THERAPEUTIC COMPOSITIONS WITH GALACTITOL AS CARRIER

Abstract: An improved pharmaceutical or veterinary composition contains galactitol as carrier for the therapeutic agent. Preferred therapeutic agents include anti-infective and anti-cancer drugs, preferably cytotoxic agents and lymphokines. One example is a lyophilized composition of about 20 parts by weight of cyclophosphamide, taken as the anhydride, about 5 to 21 parts by weight of galactitol as excipient, and about 1.4 to 3 parts by weight of water. Preferably, the amount of galactitol is 15-21 parts by weight. The galactitol enhances the chemical and physical stability of the drug and allows faster reconstitution of the formulation in water than mannitol.

Description: This invention relates to a pharmaeutical or veterinary composition which is readily reconstitutable in water. In particular, this invention relates to a composition which contains galactitol as carrier for cyclophosphamide. Cyclophosphamide is a widely synthetic antineoplastic drug and immunosuppressive agent for the treatment of a variety of malignant and non-malignant diseases. It exists in two forms: anhydrous and monohydrate. The monohydrate form is employed in processing for clinical applications because the anhydrous form is not stable. At comparatively low relative humidity, the monohydrate will lose the water of hydration. Cyclophosphamide has been made into unit dosage compositions by mixing the dry powder with sodium chloride to provide isotonicity when the product is reconstituted. The disadvantages of the dry powder blend include formation of mixture of powders which are not pharmaceutically elegant, i.e., not of uniform appearance and/or consistency, contaminated with insoluble particulates, and having prolonged dissolution time upon reconstitution into a solution. The disadvantages of dry powder formulations have been addressed by lyophilizing an aqueous solution of the formulated material, to obtain a solid composition of improved stability. The advantages of lyophilization are (1) the solution of the drug can be filtered to remove particulates, and (2) the time required for reconstitution is significantly reduced. The lyophilized product also appears to be more stable to heat. One patent which specifically addresses the lyophilization of cyclophosphamide is U.S. Patent No. 4,537,883 issued August 27, 1985. The formulation of this patent includes cyclophosphamide with mannitol as excipient and a range of moisture content of 1.25 to 2 parts by weight of water. The composition is shown to have improved physical stability over the dry formulation. It also shows enhanced appearance over the dry formulation and over lyophilizates incorporating lactose and other excipients. It is an object of the present invention to identify another excipient which would yield a physically and chemically stable lyophilizate as an alternative to mannitol, and to identify a carrier for lyophilized pharmaceutical compositions which allows for faster reconstitution in water than mannitol. Surprisingly, of the other excipients besides mannitol, only galactitol exhibits the physical and chemical stability necessary for a feasible commercial product. Accordingly, the present invention provides the use of galactitol as a carrier for cyclophosphamide. In another aspect, the invention provides a method for making a therapeutic composition of cyclophosphamide which includes the incorporation of galactitol as a carrier. In a further aspect, the invention provides a hydrated, rapidly reconstitutable lyophilizate composition, exhibiting enhanced chemical and physical stability as well as uniform consistency and appearance, which comprises about 20 parts by weight of cyclophosphamide, taken as the anhydride, 5 to 21 parts by weight of galactitol, and 1.4 to 3 parts by weight of water. The composition may be reconstituted in vials with water or other suitable diluent to provide solution for oral or parenteral administration to patients. Whereas U.S. Patent No. 4,537,883 discloses that only use of mannitol as the major excipient results in the desirable physical properties, applicant has discovered that galactitol may be used alone as excipient or, if desired, in combination with a minor amount (less than 50% by weight) of mannitol, to achieve outstanding physical, aesthetic, and chemical properties. The invention which is contemplated herein encompasses using galactitol as the predominate carrier in pharmaceutical compositions. A lyophilized composition of cyclophosphamide and galactitol exhibits both chemical and physical stability and an enhanced appearance. In addition, using galactitol results in faster reconstitution in water than using mannitol as carrier. Galactitol is a polyol of the formula: It is described in greater detail in the Merck Index. The words "predominantly comprising galactitol" as used herein refer to the carrier being comprised of at least 50% by weight of galactitol. The relative amount of galactitol to CPA in the present formulations is limited by solubility and cannot exceed as high as 