Phase I clinical trial of carbetimer.

Carbetimer (carbethimer, N-137, NED-137, carboxyimamidate) is a low molecular weight polyelectrolyte with antitumor activity in a variety of tumor models. This phase I trial evaluated a single dose of carbetimer infused over 1-2 h every 28 days. Forty-three patients received 71 courses of the drug at doses ranging from 180 to 8500 mg/m2. The dose-limiting toxicity was hypercalcemia (serum calcium greater than 12.5 mg/dl) noted in two of three patients at a dose of 8500 mg/m2. Serum calcium levels between 10.5 and 12.5 mg/dl were noted in an additional three patients treated at doses greater than or equal to 1600 mg/m2. Calcium balance studies in three patients treated at 6500 mg/m2 revealed an increase in urinary cyclic AMP and phosphate excretion after treatment accompanied by a mild elevation of serum parathyroid hormone. Immunological studies in these patients revealed a statistically significant increase in the percentage of peripheral T-helper cells. An increase in the T-helper/suppressor cell ratio was observed in two of the three patients studied. Interleukin 2 production by phytohemagglutinin-stimulated peripheral mononuclear cells was increased in two of three patients. One patient with a renal cell carcinoma showed a mixed response. The recommended dose for phase II trials as assessed from this study is 6500 mg/m2 as a single dose every 28 days.