Genomic imbalances associated with acquired resistance to platinum analogues.

During the past several years, a panel of human tumor cell lines (predominantly ovarian) with acquired resistance to cisplatin, the orally bioavailable analogue JM216, and the structurally hindered analogue AMD473, has been established and characterized for underlying mechanisms of resistance. We have examined these resistant cell lines for gains and losses of DNA associated with the acquisition of resistance using the molecular cytogenetic technique of comparative genomic hybridization. Our comparison of three analogues has shown the most frequently observed changes to include amplification of 4q (5/7) and 6q (5/7), followed by amplification of 5q (3/7). We have defined four minimal common overrepresented regions, two each on 4q and 6q, which are potential loci of genes associated with platinum analogue resistance. Additional consistent abnormalities appear to be associated with cell lines sharing specific resistance mechanisms. For example, amplification of 12q was observed in the CH1 lines made respectively resistant to JM216 and AMD473 in which increased DNA repair appears to be a major mechanism of resistance for both agents. Hence, these comparative genomic hybridization studies have identified distinct chromosomal aberrations which may correlate with defined mechanisms of resistance and contain hitherto unrecognized genes that may provide targets for future therapeutic intervention.

Phase I and pharmacokinetic study of an oral platinum complex given daily for 5 days in patients with cancer.

PURPOSE: We aimed to determine the maximum-tolerated dose (MTD) clinical toxicities, pharmacokinetics, and pharmacodynamics of oral JM216 given once daily for 5 days to cancer patients. PATIENTS AND METHODS: Patients who fulfilled standard phase I trial criteria were enrolled. Oral JM216 was given at doses based on patient body-surface area, on an empty stomach, once daily for 5 consecutive days, as 10-, 50-, and 200-mg hard gelatin capsules and with oral antiemetics. The pharmacokinetics of platinum were studied on days 1 and 5 of the first treatment course using atomic absorption spectrophotometry (AAS). RESULTS: Thirty-two patients received 94 courses of oral JM216 at doses that ranged from 30 to 140 mg/m2 body-surface area for 5 consecutive days. The MTD was 140 mg/m2/d. The dose-limiting toxicities were thrombocytopenia and neutropenia. Hematotoxicity was reversible (nadir, 17 to 21 days; recovery, 28 days), noncumulative, and dependent on the dose and history of previous therapy. There were two instances of neutropenic sepsis. Two-thirds of patients experienced mild nausea, vomiting, or diarrhea. There was no ototoxicity, neurotoxicity, nephrotoxicity, or objective tumor responses. There was a significant correlation between JM216 dose and the day 1 and 5 plasma ultrafiltrate area under the concentration-time curve (AUC; r = .78), which indicates linear pharmacokinetics. There was considerable intersubject pharmacokinetic and pharmacodynamic variability, but a significant sigmoidal relationship between the plasma ultrafiltrate AUC and severity of thrombocytopenia (R2 = .83). CONCLUSION: We recommend JM216 doses of 100 and 120 mg/m2/d x 5 for previously treated and untreated patients, respectively, for phase II trials.

The cytotoxic action of four ammine/amine platinum(IV) dicarboxylates: a flow cytometric study.

We have used flow cytometry to study the mechanism of cytotoxic action of a series of ammine/amine Pt(IV) dicarboxylates [ammine diacetatodichloro(cyclohexylamine) platinum(IV), JM216; ammine dibutyratodichloro(cyclohexylamine)platinum(IV), JM221; ammine diacetatodichloro(propylamine)platinum(IV), JM223; ammine dibenzoatodichloro(propylamine)platinum(IV), JM244]. JM216 has been shown to have clinical potential and has recently entered phase II trials. All the compounds caused a slowdown in S-phase transit followed by a block in G2. Cells died either through apoptosis (largely during S-phase) or by failing to overcome the G2 block (some days after treatment). In G2, the cells either divided or enlarged and died. At equitoxic doses, JM216 showed the most apoptotic cells and had the most platinum bound to the DNA; JM244 showed the fewest apoptotic cells and had the least platinum bound to DNA. We suggest that whether apoptosis was triggered or not was governed by the total amount of Pt bound to the DNA; the type of lesion was more important in determining whether a cell became blocked in G2.

Phase I trial of ZD1694, a new folate-based thymidylate synthase inhibitor, in patients with solid tumors.

