Diamine platinum(IV) complexes having mixed carboxylate ligands as antitumor agents

Abstract

Platinum(IV) complexes with mixed carboxylato ligands having the formula: ##STR1## where X.sup.1 and X.sup.2 are carboxylato, or are jointly dicarboxylato, where .sup.1 Y and Y.sup.2 are carboxylato, and where Z is either diaminocyclohexane or ethylenediamine, have been found to have desirable antitumor activity, as well as relatively low levels of toxicity.

Description

FIELD OF THE INVENTION

The present invention relates to platinum based drugs and methods of using such drugs and formulations thereof in antitumor therapy.

BACKGROUND OF THE INVENTION

Some platinum based drugs are known to have useful antitumor activity. However, such drugs are also known to have various problems. For example, cis-diamminedicloroplatinum(II), also referred to as cisplatin or CDDP, is one such drug with a significant level of activity, but which also exhibits significant nephrotoxicity and other harmful side effects. Other platinum drugs have been synthesized which have less potential to cause renal injury, but many of these drugs are much less soluble in water than is desirable.

A long standing need exists for platinum drugs which have improved aqueous solubility and antitumor activity, a broad spectrum of activity against various neoplastic disease states, reduced toxicity, and a lack of cross resistance to other antitumor drugs such as cisplatin.

SUMMARY OF THE INVENTION

The present invention relates to platinum(IV) complexes having the formula ##STR2## and stereoisomers thereof, where X.sup.1 and X.sup.2 are carboxylato ligands, or are jointly a dicarboxylato ligand, Y.sup.1 and Y.sup.2 are carboxylato ligands, and Z is a bidentate amino ligand selected from the group consisting of diaminocyclohexane and ethylenediamine. X.sup.1 and X.sup.2 can be different carboxylato ligands than Y.sup.1 and Y.sup.2 . When X.sup.1 and X.sup.2 are monocarboxylato, they preferably have between about 1-10 carbon atoms each. When X.sup.1 and X.sup.2 are jointly dicarboxylato, they preferably have between about 2-20 carbon atoms. Likewise, when Y.sup.1 and Y.sup.2 are monocarboxylato, they preferably have between about 1-10 carbon atoms each.

Examples of suitable carboxylato ligands include acetato, trifluoroacetato, cyclobutanecarboxylato, 1,1-cyclobutanedicarboxylato, oxalato, malonato, methylmalonato, ketomalonato, and tartronato.

The present invention also concerns antitumor compositions which include an effective amount of one or more above-described complexes, and a pharmaceutically acceptable carrier. Additionally, the present invention concerns methods of inhibiting neoplastic cell growth, which include the step of administering to a mammal an effective amount of one or more of the above-described complexes.

The complexes, compositions, and methods of the present invention possess significant advantages over the prior art. Platinum (IV) complexes in accordance with the present invention possess high aqueous solubility, high antitumor activity (greater against some tumor models than cisplatin and carboplatin), a broad spectrum of activity, and a lack of cross resistance to other antitumor drugs such as cisplatin. Therefore, the complexes, compositions, and methods of the present invention are believed to have significant therapeutic advantages in the treatment of neoplastic disease states, including the specific cancers of the testes, ovaries, bladder, and head and neck.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Synthesis

A number of diaminocyclohexane (DACH) complexes, listed in Table 1 below, were synthesized, having the general formula: ##STR3##

