TARGETING TUMORS

FIELD OF THE INVENTION

This invention relates to methods of specifically delivering an effector molecule to a tumor cell. In particular this invention relates to chimeric molecules that specifically bind to IL-13 receptors which, when combined with IL-4 receptor blockers, specifically deliver compounds or having a particular activity to tumors overexpressing IL-13 receptors.

BACKGROUND OF THE INVENTION

In a chimeric molecule, two or more molecules that exist separately in their native state are joined together to form a single entity (molecule) having the desired functionality of all of its constituent molecules. Frequently, one of the constituent molecules of a chimeric molecule is a "targeting molecule" . The targeting molecule is a molecule such as a ligand or an antibody that specifically binds to its corresponding target, for example a receptor on a cell surface. Thus, for example, where the targeting molecule is an antibody, the chimeric molecule will specifically bind (target) cells and tissues bearing the epitope to which the antibody is directed.

Another constituent of the chimeric molecule may be an "effector molecule". The effector molecule refers to a molecule that is to be specifically transported to the target to which the chimeric molecule is specifically directed. The effector molecule typically has a characteristic activity that is desired to be delivered to the target cell. Effector molecules include cytotoxins, labels, radionuclides, other ligands, antibodies, drugs, prodrugs, liposomes, and the like.

In particular, where the effector component is a cytotoxin, the chimeric molecule may act as a potent cell-killing agent specifically targeting the cytotoxin to cells bearing a particular target molecule. For example, chimeric fusion proteins which include interleukin 4 (IL-4) or transforming growth factor (TGFα) fused to Pseudomonas

exotoxin (PE) or interleukin 2 (IL-2) fused to Diphtheria toxin (DT) have been shown to specifically target and kill cancer cells (Pastan et al. , Ann. Rev. Biochem. , 61. 331-354 (1992)).

Generally, it is desirable to increase specificity and affinity and decrease cross-reactivity of chimeric cytotoxins with targets to be spared in order to increase their efficacy. To the extent a chimeric molecule preferentially selects and binds to its target (e.g. a tumor cell) and not to a non-target (e.g. a healthy cell), side effects of the chimeric molecule will be minimized. Unfortunately, many targets to which chimeπc cytotoxins have been directed (e.g. the IL-2 receptor), while showing elevated expression on tumor cells, are also expressed to some extent, and often at significant levels, on healthy cells. Thus, chimeπc cytotoxins directed to these targets frequently show adverse side-effects as they bind non-target (e.g. , healthy) cells that also express the targeted receptor.

SUMMARY OF THE INVENTION

The present invention provides methods and compositions for specifically delivering an effector molecule to a tumor cell. In particular, the present invention provides methods and compositions for specifically targeting target tumor cells while offeπng reduced targeting of healthy cells than previously known methods and compositions.

The improved specific targeting of this invention is premised, in part, on two discoveries: The first discovery was that tumor cells, especially carcinomas such as renal cell carcinoma, Kaposi's sarcoma, and brain tumors such as ghomas and medulloblastomas overexpress IL-13 receptors at extremely high levels. The second discovery was that despite the fact that the IL-4 and IL- 13 appear to share a common receptor on healthy cells, the receptors are "decoupled" in cancerous cells so that blocking of the IL-4 receptor confers protection of healthy cells without inhibiting the activity of IL-13 receptor directed molecules on cancerous cells This permits IL- 13 receptor-directed chimeric molecules (e.g. , IL- 13R-cytotoxιns) to be administered at higher dosages with fewer adverse side-effects (e.g. , IL-13R-cytotoxιns administered with an IL-4R blocker will have a higher LD ₅₀ ). In addition, reduction and elimination

of any binding between an IL-13R directed chimera and IL-4 receptors will leave greater concentrations of the chimera free in the circulation to bind to IL- 13 receptors. These features (among others) coupled with the extremely high level of IL-13 receptor expression on target tumor cells permits the specific delivery of relatively high concentrations of IL-13R-directed chimerics to their IL-13R-bearing target cells.

Thus, in one embodiment, this invention provides a method of specifically delivering an effector molecule to a tumor cell bearing an IL- 13 receptor (preferably an IL-13 receptor that is not shared with IL-4). The method involves the steps of: providing a chimeric molecule comprising an effector molecule attached to a targeting molecule that specifically binds to an IL-13 receptor; and contacting the tumor cell with the chimeric molecule in the presence of a blocker of an interleukin-4 receptor (IL-4R) The blocker is preferably present in a concentration sufficient to block binding of the targeting molecule to the IL-4 receptor. The chimeric molecule thus specifically binds to the tumor cell. In a preferred embodiment, particularly where the blocker is a molecule that also occurs endogenously (e.g. , IL-4) the blocker is present in a concentration greater than that found in the environment in which the tumor cells and/or healthy (non-tumerous) cells normally occur. Preferred blockers include, but are not limited to an interleukin-4, an interleukin-4 antagonist, and an interleukιn-4 receptor binding antibody (anti-IL-4R Ab). Interleukin-4 antogonists are selected whose antagonistic activity is mediated by binding to the IL-4 receptor not to IL-4 itself thus, they act as IL-4 competitors or competitive antagonists. Particularly preferred blockers specifically bind to the 140 kDa subunit of the IL-4 receptor. Preferred blockers include interleukin antagonists such as an interleukin-4 having a mutation in α-helix D with more preferred blockers including [Y124D]hIL4 and[R121D, Y124D]hIL4. In preferred chimeric molecules, the targeting molecule is either a hgand, such as IL-13 or an anti-IL-13 receptor antibody. The targeting molecule may be chemically conjugated to the effector molecule, or where both targeting and effector molecules are polypeptides, the targeting molecule may be joined to the effector molecule through one or more peptide bonds thereby forming a fusion protein Suitable effector molecules include a cytotoxin, a label, a radionuclide, a drug, a prodrug, a liposome, a ligand, and an antibody. In a particularly preferred embodiment, the

effector is a cytotoxin, (e.g. , Pseudomonas exotoxin, Diphtheπa toxin, πcin, abπn, or a cytotoxic prodrug) with Pseudomonas exotoxin or Diptheπa toxin (especially truncated forms in which the native binding domain is eliminated) being more preferred and Pseudomonas exotoxin (e.g , PE38QQR, PE4E, ere.) being most preferred. Where the Pseudomonas exotoxin is fused to an IL-13 targeting molecule, preferred fusion proteins include, but are not limited to IL- 13-PE38QQR, IL- 13-PE4E, cpIL- 13-PE38QQR, and cpIL-13-PE4E.

As indicated above, the chimeric molecule is preferably contacted with the tumor cell in the presence of an IL-4 receptor (IL-4R) blocker Preferred IL-13R-directed chimera/blocker combinations include, but are not limited to IL- 13- PE38QQR or IL-13-PE4E and [Y124D]hIL4 or [R121 D, Y 124D]hIL4

Preferred targets for the methods ot this invention include cells, tissues, or organs that express, more preferably overexpress IL- 13 receptors Particularly preferred targets are tumor cells that overexpress IL- 13 receptors. Such tumor cells include, but are not limited to renal cell carcinoma cells, brain tumor cells (e.g. , ghoma cells, medulloblastoma cells, etc.), and Kaposi's sarcoma cells.

In another embodiment, this invention provides a method of impairing growth of tumor cells bearing an IL-13 receptor. The method involves contacting the tumor cell with a chimeric molecule comprising a targeting molecule that specifically binds a human IL-13 receptor; and an effector molecule selected from the group consisting of a cytotoxin, a radionuchde, a ligand, an antibody, and a cytotoxic prodrug The contacting is in the presence of a blocker of an interleukin receptor (IL-4R) The blocker is preferably present in a concentration sufficient to block binding of the targeting molecule to the IL-4 receptor The chimeric molecule thus specifically binds to the tumor cell. In a preferred embodiment, particularly where the blocker is a molecule that also occurs endogenously (e.g. , IL-4) the blocker is present in a concentration greater than that found in the environment in which the tumor cells and/or healthy (non-tumerous) cells normally occur. Any of the IL-4R blockers described herein are suitable. Any of the targeting molecules described herein are suitable targeting molecules in the chimeric molecule and any ot the cytotoxic molecules descnbed herein are suitable effector molecules Preterred IL- 13R-dιrected

chimera/blocker combinations include, but are not limited to IL-13-PE38QQR or IL- 13- PE4E and [Y124D]hIL4 or [R121D, Y 124D]hIL4. Particularly preferred targets are tumor cells that overexpress IL- 13 receptors. Such tumor cells include, but are not limited to renal cell carcinoma cells, brain tumor cells (e.g. , glio a cells, meduUoblastoma cells, etc.), and Kaposi's sarcoma cells. The tumor cell growth that is inhibited can be tumor cell growth in a human. The contacting step may comprise administering the chimeric molecule to a human intravenously, into a body cavity, or into a lumen or an organ.

In still another embodiment, this invention provides a method of detecting the presence, absence, size, or number of tumor cells. The method involves contacting the tumor cell(s) with a chimeric molecule comprising a targeting molecule that specifically binds a human IL-13 receptor; and a detectable label, and detecting the presence, absence, or quantity of the detectable label. The contacting is in the presence of a blocker of an interleukin receptor (IL-4R) and the blocker is present in a concentration sufficient to block binding of the targeting molecule to an IL-4 receptor. In a preferred embodiment, particularly where the blocker is a molecule that also occurs endogenously (e.g. , IL-4) the blocker is present in a concentration greater than that found in the environment in which the tumor cells and/or healthy (non-tumerous) cells normally occur. Suitable blockers and targeting molecules include any of the blockers and targeting described herein. Detectable labels include, but are not limited to those discussed herein.

In still yet another embodiment, this invention provides a pharmacological composition. The composition includes a pharmaceutically acceptable carrier, a chimeric molecule comprising an effector molecule attached to a targeting molecule that specifically binds to an IL-13 receptor, and a blocker of an interleukin receptor (IL-4R). Any of the chimeric molecules, more preferably the cytotoxic chimeras and chimeras in which the effector is a detectable label, and most preferably the cytotoxic chimeras, described herein are suitable. The blocker can include, but is not limited to, any of the blockers described herein.

Definitions

The term "specifically deliver" as used herein refers to the preferential association of a molecule with a cell or tissue bearing a particular target molecule or marker and not to cells or tissues lacking that target molecule or expressing that target molecule at low levels. It is, of course, recognized that a certain degree of non-specific interaction may occur between a molecule and a non-target cell or tissue. Nevertheless. specific delivery, may be distinguished as mediated through specific recognition of the target molecule. Typically specific delivery results in a much stronger association between the delivered molecule and cells bearing the target molecule than between the delivered molecule and cells lacking the target molecule. Specific delivery typically results in greater than 2 fold, preferably greater than 5 fold, more preferably greater than 10 fold and most preferably greater than 100 fold increase in amount of delivered molecule (per unit time) to a cell or tissue bearing the target molecule as compared to a cell or tissue lacking the target molecule or marker. The term "blocker" when used with reference to an IL-4 receptor refers to a substance that specifically binds to an IL-4 receptor, or component thereof, and reduces or prevents binding of that receptor by another different substance (e.g. , an IL-13 based chimeric molecule). Because the blocker competes with the native ligand (IL-4) for the IL-4 receptor it is also referred to as an IL-4 competitor. Moreover, since most preferred blockers do not activate the IL-4 receptor, the preferred blocker is an "IL-4 antagonist" or a "competitive antagonist" of IL-4. One of skill in the art will appreciate that a blocker, to be effective, need not eliminate all binding to the "blocked" receptor but rather a simple reduction in binding of other molecules to the subject receptor is sufficient. The effect of such blocking is to make the receptor, on average. generally less available for binding to moieties other than the blocking agent.

The term "residue" as used herein refers to an amino acid that is incorporated into a polypeptide. The amino acid may be a naturally occurring amino acid and, unless otherwise limited, may encompass known analogs of natural amino acids that can function in a similar manner as naturally occurring amino acids. A "fusion protein" refers to a polypeptide formed by the joining of two or more polypeptides through a peptide bond formed between the amino terminus of one

polypeptide and the carboxyl terminus of another polypeptide. The fusion protein may be formed by the chemical coupling of the constituent polypeptides or it may be expressed as a single polypeptide from nucleic acid sequence encoding the single contiguous fusion protein. A single chain fusion protein is a fusion protein having a single contiguous polypeptide backbone.

A "spacer" as used herein refers to a peptide that joins the proteins comprising a fusion protein. Generally a spacer has no specific biological activity other than to join the proteins or to preserve some minimum distance or other spatial relationship between them. However, the constituent amino acids of a spacer may be selected to influence some property of the molecule such as the folding, net charge, or hydrophobicity of the molecule. A spacer can also be an organic (non-peptide) molecule that serves the same purpose as the peptide spacer.

A "ligand", as used herein, refers generally to all molecules capable of reacting with or otherwise recognizing or binding to a receptor on a target cell. Specifically, examples of ligands include, but are not limited to, antibodies, lymphokines, cytokines, receptor proteins such as CD4 and CD8, solubilized receptor proteins such as soluble CD4, hormones, growth factors, and the like which specifically bind desired target cells.

The term "cpIL-13" is used to designate a circularly permuted (cp) IL- 13. Circular permutation is functionally equivalent to taking a straight-chain molecule, fusing the ends (directly or through a linker) to form a circular molecule, and then cutting the circular molecule at a different location to form a new straight chain molecule having different termini.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the cytotoxic activity of hIL13-PE38QQR on established glioma cell lines and human glioma (G2) explant cells and failure to inhibit this cytotoxicity by hIL4. hIL4 was added at a concentration of 1.0 μg/ml. Three different batches of rhIL-4 showed the same effect. The dashed line shows 50% of the difference between the background and control MTS conversion that was recorded at A ₄ , ₀ nm.

Figure 2 shows the cytotoxicity of hIL-4-PE38QQR on glioma cells and blocking of this cytotoxicity by hIL- 13. Human IL- 13 was added at a concentration of 1.0 μg/ml. The dashed line shows 50% of the difference between the background and control MTS conversion that was recorded at A ₄₉₀ nm. Figure 3 shows the cytotoxicity of hIL-4-PE4E on glioma cells and blocking of this cytotoxicity by hIL- 13. Human IL- 13 was added at a concentration of 1.0 μg/ml. The dashed line shows 50% of the difference between the background and control MTS conversion that was recorded at A ₄₉₀ nm.

Figure 4 shows that hIL-13 and hIL-4 do not inhibit proliferation of the U-373 MG and human glioma G2 explant cells. Data represent, in most cases, the average of quadruplicates. The dashed line shows 50% of the difference between the background and control MTS conversion that was recorded at A ₄₉₀ nm.

Figures 5A and 5B illustrate a competitive binding assay on A- 172 glioblastoma cells. Data are expressed as a percentage of total ^{l 5} I-hIL- 13 binding to cells (Figure 5 A) and as a Scatchard plot (Figure 5B). The points are the average of two determinations. Similar data were obtained on three other established glioma cell lines.

Figures 6A and 6B illustrate a competitive binding assay on human glioma G2 explant cells. Data are expressed as a percentage of total ^l25 I-hIL- 13 binding to ceils (Figure 6A) and as a Scatchard plot (Figure 6B). The points are the average of two determinations. Similar data were obtained on three other established glioma cell lines.

Figures 7A and 7B show cross-competition between hIL- 13 and hIL-4 for the binding sites of labeled interleukins on glioma cells. A- 172 glioblastoma cells ( 1 x 10 ⁶ ) were incubated with 200 pM ¹²⁵ I-hIL- 13 (Figure 7A) or ^I25 I-hIL-4 (Figure 7B) with or without increasing concentrations (up to 100 nM) of unlabeled hIL- 13 or hIL-4. Bound radioactivity was determined as described in Example 13. Data are presented as a mean of % total binding of cells incubated with radiolabeled interleukins only, total of 125hIL-13 bound to A- 172 cells was 8699 ± 1 1 (cp ±SD) and total bound ^l25 I-hIL-4 was 5789± 185 (cpm±SD). The experiments were performed in duplicates. Bars, SD shown when larger than symbol. Figure 8 shows competition of hIL- 13 for the binding sites of labeled hlL-

4 on CTLL-2 cells transfected with the human 140 kDa IL-4 receptor (CTLL-2 ^hlUR ) .

CTLL-2 ^{ωL R} cells were incubated with 200 mP of ^l2S I-hIL-4 with or without excess hlL- 13 or hIL-4. The results are expressed as % of total binding. Total ^l25 I-hIL-4 bound to cells was 4412 ± 344 (cpm±SD). The experiments were done in duplicates and bars represent SD when larger than symbols. DETAILED DESCRIPTION

I. Chimeric Molecules Targeted to the IL-13 Receptor.

This invention provides compositions and methods tor specifically delivenng an effector molecule to a tumor cell. This method involves the use of chimeπc molecules in combination with a blocking agent to specifically target the tumor cells while sparing normal (healthy) cells. The chimeric molecule comprises a targeting molecule attached to an effector molecule. In a particularly preferred embodiment, the targeting molecule specifically recognizes and binds to the IL- 13 receptor, while the blocking agent (blocker) specifically recognizes and binds to the IL-4 receptor

The improved specific targeting of this invention is premised, in part, on two discoveries: The first discovery was that tumors including, but not limited to, renal cell carcinomas (RCCs), Kaposi's sarcoma (KS), and brain tumors, overexpress IL- 13 receptors at extremely high levels. While the IL-13 receptors (IL- 13R) are overexpressed on tumor cells, expression of these receptors on other cells (e.g monocytes, B cells, and T cells) appears negligible Thus, by specifically targeting the IL-13 receptor, the present invention provides chimeπc molecules that are specifically directed to solid tumors while minimizing targeting ol other cells or tissues.

The second discovery was that, although IL-4 and IL- 13 appear to share a common receptors in healthy cells (part of which is the 140 kDa subunit described herein), transformed cells express an IL-13 receptor that is not shared with IL-4; that is, it does not involve the 140 kDa subunit Administration of an IL-4 receptor blocker in conjunction with an IL-13 receptor directed chimeric molecule will block binding of that molecule to normal cells bearing IL-4 receptors and/or the shared (140 kDa subunit) without inhibiting binding of the molecule to cancer cells.

Thus, in a preferred embodiment, this invention provides a method of specifically delivering an effector molecule to a tumor cell bearing an IL- 13 receptor The method involves the steps of providing a chimeπc molecule comprising an effector

molecule attached to a targeting molecule that specifically binds to an IL- 13 receptor, and contacting the tumor cell with the chimeric molecule in the presence of a blocker of an interleukin receptor (IL-4R). The blocker is preferably provided in a concentration sufficient to block binding of the targeting molecule to an IL-4 receptor. The effector component of the chimeric molecule can be any of a wide number of effectors well known to those of skill in the art. These include, but are not limited to a cytotoxin a label, a radionuclide, a drug, a prodrug, a prodrug conversion enzyme, a liposome, a ligand, an antisense molecule, an expression cassette, and an antibody. In one particularly preferred embodiment, the effector is a cytotoxin and the method provides a means to impair the growth of tumor cells (or tumors). The cytotoxin may be a native or modified cytotoxin such as Pseudomonas exotoxin (PE), Diphtheria toxin (DT), πcin, abπn, pokeweed antiviral protein, and the like.

The chimeric cytotoxin is administered to an organism containing tumor cells either in conjunction with or after administration of an IL-4 receptor blocker. The blocker prevents the chimeric toxin from binding to IL-4 receptors which are numerous on healthy cells leaving the chimeric cytotoxin free to contact IL- 13 receptor expressing tumor cells. The targeting molecule component of the chimeric molecule specifically binds to the overexpressed IL-13 receptors on the tumor cells. Once bound to the IL-13 receptor on the cell surface, the cytotoxic effector molecule mediates internalization into the cell where the cytotoxin inhibits cellular growth or kills the cell Alternatively, the "cytotoxin" modifies the cell so that it is more susceptible to cytotoxic agents (e g. , radiotherapy or chemotherapy).

The use of chimeric molecules comprising a targeting moiety joined to a cytotoxic effector molecules to target and kill tumor cells is known in the prior art. For example, chimeric fusion proteins which include interleukin 4 (IL-4) or transforming growth factor (TGFα) fused to Pseudomonas exotoxin (PE) or interleukin 2 (IL-2) fused to Diphtheπa toxin (DT) have been tested for their ability to specifically target and kill cancer cells (Pastan et al. , Ann. Rev. Bioche . , 61 ' 331-354 ( 1992))

Although the use of cytotoxic chimeπc molecules is known in the prior art, it is believed the use of an IL-4 receptor blocker in conjunction with a cytotoxin has never been described. Chimeric IL-4-cytotoxιn molecules are known in the prior art.

and IL-4 shows some sequence similarity to IL- 13. Moreover, the IL-4 and IL- 13 receptors share a component and are reciprocally inhibited by their native ligands in normal cells. Thus, it was an unexpected discovery of this invention that tumor cells express an IL-13 receptor that is apparently decoupled from the IL-4 receptor and that this IL-13 receptor is consequently not blocked by IL-4 or other agents that bind to the

IL-4 receptor (e.g. ,[Y124D]hIL4).

In addition, it was also a surprising discovery of this invention that cytotoxins targeted by a moiety specific to the IL-13 receptor show significantly increased efficacy as compared to IL-4 receptor directed cytotoxins. Without being bound to a particular theory, it is believed that the improved efficacy of the IL- 13 chimeras of the present invention is due to at least three factors.

First, IL- 13 receptors are expressed at much lower levels, if at all on non- tumor cells (e.g. monocytes, T cells, B cells). Thus cytotoxins directed to IL- 13 receptors show reduced binding and subsequent killing of healthy cells and tissues as compared to other cytotoxins.

Second, the receptor component that specifically binds IL-13 appears to be expressed at significantly higher levels on solid tumors than the receptor component that binds IL-4. Thus, tumor cells bind higher levels of cytotoxic chimeπc molecules directed against IL-13 receptors than cytotoxic chimeπc molecules directed against IL-4 receptors.

Finally, IL-4 receptors are up-regulated when immune system cells (e.g T-cells) are activated. This results in healthy cells, for example T-cells and B-cells, showing greater susceptibility to IL-4 receptor directed cytotoxins. Thus, the induction of an immune response (as against a cancer), results in greater susceptibility of cells of the immune system to the therapeutic agent. In contrast, IL-13 receptors have not been shown to be up-regulated in activated T cells. Thus IL-13 receptor targeted cytotoxins have no greater effect on activated T cells and thereby minimize adverse effects of the therapeutic composition on cells of the immune system. Moreover, even when the immune system is upregulated, the ability to specifically block immune cells using IL-4 receptor blockers in conjunction with the IL-13 receptor directed chimeric toxins results in even greater efficacy of these toxins with greater sparing of normal (healthy) cells.