PURPOSE: To perform a phase I clinical and pharmacologic study of ZD1694 (Tomudex, Alderley Park, United Kingdom), a new folate-based thymidylate synthase (TS) inhibitor, in patients with advanced malignancy. PATIENTS AND METHODS: From February 1991 to January 1993, 61 patients with a range of solid tumor received 161 courses of ZD1694 given as a single 15-minute intravenous infusion every 3 weeks, at escalating doses from 0.1 to 3.5 mg/m2. Pharmacokinetic (PK) analysis was performed with the first two courses of treatment. There were 33 men and 28 women with a median age of 53 years (range, 21 to 73). Fifty-five patients (90%) had previously received chemotherapy. RESULTS: Reversible liver toxicity and dose-related gastrointestinal (GI) and bone marrow toxicity occurred at > or = 1.6 mg/m2. Liver function usually returned to normal with repeated treatment, but GI and bone marrow toxicities generally became more severe. No renal toxicity was observed. The maximum-tolerated dose (MTD) was 3.5 mg/m2, at which, in addition to antiproliferative toxicities, four of six patients (67%) developed severe malaise that consisted of anorexia, nausea, and asthenia, with rapidly decreasing performance status that limited re-treatment. Abnormal liver function was also seen in four patients (67%). At 3.0 mg/m2, grades III and IV diarrhea were seen in six of 23 patients (26%) and grade IV myelosuppression in two others. Liver toxicity was self-limiting and not associated with severe malaise. Two patients had a partial response to treatment. PK analysis showed that plasma elimination was triexponential, with pronounced variability in the mean terminal half-life (t1/2gamma) for a given dose ranging from 8.2 to 105 hours. There was a linear relationship between dose and both the area under the concentration-time curve (AUC) and maximum concentration (Cmax), but no clear association between these parameters and response or toxicity. CONCLUSION: The dose of ZD1694 recommended for phase II trials is 3.0 mg/m2.

Biotransformation of the platinum drug JM216 following oral administration to cancer patients.

This study evaluates the metabolic profile of JM216 [bis(acetato)ammine-dichloro(cyclohexylamine) platinum(IV)], the first orally administrable platinum complex, in plasma ultrafiltrates of 12 patients (n = 2-4 time points per patient) following different doses of drug (120, 200, 340, 420, 560 mg/m2). The biotransformation profile was evaluated by high-performance liquid chromatography (HPLC) followed by atomic absorption spectrophotometry (AA). The AA profiles were compared with those previously identified by HPLC on line with mass spectrometry (HPLC-MS) in plasma incubated with JM216. A total of six platinum peaks (Rt = 5.5, 7.2, 10.6, 12.4, 15.6, and 21.6 min, respectively) were observed in patients' plasma ultrafiltrate samples, of which only four appeared during the first 6 h post-treatment. Four of these coeluted with those observed and identified previously in plasma incubation medium. No parent JM216 was detected. The major metabolite seen in patients was the Pt II complex JM118 [cis-amminedichloro-(cyclohexylamine)platinum(II)] and was observed in all the patients. Interestingly, the second metabolite was shown to coelute with the Pt IV species JM383 [bis-acetatoammine(cyclohexylamine)dihydroxoplatinum (IV)]. Both JM118 and JM383 were identified by HPLC-MS in a clinical sample. Peak C, which was a minor product (less than 5% of the free platinum), coeluted with JM559 [bis-acetatoammine-chloro(cyclohexylalamine)hydroxoplatin um(IV)]. The cytotoxicity profile of all three metabolites in a panel of cisplatin-sensitive and -resistant human ovarian carcinoma cell lines was very close to that of the parent drug. In addition, the concentrations of JM118 reached in patients' plasma ultrafiltrate were comparable with the cytotoxic levels of the compound determined in the ovarian carcinoma panel of cell lines. Two metabolites were seen in patients but not in the in vitro incubation medium, suggesting the involvement of a possible enzymatic reaction. Thus, the biotransformation profile following oral administration of JM216 shows a variety of Pt(IV) and Pt(Il) metabolites in plasma that differ significantly from other systemically applied platinum drugs.

Novel trans platinum complexes: comparative in vitro and in vivo activity against platinum-sensitive and resistant murine tumours.