TABLE 1__________________________________________________________________________Elemental Analysis of DACH--Pt(IV) ComplexesComplexNo. Complex Name Observed (Calculated)__________________________________________________________________________ 1. (Trans-R,R-1,2-diaminocyclohexane)- 30.79(30.82) 4.86(4.77) 4.92(5.13) (tetraacetato)platinum(IV) 2. (Trans-S,S-1,2-diaminocyclohexane)- 30.45(30.82) 4.84(4.77) 4.81(5.13) (tetraacetato)platinum(IV) 3. (Cis-1,2-diaminocyclohexane)- 30.11(30.82) 4.93(4.73) 4.75(5.13) (tetraacetato)platinum(IV) 4. Cis-diacetato(trans-R,R-1,2- 24.66(25.03) 2.57(3.27) 4.09(4.17) diaminocyclohexane)trans-bis(tri- fluoroacetato)platinum(IV).H.sub.2 O 5. Trans-diacetato(trans-R,R-1,2- 25.42(25.72) 4.23(3.06) 4.82(4.28) diaminocyclohexane)cis-bis(tri- fluoroacetato)platinum(IV) 6. Trans-diacetato(trans-R,R-1,2- 37.13(37.32) 5.29(5.59) 4.24(4.35) diaminocyclohexane)cis-bis(cyclo- butanecarboxylato)platinum(IV).H.sub.2 O 7. Trans-diacetato(trans-S,S-1,2- 39.01(38.40) 5.46(5.44) 4.06(4.48) diaminocyclohexane)cis-bis(cyclo- butanecarboxylato)platinum(IV) 8. Trans-diacetato(cis-1,2-diamino- 37.34(37.32) 5.51(5.59) 4.18(4.35) cyclohexane)-bis(cyclo- butanecarboxylato) platinum(IV).H.sub.2 O 9. Cis-bis(cyclobutanecarboxylato)- 31.19(31.95) 3.58(3.99) 3.76(3.72) (trans-R,R-1,2-diaminocyclohexane)- trans-bis(trifluoroacetato) platinum(IV).H.sub.2 O10. Trans-diacetato(trans-R-R-1,2-dia- 27.71(27.96) 4.17(3.88) 5.23(5.43) minocyclohexane)oxalatoplatinum(IV)11. Trans-diacetato(trans-S,S-1,2- 27.06(27.01) 4.15(4.12) 5.13(5.25) diaminocyclohexane)oxalatoplatinum (IV).H.sub.2 O12. Trans-diacetato(cis-1,2-diamino- 26.00(26.13) 4.06(4.35) 5.34(5.08) cyclohexane)oxalatoplatinum(IV).2H.sub.2 O13. (Trans-R,R-1,2-diaminocyclohexane)- 22.76(22.46) 2.33(2.49) 4.52(4.36) oxalato-trans-bis(trifluoro- acetato)platinum(IV).H.sub.2 O14. Trans-diacetato(trans-R,R-1,2- 29.25(30.35) 4.44(4.32) 4.99(5.15) diaminocyclohexane)malonatoplatinum (IV)15. Trans-diacetato(trans-S,S-1,2- 29.26(30.35) 4.38(4.32) 4.89(5.15) diaminocyclohexane)malonatoplatinum (IV)16. Trans-diacetato(cis-1,2-diamino- 30.34(29.48) 4.56(4.15) 4.74(5.29) cyclohexane)malonatoplatinum(IV)17. (Trans-R,R-1,2-diaminocyclohexane)- 22.70(23.17) 2.32(2.97) 4.37(4.16) malonato-trans-bis(trifluoro- acetato)platinum(IV).2H.sub.2 O18. Trans-diacetato(trans-R,R-1,2- 26.46(26.85) 4.06(4.47) 5.18(4.82) diaminocyclohexane)tartronato- platinum(IV)19. Trans-diacetato(trans-R,R-1,2-dia- 25.41(25.66) 4.17(3.92) 5.30(4.99) minocyclohexane)(ketomalonato) platinum(IV)20. Trans-diacetato(trans-R,R-1,2-di- 30.64(30.93) 4.61(4.41) 5.09(5.15) aminocyclohexane)(methylmalonato)- platinum(IV)21. (1,1-cyclobutanedicarboxylato)- 33.48(33.74) 4.61(4.57) 4.74(4.92) trans-diacetato(trans-R,R,-1,2- diaminocyclohexane)platinum(IV)22. (1,1-cyclobutanedicarboxylato)- 33.84(33.74) 4.48(4.57) 4.57(4.92) trans-diacetato(trans-S,S-1,2- diaminocyclohexane)platinum(IV)23. (1,1-cyclobutanedicarboxylato)- 33.86(33.74) 4.48(4.57) 4.72(4.92) trans-diacetato(trans-R,R-1,2- diaminocyclohexane)platinum(IV)24. (1,1-cyclobutanedicarboxylato)- 28.54(28.36) 2.98(2.95) 4.04(4.13) trans-R,R,-1,2-diaminocyclohexane trans-bis(trifluoroacetato)- platinum(IV)__________________________________________________________________________

