WATER CHAIVNEL BLOCKERS AND METHODS OF USE THEREOF

Richard Boucher and Robert Tarran

Government Support

This invention was made with Government support under grant number RR00046 from the National Institutes of Health. The Government has certain rights to this invention.

Field of the Invention

The present invention concerns methods of treatment, and particularly methods of treatment in which blocking of water channels in a subject would be of therapeutic benefit, such as subjects afflicted with edema, sickle cell anemia, reperfusion injury, etc.

Background of the Invention

Water channels are proteins that are situationed in cell membranes and serve as pores through which water may pass. In the mid-1980's Peter Agre, studying various proteins from red blood cells and kidney, first identified the proteins that actually form water channels. Such proteins are called "aquaporins" (meaning "water pore"). See generally The Nobel Prize in Chemistry 2003 — Information for the Public, Kungl. Vetenskapsakademien: The Royal Swedish Academy of Sciences (8 October 2003). ^•

Water channels are ubiquitous in nature and throughout the cellular machinery of animal, including mammalian, tissues and systems. Hence, water channel blockers are, potentially, of significant and diverse benefit for medical treatments. Unfortunately, few such water channel blockers are known and there is a need for new and additional water channel blockers.

Summary of the Invention

The present invention provides a method of blocking water channels (such as aquaporins) in a subject in need thereof, comprising administering to said subject an active compound to block water channels in said subject. In some embodiments the active compound is a pyrazinoylguanidine compound (e.g. amiloride, benzamil, phenami) or a pharmaceutically acceptable salt or prodrug thereof.

A second aspect of the present invention is the use of an active compound as described herein for the preparation of a medicament for carrying out a method of treatment as described herein.

Brief Description of the Drawings

Figure 1: Effect of HS ± amiloride on ASL volume in normal and CF epithelia.

(A) ASL height, measured by confocal microscopy, before and after the addition .of 0.8 mg of. NaCl to CF epithelia. (B) ASL height in normal epithelia before and after 0.8 mg of NaCl (solid, black squares); effect of pretreatment with CFTRinh-172 (open, red circles); and effect of chloride substitution with gluconate. ^Denotes significantly different to control time points, with p < 0.05. (C) ASL volume response to 0.8 mg of NaCl after pretreatment with amiloride. *denotes difference between paired timepoints in Fig. 4A. (D) The change in serosal fluorescent intensity reflected water transport in the serosal to mucosal direction in response to apical hypertonic mannitol challenge with/without amiloride pretreatment in CF epithelia. *denotes significant difference in the slope of lines fitted through data points, with p < 0.05.

Figure 2 shows that amiloride blocks aquaporin 5.

Detailed Description of the Preferred Embodiments "Aquaporin" or "Aquaporins" are known, and as used herein mean and include any aquaporin, including but not limited to aquaporin-0, aquaporin-1, aquaporin-2, aquaporin-3, aquaporin-4, aquaporin-5, aquaporin-6, aquaporin-7, aquaporin-8, and aquaporin-9. The aquaporin may be of any species, preferably mammalian (e.g., dog, cat, horse, cow, goat, sheep, pig, monkey, etc.) and including human (including both males and females and infant, child, adolescent, adult and geriatric subjects).

The term "treat" as used herein refers to any type of treatment that imparts a benefit to a patient afflicted with a condition or disease, including improvement in the condition of the patient (e.g., in one or more symptoms), delay in the progression of the disease, etc.

The term "pharmaceutically acceptable" as used herein means that the compound or composition is suitable for administration to a subject to achieve the treatments described herein, without unduly deleterious side effects in light of the severity of the disease and necessity of the treatment.