In another embodiment, this invention also provides for compositions and methods for detecting the presence or absence of tumor cells. These methods involve providing a chimeric molecule comprising an effector molecule, that is a detectable label attached to a targeting molecule that specifically binds an IL-13 receptor. The chimeric molecule is contacted to the tumor cells in the presence of an IL-4 receptor blocker. The blocker reduces or eliminates binding of the chimeric molecule to IL-4 receptors leaving the IL-13 receptor targeting moiety free to specifically bind the chimeric molecule to tumor cells which are then marked by their association with the detectable label. Subsequent detection of the cell-associated label indicates the presence of a tumor cell. In yet another embodiment, the effector molecule may be another specific binding moiety such as an antibody, a growth factor, or a ligand. The chimeric molecule, especially in the presence of an IL-4 receptor blocker, will then act as a highly specific bifunctional linker. This linker may act to bind and enhance the interaction between cells or cellular components to which the fusion protein binds. Thus, for example, where the "targeting" component of the chimeric molecule comprises a polypeptide that specifically binds to an IL- 13 receptor and the "effector" component is an antibody or antibody fragment (e.g. an Fv fragment of an antibody), the targeting component specifically binds cancer cells, while the effector component binds receptors (e.g. , IL-2 receptors) on the surface of immune cells. The chimeric molecule may thus act to enhance and direct an immune response toward target cancer cells.

In still yet another embodiment the effector molecule may be a pharmacological agent (e.g. a drug or a prodrug) or a vehicle containing a pharmacological agent. This is particularly suitable where it is merely desired to invoke a non-lethal biological response. Thus the moiety that specifically binds to an IL- 13 receptor may be conjugated to a drug such as vinblastine, doxorubicin or its derivatives, genistein (a tyrosine kinase inhibitor), an antisense molecule, and other pharmacological agents known to those of skill in the art, thereby specifically targeting the pharmacological agent to tumor cells overexpressing IL- 13 receptors.

Alternatively, the targeting molecule may be bound to a vehicle containing the therapeutic composition. Such vehicles include, but are not limited to liposomes, micelles, various synthetic beads, and the like.

One of skill in the art will appreciate that the chimeπc molecules of the present invention may include multiple targeting moieties bound to a single effector or conversely, multiple effector molecules bound to a single targeting moiety. In still other embodiment, the chimeric molecules may include both multiple targeting moieties and multiple effector molecules. Thus, for example, this invention provides for "dual targeted" cytotoxic chimeric molecules in which targeting molecule that specifically binds to IL-13 is attached to a cytotoxic molecule and another molecule (e.g. an antibody, or another ligand) is attached to the other terminus of the toxin. Such a dual- targeted cytotoxin might comprise an IL- 13 substituted for domain la at the ammo terminus of a PE and antι-TAC(Fv) inserted in domain III, between amino acid 604 and 609. Other antibodies may also be suitable.

π. The Targeting Molecule.

In a preferred embodiment, the targeting molecule is a molecule that specifically binds to the IL- 13 receptor. The term "specifically binds" , as used herein, when referring to a protein or polypeptide, refers to a binding reaction which is determinative of the presence of the protein or polypeptide in a heterogeneous population of proteins and other biologies Thus, under designated conditions (e g immunoassay conditions in the case of an antibody), the specified ligand or antibody binds to its particular "target" protein (e.g. an IL-13 receptor protem) and does not bind in a significant amount to other proteins present in the sample or to other proteins to which the ligand or antibody may come in contact in an organism

A variety of immunoassay formats may be used to select antibodies specifically immunoreactive with an IL- 13 receptor protein For example, solid-phase ELISA immunoassays are routinely used to select monoclonal antibodies specifically immunoreactive with a protein See Harlow and Lane (1988) Antibodies, A Laboratory Manual, Cold Spring Harbor Publications, New York, for a description of immunoassay formats and conditions that can be used to determine specific immunoreactivity

Similarly, assay formats for detecting specific binding of hgands (e g IL- 13, cpIL-13) with their respective receptors are also well known in the art. Example 1

provides a detailed protocol for assessing specific binding of labeled IL- 13 by an IL- 13 receptor.

The IL-13 receptor is a cell surface receptor that specifically binds IL- 13 and mediates a variety of physiological responses in various cell types as described below in the description of IL- 13. The IL- 13 receptor may be identified by contacting a cell or other sample with labeled IL-13 and detecting the amount of specific binding of IL-13 according to methods well known to those of skill in the art. Detection of IL-13 receptors by labeled IL-13 binding is described in detail in Example 1.

Alternatively, an anti-IL-13 receptor antibody may also be used to identify IL-13 receptors. The antibody will specifically bind to the IL- 13 receptor and this binding may be detected either through detection of a conjugated label or through detection of a labeled second antibody that binds the antι-IL- 13 receptor antibody.

In a preferred embodiment, the moiety utilized to specifically target the IL-13 receptor is either an antibody that specifically binds the IL- 13 receptor (an anti-IL-13R antibody) or a ligand, such as IL-13 or cpIL- 13, that specifically binds to the receptor. Such ligands may include other molecules selected, for example from peptide libraries, or IL- 13 mimetics designed to bind the IL- 13 receptor.

A) IL-13. Interleukin- 13 (IL-13) is a pleiotropic cytokine that is recognized to share many of the properties of IL-4. IL- 13 has approximately 30% sequence identity with IL-4 and exhibits IL-4-like activities on monocytes/macrophages and human B cells (Minty et al. , Nature, 362: 248 (1993), McKenzie et al. Proc. Natl. Acad. Set. USA . 90: 3735 (1987)). In particular, IL- 13 appears to be a potent regulator of inflammator\ and immune responses. Like IL-4, IL- 13 can up-regulate the monocyte/macrophage expression of CD23 and MHC class I and class II antigens, down-regulate the expression of Fcγ, and inhibit antibody-dependent cytotoxicity. IL- 13 can also inhibit nitric oxide production as well as the expression of pro-inflammatory cytokines (e.g. IL- 1 , IL-6, IL- 8, IL-10 and IL-12) and chemokines (MIP-1 , MCP), but enhance the production of IL- 1 (Minty supra. ; McKenzie et al. , supra. ; Zurawski et al. Immunol. Today, 15: 19

(1994); de Waal Malefyt er al. J. Immunol. , 150: 180A ( 1993); de Waal Malefyt er al

J. Immunol. , 151 : 6370 (1993); Doherty er al. J. Immunol. , 151 : 7151 (1993); and Minty et al. Eur. Cytokine Nerw. , 4: 99 (1993)).

Recombinant IL-13 is commercially available from a number of sources (see, e.g. R & D Systems, Minneapolis, Minnesota, USA, and Sanofi Bio-Industries, Inc., Tervose, Pennsylvania, USA). Alternatively, a gene or a cDNA encoding IL- 13 may be cloned into a plasmid or other expression vector and expressed in any of a number of expression systems according to methods well known to those of skill in the art. Methods of cloning and expressing IL- 13 and the nucleic acid sequence for IL- 13 are well known (see, for example, Minty et al. (1993) supra, and McKenzie ( 1993), supra). In addition, the expression of IL-13 as a component of a chimeric molecule is detailed in Example 4.

One of skill in the art will appreciate that analogues or fragments of IL- 13 bearing will also specifically bind to the IL- 13 receptor. For example, conservative substitutions of residues (e.g. , a seπne for an alanine or an aspartic acid for a glutamic acid) comprising native IL-13 will provide IL- 13 analogues that also specifically bind to the IL-13 receptor. Thus, the term "IL-13", when used in reference to a targeting molecule, also includes fragments, analogues or peptide mimetics of IL-13 that also specifically bind to the IL-13 receptor.

Bi- Anti-II _^ l.l receptor antibodies. i) The antibodies.

One of skill will recognize that other molecules besides IL- 13 will specifically bind to IL-13 receptors. Polyclonal and monoclonal antibodies directed against IL-13 receptors provide particularly suitable targeting molecules in the chimeric molecules of this invention. The term "antibody" , as used herein, includes various forms of modified or altered antibodies, such as an intact immunoglobulin, various fragments such as an Fv fragment, an Fv fragment containing only the light and heavy chain variable regions, an Fv fragment linked by a disulfide bond (Bπnkmann, et al Proc. Natl. Acad. Sci. USA, 90: 547-551 (1993)), an Fab or (Fab) ', fragment containing the variable regions and parts of the constant regions (see, e.g. , Debmski et al. , Clm Cancer. Res. , 1 : 1015- 1022 (1995), a single-chain antibody and the like (Bird et a!. ,

Science 242: 424-426 ( 1988); Huston et al , Proc. Nat. Acad. Sci. USA 85: 5879-5883 (1988)). The antibody may be of animal (especially mouse or rat) or human origin or may be chimeric (Morrison et al. , Proc Nat. Acad. Sci. USA 81 : 6851-6855 ( 1984)) or humanized (Jones et al , Nature 321 : 522-525 ( 1986), and published UK patent application #8707252). Methods of producing antibodies suitable for use in the present invention are well known to those skilled in the art and can be found described in such publications as Harlow & Lane, Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory (1988), and Asai, Methods in Cell Biology Vol. 37: Antibodies in Cell Biology, Academic Press, Inc. N.Y. (1993). Antibodies that specifically bind the IL- 13 receptor may be produced by a number of means well known to those of skill in the art. Generally, this involves using an antigenic component of the IL- 13 receptor as an antigen to induce the production of antibodies in an organism (e.g. a sheep, mouse, rabbit, etc. ). One of skill in the art will recognize that there are numerous methods of isolating all or components of the IL- 13 receptor for use as an antigen. For example, IL- 13 receptors may be isolated by cross- linking the receptor to a labeled IL- 13 by the exposure to 2 mM disuccinimidyl suberate (DSS). The labeled receptor may then be isolated according to routine methods and the isolated receptor may be used as an antigen to raise anti-IL- 13 receptor antibodies as described below. Cross-linking and isolation of components of the IL- 13 receptor is described in Example 3.

In a preferred embodiment, however, IL- 13 receptors may be isolated by means of affinity chromatography. It was a surprising discovery of the present invention that solid tumor cells overexpress IL- 13 receptors. This discovery of cells overexpressing IL-13 receptor greatly simplifies the receptor isolation. Generally, approximately, 100 million renal carcinoma cells, may be solubilized in detergent with protease inhibitors according to standard methods. The resulting lysate is then run through an affinity column bearing IL-13. The receptor binds to the IL-13 in the column thereby effecting an isolation from the lysate. The column is then eluted with a low pH buffer to dissociate the IL-13 ligand from the IL- 13 receptor resulting in isolated receptor. The isolated receptor may then be used as an antigen to raise anti-IL- 13 receptor antibodies.

in AntihoHy production.

Methods of producing polyclonal antibodies are known to those of skill in the art. In brief, an immunogen, preferably an isolated IL-13 receptor or receptor epitope is mixed with an adjuvant and animals are immunized with the mixture. The animal's immune response to the immunogen preparation is monitored by taking test bleeds and determining the titer of reactivity to the polypeptide of interest. When appropriately high titers of antibody to the immunogen are obtained, blood is collected from the animal and antisera are prepared. Further tractionation of the antisera to enrich for antibodies reactive to the polypeptide is performed where desired. See, e.g. ,

Coligan (1991) Current Protocols in Immunology Wiley/Greene, NY; and Harlow and Lane (1989) Antibodies: A Laboratory Manual Cold Spring Harbor Press, NY).

Monoclonal antibodies may be obtained by various techniques familiar to those skilled in the art. Description of techniques for preparing such monoclonal antibodies may be found in, e.g. , Stites et al (eds.) Basic and Clinical Immunology (4th ed.) Lange Medical Publications, Los Altos, CA, and references cited therein; Harlow and Lane (1988) Antibodies: A Laboratory Manual CSH Press; Goding ( 1986) Monoclonal Antibodies: Principles and Practice (2d ed.) Academic Press, New York, NY; and particularly in Kohler and Milstein (1975) Nature 256: 495-497, which discusses one method of generating monoclonal antibodies.

Summarized briefly, this method involves injecting an animal with an immunogen. The animal is then sacrificed and cells taken from its spleen, which are then fused with myeloma cells (See, Kohler and Milstein (1976) Eur. J. Immunol 6: 511-519). The result is a hybrid cell or "hybridoma" that is capable of proliferation in vitro, and producing antibodies against the "given" immunogen.

Colonies arising from single immortalized cells are screened for production of antibodies of the desired specificity and affinity for the antigen, and yield of the monoclonal antibodies produced by such cells is enhanced by various techniques, including injection into the peritoneal cavity of a vertebrate host. Alternatively, one may isolate DNA sequences which encode a monoclonal antibody or a binding fragment thereof by screening a DNA library from human B cells according to the general

protocol outlined by Huse et al. ( 1989) Science 246: 1275- 1281. In this manner, the individual antibody species obtained are the products of immortalized and cloned single B cells from the immune animal generated in response to a specific site recognized on the immunogenic substance. Other suitable techniques involve selection of libraries of antibodies in phage or similar vectors. See, Huse et al Science 246: 1275-1281 ( 1989); and Ward, et al. Nature 341: 544-546 (1989). In general suitable monoclonal antibodies will usually bind their target epitope with at least a K _D of about 1 mM, more usually at least about 300 μM, and most preferably at least about 0.1 μM or better. One of skill will appreciate that the IL-13R targeting antibodies and the

IL-4R blocking antibodies of this invention can also include humanized (chimeric) or human antibodies. ϊ) Hπmani7ed ichimerie) antibodies. Humanized (chimeric) antibodies are immunoglobulin molecules comprising a human and non-human portion. More specifically, the antigen combining region (or variable region) of a humanized chimeπc antibody is derived from a non-human source (e.g. , murine) and the constant region of the chimeπc antibody (which confers biological effector function to the immunoglobuhn) is derived from a human source. The humanized chimeric antibody should have the antigen binding (e. t; , anti-IL-4R or anti-IL-13R) specificity of the non-human antibody molecuie and the effector function conferred by the human antibody molecule. A large number of methods of generating chimeric antibodies are well known to those of skill in the art (see, e.g. , U.S. Patent Nos: 5,502, 167, 5,500,362, 5,491 ,088, 5,482,856, 5,472,693, 5 ,354,847, 5,292,867, 5,231 ,026, 5,204,244, 5,202,238, 5, 169,939, 5,081 ,235, 5,075,431 , and 4,975,369).

In general, the procedures used to produce these chimeπc antibodies consist of the following steps (the order of some steps may be interchanged): (a) identifying and cloning the correct gene segment encoding the antigen binding portion of the antibods molecule; this gene segment (known as the VDJ, variable, diversity and joining regions for heavy chains or VJ, variable, joining regions for light chains (or simply as the V or

Variable region) may be in either the cDNA or genomic form; (b) cloning the gene segments encoding the constant region or desired part thereof; (c) ligating the variable region with the constant region so that the complete chimeric antibody is encoded in a transcribable and translatable form; (d) ligating this construct into a vector containing a selectable marker and gene control regions such as promoters, enhancers and poly(A) addition signals; (e) amplifying this construct in a host cell (e.g., bacteria); (f) introducing the DNA into eukaryotic cells (transfection) most often mammalian lymphocytes;

Antibodies of several distinct antigen binding specificities have been manipulated by these protocols to produce chimeric proteins (e.g., anti-TNP: Boulianne et al. (1984) Nature, 312: 643; and anti-tumor antigens: Sahagan et al (1986) J. Immunol, 137: 1066). Likewise several different effector functions have been achieved by linking new sequences to those encoding the antigen binding region. Some of these include enzymes (Neuberger et al (1984) Nature 312: 604), immunoglobulin constant regions from another species and constant regions of another immunoglobulin chain

(Sharon et al (1984) Nature 309: 364; Tan et al, (1985) J. Immunol. 135: 3565-3567). Detailed methods for preparation of chimeric (humanized) antibodies can be found in U.S. Patent 5,482,856.

hi Human antibodies.

In another embodiment, this invention provides for fully human anti-IL- 4R antibodies. Human antibodies consist entirely of characteristically human polypeptide sequences. The human antibodies (e.g., anti-IL-4R) used in this invention can be produced in using a wide variety of methods (see, e.g. , Larrick et al , U.S. Pat. No. 5,001 ,065, for review).

In one preferred embodiment, the human antibodies of the present invention are usually produced initially in trioma cells. Genes encoding the antibodies are then cloned and expressed in other cells, particularly, nonhuman mammalian cells.

The general approach for producing human antibodies by trioma technology has been described by Ostberg et al. (1983), Hybridoma 2: 361-367,

Ostberg, U.S. Pat.No. 4,634,664, and Engelman et al , U.S. Pat. No. 4,634,666. The

antibody-producing cell lines obtained by this method are called tπomas because they are descended from three cells; two human and one mouse. Tπomas have been found to produce antibody more stably than ordinary hybπdo as made from human cells. In another approach, mouse-human hybπdomas which produces human anti-IL4R antibodies are prepared (see, e.g. , U.S. Patent No: 5,506, 132). Other approaches include immunization of muπnes transformed to express human immunoglobulin genes, and phage display screening (Vaughan et al. supra. ).

C) Circularly permuted IL-13. In another embodiment, the targeting moiety can be a circularly permuted

IL-13 (cpIL- 13). Circular permutation is functionally equivalent to taking a straight- chain molecule, fusing the ends (directly or through a linker) to form a circular molecule, and then cutting the circular molecule at a different location to form a new straight chain molecule with different termini (see, e.g. , Goldenberg, et al J. Mol Biol , 165: 407-413 ( 1983) and Pan et al Gene 125: 1 1 1- 1 14 ( 1993)). Circular permutation thus has the effect of essentially preserving the sequence and identity of the amino acids of a protein while generating new termini at different locations.

Circular permutation of IL- 13 provides a means by which the native IL- 13 protein may be altered to produce new carboxyl and amino termini without diminishing the specificity and binding affinity of the altered first protein relative to its native form With new termini located away from the active (binding) site, it is possible to incorporate the circularly permuted IL-13 into a fusion protein with a reduced, or no diminution, of IL-13 binding specificity and/or avidity

It will be appreciated that while circular permutation is described in terms of linking the two ends of a protein and then cutting the circularized protein these steps are not actually required to create the end product A protein can be synthesized de novo with the sequence corresponding to a circular permutation of the native protein. Thus, the term "circularly permuted IL-13 (cpIL- 13)" refers to all IL- 13 proteins having a sequence corresponding to a circular permutation ot a native IL- 13 protein regardless of how they are constructed.

Generally, however, a permutation that retains or improves the binding specificity and/or avidity (as compared to the native IL- 13) is preferred. If the new termini interrupt a critical region of the native protein, binding specificity and avidity may be lost. Similarly, if linking the original termini destroys IL- 13 binding specificity and avidity then no circular permutation is suitable. Thus, there are two requirements for the creation of an active circularly permuted protein: 1) The termini in the native protein must be favorably located so that creation of a linkage does not destroy binding specificity and/or avidity; and 2) There must exist an "opening site" where new termini can be formed without disrupting a region critical for protein folding and desired binding activity (see, e.g. , Thorton et al J. Mol Biol , 167: 443-460 ( 1983)). This invention establishes that IL- 13 meets these criteria and provides for circularly permuted IL- 13 that having improved binding characteristics.

When circularly permuting IL- 13, it is desirable to use a linker that preserves the spacing between the termini comparable to the unpermuted or native molecule. Generally linkers are either hetero- or homo-bifunctional molecules that contain two reactive sites that may each form a covalent bond with the carboxyl and the amino terminal amino acids respectively. Suitable linkers are well known to those of skill in the art and include, but are not limited to, straight or branched-chain carbon linkers, heterocyclic carbon linkers, or peptide linkers. The most common and simple example is a peptide linker that typically consists of several amino acids joined through peptide bonds to the termini of the native protein. The linkers may be joined to the terminal amino acids through their side groups (e.g. , through a disulfide linkage to cysteine). However, in a preferred embodiment, the linkers will be joined to the alpha carbon amino and carboxyl groups of the terminal amino acids. Functional groups capable of forming covalent bonds with the amino and carboxyl terminal amino acids are well known to those of skill in the art. For example, functional groups capable of binding the terminal amino group include anhydrides, carbodimides, acid chlorides, activated esters and the like. Similarly, functional groups capable of forming covalent linkages with the terminal carboxyl include amines, alcohols, and the like. In a preferred embodiment, the linker will itself be a peptide and will be joined to the protein termini by peptide bonds. A preferred linker for the

circular permutation of IL-13 is two glycines (Gly) ₂ , followed by a seπne (Ser) followed by two glycines (Gly) .

In a preferred embodiment, circular permutation of IL- 13 involves creating an opening such that the formation of new termini does not interrupt secondary structure crucial to the formation of a structure that specifically binds the IL- 13 receptor

Even if the three-dimensional structure is compatible with joining the termini, it is conceivable that the kinetics and thermodynamics of folding would be greatly altered by circular permutation if the cleavage separates residues that participate m short range interactions that are crucial for the folding mechanism or the stability of the native state Goldenberg, Protein Eng. , 7: 493-495 ( 1989). Thus, the choice of a cleavage site can be important to the protein's binding specificity and/or avidity.

The selection of an opening site in IL- 13 may be determined by a number of factors. Preferred opening sites will be located in regions that do not show a highly regular three-dimensional structure. Thus, it is preferred that cleavage sites be selected in regions of the protein that do not show secondary structure such as alpha helices, pleated sheets, αβ barrel structures, and the like.

Methods of identifying regions of particular secondary structure of IL-13 based on amino acid sequence are widely known to those of skill in the art. See, for example, Cohen et al , Science, 263: 488-489 (1994). Numerous programs exist that predict protein folding based on sequence data. Some of the more widely known software packages include MatchMaker (Tripos Associates, St. Louis, Missouri, USA), FASMAN from GCG (Genetics Computer Group), PHD (European Molecular Biology Laboratory, Heidelburg, Germany) and the like. In addition, the amino acid sequence of IL-13 is well known and the protein has been extensively characterized (see, e.g. , WO 94/04680).

Alternatively, where the substitution of certain amino acids or the modification of the side chains of certain amino acids does not change the activity of a protein, it is expected that the modified amino acids are not critical to the protein's activity. Thus, amino acids that are either known to be susceptible to modification or axe actually modified in vivo are potentially good candidates for cleavage sites.

Where the protein is a member of a family of related proteins, one may infer that the highly conserved sequences are critical for biological activity, while the variable regions are not. Preferred cleavage sites are then selected in regions of the protein that do not show highly conserved sequence identity between various members of the protein family. Alternatively, if a cleavage site is identified in a conserved region of a protein, that same region provides a good candidate for cleavage sites in a homologous protein.