Two pairs of cis/trans platinum complexes, JM118 (cis-ammine(cyclohexylamine) dichloro platinum(II)) and its trans counterpart, JM334 and JM149 (cis-ammine(cyclohexylamine) dichloro-dihydroxo platinum(IV)) and its trans counterpart JM335 have been evaluated (both in vitro and in vivo) against two murine tumour models of historical importance in the discovery of novel platinum drugs; the ADJ/PC6 plasmacytoma and the L1210 leukaemia and sublines selected for resistance to platinum drugs. In vitro, results showed that the trans complexes induced comparable growth inhibitory properties to those observed for cisplatin and their respective cis isomers. Moreover, retention of activity was observed in a series of 5 acquired platinum drug (cisplatin, carboplatin, iproplatin, tetraplatin and JM149)-resistant L1210 sublines whereas at least partial cross-resistance was observed to the cis isomer JM149 in the acquired carboplatin and iproplatin-resistant lines (in addition to being 11-fold resistant in the line selected for resistance to JM149 itself). In vivo, JM355 showed activity against both the ADJ/PC6 and L1210 models of acquired cisplatin resistance. Furthermore, JM355 was active against an ADJ/PC6 subline possessing resistance to iproplatin and a L1210 subline possessing resistance to its cis isomer JM149. Interestingly, the trans platinum(II) counterpart of JM335(JM334) was inactive in vivo. These data indicate that the trans platinum(IV) complex JM335 possess several in vitro growth inhibitory- and in vivo antitumour properties which are distinct from those observed for cisplatin (or its cis isomer). Thus, JM335 contravenes the original structure-activity rules determined for platinum-containing compounds and, because of its level of activity against cisplatin-resistant tumours, establishes the complex as of interest in the search for new platinum drugs active against cisplatin-resistant disease.

cis-Diamminedichloroplatinum(II)-induced cell death through apoptosis in sensitive and resistant human ovarian carcinoma cell lines.

We have studied the effects of the chemotherapeutic drug cis-diamminedichloroplatinum(II) (cis-platin) on three human ovarian carcinoma cell lines - one sensitive to the drug (CH1), one with acquired resistance (CH1cisR) and one with intrinsic resistance (SKOV-3). Previous work has shown that the 50% inhibitory concentrations (IC50 values) after a 2-h exposure to the drug are: CH1, 2.5 microM; CH1cisR, 7.5 microM; and SKOV-3, 33 microM. Despite the variation in sensitivity, the amount of Pt bound to DNA and the rate of removal of Pt was similar for the three lines. There were significant differences in the rates of formation of DNA cross-links but these were not large enough to account for the high resistance of the SKOV-3 line. We have reported that in the L1210 murine leukaemia cell line there are two mechanisms of cisplatin-induced cell death - one of which involves apoptosis. In this paper, we report on an investigation into whether sensitivity to apoptosis played a role in the resistance of these ovarian lines toward cisplatin. After a 2-h incubation with the drug, cells from the three lines showed evidence of death through apoptosis. The cells detached from the culture dish in a time- and dose-dependent fashion. These cells morphologically were quite distinctive from the attached cells and showed changes in their chromatin structure indicative of apoptosis. Their DNA had not been degraded into oligonucleosomal fragments (200 bp and multiples thereof) but had been cut into larger fragments (30 kilobase pairs, kbp) of a size associated with chromatin domains (chromatin loops). At equitoxic doses of drug, the quantity of cells undergoing apoptosis was similar for the three cell lines. The most prominent effect on cell-cycle kinetics was a slowdown in S-phase transit during which the cells underwent apoptosis. Cells that successfully completed the S phase subsequently suffered a temporary G2 block. We propose that the sensitivity of these cell lines to cisplatin was governed by their ability to handle damage caused by platination of the DNA and that the major mechanism of cisplatin-induced cell death in all three cell lines was the induction of apoptosis.

Tomudex (ZD1694): from concept to care, a programme in rational drug discovery.

Folate-based anticancer drugs with specificity for thymidylate synthase (TS) have come of age. Ideas nurtured in the early 1970s led to the first-generation of antifolates with TS and dihydrofolate reductase (DHFR) inhibitory activities. Compounds with increased selectivity for TS followed with the highly specific inhibitor, CB3717 being synthesised in 1979 at the Institute of Cancer Research (ICR). CB3717 had significant clinical activity but its development had to be abandoned because its low aqueous solubility led to occasional nephrotoxicity. Collaborative laboratory studies between the ICR and ICI Pharmaceuticals (later to become Zeneca Pharmaceuticals) led to the discovery of ZD1694 (Tomudex), the first antifolate to be licensed for the treatment of cancer (UK 1995) in nearly 40 years and the first new drug for colorectal cancer in about 35 years. Tomudex belongs to a class of compounds that use the reduced-folate carrier (RFC) for uptake into cells and which are excellent substrates for folylpolyglutamate synthetase (FPGS). This paper reviews the underlying philosophies, and the milestones reached during the development of Tomudex.

