CRYSTALLINE ALKYCYCLINE DERIVATIVE
The present invention relates to a crystalline form of a useful drug that is an alkycycline derivative. US-A-5, 532,218 discloses 4-demethoxy-3' -deamino-3' - azιridmyl-4' -methansulfonyl daunorubicin, its preparation and its usage as an anticancer agent, which is referred to as "aziridino alkycycline" hereinafter and is represented from the formula la
The compound la intercalates into DNA via the chromophore and alkylates guanine at N7 position in DNA minor groove via its reactive moiety on position 3' of the ammo sugar. Compound la is able to circumvent the resistance to all major classes of citotoxics, indicating that the compound belongs to a new class of anticancer drugs, and was described and claimed in US-A-5, 532, 218. We have now surprisingly found a crystalline form of aziridine alkycycline useful as bulk drug, particularly stable and suitable for pharmaceutical preparations . The present invention is relating to a crystalline aziridine alkycycline having excellent stability, to its preparation, to the pharmaceutical compositions containing it and to their use in cancer treatment.
Another aspect relates to samples crystalline aziridine alkycycline having a % purity > 85%, preferably >96po. Description of figures
Figure 1. shows the powder X-ray diffraction spectrum of crystalline aziridine alkycycline' according to the present invention, with peak intensity (counts) as the vertical axis and angle (°2Θ) as the horizontal axis. X-RAY Powder Diffraction Powder X-ray diffraction was performed using a Philips analytical X-ray diffractometer type PW1800, operating under PC-APD diffraction software. The system used a copper X-ray source maintained at 50 kV and 30 mA to provide CuKα, emission of 1.5406 angstroms and CuK : emission of 1.5444 angstroms, intensity ratio o-i /o.20.500, irradiated length 10mm. Data were collected from 2 to 40° 2Θ using a step scan of 0.02° /point with a one second/point counting time. The x-ray powder diffraction pattern for crystalline aziridine alkycycline (Figure 1) shows a crystalline structure with distinctive peaks shown in the following table I:
TABLE I
Crystalline aziridine alkycycline of the present invention can be produced by crystallizing aziridine alkycycline from an aprotic organic solvent or from a mixture of aprotic organic solvents. Specifically, crystalline aziridine alkycycline can be produced by dissolving amorphous aziridine alkycycline an aprotic organic solvent solution, partially removing the solvent from the solution at a temperature of up to 45°C (external bath temp.) under vacuum and crystallizing aziridine alkycycline at a temperature of from 0° to 20°C.
Preferably the solution of aziridine alkycycline is kept under inert atmosphere, more preferably under nitrogen. Suitable aprotic organic solvents include ketones, cyclic and linear ether, esters and a mixture thereof.
Optionally an anti-solvent can be added, for example n- hexane .
Ketones and esters include straight or branched
C^-C6 ketones, such as acetone, 2-butanone, 3-pentanone, 4- methyl-2-pentanone, and C2-C4 esters such as ethyl acetate, l-butyl acetate and t-butyl acetate.
Ether solvents include straight or branched C4-Ce ethers such as diethyl ether, methyl t-butyl ether and cyclic ethers having 5 or 6 membered ring such as tetrahydrofurane and 1,4-dιoxane.
Preferred solvents are tetrahydrofurane and ethyl acetate. The amount of the solvent dissolving aziridine alkycycline is, for example, 10 to 1000 parts by weight per part of aziridine alkycycline. Preferably, the amount of the aprotic organic solvent may be 10 to 100 parts by weight, more preferably 10 to 50 parts by weight, still more preferably 10 to 20 parts by weight per part of aziridine alkycycline. The temperature of the solution of aziridine alkycycline at which the solvent is removed (external bath temp.) under vacuum may be, for example, up to 45°C, more
preferably of from 25°to 35°C. The solution from which the aziridine alkycycline is crystallized is held at a temperature of 0°to 20°C during the crystallization. The period of time for crystallizing the aziridine alkycycline is not limited, but preferably it is m the range of 30 minutes to 1 day.
Seed crystals of crystalline aziridine alkycycline may be added into the solution to accelerate crystallization. The thus obtained crystals may be recovered by common procedures, for example by filtration under reduced pressure of by centrifugal filtration, followed by drying the crystals, to obtain the crystalline aziridine alkycycline of the present invention. Occasionally, the crystalline aziridine alkycycline bears the aprotic organic solvent used for the crystallization. In that case, the solvent may be removed by drying the crystals .
The drying treatment can be carried out m a conventional manner, for example by subjecting the crystals to a reduced pressure at a temperature of from 0° to 50°C, preferably from 20 to 40°C. The pressure m drying may be, for example, less than 200 mHg, preferably 1 to 50 mmHg. The drying treatment can be monitored by measuring the amount of solvent m the crystals. Usually, the drying will be completed m 24 to 72 hours.