Methods of determining sequence identity are well known to those of skill in the art. Sequence comparisons between two (or more) polynucleotides or polypeptides are typically performed by comparing sequences of the two sequences over a "comparison window" to identify and compare local regions of sequence similarity Since the goal is to identify very local sequence regions that are not conserved, the comparison window will be selected to be rather small. A "comparison window" , as used herein, refers to a segment of at least about 5 contiguous positions, usually about 10 to about 50, more usually about 15 to about 40 in which a sequence may be compared to a reference sequence of the same number of contiguous positions after the two sequences are optimally aligned.

Optimal alignment of sequences for comparison may be conducted by the local homology algorithm of Smith et al. Adv. Appl. Math. 2: 482 ( 1981), by the homology alignment algorithm of Needleman et al , J. Mol. B l 48:443 (1970), by the search for similarity method of Pearson er al , Proc. Natl. Acad. Sa. USA, 85: 2444 (1988), by computerized implementations of these algorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group (GCG), 575 Science Dr. , Madison, WI), or by inspection. A preferred opening site in IL- 13 is just prior to Met-44 of hIL- 13, just at the beginning of the putative second alpha-helix resulting in a circularly permuted IL- 13 having a methionme at position 44 of the native IL-13 at the amino terminus of the cpIL- 13 and the Glycine at position 43 of the native IL-13 at the new carboxyl terminus of the cpIL-13. This carboxyl terminus can be joined to a second protein directly or through a spacer.

Circularly permuted IL- 13 may be made by a number of means known to those of skill in the art. These include chemical synthesis, modification of existing proteins, and expression of circularly permuted proteins using recombmant DNA methodology. The circularly permuted IL-13 may be synthesized using standard chemical peptide synthesis techniques as discussed below in section IV(B). If the linker is a peptide it may be incorporated during the synthesis. If the linker is not a peptide it may be coupled to the peptide after synthesis.

Alternatively, the circularly permuted IL- 13 can be made by chemically modifying a native IL-13 (e.g. a native human IL-13). Generally, this requires reacting the IL-13 in the presence of the linker to form covalent bonds between the linker and the carboxyl and ammo termini of the protein, thus forming a circular protein. New termini are then formed by cleaving the peptide bond joining amino acids at another location. This may be accomplished chemically or enzymatically using, for example, a peptidase. If the cleavage reaction tends to hydrolyze more than one peptide bond, the reaction may be run briefly. Those molecules having more than one peptide bond cleaved will be shorter than the full length circularly permuted molecule and the latter may be isolated by any protein purification technique that selects by size (e.g , by size exclusion chromatography or electrophoresis). Alternatively, vaπous sites in the circular protein may be protected from hydrolysis by chemical modification of the amino acid side chains which may interfere with enzyme binding, or by chemical blocking of the vulnerable groups participating in the peptide bond.

In a preferred embodiment, the circularly permuted IL- 13, or fusion proteins comprising the circularly permuted IL- 13 will be synthesized using recombmant DNA methodology. Generally this involves creating a DNA sequence that encodes the circularly permuted growth factor (or entire fusion protein containing the growth factor), placing the DNA in an expression cassette under the control of a particular promoter, expressing the protein in a host, isolating the expressed protein and, if required, renaturing the protein Recombmant expression of the fusion proteins of this invention is discussed in more detail below in section IV(B).

DNA encoding circularly permuted growth factors or fusion proteins comprising circularly permuted growth factors may be prepared by any suitable method, including, for example, cloning and restriction of appropriate sequences or direct chemical synthesis by methods as discussed below. Alternatively, subsequences may be cloned and the appropriate subsequences cleaved using appropriate restriction enzymes. The fragments may then be ligated to produce the desired DNA sequence.

In a preferred embodiment, DNA encoding the circularly permuted growth factor may be produced using DNA amplification methods, for example polymerase chain reaction (PCR). First, the segments of the native DNA on either side of the new terminus are amplified separately. The 5' end of the one amplified sequence encodes the peptide linker, while the 3' end of the other amplified sequence also encodes the peptide linker. Since the 5' end of the first fragment is complementary to the 3' end of the second fragment, the two fragments (after partial purification, e.g. on LMP agarose) can be used as an overlapping template in a third PCR reaction. The amplified sequence will contain codons the segment on the carboxy side of the opening site (now forming the amino sequence), the linker, and the sequence on the amino side of the opening site (now forming the carboxyl sequence). The circularly permuted molecule may then be ligated into a plasmid and expressed as discussed below.

D Modified IL-13.

One of skill in the art will appreciate that IL- 13 can be modified in a variety of ways that do not destroy binding specificity and/or avidity and, in fact, may increase binding properties. Some modifications may be made to facilitate the cloning, expression, or incorporation of the circularly permuted growth factor into a fusion protein. Such modifications are well known to those of skill in the art and include, for example, a methionine added at the amino terminus to provide an initiation site to a mature polypeptide, or additional amino acids placed on either terminus to create conveniently located restriction sites or termination codons.

One of skill will recognize that other modifications may be made. Thus, for example, amino acid substitutions may be made that increase specificity or binding affinity of the circularly permuted protein, etc. Alternatively, non-essential regions of

the molecule may be shortened or eliminated entirely. Thus, where there are regions ot the molecule that are not themselves involved in the activity of the molecule, they may be eliminated or replaced with shorter segments that merely serve to maintain the correct spatial relationships between the active components of the molecule.

E) Other targeting antibodies.

Where the chimeric molecule contains more than one targeting molecule (e.g. a dual-targeted cytotoxin), the molecule may contain targeting antibodies directed to tumor markers other than the overexpressed IL-13 receptor. A number of such antibodies are known and have even been converted to form suitable for incorporation into fusion proteins. These include antι-erbB2, B3, BR96, OVB3. anti-transferπn, Mik- βl and PR1 (see Batra et al , Mol. Cell BioL , 1 1 : 2200-2205 (1991 ); Batra et al , Proc Natl Acad. Sa. USA, 89: 5867-5871 (1992); Bπnkmann, et al. Proc. Nail Acad. Sa USA, 88: 8616-8620 (1991); Brink ann et al , Proc. Natl Acad. Sa. USA, 90. 547-551 (1993); Chaudhary et al , Proc. Natl. Acad. Sa. USA, 87: 1066- 1070 ( 1990), Friedman et al , Cancer Res. 53: 334-339 (1993); Kreitman et al , J. Immunol , 149: 2810-2815 (1992); Nicholls et al , J. Biol Che ., 268: 5302-5308 ( 1993); and Wells, er al , Cancer Res. , 52: 6310-6317 (1992), respectively).

III. The Effector Molecule.

As described above, the effector molecule component ot the chimeπc molecules of this invention may be any molecule whose activity it is desired to deliver to cells that overexpress IL-13 receptors. Particularly preferred effector molecules include cytotoxins such as PE or DT, radionuchdes, ligands such as growth factors, antibodies, detectable labels such as fluorescent or radioactive labels, and therapeutic compositions such as liposomes and various drugs.

A) Cytotoxins.

Particularly preferred cytotoxins include Pseudomonas exotoxins, Diphtheria toxins, πcin, abπn, cytotoxic prodrugs, πbonucleases (e.g. , .Ribonuclease

A), and ribozymes. Pseudomonas exotoxin and Dipthteria toxin, doxorubicin and maytanisinoids are most preferred. i. Pseudomonas exotoxin (PE).

Pseudomonas exotoxin A (PE) is an extremely active monomeric protein (molecular weight 66 kD), secreted by Pseudomonas aeruginosa, which inhibits protein synthesis in eukaryotic cells through the inactivation of elongation factor 2 (EF-2) by catalyzing its ADP-ribosylation (catalyzing the transfer of the ADP ribosyl moiety of oxidized NAD onto EF-2).

The toxin contains three structural domains that act in concert to cause cytotoxicity. Domain la (amino acids 1-252) mediates cell binding. Domain II (amino acids 253-364) is responsible for translocation into the cytosol and domain III (amino acids 400-613) mediates ADP ribosylation of elongation factor 2, which inactivates the protein and causes cell death. The function of domain lb (amino acids 365-399) remains undefined, although a large part of it, amino acids 365-380, can be deleted without loss of cytotoxicity. See Siegall et al , J. Biol Chem. 264: 14256-14261 ( 1989).

Where the targeting molecule (e.g. IL- 13) is fused to PE, a preferred PE molecule is one in which domain la (amino acids 1 through 252) is deleted and amino acids 365 to 380 have been deleted from domain lb. However all of domain lb and a portion of domain II (amino acids 350 to 394) can be deleted, particularly if the deleted sequences are replaced with a linking peptide such as GGGGS.

In addition, the PE molecules can be further modified using site-directed mutagenesis or other techniques known in the art, to alter the molecule for a particular desired application. Means to alter the PE molecule in a manner that does not substantially affect the functional advantages provided by the PE molecules described here can also be used and such resulting molecules are intended to be covered herein.

For maximum cytotoxic properties of a preferred PE molecule, several modifications to the molecule are recommended. An appropriate carboxyl terminal sequence to the recombinant molecule is preferred to translocate the molecule into the cytosol of target cells. Amino acid sequences which have been found to be effective include, REDLK (as in native PE), REDL, RDEL, or KDEL, repeats of those, or other sequences that function to maintain or recycle proteins into the endoplasmic reticulum.

referred to here as "endoplasmic retention sequences". See, for example, Chaudhary et al, Proc. Natl. Acad. Sa. USA 87:308-312 and Seetharam et al, J. Brol Chem. 266: 17376-17381 (1991).

Deletions of amino acids 365-380 of domain lb can be made without loss of activity. Further, a substitution of methionine at amino acid position 280 in place of glycine to allow the synthesis of the protein to begin and of seπne at amino acid position 287 in place of cysteine to prevent formation of improper disulfide bonds is beneficial.

In a preferred embodiment, the targeting molecule is inserted in replacement for domain la. A similar insertion has been accomplished in what is known as the TGFα-PE40 molecule (also referred to as TP40) described in Heimbrook et al. , Proc. Natl Acad. Sci. , USA, 87: 4697-4701 (1990) and in U.S. Patent 5,458,878

Preferred forms of PE contain amino acids 253-364 and 381 -608, and are followed by the native sequences REDLK or the mutant sequences KDEL or RDEL. Lysines at positions 590 and 606 may or may not be mutated to glutamine. In a particularly preferred embodiment, the IL- 13 receptor targeted cytotoxins of this invention comprise the PE molecule designated PE38QQR. This PE molecule is a truncated form of PE composed of amino acids 253-364 and 381 -608. The lysine residues at positions 509 and 606 are replaced by glutamine and at 613 are replaced by arginine (Debinski et al. Bioconj. Chem , 5' 40 (1994)). In another particularly preferred embodiment, the IL- 13 receptor targeted cytotoxins of this invention comprise the PE molecule designated PE4E. PE4E is a "full length" PE with a mutated and inactive native binding domain where amino acids 57, 246, 247, and 249 are all replaced by glutamates (see, e.g. , Chaudhary et al , J Biol Chem. , 265: 16306 (1995)). The targeting molecule (e.g. IL- 13 or antι-IL- 13R antibody) may also be inserted at a point within domain III of the PE molecule. Most preferably the targeting molecule is fused between about amino acid positions 607 and 609 of the PE molecule. This means that the targeting molecule is inserted after about ammo acid 607 of the molecule and an appropriate carboxyl end of PE is recreated by placing amino acids about 604-613 of PE after the targeting molecule. Thus, the targeting molecule is inserted within the recombmant PE molecule after about amino acid 607 and is followed

by amino acids 604-613 of domain III. The targeting molecule may also be inserted into domain lb to replace sequences not necessary for toxicity. Debinski, et al Mol. Cell. BioL , 11: 1751-1753 (1991).

In a preferred embodiment, the PE molecules will be fused to the targeting molecule by recombinant means. The genes encoding protein chains may be cloned in cDNA or in genomic form by any cloning procedure known to those skilled in the art (see, e.g. , Sambrook et al , Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory, (1989)). Methods of cloning genes encoding PE fused to various ligands are well known to those of skill in the art (see, e.g. , Siegall et al. , FASEB J. , 3: 2647-2652 (1989); and Chaudhary et al. Proc. Natl Acad. Sa. USA, 84: 4538-4542 (1987)).

Those skilled in the art will realize that additional modifications, deletions, insertions and the like may be made to the chimeric molecules of the present invention or to the nucleic acid sequences encoding IL-13 receptor-directed chimeric molecules. Especially, deletions or changes may be made in PE or in a linker connecting an antibody gene to PE, in order to increase cytotoxicity of the fusion protein toward target cells or to decrease nonspecific cytotoxicity toward cells without antigen for the antibody. All such constructions may be made by methods of genetic engineering well known to those skilled in the art (see, generally, Sambrook et al. , supra) and may produce proteins that have differing properties of affinity, specificity, stability and toxicity that make them particularly suitable for various clinical or biological applications. ii. Diphtheria toxin (DT).

Like PE, diphtheria toxin (DT) kills cells by ADP-ribosylating elongation factor 2 thereby inhibiting protein synthesis. Diphtheria toxin, however, is divided into two chains, A and B, linked by a disulfide bridge. In contrast to PE, chain B of DT, which is on the carboxyl end, is responsible for receptor binding and chain A, which is present on the amino end, contains the enzymatic activity (Uchida et al. , Science, 175: 901-903 (1972); Uchida er al J. Biol. Chem. , 248: 3838-3844 ( 1973)). In a preferred embodiment, the targeting molecule-Diphtheria toxin fusion proteins of this invention have the native receptor-binding domain removed by truncation

of the Diphtheria toxin B chain. Particularly preferred is DT388, a DT in which the carboxyl terminal sequence beginning at residue 389 is removed. Chaudhary, er al. , Bioch. Biophys. Res. Comm. , 180: 545-551 (1991).

Like the PE chimeric cytotoxins, the DT molecules may be chemically conjugated to the IL-13 receptor targeting molecule, but, in a preferred embodiment, the targeting molecule will be fused to the Diphtheria toxin by recombinant means. The genes encoding protein chains may be cloned in cDNA or in genomic form by any cloning procedure known to those skilled in the art. Methods of cloning genes encoding DT fused to various ligands are also well known to those of skill in the art (see, e.g. , Williams et al. J. Biol. Chem. 265: 11885-1 1889 (1990)).

The term "Diphtheria toxin" (DT) as used herein refers to full length native DT or to a DT that has been modified. Modifications typically include removal of the targeting domain in the B chain and, more specifically, involve truncations of the carboxyl region of the B chain.

iii) Cvtotoxic prodrugs.

In another embodiment, the cytotoxic moiety is a cytotoxic prodrug or a moiety (e.g. , an enzyme) capable of converting a "cytotoxic" prodrug from its inactive (non-cytotoxic) prodrug form to its cytotoxic (active) form. The chimeric molecule bearing the "conversion enzyme" or the prodrug itself is contacted with the target

(tumor) cell in the presence of an IL-4 receptor blocker. In the presence of the 1L-4 receptor blocker the chimeric molecule specifically binds to tumor cells overexpressing IL-13 receptors thereby localizing the prodrug or "conversion enzyme" at the tumor site. The prodrug or "conversion enzyme" is then contacted with its corresponding conversion enzyme or prodrug thereby converting the prodrug into its cytotoxic form at the tumor site thereby causing the inhibition of growth or killing of tumor cells.

Suitable prodrugs are well known to those of skill in the art and include, for example, etoposide-4' phosphate or 7-(2'aminoethyl phosphate)mitomycin which are activated in the presence of alkaline phosphatase (AP) to effect killing of tumor cells. Other prodrugs include the prodrug N-(p-hydroxyphenoxyacetyl)adriamycin which is

used in conjunction with penicillin V amidase (PVA) or 5-fluorocytosine which is used in conjunction with cytosine deaminase (CD) (see, e.g. , U.S. Patent 4,957,278). iv. Ricin and Abrin

Ricin and abrin are plant derived cytotoxins well known to those of skill in the art. Like Pseudomonas exotoxin and Diphtheria toxin, ricin and abrin can also be linked to a targeting moiety (e.g. , a molecule that specifically binds the IL- 13 receptor) for specific delivery to cell bearing a particular target molecule. Means of joining ricin and abrin to a targeting molecule are well known to those of skill in the art (see, e.g. , Pastan et al Ann. Rev. Biochm. , 61 : 331-354 (1992), Thrush et al , Ann. Rev. lmm. 14: 49-71 (1996) and references cited therein).

B) Detectable labels.

Detectable labels suitable for use as the effector molecule component of the chimeric molecules of this invention include any composition detectable by spectroscopic, photochemical, biochemical, immunochemical, electrical, optical or chemical means. Useful labels in the present invention include magnetic beads (e.g. Dynabeads™), fluorescent dyes (e.g. , fluorescein isothiocyanate, texas red, rhodamine, green fluorescent protein, and the like), radiolabels (e.g. , ^} H, ^l25 I, "S, ^l C, or ³² P), enzymes (e.g. , horse radish peroxidase, alkaline phosphatase and others commonly used in an ELISA), and colorimetric labels such as colloidal gold or colored glass or plastic

(e.g. polystyrene, polypropylene, latex, etc.) beads.

Means of detecting such labels are well known to those of skill in the art. Thus, for example, radiolabels may be detected using photographic film or scintillation counters, fluorescent markers may be detected using a photodetector to detect emitted illumination. Enzymatic labels are typically detected by providing the enzyme with a substrate and detecting the reaction product produced by the action of the enzyme on the substrate, and colorimetric labels are detected by simply visualizing the colored label.

C) Ligands. As explained above, the effector molecule may also be a ligand or an antibody. Particularly preferred ligand and antibodies are those that bind to surface

markers on immune cells. Chimeric molecules utilizing such antibodies as effector molecules act as bifunctional linkers establishing an association between the immune cells beaπng binding partner tor the ligand or antibody and the tumor cells overexpressmg the IL- 13 receptor Suitable antibodies and growth factors are known to those of skill in the art and include, but are not limited to, IL-2, IL-4, IL-6, IL-7, tumor necrosis factor (TNF), anti-Tac, TGFα, and the like

D Other therapeutic moieties.

Other suitable effector molecules include pharmacological agents or encapsulation systems containing various pharmacological agents Thus, the targeting molecule of the chimeric molecule may be attached directly to a drug that is to be delivered directly to the tumor Such drugs are well known to those ot skill in the art and include, but are not limited to, doxorubicin, vinblastine, genistein, an antisense molecule, and the like. Alternatively, the effector molecule may be an encapsulation system, such as a liposome or micelle that contains a therapeutic composition such as a drug, a nucleic acid (e.g. an antisense nucleic acid), or another therapeutic moiety that is preferably shielded from direct exposure to the circulatory system Means of preparing liposomes attached to antibodies are well known to those of skill in the art See, tor example, U S Patent No. 4,957,735, Connor et al , Pharm Ther , 28- 341-365 ( 1985)

IV. Attachment nf the T-irgetinp Molecule to the Effector Mo.eriile.

One of skill will appreciate that the targeting molecule and effector molecules may be joined together in any order Thus, where the targeting molecule is a polypeptide, the effector molecule may be joined to either the amino or carboxy termini of the targeting molecule. The targeting molecule may also be joined to an internal region of the effector molecule, or conversely, the ettector molecule may be joined to an internal location of the targeting molecule, as long as the attachment does not interfere with the respective activities ot the molecules The targeting molecule and the effector molecule may be attached by any of a number of means well known to those of skill in the art Typically the effector

molecule is conjugated, either directly or through a linker (spacer), to the targeting molecule. However, where both the effector molecule and the targeting molecule are polypeptides it is preferable to recombinantly express the chimeric molecule as a single- chain fusion protein.

A.) Conjugation of the effector molecule to the targeting molecule.

In one embodiment, the targeting molecule (e.g. , IL- 13, cpIL-13, or anti- IL-13R antibody) is chemically conjugated to the effector molecule (e.g. , a cytotoxin, a label, a ligand, or a drug or liposome). Means of chemically conjugating molecules are well known to those of skill.

The procedure for attaching an agent to an antibody or other polypeptide targeting molecule will vary according to the chemical structure of the agent. Polypeptides typically contain variety of functional groups; e.g. , carboxyhc acid (COOH) or free amine (-NH ₂ ) groups, which are available for reaction with a suitable functional group on an effector molecule to bind the effector thereto.

Alternatively, the targeting molecule and/or effector molecule may be derivatized to expose or attach additional reactive functional groups. The deπvatization may involve attachment of any of a number of linker molecules such as those available from Pierce Chemical Company, Rockford Illinois. A "linker" , as used herein, is a molecule that is used to join the targeting molecule to the effector molecule. The linker is capable of forming covalent bonds to both the targeting molecule and to the effector molecule. Suitable linkers are well known to those of skill in the art and include, but are not limited to, straight or branched-chain carbon linkers, heterocyclic carbon linkers, or peptide linkers. Where the targeting molecule and the effector molecule are polypeptides, the linkers may be joined to the constituent amino acids through their side groups (e.g. , through a disulfide linkage to cysteine). However, in a preferred embodiment, the linkers will be joined to the alpha carbon amino and carboxyl groups of the terminal amino acids.

A bifunctional linker having one functional group reactive with a group on a particular agent, and another group reactive with an antibody, may be used to form the desired immunoconjugate. Alternatively, deπvatization may involve chemical

treatment of the targeting molecule, e.g. , glycol cleavage of the sugar moiety of a the glycoprotein antibody with periodate to generate free aldehyde groups. The free aldehyde groups on the antibody may be reacted with free amine or hydrazine groups on an agent to bind the agent thereto. (See U.S. Patent No. 4,671 ,958). Procedures for generation of free sulfhydryl groups on polypeptide, such as antibodies or antibody fragments, are also known (See U.S. Pat. No. 4,659,839).

Many procedure and linker molecules for attachment of various compounds including radionuclide metal chelates, toxins and drugs to proteins such as antibodies are known. See, for example, European Patent Application No. 188,256; U.S. Patent Nos. 4,671 ,958, 4,659,839, 4,414, 148, 4,699,784; 4,680,338; 4,569,789; and 4,589,071 ; and Borlinghaus er al. Cancer Res. 47: 4071-4075 ( 1987). In particular. production of various immunotoxins is well-known within the art and can be found, for example in "Monoclonal Antibody-Toxin Conjugates: Aiming the Magic Bullet, " Thorpe et al , Monoclonal Antibodies in Clinical Medicine, Academic Press, pp. 168- 190 (1982), Waldmann, Science, 252: 1657 ( 1991), U.S. Patent Nos. 4,545,985 and

4,894,443.

In some circumstances, it is desirable to free the effector molecule from the targeting molecule when the chimeric molecule has reached its target site. Therefore, chimeric conjugates comprising linkages which are cleavable in the vicinity of the target site may be used when the effector is to be released at the target site. Cleaving of the linkage to release the agent from the antibody may be prompted by enzymatic activity or conditions to which the i munoconjugate is subjected either inside the target cell or in the vicinity of the target site. When the target site is a tumor, a linker which is cleavable under conditions present at the tumor site (e.g. when exposed to tumor- associated enzymes or acidic pH) may be used.