The present invention is primarily concerned with the treatment of human subjects, but the invention may also be carried out on animal subjects, particularly mammalian subjects such as mice, rats, dogs, cats, livestock and horses for veterinary purposes, and for drug screening and drug development purposes. "Block" as used herein means sufficient blockage to achieve a beneficial treatment effect in the subject. Blocking need not be total and need not be permanent so long as a clinical benefit in the subject is achieved. Thus the phrase. "amount effective to block", is to . be treated as essentially the same as "amount effective to treat" where a particular disorder or condition to be treated is named. Subjects to be treated by the methods of the present invention include those afflicted with edema, particularly ischemic edema. The ischemic edema may be of the brain, heart, kidney, or muscle {e.g., ischemic necrosis).

Subjects to be treated by the methods of the present invention furtherinclude subjects at risk or afflicted with: sickle cell anemia, tissue reperfusion injury (such as organ transplant subjects, subjects afflicted with an ischemic injury such as heart attack, stroke, etc), macular degeneration, inappropriate anti-diuretic hormone (ADH) secretion, pulmonary edema (including cardiogenic and non-cardiogenic pulmonary edema and high-altitude pulmonary edema), inhalation burn injury, post trauma swelling (e.g., of a limb OF extremity), angioadema, allergic reactions such as drug allergy or bee sting allergy, post venous obstructive syndromes (including superior vena cava syndrome, and post-phlebitic syndrome), diabetic hyperosmolar coma or severe hyperglycemia, hyponatremia, pulmonary embolism with infarction, Maniere's disease, malaria, osteoporosis, hypertension, watery eyes, rhinorrhea (runny nose) etc.

The disclosures of all United States patent references cited herein are to be incorporated by reference herein in their entirety.

1. Active compounds. Active compounds that may be used to carry out the present invention include pyrazinoylguanidine compounds, including analogs thereof.. These structures were previously functionally described as sodium channel blockers. Examples of such compounds are disclosed in U.S. Patent No. 3,313,813 to Cragoe. Amiloride, one particular pyrazinoylguanidine compound, is described at Merck Index Registry No. 426 (12 ^th Ed. 1996). Benzamil (also known as 3,5-diamino-6-chloro-N-(benzylaminoaminomethylene) pyrazinecarboxamide) and phenamil (also known as 3,5-diamino-6-chloro-N-

(phenylaminoaminomethylene) pyrazinecarboxamide) are known compounds and are also disclosed in U.S. Pat. No. 3,313,813 to E. Cragoe.

Various additional pyrazinoylguanidine compounds that are amiloride analogs are disclosed and described in T. Kleyman and E. Cragoe , J. Membrane Biol. 105, 1-21 (1988).

Preferred examples of active compounds that may be used to carry out the present invention are the pyrazinoylguanidine compounds disclosed in U.S. Pat. No. 3,313,813, incorporated by reference above. Such compounds have the formula: . _ .

wherein:

X is selected from the group consisting of chloro, bromo, iodo, loweralkyl, lower- cycloalkyl having from 3 to 7 carbons, phenyl, chlorophenyl, bromophenyl, Z-thio and Z- sulfonyl wherein Z is selected from the group consisting of loweralkyl and phenyl- loweralkyl. Preferably, X is chloro.

Y is selected from the group consisting of hydroxyl, mercapto, loweralkyloxy, loweralkylthio, chloro, loweralkyl, lowercycloalkyl having from 3 to 6 carbons, phenyl, amino having the structure:

R

-N

Ri

wherein:

R is selected from the group consisting- of hydrogen, amino,— amidino, lowercycloalkyl having 3 to 6 carbon atoms, loweralkyl, hydroxyloweralkyl, halo-loweralkyl, lower-(cycloalkylalkyl) having 3 to 6 carbons in the ring, phenyl-loweralkyl, lower- (alkylaminoalkyl), lower-alkenyl, phenyl, halophenyl, and lower-alkylphenyl;

Ri is selected from the group consisting of hydrogen, loweralkyl, loweralkenyl, and additionally;

R and R| can be joined to form a lower alkylene. Preferably. Y is amino.

