Pharmaceutical formulation of the tubulin inhibitor lndibulin for oral administration with improved pharmacokinetic properties, and process for the manufacture thereof

FIELD OF THE INVENTION

The present invention relates to a specific pharmaceutical formulation for oral administration of the poorly soluble and therefore hardly bioavailable tubulin inhibitor lndibulin and a process for its manufacture.

BACKGROUND OF THE INVENTION

During mitosis, a cell's DNA is replicated and then divided into two new cells. The process of separating the newly replicated chromosomes into the two forming cells involves spindle fibers constructed with microtubules, which themselves are formed by long chains of smaller protein subunits called tubulins. Spindle microtubules attach to replicated chromosomes and pull one copy to each side of the dividing cell. Without these microtubules, cell division is not possible.

Microtubules therefore are among the most important sub-cellular targets of anticancer chemotherapeutics because they are present in all cells and are necessary for mitotic, interphase and cell maintenance functions (e.g. intracellular transport, development and maintenance of cell shape, cell motility, and possibly distribution of molecules on cell membranes). Compounds that interact with tubulin can interfere with the cell cycle by causing tubulin precipitation and sequestration, thereby interrupting many important biologic functions that depend on the microtubular class of subcellular organelles. Therefore, such compounds can potentially inhibit the proliferation of tumor cell lines derived from various organs. See, e.g., Bacher et al. (2001) Pure Appl. Chem. 73:9 1459-1464 and Rowinsky & Donehower (1991) Pharmac. Ther. 52:35-84.

Accordingly, new, synthetic, small-molecule chemical entities that bind to tubulin, but are neither a substrate of transmembrane pumps nor interfere with the function of axonal microtubules, would strongly increase the therapeutic index in the treatment of malignancies.

A series of synthetic molecules that bind to tubulin are currently being evaluated in the preclinical or early clinical stage. Among them is the synthetic compound, λ/-(pyridine-4-yl)-[1-(4-chlorobenzyl)-indole-3-yl]glyoxyli c acid amide, named Indi- bulin (INN) having the formula C-22H1 ₆ CIN ₃ O ₂ and the following structure:

lndibulin is a synthetic small molecule tubulin inhibitor with significant antitumor activity in vitro and in vivo. It destabilizes microtubules in tumor cells, as well as in a cell-free system. The binding site of lndibulin does not appear to overlap with the tubulin-binding sites of the well-characterized microtubule-destabilizing agents vincristine or colchicine. Furthermore, the molecule selectively blocks cell cycle progression at metaphase.

In vitro, lndibulin exerts significant antitumor activity against a variety of malignancies (e.g., prostate, brain, breast, pancreas, and colon), lndibulin displays high in- ' vivo antineoplastic efficacy in animals. Based on its mechanism of action it is expected to target all types of solid tumors. It is also expected to exhibit antiasthmatic, antiallergic, immuno-suppressant and immunomodulating actions. No neurological symptoms have so far been found in animal experiments. In preclinical expe-

riments in rodents the compound was very well tolerated at highly effective doses. Another advantage for further development is, in contrast to other tubulin-inhibitory compounds, its easy synthesis.

lndibulin is obtained by chemical synthesis as a white crystalline powder. The solubility in hydrophilic solvents is poor, for example it is practically insoluble in water, methanol, ethanol or 2-propanol. Due to these properties, the bioavailability of pure lndibulin is very low. This is also valid for common pharmaceutical dosage forms of lndibulin, e.g. powder, granula, tablets or capsules.

In various organic solvents, for example dimethylformamide, dimethylsulfoxide and N-methylpyrrolidone it shows a sufficient solubility. But these organic solvents cannot be used for application in humans, due to their toxicity.

Highly concentrated (roughly > 50% w/v) organic acids, for example acetic acid or lactic acid are relatively good solvents for lndibulin.

For the improvement of the bioavailability of poorly soluble drugs various technologies are known and proven:

(i) Micronisation of the active ingredient and formulation to oral dosage forms, for example suspensions, capsules or tablets [lit.: R. Voigt, Lehrbuch der Pharm. Tech.; Hagers Handbuch Band 2, Kap. 12.2; Bauer, Frόmming, Fϋhrer, Phar- mazeutische Technologie]. However, these types of formulation lead in the case of lndibulin to a relatively low and insufficient bioavailability and therefore to low plasma levels and no efficacy.

