NOVEL PLATINUM (IV) COMPLEXES, PROCESS FOR PRODUCING THE SAME, AND CARCINOSTATIC AGENTS CONTAINING THE SAME

Abstract: A platinum(IV) complex represented by the general formula (I): wherein R 1 and R 2 independently represent ammonia, an alkylamine or a cycloalkylamine, or R 1 and R 2 may together form a cycloalkyldiamine; X 1 and X 2 independently represent a halogen, nitrate ion, sulfate ion or a monocarboxylic acid, or X 1 and X 2 may together form a glycolate or a dicarboxylic acid; Y 1 represents formic acid, a C 1 -C 8 alkyl-, alkenyl-, aryl-, aralkyl-, alkylamino- or alkoxyl-monocarboxylic acid or sulfonic acid; and Y 2 represents a halogen. The complex of the invention is stable even when orally administered and has high antitumor activity.

Description: This invention relates to a novel platinum(IV) complex which shows strong antitumor activity, a process for the production thereof and a carcinostatic agent that contains the same. EP-A-0 328 274 discloses Pt(IV) complexes said to demonstrate patent antitumor acitivity. Since the development and practical use of cisplatin as an effective antitumor agent, a broad range of studies have been conducted with the aim of finding a new platinum complex which possesses more effective antitumor activity than cisplatin, and of improving properties thereof other than the antitumor action, such as reduction of toxicity and other undesirable side effects. Carboplatin is known as a platinum(II) complex, as well as recently developed oxaliplatin. With regard to platinum(IV) complexes, iproplatin is known, and tetraplatin has been subjected to clinical trial but its clinical development has been suspended due to side effects, such as toxicity. Each of these platinum complexes is for parenteral administration use and is hydrophilic. In order to improve quality of life of cancer patients, great concern has been directed toward the development of an oral preparation for use in the treatment of cancer patients at the terminal stage. The present invention provides platinum(IV) complexes having high antitumor activity, particularly for use in oral administration. Many of these complexes show high solubility in both water and organic solvents, have high partition coefficient and are stable in strongly acidic solution. The present invention provides a platinum(IV) complex represented by the general formula (I): wherein Y 1 represents a C 2 -C 8 alkyl-monocarboxylic acid and Y 2 represents Cl, Br or I. The invention is further illustrated by the accompanying drawings, in which: Fig. 1 shows a reaction scheme regarding the process for the production of the platinum(IV) complex of the present intention; and Fig. 2 is a chart showing an infrared absorption spectrum of C6-OHP·Cl as a member of the platinum(IV) complex of the present invention. A characteristic nature of the present invention is that a monocarboxylic acid and a halogen element are coordinated simultaneously at the trans position. The following shows abbreviations to be used herein. cis, trans, cis: c-t-c dach: 1,2-cyclohexanediamine (cis-dach, R,S-dach; trans-d-dach, 1S,2S-dach; trans-ℓ-dach, 1R,2R-dach) C5-OHP: t,c,c-[Pt(OCOC 4 H 9 ) 2 (ox)(1R,2R-dach)] ℓ-OHP: [Pt(ox)(1R,2R-dach)] C5-OHP·Cl: t,t,c,c-[PtCl(OCOC 4 H 9 )(ox)(1R,2R-dach)] C5-OHP·Br: t,t,c,c-[PtBr(OCOC 4 H 9 )(ox)(1R,2R-dach)] C5-OHP·I: t,t,c,c-[PtI(OCOC 4 H 9 )(ox)(1R,2R-dach)] C4-OHP: t,c,c-[Pt(OCOC 3 H 7 ) 2 (ox)(1R,2R-dach)] C4-OHP·Hal: t,t,c,c-[PtHal(OCOC 3 H 7 )(ox)(1R,2R-dach)] C6-OHP: t,c,c-[Pt(OCOC 5 H 11 ) 2 (ox)(1R,2R-dach)] C6-OHP·Hal: t,t,c,c-[PtHal(OCOC 5 H 11 )(ox)(1R,2R-dach) ℓ-OHP·Cl: t-[PtCl 2 (ox)(1R,2R-dach)] ℓ-OHP·Br: t-[PtBr 2 (ox)(1R,2R-dach)] ℓ-OHP·I: t-[PtI 2 (ox)(1R,2R-dach)] C4-COOAg: Ag-butylate C5-COOAg: Ag-valerate C6-COOAg: Ag-hexanoate C7-COOAg: Ag-heptanoate Hal: Cl, Br or I ox: oxalate HPLC: high performance liquid chromatography It was found that, when C4-OHP, C5-OHP, C6-OHP or the like Cn-OHP is orally administered, one carboxylic acid thereof is gradually substituted by Cl in the strongly acidic gastric juice (1 N HCl, pH 0.1). The platinum complex of the present invention can be synthesized by the following alternative methods: i.) A compound represented by the general formula II , wherein Y 2 is Cl, Br or I can react with a silver salt of a C 2 -C 8 alkyl monocarboxylic acid, or ii.) a compound represented by the general formula III , wherein Y 1 is as defined above can react with a hydrogen chloride, bromide or iodide. When C5-OHP is allowed to undergo 24 hours of reaction in a strong acid and then subjected to separation by HPLC, [PtCl(OCOC 4 H 9 ) (ox)(1R,2R-dach)], namely C5-OHP·Cl, can be produced. In the same manner, [PtCl(OCOC 3 H 7 )(ox)(1R,2R-dach)], namely C4-OHP·Cl, [PtCl(OCOC 5 H 11 )(ox)(1R,2R-dach)], namely C6-OHP·Cl, and [PtCl(OCOC 6 H 13 )(ox)(1R,2R-dach)], namely C7-OHP·Cl, can be produced from C4-OHP, C6-OHP and C7-OHP, respectively. The platinum complex of the present invention can be synthesized by the following alternative method. A methanol solution of ℓ-OHP·Cl (or Br or I) as [PtCl 2 (or Br 2 or I 2 ) (ox) (1R,2R-dach)] is allowed to undergo preferably 24 hours of reaction, preferably while stirring in the dark at room temperature, with 1 M of C5-COOAg (this can be obtained as white precipitate by adding silver nitrate to n-valeric acid and then adding alcohol thereto; C4-COOAg, C6-COOAg, C7-COOAg and the like can also be synthesized in the same manner and used instead thereof). After filtering off the thus formed AgCl, methanol is evaporated, the residue is dissolved in ethanol, activated carbon is added to the solution and filtered off and then water is added to the filtrate to collect the thus formed precipitate by filtration. In the same manner, C4-OHP·Cl, C6-OHP·Cl and C7-OHP·Cl can be produced. By using ℓ-OHP·Cl, ℓ-OHP·Br or ℓ-OHP·I as the starting material and allowing it to react with C4-COOAg, C5-COOAg, C6-COOAg or C7-COOAg, a large amount of C4-OHP·Cl(or Br or I), C5-OHP·Cl(or Br or I), C6-OHP·Cl(or Br or I) or C7-OHP·Cl(or Br or I) can be produced. According to this process, various types of complexes can be produced from C 1-8 COOAg. The aforementioned two synthetic processes are shown in Fig. 1. The platinum(IV) complexes of the present invention show antitumor activity when orally administered for the treatment of malignant tumors. In consequence, these complexes can be made into dosage forms suitable for oral administration, such as tablets, pills, capsules, liposome inclusions and sterile suspensions, as well as suppositories, liniments, ointments or solutions. Usual pharmaceutical carriers, additives, binders and/or fillers can also be used. They can be used also for