1.05:1 galactitol:CPA as the anhydride. The formulation herein may contain other ingredients besides a carrier, such as a detergent. In addition, the formulation may contain a small amount of buffer which will provide a physiological pH if the mixture is reconstituted. The chemical stability of the composition for purposes herein is measured by its ability to retain its original potency after being exposed to a 37°C temperature for one week. The physical stability of the composition for purposes herein is measured by its ability to retain its original physical properties (including color, dissolution rate, and consistency and uniformity of appearance) after exposure to a 37°C temperature for one week, which is expected to correspond to being stable at 27 ± 3°C for one year, and at 22 ± 3°C for 3-5 years. Exposure of the composition to 37°C is not uncommon for short periods during transportation or warehouse storage. The enhanced appearance of the composition herein is measured by the uniformity of its consistency and appearance such as color, i.e., by the "pharmaceutical elegance" of the product. Pharmaceutical elegance refers to a visually pleasing product, a criterion commonly used by those skilled in the art to gauge the market quality of the pharmaceutical. In more quantitative terms, the pharmaceutically elegant product has a uniform appearance, i.e., when examined from outside a glass vial or other container in which the product is held, is essentially free from blisters, bubbles or voids which individually do not exceed 2 mm in equivalent diameter. A uniform appearance and consistency also refers to a cake with uniform color, uniform moisture content, and no fissures or flaking as evidenced by plate-like flakes and granular odd-sized agglomerates. While it is generally acknowledged that the visual appearance of cyclophosphamide product may not affect its pharmaceutical efficacy, purchasers and dispensers of pharmaceuticals expect lyophilized products to have pharmaceutical elegance which otherwise dry, powder-filled cyclophosphamide conspicuously lacks. The therapeutically active agent herein, CPA, is an anti-cancer agent with the chemical name: 2-[bis-(2-chloroethyl)amino]-tetrahydro-2H-1,3,2-oxazaphosphorine-2-oxide monohydrate. CPA is described in greater detail in U.S. Patent No. 3,018,302 and in the Merck Index. The co-carrier which may be employed along with galactitol in an amount up to 49% by weight of total carrier must be water soluble, must not react with the therapeutic agent and must be stable. This carrier also is preferred non-sensitive (i.e., non-hygroscopic) to water. Examples of such co-carriers include lactose, mannitol, and albumin such as human serum albumin, but preferably mannitol. Most preferably, no co-carrier is employed. Lyophilization of an aqueous solution of CPA with the galactitol excipient under the conditions specified below results in a CPA product which has uniform CPA hydrate integrity and good shelf-life stability. "Hydrate integrity" means that the bound moisture content of the CPA hydrate is sufficient to provide stability of the product, which content is hypothesized to be in the range from 5% to 7% by weight of the CPA hydrate; and "uniform" means that substantially all vials in a batch of at least several hundred vials are lyophilized to within a moisture range of from 1.4 to 3 parts by weight of water per about 20 parts by weight of CPA taken as the anhydride. The criticality of maintaining the CPA hydrate integrity is premised on the knowledge that the moisture content of the CPA product cannot be reduced below about 1.4 parts, because the CPA will degrade, and cannot exceed about 3 parts for the same reason. The particular proportioning of this moisture relative to each component of the product is not narrowly critical. By a "dosage amount" of CPA is meant a specified amount of pure CPA (anhydrous), which may, if desired, include an overage, preferably up to 10%, and galactitol , optionally with a co-carrier such as, preferably, mannitol. The composition is in a single dose vial having a size sufficient to allow reconstitution with water or other suitable diluent such as, e.g., bacteriostatic Water for Injection to yield the appropriate concentration of CPA for administration. Typical dosage amounts herein are 100 mg, 200 mg, 500 mg, 1 g and 2 g of CPA, taken as the anhydride (not including an overage). An equivalent amount by weight of galactitol vis-a-vis CPA is preferred as excipient. The amount of water effective for reconstitution and administration may range broadly, but is preferably 5 to 100 ml, more preferably 15-71 ml. A typical dosage amount is 500 mg CPA, taken as the anhydride, and 525 mg galactitol reconstituted in 20 ml water, or 500 mg CPA, taken as the anhydride, and 525 mg galactitol reconstituted in 25 ml water. The galactitol in the formulation herein may be replaced, in part, by a minor amount of mannitol as excipient, with no adverse effects. By minor amount is meant that no more than 49% by weight of the galactitol can be so replaced. The amount