(ii) Dissolution or suspension in organic solvents and surfactants, [lit.: R. Voigt, Lehrbuch der Pharm. Tech; Hagers Handbuch Band 2, Kap. 12.2; Bauer, Frόmming, Fϋhrer, Pharmazeutische Technologie]. The use of surfactants leads to an increased bioavailability of lndibulin in animal tests, but in all cases the formulation were not acceptable for human use, due to the high amount of excipients needed, (iii) Preparation of colloidal suspensions, nano- or microparticle suspensions. For example by using high shear forces the substance is crushed to nanoparticu- late size or the substance is dissolved and afterwards precipitated out of a solvent

- A - mixture. For stabilization often surfactants and/or salts are added. Additionally the viscosity of the suspension can be modified to decrease sedimentation, [see also U.S. Pat. No. 4,826,689]. However, the manufacturing and processing of this type of pharmaceutical formulation is of extremely high complexicity. (iv) Preparation of a drinking solution for Indibulin. For lndibulin it is additionally known that an oversaturated solution in lactic acid can be prepared and orally administered [see also DE 2004 031538.8]. This solution has to be freshly prepared prior to administration, due to stability reasons. Such a solution shows a good bioavailability of Indibulin, but due to the relatively high concentration of lactic acid (5 to 10 % w/v) the amount which can be administered is limited by taste and side effects. Since the concentration of the solution ready to use is approximately 1 mg/ml in 10% lactic acid, the applicable volume is limited to roughly 60 to 80 ml.

Therefore, a strong need exists for a new pharmaceutical Indibulin formulation which exhibits improved bioavailability of Indibulin without showing the disadvantages given in the prior art as mentioned above. Thus, it is an object of the present invention to provide a new pharmaceutical formulation exhibiting improved bioavailability of the pure Indibulin substance. It is a further object of the present invention to provide a respective method for the manufacture of such a pharmaceutical formulation.

SUMMARY OF THE INVENTION

The present invention relates to a pharmaceutical formulation of Indibulin for oral administration comprising a granulate containing micronized Indibulin having a particle size of less than 20 μm for at least 99 vol.-% of the particles, at least one hydrophilic surfactant, and one or more additional capsulation excipients. Further, the present invention relates to a tablet prepared by using said pharmaceutical formulation and a capsule filled with said pharmaceutical formulation, respectively.

The pharmaceutical formulation of Indibulin according to the present invention is based on micronization of Indibulin combined with a granulation procedure using a hydrophilic surfactant (e.g. polysorbate, poloxamer, cremophor) and common

capsulation excipients (e.g. cellulose, starch, highly disperse silicon dioxide, etc). This leads to a sufficient bioavailability and therefore effective plasma levels, which is a significant improvement in formulation of the poorly soluble drug Indibu- Hn. Compared with an ordinary capsule or tablet made of micronized lndibulin the bioavailability as gained by the pharmaceutical formulation of lndibulin according to the present invention is significantly higher. It is on the same level as found for the drinking solution of lactic acid, but avoiding the disadvantages of that formulation with a limit of dosage.

Additionally, a process for manufacturing said pharmaceutical formulation, comprising the steps of micronizing lndibulin to a particle size of less than 20 μm for more than 99 vol.-% of the particles and homogeneously mixing the micronized lndibulin with at least one hydrophilic surfactant and additional capsulation excipients, is provided according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

One aspect of the present invention relates to a pharmaceutical formulation of lndibulin for oral administration comprising a granulate containing micronized lndibulin having a particle size of less than 20 μm for at least 99 vol.-% of the particles, at least one hydrophilic surfactant, and one or more capsulation excipients. Preferably, the micronized lndibulin has a particle size of less than 10 μm for at least 90 vol.-% of the particles. More preferably, the micronized lndibulin has a particle size of less than 10 μm for at least 99 vol.-% of the particles. Even more preferred, the micronized lndibulin has a mean particle size in the range of 2 to 4 μm.

In a preferred embodiment of the present invention, the pharmaceutical formulation comprises lndibulin in an amount of about 10 to about 50 weight %, the at least one hydrophilic surfactant in an amount of about 1 to about 10 weight %, and one or more capsulation excipients in an amount of about 40 to about 80 weight

%, the three constituents always adding up to 100 weight % of said pharmaceutical formulation.

The hydrophilic surfactant is not subject to any particular limitation as long as it is capable of acting as an oil-in-water surfactant. Preferably, the one or more hydrophilic surfactant(s) is/are selected from the group consisting of polysorbates, poloxamers, cremophors and polyalkylene glycols. Any type of polysorbate can be employed, but particularly the polysorbate is selected from polysorbate 20, polysorbate 40, polysorbate 60 or polysorbate 80, more preferred from polysorbate 80. Further, any type of poloxamers can be employed. Poloxamers are surfactant-like block polymers having a central polypropylene glycole moiety which on both terminal ends is connected to a macrogol moiety. Typical poloxamers suited for the present invention are poloxamers 188 and 407, particularly poloxamer 188. Cremophors are non-ionic emulsifiers obtained by causing ethylene oxide to react with castor oil particularly in a molar ratio of about 35 moles to 1 mole. Other common names are polyoxyethyleneglyceroltriricinoleate 35 or polyoxyl 35 castor oil. A typical cremophor is for example Cremophor ^® EL supplied by BASF AG, Germany.