Trans-diacetato-(trans-R,R-1,2-diaminocyclohexane) malonato-platinum(IV) (complex no. 14 in Table 1) was synthesized by using the following multistep procedure. Potassium tetrachloroplatinum(II) (20.76 g, 50 mmol) was dissolved in deionized water (500 ml) and filtered. To the filtrate was then added potassium iodide (83 g, 0.5 mol in 50 ml of water) and allowed to stir for 5 min. To this solution trans-R,R-1,2-diaminocyclohexane (trans-R,R-DACH) (5.7 g, 0.5 mol in 10 ml of water) was added. A yellow precipitate formed immediately and the reaction mixture was left stirring for 30 min. at room temperature. The water insoluble trans-R,R-DACH-diiodoplatinum(II) was collected by filtration and washed successively with water, dimethylformamide, ethanol, and ether. The final product was dried in a vacuum (yield 95%).

The trans-R,R-DACH-diiodoplatinum(II) (4.5 g, 8 mmol) was mixed with a slightly less than equimolar amount of silver sulfate (2.44 g, 7.8 mmol) in water and the reaction mixture was stirred for 24 hrs in the dark at room temperature. The water soluble aqua-trans-R,R-DACH-sulfatoplatinum(II) was removed from silver chloride precipitate by filtration and was evaporated to dryness at 40.degree. C. under reduced pressure using a rotary evaporator. The final product was recrystallized from water. Aqua-trans-R,R-DACH-sulfato-platinum(II) complex (1.692 g, 4 mmol) was dissolved in 50 ml of water, and a solution of sodium malonate (prepared in situ by mixing 1.6 ml of 5 N NaOH and 0.416 g of malonic acid in 20 ml of water) was added. The reaction mixture was left stirring at room temperature for 24 hrs. The off-white precipitate was separated by filtration. The crude product was recrystallized from water to give white crystals of trans-R,R-DACH-malonatoplatinum(II) (yield=85%).

Trans-R,R-DACH-malonatoplatinum(II) (1.233 g, 3 mmol) was suspended in water (100 ml), to which was then added in small portions 30% aqueous hydrogen peroxide (10 ml) at 70.degree. C. on a water bath under stirring for one hr, followed by stirring overnight at room temperature. The final clear solution was filtered and the filtrate was evaporated to dryness under reduced pressure at room temperature. The light yellow solid was redissolved in 30 ml water, filtered and the volume of the filtrate was reduced to about 5 ml which was treated with 100 ml acetone. The white precipitate of trans-R,R-DACH-dihydroxomalonatoplatinum(IV) was recovered by filtration, washed with a small portion of ethanol and dried under vacuum (yield=90%). Finally, trans-R,R-DACH-dihydroxomalonato platinum(IV) (0.89 g, 2 mmol) was suspended in 100 ml CHCl.sub.3 and 10 ml of acetic anhydride was added. The mixture was left stirring for 5 hrs at room temperature. Methanol (100 ml) was added to the mixture to give a clear light yellow solution which was kept on stirring for an additional 1 hr, filtered and the filtrate was evaporated to dryness under reduced pressure at room temperature. The final product was redissolved in 30 ml of methanol, filtered and the filtrate was treated with 100 ml ether to give a white precipitate which was collected on a filter paper (yield=95%).

By using the above mentioned procedure the complexes 1-13 and 15-24 in Table 1 were also synthesized. Infrared NMR spectra for these complexes are given in Table 2 below.

