Clinical and Pharmacologic Study of the Novel Prodrug Delimotecan (MEN 4901/T-0128) in Patients with Solid Tumors

Purpose: To investigate i.v. administration of delimotecan (MEN 4901/T-0128), a carboxymethyldextran polymer prodrug of the active camptothecin derivative T-2513, and to assess the maximum tolerated dose, safety profile, clinical pharmacology, and antitumor activity of delimotecan and metabolites.

Experimental Design: Patients with solid tumors refractory to standard therapy received i.v. delimotecan as 3-hour infusion once every 6 weeks. The starting dose was 150 mg/m(2), followed by an accelerated dose escalation with at least one patient per dose level. The pharmacokinetics of delimotecan, T-2513, and its metabolites, SN-38, SN-38G, T-1335, T-0055, and T-3921, were assessed in plasma and urine, and their pharmacodynamics were determined by measuring the effect of the treatment on hematologic and nonhematologic toxicity.

Results: Twenty-two patients received 35 courses. Dose-limiting toxicities were observed at 5,400 mg/m(2) (n = 1), 3,600 mg/m(2) (n = 1), and 2,400 mg/m(2) (n = 2). The dose level of 1,800 mg/m(2) was determined as maximum tolerated dose. Two partial responses were observed in patients with anal cancer (1800 mg/m(2)) and head and neck cancer (2400 mg/m(2)). Delimotecan had a long terminal half-life of 109 h, and relatively high exposures to T-2513 and SN-38 were obtained. The percentage decrease in WBC and absolute neutrophil count significantly correlated with the dose of delimotecan.

Conclusions: Based on its preliminary antitumor activity, safety profile, and pharmacokinetic profile, we recommend to evaluate delimotecan given as 3-hour infusion once every 6 weeks at a dose level of 1,800 mg/m(2) in a phase II study.