parenteral administration as freeze-dried preparations and solutions. As fillers, diluents and auxiliaries of oral administration preparations, one or more materials can be used, for example lactose, sucrose, glucose, sorbitol, mannitol, potato starch, amylopectin, other various starches, cellulose derivatives (for example, carboxymethyl cellulose or hydroxyethyl cellulose), gelatin, magnesium stearate, polyvinyl alcohol, calcium stearate, polyethylene glycol, gum arabic, talc, titanium dioxide, vegetable oils such as olive oil, peanut oil, sesame oil, paraffin oils, neutral fat bases, ethanol, propylene glycol, physiological saline, sterile water, or glycerol. As fillers for injection use, sugar solutions, buffer solutions, ethylene glycol, polyethylene glycol and the like can be used. It is desirable to use the complex of the present invention in an amount of from 0.01 to 200 mg/kg, preferably from 0.1 to 100 mg/kg, more preferably from 0.5 to 50 mg/kg, in the case of parenteral administration, or from 0.1 to 2,000 mg/kg, preferably from 1 to 1,000 mg/kg, more preferably from 5 to 500 mg/kg, in the case of oral administration. The platinum complex of the present invention does not show medicinal problems such as renal toxicity, cross-resistance and mutagenicity. Examples of the present invention are given below by way of illustration. Example 1. Formation of C4-OHP·Cl A 0.2 g portion of C4-OHP was dissolved in 20 ml of 1 N HCl and allowed to stand for 12 hours at 37°C in the dark. After the reaction, the product was separated and purified by HPLC. Yield, 18 mg as colorless powder. HPLC: Using Cosmosil 5C18 (trade mark) columns of 10 mm i.d. x 5 cm (guard column) and 15 mm i.d. x 25 cm (main column), 0.8 ml of the sample solution was injected and eluted at 50°C with 30% MeOH at a rate of 3 ml/min. Example 2. Formation of C5-OHP·Cl A 0.4 g portion of C5-OHP was dissolved in 20 ml of 30% MeOH-1 N HCl mixture solution and allowed to stand for 30 hours at 37°C in the dark. After the reaction, the product was separated and purified by HPLC. Yield, 35 mg as colorless powder. HPLC was carried out under the same conditions as described in Example 1. Example 3. Formation of C6-OHP·Cl A 0.4 g portion of. C6-OHP was dissolved in 17 ml of 50% MeOH-1 N HCl mixture solution and allowed to stand for 36 hours at 37°C in the'dark. After the reaction, the product was separated and purified by HPLC. Yield, 35 mg as colorless powder. HPLC was carried out under the same conditions as described in Example 1. Infrared absorption spectrum of the thus obtained C 6 -OHP·Cl is shown in Fig. 2, and results of the TLC analysis (development solvent: butanol/acetic acid/water = 12:3:5) are shown below. Complex R f value ℓ-OHP 0.13 ℓ-OHP·Cl (starting material) 0.24 C6-OHP·Cl 0.29 C6-OHP 0.31 Example 4. Synthesis of C5-OHP·Br A 1.12 g portion of [PtBr 2 (ox)(1R,2R-dach)], namely ℓ-OHP·Br, was dissolved in 140 ml of hot MeOH, and the solution was mixed with 0.42 g of 1 M C5-COOAg and stirred for 48 hours at room temperature in the dark. After the reaction, the thus formed precipitate of AgBr was filtered off, MeOH was evaporated to dryness, the resulting residue was dissolved in 30 ml of EtOH, activated carbon was added to the solution and filtered off and then the filtrate was concentrated and subjected to alumina or silica gel column