Preclinical pharmacology and antitumour activity of the novel sequence-selective DNA minor-groove cross-linking agent DSB-120.

We examined the in vitro cytotoxicity, antitumour activity and preclinical pharmacokinetics of the novel sequence-selective, bifunctional alkylating agent DSB-120, a synthetic pyrrolo[1,4][2,1-c]benzodiazepine dimer. DSB-120 was shown to be a potent cytotoxic agent in vitro against a panel of human colon carcinomas [50% growth-inhibitory concentration (IC50) 42 +/- 7.9 nM, mean +/- SE, n = 7] and two rodent tumours (L1210 and ADJ/PC6). Antitumour activity was assessed in the bifunctional alkylating-agent-sensitive murine plasmacytoma ADJ/PC6 using a variety of administration protocols. The maximal antitumour effects were observed following a single i.v. dose but the therapeutic index was only 2.6. DSB-120 was less effective when given i.p. either singly or by a daily x 5 schedule. After a single i.v. dose at the maximum tolerated dose (MTD, 5 mgkg-1) the plasma elimination was biphasic, with a short distribution phase (t1/2 alpha 4 min) being followed by a longer elimination phase (t1/2 beta 38 min). Peak plasma concentrations were 25 micrograms ml-1, the clearance was 1.3 ml g-1 h-1 and the AUC0-infinity was 230 micrograms ml-1 min. Concentrations of DSB-120 in ADJ/PC6 tumours were very low, showing a peak of 0.4 micrograms g-1 at 5 min. The steady-state tumour/plasma ratio was about 5% and the AUC was only 2.5% of that occurring in the plasma. DSB-120 appeared to be unstable in vivo, with only 1% of an administered dose being recovered unchanged in 24-h urine samples. Plasma protein binding was extensive at 96.6%. In conclusion, the poor antitumour activity of DSB-120 may be a consequence of low tumour selectivity and drug uptake as a result of high protein binding and/or extensive drug metabolism in vivo.

Determination of metabolites of a novel platinum anticancer drug JM216 in human plasma ultrafiltrates.

The present study describes the application of on-line liquid chromatography-electrospray ionisation in conjunction with a high resolution magnetic sector mass spectrometer to identify metabolites of a platinum(IV) anticancer drug JM216 [bis(acetato)amminedichloro(cyclohexylamine)platinum(IV)] in human plasma. Four metabolites were identified following incubation of JM216 in human plasma: JM118 [amminedichlorocyclohexylamineplatinum(II)], a platinum(II) complex; JM383 [bis(acetato)amminedihydroxo(cyclohexylamine)platinum(IV)]; JM518 [bis(acetato)amminechloro(cyclohexylamine)hydroxoplatinum (IV)] and its isomer JM559. The platinum complexes mass spectra were dominated by the natriated [M + Na]+ ion. Elemental compositions of these natriated ions were confirmed by accurate mass measurement on a magnetic sector mass spectrometer in the course of LC/MS analysis. This study demonstrates the capability of direct LC-ESI/MS with accurate mass measurement for analysis of platinum complexes in biological samples. Our results suggest that LC-ESI/MS is a powerful technique for structure elucidation of novel metabolites, and could make valuable contributions to drug metabolism research.

Metabolic studies of an orally active platinum anticancer drug by liquid chromatography-electrospray ionization mass spectrometry.

Bis(acetato)amminedichloro(cyclohexylamine) platinum(IV) (JM216) is a new orally administered platinum complex with antitumor properties, and is currently undergoing phase II clinical trials. When JM216 was incubated with human plasma ultrafiltrate, 93% of the platinum species were protein-bound and 7% were unbound. The unbound platinum complexes in the ultrafiltrates of human plasma were analysed using a liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method. Apart from the parent drug, four metabolites were identified and characterised. These include JM118 [amminedichloro(cyclohexylamine) platinum(II)], JM383 [bis(acetato)ammine(cyclohexylamine)dihydroxo platinum(IV)] and the two isomers JM559 and JM518 [bis(acetato)amminechloro(cyclohexylamine) hydroxo platinum(IV)]. Their elemental compositions were determined by accurate mass measurement during the LC analysis, to confirm their identities. Quantitation of these metabolites by off-line LC atomic absorption spectroscopy demonstrated that JM118 is the major metabolite in plasma from patients receiving JM216 treatment.

