Phase I study of NKT-01

A phase I study of NKT-01 (deoxyspergualin), which is a derivative of an antitumor antibiotic, spergualin, was performed by a cooperative study group. NKT-01 was given intravenously by 3-h infusion. The effect of single administration was studied prior to evaluation of daily administration for 5 consecutive days. In all, 5 and 33 patients with various malignancies, including leukemia, were entered into the trials of single and daily administration, respectively. In the single-administration study, all patients were evaluable and no clear adverse effect was observed at doses ranging from 20 to 320 mg/m². In the daily-administration study, 28 evaluable patients (16 men and 12 women; median age, 55.5 years) were treated with a daily dose of 20–500 mg/m². Toxicities such as myelosuppression, mild nausea/vomiting, anorexia, alopecia, tongue and perioral numbness, and hypotension were observed dose-dependently during or after the treatment. Grade 2 leukopenia, thrombocytopenia, and anemia were experienced at a dose of 500 mg/m². These usually recovered to normal values by approximately 3 weeks after treatment. A pharmacokinetic analysis of single administration revealed rapid plasma clearance, with mean half-lives for the and phases being 28 min and 6.9 h, respectively. Approximately 12% of the infused dose was excreted into the urine in unmetabolized form. The pharmacokinetic parameters obtained after 5-day administration were similar to those recorded after single administration. Concerning treatment response, a transient but significant reduction in the number of leukemic cells was observed in one patient with adult T-cell leukemia. In this study, perioral numbness, hypotension, and hematological toxicity were concluded to be dose-limiting, with the maximal acceptable dose being 500 mg/m². The recommended dose for a phase II study of NKT-01 against solid tumors was judged to be 400 mg/m² given daily by 3-h infusion for 5 days, every 3 weeks. In hematological malignancies, however, higher myelosuppressive schedules of administration should be investigated.