TABLE 2______________________________________Spectroscopic Data of DACH--Pt(IV) ComplexesComplex IR.sup.a, Cm.sup.-1 .sup.195 Pt.sup.bNo .upsilon.(N--H) .upsilon..sub.as (C--O) .upsilon..sub.s (C--O) .delta., ppm______________________________________ 1 3160, 3080 1619 1357, 1287 2 3160, 3080 1600 1350, 1270 3 3160, 3080 1608 1355, 1270 4 3160, 3080 1655, 1614 1360, 1160 +1893 5 3161, 3076 1642, 1622 1362, 1186 6 3160, 3080 1606 1342, 1285 7 3160, 3080 1606 1342, 1285 +1846 (H.sub.2 O) 8 3160, 3080 1619 1360, 1272 +1840 (MeOH) 9 3170, 3080 1690, 1629 1342, 116510 3160, 3080 1659 1353, 127711 3160, 3080 1650 1343, 127112 3160, 3080 1680 1355, 127613 3160, 3075 1701, 1596 1344, 116214 3160, 3080 1612 1342, 1285 +1755 (H.sub.2 O)15 3160, 3090 1616 1346, 128416 3160, 3080 1619 1360, 127217 3170, 3070 1705, 1600 1345, 115018 3171, 3071 1709, 1647 1359, 127919 3171, 3078 1705, 1657 1360, 1288 +1576 (MeOH)20 3170, 3080 1619 1348, 1263 +1798 (MeOH)21 3160, 3080 1618 1350, 1280 +1750 (acetone)22 3160, 3090 1610 1350, 128023 3160, 3080 1620 1385, 1274 +1840 (MeOH)24 3170, 3080 1690, 1624 1332, 1447______________________________________ .sup.a Infrared spectra are recorded as KBr pellets, and band positions are givin in cm.sup.1 .sup.b 195 Pt chemical shifts are relative to Na.sub.2 PtCl.sub.6 peak in D.sub.2 O at 0.0 ppm

Certain ethylenediamine platinum(IV) complexes were synthesized as indicated below. In this section, the following abbreviations are used: CDDP, cis-diamminedichloroplatinum(II); en, ethylenediamine; Mal, malonic acid; CBDCA, 1,1-cyclobutanedicarboxylic acid; DMF, N,N-dimethylformammide; IR, infrared; NMR, nuclear magnetic resonance; IC.sub.50, concentration of drug required to inhibit cell growth by 50%.

Silver sulfate, CBDCA, Mal, cyclobutanecarboxylic acid (C.sub.4 H.sub.7 COOH), cyclopentanecarboxylic acid (C.sub.5 H.sub.9 COOH), cyclohexanecarboxylic acid (C.sub.6 H.sub.11 COOH), and trifluoroacetic anhydride ((CF.sub.3 CO)) were obtained from Aldrich Chemical Co. (Milwaukee, Wis.) while en and acetic anhydride ((CH.sub.3 CO).sub.2 O) were obtained from Fisher Scientific Co. (Houston, Tex.). K.sub.2 PtCl.sub.4 was purchased from Johnson Matthey (Seabrook, N.H.). All chemicals obtained from commercial suppliers were used as received.

Pt(en)I.sub.2. An aqueous solution of K.sub.2 PtCl.sub.4 (4.15 g, 10 mmol) was treated with KI (6.6 g, 100 mmol) and stirred for 10 min at room temperature. One equivalent of ethylenediamine was added dropwise to the resulting K.sub.2 PtI.sub.4 solution. Upon stirring for another 5 min, the Pt(en)I.sub.2 precipitate was filtered, washed extensively with water, and recrystallized from a DMF/H.sub.2 O mixture. After washing with water, methanol and diethyl ether, the final product was dried in vacuo. Yield, 95%.

Pt(en)(SO.sub.4)(H.sub.2 O). To a Pt(en)I.sub.2 (2.38 g, 4.7 mmol) suspension in 200 ml of H.sub.2 O in a flask wrapped with aluminum foil was added 500 ml of silver sulfate solution (1.40 g, 4.5 mmol) and 50 ml of acetone. The mixture was stirred overnight. After removal of silver iodide by filtration through Celite, the filtrate was evaporated to dryness at 35.degree. C. The residue was washed with acetone and dried in vacuo. Pt(en)(SO.sub.4)(H.sub.2 O) was obtained as a bright yellow solid, and the yield was quantitative. Anal. Calc. for C.sub.2 H.sub.10 N.sub.2 O.sub.5 SPt: C, 6.50; H, 2.73; N, 7.79. Found: C, 6.93; H, 2.25; N, 7.02.

