|Title of Invention||
A PROCESS FOR THE PREPARATION OF LOBAPLATIN TRIHYDRATE
|Abstract||Lobaplatin trihydrate constitutes a new and advantageous form of a platinum complex having an antitumour effect.|
British patent application 2 024 823 discloses, for example, platinum complexes of 11 -bis(aminomethy[)-cyclobutane. These compounds are recommended for the treatment of cancer.
The compounds of this invention have a good anti-tumour effect (for example in vitro in AH 135 tumour, B 16 melanoma, colon 115; in vivo for example in P 388 leukemia in mice). Moreover the compounds of this invention display low toxicity, in particular they have no cumulative toxicity and have no nephrotoxicity. Moreover bone marrow toxicity is low.
European Patent 324,154 describes platinum complexes of trans-1,2-bis(aminomethyl)cyclobutane as being compounds with a potent antitumour effect. In particular cis-[trans-1,2-cyclobutane bis(methylamine)-N,N']-[(2S)-lactato-O1 ,O2]-platinum(ll) (INN: lobaplatin) has been found more effective and better tolerated than cisplatin (R. Voegeli etal. Drugs of the Future 1992, 17, 883-886 and R. Voegeli et al., J. Cancer Res. Clin. Oncol., 1990, 116, 439 - 442).
The chemical synthesis of lobaplatin has hitherto concentrated on the anhydrous substance. As set out in the synthesis example (EP 324,154, Example 1a), the aqueous reaction solution was evaporated, taken up in methanol, stirred with active charcoal and the filtrate crystallised after mixing with diethyl ether at refrigerator temperature. The crystals obtained in this manner were vacuum dried. Using this method, it is difficult to reproduce the purity and content parameters and to adjust them within the prescribed limits. Moreover the substance is hygroscopic and causes difficulties in dosage and pharmaceutical formulation because of adhesion.
It is the object of the invention to provide a new form of lobaplatin which is simpler and safer to handle and which displays improved quality. It is, moreover, important to provide hospital staff with a pharmaceutical form that is easy to handle since handling cytostatic agents presents difficulties in respect of industrial hygiene. It has now been found that the trihydrate form of lobaplatin meets the above requirements to a great extent.
Hydrate forms of lobaplatin have not been described to date. A targeted investigation has shown that lobaplatin trihydrate surprisingly displays substantial advantages.
The present invention describes the production of lobaplatin as a trihydrate and the resultant, unexpected advantages: easier synthesis, reduction of proportion of by-products, no hydroscopy, reproducible adjustable water content, improved storage stability, better dosability, better pharmaceutical processability. The following pharmaceutical formulations may, for example, be prepared from lobaplatin trihydrate: tablets, capsules, coated tablets, sustained release formulations, lyophilisates, injection or infusion solutions.
The following investigations are intended to confirm these advantages: 1. Synthesis
The lobaplatin synthesised in complete analogy with Example 1a of EP 324 154 up to the dropwise addition of the dihydroxo-platinum complex into the aqueous lactic acid solution is now worked up in a substantially simpler manner:
After concentrating the aqueous reaction batch, raw lobaplatin crystallises out and is recrystallised from a mixture of water / acetone with addition of a little active charcoal. The crystals obtained in this manner as trihydrate are dried on the air at room temperature or slightly elevated temperature (see example).
An analytical profile was made out of 15 batches - 7 batches manufactured as anhydrous substance, 8 as trihydrate - that displays the pronounced superiority of the substance synthesised as trihydrate.
Elementary analysis a) Anhydrous:
Calculated Found Deviation
C 27.21% 25.86% 5.0%
H 4.57% 4.82% 5.5%
N 7.05% 6.65% 5.7%
Pt 49.10% 46.39% 6.1%
Calculated Found Deviation
C 23.95% 23.92% 0.1%
H 5.36% 5.25% 2.1%
N 6.21% 6.06% 2.3%
Pt 43.22% 43.44% 0.5%
Deviation = 100% * (calculated-found) / calculated
Content of water and acitive substance
The water content values of 3.73 ± 1.55% determined using Karl-Fischer titration show that complete drying is impossible because of the hygroscopic nature of lobaplatin. Moreover the values display a very considerable mean variation.
The active substance content determined using HPLC (deducting the water content values obtained by Karl-Fischer titration) was 98.00 ± 1.38% active substance content and is less than the values prescribed in the specification and has also a wide mean variation. According to the specification, the content of the active substance must be between 97% and 102%.
The water contents of the trihydrate batches were 12.09 ± 0.09%, very close to the theoretical value of 11.96%. The analyses of the active substance assay also attained acceptable values with 99.76 ± 0.83%, their mean variation is within the limits conventional in pharmacy.