A number of different cleavable linkers are known to those of skill in the art. See U.S. Pat. Nos. 4,618,492; 4,542,225, and 4,625,014. The mechanisms for release of an agent from these linker groups include, for example, irradiation of a photolabile bond and acid-catalyzed hydrolysis. U.S. Pat. No. 4,671 ,958, for example, includes a description of immunoconjugates comprising linkers which are cleaved at the target site in vivo by the proteolytic enzymes of the patient's complement system. In

view of the large number of methods that have been reported for attaching a variety of radiodiagnostic compounds, radiotherapeutic compounds, drugs, toxins, and other agents to antibodies one skilled in the art will be able to determine a suitable method for attaching a given agent to an antibody or other polypeptide.

B) Production of fusion proteins.

Where the targeting molecule and/or the effector molecule is relatively short (i.e. , less than about 50 amino acids) they may be synthesized using standard chemical peptide synthesis techniques. Where both molecules are relatively short the chimeric molecule may be synthesized as a single contiguous polypeptide. Alternatively the targeting molecule and the effector molecule may be synthesized separately and then fused by condensation of the amino terminus of one molecule with the carboxyl terminus of the other molecule thereby forming a peptide bond. Alternatively, the targeting and effector molecules may each be condensed with one end of a peptide spacer molecule thereby forming a contiguous fusion protein.

Solid phase synthesis in which the C-terminal amino acid of the sequence is attached to an insoluble support followed by sequential addition of the remaining amino acids in the sequence is the preferred method for the chemical synthesis of the polypeptides of this invention. Techniques for solid phase synthesis are described by Barany and Merrifield, Solid-Phase Peptide Synthesis; pp. 3-284 in The Peptides:

Analysis, Synthesis, Biology. Vol. 2: Special Methods in Peptide Synthesis, Parr A. , Merrifield, et al J. Am. Chem. Soc , 85: 2149-2156 ( 1963), and Stewart et al , Solid Phase Peptide Synthesis, 2nd ed. Pierce Chem. Co. , Rockford, 111. ( 1984).

In a preferred embodiment, the chimeric fusion proteins of the present invention are synthesized using recombinant DNA methodology. Generally this involves creating a DNA sequence that encodes the fusion protein, placing the DNA in an expression cassette under the control of a particular promoter, expressing the protein in a host, isolating the expressed protein and, if required, renaturing the protein.

DNA encoding the fusion proteins (e.g. IL-13-PE38QQR) of this invention may be prepared by any suitable method, including, for example, cloning and restriction of appropriate sequences or direct chemical synthesis by methods such as the

phosphotriester method of Narang et al. Met . Enzy ol. 68: 90-99 ( 1979); the phosphodiester method of Brown et al , Meth. Enzymol. 68: 109- 151 (1979); the diethylphosphoramidite method of Beaucage et al , Tetra. Lett. , 22: 1859-1862 ( 1981 ); and the solid support method of U.S. Patent No. 4,458,066. Chemical synthesis produces a single stranded oligonucleotide. This may be converted into double stranded DNA by hybridization with a complementary sequence, or by polymerization with a DNA polymerase using the single strand as a template. One of skill would recognize that while chemical synthesis of DNA is limited to sequences of about 100 bases, longer sequences may be obtained by the hgation of shorter sequences.

Alternatively, subsequences may be cloned and the appropriate subsequences cleaved using appropriate restriction enzymes. The fragments may then be ligated to produce the desired DNA sequence.

In a preferred embodiment, DNA encoding fusion proteins of the present invention may be cloned using DNA amplification methods such as polymerase chain reaction (PCR). Thus, in a preferred embodiment, the gene for IL- 13 is PCR amplified, using a sense primer containing the restriction site for Ndel and an antisense primer containing the restriction site for Hindlll. In a particularly preferred embodiment, the primers are selected to amplify the nucleic acid starting at position 19, as described by McKenzie et al. (1993), supra. This produces a nucleic acid encoding the mature IL-13 sequence and having terminal restriction sites. A PE38QQR fragment may be cut out of the plas id pWDMH4-38QQR or plas id pSGC242FdN l described by Debinski et al. Int. J. Cancer, 58: 744-748 ( 1994), and by Debinski et al , Clin. Cancer. Res. , I : 1015-1022 (1995), respectively. Ligation of the IL-13 and PE38QQR sequences and insertion into a vector produces a vector encoding IL- 13 joined to the amino terminus of

PE38QQR (position 253 of PE). The two molecules are joined by a three amino acid junction consisting of glutamic acid, alanine, and phenylalanine introduced by the restriction site.

While the two molecules are preferably essentially directly joined together, one of skill will appreciate that the molecules may be separated by a peptide spacer consisting of one or more amino acids. Generally the spacer will have no specific

biological activity other than to join the proteins or to preserve some minimum distance or other spatial relationship between them. However, the constituent amino acids of the spacer may be selected to influence some property of the molecule such as the folding, net charge, or hydrophobicity. The nucleic acid sequences encoding the fusion proteins may be expressed in a variety of host cells, including E. coli, other bacterial hosts, yeast, and various higher eukaryotic cells such as the COS, CHO and HeLa cells lines and myeloma cell lines. The recombinant protein gene will be operably linked to appropriate expression control sequences for each host. For E. coli this includes a promoter such as the T7, tip, or lambda promoters, a ribosome binding site and preferably a transcription termination signal. For eukaryotic cells, the control sequences will include a promoter and preferably an enhancer derived from immunoglobulin genes, SV40, cytomegalovirus, etc. , and a polyadenylation sequence, and may include splice donor and acceptor sequences. The plasmids of the invention can be transferred into the chosen host cell by well-known methods such as calcium chloride transformation for E. coli and calcium phosphate treatment or electroporation for mammalian cells. Cells transformed by the plasmids can be selected by resistance to antibiotics conferred by genes contained on the plasmids, such as the amp, gpt, neo and hyg genes. Once expressed, the recombinant fusion proteins can be purified according to standard procedures of the art, including ammonium sulfate precipitation, affinity columns, column chromatography, gel electrophoresis and the like (see, generally, R. Scopes, Protein Purification, Springer- Verlag, N.Y. ( 1982), Deutscher, Methods in Enzymology Vol 182: Guide to Protein Purification. , Academic Press, Inc. N.Y. (1990)). Substantially pure compositions of at least about 90 to 95 % homogeneity are preferred, and 98 to 99% or more homogeneity are most preferred for pharmaceutical uses. Once purified, partially or to homogeneity as desired, the polypeptides may then be used therapeutically.

One of skill in the art would recognize that after chemical synthesis, biological expression, or purification, the IL- 13 receptor targeted fusion protein may possess a conformation substantially different than the native conformations of the

constituent polypeptides. In this case, it may be necessary to denature and reduce the polypeptide and then to cause the polypeptide to re-told into the preferred conformation Methods of reducing and denaturing proteins and inducing re-folding are well known to those of skill in the art (See, Debinski et al. J. Biol Chem. , 268. 14065-14070 ( 1993), Kreitman and Pastan, Bioconjug. Chem. , 4: 581-585 ( 1993), and Buchner, et al , Anal

Biochem. , 205: 263-270 (1992)). Debinski et al. , for example, describe the denaturation and reduction of inclusion body proteins in guanidine-DTE. The protein is then refolded in a redox buffer containing oxidized glutathione and L-arginine

One of skill would recognize that modifications can be made to the IL- 13 receptor targeted fusion proteins without diminishing their biological activity Some modifications may be made to facilitate the cloning, expression, or incorporation ot the targeting molecule into a fusion protein Such modifications are well known to those ot skill in the art and include, for example, a methionine added at the amino terminus to provide an initiation site, or additional amino acids placed on either terminus to create conveniently located restriction sites or termination codons

V. The II-4 receptor hloeker.

As indicated above, in a preferred embodiment, the chimeric molecules of this invention are preferably contacted with tumor cells in the presence of a blocker ot an IL-4 receptor The blocker can be any moiety that specifically binds to the IL-4 receptor and thereby reduces and/or prevents binding ot targeting moieties that are directed against the IL-13 receptor IL-4 receptor blockers include, but are not limited to ligands, antibodies, and small organic molecules that specifically bind to the IL-4 receptor. Thus, for example, IL-4 itself, when added or otherwise upregulated, can act as an IL-4 receptor blocker for this invention However, because systemic upregulation of IL-4 receptor activity can have pathophysiological consequences, preferred blockers bind to the IL-4 receptor with reduced or no agonistic activity In addition to blocking the IL-13 targeting molecule, they also act to antagonize (competitively inhibit) IL-4

Means of identifying and/or designing IL-4 antagonists are well known to those of skill in the art. Human ιnterleukιn-4 (IL-4) activates its cognate receptor system by sequential binding to two different receptor subumts The first, high-affinity binding

step (e.g. , K _d 100 pM) involves the interaction between IL-4 receptor subunit (Beckmann et al , In: Interleukins: Molecular Biology and Immunology. Chem. Immunol , Kishimoto, T., ed. 51 : 2213-2218 (1992); Galizzi et al , Int. Immunol , 2: 669-675 (1990), and Idzerda et al J. Exp. Med. , 171 : 861-873 ( 1990)) and IL-4 amino acid residues located on helices A and C ((Kruse et al EMBO J. , 12: 5121-5129 ( 1993), and Ramanathan et al. Biochem. , 32: 3549-3556 (1993)) The subsequent second binding step involves a signaling site on helix D of IL-4 (Kruse et al. EMBO J. , 3237-3244 (1992)) and a further receptor subunit which is believed to be the γ chain of the IL-2 receptor system. The two-step binding scheme leads to a simple rationale for the design of antagonistic IL-4 variants (IL-4 receptor blockers). Simply mutating (i. e. destroying or disrupting) the second binding site of IL-4 produces a ligand that will bind to, but not activate the IL-4 receptor (see, e.g. , Cunningham et al Science, 254: 821-825 ( 1991 ), De Vos, et al , Science 255: 306-312, Fuh et al Science, 256: 1677- 1680 ( 1992), Kruse et al. EMBO J. , 3237-3244 ( 1992)).

As indicated by the cited references, methods of mutating IL-4 to produce IL-4 antagonists are well known to those of skill in the art. It is well known that amino acid residues on α-helix D of IL-4 are involved in the second binding site that mediates signal transduction. Thus, mutations, insertions, or deletions, that alter or disrupt the D helix will generate IL-4 antagonists. For example, it is known that the signaling site of human IL-4 comprises side chains of Argl21 , Tyrl24, and Serl25. These residues thus provide particularly suitable sites for mutation.

Preferred mutations will involve substituting one amino acid for another having different properties. Thus, for example, a negatively charged (at pH 6) amino acid can be substituted for a positively charged, neutral polar or non-polar (at pH 6) amino acid. Mutations known to reduce or eliminate agonistic IL-4 activity include, but are not limited to substitution of arginine 121 with aspartic acid ([R 121 D]IL-4), substitution of serine 125 with aspartic acid ([S 125D]IL-4), substitution of tyrosine 124 with aspartic acid ([Y124D]IL-4) (see, e.g. , Tony et al. Europ. J. Biochem. , 225: 659- 665 (1994)). Of course, multiple mutations can also be made. These include, but are not limited to [R121D,Y 124D]IL-4, [R121D, S 125D]IL-4, [Y 124D, S 125DJIL-4,

[R121D, Y124D, S125D]IL-4, and the like. Other variants can include deletions of C or g C-terminal amino acids.

One of skill will appreciate that IL-4R blockers can also be created by deleting large sections of IL-4 leaving only sufficient residues to maintain minimal required structure and to mediate binding to the IL-4 receptor. Such peptide "mimetics" are well known to those of skill in the art and can be routinely produced by rational design using knowledge of the structure of the IL-4 and IL-4R interaction and/or by screening and/or "directed evolution" using IL-4R and tumor expressed IL-13R as positive and negative targets respectively. Methods of using phage display and directed evolution for producing polypeptides that high specific affinities for a particular target molecule are well known to those of skill in the art (see, e.g , Noren, NEB Transcript, 8: 1-5 (1996), Li et al. Nature Biorechnology, 14. 986-991 ( 1996), Moore ewr al Nature Biotechnology, 14: 458-467 ( 1996), and Vaughan er al Nature Biotechnology, 14: 309-314 (1996), Wπghton et al , Science, 273. 458-463 ( 1996), and references cited therein). The above-described IL-4 vaπants (e.g. , [Y l 19D]IL-4) and other IL-4R blockers can be routinely made as described above, and screened as described below in Section VI.

One of skill in the art will appreciate that other moieties besides ligands such as IL-4 and its variants can be used to block IL-4 receptors For example, antι-IL-4 antibodies can also be used to block binding of IL- 13R targeting moieties to the IL-4 receptor. Antibodies that specifically bind to and block the IL-4 receptor are well known to those of skill in the art and are described, for example, by Reusch et al Eur. J. Biochem. , 222: 491 -499 (1994). Representative antι-IL-4R antibodies include, but are not limited to sl03, s456, s6g7, sg24, and o2g6 (see, e.g. , Zurawski er al J. Biol Chem. , 13: 13869- 13878 (1995)). One of skill in the art will appreciate that the antibodies may be human or humanized as described above.

Small organic molecules can also be used to block the I -4 receptor Such small organic molecules can be rationally designed based on the extensive knowledge in the field regarding the IL-4 receptor binding site (see, e ^■ >. , Muller er al J. Mol Biol , 237: 423-436 ( 1994), Tony er al , Eur J Biochem. , 225 ' 659-665 ( 1994) and references cited therein) and/or screened for using high throughput screening

methodologies applied to combinatorial libraries. Screening methods involve screening the putative IL-4R blocker against IL-4 receptors and against IL- 13 receptors to identify those that block IL-4R and not IL- 13R. Methods of generating combinatorial libraries and screening such libraries using high-throughput methods are well known to those of skill in the art (see, e.g., Baum, C&EN (Feb. 7, 1994): 20-26 and references cited therein).

In another embodiment, the IL-4 receptor blockers of this invention can be provided as chemical conjugates or as fusions with other molecules to increase their effective molecular weight and hence their serum half-life. The attachment or fusion may be to virtually any large molecule compatible with components in the serum of the subject organism. Thus, for example, the 1L-4 receptor blocker may be conjugated or fused to a lipid, a protein (e.g. , serum albumin), a polysaccharide, an antibody or ligand, and the like. Of course, the conjugated or fused IL-4 receptor blocker will be screened for binding affinity to an IL-4 receptor as described below and in the examples.

VI. Screening blockers for efficacy.

Blockers suitable for use in this invention are readily identified by routine screening. In a preferred embodiment, the screening will entail utilizing the blocker in conjunction with an IL-4R directed and an IL- 13R directed cytotoxin. Normal cells (having IL-4 receptors and few or no IL- 13 receptors) and tumor cells overexpressing the IL-13 receptor will be contacted with the cytotoxin in the presence and absence of the putative blocker. Blockers that reduce or eliminate cytotoxic activity of the IL- 13R directed chimeric molecule on normal cells, but cause little or no reduction in cytotoxicity on tumor cells are suitable for use in the methods of this invention In a preferred embodiment, the cytotoxicity of the chimeπc toxins is determined using a colorimetric MTS ([3-(4,5-dimethylfhiazol-2-yl)-5-(3- carboxymethoxyphenyl)-2-(4-su!fophenyl)-2H-tetrazoliuιn, inner salt) / PMS (phenazine methasulfate) cell proliferation as described in the Examples herein.

VII. Identification of T rget Cells.

It was a surprising discovery of the present invention that tumor cells, overexpress IL-13 receptors. In particular, carcinoma tumor cells (e.g. , renal carcinoma cells) overexpress IL-13 receptors at levels ranging from about 2100 sites/ cell to greater than 150,000 sites per cell. Similarly, gliomas and Kaposi's sarcoma also overexpress

IL-13 receptors (IL-13R). Moreover, every cancer type tested to date appears to overexpress IL-13 receptors. Thus it appears that IL- 13 receptor overexpression is general characteristic of a solid tumor neoplastic cell.

Thus, the methods of this invention can be used to target an effector molecule to virtually any neoplastic cell. Neoplasias are well known to those of skill in the art and include, but are not limited to, cancers of the skin (e.g. , basal or squamous cell carcinoma, melanoma, Kaposi's sarcoma, etc.), cancers of the reproductive system (e.g. , testicular, ovarian, cervical), cancers of the gastrointestinal tract (e.g. , stomach, small intestine, large intestine, colorectal, etc. ), cancers of the mouth and throat (e.g. esophageal, larynx, oropharynx, nasopharynx, oral, etc. ), cancers of the head and neck, bone cancers, breast cancers, liver cancers, prostate cancers (e.g. , prostate carcinoma), thyroid cancers, heart cancers, retinal cancers (e.g. , melanoma), kidney cancers, lung cancers (e.g. , mesothelioma), pancreatic cancers, brain cancers (e.g. gliomas, medulloblastomas, pituitary ademomas, etc. ) and cancers of the lymph system (e.g. lymphoma).

In a particularly preferred embodiment, the methods of this invention are used to target effector molecules to kidney cancers, colorectal cancers (especially colorectal carcinomas), to skin cancers (especially Kaposi's sarcoma), and to brain cancers (especially gliomas, and medulloblastomas). One of skill in the art will appreciate that identification and confirmation of IL-13 overexpression by other cells requires only routine screening using well-known methods. Typically this involves providing a labeled molecule that specifically binds to the IL-13 receptor. The cells in question are then contacted with this molecule and washed. Quantification of the amount of label remaining associated with the test cell provides a measure of the amount of IL- 13 receptor (IL- 13R) present on the surface of that cell.

In a preferred embodiment, IL- 13 receptor may be quantified by measuring the binding of ^l25 I-labeled IL- 13 ( ^12S I-IL- I 3) to the cell in question. Details of such a binding assay are provided in Example 1.

VIII. Pharmaceutical Compositions.

The chimeric molecules and IL-4 receptor blockers of this invention are useful for parenteral, topical, oral, or local administration, such as by aerosol or transdermally, for prophylactic and/or therapeutic treatment. The pharmaceutical compositions can be administered in a variety of unit dosage forms depending upon the method of administration; for example oral administration include powder, tablets, pills, capsules and lozenges. It is recognized that the fusion proteins and IL-4R blockers and pharmaceutical compositions of this invention, when administered orally, must be protected from digestion. This is typically accomplished either by complexing the chimeric molecule and/or blocker with a composition to render it resistant to acidic and enzymatic hydrolysis or by packaging the chimeric molecule and/or blocker in an appropriately resistant carrier such as a liposome. Means of protecting proteins from digestion are well known in the art.

In one particularly preferred embodiment, the chimeric molecule and/or the blocker can be provided in a time-release formulation such that the blocker is released and protects normal cells prior to their coming in contact with the chimeric molecule. Methods of preparing time-release formulations are well known to those of skill in the art (see, e.g. , U.S. Patents 5,079,005, 5,055,300, 4,690,825, 4,608,248, 4,434, 152 and references therein).

In another embodiment, the blocker can be provided by upregulation of endogenous compounds (e.g. , IL-4) that bind to IL-4 receptors. Alternatively, the subject organism can be transfected with one or more vectors or other delivery vehicles that encode and express one or more IL-4 receptor antagonists such as those described above (i.e. , [Y 124D]hIL4 or [R 121 D, Y 124D]hIL4).

A large number of delivery methods are well known to those of skill in the art. Such methods include, for example liposome-based gene delivery (Debs and

Zhu (1993) WO 93/24640; Mannino and Gould-Fogerite ( 1988) BioTechniques 6(7):

682-691; Rose U.S. Pat No. 5,279,833; Brigham ( 1991) WO 91/06309; and Feigner et al. (1987) Proc. Natl. Acad. Sci. USA 84: 7413-7414), and replication-defective retroviral vectors harboring an expression cassette capable of expressing the IL-4R blocker as part of the retroviral genome (see, e.g. , Miller et al. ( 1990) Mol. Cell Biol. 10:4239 (1990); Kolberg ( 1992) J. N1H Res. 4:43, and Cornetta et al. Hum. Gene Ther.

2:215 (1991)). Widely used retroviral vectors include those based upon murine leukemia virus (MuLV), gibbon ape leukemia virus (GaLV), Simian Immuno deficiency virus (SIV), human immuno deficiency virus (HIV), and combinations thereof. See, e.g. , Buchscher et al. ( 1992) J Virol. 66(5) 2731-2739; Johann er al. ( 1992) J Virol. 66 (5): 1635-1640 (1992); Som erfelt et al. , ( 1990) Virol. 176:58-59; Wilson et al.

(1989) J Virol. 63:2374-2378; Miller et al. , J Virol 65:2220-2224 ( 1991 ); Wong-Staal et al , PCT/US94/05700, and Rosenburg and Fauci ( 1993) in Fundamental Immunology, Third Edition Paul (ed) Raven Press, Ltd. , New York and the references therein, and Yu et al , Gene Therapy (1994) supra). In addition to viral particles, a variety of protein coatings can be used to target nucleic acids to selected cell types. For example, transferrin-poiy-cation conjugates enter cells which comprise transferrin receptors. See, e.g. , Zenke et al

(1990) Proc. Natl. Acad. Sci. USA 87: 3655-3659; Curiel ( 1991 ) Proc. Nail. Acad Sci USA 88: 8850-8854 and Wagner et al. (1993) Proc. Natl. Acad. Sci. USA 89:6099- 6013. electrostatically to poly-!-lysine or poly-1-lysine-transferrin which has been linked to defective adenovirus mutants can be delivered to cells with transfection efficiencies approaching 90% (Curiel er al. ( 1991) Proc Nail Acud Sci USA 88:8850-8854; Cotten er al (1992) Proc Natl Acad Sci USA 89:6094-6098; Curiel er al. ( 1992) Hum Gene Ther 3: 147-154; Wagner er al. ( 1992) Proc Narl Acad Sci USA 89:6099-6103; Michael er al.

(1993) J Biol Chem 268:6866-6869; Curiel er al (1992) Am J Respir Cell Mol Biol 6:247-252, and Harris et al. ( 1993) Am J Respir Cell Mol Biol 9:441-447). The adenovirus-poly-1-lysine-DNA conjugate binds to the normal adenovirus receptor and is subsequently internalized by receptor-mediated endocytosis. The adenovirus-poly-1- lysine-DNA conjugate binds to the normal adenovirus receptor and is subsequently internalized by receptor-mediated endocytosis. Similarly, other virus-poly-1-lysιne-DNA

conjugates bind the normal viral receptor and are subsequently internalized by receptor-mediated endocytosis. Accordingly, a variety of viral particles can be used to target vector nucleic acids to cells.