Pt.sup.II (en)(X) (X=CBDCA or Mal) and Pt(en)X.sup.1 X.sup.2 (X.sup.1 and X.sup.2 =Cl, OCOC.sub.4 H.sub.7, OCOC.sub.5 H.sub.9, or OCOC.sub.6 H.sub.11). The general synthetic procedures for these complexes are the same; therefore, only the preparation of Pt.sup.II (en)(CBDCA) is described here as an example. Pt(en)(SO.sub.4)(H.sub.2 O)(1.11 g, 3 mmol) was dissolved in 50 ml of water, and 20 ml of sodium 1,1-cyclobutanedicarboxylte (prepared in situ by mixing 6 ml of 1 N NaOH and 0.43 g of CBDCA (3 mmol)) was added. After stirring overnight, the volume of the reaction mixture was reduced to 3 ml under reduced pressure. The precipitate was collected with filter and washed with acetone. The crude product was redissolved in 800 ml of water and filtered through Celite and the filtrate was evaporated to 2 ml under reduced pressure. The crystalline solid was collected with filter and washed with water, acetone, and diethyl ether. The final product, Pt.sup.II (en)(CBDCA), was dried in vacuo. Yield, 75%.

Pt.sup.IV (en)(X)(OH).sub.2 and Pt.sup.IV (en)X.sup.1 X.sup.2 (OH).sub.2. Addition of 10 ml of 30% H.sub.2 O.sub.2 to an aqueous solution of partially dissolved Pt.sup.II (en)(CBDCA) (0.80 g, 2 mmol) produced a clear solution initially, which was then followed by the appearance of a white precipitate. After stirring at room temperature overnight, the resulting precipitate was filtered, washed with water, acetone and diethyl ether, and dried in vacuo. Pt.sup.IV (en)(CBDCA)(OH.sub.2 was obtained as a white solid. Yield, 76%.

All the trans-dihydroxoplatinum(IV) complexes were prepared in a manner similar to that described above.

Pt.sup.IV (en)(X)A.sub.2 and Pt.sup.IV (en)X.sup.1 X.sup.2 Y.sup.1 Y.sup.2, where Y.sup.1 and Y.sup.2 =OCOCH.sub.3 or OCOCF.sub.3. To a Pt.sup.IV (en)(CBDCA)(OH).sub.2 suspension (0.30 g, 0.7 mmol) in 50 ml of CH.sub.2 Cl.sub.2 was added 5 ml of acetic anhydride. The mixture was stirred for 2 days. The solvent was removed by evaporation under reduced pressure and the residue was recrystallized from methanol. The final product, Pt.sup.IV (en)(CBDCA)(OCOCH.sub.3).sub.2, was dried in vacuo. Yield, 68%.

Pt.sup.IV (en)(CBDCA)(OCOCF.sub.3).sub.2 was prepared by using the above-mentioned procedure, starting with Pt.sup.IV (en)(CBDCA)(OH).sub.2 and (CF.sub.3 CO).sub.2 O.

The remaining complexes [trans-diacetatoplatinum(IV) and trans-bis(trifluoroacetato)platinum(IV)] listed in Table 5 were prepared in a manner similar to that described above.

Elemental analysis data is given in Table 3. Infrared and NMR spectra for these complexes are given in Table 4.