Initiatives with platinum- and quinazoline-based antitumor molecules--Fourteenth Bruce F. Cain Memorial Award Lecture.

Carboplatin is a better-tolerated alternative to cisplatin. JM216, the first p.o.-administrable platinum complex possesses toxicities comparable to carboplatin in Phase I studies. Together with the trans-platinum complex JM335, it provides new chemical guidelines for the development of compounds that may circumvent cisplatin resistance in tumors. Systematic structure-activity investigations have led to the discovery and development of ZD1694 (Tomudex), an inhibitor of thymidylate synthase that exploits both the reduced folate carrier and folylpolyglutamate synthetase as major determinants of its growth-inhibitory activity. Phase II studies have revealed encouraging activity against colon cancer, and Phase III studies are nearing completion. An associated structure-activity investigation has led to the development of ZD9331, a potent thymidylate synthase inhibitor which exploits the reduced folate carrier for cell entry, but which is independent of polyglutamation for its thymidylate synthase-inhibitory activity. This compound possesses antitumor activity in vivo and has been selected for full development.

ZD1694 (Tomudex): a new thymidylate synthase inhibitor with activity in colorectal cancer.

ZD1694 (Tomudex) is a new antifolate which is a specific inhibitor of thymidylate synthase (TS). Evidence suggests that ZD1694 has a spectrum of activity that only partially overlaps with 5-fluorouracil (modulated with leucovorin) against colon tumours in vitro. Potent cytotoxic activity is dependent upon active uptake into cells via the reduced folate/methotrexate cell membrane carrier (RFC) and subsequent metabolism to polyglutamated forms (tri, tetra and pentaglutamates). These polyglutamates are approximately 60-fold more active as TS inhibitors and are not effluxed readily from cells. Extensive polyglutamation also occurs in various mouse tissues (e.g. small intestinal epithelium, liver and kidney), resulting in high tissue/plasma drug ratios which persist for a prolonged period. ZD1694 has antitumour activity in mice, although the high plasma thymidine in this species complicates: (1) the interpretation of therapeutic index; (2) tumour types in which activity is likely to be observed; and (3) translation of doses and schedules for clinical evaluation. ZD1694 entered clinical study and has completed Phase I and II evaluation, with activity observed in several tumour types. Appreciable activity in the Phase II colorectal study (29% objective response rate on interim analysis) led to the current Phase III study, randomised against 5-fluorouracil/leucovorin.

A novel trans-platinum coordination complex possessing in vitro and in vivo antitumor activity.

As part of a drug discovery program to discover more effective platinum-based anticancer drugs, a series of platinum complexes of trans coordination geometry centered on trans-ammine(cyclohexylaminedichlorodihydroxo)platinum(IV) (JM335) has been evaluated in vitro against a panel of cisplatin-sensitive and cisplatin-resistant human tumor cell lines (predominantly ovarian). In vitro, against 5 human ovarian carcinoma cell lines, JM335 was comparably cytotoxic to cisplatin itself and over 50-fold more potent than transplatin (mean 50% inhibitory concentrations: JM335, 3.1 microM; cisplatin, 4.1 microM; transplatin, 162 microM). With the use of seven pairs of human tumor cell lines (parent and subline with acquired resistance to cisplatin and encompassing all of the known major mechanisms of resistance to cisplatin) JM335 exhibited a different cross-resistance pattern to that of its cis isomer (JM149). JM335 showed non-cross-resistance in six of the seven resistant lines, cross-resistance in the A2780cisR line possibly being associated with high levels of glutathione. Preliminary intracellular DNA binding studies showed that in contrast to transplatin, JM335 was efficient at forming DNA-DNA interstrand cross-links. In vivo, JM335 produced growth delays in excess of 15 days against 4 of 6 human ovarian carcinoma xenografts and was unique among the complexes studied in retaining some efficacy against a cisplatin-resistant subline of the murine ADJ/PC6 plasmacytoma. JM335 is the first trans-platinum complex to demonstrate marked antitumor efficacy against both murine and human s.c. tumor models and represents a significant structural lead to complexes capable of circumventing cross-resistance to cisplatin.