As capsulation excipients those which are common in the art can be suitably used in the present invention. In particular, those capsulation excipients can comprise cellulose such as microcristalline cellulose or a derivative thereof, gelatine, starch, particularly corn starch, and highly disperse silicon dioxide (aerosil). Typically, the capsulation excipients comprise a mixture of microcrystalline cellulose, gelatine, corn starch and aerosil. For example, corn starch and microcrystalline can serve as a filling mass and degradants. Highly disperse silicon dioxide (aerosil) acts in turn to make the mass fluent. Gelatine usually serves as an adhesive to get homogeneous granules.

In a preferred embodiment of the present invention the granules constituting said pharmaceutical formulation are covered by an outer phase composed of a mixture comprising starch, particularly corn starch, highly dispersed silicon dioxide and

magnesium stearate. Such an outer phase properly enables the encapsulation the granules.

A further aspect of the present invention relates to a tablet prepared by using the pharmaceutical formulation according to the present invention. Another aspect of the present invention relates to a capsule filled with said pharmaceutical formulation. Thus, the pharmaceutical formulation according to the present invention can be suitably used as a capsule filling mass. Such a capsule can particularly be a hard gelatine capsule of size 1 or 2 (Ph. Eur.).

In such a capsule according to the present invention the amount of lndibulin as pharmaceutically active ingredient is preferably in the range of about 20 to about 100 mg, more preferably about 30 to about 70 mg, even more preferably about 50 mg per capsule.

A further aspect of the present invention relates to a process for manufacturing said pharmaceutical formulation, comprising the steps of micronizing lndibulin to a particle size of less than 20 μm for more than 99 vol.-% of the particles and homogeneously mixing the micronized lndibulin with at least one hydrophilic surfactant and one or more capsulation excipients. Preferably, the lndibulin is micronized by milling with a jet mill.

In a preferred embodiment of the present invention the micronized lndibulin is homogeneously mixed with corn starch, microcrystalline cellulose and aerosil to obtain a powder mixture, while simultaneously gelatine and polysorbate are dissolved in purified water, and subsequently the powder mixture is moistened with the gelatine-polysorbate solution to obtain a homogeneous granulate by sieving through 0.8 mm sieve.

The process according to the present invention can further comprise the step of encapsulating the granules by mixing with an outer phase forming mixture which in turn is obtained by mixing corn starch, aerosil and magnesium stearate.

Moreover, the process according to the present invention can further comprise the step of filling the pharmaceutical formulation in hard gelatine capsules of size 1 or 2 (Ph. Eur.) or, alternatively, the pharmaceutical formulation is subsequently processed for tabletting.

The figures show:

Figure 1 shows the result of a bioavailability study in humans by treating with a formulation according to the present invention first under fasted and for second treatment under fed conditions afterwards (cf. Example 6 hereinbelow).

Figure 2 shows data of said bioavailability study from a patient who was first treated fed and afterwards treated under fasted conditions (cf. Example 6 hereinbelow).

Figure 3 shows the plasma level from 5 patients treated either with the pharmaceutical formulation according to the present invention as obtained in Example 1 hereinbelow or the drinking solution (Example 4) for comparison (cf. Example 7 hereinbelow).

Examples

The invention is described in the following examples in more detail, but without being limited to those.

Example 1 : Capsule formulation with a strength of 50 mg lndibulin

In order to increase the specific surface of the drug substance lndibulin it is milled via a jet mill. The resulting particle size should be less than 10 μm for more than 90% (volume) of the particles with an average size of about 2 to 4 μm.

The micronized lndibulin is homogeneously mixed with corn starch, microcrystalli- ne cellulose and Aerosil. In parallel gelatine and polysorbate is dissolved in purified water. The powder mixture is then moistened with the gelatine-polysorbate- solution in order to get a homogeneous granulate by sieving through 0.8 mm sieve.

To enable encapsulation the granula is mixed with an outer phase of the capsule mass which is obtained by mixing corn starch, Aerosil and Mg-stearate.

The completed capsule filling mass is then filled in hard gelatine capsules of size 2 (Ph. Eur.)