In another embodiment, the blocker can be introduced into the subject organism as a naked expression cassette injected e.g. , naked DNA. The naked DNA, utilizing enzymes provided by the host expresses the encoded IL-4R blocker (see, e.g. , Wolff et. al , Science 247: 1465-1468 (1990)).

The pharmaceutical compositions of this invention are particularly useful for parenteral administration, such as intravenous administration or administration into a body cavity or lumen of an organ. The compositions tor administration will commonly comprise a solution of the chimeric molecule dissolved in a pharmaceutically acceptable carrier, preferably an aqueous carrier. A variety of aqueous carriers can be used, e.g , buffered saline and the like. These solutions are sterile and generally free of undesirable matter. These compositions may be sterilized by conventional, well known sterilization techniques. The compositions may contain pharmaceutically acceptable auxiliary substances as required to approximate physiological conditions such as pH adjusting and buffering agents, toxicity adjusting agents and the like, for example, sodium acetate, sodium chloride, potassium chloride, calcium chloride, sodium lactate and the like The concentration of chimeric molecule and IL-4R blocker in these formulations can vary widely, and will be selected primarily based on fluid volumes, viscosities, body weight and the like in accordance with the particular mode of administration selected and the patient's needs.

Thus, a typical pharmaceutical composition for intravenous administration would be about 0.1 to 10 mg per patient per day. Dosages from 0. 1 up to about 100 mg per patient per day may be used, particularly when the drug is administered to a secluded site and not into the blood stream, such as into a body cavity or into a lumen of an organ. Blocker concentrations will range from about 10 to 1000 times higher than that of the chimeric molecules. Actual methods for preparing parenterally administrable compositions will be known or apparent to those skilled in the art and are described in more detail in such publications as Remington 's Pharmaceutical Science, 15th ed. , Mack Publishing

The compositions containing the present fusion proteins and/or IL-4 receptor blockers or a cocktail thereof (i.e. , with other proteins) can be administered for therapeutic treatments. In therapeutic applications, compositions are administered to a patient suffering from a disease, in an amount sufficient to cure or at least partially arrest the disease and its complications. An amount adequate to accomplish this is defined as a

"therapeutically effective dose. " Amounts effective for this use will depend upon the severity of the disease and the general state of the patient's health.

Single or multiple administrations of the compositions may be administered depending on the dosage and frequency as required and tolerated by the patient. In any event, the composition should provide a sufficient quantity of the proteins of this invention to effectively treat the patient.

Among various uses of the cytotoxic fusion proteins of the present invention are included a variety of disease conditions caused by specific human cells that may be eliminated by the toxic action of the protein. One preferred application is the treatment of cancer, such as by the use of an IL-13 receptor targeting molecule (e.g. IL-

13 or anti-IL-13R antibody) attached to a cytotoxin. These chimeric molecules are preferably utilized in conjunction with an IL-4 receptor blocker as described above. Where the chimeric molecule comprises an IL- 13 receptor targeting molecule attached to a ligand, the ligand portions of the molecule are chosen according to the intended use. Proteins on the membranes of T cells that may serve as targets for the ligand includes CD2 (Ti l), CD3, CD4 and CD8. Proteins found predominantly on B cells that might serve as targets include CD 10 (CALLA antigen), CD 19 and CD20. CD45 is a possible target that occurs broadly on lymphoid cells. These and other possible target lymphocyte target molecules for the chimeric molecules bearing a ligand effector are described in Leukocyte Typing III, A.J. McMichael, ed. , Oxford University

Press (1987). Those skilled in the art will realize ligand effectors may be chosen that bind to receptors expressed on still other types of cells as described above, for example, membrane glycoproteins or ligand or hormone receptors such as epidermal growth factor receptor and the like. It will be appreciated by one of skill in the art that there are some regions that are not heavily vascularized or that are protected by cells joined by tight junctions

and/or active transport mechanisms which reduce or prevent the entry of macromolecules present in the blood stream. Thus, for example, systemic administration of therapeutics to treat some gliomas, or other brain cancers, is constrained by the blood-brain barrier.

The entry of macromolecules into the subarachnoid space is obviously limited due to its anatomical organization as well.

One of skill in the art will appreciate that in these instances, the therapeutic compositions of this invention can be administered directly to the tumor site.

Thus, for example, brain tumors (e.g., gliomas) can be treated by administering the therapeutic composition directly to the tumor site (e.g. , through a surgically implanted catheter). Where the fluid delivery through the catheter is pressurized, small molecules

(e.g. the therapeutic molecules of this invention) will typically infiltrate as much as two to three centimeters beyond the tumor margin.

Alternatively, the therapeutic composition can be placed at the target site in a slow release formulation. Such formulations can include, for example, a biocompatible sponge or other inert or resorbable matrix material impregnated with the therapeutic composition, slow dissolving time release capsules or microcapsules, and the like.

Typically the catheter or time release formulation will be placed at the rumor site as part of a surgical procedure. Thus, for example, where major rumor mass is surgically removed, the perfusing catheter or time release formulation can be emplaced at the tumor site as an adjunct therapy. Of course, surgical removal of the tumor mass may be undesired, not required, or impossible, in which case, the delivery of the therapeutic compositions of this invention may comprise the primary therapeutic modality.

IX. Diagnostic Kits.

In another embodiment, this invention provides for kits for the treatment of rumors or for the detection of cells overexpressing IL-13 receptors. Kits will typically comprise a chimeric molecule of the present invention (e.g. IL-13-label, IL-13-cytotoxin, IL-13-ligand, etc.) and an IL-4 blocking molecule ( .g., [Y124D]hIL4 or [R121D, Y124D]hIL4). In addition the kits will typically include instructional

materials disclosing means of use of the chimeric molecule (e.g. as a cytotoxin, for detection of tumor cells, to augment an immune response, ere ). The kits may also include additional components to facilitate the particular application for which the kit is designed. Thus, for example, where a kit contains a chimeric molecule in which the effector molecule is a detectable label, the kit may additionally contain means of detecting the label (e.g. enzyme substrates for enzymatic labels, filter sets to detect fluorescent labels, appropriate secondary labels such as a sheep anti- mouse-HRP, or the like). The kits may additionally include buffers and other reagents routinely used for the practice of a particular method. Such kits and appropriate contents are well known to those of skill in the art.

EXAMPLES

The following examples are offered to illustrate, but not to limit the claimed invention. Example 1

Identification of Cells that Overexpress H--13

Recombinant human IL-4 and IL- 13 were labeled with ^13S I (Amersham Research Products, Arlington Heights, Illinois, USA) by using the IODO-GEN reagent (Pierce, Rockford, Illinois, USA) according to the manufacturer's instructions. The specific activity of the radiolabeled cytokines was estimated to range from 20 - 100 μCi/μg protein. For binding experiments, typically, lxlO ⁶ renal cell carcinoma (RCC) tumor cells were incubated at 4°C for 2 hours with '" -IL- 13 ( 100 pM) with or without increasing concentrations (up to 500 nM) of unlabeled IL-13. In some experiments, IL- 13R expression was examined as previously described (Obiri er al. J. Clin. Invest. , 91 : 88-93 (1993))). The data were analyzed with the LIGAND program (Munson et al

Anal Biochem. , 107: 220-239 ( 1980)) to determine receptor number and binding affinity.

Four human renal cell carcinoma (RCC) cell lines (WS-RCC, HL-RCC, PM-RCC, and MA-RCC) bound ^l25 I-IL- 13 specifically and the density of IL- 13R varied from 2100 sites per cell in WS-RCC cells to 150,000 sites per cell in HL-RCC cells

(Table 1). The represents an increase in IL- 13 receptor expression ranging from 15 to

about 500 fold as compared to normal immune cells. In contrast, IL-4 receptors overexpressed on cancers have been reported at concentrations as high as 4000 sites per cell. Scatchard analyses (Scatchard, Ann. N. Y. Acad. Sci , 51 : 660-663 (1949)) revealed that only one affinity class of receptors was expressed on each cell line. The binding affinities (Kd) ranged between 100 pM to 400 pM in three RCC cell lines while

HL-RCC ceils expressed lower affinity receptors (Kd ^" 3 nM).

Although IL- 13 responsiveness has previously been reported in human monocytes, B cells and pre-myeloid (TF-1) cells (see, e.g. de Waal Malefyt, et al. J. Immunol , 151 : 6370-6381 (1993), de Waal Malefyt, et al. J. Immunol , 144: 629-633 (1993)), little was known about IL-13R structure or its binding characteristics in these, or any other cells. The present data show that freshly isolated human monocytes, EBV-transformed B cell line and TF- 1 cell line express very few IL- 13 binding sites (100-300/cell) compared to human RCC cells (Table 1 ). On the other hand, no binding of ¹²⁵ I-IL-13 was observed on H9 T cells, LAK cells and resting or PHA activated PBL. This is compatible with the fact that IL- 13 responsiveness has not been observed in T lymphocytes (Punnonen et al , Proc. Natl. Acad. Sci. USA , 90: 3730-3734 (1993).

^c UC=undetectable ^d The Kd could not be reliably calculated because of low binding of ^{l S} I-IL- 13 ^e The peripheral blood derived monocytes ( > 90% purity) were isolated by ficoll- hypaque density gradient followed by ellutriation from a leukopac obtained from normal donor. ^f LAK cells and activated T-lymphocytes were generated by the culture of donor PBLs

(106/ml) with IL-2 (500 Units/ml) for 3 days or PHA ( lOμg/ml) for 3-4 days respectively.

Example 2 ■ T -13 and IL-4 Bind to Different Receptors

Recently, it was proposed that the IL-2Rγ _c receptor subunit is associated with IL-13R (see, e.g. , Russell et al Science 262: 1880- 1883 ( 1993); Kondo er al. Science, 262: 1874-1877 (1993); Noguchi er al. Science, 262: 1877-1880 (1993); Kondo et al. Science 263: 1453-1454 (1994); Giri er al. EMBO J. 13: 2822-2830 (1994))) and IL-13R may share a common component with IL-4R (Zurawski er al EMBO J. 12: 2663-2670 (1993); Aversa er al. J. Exp. Med. 178: 2213-2218 (1993)). To directly address these possibilities, radio-ligand binding experiments were performed, as described in Example 1 , on HL-RCC and WS-RCC cells using ^l2S I-IL-4 or ¹²⁵ I-IL- 13 in the presence or absence of excess of either cytokine.

Unlabeled IL-4 more efficiently inhibited ¹²⁵ I-IL-4 from binding to RCC cells (84%, and 72% displacement of total binding in WS-RCC and HL-RCC, respectively) than IL-13 which also displaced ^l25 I-IL-4 binding to these cells (61 % of total binding in WS-RCC and 51 % in HL-RCC) under similar conditions. On the other hand, while ¹²⁵ I-IL-I3 binding was effectively displaced by IL-13 (about 85 % of total in both cell types), it was only minimally displaced by IL-4 ( 12% of total displacement in WS-RCC, and 7% in HL-RCC). These results indicate that IL-4 and IL-13 both interact with each other's receptors, however, the interaction is not identical since IL-4 inhibition of ¹²⁵ I-IL-13 binding was weak and IL- 13 inhibition of ^l2 T-IL-4 binding was not complete. These results agree with previous observations in which IL- 13 was found to compete with IL-4 binding on TF-1 cells (Zurawski er al , EMBO J. 12: 2663-2670 (1993)). However, in that report the converse experiment was not done. Here, the data show that even though IL-13 competed for IL-4 binding, IL-4 did not compete for IL- 13 binding.

The competition by IL- 13 for IL-4 binding sites on lymphoid MLA 144 cells and RAJI cell lines was also investigated. These cells were incubated with radiolabeled IL-4 with or without excess unlabeled IL-4 or IL-13. Excess unlabeled IL- 4 effectively displaced labeled ⁱ²⁵ I-IL-4 bound to MLA 144 and RAJI cells, while excess IL-13 could not compete this binding. This observation is at variance to that seen with RCC cells in which IL-13 competed for IL-4 binding. The inability of IL- 13 to compete

for ^l25 I-IL-4 binding to MLA 144 is consistent with the observation that IL- 13 did not bind to peripheral blood T (or MLA 144) cells.

Example 3 Siiliunit Structure of L-13 and H.-4 Receptors

The subunit structure of IL-13R on RCC cells was investigated by crosslinking studies. Cells (5 x 10 ^δ ) were labeled with ^{1 5} I-IL- 13 or ^l2S I-IL-4 in the presence or absence of excess IL-13 or IL-4 for 2 h at 4°C. The bound ligand was cross- linked to its receptor with disuccimmidyl suberate (DSS) (Pierce, Rockford, Illinois, USA) at a final concentration of 2 mM for 30 min. Cells were lysed in a buffer containing 1 % Triton X-100, 1 mM phenylmethylsulfonyl fluoride, 0.02 mM leupeptin, 5.0 μ M trypsin inhibitor, 10 mM benzamidine HC1, 1 mM phenanthroline iodoacetamide, 50 mM amino caproic acid, 10 μg/ml pepstatin, and 10 μg/ml aprotinin. The cell lysates were cleared by boiling in buffer containing 2- mercaptoethanol and analyzed by electrophoresis through 8% SDS/polyacrylamide gel. The gel was subsequently dried and autoradiographed. In some experiments, the receptor/ligand complex was lmmunoprecipitated from the lysate overnight at 4°C by incubating with protein A sepharose beads that had been pre-incubated with P7 anti hlL- 4R or anti-γ _c antibody and analyzed as above. The labeled ^l25 I-IL- 13 cross-linked to one major protein on all four RCC cell lines and the complex migrated as a single broad band ranging between 68 and 80 kDa. A single band was also observed on human pre-myeloid TF- I .J61 cells only after much longer exposure of the gel. After subtracting the molecular mass of IL- 13 (12 kDa), the size of IL- 13 binding protein was estimated at 56 to 68 kDa. The ¹² VlL- 13 cross-linked band was not observed when the crosslinking was performed in the presence of 200-fold molar excess of IL- 13. In addition to the major band, a faint band of approximately 45 kDa was also observed in HL-RCC and PM-RCC but not on MA-RCC cells. This band appeared to be specifically associated with IL- 13R because unlabeled IL-13 competed for the binding of I-IL- 13. This band could represent an IL- 13R associated protein or a proteolytic fragment of the larger band. In contrast to the displacement of ^{1 5} I-IL-13 binding by unlabeled IL- 13, an excess of unlabeled IL-4 did

not prevent the appearance of IL- 13R band in RCC cell lines. IL- 13 on the other hand competed for ¹²⁵ I-IL-4 binding to both major proteins on WS-RCC cells. It is of interest that ^12S ML-13-cross-linked protein was slightly larger in size in TF- 1.J61 , WS-RCC, PM-RCC, and HL-RCC cell lines compared to that seen in MA-RCC. Post-translational modifications, such as glycosylation or phosphorylation, may account for this difference.

Example 4

Construction of an IL-13-PE Fusion Protein

Construction of a Plasmid Encoding IL-I3-PE38QQR To construct the chimeric toxin a coding region of the human interleukin

13 (hIL-13) gene ( plasmid JFE14-SR ) (Minty er al . Nature, 362: 248 (1993), McKenzie et al. Proc. Natl Acad. Sci. USA, 90: 3735 (1987)) was fused to a gene encoding PE38QQR, a mutated form of PE, thereby producing a construct (phuIL- 13- Tx) encoding the chimeric molecule. Specifically, a DNA encoding human IL- 1 was PCR-amplified from plasmid JFE14-SRα. New sites were introduced for the restriction endonucleases Ndel and Hind III at the 5' and 3' ends of the hIL-13 gene, respectively by PCR using a sense primer that incorporated the Ndel site and an antisense primer that incorporated the Hindlll site.

The Ndel/Hindlll fragment containing encoding hIL-13 was subcloned into a vector obtained by digestion of plasmid pWDMH4-38QQR (Debinski et al. Int. J.

Cancer 58: 744-748 (1994)) or plasmid pSGC242FdN l (Debinski er al. Clin. Cancer

Res. , 1: 1015-1022 (1995)) with Ndel and Hindlll, to produce plasmid phuIL- 13-Tx.

The 5' end of the gene fusion was sequenced and showed the correct DNA of hIL- 13.

Human interleukin 4 (hIL-4) was cloned into an expression vector in a similar way to hlL-13 using plasmid pWDMH4 (Debinski er al. J. Biol. Chem. 268: 14065-14070 (1993)) as a template for PCR amplification. Recombinant proteins were expressed in E. coli BL21 (λDE3) under control of the T7 late promoter (Id. ). In addition to the T7 bacteriophage late promoter, the plasmids also carried a T7 transcription terminator at the end of the open reading frame of the protein, an f 1 origin of replication and gene for ampicillin . resistance (Debinski er al J. Clin. Invest. 90: 405- 411 (1992)). The plasmids were amplified in E. coli (HB101 or DH5α high efficiency

transformation) (BRL) and DNA was extracted using Qiagen kits (Chatsworth, California, USA).

Expression and purification of recombinant proteins. E. coli BL21 (λDE3) cells were transformed with plasmids of interest and cultured in 1.0 liter of Super broth. Expressed recombinant human IL- 13 and human IL-13-PE38QQR were localized in inclusion bodies. The recombinant proteins were isolated from the inclusion bodies as described by Debinski et al. , J. Biol Chem 268: 14065-14070 (1993). After dialysis, the renatured protein of human IL- 13-PE38QQR was purified on Q-Sepharose Fast Flow and by size exclusion chromatography on

Sephacryl S-200HR (Pharmacia, Piscataway, New Jersey, USA) The initial step of hlL- 13 or hIL-4 purification was conducted on SP-Sepharose Fast Flow (Pharmacia)

Protein concentration was determined by the Bradford assay (Pierce "Plus", Rockford, Illinois, USA) using BSA as a standard. Human IL- 13 and IL- 13-PE38QQR were expressed at high levels in bacteria as seen in SDS-PAGE analysis of the total cell extract. After initial purification on SP-Sepharose (hIL-13) or Q-Sepharose (hIL- 13-PE38QQR) the renatured recombinant proteins were applied onto a Sephacryl S-200 HR Pharmacia column. Human IL-13 and hlL-13-PE38QQR appeared as single entities demonstrating the very high purity of the final products. The chimeric toxin migrated within somewhat lower than expected for 50 kDa protein M range which may be related to the hydrophobicity of the molecule. The biologic activity of the rhIL- 13 was exactly the same as commercially obtained hIL- 13.

Example 5

The Activity of an IL-13-PE Fusion Protein on Human Carcinoma Cells

Cytotoxic activity ofhIL-I3-PE38QQR

The cytotoxic activity of chimeric toxins, such as hIL- 13-PE38QQR, were tested by measuring inhibition of protein synthesis. Protein synthesis was assayed by plating about 1 x 10 ⁴ cells per in a 24-we!l tissue culture plate in 1 ml of medium.

Various concentrations of the chimeric toxins were added 20-28 h following cell plating

After 20 h incubation with chimeric toxins, [ ³ H]-!eucιne was added to cells for 4 h, and the cell-associated radioactivity was measured. For blocking studies, rhIL-2, 4 or 13 was added to cells for 30 min before the chimeric toxin addition. Data were obtained from the average of duplicates and the assays were repeated several times. Several established cancer cell lines were tested to determine if hIL- 13-

PE38QQR is cytotoxic to them. In particular, cancers derived from colon, skin and stomach were examined. The cancer cells were sensitive to hIL-13-PE38QQR with ID _j oS ranging from less than 1 ng/ml to 300 ng/ml (20 pM to 6.0 nM) (ID _5ϋ indicates the concentration of the chimeric toxin at which the protein synthesis fell by 50% when compared to the sham-treated cells). A colon adenocarcinoma cell line, Colo201 , was very responsive with an IC _5υ of 1 ng/ml. A431 epidermoid carcinoma cells were also very sensitive to the action of hIL-13-toxιn; the ID _5υ for hIL- 13-PE38QQR ranged from 6 to 10 ng/ml. A gastric carcinoma CRL1739 cell line responded moderately to the hlL- 13-toxin with an ID _5υ of 50 ng/ml. Another colon carcinoma cell line, Colo205, had a poorer response with an ID _5U of 300 ng/ml.

The cytotoxic action of hIL- 13-PE38QQR was specific as it was blocked by a 10-fold excess of hIL-13 on all cells. These data suggest that a spectrum of human cancer cells possess hIL- 13 binding sites and such cells are sensitive to hIL- 13- PE38QQR chimeric toxin. Because the hIL- 13R has been suggested to share the , subunit of the

IL-2R (Russell et al. Science 262: 1880-1883 ( 1993)), the specificity of hIL- 13- PE38QQR action on A431 and CRL1739 cells, the two cell lines with different sensitivities to the chimeric toxin was further explored The cells were treated with hlL- 13-PE38QQR with or without rhIL-2 at a concentration of 1.0 μg/ml or 10 μg/ml. The rhIL-2 did not have any blocking action on hIL-13-PE38QQR on the two cell lines, even at 10,000 fold molar excess over the chimeric toxin. These results indicate that the ceil killing by the hIL- 13-toxιn is independent ot the presence of hIL-2

IL-4, unlike IL-2, blocks the action of IL-I3-PE38QQR Native hIL-4 was added to cells which were then treated with hlL- 13-

PE38QQR. Unexpectedly, it was found that hIL-4 inhibited the cytotoxic activity of the

hIL-13-toxin. This phenomenon was seen on all the tested cell lines, including Colo201, A431 and CRL1739. To investigate the possibility that hIL- 13 and hIL-4 may compete for the same binding site, the cells were also treated with the hIL-4-based recombinant toxin, hIL-4-PE38QQR (Debinski et al. Int. J. Cancer 8: 744-748 ( 1994)). The cytotoxic action of hIL-4-PE38QQR had already been shown to be blocked by an excess of hIL-4 but not of hIL-2 (Id. ). In the present experiment hIL- 13 potently blocked the cytotoxic activity of hIL-4-PE38QQR. Also, the action of another hIL-4- based chimeric toxin, hIL-4-PE4E (Debinski et al. J. Biol. Chem. 268: 14065- 14070 (1993)), was blocked by an excess of hIL-13 on Colo201 and A431 cells. Thus, the cytotoxicity of hIL- 13-PE38QQR is blocked by an excess of hIL- 13 or hIL-4, and the cytotoxic action of hIL-4-PE38QQR is also blocked by the same two growth factors. However, IL-2 does not block the action of either chimeric toxin. These results strongly suggest that hIL-4 and hIL- 13 have affinities for a common binding site.