R ₂ is selected from the group consisting of hydrogen and loweralkyl. Preferably, R, Ri, and R ₂ are hydrogen.

R ₃ and R ₄ are indepenedently selected from the group consisting of hydrogen, loweralkyl, hydroxy-loweralkyl, phenyl-loweralkyl, (halophenyl)-loweralkyl, lower-

(alkylphenylalkyl), (loweralkoxyphenyl)-loweralkyl, naphthyl-loweralkyl, (octahydro-1- azocinyl)-loweralkyl, pyridyl-loweralkyl, and loweralkyl radicals linked to produce with the nitrogen atom to which they are attached a 1-pyrrolidinyl, piperidino, morpholino, and a A- loweralkyl-piperazinyl group, and phenyl. Preferably, R ₃ is hydrogen, phenyl, or phenylalkyl. Preferably, R ₄ is hydrogen.

In some embodiments the active compound is a conjugate of a pyrazinoylguanidine compound (e.g., as described above) and a non-absorbable carrier moiety such as carbohydrates, proteins, peptides, polyamines, and water soluble linear polymers. Specific examples of such carrier moieties are polyvinylpyrrolidone, poyethylene glycol, nonylphenol ethoxylates, polyvinyl alcohol; sugars and polysaccharides; dextran, lactose, sialic acid and mannitol; albumin and protamine; spermine and spermidine; etc. Such compounds are known and described in, for example, US Patent No. 6,264,975 to Boucher.

In some embodiments the active compound is a compound of the formula Pi-L-P ₂ , wherein Pi is a pyrazinoylguanidine compound (e.g. as described above), L is a linking group; and P ₂ is a pyrazinoylguanidine compound (e.g. as described above).

Such compounds are known and described in, for example, US Patent No. 6,613,345 to

Boucher.

Still other examples of active compounds of the present invention include those described in US Patent Applications Publication Numbers 20040229884; 20040204425; 20040204424; 20040198749; 20040198748; 20040198747; 20040198746; 20040198745;

20040198744; and 20040162296 (all to Parion Inc.), the disclosures of all of which are incorporated by reference herein in their entirety.

The active compounds disclosed herein can, as noted above, be prepared in the form of their pharmaceutically acceptable salts. Pharmaceutically acceptable salts are salts that retain the desired biological activity of the parent compound and do not impart undesired toxicological effects. Examples of such salts are (a) acid addition salts formed with inorganic acids, for example hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid and the like; and salts formed with organic acids such as, for example, acetic acid, oxalic

acid, tartaric acid, succinic acid, maleic acid, fiimaric acid, gluconic acid, citric acid, malic acid, ascorbic acid, benzoic acid, tannic acid, palmitic acid, alginic acid, polyglutamic acid, naphthalenesulfonic acid, methanesulfonic acid, p-toluenesulfonic acid, naphthalenedisulfonic acid, polygalacturonic acid, and the like; (b) salts formed from elemental anions such as chlorine, bromine, and iodine, and (c) salts derived from bases, such as ammonium salts, alkali metal salts such as those of sodium and potassium, alkaline earth metal salts such as those of calcium and magnesium, and salts with organic bases such as dicyclohexylamine and N-methyl-D-glucamine.

The term "pharmaceutically acceptable prodrugs" as used herein refers to those prodrugs of the compounds of the present invention which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of humans and lower animals without undue toxicity, irritation, allergic response and the like, commensurate with a reasonable risk/benefit ratio, and effective for their intended use, as well as the zwitterionic forms, where possible, of the compounds of the invention. The term "prodrug" refers to compounds that are rapidly transformed in vivo to yield the parent compound of the above formulae, for example, by hydrolysis in blood. A thorough discussion is provided in T. Higuchi and V. Stella, Prodrugs as Novel delivery Systems, Vol. 14 of the A.C.S. Symposium Series and in Edward B. Roche, ed. ₅ Bioreversible Carriers in Drug Design, American Pharmaceutical Association and Pergamon Press, 1987, both of which are incorporated by reference herein. See also US Patent No. 6,680,299 Examples include a prodrug that is metabolized in vivo by a subject to an active drug having an activity of active compounds as described herein, wherein the prodrug is an ester of an alcohol or carboxylic acid group, if such a group is present in the compound; an acetal or ketal of an alcohol group, if such a group is present in the compound; an N-Mannich base or an imine of an amine group, if such a group is present in the compound; or a Schiff base, oxime, acetal, enol ester, oxazolidine, or thiazolidine of a carbonyl group, if such a group is present in the compound, such as described in US Patent No. 6,680,324 and US Patent No. 6,680,322.