Composition per unit (Capsule)

Granulate

lndibulin 50.0 mg corn starch 40.0 mg aerosil 3.0 mg gelatine 2.5 mg polysorbate 80 5.0 mg microcristalline cellulose 45.0 mg purified water (USP, EP) q.s.

Outer phase

corn starch 10.0 mg aerosil 2.5 mg

Mg stearate 2.0 mg

hard gelatine capsules of size 2 1

Example 2: Capsule formulation with a strength of 100 mg lndibulin

The manufacturing of a 100 mg strength of lndibulin capsules follows the description in Example 1 , but having a slightly different composition per unit.

Composition per unit (Capsule)

Granulate

lndibulin 100.0 mg corn starch 80.0 mg aerosil 6.0 mg gelatine 5.0 mg polysorbate 80 10.0 mg microcristalline cellulose 90.0 mg purified water (USP, EP) q.s.

Outer phase

corn starch 20.0 mg aerosil 5.0 mg

Mg stearate 4.0 mg

hard gelatine capsules of size 1

Example 3: Capsule formulation with a strength of 50 mg lndibulin using a polox- amer

Composition per unit (Capsule)

Granulate

lndibulin 50.0 mg corn starch 40.0 mg aerosil 3.0 mg gelatine 2.5 mg poloxamere 188 5.0 mg microcristalline cellulose 45.0 mg purified water (USP, EP) q.s.

Outer phase

corn starch 10.0 mg aerosil 2.5 mg

Mg stearate 2.0 mg

hard gelatine capsules of size 2

Example 4: Drinking solution of lndibulin in 10% lactic acid (1 mg/ml)

For preparation of the drinking solution, a certain amount of the pure active compound is dissolved in lactic acid 90% (Ph. Eur.). Afterwards the obtained solution is diluted with an aqueous solution of glucose and passion fruit flavour to the applicable volume and concentration. The final solution is oversaturated and therefore only stable for 2 hours. Therefore the drinking solution has to be prepared directly prior to administration.

The applicable formulation contains 60 ml of an aqueous drinking solution of lndibulin with a concentration of 1 mg/ml. Glucose and passion fruit flavour are used to modify the taste to make swalling easier.

Composition of the solution:

lndibulin 60.0 mg lactic acid 90% 7269.2 mg glucose Ph. Eur. 5532.5 mg passion fruit flavour 96.9 mg pur. water 50503.7 mg

Example 5: Bioavailability studies on animal

Pharmacokinetic studies were carried out in Cynomolgus monkeys, comparing the bioavailability of lndibulin from three different formulation for oral administration and for reference from an intravenously administered solution of lndibulin in solu- tol ^® /propane diol:

1. formulation according to the present invention as obtained in Example 1 (50 mg)

2. standard capsule of micronized lndibulin (50 mg)

3. drinking solution of lndibulin in 10% lactic acid, as described in Example 4

4. intravenously administered solution of lndibulin in solutol ^® /propane diol.

The results show a significant improved bioavailability for the formulation according to the present invention compared with an ordinary capsule formulation. In comparison with the drinking solution containing lactic acid, the bioavailability from the formulation according to the present invention as obtained in Example 1 is lower, but this is compensated by the better tolerability and the higher possible dosing as exemplified by said Example 1 ; cf. Table 1 hereinbelow (AUC = area under curve).

Table 1 :

* Plasma samples from intravenously administered animals were only withdrawn until 4 hours and, thus, only AUC _0-4 could be calculated

Example 6: Bioavailability studies in humans

The formulation of Example 1 was tested in Phase I studies in humans. Patients were treated with the lndibulin capsules under fed and fasted conditions to evaluate the influence of administration prior or after a meal.

To obtain relevant plasma levels it seems to be better to administer the capsules under fed conditions. Fig. 1 shows treatment first under fed and for second treatment under fasted conditions afterwards. Good bioavailability can be observed in the first treatment whereas after second treatment no plasma level was found.

Fig. 2 shows data from a patient who was first treated fasted and afterwards treated under fed conditions. Again, if patient was fasted, no plasma level of lndibulin can be found, but under fed conditions significant plasma levels were observed.

Example 7: Comparison of the bioavailability of Example 1 (capsule formulation according to the present invention) and Example 4 (drinking solution) in Phase I studies in humans

Fig. 3 shows the plasma levels of lndibulin from three patients (patients 104, 105 and 107) treated with 40 mg via the lactic acid drinking solution versus two patients (patients 116 and 117) treated with 50 mg via the capsule formulation according to the present invention.

The plasma levels of both formulation were within the same range taking the standard deviation into account, therefore no significant differences can be found. The bioavailability can be stated to be similar for both formulations.