chromatography to effect separation (from the starting material and C5-OHP) and purification. Yield, 0.85 g, 73%, as light yellow powder. Example 5. Synthesis of C6-OHP·Br A 1.12 g portion of ℓ-OHP·Br was dissolved in 140 ml of MeOH, and the solution was mixed with 0.44 g of 1 M C6-COOAg and stirred for 48 hours at room temperature in the dark. After the reaction, the thus formed AgBr was filtered off to carry out purification by the same treatment as described in Example 4. Yield, 0.95 g, 80%, as light yellow powder. Example 6. Synthesis of C5-OHP·I A 0.65 g portion of ℓ-OHP·I was dissolved in 100 ml of MeOH, and the solution was mixed with 0.21 g of 1 M C5-COOAg and stirred for 48 hours at room temperature in the dark. Thereafter, the same treatment as in Example 4 was repeated. Yield, 0.45 g, 72%. Example 7. Synthesis of C6-OHP·I A 0.65 g portion of ℓ-OHP·I was dissolved in 100 ml of MeOH, and the solution was mixed with 0.22 g of 1 M C6-COOAg and stirred for 48 hours at room temperature in the dark. Thereafter, the same treatment as in Example 4 was repeated. Yield, 0.45 g, 71%. Example 8. Synthesis of C5-OHP·Cl A 0.47 g portion of ℓ-OHP·Cl was dissolved in 40 ml of H 2 O + MeOH mixture solution, and the solution was mixed with 0.21 g of 1 M C5-COOAg and stirred for 48 hours at room temperature in the dark. Thereafter, the same treatment as in Example 4 was repeated. Yield, 0.45 g, 85%. Example 9. Synthesis of C6-OHP·Cl A 0.47 g portion of ℓ-OHP·Cl was dissolved in 40 ml of H 2 O + MeOH mixture solution, and the solution was mixed with 0.19 g of 1 M C6-COOAg and stirred for 48 hours at room temperature in the dark. Thereafter, the same treatment as in Example 4 was repeated. Yield, 0.45 g, 85%. Example 10. Synthesis of C4-OHP·Cl Reaction of ℓ-OHP·Cl and C4-COOAg was carried out in the same manner as described in Examples 8 and 9. Yield, 0.45 g, 85%. Analytical data of the thus obtained complexes are shown below. 1. Elemental analysis C4-OHP·Cl, C 12 H 27 N 2 O 6 PtCl calcd. C 27.74; H 4.04; N 5.39 found 27.84; 4.75; 5.57 C5-OHP·Cl, C 13 H 29 N 2 O 6 PtCl calcd. C 29.26; H 4.31; N 5.25 found 29.16; 4.95; 5.10 C6-OHP·Cl, C 14 H 31 N 2 O 6 PtCl calcd. C 30.68; H 4.56; N 5.11; Pt 35.61 found 29.69; 4.78; 5.03; 35.00 C5-OHP·Br, C 13 H 29 N 2 O 6 PtBr calcd. C 26.98; H 3.97; N 4.87 found 26.94; 4.02; 4.87 C6-OHP·Br, C 14 H 31 N 2 O 6 PtBr calcd. C 28.37; H 4.22; N 4.72 found 27.36; 4.03; 4.59 C5-OHP·I, C 13 H 29 N 2 O 6 PtI calcd. C 24.96; H 3.68; N 4.48 found 24.85; 3.57; 4.40 C6-OHP·I, C 14 H 31 N 2 O 6 PtI calcd. C 26.29; H 3.19; N 4.38 found 26.30; 3.20; 4.40 2. Partition coefficient Partition coefficient (PC) of each of the thus obtained complexes to 1-octanol/water is as follows. Complex PC C4-OHP·Cl 3.6 x 10 -2 C5-OHP·Cl 2.4 x 10 -1 C6-OHP·Cl 8.4 x 10 -1 C7-OHP·Cl 2.7 3. Solubility Solubility of each of the thus obtained complexes in water (about 20°C) is shown below. Complex Solubility (mM) C4-OHP·Cl 147 C5-OHP·Cl 41 C6-OHP·Cl 9.6 C7-OHP·Cl 2.2 4. Stability Stability of each of the thus obtained complexes in an aqueous solution of hydrochloric acid at 37°C is shown below in terms of its half life. Half life (hour) Complex 0.05 M HCl 1 M HCl C4-OHP·Cl >50 6.1 C5-OHP·Cl >50 7.4 C6-OHP·Cl N.D. 8.9 C7-OHP·Cl N.D. 11.3 The term N.D. indicates that significant decrease in concentration was not