of galactitol present in the formulation may range from 5 to 21 parts by weight of the final formulation, given 20 parts by weight of CPA, taken as the anhydride. If the amount of galactitol exceeds about 21 parts the product is no longer soluble. If the galactitol amount is too low, however, the product will be harder to lyophilize. Preferably the amount of galactitol employed is 15 to 21 parts by weight, more preferably 20-21 parts by weight. The cake of the CPA product has a uniform, near-white color and is essentailly free of flaking or granular agglomerates. As mentioned above, the CPA product herein contains 1.4 to 3 parts by weight of water per 20 parts by weight of CPA, taken as the anhydride. Such a product provides the requisite shelf-life stability which is evidence that the integrity of the CPA hydrate is maintained. Moisture determination is made by any standard method, as, for example, described in Edwards, Freeze-Drying Handbook , by Terence W. G. Rowe and John W. Snowman, published by Edwards High Vacuum:Crawley, England (1976). The size of the vial chosen is determined by the dosage amount, the basic dosage amount of CPA (e.g., 500 mg of CPA) being provided in vials which can hold 20 ml to 50 ml, and most preferably 25 or 30 ml. Most preferred for a basic dosage amount is a 30 ml vial in which 15 ml of solution is added containing 500 mg of CPA (anhydride), about 525 mg of galactitol, and a quantity of water or other suitable diluent sufficient (QS) to bring the volume to 15 ml. Precisely how the lyophilization cycle is monitored is not critical and this may be effected in various ways, for example, as suggested in Freeze Drying Processes for the Food Industry , by Gutcho, M. H., published by Noyes Data Corporation, New Jersey (1977). The essential elements of the cycle are the monitoring of the temperature of the shelves, the temperature of the material in the vials, and the time periods during which the temperature and pressure conditions are controlled. The chamber is evacuated after the vials are frozen and a temperature from -20°C to -50°C is maintained for enough time to ensure that all the vials are at substantially the same temperature. The temperature may be determined by probes in vials racked in a tray placed on a shelf of the lyophilization chamber. A higher temperature may be used if time is not a factor, but temperatures much warmer than -20°C are not economical. A pressure of no more than 1.33322 x 10² Pa is essential, and it is preferred to use a pressure in the range from 1.33322 to 0.66661 x 10² Pa, which may be effected with any conventional high-quality vacuum pump. The time during which the chamber is evacuated is not critical as long as the material in the vials is frozen solid, a typical evacuation period ranging from 10 minutes to one hour. The shelf temperature is raised gradually, the rate being controlled by a control means such as a cam, or microprocessor, or by manual control, so that the shelf temperature reaches a finish-drying temperature no higher than that which deleteriously affects the CPA material. Too high a temperature causes the material to melt or otherwise be degraded, adversely affecting both its pharmaceutical efficacy and elegance. The vacuum is maintained throughout the drying cycle, and in all cases should be sufficient to produce dried material with a moisture content of less than 2% by weight based on total net content weight of the dried material (corresponding to less than 1.3 parts by weight water per 20 parts by weight of CPA). The period of time will depend upon the dosage amounts in the vials, the size and configuration of the vials, and the number of vials in an assembly in the particular chamber being used. After the vials have been dried to the aforespecified degree in the first stage of the process, the lyophilized material is rehydrated by introducing water vapor into the chamber. A fine spray of water may be jetted intermittently into the chamber in an amount sufficient to raise the moisture level in the chamber to at least 75% relative humidity. Any source of pure water may be used, but clean steam is preferred because it is convenient and lends itself to precise control. Sufficient clean steam is introduced over a period of time sufficient (generally in the range from five minutes to two hours) to attain a relative humidity of at least 75%, preferably 75-80%, in the chamber. The humidity is maintained at this level until it is determined that the material in the vials has absorbed enough moisture to meet the water content range specified above. The exact relative humidity of the chamber for rehydration is not critical if it is at least 75%, it being evident that rehydration will take place when the vapor pressure in the chamber is greater than that of the lyophilized material. The relative humidity is preferably 75-80% because at lower humidity the rehydration is impractical. Rehydration of the lyophilized material obtained after the first stage may be effected not only by using steam, but also by the following methods: A. The vials