TABLE 3__________________________________________________________________________Elemental Analysis of Ethylenediamine Platinum(IV) ComplexesComplex Found (%) Calc. (%)No. Complex C H N C H N__________________________________________________________________________25 Pt.sup.IV (en)(CBDCA)(OCOCH.sub.3).sub.2 28.09 4.05 5.15 27.97 3.91 5.4326 Pt.sup.IV (en)(CBDCA)(OCOCF.sub.3).sub.2 22.91 2.16 4.31 23.12 2.26 4.4927 Pt.sup.IV (en)(Mal)(OCOCH.sub.3).sub.2 22.54 3.45 5.90 22.74 3.39 5.8928 Pt.sup.IV (en)(Mal)(OCOCF.sub.3).sub.2 18.36 1.73 4.75 18.53 1.73 4.8029 Pt.sup.IV (en)Cl.sub.2 (OCOCH.sub.3).sub.2 16.14 2.99 6.18 16.22 3.18 6.3130 Pt.sup.IV (en)Cl.sub.2 (OCOCF.sub.3).sub.2 12.90 1.73 4.95 13.05 1.46 5.0731 Pt.sup.IV (en)(OCOC.sub.4 H.sub.7).sub.2 (OCOCH.sub.3).sub.2 33.43 4.81 4.88 33.62 4.94 4.9032 Pt.sup.IV (en)(OCOC.sub.4 H.sub.7).sub.2 (OCOCF.sub.3).sub.2 27.99 2.98 4.00 28.28 3.26 4.1233 Pt.sup.IV (en)(OCOC.sub.5 H.sub.9).sub.2 (OCOCH.sub.3).sub.2 36.01 5.48 4.60 36.06 5.38 4.6734 Pt.sup.IV (en)(OCOC.sub.5 H.sub.9).sub.2 (OCOCF.sub.3).sub.2 30.27 3.52 3.91 30.56 3.70 3.9635 Pt.sup.IV (en)(OCOC.sub.6 H.sub.11).sub.2 (OCOCH.sub.3).sub.2 38.33 5.72 4.42 38.28 5.78 4.4636 Pt.sup.IV (en)(OCOC.sub.6 H.sub.11).sub.2 (OCOCF.sub.3).sub.2 32.43 3.87 3.75 32.66 4.11 3.81__________________________________________________________________________ TABLE 4__________________________________________________________________________Infrared and NMR Spectroscopic Data for EthylenediaminePlatinum(IV) Complexes.sup.1Complex IR, cm.sup.-1 NMR, ppmNo. .sup.v N--H .sup.v C.dbd.O .sup.v C--O .sup.v C--F .sup.13 C .sup.195 Pt__________________________________________________________________________25 3177-3042 1620 1348, 1276 181.7 172726 3189-3104 1706, 1630 1336, 1209 1153 180.9, 184.8 176827 3179-3084 1617 1344, 1272 177.2, 181.9 170628 3214-3166 1706, 1638 1360, 1205 1153 172.0.sup.2 1796.sup.329 3190 1620 1361, 1349 179.5.sup.2 1028.sup.3 127230 3171, 3082 1720, 1601 1376, 1208 1151 165.4.sup.4 923.sup.531 3204 1619 1349, 1273 182.5, 185.3 177032 3170-3155 1712, 1624 1340, 1253 1163 184.3.sup.6 1827.sup.533 3211-3177 1619 1351 182.5, 186.4 1806.sup.5 1303(sh) 127334 3189-3144 1699, 1623 1339-1319 1162 185.5, 187.1.sup.6 1782.sup.5 129835 3175 1616 1351-1338 181.8, 185.0.sup.6 1796.sup. 5 1308(sh) 126936 3179-3155 1711, 1624 1371-1351 1160 185.1.sup.6 1778.sup.5 1315, 1258__________________________________________________________________________ .sup.1 Infrared spectra were recorded as KBr pellets. sh = shoulder. .sup.195 Pt NMR spectra were recorded in H.sub.2 O or CH.sub.3 OH. All .sup.195 Pt chemical shifts were referenced to aqueous Na.sub.2 PtCl.sub.6. .sup.13 C NMR spectra were recorded in D.sub.2 O with CD.sub. OD as reference (49.00 ppm). .sup.2 Measured in (CD.sub.3).sub.2 SO. .sup.3 Measured in (CH.sub.3).sub.2 SO. .sup.4 Quartet. J.sub.C(.dbd.O)--F = 38.9 Hz. Measured in CD.sub.3 OD. .sup.5 Measured in CH.sub.3 OH. .sup.6 Measured in CD.sub.3 OD.

Antitumor Activity

EXAMPLE 1

Cisplatin-sensitive L1210/0 cells (1.times.10.sup.5 cells/mouse) were injected intraperitoneally in male BDF1 mice on day 0, and a DACH complex, in an aqueous medium, was administered intraperitoneally at dose levels ranging from 1.56 to 200 mg/kg on days 1, 5 and 9. the median life spans of control (C) and treated (T) animals were determined, and the percent T/C at the optimal dose calculated as an indicator of antitumor efficacy. (Percent T/C is the median survival time of treated mice/median survival time of control mice x 100.) From the efficacy data, the optimal dose was ascertained. Table 5 gives the percent T/C values for the complexes tested, as well as the number of mice cured where applicable.