2. Pharmaceutical formulations. The active compounds described above may be formulated for administration in a pharmaceutical carrier in accordance with known techniques. See, e.g., Remington, The Science And Practice of Pharmacy (9 ^th Ed. 1995). In the manufacture of a pharmaceutical formulation according to the invention, the active compound (including the physiologically acceptable salts thereof) is typically admixed with, inter alia, an acceptable carrier. The carrier must, of course, be acceptable in the sense of

being compatible with any other ingredients in the formulation and must not be deleterious to the patient. The carrier may be a solid or a liquid, or both, and is preferably formulated with the compound as a unit-dose formulation, for example, a tablet, which may contain from 0.01 or 0.5% to 95% or 99% by weight of the active compound. One or more active compounds may be incorporated in the formulations of the invention, which may be prepared by any of the well known techniques of pharmacy comprising admixing the components, optionally including one or more accessory ingredients.

The formulations of the invention include those suitable for oral, rectal, topical, buccal (e.g., sub-lingual), vaginal, parenteral (e.g., subcutaneous, intramuscular, intradermal, or intravenous), topical (Le., both skin and mucosal surfaces, including airway surfaces) and transdermal administration, although the most suitable route in any given case will depend on the nature and severity of the condition being treated and on the nature of the particular active compound which is being used.

Formulations suitable for oral administration may be presented in discrete units, such as capsules, cachets, lozenges, or tablets, each containing a predetermined amount of the active compound; as a powder or granules; as a solution or a suspension in an aqueous or non-aqueous liquid; or as an oil-in-water or water-in-oil emulsion. Such formulations may be prepared by any suitable method of pharmacy which includes the step of bringing into association the active compound and a suitable carrier (which may contain one or more accessory ingredients as noted above). In general, the formulations of the invention are prepared by uniformly and intimately admixing the active compound with a liquid or finely divided solid carrier, or both, and then, if necessary, shaping the resulting mixture. For example, a tablet may be prepared by compressing or molding a powder or granules containing the active compound, optionally with one or more accessory ingredients. Compressed tablets may be prepared by compressing, in a suitable machine, the compound in a free-flowing form, such as a powder or granules optionally mixed with a binder, lubricant, inert diluent, and/or surface active/dispersing . agent(s). Molded tablets may be made. by molding, in a suitable machine, the powdered compound moistened with an inert liquid binder. Formulations suitable for buccal (sub-lingual) administration include lozenges comprising the active compound in a flavoured base, usually sucrose and acacia or tragacanth; and pastilles comprising the compound in an inert base such as gelatin and glycerin or sucrose and acacia.