A further aspect of the present invention is to provide a method of treating a mammal including humans, suffering from a neo-plastic disease state comprising administering to said mammal a pharmaceutical composition obtained starting from the crystalline aziridine alkycycline of formula la as defined above amounts effective to produce a anti-cancer effect.
By the term * administered λ or * administering" as used herein is meant parenteral and /or oral administration. It will be appreciated that the actual preferred method and
order of administration will vary according to, _nter -ilia, the particular formulation of the aziridine alkycycline of formula la being utilized, the particular tumors being treated, and the particular host being treated. In the method of the subject invention, for the administration of the aziridine alkycycline formulation, the course of therapy generally employed is from about 0.1 to about 200 mg/m2 of body surface area. More preferably, the course therapy employed is from about 1 to about 50 mg/m2 of body surface area.
The anti-neoplastic therapy of the present invention is m particular suitable for treating breast, ovary, -.ung, colon, kidney and brain tumors in mammals, including humans . The present invention will be described detail below, referring to Examples, which are not limitative of the present invention. Example 1 Crystalline 4-demethoxy-3' -deamιno-3' -azιrιdmyl-4 ' - methansulfonyl daunorubicin (aziridine alkycycline) Amorphous 4-demethoxy-3' -deamιno-3' -azιrιdmyl-4 ' - methansulfonyl daunorubicin (aziridine alkycycline, prepared according to example 2 of US-A-5, 532,218) was dissolved m tetrahydrofurane (THF) or ethylacetate (AcOEt) , that were then completely removed by evaporation under different conditions. The resulting crystals were collected and analyzed, x-ray powder diffraction pattern is shown m Figure 1. The following table II summarizes the conditions of the different experiments.
Table II
Example 2
Crystalline aziridine alkycycline 500 mg of amorphous aziridine alkycycline were dissolved in tetrahydrofurane (10 ml), the solution was cooled at 0°-2°C and 40 ml of hexane were added in, half an hour. After 90 minutes stirring, the precipitated crystals were collected by filtration and dried at 20°C for 24 hours under vacuum. The obtained crystals (390 mg) showed the same x-ray powder diffraction pattern of those prepared in Example 1. Example 3 Crystalline aziridine alkycycline a) Operating as described in Example 2, but starting from 100 mg of amorphous aziridine alkycycline dissolved in ethylacetate (11 ml) and adding 33 ml of hexane, there were obtained 70 mg of crystals with the same x-ray powder diffraction pattern of those prepared in Example 1. b) Operating in the same way, but starting from 500 mg of amorphous aziridine alkycycline dissolved in ethylacetate
(55 ml) and adding 165 ml of hexane, there were obtained 330 mg of crystals. Example 4
Crystalline aziridine alkycycline Operating as described in Example 3 b, but keeping the solution at room temperature, there were obtained 250 mg of crystals with the same x-ray powder diffraction pattern of those prepared m Example 1. Example 5 Crystalline aziridine alkycycline
Operating as described Example 4, but employing 6 ml ethylacetate and stirring at a temperature of 4°C for three hours without adding hexane, there were obtained 120 mg of crystals with the same x-ray powder diffraction pattern of those prepared in Example 1. Example 6
Crystalline aziridine alkycycline
1500 mg of amorphous aziridine alkycycline were dissolved in ethylacetate (100 ml) and the solvent was removed under vacuum at 27°-30°C (external bath temp.); the resulting suspension was filtered and the collected crystals were dried at 20°C for 24 hours under vacuum. The obtained crystals (1350 mg) showed the same x-ray powder diffraction pattern of those prepared m Example 1. Example 7
Crystalline aziridine alkycycline
31 g of amorphous aziridine alkycycline were dissolved m ethylacetate (3.5 1) under nitrogen atmosphere, the solvent was removed under vacuum at 28-30°C. The resulting suspension was maintained at 0°-4°C for one hour and then filtered; the collected crystals were dried at 30°C for about 40 hours under vacuum (25-50 mmHg) . The obtained crystals (28 g, 90° yield) showed the same x-ray powder diffraction pattern of those prepared m Example 1.
The crystals resulting from examples 1 to 7 were also analyzed with HSM (Hot Stage Microscopy) [THMS 600 Linkam + optical microscopy Reichert] and Thermogravimetric Analysis (TGA) ; the resulting data are shown in tables III and IV. Table III -Crystalline aziridine alkycycline - TGA 2°C/min
Note: When Temp, was > 150°C, sample degradation was observed.
Table IV- Crystalline aziridine alkycycline, HSM 10°C/mιn (thermomicroscopy)