Circumvention of acquired tetraplatin resistance in a human ovarian carcinoma cell line by a novel trans platinum complex, JM335 [trans ammine (cyclohexylamine) dichloro dihydroxo platinum (IV)].

Acquired resistance to tetraplatin [d,1-trans-1,2-diaminocy-clohexane tetrachloroplatinum (IV)] has been generated in vitro in the human ovarian carcinoma cell line PXN94; the derived line, PXN94tetR, was 24-fold resistant to tetraplatin. Intracellular tetraplatin accumulation was reduced in PXN94tetR compared with PXN94 by an average of 1.3-fold across the concentration range 1-100 microM (2 hr exposure). There was no significant difference in glutathione levels between the 2 cell lines. PXN94tetR was 1.6-fold more resistant to cadmium chloride than PXN94, suggesting that metallothionein levels may be elevated. However, no significant difference was observed between PXN94 and PXN94tetR in the levels of total platinum bound to DNA or DNA interstrand cross-links immediately after tetraplatin exposure (10-100 microM x 2 hr). There was also no significant difference between the 2 cell lines in the rate of removal of total platinum or interstrand cross-links from DNA following 2 hr exposure to 25 microM tetraplatin. Hence the major mechanism of acquired tetraplatin resistance in PXN94tetR appears to be increased tolerance of platinum-DNA adducts. PXN94tetR was partially cross-resistant to the bifunctional alkylating agents melphalan, chlorambucil and mitomycin C. Partial cross-resistance was also observed to Adriamycin, bleomycin, etoposide, 5-fluorouracil and vinblastine; however, no elevation in P-glycoprotein levels was apparent in PXN94tetR. No cross-resistance was observed to taxotere. PXN94tetR was partially cross-resistant to cisplatin, carboplatin and several novel cis platinum complexes. In contrast, resistance was completely circumvented by the novel trans platinum complex JM335 [trans ammine (cyclohexylamine) dichloro dihydroxo platinum (IV)].

Evaluation of novel ammine/amine platinum (IV) dicarboxylates in L1210 murine leukaemia cells sensitive and resistant to cisplatin, tetraplatin or carboplatin.

Seventeen alkylamine ammine dicarboxylatodichloroplatinum(IV) complexes of general structure c,t,c-[PtCl2(OCOR1)2NH3(RNH2)], where R = aliphatic or alicyclic and R1 = aliphatic or aromatic, have been evaluated against L1210 cell lines with acquired resistance to cisplatin (10-fold), tetraplatin (34-fold) or carboplatin (14-fold) using an in vitro growth-delay assay. All of these compounds overcame cisplatin, tetraplatin and carboplatin resistance. Potency increased as the number of carbon atoms in the axial aliphatic ligands (R1) increased, for example comparing JM216 (R = cyclohexyl, R1 = CH3, IC50 = 1.2 microM) with JM274 (R = cyclohexyl, R1 = n-C4H9, IC50 = 0.05 microM) against the parent sensitive line (L1210/S). The most active compounds were those possessing aromatic ligands at R1, regardless of whether R = aliphatic or alicyclic, for example JM244 (R = n-C3H7, R1 = C6H5, IC50 = 0.028 microM) and JM2644 (R = c-C6H11, R1 = C6H5, IC50 = 0.031 microM) against L1210/S. For an alicyclic alkylamine series in which R is varied from c-C3H7 to C-C7H13, with R1 = n-C3H7 for each compound, cytotoxic potency was maximised at c-C6H11 (JM221, IC50 = 0.06 microM against L1210/S). Preliminary biochemical studies, at equitoxic doses, comparing JM221 (0.1 microM) with cisplatin (0.6 microM) identified five times more platinum associated with JM221 treated cells and 1.5 times more platinum bound to the DNA of JM221-treated cells. The lipophilic properties of some of these platinum(IV) dicarboxylates may contribute to both the potency and circumvention of resistance by these compounds.

Schedule dependency of orally administered bis-acetato-ammine-dichloro-cyclohexylamine-platinum(IV) (JM216) in vivo.

