Phase I and pharmacokinetic study of the dolastatin-15 analogue tasidotin (ILX651) administered intravenously on days 1, 3, and 5 every 3 weeks in patients with advanced solid tumors

PURPOSE

To determine the maximum tolerated dose (MTD), dose-limiting toxicity (DLT), and pharmacokinetics of tasidotin (ILX651), a dolastatin-15 analogue, when administered on days 1, 3, and 5 every 3 weeks in patients with advanced solid tumors.

PATIENTS AND METHODS

Thirty-two patients were treated with 92 courses of tasidotin through seven dose levels determined by a modified Fibonacci scheme ranging from 3.9 to 45.7 mg/m(2). Pharmacokinetic samples were collected during the first course.

RESULTS

Neutropenia was the principal DLT at the 45.7 mg/m(2)/d dose level. In addition, one patient also experienced grade 3 neutropenia complicated with grade 3 esophageal candidiasis and grade 3 dehydration. Only 1 of 11 patients treated at the MTD, 34.4 mg/m(2), experienced dose-limiting neutropenia. Other common, drug-related toxicities included mild to moderate fatigue, anemia, nausea, anorexia, emesis, alopecia, and diarrhea. The best observed antitumor response consisted of stable disease and was noted in 10 patients (31%); the median duration on study for those patients with stable disease was 99.5 days compared with 37.5 days for those patients with progressive disease. Tasidotin plasma concentrations declined biphasically with an effective half-life of < or =55 minutes, and approximately 11% was excreted unchanged in the urine.

CONCLUSION

The recommended dose for phase II studies and the MTD when tasidotin is administered on days 1, 3, and 5 every 3 weeks is 34.4 mg/m(2). The favorable toxicity profile of tasidotin compared with other antitubulin agents, including other dolastatin analogues, and its novel mechanism of action support further disease-directed evaluation of this agent.

A Phase I Study of the Dolastatin-15 Analogue Tasidotin (ILX651) Administered Intravenously Daily for 5 Consecutive Days Every 3 Weeks in Patients with Advanced Solid Tumors

PURPOSE

To determine the maximum tolerated dose, dose-limiting toxicity, and pharmacokinetics of the dolastatin-15 analogue, tasidotin (ILX651), when administered i.v. daily for 5 days every 3 weeks.

EXPERIMENTAL DESIGN

Thirty-six patients with advanced solid tumors received a total of 114 courses through eight dose levels ranging from 2.3 to 36.3 mg/m(2). Pharmacokinetic samples were collected in cycle 1.

RESULTS

Neutropenia was the principal dose-limiting toxicity at 36.3 mg/m(2)/d along with grade 3 ileus and elevated aspartate amino transaminase/alanine amino transaminase (n = 1). At the maximum tolerated dose, 27.3 mg/m(2), 4 of 14 patients experienced dose-limiting grade 4 neutropenia. The other principal toxicities consisted of mild-to-moderate elevated transaminases, alopecia, fatigue, and nausea. One patient with melanoma metastatic to liver and bone treated at 15.4 mg/m(2)/d experienced a complete response and received 20 courses of tasidotin. Two other patients with melanoma had mixed responses of cutaneous metastases at 27.3 mg/m(2)/d associated with either stable or progressive visceral disease. In addition, nine patients had stable disease. There was no accumulation of tasidotin following repeated daily dosing. Tasidotin decayed from plasma in a biphasic fashion with a half-life of <45 minutes in most cases.

CONCLUSION

The maximum tolerated dose and recommended phase II dose for tasidotin when administered on this schedule was 27.3 mg/m(2)/d. The favorable toxicity profile of tasidotin compared with other antitubulin agents (particularly the lack of severe cumulative neuropathy, peripheral edema, and fatigue), the observed antitumor activity of tasidotin, and its novel mechanism of action support further disease-directed evaluations of this agent on this 5-day schedule every 3 weeks.