Oxaliplatin/cisplatin (L-OHP/CDDP) combination in heavily pretreated ovarian cancer

Inhibition of telomerase activity and cell proliferation by a reverse transcriptase inhibitor in gynaecological cancer cell lines

Telomerase is a ribonucleoprotein which has a RNA template to bind and extend telomere ends, so prolonging the life of tumour cells. The aim of this study was to determine whether transcriptase function of telomerase could be inhibited by the reverse transcriptase inhibitors (RTI); azydothymidine (AZT), dideoxyinosine (ddI) and AZT-5' triphosphate (AZT-TP). We examined their effects on the proliferation of cancer cells and the antitumour effects of cisplatin in vitro. The three agents did not cause major changes in telomerase activity or telomere length in MCAS cells. However, in HEC-1 cells changes in telomerase activity and telomere length were observed that were dependent on the RTI concentration and duration of exposure. ddI and AZT-TP reduced telomerase activity and shortened the length of the telomere. In the presence of RTI, the antitumour effects of cisplatin were enhanced. This was particularly evident in HEC-1 cells where there was a marked reduction in cell proliferation, appearance of morphological changes and senescent-like cells in the presence of ddI or AZT-TP. In MCAS cells, TP53 expression was increased by ddI and AZT-TP, while p21 expression was unchanged. In HEC-1 cells the expression of both TP53 and P21 was increased by ddI. Continuous administration of RTI enhanced the cell growth inhibition of cisplatin. RTI also inhibited the proliferation of some cells.

Oxaliplatin: a review of preclinical and clinical studies

Of the new generation platinum compounds that have been evaluated, those with the 1,2-diaminocyclohexane carrier ligand-including oxaliplatin--have been focused upon in recent years. Molecular biology studies and the National Cancer Institute in vitro cytotoxic screening showed that diaminocyclohexane platinums such as oxaliplatin belong to a distinct cytotoxic family, differing from cisplatin and carboplatin, with specific intracellular target(s), mechanism(s) of action and/or mechanism(s) of resistance. In phase I trials, the dose-limiting toxicity of oxaliplatin was characterized by transient acute dysesthesias and cumulative distal neurotoxicity, which was reversible within a few months after treatment discontinuation. Moreover, oxaliplatin did not display any, auditory, renal and hematologic dose-limiting toxicity at the recommended dose of 130 mg/m2 q three weeks or 85 mg/m2 q two weeks given as a two-hour i.v. infusion. Clinical phase II experiences on the antitumoral activity of oxaliplatin have been conducted in hundreds of patients with advanced colorectal cancers (ACRC). Single agent activity reported as objective response rate in ACRC patients is 10% and 20% overall in ACRC patients with 5-fluorouracil (5-FU) pretreated/refractory and previously untreated ACRC, respectively. Synergistic cytotoxic effects in preclinical studies with thymidylate synthase inhibitors, cisplatin/carboplatin and topoisomerase I inhibitors, and the absence of hematologic dose-limiting toxicity have made oxaliplatin an attractive compound for combinations. Phase II trials combining oxaliplatin with 5-FU and folinic acid ACRC patients previously treated/refractory to 5-FU showed overall response rates ranging from 21% to 58%, and survivals ranging from 12 to 17 months. In patients with previously untreated ACRC, combinations of oxaliplatin with 5-FU and folinic acid showed response rates ranging from 34% to 67% and median survivals ranging from 15 to 19 months. Two randomized trials totaling 620 previously untreated patients with ACRC, comparing 5-FU and folinic acid to the same regimen with oxaliplatin, have shown a 34% overall response rate in the oxaliplatin group versus 12% in the 5-FU/folinic acid group for the first trial; and 51.2% vs. 22.6% in the second one. These statistically significant differences were confirmed in time to progression advantage for the oxaliplatin arm (8.7 vs. 6.1 months, and 8.7 vs. 6.1 months, respectively). A small but consistent number of histological complete responses have been reported in patients with advanced colorectal cancer treated with the combination of oxaliplatin with 5-FU/folinic acid, and secondary metastasectomy is increasingly done by oncologists familiar with the combination. Based on preclinical and clinical reports showing additive or synergistic effects between oxaliplatin and several anticancer drugs including cisplatin, irinotecan, topotecan, and paclitaxel, clinical trials of combinations with other compounds have been performed or are still ongoing in tumor types in which oxaliplatin alone showed antitumoral activity such as ovarian, non-small-cell lung, breast cancer and non-Hodgkin lymphoma. Its single agent and combination therapy data in ovarian cancer confirm its non-cross resistance with cisplatin/carboplatin. While the role of oxaliplatin in medical oncology is yet to be fully defined, it appears to be an important new anticancer agent.

Ongoing and unsaid on oxaliplatin: the hope

Oxaliplatin, the first available diaminocyclohexane platinum, has clinical activity in colorectal and ovarian cancers. Its mechanism of action is thought to be similar to that of cisplatin, its main mechanism being the intrastrand DNA adduct between two adjacent guanins or two adjacent guanine and adenine adducts. Ongoing molecular pharmacological studies of the mechanism of action of cisplatin suggest that platinated adducts are recognized by proteins of the mismatch repair system, including the products of the hMLH1 and hMSH2 genes. DNA mismatch repair defects occur in a wide variety of sporadic human cancers, are the main genetic factor in hereditary non-polyposis colon cancer and a frequent de novo or acquired phenomenon in ovarian cancer and other solid tumours. Moreover, they have recently been reported to be a cause of resistance to cisplatin but not to oxaliplatin, as diaminocyclohexane platinum adducts do not appear to be recognized by the mismatch repair complex. These findings explain the oxaliplatin activity in some cisplatin-resistant tumours. In addition, the good safety profile of oxaliplatin makes it a drug of choice for combination therapy, and it has been shown to be synergistic with other cytotoxic agents, including 5-fluorouracil, cisplatin, carboplatin, topotecan, gemcitabine and CPT-11. The results of several ongoing trials are awaited, but available data demonstrate that oxaliplatin is highly effective in the treatment of advanced colorectal and ovarian cancers. Promising early results suggest that it is also efficacious in non-Hodgkin's lymphoma, breast and non-small-cell lung cancers. As a result of its mechanism of action, its favourable safety profile and the differential profile of its antitumoral activity, the full potential of oxaliplatin as an active, versatile antitumoral agent is yet to be fully explored.

Oxaliplatin in practice

Oxaliplatin, a new third-generation platinum complex, is active in the treatment of colorectal and advanced ovarian cancers, both as monotherapy and in combination therapy. It has demonstrated a very good safety profile, characterized by low haematotoxicity, and moderate and manageable gastrointestinal toxicity. No significant renal or ototoxicities have been observed. Oxaliplatin induces a peripheral sensory neuropathy which is characterized by distal and perioral dysaesthesia, and is induced or exacerbated by the cold; in general, it is regressive between cycles of treatment. This dose-limiting toxicity is cumulative, but reversible within a few months of discontinuation of treatment in the majority of cases. In a cohort study of 490 patients with advanced colorectal cancer included in an extended access programme, more than 2700 cycles of oxaliplatin plus 5-fluorouracil (5-FU) were administered. The overall safety profile of oxaliplatin was shown to be very favourable. Oxaliplatin and cisplatin, each in combination with cyclophosphamide, have a similar efficacy in the treatment of advanced ovarian cancer, but oxaliplatin was better tolerated than cisplatin in terms of haematological, gastrointestinal, neurosensory and renal toxicities. The safety profile of oxaliplatin makes it an ideal candidate for combination therapy.