Phase I and pharmacokinetic studies with the pentacyclic pyrroloquinone mitoquidone

The comparative disposition of the pyrolloquinone GR63178A and its 9-hydroxy metabolite GR54374X in sensitive and resistant mouse colon adenocarcinoma

The novel anticancer compound GR63178A is being evaluated in the clinic, having demonstrated activity against a wide range of experimental tumour systems in animals without significant toxic side-effects being apparent. In this work, we have demonstrated significant antitumour action of this compound against one murine colon cancer model (colon 38 tumour in BDF-1 mice, specific growth delay = 1.2) when given at 10 mg/kg over 21 consecutive days and in contrast shown minimal sensitivity of another similar murine colon adenocarcinoma, MAC 26, in NMRI mice with the same dose regime. We investigated the disposition of both the parent drug and the 9-OH metabolite (GR54374X) in plasma, tissues and tumours, using solid phase extraction followed by reversed-phase high performance liquid chromatography. Although plasma clearance profiles of GR63178A were similar, significant differences were seen in the disposition of the drug to major organs in two mouse strains. Noteably, the liver and kidneys of the sensitive model had higher levels of parent drug and 9-OH metabolite at both 30 min and 4 h post-injection. However, this was not apparent in the tumours themselves, and the levels of 9-OH metabolite were lower in the plasma and higher in the urine of the sensitive mice, indicating possible rapid renal clearance of this compound. Neither GR63178A nor GR54374X proved cytotoxic in in vitro experiments. The data presented here have revealed considerable variation in drug handling by these two mouse strains, but this did not produce different levels of either parent drug or GR54374X in the tumours, which are the presumed targets, suggesting that differences in disposition are probably not responsible for the different sensitivities of the two tumours. Other possible explanations include the production of a hitherto undetected ultimate cytotoxic metabolite in the sensitive, but not in the resistant, mouse/tumour combination, or differences in inherent tumour sensitivity, or in host-mediated effects. These possibilities are discussed.

Phase II trials of fosquidone (GR63178A) in carcinoma of the breast, head and neck, ovary and melanoma

A total of 91 eligible patients with metastatic cancer have been treated in a series of phase II trials of the novel pentacyclic pyrroloquinone, fosquidone. Tumour types were breast (24), ovary (25), head and neck (21) and melanoma (21). All patients, except those with melanoma had received prior chemotherapy. The drug was given intravenously as a 20 min infusion, at the dose of 120 mg/m2 on days 1 to 5 of a 3 week cycle. Treatment was well tolerated; the only significant side-effects being mild headaches and generalised musculo-skeletal pains. Response was assessed after 2 cycles of therapy. Only one patient (with head and neck cancer) achieved an objective partial response, lasting 6 weeks. A total of 12 patients demonstrated stable disease for a median duration of 15 to 20 weeks. Using this schedule of administration, fosquidone has no significant antitumour activity in this group of tumours.

Phase II trials of fosquidone, (GR63178A), in colorectal, renal and non-small cell lung cancer. CRC Phase II Clinical Trials Committee

A total of 61 eligible patients with metastatic cancer have been treated in a series of Phase II trials of the novel pentacyclic pyrroloquinone, fosquidone. Tumour types were colorectal (23), renal (21), and non small cell lung (17). No patient had received prior chemotherapy. The drug was given intravenously as a 20 min infusion at the dose of 120 mg-2 on days 1 to 5 every 3 weeks. Treatment was well tolerated; the only significant side effects being mild nausea and generalised musculo-skeletal pains. Response was assessed after two cycles of therapy. No patient achieved an objective partial response. A total of nine patients demonstrated stable disease for a median duration of 11 weeks. Using this schedule of administration, fosquidone has no significant antitumour activity in this group of tumours.

A phase I and pharmacology study of GR63178A, a water-soluble analogue of mitoquidone

GR63178A is a water-soluble analogue of mitoquidone, a pentacyclic pyrroloquinone. This group of drugs exhibit a novel structure and activity against several murine solid tumours and xenografts. In the present phase I study the toxicity and pharmacokinetics of GR63178A given on 5 consecutive days of a 21-day cycle were examined. A total of 24 patients presenting with a wide range of tumours were treated at 5 doses escalated to reach the maximal tolerated dose (MTD). Linear pharmacokinetics was documented over the dose range studied, and there was no difference in parent drug handling between day 1 and day 4 of dosing. A number of metabolites were detected. The toxicity profile was unusual in that pain occurred in 20/24 patients, most often at the site of known disease. This was the dose-limiting toxicity. Other side effects included nausea and vomiting (23/24), phlebitis at the infusion site (6/24) and headache (7/24). No treatment response was seen in this study. The MTD was demonstrated to be 160 mg/m2 daily (total, 800 mg/m2 per treatment cycle). The drug has now entered phase II trials at 120 mg/m2 daily x 5, repeated every 21 days.

Chromatographic characterisation of six human metabolites of the new anticancer drug GR63178A

GR63178A is the second pentacyclic pyrroloquinone to enter clinical trials as an anticancer drug. We developed a reversed-phase, gradient-elution high-performance liquid chromatography (HPLC) method along with a Bond Elut C2 mini-column sample-preparation technique for the analysis of GR63178A, its 9-hydroxy-metabolite GR54374X and internal standard GR70440A in human plasma and urine. The limit of detection is 2 ng/ml for both GR63178A and GR54374X. Analysis of GR63178A is complicated by its light instability, whereby a number of chromatographically distinct, stable degradation products can form. These can be practically eliminated if clinical specimens are frozen immediately and all subsequent sample preparation is performed in a darkroom. Using this methodology, a total of six metabolites (including GR54374X) were detected in human plasma and urine specimens. The five new metabolites were characterised according to polarity (HPLC retention time), UV-visible absorption maxima and the effect of incubation with beta-glucuronidase and aryl-sulphatase. Application of this methodology to the analysis of GR63178A will aid in the development of this novel synthetic anticancer drug.