of lyophilized material are removed from the lyophilization chamber and placed in a constant humidity cabinet at 75-80% relative humidity for rehydrating the material. The material is held in the constant humidity cabinet until it is determined that the material in the vials has absorbed enough moisture to meet the critical moisture content of CPA product. The vials of rehydrated CPA product are then removed from the constant humidity cabinet and stoppered. B. The vials of lyophilized material are placed in a chamber over a constant humidity solution with a relative humidity value of 80-90%. The material is held in the chamber over the solution until it is determined that the material has absorbed enough moisture to meet the specification of the critical moisture content of CPA product. At the end of the rehydration step, the probes in the vials read about +20°C, without exceeding about +25°C for any significant period of time. In an analogous manner, the process may be carried out in vials in which a dosage amount includes less than an equivalent weight of the excipient. The following examples are provided to illustrate further the embodiments of the invention. In the examples, all parts and percentages are by weight and all temperatures are in degrees Centigrade unless otherwise noted. EXAMPLE 1 A preparation of a 500 mg/vial dosage amount of CPA hydrate with 525 mg/vial galactitol for 15 ml/vial Water For Injection (WFI) was prepared as follows: A total of 29.60 g of cyclophosphamide monohydrate and 28.88 g of galactitol were added to 700 ml of WFI and mixed vigorously for one hour using a high-speed mixer. The resulting solution was clear and colorless. The solution was brought to volume of 825 ml with WFI, and the solution was mixed for five minutes. The result was a clear, colorless solution at pH 3.95. The solution was filtered through a 47 mm Pall NR 0.2 µm membrane using a 47 mm Millipore™ Millitube™ filter holder. The solution, which filtered easily at 40 psi, was very clear and colorless. The solution was dispensed in 53 x 30-ml Flint, Type I, molded vials (Wheaton) at 15 ml/vial, with closures placed in lyophilizing position, racked in trays and placed on the shelves of a lyophilization chamber. In the first stage of lyophilization, the product solution in the vials was frozen to a temperature of about -20°C, and after all the probes reached the desired temperature, this temperature was maintained for about two hours. The condenser was chilled to about -50°C and the chamber was evacuated, the vacuum being adjusted with a N²-sweep to read in the range from 1.33322 to 1.33322 x 10² Pa. The shelves were then warmed to about +22°C, and when the probes in the vials read about +20°C, lyophilization cycle was continued for about 4 to 24 hours without exceeding about 25 ± 2°C for any significant period of time. In the second stage, rehydration of the lyophilization material was accomplished by introducing water vapor directly into the chamber until it reached about 75-80% relative humidity at 25 to 30°C, the water being in the form of clean steam passed through a sterile microbiological filter. When the chamber had reached an equilibrium value of about 80% to about 85% relative humidity, this humidity was maintained until the product acquired a moisture content of about 3.60% by weight based on the total weight of the formulated product, with 3.3% being equivalent to 1.3 parts per 20 parts CPA. The moisture level was monitored periodically by removing representative samples (vials) in the lot and carrying out the standard Karl Fischer analysis. Before rehydration all vials possessed solid, uniform snow-white cakes. The initial moisture content was 0.1% by weight, based on CPA as the anhydride. After rehydration the moisture content and appearance were as follows: Hours of Rehydration % Water (by weight, based on net CPA product) Appearance 1 0.90 Uniform snow-white cakes 2 1.36 Uniform snow-white cakes 4 2.10 Uniform snow-white cakes 6 2.64 Uniform snow-white cakes 8 3.10 Uniform snow-white cakes 10 3.60 Uniform snow-white cakes The minimum moisture requirement is 3.30% (1.3 parts by weight per 20 parts by weight CPA). The remaining samples were placed on a stability testing program in controlled atmosphere rooms at a temperature of 24 ± 2°C, and at 75% relative humidity at temperatures of 37°C and 30 ± 2°C. Samples of vials (3 for each test interval) were taken at random from each batch and analyzed at the intervals indicated, and the results recorded in the following Table I. The assays were performed according to the procedure described in the USP monograph for Cyclophosphamide for Injection. The variation in assay results is within the specified range of 90-110% CPA set forth in the USP monograph. Degradation, indicating a lack of adequate chemical stability, would be evidenced at the end of a test period by a significantly lower assay than the initial assay. As will be evident from the representative tests set forth below, there was no evidence of degradation at the end of two months at 30 ± 2°C. The