TABLE 5______________________________________Efficacy of Complexes Against L1210/0 Optimal doseComplex No. (mg/kg/inj) % T/C at opt. dose______________________________________ 1 200 206 2 200 194 3 200 182 4 25 218 (1/5) 6 100 206 7 50 182 (2/5) 9 25 241 (1/5)10 50 17111 50 13512 100 15913 50 >700 (3/5)14 200 19415 200 17116 200 206 (1/5)17 100 21821 200 11222 200 11223 200 11224 200 253 (1/5)Cisplatin 5 300Carboplatin 75 147______________________________________ Figures in parentheses are number of animals cured/number of animals treated.

EXAMPLE 2

Cisplatin-resistant L1210/cisplatin cells (1.times.10.sup.5 cells/mouse) were injected intraperitoneally in male BDF1 mice on day 0, and a DACH complex, in an aqueous medium, was administered intraperitoneally at dose levels ranging from 1.56 to 200 mg/kg on days 1, 5 and 9. The median life spans of control (c) and treated (T) animals were determined, and the percent T/C calculated as an indicator of antitumor efficacy. From the efficacy data, the optimal dose was ascertained. Table 6 gives the optimal dose and percent T/C values for the complexes tested.

TABLE 6______________________________________Efficacy of complexes against L1210/cisplatin Optimal doseComplex No. (mg/kg/inj) % T/C at opt. dose______________________________________ 4 25 148 6 50 157 9 25 22413 50 17614 200 13824 100 205Cisplatin 5 100Carboplatin 75 111______________________________________

EXAMPLE 3

Ethylenediamine platinum complexes were dissolved in water or 95% ethanol and their antitumor activity determined in vitro against murine leukemia L1210/0 cells (final ethanol concentration 0.25%). Briefly, cells were cultured in RPMI 1640 medium containing 10% fetal calf serum, and cytotoxicity was determined after continuous drug exposure for 72 h by an MTT assay. Drug concentration was plotted against cell survival, and IC.sub.50 values (drug concentration giving 50% survival) were determined directly from the plot.

As shown in Table 7, all the compounds displayed antitumor activity, with IC.sub.50 values in the range of 0.1 to 93 .mu.M. Carboxylato groups in the axial position appear to have a substantial influence on antitumor activity for equatorial mondentate bis-carboxylato analogs but less influence for bidentate carboxylato analogs.

TABLE 7______________________________________Ethylenediamine Platinum (IV) Complexes andTheir Antitumor Activity Against L1210/0 Leukemia Cells ##STR4##ComplexNo. Y.sup.1 and Y.sup.2 X X.sup.1 and X.sup.2 IC.sub.50 (.mu.M)______________________________________25 OCOCH.sub.3 CBDCA 92.526 OCOCF.sub.3 CBDCA 33.627 OCOCH.sub.3 Mal 73.228 OCOCF.sub.3 Mal 39.329 OCOCH.sub.3 Cl 7.130 OCOCF.sub.3 Cl 3.831 OCOCH.sub.3 OCOC.sub.4 H.sub.7 85.632 OCOCF.sub.3 OCOC.sub.4 H.sub.7 0.1133 OCOCH.sub.3 OCOC.sub.5 H.sub.9 39.334 OCOCF.sub.3 OCOC.sub.5 H.sub.9 0.2735 OCOCH.sub.3 OCOC.sub.6 H.sub.11 8.336 OCOCF.sub.3 OCOC.sub.6 H.sub.11 0.14______________________________________

Compositions in accordance with the present invention can suitably include a pharmaceutically effective amount of one or more platinum complexes in accordance with the present invention, and a pharmaceutically acceptable carrier, such as, for example, water, saline, or dextrose solution. Compositions in accordance with the present invention will contain between about 0.001% and about 99% by weight active complexes, preferably between about 0.001% and about 10%.

Methods in accordance with the present invention comprise administering to a mammal an effective amount of the compounds or complexes described above. The administering step can suitably be parenteral and by intravenous, intraarterial, intramuscular, intralymphatic, intraperitoneal, subcutaneous, intrapleural, or intrathecal injection, or by topical application or oral dosage. Such administration is preferably repeated on a timed schedule until tumor regression or disappearance has been achieved, and may be used in conjunction with other forms of tumor therapy such as surgery or chemotherapy with different agents. The dose administered of a complex in accordance with the present invention can be between about 0.5 and about 100 mg/kg of body weight of the subject to which it is administered.