This conclusion was supported by the observation of one cytokine blocking the effect of a mixture of the two chimeric toxins. When A431 cells were incubated with both hIL-3- and hIL-4-PE38QQR chimeric toxins concomitantiy the cytotoxic action was preserved and additive effect was observed as expected. An excess of hIL-13 efficiently blocked the action of a mixture of the two chimeric toxins. Moreover, neither hIL-13 nor hIL-4 blocked cell killing by another mixture composed of hIL- 13-PE38QQR and TGFα-PE40, a chimeric toxin which targets the EGFR (TGFα- based chimeric toxin, TGFα-PE40) (Debinski et al. Mol Cell. Biol , 1 1 : 1751- 1753 (1991)). The same was observed on Colo201 cells.

Reciprocal blocking of chimeric toxins by IL-13 and 1L-4 is due to competition for binding sites.

The binding ability of human IL- 13 was compared to human IL-4- PE38QQR in competitive binding assays. Recombinant hIL-4-PE38QQR was labeled with ¹²⁵ I using the lactoperoxidase method as described by Debinski er al , J. Clin. Invest. 90, 405-41 1 (1992). Binding assays were performed by a standard saturation and displacement curves analysis. A431 epidermoid carcinoma cells were seeded at 10 ^" ' cells per well in a 24-well tissue culture plates at 24 h before the experiment. The plates were

placed on ice and cells were washed with ice-cold PBS without Ca+ + , Mg+ -f- in 0.2 % BSA, as described (Id ). Increasing concentrations ot hIL-13 or hIL-4-PE38QQR were added to cells and incubated 30 min prior to the addition of fixed amount of ^l25 I-hIL-4- PE38QQR (specific activity 6 2 μCi/μg protein) for 2 to 3 hours. After incubation, the cells were washed twice and lysed with 0. 1 N NaOH, and the radioactivity was counted in a γ-counter.

Human IL-4-PE38QQR competed for the binding of ^{l 5} I-hIL-4-PE38QQR to A431 cells with an apparent ID _5υ of 4 x 10 " M. In addition, hIL-13 also competed for the ^l25 I-hIL-4-PE38QQR binding site with a comparable potency to that exhibited by the chimeric protein. More extensive binding studies have shown that hIL- 13 also competes for hIL-4 binding sites on human renal carcinoma cell lines

The possibility of an influence of hIL- 13 or hIL-4 on the process ot receptor-mediated endocytosis and post-binding PE cellular toxicity steps was excluded by adding to cells: (I) native PE (PE binds to the α.-macroglobulin receptor), (n) TGFα-PE40, and (in) a recombinant immunotoxin C242rF(ab')-PE38QQR (Debinski er al Clin. Cancer Res. , 1 1015- 1022 (1995)). C242rF(ab')-PE38QQR binds a tumor- associated antigen that is a sialylated glycoprotein (Debinski er al J Clin Invest 90 405-411 (1992)) The expected cytotoxic actions of these recombinant toxins were observed and neither hIL- 13 nor hIL-4 blocked these actions on A431 and Colo205 cells

hIL-4 and hIL-I3 compete foi a common binding sire on carcinoma cells bur evoke different biological effects

Even though hIL- 13 and hIL-4 compete tor a common binding site, they induce different cellular effects Protein synthesis was inhibited in A4 1 epidermoid carcinoma cells in a dose-dependent manner by hIL-4 alone, or by a ADP-πbosylation deficient chimeric toxin containing hIL-4 (Debinski et al. , Int J. Cancer 58. 744-748 (1994)). This effect of hIL-4 or enzymatically deficient chimeric toxin can be best seen with a prolonged time of incubation (J≥.24 h) and requires concentrations of hIL-4 many fold higher than that of the active chimeric toxin in order to cause a substantial decrease in tπtium incorporation However, when A431 cells were treated with vaπous concentrations of hIL- 13, no inhibition (or stimulation) ot protein synthesis was

58 observed, even at concentrations as high as 10 μg/ml of hIL- 13 for a 72 h incubation. The same lack of response to hIL- 13 was found on renal cell carcinoma cells PM-RCC Thus, while hIL- 13 and hIL-4 may possess a common binding site, they appear to transduce differently in carcinoma cells expressing this common site, such as A431 and PM-RCC cells.

Example 6 TIJ-13 Inhihits Growth of Human Renal Cell Carcinoma Cells Independently of the

PI 40 II.-4 Receptor Chain Since human renal cell carcinoma cells (RCC) express a large number of intermediate to high affinity IL- 13 receptors, the effect of IL- 1 on in vitro growth of RCC cells was determined. The interaction between the IL- 13 receptor and the IL-4 receptor was evaluated by examining the effect of antι-IL-4 and antι-IL-4R antibodies on IL-13 binding to RCC cells and the IL- 13 modulation of RCC cell proliferation.

Inhibition of RCC cell growth by IL-I3.

Renal cell carcinoma cells - WS-RCC and PM-RCC were derived as described previously (Obiπ et al , J. Clin. Invest. , supra) and maintained in culture medium (CM) consisting of DMEM with 4.5 g/L glucose supplemented with 10% fetal bovine serum (FBS), glutamine (2 mM), HEPES buffer ( 10 mM), penicillin ( 100 U/ml) and streptomycin (100 μg/ml).

For proliferation assays, RCC cells were harvested, washed and resuspended in CM in which the FBS content was reduced to 0.5% Ten thousand cells were plated in each well of a 96-well microtiter tissue culture plate and cultured overnight at 37°C in a 5 % C0 ₂ environment. IL- 13 and/or IL-4 (0- 1000 ng/ml) were added and incubation continued for an additional 72 h. Some cultures were concurrently treated with anti-IL-4 or anti-IL-4R antibody (1-10 μg/ml). [ H]-thymιdιne (1 μCi/well) was added for the final 20 h of incubation. At the end of the incubation, cells were detached with trypsin or by a rapid freeze/thaw cycle and harvested unto a glass fiber filter-mat with a cell harvester (Skatron, Lier, Norway), f H]-thymιdιne uptake was determined with a Betaplate sc tilation counter (LKB, Gaithersburg, MD)

IL-13 inhibited cellular proliferation by up to 50% in a concentration dependent manner in WS-RCC and PM-RCC cell lines. The PM-RCC cell line was more sensitive to IL-13 since 0. 1 - 1 ng/ml IL- 13 caused a maximum inhibitory effect. The other cell line, WS-RCC required as much as 100 ng/ml of IL- 13 for maximum effect. In addition, IL-13 at concentration of 10 ng/ml reduced proliferation of HL-

RCC cells by 33%. Higher concentrations of IL- 13 (up to 2000 ng/ml) did not have additional growth inhibitory effect. This growth inhibitory effect of IL- 13 is similar to that observed with IL-4 On human RCC cells.

In order to examine the effect of IL- 13 on the viability of RCC cells, the cells were cultured with IL- 13 (0 - 100 ng/ml) at 5 x 10 ⁴ /MI in 12-welI tissue culture plates. After 72 h, the cells were harvested with trypsm/versene, washed and diluted in trypan blue for cell counts. Viability was determined by trypan blue exclusion. In control cultures, the viability (mean±SD of quadruplicate samples) was 95 ± 10% while the viability in cultures treated with 10 or 100 ng/ml IL- 13 was 92.5 ±9.6 and 93± 8.9 respectively. Thus, IL-13 did not have direct cytotoxic effect on RCC cells.

Since IL- 13 competes for IL-4 binding and a mutated form of IL-4 inhibited IL-13 and IL-4 effects (Zurawski et al , EMBO J. , 12: 2663 ( 1993)), the ability of anti-IL-4 or antι-IL-4R antibody to block both IL-4 and IL- 13 growth inhibitory effects was determined. For this experiment, WS-RCC cells were treated with IL-13 or IL-4 alone, or in the presence of a neutralizing polyclonal antibody to hIL-4 or a monoclonal antibody to IL-4R (M57). This approach was chosen because a suitable anti-hlL-13 was not readily available.

[ ³ H]-thymidine uptake was significantly inhibited (p < 0.05) in IL-13-treated cultures (1913 + 364 cpm in treated vs 3222+458 cpm in control) and in IL-4 treated cultures (2262±210 cpm in treated vs 3222±458 cpm in control). While the IL-4-mediated inhibition of proliferation was abrogated by a polyclonal antι-IL-4 antibody, the inhibitory effect of IL- 13 was not affected by the addition of antι-IL-4 antibody. Furthermore, the anti-prohferative effect of IL-4 was also abrogated by M57, a monoclonal antibody against IL-4R, but the antiprohferative effect of IL- 13 was not affected by this antibody.

When WS-RCC cells were treated with a combination of IL-4 and IL- 13, the resulting inhibition of cellular proliferation was not significantly different from that seen in cultures treated with either cytokine alone. Thus, although IL-4 and IL- 13 exert a similar effect on RCC cell growth, their actions could not be potentiated by using the two cytokines together.

Inhibition of RCC colony formation by IL-I3.

To confirm the observed IL- 13 mediated inhibition of RCC tumor cell proliferation, a colony formation assay was used to evaluate the effect of IL- 13 on RCC cell growth. Five hundred RCC cells were plated in triplicate 100 cm ² tissue culture-treated petπ dishes and treated with various concentrations of IL- 13 For comparative purposes, RCC cells were also similarly treated with IL-4 After a 10-day culture period, the percentages of colonies formed in control and cytokine treated groups were compared. IL-13 inhibited colony formation in PM and WS RCC cells in a concentration dependent manner A maximum of 34% reduction in colony formation was observed in WS-RCC cells. In repeated experiments, the maximum inhibition observed in PM-RCC cells ranged from 13 - 32% The kinetics ot the inhibition ot colony formation in WS-RCC cells was similar to that observed in PM-RCC cells. By compaπson, IL-4 inhibited colony formation in both cell lines to the same extent as did IL-13. However, PM-RCC cells appeared to be slightly more sensitive to the 1L-4 effect than WS-RCC cells.

Effecr of anιι-IL-4R antibody on IL-I3 binding. As explained above, on human RCC cells, IL- 13 compete for the binding of ¹²⁵ I-IL-4 but IL-4 does not compete for the binding of ^l2S I-IL- 13. In order to understand the mechanism underlying the inhibition ot IL-4 binding by IL- 13 and to evaluate the fidelity of ligand binding by IL- 13R, the effect of antι-IL-4R antibody on '"l-IL-13 binding to PM-RCC cells, which express both IL-4R and IL- 13R, was examined. As a control, the effect of this antibody on ^l2<i l -IL-4 binding to PM-RCC cells was also tested.

Recombinant human IL-4 and IL- 13 were labeled with ¹² I (Amersham Coφ.) by using the IODO-GEN reagent (Pierce Chem. Co.) according to the manufacturer's instructions. Specific activity ranged from 20 to 80 μCi/μg for ^l25 IL-4 and 80 to 120 μCi/μg for ¹²ⁱ IL- 13. About 1 x 10 ⁶ cells were incubated with radio labeled ligand (0.64 nM) in a buffered medium alone or in the presence of excess cytokine ( 128 nM); monoclonal (M57) or polyclonal (P2, P3, P7) rabbit antibodies raised against human IL-4R. The antibodies were used at a final dilution of 1 :64. The incubation was done at 4°C for 2 h in a shaking water bath. Cell bound radio-hgand was separated from free by centnfugation through an oil gradient and bound radioactivity determined in a gamma counter.

Both ¹²⁵ I-IL- 13 and ^l2S I-IL-4 specifically bound to PM-RCC cells (181,650+3, 182 cpm and 9,263 ±576 cpm respectively). Unlabeled IL-13 competed well for ¹²⁵ I-IL-13 binding, however, neither IL-4 nor any of three different polyclonal antibodies to IL-4R competed for the binding of ^l25 I-IL-13 on PM-RCC cells. Similarly, a monoclonal antibody to IL-4R (M57) did not block the binding of '"l-IL- B to

PM-RCC cells. In contrast, IL-4, IL- 13 and anti-IL-4R antibody (P7) all competed for ^l25 I-IL-4 binding on these cells.

This Example demonstrates that IL- 13 inhibits the proliferation of human RCC cells in a concentration dependent manner. A maximum of 50% growth inhibition was observed and this growth inhibitory effect of IL- 13 was supported by the results of a colony formation assay. It is noteworthy that the same concentration range of IL- 13 inhibited colony formation in both RCC cell lines. Although a similar magnitude of growth inhibition has been reported tor IL-4, this is the first report of a direct anti-tumor effect of IL-13 on RCC cells. Furthermore, inhibitory effects of IL-4 on colony formation in RCC cells have not been previously reported

The antitumor effects of IL- 13 were independent of IL-4 and did not involve IL-4R. This is evidenced by the fact that polycional or monoclonal antibodies to IL-4 or to the 140 kDa subunit of IL-4R had no effect on the growth inhibitory effect of IL-13. As was previously observed with IL-4, the inhibitory effect of IL-13 on RCC growth was cytostatic rather than cytotoxic since the viability in cells cultured with 10 or

100 ng/ml IL- 13 was similar to that observed in control cultures after 72 h treatment

62

Recently, 1L-13 was shown to directly inhibit the proliferation ot normal and leukemic B precursor cells in vitro by 30% (Renard et al , Blood, 84: 2253-(1994)) This growth inhibitory effect of IL-13 was abrogated by an antibody to the 140 kDa subunit of IL-4R. Similarly, the growth stimulatory effect of IL- 13 on TF-1 cells was also shown to be blocked by an antibody to IL-4R (e.g , Tony et al. , Europ. J

Biochem. , 225: 659 (1994)). However, in this study, none of 3 different antibodies to IL-4R blocked the growth inhibitory effect of IL- 13. These contrasting findings may suggest that the antibodies used in this study and those used by others are directed at different epitopes on the IL-4R protein. An alternative explanation, which we favor, is that IL-13R on RCC are structurally different from those expressed on lymphoid cells

Structural differences between IL-4R expressed on RCC and those expressed on lymphoid cells have been identified These include the absence ot the common gamma chain of the receptors for IL-2, 4, 7, 9, and 15 in tumor cell IL-4R, although this chain is present tn IL-4R of immune cells (Obin et al Oncol. Res , 6 419 (1994)).

Previous studies have demonstrated that antibodies to IL-4R block cellular responsiveness to IL- 13 (Tony et al , Euiop. J. Biochem. , 225: 659 (1994)) However, the effect of these antibodies on the binding of ¹²⁵ I-1L- 13 to the cells was not investigated. We report here that the binding of radio-labeled IL-13 to its receptors on RCC cells could not be blocked by a polyclonal antibody to IL-4R which did block the binding of radio-labeled IL-4 to its receptors. These data suggest that in RCC cells. IL-13 interaction with its receptor does not involve the 140 kDa subunit of IL-4R and IL-13 effects are probably mediated by receptors that are not shared with IL-4.

Nevertheless, results from the above described Examples do suggest some common element(s) between IL-4R and IL- I 3R For example, 1L-1 binds to a ^" 70 kDa protein and competes for IL-4 binding but IL-4 did does compete for IL- 13 binding in RCC cells. In addition, IL-4 cross links to a ^" 70 kDa protein in addition to its primary 140 kDa binding protein Taken together, these data suggest that the -70 kDa protein binds both IL-13 and IL-4 This indicates that the 70 kDa protein may be a homodimer in which one of the constituents binds IL- 13 alone while the other binds bot IL-13 and IL-4. The data further suggest that because it binds to both putative

components of the ^" 70 kDa protein, IL- 13 has a higher binding affinity to this protein than does IL-4 which appears to bind, at most, one component of the IL-13 receptor. Such an arrangement explains the finding that IL- 13 competes for ^l2<i I-IL-4 binding while IL-4 does not compete for ^l25 I-IL- 13 binding on these cells. Finally, since antibody to IL-4R did not block IL-13 binding, and ^l25 I-IL- 13 cross linking to the pl40 form of the

IL-4R was not detected, in RCC cells, IL-13 does not appear to utilize the 140 kDa IL-4 binding subunit.

The observation that the combination of IL-4 and IL- 13 does not inhibit RCC cell proliferation any better than either cytokine alone suggests that the anti-proliferative effects of IL-4 and IL- 13 are mediated through a common receptor subunit or common signaling pathway. This is consistent with the notion of a shared receptor or receptor component for the two cytokines and the observation that both IL- 13 and IL-4 phosphorylate a member of the Janus family of kinases (JAK 1) as well as the 140 kDa subunit of IL-4R and activate the same signal transducer and activator of transcription (STAT 6) proteins in different cell types.

In summary, IL- 13, like IL-4 directly inhibits RCC proliferation in vitro. The IL-13 effect is independent of IL-4 since anti-IL-4R antibody did not inhibit IL- 13 binding to its receptor and anti-IL-4R antibody did not inhibit the IL- 13 effect on RCC cells. These findings suggest that IL- 13R directed chimeric molecules are particularly useful for the management of RCC.

Example 7 Targeting of Interleukin- 13 Receptor on Human Renal Cell Carcinoma Cells by

Recombinant IL-13-PE Cytotoxins Cytotoxicity of IL-l 3-toxin fusion protein.

The cytotoxic activity of IL4-toxins was tested as described above. Typically, 10 ⁴ RCC tumor cells or other cells were cultured in leucine-free medium with or without various concentrations of IL-toxin for 20-22 hours at 37°C. Then 1 μCi of [ ^J H]-Leucine (NEN Research Products, Wilmington, Deleware, USA) was added to each well and incubated for an additional 4 hours. Cells were harvested and radioactivity

incorporated into cells was measured by a Beta plate counter (Wallac-LKB, Gaithersburg, Maryland, USA).

Four primary cell cultures (PM-RCC, WS-RCC, MA-RCC & HL-RCC) and 1 long term culture (RC-2) of RCC cell lines were tested because of the large number of IL-13 receptors expressed by human RCC cells (see Example 1). RCC cells were sensitive to the cytotoxic activity of IL13-toxin with IC _W ranging from as low as 0.03 ng/ml to 350 ng/ml ( < 2 fM to 1 nM) (Table 2). All four primary cultures of RCC cells generated in our laboratory ( 18) seemed to be more sensitive to IL13-PE38QQR compared to long term RCC cell line (CAKI- 1 ). The cytotoxic activity of lL13-toxin was specific and mediated through IL- 13R, because excess IL- 13 neutralized the cytotoxic activity of ILl 3-toxin. Thus, RCC cells are killed by IL13-PE38QQR at uniquely low concentrations of the chimeric protein (1L13-PE38QQR (474 am o acid protein) is composed of IL- 13 ( 1 14 N-terminal amino acids) and domain II and domain III of PE molecule (Debinski et al , J. Biol. Chem. , 270: 16775 ( 1995)). Table 2. Cytotoxic activity of IL13-PE38QQR on human RCC tumor cell lines.

Tumors IC ₃₀ (ng/ml)' IL- 13 binding Reference mean ± SD sites/cell No.

HL-RCC 0.03, < 0. 1 150,000 13

PM-RCC 0.090 ± 0.01 26,500 13

MA-RCC 0.340 + . 15 5,000 13

WS-RCC 17.500 ± 3.50 2,000 13

CAKI- 1 350.000" < 100 -'

"IC ₅₀ , the concentration of IL 13-toxin at which 50% inhibition of protein synthesis is observed compared to untreated cells and was determined as described under "methods" . The mean IC _5ϋ for individual tumors is shown and was determined from 2-5 experiments for four RCC tumor cell lines. ^b Single experiment performed in quadruplicate using 5 different concentration of

IL13-toxin. ^c current data

Correlation between IL-I3R eψiession and sensitivity to ILI3-toxιn

As described above, the primary RCC cell lines, such as PM-RCC, WS- RCC, HL-RCC, and MA-RCC expressed varied numbers of high- to intermediate- affinity IL- 13R. However, IL 13 binding characteristics on CA I- 1 RCC cell line was not determined. IL-13 binding studies were therefore performed on these RCC cells utilizing [ ^,25 I]-IL-13.

IL- 13 was lodinated with IODOGEN reagent (Pierce, Rockford, Illinois, USA) according to manufacturer's instructions. The specific activity of radio-labeled IL- 13 ranged between 44 to 128 μCi/μg The IL- 13 binding assay was performed by as descnbed above (see Example 1 ) Briefly, RCC tumor cells were harvested after brief incubation with versene (Biowhittaker), washed three times in Hanks balanced salt solution and resuspended in binding buffer (RPMI 1640 plus 1 mM HEPES and 0.2 % human serum albumin). For IL- 13 displacement assay, RCC ( l x l 0 ⁶ / 100 μ!) cells were incubated at 4°C with ^{I S} I-1L- 13 ( 100-200 pM) with or without increasing concentrations of unlabeled IL- 13 or IL13-PE38QQR Following a 2 h incubation, cell bound radio- ligand was separated from unbound by centnfugation through a phthalate oil gradient and radioactivity determined with a gamma counter (Wallac)

CAKI- 1 RCC cell line did not bind radiolabeled IL- 13 well and only expressed < 100 IL- 13 binding sites/cell (Table 1) The sensitivity of these cell lines to IL13-toxιn also varied depending on the number of IL- 13 binding sites per cell CAKI- 1 RCC cell line expressed the least number ot IL- 13 binding sites and were least sensitive to IL13-toxιn. In contrast, HL-RCC cells were extremely sensitive and expressed 150,000 IL-13 binding sites/cell.

In vivo passage of MA-RCC does not decrease sensitivity to lLI3-toxιn

In order to determine the antitumor activity of IL13-toxιn against human RCC, human RCC cells were grown as subcutaneous tumors in nude mice irradiated (300 rads) nude mice and in SCID mice However, these RCC cells did not grow consistently in any of these immimoincompetent mice In some cases tumors did grow very slowly but became centrally necrotic with a white rim ot viable RCC cells

Therefore, antitumor activity of IL13 toxin was not evaluated in vivo However, MA-RCC were passaged in nude mice and the passaged tumors were used to prepare single cell suspensions These cells did grow in tissue culture and after 1-3 passages, their sensitivity to IL13-toxιn was determined MA-RCC were very sensitive to IL13-toxιn and passaging of these RCC cells in vivo twice did not decrease their sensitivity These data suggest that IL- 13R levels do not change by in vivo passaging of RCC tumor cells

lL13-toxιn is not cytotoxic to immune cells, monocytes, bone marrow-derived cells, and Buikitt's lymphoma cells

The cytotoxic activity of IL13-PE38QQR was also examined on PHA- activated T cells, a CD4+ T cell lymphoma line (H9), normal bone marrow cells, EBV- transformed B cell line, 2 Burkitt's lymphoma cell lines and a premonocytic cell line (U937). As shown above in Example 1 , PHA-activated T cells, H9 cells, and U937 cells did not express detectable numbers ot IL-13R Consistent with these observations,

IL13-PE38QQR was not cytotoxic to any ot these cell types EBV-transformed B cell line did express about 300 IL 13-bιnd g sites/cell, however, IL13-toxιn was not cytotoxic to them Although IL- 13R expression was not tested on human bone marrow cells or Burkitt's lymphoma cell lines, based on their msensitivity to IL13-toxιn, it is expected that these cells also do not express IL- I3R or express a low number ot these receptors.