observed. The measurements were carried out at a complex concentration of 50 µM at 37°C in the dark. 5. Reduction property Test results of the in vitro reduction of the thus obtained complexes by an ascorbic acid salt are shown below in terms of half life. Half life (hour) Complex 5 mM 100 mM C4-OHP·Cl 0.6 <0.1 C5-OHP·Cl 0.8 <0.1 C6-OHP·Cl 1.2 <0.1 C7-OHP·Cl 1.6 <0.1 The measurements were carried out at a complex concentration of 50 µM, pH 7.5 (50 mM HEPES·NaOH buffer), at 37°C in the dark. Carcinostatic Test ip: On the day 0, L 1210 (10 5 cells/mouse) was transplanted into the abdominal cavity of each CDF 1 mouse, and each of the platinum complexes was intraperitoneally administered on the day 1, day 5 and day 9 (Q04D x 03). Using 5 animals in one group, T/C% (T: treated, C: control) is calculated from survived days. A T/C% value of 125 or more was judged effective. The number of survived (or tumor bearing) animals is shown as n/5. 10 mice in total were used in the control. The results are shown below. Carcinostatic effect ip-ip, L 1210, three administrations on days 1, 5 and 9 100 50 25 12.5 mg/kg dose C4-OHP·Cl T 63 195 145 130 T/C% C5-OHP·Cl T 88 283 (4/5) 168 C6-OHP·Cl T 80 280 (1/5) 173 C7-OHP·Cl 176 137 122 C5-OHP·Br 107 395 (4/5) C6-OHP·Br T 69 T 96 373 (4/5) T = toxic L 1210 (10 5 cells/mouse), one group "=" 5 CDF 1 mice, ip administration on the days 1, 5 and 9. po: On the day 0, L 1210 (10 5 cells/mouse) was transplanted into the abdominal cavity of each CDF 1 mouse, and each of the platinum complexes was orally administered on the day 1, day 3, day 5, day 7 and day 9 (Q02D x 05), or on the day 1 to day 5 (Q01D x 05). The oral administration was carried out with a 10, 7.5 or 5 times higher dose than the optimum amount of each platinum complex by ip (T/C% of ip; 100 mg/kg, 75 mg/kg or 50 mg/kg, respectively). A value of 140% or more was judged effective. The results are shown below. (Oral) carcinostatic effect L 1210, ip-po, every two days Q02D x 05 mg/kg dose 15 10 5 2.5 C5-OHP·Cl T 60 143 214 140 C6-OHP·Cl T 98 168 191 143 C7-OHP·Cl 151 129 117 C5-OHP·Br T 73 163 160 C6-OHP·Br T 88 180 173 T = toxic L 1210 (10 5 cells/mouse); one group = 5 CDF 1 mice; Suspension in olive oil was administered into the stomach through a catheter.

Claims: A platinum(IV) complex represented by the general formula (I): wherein Y 1 represents a C 2 -C 8 alkyl monocarboxylic acid and Y 2 represents Cl, Br or I. A carcinostatic preparation which comprises an effective amount of the platinum(IV) complex of claim 1 as an active ingredient. A complex according to claim 1 for use as a carcinostatic. The use of a complex according to claim 1 for the manufacture of a carcinostatic preparation. A process for producing the platinuin(IV) complex of claim 1 which comprises allowing a compound represented by the general formula (II): , wherein Y 2 is as defined in claim 1, to react with a silver salt of a C 2 -C 8 alkyl monocarboxylic acid. A process for producing the platinum(IV) complex of claim 1 which comprises allowing a compound represented by the general formula (III) : , wherein Y 1 is as defined in claim 1, to react with a hydrogen chloride, bromide or iodide.

Inventors: KIDANI YOSHINORI, KIDANI, YOSHINORI
Applicants: KIDANI YOSHINORI, KIDANI, YOSHINORI
Application year: 1996
Main classification: C07F15
IPC codes: C07F15