JM216 is a novel antitumor platinum(IV) complex displaying oral activity, dose-limiting myelosuppression, and a lack of nephro- and neurotoxicity in rodents. It has been selected for clinical evaluation. The schedule dependency of its antitumor action against a murine (ADJ/PC6 plasmacytoma) and a human tumor model (PXN109T/C ovarian carcinoma xenograft) was studied in vivo. Single dose (q21d), once a day dosing for 5 consecutive days (q21d or q28d), and once a day dosing indefinitely (chronic daily dosing) administration schedules were compared. Against the murine ADJ/PC6 plasmacytoma, daily x5 administration improved the tolerance, antitumor potency, and therapeutic index of oral JM216, compared to single dose administration, whereas no advantage was found for fractionating cisplatin dosages. Against the PXN109T/C human ovarian carcinoma xenograft, oral JM216, given at dose levels delivering a equivalent total dose on single dose (200 mg/kg q21d), daily x5 (40 mg/kg/day q21d) and chronic daily dosing (9.5 mg/kg/d) schedules, showed superior tumor growth delays (55 +/- 15 days; P < 0.05) and maximal tumor regression (10 +/- 11% of initial tumor volume; P < 0.001) with the daily x5 schedule. Gastrointestinal toxicity (P < 0.05) and mild nephrotoxicity (P < 0.01) complicated the chronic daily dosing schedule, while leukopenia (P < 0.02) and thrombocytopenia (P < 0.01) were dose-limiting for the single dose and daily x5 administration, respectively. Peak plasma ultrafiltrate (PUF) platinum levels were below cytotoxic levels (PUF Cmax, 0.11 +/- 0.066 mg/l) at the maximally tolerable dose for the chronic dosing schedule (9.5 mg/kg). Peak PUF platinum levels did not increase significantly with a 5-fold increase in dosage from 40 mg/kg (PUF Cmax 1.5 +/- 0.11 mg/l) to 200 mg/kg (PUF Cmax, 2.4 +/- 0.44 mg/l; P > 0.05). In conclusion, these data demonstrate antitumor schedule dependency for oral JM216 in vivo, independently in two tumor model systems, and with nonlinear pharmacokinetics after its oral administration to mice. Optimal antitumor activity, tolerance, and pharmacokinetics occurred with daily x5 dosing, and this has prompted the clinical evaluation of this administration schedule.

Cisplatin induces apoptosis in a human ovarian carcinoma cell line without concomitant internucleosomal degradation of DNA.

After treatment of the human ovarian carcinoma cell line, CH1, with cisplatin, cells detached from the culture dish in a time- and dose-dependent fashion. These cells showed morphological changes indicative of apoptosis. Their DNA had not been degraded into oligonucleosomal fragments, but the DNA had been cut into larger fragments (30 kbp) of a size associated with chromatin loops. We conclude that cisplatin killed these ovarian cells by inducing apoptosis. However, in these cells, apoptosis was not accompanied by internucleosomal degradation of DNA. Our data are consistent with the hypothesis that the introduction of a double-strand break at a specific site in the chromatin loops is an early event in apoptosis. This degradation is accompanied by morphologically observable changes in chromatin structure. Internucleosomal degradation, when it occurs, is a late event.

Lack of neurotoxicity of oral bisacetatoamminedichlorocyclohexylamine-platinum(IV) in comparison to cisplatin and tetraplatin in the rat.

This study compared the effect on sensory nerve conduction velocity in the hind limb of chronically treated age-matched rats of a novel lipophilic p.o. platinum complex [bisacetatoamminedichlorocyclohexylamine-platinum(IV)], with that of neurotoxic platinum complexes cisplatin and tetraplatin. Tetraplatin (i.p.) first caused slowing of sensory nerve conduction (-14.4% of controls; P < 0.05) at a dose (1 mg/kg) that was free of constitutional toxicity. Cisplatin (i.p.) first caused slowing of sensory nerve conduction (-17.5% of control; P < 0.05) at a dose (2 mg/kg) approximating the maximal tolerated dose. Bisacetatoamminedichlorocyclohexylamineplatinum(IV) (p.o.) showed no slowing of sensory nerve conduction either after 20.5 weeks of treatment at a dose (25 mg/kg) approximating the maximal tolerated dose or after 6 weeks of treatment at a dose (50 mg/kg) which eventually proved intolerable. In conclusion, p.o. bisacetatoamminedichlorocyclohexylamineplatinum(IV) shows a lack of neurotoxicity compared to parenterally administered cisplatin and tetraplatin at the maximal tolerated dose in rats.