Clonogenic assay

The antitumor activity of IL13-PE38QQR was also tested by a colony- forming assay Five hundred PM-RCC cells were plated in 100 mm petπ dishes and the next day triplicate plates received IL- 13 (20 ng/ml), IL13-PE38QQR (50 ng/ml) or control medium. The cells were cultured tor 10 days at 37°C in a CO, incubator Media was then removed and colonies were fixed and stained with 0 25 % crystal violet in alcohol. Colonies containing 50 or more cells were scored The surviving traction was calculated as the ratio ot the number of colonies formed in treated and untreated cells and presented as percent survival

Human PM-RCC cells formed colonies when 500 cells were cultured in petri dishes. Using this number of cells, PM-RCC cells formed 175 colonies with a clonogenic efficiency of 35 % . When these cells were treated with ILI 3-PE38QQR for 10 days, only 32 colonies were formed (Table 3). However, 123 or 175 colonies were formed when cells were treated with recombinant IL-13 or media alone respectively.

Table 3. Effects of IL- 13 and IL-13-PE38QQR on PM-RCC cells by clonogenic assav.

No. Colonies ± SD % Surviving fraction

PM RCC:

Control 175 + 5 100

IL13-PE38QQR 32 ± 4 18

IL-13 123 ± 3 70

HL RCC:

Control 348 ± 9 100

IL13-PE38QQR (5 i ig/ l ) 4 ± 0.8 1

IL13-PE38QQR ( 15 ng/ml ) 1 ± 1 0.3

IL-13 232 ± 12 67

IL-4 does not block the cytotoxic activity ofILI3-PE38QQR on RCC cells.

IL- 13 competed for the binding sites of IL-4 while IL-4 did not compete for the binding site of IL- 13. However, in other cancer cell types IL-4 neutralized the cytotoxicity mediated by IL13-PE38QQR. The ability of IL-4 to neutralize the cytotoxicity of IL13-toxin on RCC cells was therefore tested. Only IL- 13 blocked the cytotoxicity of IL13-toxin, while IL-4 did not block this cytotoxicity in all three RCC cell lines tested.

Binding affinity of ILI 3-toxin on human RCC cells.

The binding affinity of IL13-PE38QQR to IL- 13R was then examined. HL-RCC or PM-RCC cells were utilized for this purpose. These cells were incubated

with a saturating concentration of radiolabeled IL- 13 in the absence or presence of vanous concentrations of IL- 13 or IL13-PE38QQR In HL-RCC cells the IC ₅₀ (the protein concentration at which 50% displacement of [ ^l25 I]-IL- 13 binding is observed) tor native IL-13 was ^" 20 x 10 M, compared to ^" 180 x 10 " M with IL13-PE38QQR. Thus IL13-toxιn bound to IL-13R with about 8- 10 fold lower affinity compared to IL- 13

The foregoing experiments show that an IL- 13 based cytotoxin, IL13- PE38QQR, is highly cytotoxic to human renal cell carcinoma cells. The IC _5U in RCC cell lines ranged from less than 0.03 ng/ml to 350 ng/ml. The cytotoxicity of the IL13-toxιn was specific and mediated through IL- 13R because excess IL- 13 neutralized the cell killing activity of IL13-PE38QQR. These results corroborate with the data generated in a clonogenic assay that demonstrate a significant inhibition of colony formation by IL 13- toxin.

Resting human cells including non-activated T cell line (H9), EBV- transformed B cell line, and promonocytic (U937) cell lines were not sensitive to the cytotoxic effect of IL13-toxιn. Similarly, PHA-activated human T cells and cells obtained from normal bone marrow biopsy were also insensitive to the cytotoxic effect of IL13-PE38QQR. It has previously been reported that hematologic progenitor cell lines and fresh human bone marrow cells express low numbers of IL-4 receptors (e ^→ → , Lowenthal et al. J Immunol , 140: 456 ( 1988)). However, IL- 13R expression on these cells has not been determined A recent study reported that IL- 13 has a direct regulatory role in the proliferation and differentiation of primitive murine hematopoiettc progenitor cells (Jacobsen et al J. Exp. Mec , 180: 75 ( 1994)) indicating expression of some level of IL-13R on these cells. However, the example shows that IL13-toxιn was not cytotoxic to fresh bone marrow derived cells indicating that progenitor cells probably express insufficient amount of IL-13R or receptors on these cells are not susceptible to the cytotoxic action of IL 13-toxιn

It was shown above that IL- 13 competes for the binding of IL-4 while IL- 4 does not compete for the binding of IL- 13 on RCC cells (Example 2). Similar to these results, the data in this example show that IL-4 does not neutralize the cytotoxic ef fect of IL13-PE38QQR

It has been previously demonstrated that IL4 based cytotoxin (IL4-PE4E) is highly cytotoxic to human RCC cells. A comparison was not made between IL13- PE38QQR and IL4-PE4E because the PE portion in these two chimeric proteins is different. However, both IL- I3 and IL-4 competed with the cytotoxicity of IL4-toxιn Similarly, a mutant IL-4 protein blocked the proliferative response generated by IL-4 and IL-13. These data suggest that the receptors for IL- 13 and IL-4 share a component The data on RCC cells showed that [ ^l2, I]-IL- 13 crosshnked to one major protein of ^" 70kDa, which appeared to be similar in size to the smaller of the two subunits of IL-4R. The competition of IL- 13 for the binding sites of IL-4, suggests that the ^" 70 kDa protein is shared between these two receptors Also, IL-4 and IL- 13 compete reciprocally to an internalized receptor form on some carcinoma cell lines Recent data demonstrate that both IL-4 and IL- 13 caused the phosphorylation of 140 kDa IL-4 binding protein In addition, antibody to 140 kDa IL-4 binding protein blocked the effects of IL-13 on B cells. While these studies, suggest that the 140 kDa IL-4 binding protein may be shared between these two cytokine receptors, crosslinking of [ ^{l <i} I]-IL- 13 to the 140 kDa protein was not observed even though [ ^12, I]-IL-4 crosshnked to this protein. These data suggest that either the 140 kDa IL-4 binding protem does not share a chain with IL- 13R or the 140 kDa protein is a non-IL- 13 binding component of the IL- 13R system which is why IL-4 does not compete for the binding of IL- 13 It is of interest to note that IL13-toxιn binds to IL- 13 receptor with a lower affinity compared to that ot IL- 13 Since PE molecule was attached to the C- terminus of the IL- 13 molecule, these data suggest that, similar to IL-4, IL- 13 may interact with its receptor predominantly through C-terminal end residues In addition, these data also suggest that a chimeric IL13 toxin molecule in which the toxin moiety is attached at a site away from the C-terminus residues should be more cytotoxic to cancer cells.

In summary, these results indicate that IL13-toxιn IL 13-PE38QQR is highly cytotoxic to human RCC cells which express high numbers of IL- 13R Because resting or activated immune cells or bone marrow cells are not sensitive to IL13-toxm, the data indicate that this toxin is useful tor the treatment of RCC without being cytotoxic to normal immune cells

Example 8 Human Glioma Cells Overexpress IL-13 Receptors and Are Extremely Sensitive to

IL-13PE Chimeric Proteins

In order to evaluate the efficacy of the chimeric immunotoxins of this invention on brain tumors, cytotoxicity (as evaluated by inhibition of protein synthesis) and competitive inhibition assays were performed on a number of brain tumor cell lines as described below.

Protein synthesis inhibition as say The cytotoxic activity of chimeric toxins (e.g , hIL 13-PE38QQR) was tested on brain tumor cell lines This group of cells is represented by human gliomas and includes U-373 MG, DBTRG-05 MG, A- 172, Hs 683, U-25 1 MG, T-98G , SNB- 19, and SW-1088, and also one human neuroblastoma SK-N-MC cell line. The majority of cell lines was obtained from the ATCC and they were maintained under conditions recommended by the ATCC. The SNB- 19 ceil line was obtained from National Cancer Institute/Frederick Cancer Research Facility, DCT tumor repository. Both SNB- 19 and SW-1088 cell lines are of neuroglial origins.

Usually about I x 10 ⁴ cells/well were plated in a 24-well tissue culture plate in 1 ml of medium and vaπous concentrations of chimeric immunotoxin were diluted in 0.1 % bovine serum albumin (BSA)/phosphate-buffered saline (PBS) and 25 μl of each dilution was added to 1 ml of cell culture medium. After 20 hr incubation with the immunotoxins, [ ³ H]-leucιne was added to the cells for 3-5 hr, and the cell-associated radioactivity was measured using a beta counter.

For blocking studies (i) recombinant h I L 13 (rhILl 3) or (n) rhIL4 was added to cells for 20-30 min before the addition of chimeric toxins (CTs) Data were obtained from the average of duplicates and the assays were repeated several times.

The cancer cells were sensitive to hIL13-PE38QQR with IC^s ranging from less than 0. 1 ng/ml to more than 300 ng/ml (2 pM to 6.0 nM). (The IC _Sυ was calculated as the immunotoxin toxin concentration that causes 50% inhibition of tπtiated leucine incorporation by the test cell line.) The cell lines fell into roughly three groups according to their responsiveness to the chimeπc toxin The first group consisting ot U-

373 MG, U-251 MG, SNB- 19, and A- 172 was killed by hIL13-PE38QQR at the lowest concentrations with IC _5u s ranging from less than 0. 1 to 0.5 ng/ml (2 to lOpM). In particular, SNB-19 and A- 172 had IC _5υ s of about 0.05 ng/ml. The second group of glioma cell lines composed of DBTRG MG and Hs-683 cells also responded very well to the hIL13-toxιn with IC _5u s in a range of 1 - 10 ng/ml (20-200 pM). The third group of glioma cell lines represented by T-98G and SW 1088 had poorer responses with IC ₎ s of 300 and > 1000 ng/ml, respectively. The only human cancer cell line of neural origin tested, the SK-N-MC neuroblastoma cell line, responded relatively poor to the chimeric toxin. The cytotoxic action of hIL13-PE38QQR was specific as it was blocked by a 10- or 100-fold excess of I 13 on the studied cells. These data indicate that most of the human glioma cancer cells examined possess hIL 13 binding sites and such cells are extremely sensitive to hIL 1 -PE38QQR.

Cytotoxic activities of other cytokine-based chimeric proteins in glioma cells.

The cytotoxic action of hIL13-PE38QQR was compared to that of chimeπc toxins containing other interleukins, such as hIL4 or hIL6. It has already been shown that some glioma cell lines can be killed by hIL4-PE4E with IC _su s exceeding 10 ng/ml (Pun et al. Int. J. Cancer, 58: 574-581 ( 1994)). HIL13-PE38QQR was cytotoxic to U-251 MG, U-373 MG and DBTRG MG cell lines with IC _Sϋ s much below 10 ng/ml. The cytotoxin hIL4-PE38QQR, a hIL4-based chimeπc toxin resembling hIL13-PE38QQR, killed glioma cell lines, but at a concentration ranging from a factor of 10 to almost a factor of 1000 higher than that of hIL13-based toxin.

The IC _5ϋ s for hIL4-PE38QQR were higher than that seen with the hIL4- PE4E variant of the chimeric toxin (Debinski, et al. J. Biol. Chem. , 268: 14065- 14070

(1993), Puri et al Int. J. Cancer, 58: 574-581 ( 1994)) which is consistent with observations made with other growth tactor-based chimeric proteins (Siegall et al. Cancer Res. , 51 : 2831-2836 ( 1991 )). Interestingly, hIL6-PE40 was also active on some human glioma cells and its activity was similar to that of the hIL4-toxιn or better. However, hIL6-PE40 was still less active than the hIL13-based chimeπc protein. These results show that human glioma cell lines are extremely sensitive to hlL13-PE38QQR

and the cytotoxic activity of the IL13 directed cytotoxin is considerably better than that of other interleukin-based chimeric toxins.

Comperirion of hIL4for the cytotoxicity of hIL- 13-PE38QQR. The previous examples demonstrated that the action of hIL13-PE38QQR on several solid tumor cell lines is hIL13- and hIL4-specιfic, i.e. , it can be blocked by these two cytokines but not by IL2. However, it was also observed that hIL4 cannot compete for hIL13 binding sites (Obin et al. J. Biol Chem. , 270' 8797-8804 ( 1995)) and it cannot block the cytotoxic action of the hIL13-based chimeric protein on some other cancer cell lines. Thus, the ability of hIL4 to block the IL 13-toxιn cytotoxin in glial cells was determined.

The hIL4 cytokine was ineffective in preventing the cytotoxicity of hIL 13- PE38QQR on both U-251 MG and U-373 MG cell lines. On the other hand, hIL13 did block the cytotoxic activity of I.IL4-PE38QQR. Thus, the cytotoxicity of hIL 13- PE38QQR was blocked by an excess of hIL13 but not of hIL4, and the cytotoxic action of hIL4-PE38QQR was blocked by hIL 13

Human glioma cell lines express a number of leceptors for ILJ3.

To verify that the cytotoxic activity of hIL13-PE38QQR is specific and mediated by hIL13 receptors, competitive binding assays were performed. Recombinant hIL13 was labeled with ^l25 I (Amersham Corp.) by using the IODO-GEN reagent (Pierce) according to the manufacturer's instructions, as previously described (Obin er al. J Biol Chem. , 270: 8797-8804 ( 1995)) The specific activity of the radiolabeled cytokines was estimated to range from 20 to 100 μCi/μg of protein. For binding experiments, typically 1 x 10 ⁶ tumor cells were incubated at 4°C for 2 h with I-hIL 13

(100 pM) with or without increasing concentrations (up to 500 nM) of unlabeled cytokine. The data were analyzed with the LIGAND program (Munson, ef al , Analv Biochem. 107: 220-239 ( 1980)) to determine receptor number and binding affinity. Unlabeled hIL13 competed for the binding of ^12S I-hlL13 to U-373 MG cells efficiently. The Scatchard plot analyses of displacement experiments revealed one single binding site for hIL13 of intermediate affinity (K _d = 1 8 nM) There were around

16,000 binding sites for hlL13 on the U-373 MG cell line. The presence of hIL13 receptors in other human glioma cell lines was also evaluated. As seen in Table 4, the glioma cells had receptors for h I L 13 ranging from 500 to 30,000 molecules per cell. The hIL-13Rs expressed in human glioma cells are of intermediate affinity with K _d s ranging from 1 to 2 nM. It is noteworthy that four out of five cell lines studied had very Table 4. Human IL-13 binding to human glioma cells.

Cell Line Binding Sites ^* Kd hIL- 13 -PE38QQR molecules/cell ( % CV) (nM) IC ₅₍ i (ng/ml)

A- 172 22,600 ( 15) 1 .6 < 1

U-251 MG 28,000 ( 12) 2. 1 < 1

SNB-19 17,580 ( 19) 1 .4 < 1

T-98G 549 (37) 1.0 200

U-373 MG 16,400 ( 14) 1.8 < 1

*1 x 10 ⁶ cells were incubated with 1251-hIL- 13 (100 pM) with or without increasing concentrations (up to 500 nM) of unlabeled hIL- 13. Displacement curves and scatchard analyses were generated from the binding data using the LIGAND program (Munson er al . Analy. Biochem. , 107: 220-239 ( 1980)).

high numbers of hIL- 13R, i.e. , above 15,000 molecules per cell. The very same cell lines were also the most responsive to the action of hIL- l 3-PE38QQR (Table 1 ). The T- 98 G cell line was poorly responsive to the hIL- 13-toxin ³ and was found to have only around 500 hIL- 13 binding sites per cell (Table 1). Thus, specific hIL- 13Rs are expressed in glioma cell lines and they mediate the cytotoxicity of hIL- 13-PE38QQR. These experiments establish that human glioma cell lines express large numbers of the receptor for the cytokine, IL 13 and that it is possible to target hIL- 13R with a chimeric toxin composed of the IL13 interleukin and a derivative of PE (e.g. ,

PE38QQR). The hIL13-PE38QQR toxin is extremely active on several glioma cell lines and most of these cell lines are killed at concentrations below 1 ng/ml ( < 20 pM).

The action of hIL 13-PE38QQR on glioma cells appears hIL l3-specifιc because (i) hIL13 alone blocks the cytotoxicity of the chimeric toxin on all of the studied cell lines, and (ii) rhIL4 does not prevent the cytotoxic action of hIL13-PE38QQR on U-251 MG and U-373 MG e g>l'ioma cells. The latter observation is different from the one made

on adenocarcinomas of the skin, stomach and colon origins (Debinski et al , J. Biol Chem. , 270: 16775- 16780 ( 1995)) The action of IL13-PE38QQR was blocked efficiently by rhIL4 on these adenocarcinoma cell lines.

Receptors for IL4 and IL13 are complex and they have some common features detected in various systems, such as normal or malignant human cells.

However, the U-251 MG cell line does not bind rhIL4 in a standard binding assay at 4°C while the number of hIL I3 binding sites is high on these cells This phenomenon most probably explains why rhIL4 does not block the action of hIL13-PE38QQR on these cells. Thus, the receptors for hIL13 and hIL4 in glioma cells are different from those found in several solid tumor cell lines.

The hIL13-PE38QQR cytotoxin is considerably more active on glioma cell lines than the comparable IL4-based chimeric toxin This difference in cytotoxicity is presumably due to the difference in numbers of IL 1 and IL4 molecules that can be bound by glioma cells. Many human glioma cells bind more than 15,000 and up to 30,000 molecules of IL13 per cell while these cells bind from less than 3,000 to very few molecules of IL4 per cell. Interestingly, some human glioma cells can also be killed by a chimeric toxin containing hIL6 (Siegall et al , Cancel Res. , 51: 2831 -2836 ( 1991 )) However, the potency of 1.IL6-PE40 chimeric protein is lower from that of hILl 3- PE38QQR. Example 9

Chimeric Toxins Having Increased Cytotoxicity Two chimeπc toxins were produced that had higher specific toxicities than IL-13-PE38QQR. The first cytotoxin was an IL- 13-PE4E toxin where PE4E is a "full length" PE with a mutated and inactive native binding domain where amino acids 57, 246, 247, and 249 are all replaced by glutamates.

The second fusion protem was circularly permuted human IL- 1 (cpIL- 13) fused to PE38QQR In particular, the circularly permuted IL- 13 was produced by selecting the methionme (Met) at position 44 of human IL- 13 (hIL- 13), just at the beginning of the putative second alpha-helix of hIL-13, as the "new" N-terminal end ot the cytjkine. The "old" N-, and C-termmi were connected by a short peptide having the sequence Gly-GLy-Ser-Gly. The circularly permuted IL- 13 (cphIL- 1 ) was cloned in a

way that the "new" C-teπmnus of cphIL- 13 (Gly-43 in a wild-type cytokine) was fused to the N-terminal Gly of PE38QQR.

The plasmid encoding cphIL- l 3-PE38QQR was constructed as follows Plasmid phuIL13, encoding the 1 14 am o acids of hIL13 (see, e.g. , Debinski et al. , J. Biol Chem. 270: 16775- 16780 ( 1995)) served as a template for amplification of two separate fragments of hIL13; a fragment consisting of amino acids 1-43 and a fragment consisting of amino acids 44-1 14 or hIL- 13 respectively. Both hIL13 1 -43 and hIL 13 44-114 were produced by PCR-amplification using two set of primers, primers cpl/cp2 and cp3/cp4, respectively (see Table 5, Sequence ID Nos. 1 , 2, 3, and 4 respectively) Pnmers cpl and cp4 introduced a new cloning site for Bam HI restriction endonuclease: primer cp2 encoded for a Hind III site and primer cp3 for Nde I restriction site. PCR-amplified cDNAs encoding for hIL13 1 -43 ( 130 base-long) was cut with Bam HI and Hind III enzymes, and hILl 3 44- 1 14 (210 base-long) was cut with Nde 1 and Bam HI. These two fragments of DNA were ligated in a three- fragment ligation reaction to a vector encoding hIL13-PE38QQR (Id. ) and cut with Nde I and Hind III restriction enzymes. Table 5. PCR primers used to circularly permute hIL- 13.

PCR Sequence Sequence ID primer No. cpl 5 ^• -GTGACTGCAGGTGTCCATATGTACTGTGCAGCCCTGGA-3 ' 1 cp2 5 ^• -CCCAAACCGCGGGATCCACCGTTGAACCGTCCCTCGCGAA-3 ' 2 cp3 5 ' -GCAGTCGTGGGTGGATCCGGCGGTTCCCCAGGCCCTGTGCCTCC-3' 3

Cp4 5'-TGGTGCAGCATCAAAAGCTTTGCCAGCTGTCAGGTTGATGC-3' 4

The resulting plasmid, pCP/hILl3-PE38QQR, carried the cDNA for a circularly permuted hIL13 in which the new N-terminus starts at Met 44 of the wild type interleukin- 13. Four additional amino acids (GlyGlySerGlyGly) are located in between the residues 1 14 and 1 of the wild type hIL13. Circularly permuted hIL 1 was linked to the first amino acid of PE38QQR The cphIL- 13-PE38QQR was expressed in E. coli and purified to homogeneity

Both hIL- 13-PE4E and cphIL- 13-PE38QQR exhibited cytotoxic activities that were two to ten fold better than those seen with hIL- 1 -PE38QQR IC, _u s were as

low as < 0.1 ng/ml ( < 2 pM) on several glioma cell lines. Fresh human glioma explant cells were also killed at these low concentrations. The data suggest that the recepotr for IL-13 is an excellent target for the treatment of human gliomas using IL- 13R directed cytotoxins.

Example 10

Activity of IL-13R Directed Cytotoxins on Neural Cancers

The cytotoxicity of two chimeric toxins (hIL- 13-PE38QQR and hlL- 13PE4E) was tested on cancer cell lines of neural origins The DAOY, TE671 . and D283 meduUoblastoma cell lines were all responsive to hIL- 13 fused to PE4E The

IC _JQ S recorded in an MTS colorimetric cytotoxicity assay were m a range of < 1 ng/ml to 50 ng/ml ( <20pM to InM, respectively). In addition, human meduUoblastoma explant cells also responded well to hIL- 13-PE4E.

On the other hand, the SK-N-MC and Neuro-2A neuroblastoma cells were poorly responsive (IC _5u s > 4 nM). The data, however, suggest that the overexpression of a receptor for hIL- 13 is not restricted to gliomas, but it can be observed in neuron- derived cancers.

Example 11 II.-13R Targeted Cytotoxins are Effective Against Kaposi's -Snrcomn

The recombinant immunotoxin IL- 13-PE38QQR was also tested against Kaposi's sarcoma cell lines (NCB59, KS248, KS220B, KS54A, and ARL- 13). All ot the cell lines were cytotoxin sensitive with ID^s ranging from about 8 ng/ml to about 180 ng/ml. The Kaposi's sarcoma cell lines all expressed IL- 13 receptors at higher levels than normal cells, however the levels were lower than the IL-13R expression levels found in renal cell carcinoma or in gliomas.