The description and examples given in this patent are intended to illustrate the present invention. They are not intended to be an exhaustive list of all possible specific embodiments of the present invention. Those skilled in the art will recognize that modifications could be made to the specific embodiments listed here which would still be within the scope of the present invention.

Claims

1. A platinum(IV) complex having the formula ##STR5## or a stereoisomer thereof, where X.sup.1 and X.sup.2 are carboxylato or are jointly dicarboxylato, where Y.sup.1 and Y.sup.2 are carboxylato, and where Z is a bidentate ligand selected from the group consisting of diaminocyclohexane and ethylenediamine.

2. The complex of claim 1, where X.sup.1 and X.sup.2 are carboxylato having between about 1-10 carbon atoms each or are jointly dicarboxylato having between about 2-20 carbon atoms, and where Y.sup.1 and Y.sup.2 are carboxylato having between about 1-10 carbon atoms each.

3. The complex of claim 1, where X.sup.1 and X.sup.2 are selected from the group consisting of

acetato,

trifluoroacetato, and

cyclobutanecarboxylato,

or are jointly selected from the group consisting of

oxalato,

malonato,

methylmalonato,

ketomalonato,

tartronato, and

1,1-cyclobutanedicarboxylato.

4. The complex of claim 1, where Y.sup.1 and Y.sup.2 are selected from the group consisting of

acetato,

trifluoroacetato, and

cyclobutanecarboxylato.

5. An antitumor composition which includes (a) an amount effective to inhibit neoplastic cell growth of a platinum(IV) complex having the formula ##STR6## or a stereoisomer thereof where X.sup.1 and X.sup.2 carboxylato or are jointly dicarboxylato, where Y.sup.1 and Y.sup.2 are carboxylato, and where Z is a bidentate ligand selected from the group consisting of diaminocyclohexane and ethylenediamine, and (b) a pharmaceutically acceptable carrier.

6. The composition of claim 5, where X.sup.1 and X.sup.2 are carboxylato having between about 1-10 carbon atoms each or are jointly dicarboxylato having between about 2-20 carbon atoms, and where Y.sup.1 and Y.sup.2 are carboxylato having between about 1-10 carbon atoms each.

7. The composition of claim 5 where X.sup.1 and X.sup.2 are selected from the group consisting of

acetato,

trifluoroacetato, and

cyclobutanecarboxylato,

or are jointly selected from the group consisting of

oxalato,

malonato,

methylmalonato,

ketomalonato,

tartronato, and

1. 1-cyclobutanedicarboxylato.

8. The composition of claim 5, where Y.sup.1 and Y.sup.2 are selected from the group consisting of

acetato,

trifluoroacetato, and

cyclobutanecarboxylato.

9. A method of inhibiting neoplastic cell growth, including the step of administering to a mammal an amount effective to inhibit neoplastic cell growth of a platinum(IV) complex having the formula ##STR7## or a stereoisomer thereof, where X.sup.1 and X.sup.2 are carboxylato or are jointly dicarboxylato, where Y.sup.1 and Y.sup.2 are carboxylato, and where Z is a bidentate ligand selected from the group consisting of diaminocyclohexane and ethylenediamine.

10. The method of claim 9, where X.sup.1 and X.sup.2 are carboxylato having between about 1-10 carbon atoms each or are jointly dicarboxylato having between about 2-20 carbon atoms, and where Y.sup.1 and Y.sup.2 are carboxylato having between about 1-10 carbon atoms each.

11. The method of claim 9, where X.sup.1 and X.sup.2 are selected from the group consisting of

acetato,

trifluoroacetato, and

cyclobutanecarboxylato,

or are jointly selected from the group consisting of

oxalato,

malonato,

methylmalonato,

ketomalonato,

tartronato, and

1. 1-cyclobutanedicarboxylato.

12. The method of claim 9, where Y.sup.1 and Y.sup.2 are selected from the group consisting of

acetato,

trifluoroacetato, and

cyclobutanecarboxylato.