Phase I clinical trial with carbetimer.

Carbetimer, a low molecular weight polymer derived from ethylene and maleic anhydride, belongs to a class of chemical compounds different from previously available anticancer agents. It has shown moderate antitumor activity against the Madison 109, Lewis lung, colon 26 and M5076 ovarian carcinomas. In the human tumor stem cell assay, antitumor activity was seen against carcinomas of the breast, ovary, lung, colon and kidney. A total of 26 patients with solid tumors were entered into this trial; carbetimer was given on 5 consecutive days as a 1-2-h intravenous infusion. The dose was escalated from 1.08 to 11 g/m2/day. The drug did not induce the usual side-effects of chemotherapy: leukopenia, thrombocytopenia, alopecia and mucositis were minimal or totally absent. Gastrointestinal toxicity was limited to mild to moderate nausea and vomiting; these were observed at all dose levels and required antimetics in only two patients. The major side-effects of carbetimer consisted of hypercalcemia and neurotoxicity. Hypercalcemia was dose- and treatment duration-dependent. The precise mechanism of hypercalcemia is presently under investigation, but remains unclear. Neurotoxicity was observed only after prolonged therapy; two patients, who received cumulative doses higher than 250 g/m2, developed a peripheral neuropathy with paresthesia, decrease in sensory perception and motor weakness. One patient recovered completely; the other patient improved slightly before developing fatal brain metastases. Two patients with malignant melanoma exhibited major antitumor response; both were previously treated; after excellent partial responses to carbetimer, both were operated on and one is presently disease-free 2 1/2 years after completion of therapy with carbetimer. In conclusion, carbetimer is a new compound with an unusual pattern of side-effects and interesting antitumor activity against malignant melanoma. Its antitumor activity is presently being investigated in phase II trials.