The content of known and unknown impurities was determined using thin layer chromatography. The sum of the impurities was determined for anhydrous substance as 1.21 ± 0.55% and as 0.34 ± 0.19% for trihydrate. Here, too, both absolute values and mean variation improved.
Improvements were also recorded for the measured turbidity values: whereas these were 1.45 ± 0.91 FTU for anhydrous substance, values of 0.38 ± 0.41 FTU were achieved with trihydrate.
Two batches each of anhydrous substance and trihydrate were stored in each case at 4°C, room temperature, 31 °C, 41 °C and 31 °C / 80% relative humidity (open sample vials). After 3, 6 and 12 months the impurities profile (TLC), active substance content (HPLC), water content (Karl-Fischer titration) and turbidity were investigated. The following findings were obtained for all storage conditions:
- The level of impurities rises with the anhydrous substance. In the case of
the trihydrate the impurities are at a constant, low level.
- The active substance content of the trihydrate is clearly closer to the 100%
value and displays less mean variation.
- The hygroscopic, anhydrous substance displays a rise in the water content
whereas this is constant in the case of the trihydrate.
- The turbidity of the lyophilisate batches, which were prepared from the
anhydrous substance, begin at markedly higher values and moreover rise
considerably in the course of storage. In the case of the trihydrate batches,
the turbidity values remain at a constant low level.
The lyophilisates were prepared according to the instructions set out in DE-OS 38 43 571.
7. Pharmaceutical processability
Because of the hydroscopic nature of the anhydrous compound, this must be handled with exclusion of air. Any moisture present causes sticking together and adhesion. The trihydrate, which is stable on air, is characterised by good flow characteristics and shows markedly improved dosability and processability.
Example for the preparation of lobaplatin trihydrate
3.8 g (10 mmol) cis-[trans-1,2-cyclobutane bis(methylamine)-N,N']-dichtoroplatinum(ll) are suspended in 20 ml water and heated to 40°C. 3.39 g (20 mmol) silver nitrate are added. After stirring for 1.5 hours and after cooling in a refrigerator the precipitated silver chloride is filtered off by suction and is washed with 10 ml water. The filtrate is passed over a column with 100 ml of a basic ion exchanger and post-washed with 150 ml water. Any conventional basic ion exchanger may be used as ion exchanger. The solution is added dropwise to 4.5 g (10 mml, 20%) L-lactic acid. After stirring for three days the mixture is concentrated to about 20 ml and left over night in a refrigerator. The precipitated crystals are suction filtered, the filtrate is concentrated further and the crystals precipitating after standing over night in a refrigerator are suction filtered again. The combined crystal amounts are recrystaliised from 20 ml water/ acetone (1/1, v/v). Yield 2.3 g (51%), melting point 210°C (decomposition).
C9H24N2O6Pt M = 451.38
Calculated: C 23. 95% H5 .36 o/
/o N 6 .21 % Pt 43. 22 %
Found: C 23. 94% H5 .28 % N 6 .15 % Pt 43. 05 %
C 23. 99% H5 .25 % N 6 .05 %
Water content (Karl-Fischer titration): 12.24% (calc. 11.96%)
1H-NMR (500 MHz, D2O) : ? (ppm) = 1,2 (d, 3H, CH3), 1,6 (m,2H,CH2-CH2), 1.9 (m, 2H, CH2-CH2), 2.4 (m, 2H, CH2-NH2), 2,65 (m, 2H, CH-CH), 2.85 (m, 2H, CH2-NH2), 4,05 (q, 1H, CH-CH3),4,3...5,0 (br, overlapped, NH2)
1. A process for the preparation of lobaplatin trihydrate, characterised in that cis-
[trans-1,2-cyclobutane bis(methylamine)-N,N']-dlhalogenoplatlnum(Il) is
converted by exchange reactions of the halogen ligands and subsequent working up in aqueous medium into cls-[trans-1,2-cyclobutane bis (methylamlne)-N,N']-[2S)-lactato-01,02]-piatinum(II)trihydrate.
Lobaplatin trihydrate constitutes a new and advantageous form of a platinum complex having an antitumour effect.
|Indian Patent Application Number||415/CAL/1995|
|PG Journal Number||11/2007|
|Date of Filing||17-Apr-1995|
|Name of Patentee||ZENTARIS GMBH|
|Applicant Address||WEISMULLERSTRASSE 45, 60314 FRANKFURT/MAIN|
|PCT International Classification Number||A 61 K 31/28|
|PCT International Application Number||N/A|
|PCT International Filing date|