Formulations of the present invention suitable for parenteral administration comprise sterile aqueous and non-aqueous injection solutions of the active compound, which preparations are preferably isotonic with the blood of the intended recipient. These preparations may contain anti-oxidants, buffers, bacteriostats and solutes which render the formulation isotonic with the blood of the intended recipient. Aqueous and non-aqueous sterile suspensions may include suspending agents and thickening agents. The formulations may be presented in unit\dose or multi-dose containers, for example sealed ampoules and vials, and may be stored in a freeze-dried (lyophilized) condition requiring only the addition of the sterile liquid carrier, for example, saline or water-for-injection immediately prior to use. Extemporaneous injection solutions and suspensions may be prepared from sterile powders, granules and tablets of the kind previously described. For example, in one aspect of the present invention, there is provided an injectable, stable, sterile composition comprising an active compound such as a compound of Formula (I), or a salt thereof, in a unit dosage form in a sealed container. The compound or salt is provided in the form of a ly.ophilizate which is capable of being reconstituted with a suitable pharmaceutically acceptable carrier to form a liquid composition suitable for injection thereof into a subject. The unit dosage form typically comprises from about 10 mg to about 10 grams of the compound or salt. When the compound or salt is substantially water-insoluble, a sufficient amount of emulsifying agent which is physiologically acceptable may be employed in sufficient quantity- to emulsify the compound or salt in an aqueous carrier. One such useful emulsifying agent is phosphatidyl choline.

Formulations suitable for rectal administration are preferably presented as unit dose suppositories. These may be prepared by admixing the active compound with one or more conventional solid carriers, for example, cocoa butter, and then shaping the resulting mixture. Formulations suitable for topical application to the skin preferably take the form of an ointment, cream, lotion, paste, gel, spray, aerosol, or oil. Carriers which may be used include petroleum jelly, lanoline, polyethylene glycols, alcohols, transdermal, enhancers,., and combinations of two or more thereof.

Formulations suitable for transdermal administration may be presented as discrete patches adapted to remain in intimate contact with the epidermis of the recipient for a prolonged period of time. Formulations suitable for transdermal administration may also be delivered by iontophoresis (see, for example, Pharmaceutical Research 3 (6):318 (1986)) and typically take the form of an optionally buffered aqueous solution of the active compound.

Suitable formulations comprise citrate or bisNtris buffer (pH 6) or ethanol/water and contain from 0.1 to 0.2M active ingredient.

Further, the present invention provides liposomal formulations of the compounds disclosed herein and salts thereof. The technology for forming liposomal suspensions is well known in the art. When the compound or salt thereof is an aqueous-soluble salt, using conventional liposome technology, the same may be incorporated into lipid vesicles. In such an instance, due to the water solubility of the compound or salt, the compound or salt will be substantially entrained within the hydrophilic center or core of the liposomes. The lipid layer employed may be of any conventional composition and may either contain cholesterol or may be cholesterol-free. When the compound or salt of interest is water-insoluble, again employing conventional liposome formation technology, the salt may be substantially entrained within the hydrophobic lipid bilayer which forms the structure of the liposome. In either instance, the liposomes which are produced may be reduced in size, as through the use of standard sonication and homogenization techniques. Of course, the liposomal formulations containing the compounds disclosed herein or salts thereof, may be lyophilized to produce a lyophilizate which may be reconstituted with a pharmaceutically acceptable carrier, such as water, to regenerate a liposomal suspension.

Other pharmaceutical compositions may be prepared from the water-insoluble compounds disclosed herein, or salts thereof, such as aqueous base emulsions. In such an instance, the composition will contain a sufficient amount of pharmaceutically acceptable emulsifying agent to emulsify the desired amount of the compound or salt thereof.

Particularly useful emulsifying agents include phosphatidyl cholines, and lecithin.

In addition to active compounds such as compounds of formula (I) or their salts, the pharmaceutical compositions may contain other additives, such as pH-adjusting additives. In particular, useful pH-adjusting agents include acids, such as hydrochloric acid, bases or buffers, such as sodium lactate, sodium acetate, sodium phosphate, sodium citrate, sodium borate, or sodium gluconate. Further, the compositions may contain microbial preservatives.

Useful microbial preservatives include methylparaben, propylparaben, and benzyl alcohol.

The microbial preservative is typically employed when the formulation is placed in a vial designed for multidose use. Of course, as indicated, the pharmaceutical compositions of the present invention may be lyophilized using techniques well known in the art.