Example 12 ITr-4 Receptors are "Decoupled" from IL-13 Receptors on Tumor Cells In this example the interactions between the human IL- 13 receptor (hlL-

13R) and the human IL-4 receptor (I.IL-4R) are studied in human glioma cells This

study utilizes established human glioma cell lines and, tor the first time, cells ot a human glioblastoma multiforme explant to test the cytotoxicities of chimeπc toxins and responses to hIL- 13 and hIL-4

The results indicate that one predominant form of hIL- 13R is overexpressed on tumor cells such as glioma cells. Unlike IL-13 receptors on "healthy" cells, these IL- 13 receptors are not blocked by agents that bind to IL-4 receptors. The data indicate that blocking of IL-4 receptors will significantly increase the specificity of molecules directed to the IL- 13 receptor.

Materials and Methods

Restriction endoiuicleases and DNA ligase were obtained from New England Biolabs (Beverly, Massachusetts, USA), Bethesda Research Laboratories (BRL, Gaithersburg, Maryland, USA) and Boehπnger Mannheim (Indianapolis, IN). [ ³ H]-leucιne and ¹²⁵ I were purchased from Amersham Corporation (Arlington Heights, Illinois, USA). Fast protein liquid chromatography (FPLC) columns, media, and

Ficoll-Paque were purchased from Pharmacia (Piscataway, New Jersey, USA). Oligonucleotide primers were synthesized at Pharmacia's Gene Assembler at the Research Centre, HDM-UM PCR kit was from Perkin-Elmer Cetus (Norwalk, Connecticut, USA). MTS/PMS (see below) for cell titer 96 aqueous non-radioactive cell proliferation assay was purchased from Promega (Madison, Wisconsin, USA)

Plasmids bacterial strains and cell lines

Plasmids carry a T7 bacteπophage late promoter, a T7 transcription terminator at the end of the open reading frame of the protein, a fi origin of replication and gene for ampicillin resistance (Debinski, et al , J Clin Invest 90:405-41 ( 1992)) The cDNA encoding sequence for hlL- 13 was PCR-cloned to produce hILI13-PE38QQR, as described in Example 4 (see also Debinski, et al , J Biol Chem 270: 16775-16780 (1995)) Recombinant proteins were expressed in E coli BL21 (λDE3) under control of T7 late promoter (Studier, et al , J. Mol. Biol 189. 1 13- 130 (1986)). Plasmids were amplified in E. coli (HB101 or DH5α high efficiency

transformation) (BRL) and DNA was extracted using Qiagen kits (Chatsworth, California, USA).

The cytotoxic activity of chimeric toxins and antiprol iterative activity of ILs were tested on several brain tumor cell lines, such as U-373 MG, DBTRG-05 MG, A-172, Hs 683, U-251 MG. and SW- 1088. The majority ot cell lines were obtained from the American Type Culture Collectιon(ATCC, Bethesda, Maryland, USA) and they were maintained under conditions recommended by the ATCC

Glioma explant cells preparation. Pathology proven surgical specimen of glioblastoma multiforme was collected and transferred to the laboratory under sterile conditions. Peripheral and necrotic tissue were excised and the remaining tissue minced using a scalpel. Tumor tissue was incubated in a cocktail composed of collagenase type 1 1 and IV, Dispase, and NuSerum/DMEM, at 37°C with constant shaking tor 45 nun Cell suspension was then passed through gauze and washed first with Hanks BSS and then with PBS (Ca ^{+ +} ,

Mg ^{+ +} -free). Cells were then layered on the Ficoll-Paque and centrifuged at 400 xg at 18-20°C for 35 mm The isolated cells were resuspended in 3x volume of balanced salt solution, centrifuged at 100 xg, at 18-20°C tor 10 min The pellet was washed one more time with the same solution and finally resuspended in RPMI 1640/25 mM HEPES with L-glutamine and supplemented with 10% FCS, 0. 1 ng/ml L-cystine, 0 02 mg/ml L-prohne, 0. 1 mg/ml sodium pyruvate, HT supplement and antibiotics The cells were transferred into 100 mm plates and incubated at 37°C in 95 %) 0,/5 % C0 _? humidified atmosphere.

Expression and purification of lecombinant proteins

E coli BL21 (λDE3) cells were transformed with plasmids of interest and cultured in 1.0 liter of Super broth The chimeπc toxins and interleukins were localized to the inclusion bodies The procedure for the recombinant proteins isolation from the inclusion bodies was described previously (Debinski, et al , J Biol Chem 268: 14065-14070 (1993)) Atter dialysis, the renatured protems were purified on

ion-exchange columns and by size exclusion chromatography on Sephacryl S-200HR (Pharmacia).

Protein concentration was determined by the Bradford assay (Pierce "Plus", Rockford, IL) using BSA as a standard.

Protein synthesis inhibition assay

The cytotoxic activities of chimeπc toxins, such as hIL- 13-PE38QQR and hIL-4-PE38QQR, were tested as follows: usually 5 x iO ³ cells per well were plated in a 96-well tissue culture plate in 200 μl of media. Various concentrations of the chimeπc toxins were diluted in 0.1 % BSA/PBS and 25 μl of each dilution was added to cells 20- 28 h following cell plating. Cells were incubated at 37°C for another 48 h. Then, the cytotoxicity was determined using a colorimetric MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3- carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolιum, inner salt]/PMS (phenazine methasulfate) cell proliferation assay. MTS/PMS was added at a half final concentration as recommended by the manufacturer. The cells were incubated with the dye for 6 hr and then the absorbance was measured at 490 nm for each well using a microplate reader (Cambridge Technology, Inc. , Watertown, Massachusetts, USA). The wells containing no cells or wells with cells treated with high concentrations of PE or hIL- 13-PE38QQR (10 μg/ml), or wells with no viable cells left served as a background for the assay. For blocking studies, rhIL-4 or rhIL- 13 was added to cells for 60 mm before the chimeπc toxins addition. Data were obtained from the average of quadruplicates and the assays were repeated several times.

To evaluate the effects of interleukins on cell proliferation, the assays were performed as follows: 1 x 10 ³ cells per well were plated in a 96-well tissue culture plate in

200 μl of 0.5 % FBS-containing media and the interleukins were added 20 h following cell plating. After seven-day or five-day cubation with the interleukins, MTS/PMS was added to the cells for 6 h, and the assay was performed as described above for the chimeric toxins.

Competitive binding assay

Recombinant human IL- 13 (rHIL- 13) and recombinant IL-4 (rIL-4)labeled with ^I25 I (Amersham Coψ.) using the IODO-GEN reagent (Pierce) according to the manufacturer's instructions The specific activities of radiolabeled cytokines were estimated to be between 20 to 100 μCi/μg of protein ot protein tor ^l2S I-hIL- 13 and 179 μCi/μg of protein for ¹²⁵ l-hIL-4

Binding experiments were performed as described in Example 1 and by Obin, et al , J. Biol Chem. 270:8797-8804 ( 1995) Typically, 1 x 10 ⁶ to 1 5 x 10" tumor cells were incubated at 4°C tor 2 h with ^l25 I-hIL- 13( 100-500 pM) or I-hIL-4 (100-500pM with or without increasing concentrations (up to 1000 nM) of unlabeled interleukins. The data were analyzed with the LIGAND program (Obin , et al J Biol Chem. 270:8797-8804 ( 1995), Munson et al , Analv Biochem 107 220-239 ( 1980)) to determine receptor number and bmding affinity

Re-sults hIL-13-PE38QQR is extremely cytotoxic to both established glioma cell lines and glioblastoma multiforme explant cells

The A- 172, DBTRG MG, and Hs-683 established human glioma cell lines and, for the first time, glioma explant cells (G2) were tested to determme and/or confirm if hIL-13-PE38QQR is cytotoxic to them All the established glioma cell lines were very responsive with an IC, ₀ Of 0. 1 to 5 ng/ml (Fig 1 ) Ot interest, human glioma explant cells were also extremely sensitive to the action ot hIL- 13-toxιn; the IC _W for hIL-13-PE38QQR was 0.2 ng/ml (Fig 1 ) The cytotoxic action ot hIL- 13-PE38QQR was specific as it was blocked by an excess ot hIL- 13 on all cells (see, e g, Example 5) These data demonstrate that both established glioma cell lines and a primary culture ot glioma cells possess hIL- 13 binding sites and such cells are extremely sensitive to hlL- 13-PE38QQR chimeric toxin

hIL-4 does not block the cytotoxicity of hIL- 13-PE38QQR on glioma cell lines and glioma explant cells.

Because hlL- 13R has been shown to be related to IL-4R (see, e.g. , Examples 4 and 5, Debinski, et al , J. Biol Chem. 270: 16775- 16780 ( 1995); Obin, er al , J. Biol. Chem. 270:8797-8804 ( 1995); Zurawski, et al , EMBO J. 12:2663-2670

(1993)), the specificity of hIL- 13-PE38QQR action on the glioma cell lines and G2 explant cells was further explored. The cells were treated with hIL-13-PE38QQR with or without recombinant (r) hIL-4 at a concentration of 1.0 μg/ml. The rhIL-4 did not have any blocking action against hIL- 13-PE38QQR on either the established cultured cells (A- 172, Hs 683, and DBTRG MG) or freshly explanted cultured glioma cells, even at a 1000-fold molar excess over the chimeric toxin (Fig. 1 ). These results indicate that the cell killing by the hIL- 13-toxin on these cells is independent of the presence of hlL- 4. The same results were obtained with the U-25 1 MG, U-373 MG (Example 8) and on U-87 MG and SNB- 19 cell lines. Since these data are in contrast to observation made on several adenocarcinoma cells (Example 5, Debinski, et al , J. Biol. Chem. 270: 16775- 16780 (1995)), the cytotoxicity experiments were repeated, for example, on Colo 201 human colon adenocarcinoma cells employing a colorimetric assay used in the present study (instead of tritium incorporation) and reproduced exactly same results.

hlL-13 blocks the action of ML-4-toxins on the U-251 MG, DBTRG MG, and A-I72 glioma cells, and glioma G2 explant cells.

To investigate the possibility that hi 13 and IL-4 may nevertheless compete, although not reciprocally, for the same binding site on glioma cells, the cells were also treated with hIL-4-based recombinant toxin, hIL-4-PE38QQR (Debinski, et al , Int. J. Cancer 58:744-748 ( 1994)) (Fig. 2). It has previously been demonstrated that all tested glioma ceil lines express specific 140 kDa hIL-4R, as determined by a immunoreactivity of an antibody raised against the protein (Pun, et al , Int. J. Cancer 58:574-581 (1994)). The data again show, unexpectedly, that hIL-4-PE38QQR was without any significant specific cytotoxicity to most of these cells (Fig. 2) including the Hs-683 and U-373 MG cells. Only the U-251 MG glioma cell line responded relatively

well to hIL-4-38QQR with an IC _jυ of 10 ng/ml. This cytotoxicity was blocked efficiently by an excess of hIL- 13 (Fig. 2) Thus, the cytotoxicity of hIL-4-PE38QQR is blocked by an excess of hIL-13, however, the cytotoxic action ot hIL-4-PE38QQR is absent on the majority of glioma cell lines and human glioma explant cells. Since interleukins coupled to PE4E form ot the toxin exhibit better cytotoxic activities on cancer cells (e g , Debinki et al , J Biol Chem, 268 14065 14070), the glioma cells were also treated with hIL-4-PE4E The higher cytotoxic potency of this chimeπc protein when compared to hIL-4-PE38QQR was observed on several glioma cells as well as on G2 explant cells (Fig 3) The IC, _(I ranged from 10 to 200 ng/ml on U-251 MG, DBTRG MG. A- 172, G2 explant (Fig 3), and U-87 MG cells. The cytotoxic action ot hIL-4-PE4E was blocked by an excess ot hIL- 13 (Fig 3) in a manner similar to the blocking ot this cytotoxicity by hIL-4 The blocking on G2 cells was less than on other cell lines (Fig 3) and a similar response was seen on SNB- 19 cells. These results demonstrate that hIL-4 and hIL- 13 have a common binding site on the glioma cell lines and are reminiscent ot the previous findings on a series ot adenocarcinoma cells. However, there is also a profound difference between these and and previous findings, since the commonality is not reciprocal, / e , only hIL- 13 is a competitor for the two receptors

Antφroliferative effects of hIL-13 and hIL-4 on ^→ →-lioma cells

Despite being competitors tor the same binding site on some cancer cells, differences in hIL- 13- and hIL-4-ιnduced cellular effects were observed (Example 5) Namely, protein synthesis was inhibited in A431 epidermoid carcinoma cells in a dose-dependent manner by hIL-4, while hIL- 13 had no effect on these cells, even at concentrations as high as 10 μg/ml ot hIL- 13 for a 72 h incubation (Example 5) Similarly, hIL-13 had no effect on the growth of glioma cells The U-25 1 MG, U-373 MG glioma cells (Fig 4), and G2 explant cells (Fig 4), were unaffected by the five-day and/or one-week treatment with IL 13 Human IL-4 also had no activity on the growth of these cells (Fig 4)

hlL-13 binding affinity to A- 172 and G2 explain cells.

Competitive binding assays were performed to determine whether the hlL- 13Rs on the established glioma cell lines, such as A- 172 glioma cells, have different or similar binding affinity for hIL- I 3 compared to the hIL- 13R that is expressed on freshly isolated cells. As shown in Figures 5 A and 5B. unlabeled hlL- 13 competed for the binding of ^{1 3} I-hILl3 to A- 172 cells efficiently (Fig. 5A). The Scatchard plot analysis of displacement experiments (Fig. 5B) revealed one single binding sue for hlL-13 of intermediate affinity; K _u = 1.6 nM. There are 22,600 binding sites for hlL- 13 on the A-172 cell line. The competition of unlabeled hlL-13 for the binding of lodinated ligand (Fig. 6A) and the Scatchard analysis performed on G2 explant cells (Fig. 6B) have shown similar results to that obtained on A- 172 cells. However, the number ot binding sites on explant cells is 300,000 per cell with K _d of 2.4 nM In another experiment, the estimate of hlL-13 binding sites indicated more than 500,000 binding sites per cell.

Thus, there is no difference affinity of hlL- 13 to its receptor whether or not cells are permanently cultured or are derived from the primary culture, although the explant cells seem to be considerably more enriched in hlL- 13 receptors than the established glioma cell cultures.

hIL-4 does not compete for labeled hlL-13 binding sites, but hlL-13 is a competitor for ^l25 I-hIL-4 binding sires on glioma cells.

The first step in the action of a chimeπc toxin is binding of the toxin to a specific (often internalized) receptor. Binding activity was investigated using standard competition experiments were performed at 4°C using radiolabeled ligands. As seen in Fig. 7A hlL-13 displaced labeled hlL- 13 very efficiently on A- 172 glioma cells. However, hIL-4 did not compete for the binding of ^l2-, I-hIL- 13 at all at up to 100 nM ot the competitor. On the other hand, as shown above (Figs 2 and 3), hlL- 13 blocked the actions of both hIL-4-PE38QQR and hIL-4-PE4E on glioma cells. Therefore, the reverse assay was performed nd it was determined that either interleukin was a competitor for ^12S I-hL4 binding sites (Fig. 7B). Thus, the results of binding experiments indicate that the non-reciprocal interference of interleukins with the cytotoxic activities of their respective chimeπc

toxins on glioma cells is due to the non-reciprocal interference with the binding to the interleukin receptors.

hlL-13 is not a competitor for ⁿ⁵ l-hlL-4 binding sites on cells transfected with the 140 kDa hlL-4 receptor.

The foregoing experiments show that hil l 3 blocks the cytotoxicities ot hIL-4-based chimeric toxins and competes for the binding sites of ^{l 2,i} l-hIL-4 on glioma cells. The 140 kDa hIL-4R chain is believed to be a principal hlL-4 binding protein. Therefore, eel Is transfected with the hIL-4 receptor (CTLL ^h " ^~*k ldzerda, et al. J. Exp. Med. 171 :861-873 ( 1990)) were used for competition binding assays. Human IL- 13, unlike hIL-4, does not compete tor the ^12<i I-hIL-4 binding sues on CTLL ¹¹ " ^"41 * cells (Figure 8). In similar experiments with the hIL-4R transgenes hlL- 13 did not compete for labeled hIL-4 binding sites (e.g. Zurawski et al EMBO J , 12 2663-2670 ( 1993)). On the other hand, hlL- 13 is a competitor tor ^l2l I-hIL-4 crosslinking to the 140 kDa protein (Obin, et al , J. Biol Chem. 270:8797-8804 ( 1995), Zurawski, et a/. , J. Biol

Chem. 270: 13869-13878 ( 1995), Vita, et al , J. Biol Chem. 270:3512-3517 ( 1995)). These results and our results obtained on glioma cells using chimeπc toxins indicate that the interaction of hlL- 13 with the hIL-4R involves more elements beside the 140 kDa hIL-4R chain.

DISCUSSION

The foregoing experiments show that glioma cells exhibit different responses to hlL-13 and hIL-4-based chimeric proteins containing PE38QQR as well as to the two interleukins themselves when compared to adenocarcinoma cells. All of the studied glioma cell lines are killed potently by hIL- 13-PE38QQR and these killing activities are blocked specifically by an excess of hlL- 13. On an array of established human glioma cell lines, and represented by the U-273, U-25 1 , DBTRG MG, Hs-683, U-87 MG, SNB- 19, and A- 172 cell lines, hIL-4 cannot block the action of hIL- 13-based chimenc protein. The same phenomenon was observed on primary cultured human glioma cells. Thus, the data indicate that there exists a form of internalized receptor for hlL-13 on glioma cells which does not interact with hIL-4. Of interest a, corresponding

to WL-13-PE-38QQR, hIL-4-based chimeric protein, hIL-4-PE38QQR, is weakly active or not active through specific binding to the hIL-4 binding protein (Table 6). This is seen on the same cell lines which do respond very well to hIL-13-PE38QQR. Thus, the human IL-13 receptor (hIL- 13R) in glioma cells is apparently different from the one described previously ("Adenocarcinomas" in Table 1 ) (Debinski, et al , J. Biol Chem. 270: 16775- 16780 (1995)). When hIL-4-PE388QQR, or hIL-4-PE4E, exerts cytotoxic activity, this activity can be nevertheless neutralized by an excess of hlL- 13, as it was seen on adenocarcinoma cell lines.

Table 6. Cytotoxic activity of hlL- 13 and hIL-4 based chimeric toxins and inhibitory potencies of hlL- 13 and hIL-4 to block these activities on cancer cells. hIL- 13-PE38QQR hIL-4-PE38QQR cytotoxicity cytotoxicity w/o ILs w hIL- 13 w hIL-4 wo ILs w hIL- 13 w hIL-4

Gliomas + -+- -+- + ^■ ' - 4- + + + + +/-

Adenocar 4- + + + + + cinomas a arbitrary estimate of the cytotoxic potency ( + to + -+- + +). cytotoxicity blocked (-)

Studies with a mutated IL-4 first suggested interrelatedness between IL- 13 and IL-4 receptors (Zurawski, et al , EMBO J. 12: 2663-2670 ( 1993)) Although the existence of a novel subunit that is shared between the two receptors was postulated, the same group of investigators has recently pointed to an already identified 140 kDa hlL-4R chain as the component of the hIL- 13R (Zurawski, et al , J. Biol. Chem. 270: 13869-13878 (1995)). This support the studies presented herein. The model systems described herein permits the use of wild-type interleukins and facilitates monitoring the effects of hIL-4 or hlL- 13 on the hIL-4R-, and hIL- 13R-medιated cellular events. In these models the foregoing experiments show reciprocal inhibition of the cytotoxic activities of hIL-4-, and hIL- 1 -based chimeric toxins by the interleukins alone.

It was previously suggested that, in order to explain this phenomenon, the common form of hlL- 13 and hIL-4 receptor on the studied adenocarcinoma cells must be internalized and is composed of a 140 kDa principal subunit ot the hIL-4R (Harada, et

al , J. Biol Chem. 267:22752-22758 ( 1992)) and a 70 kDa hIL- 13-bmdιng protein (Obiri, et al. , J. Biol Chem. 270:8797-8804 ( 1995)), which is in agreement with emerging consensus.

The data on glioma cells presented herein implicate another, previously undescribed hIL-13R that does not involve the 140 kDa subunit of the hIL-4R. Several observations speak in favor of the existence of such a receptor. First, hIL-4-PE38QQR has a very weak activity on most of the glioma cells tested. This result is surprising, since hIL-4-PE38QQR tended to be, e.g. , more active from the corresponding hIL- 13- toxin on several adenocarcinoma cell lines. Therefore, glioma cells should express relatively low levels of hIL-4 binding sues (as compared to number of hlL- 13 sites) which, in fact, has already been documented (Pun, et ul , Inr J Cancer 58:574-581 (1994)). However, even at these levels of hIL-4R expression one would expect better cytotoxic activity of hIL-4-PE38QQR on these cells (Table 1 ) Second, the data presented herein show the lack of involvement of the 140 kDa chain in a hIL- 13-evoked growth-inhibitory effect on human renal cell carcinoma cells Third, hlL-4 is deprived of any ability to influence the action of hIL- 13-PE388QQR on glioma cells, including freshly cultured explant cells, at even 1000-fold molar excess over the chimeπc toxin. This finding is supported by the data obtained herein on renal cell carcinoma cells and indicates the presence of cancer-specific receptor for hlL- 13. Binding experiments using ^I25 I-hIL- 13 also showed the lack of hIL-4 competition for the radiolabeled ligand binding sites However, the hlL-4R that is present on, e.g. , U-251 MG cells interacts with hlL- 13, since hlL- 13 blocks the cytotoxicity of hIL-4-PE38QQR. hlL- 13 appears to be a good competitor for ^12S I-hIL-4 binding sites in a competitive binding assay on glioma cells On the other hand, hlL- 13 does not compete for ^l25 I-hIL-4 binding sites on cells transfected with the 140 kDA hlL-

4R alone. This suggests that the expression of 140 kDa hILL4R is necessary but not sufficient for the interaction with hlL- 13. The specific molecular forms of this and other hlL-13 receptor forms are currently being revealed One common on feature of all these forms is their ability to undergo internalization readily upon binding a ligand, as evidenced by the high effectiveness of hIL- 13-toxιn on vaπous cancer cell lines and explant cells.

Established human glioma cells express up to 30,000 binding sites for hlL-13 per cell and the explant cells even 10 times more. These binding sites represent a new attractive target for the treatment of brain cancers. Since human glioma established cell lines and also human glioma explant cells express an IL-4-independent WL-13R, it is possible to take advantage of this phenomenon pharmacologically.

It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims. All publications, patents, and patent applications cited herein are hereby incorporated by reference for all purposes.