reconstitution time was ten seconds as opposed to at least one minute for formulations containing only mannitol as carrier. EXAMPLE II - Use of Excipients Other Than Galactitol 1. A total of 535 mg per vial of CPA, taken as the anhydride, was mixed with 950 mg per vial of one of the following excipients (A) xylitol, (B) inositol, (C) mannose, (D) maltose, or (E) fructose to 85% (320-340 ml) of total QS volume (15 ml). Lots A-D were stirred vigorously for one hour using a highspeed mixer, and Lot E was stirred for 15 minutes. The solutions were filled to 375 ml with WFI, mixed for 10 minutes, and filtered through a membrane at 40 psi (0.12 mPa). Twenty-two vials per lot at 15 ml per vial were placed into an Edwards lyophilization chamber and lyophilized as described in Example I. The results are provided in Table II. Lot No. Appearance A Totally melted and glazed, cake shrunken to the vial bottom; all vials rejected B Totally melted and glazed, cake shrunken to the vial bottom; all vials rejected C Shrunken and molten glass appearance; all vials rejected D All vials possessed solid, uniform snow-white cakes; no rejects occurred E Clear, melted, wet and sticky cakes; poor appearance When Lot D was tested for stability it was found to lose its potency and solubility characteristics after exposure to 37°C for one week. 2. A total of 500 mg per vial of CPA, taken as the anhydride, was mixed with one of the following excipients: (A) 500 mg/vial of dextran and 125 mg per vial of sucrose, (b) 500 mg/vial of maltodextrin (Grain Processing Corp., Miscatine, Iowa), (C) 1000 mg/vial of dextran, or (D) 250 mg/vial of maltodextrin. A total of 9.70 g of CPA was mixed with the appropriate amount of excipient in 230 ml of WFI and mixed vigorously with a high-speed mixer. The solutions were brought to the volume of 270 ml with WFI and mixed for 2-3 minutes. This mixture was filtered through a membrane and dispensed in 17 vials per lot. The vials were placed in a lyophilization chamber and lyophilized as described in Example I. The results before and after rehydration are shown in Table III, where HPLC analysis was made after storage for 6.5 days at 37°C and 75% relative humidity, and % moisture is expressed by weight based on CPA as the anhydride. The mixtures were processed as described above, and the results of appearance and stability after rehydration are indicated in Table IV, with HPLC analysis made after storage for 6.5 days at 37°C and 75% relative humidity. Seven Day Stability Results (Storage at 37°C/75% Relative Humidity) Lot No. Appearance HPLC Analysis (% potency) A Shrunken, almost melted, orange-brown cakes; poor appearance 75 B Snow-white, slightly shrunken cakes 88.6 C Snow-white, uniform cakes; good appearance 75.1 D Snow-white, shrunken cakes 96.8 3. A total of 500 mg per vial of CPA, taken as the anhydride, was mixed with one of the following excipients: (A) 250 mg per vial maltodextrin, or (B) 500 mg per vial maltodextrin. The mixtures were processed as described above and mixed for five minutes, and the results of appearance before and after rehydration and stability after rehydration are indicated in Table V, with HPLC analysis made initially and after two-weeks' storage at 37°C and 75% relative humidity. Lot No. Appearance HPLC Analysis (% potency) 0 2 weeks A Solid, uniform white cake before rehydration 97.0 92.4 B Solid, uniform white cake before rehydration; shrunken off-white cake after two-weeks' storage at 37°C 94.4 N/D The results indicate that of all the above-tested excipients, which include monosaccharides, disaccharides, and polysaccharides, only galactitol successfully yielded a product on a caliber with mannitol with adequate chemical and physical stability as defined herein and uniform appearance and consistency. Yet, formulations using as excipients dextran and sucrose, maltodextrin, and dextran met the definition of "stability" in U.S. Patent No. 4,537,883 and would have been declared as acceptable excipients under the criteria in that patent. Furthermore, the lyophilizate formulated with galactitol instantly reconstituted in water, whereas the lyophilizate formulated with mannitol alone required about one minute for reconstitution in water.

Claims: A hydrated lyophilizate composition, having enhanced chemical and physical stability and uniform appearance and consistency, comprising about 20 parts by weight of cyclophosphamide, taken as the anhydride, 5 to 21 parts by weight of galactitol, and 1.4 to 3 parts by weight of water. A composition as claimed in Claim 1 wherein the amount of galactitol is 15 to 21 parts by weight. A composition as claimed in Claim 1 or Claim 2 wherein no more than 49% by weight of the galactitol is replaced with mannitol. The use of galactitol as a carrier for cyclophosphamide. A method of making a therapeutic composition of cyclophosphamide which includes the incorporation of galactitol as a carrier.

Inventors: FRANCIS, DANIEL LEE
Applicants: CETUS-BEN VENUE THERAPEUTICS
Application year: 1987
Main classification: A61K47
IPC codes: A61K9, A61K47, A61K38, A61K45, A61P35