3. Dosage and routes of administration. As noted above, the present invention provides pharmaceutical formulations comprising the active compounds (including the

pharmaceutically acceptable salts thereof), in pharmaceutically acceptable carriers for oral, rectal, topical, buccal, parenteral, intramuscular, intradermal, or intravenous, and transdermal administration.

The therapeutically effective dosage of any specific compound, the use of which is in the scope of present invention, will vary somewhat from compound to compound, and patient to patient, and will depend upon the condition of the patient and the route of delivery. As a general proposition,, a dosage from about 0.1. to about 50 mg/kg will have therapeutic efficacy, with all weights being calculated based upon the weight of the active compound, including the cases where a salt is employed. Toxicity concerns at the higher level may restrict intravenous dosages to a lower level such as up to about 10 mg/kg, with all weights being calculated based upon the weight of the active base, including the cases where a salt is employed.

The present invention is explained in greater detail in the following non-limiting Examples.

EXAMPLES 1-2

Prolonged Airway Surface Liquid Volume Response to HS by CF Epithelia. The addition of NaCl to the mucosal surface of airway epithelial cultures, simulating the deposition of 7% NaCl(Sood N et al., Am J Respir Crit Care Med 2003;. 167(2): 158- 163.), produced a much larger and more sustained increase in ASL height (volume) in CF than in normal cultures (Fig. IA, B). Because there is no evidence that water permeability differs between normal and CF epithelia (Matsui H et al., J Clin Invest 2000; 105(10):1419-1427), we tested the hypothesis that the CF response reflected the absence of the CFTR Clchannel as a transcellular absorptive path. Normal cultures, exposed to a CFTR Clchannel blocker (CFTRiπh-172) or to the impermeant anion gluconate replacing Cl- in the apical hypertonic solution, exhibited significantly increased ASL height (volume) responses to the hypertonic challenge (Fig. IB). These data indicate, that the rate of passive transcellular diffusion of hypertonic NaCl across airway surfaces is a key determinant of the ASL volume response to HS administration. Amiloride Inhibits Transepithelial Water Transport in Response to HS. The capacity of HS to produce large and prolonged increases in ASL in CF cultures was almost completely blocked by amiloride pretreatment (compare Fig. 1C and IA). We investigated whether this effect reflected an amiloride block of ransepithelial water flow across CF airway epithelia by

measuring amiloride's effect on osmotically induced water flow. The slower increase in serosal fluorescent intensity in response to mucosal hyperosmolar mannitol solutions was consistent with a block of transepithelial water permeability (Fig. ID).

EXAMPLE 3

Cell height response to luminal hypertonic solutions as an index of apieal membrane aquaporin 5 expression

Aquaporin-5 is a mammalian water channel protein that is present in the the respiratory tract, salivary and lacrimal gland epithelia, and corneal epithelium. See, e.g., J. Hoffert, J. Biol. Chem. 275, 9070-9077 (2000). The data presented in Figure 2 shows that amiloride blacks aquaporin-5.

MDCK cells, either sham transfected or transfected wtih aquaporin 5, were loaded with calcein AM for visualization by confocal microscopy in the x-z mode. At time=0, the lumenal solution was changed from an isosmotic solution to one that was hypertonic (150 mOsm added mannitol). The control cells lost cell height ie shrunk, reflecting water movement from the cell into the lumenal liquid following exposure to lumenal hypertonic solutions. The rate of shrinking is a reflection of the water permeability of the apical membrane. In contrast, following application of amitoride (400 micromolar) to the lumen, aqp 5 MDCK cell shrinkage in response to lumenal hypertonic solution was greatly diminished. These data show that amiloride has blocked water movement through the aqp5 water channel in the apical membrane of the aqp5 transfected cell-and that amiloride is an aquaporin blocker.

The foregoing is illustrative of the present invention, and is not to be construed as limiting thereof. The invention is defined by the following claims, with equivalents of the claims to be included therein.