UC Davis

Purpose

This phase I study examined the toxicity and tolerability of pegylated arginine deiminase (ADI-PEG 20) in combination with docetaxel in patients with advanced solid malignancies.

Experimental design

Eligible patients had histologically proven advanced solid malignancies, with any number of prior therapies, Zubrod performance status 0-2, and adequate organ function. Patients received ADI-PEG 20 weekly intramuscular injection ranging from 4.5 to 36 mg/m(2) and up to 10 doses of docetaxel (75 mg/m(2)) every 3 weeks. Primary endpoints were safety, toxicity, and a recommended phase II dose. Circulating arginine levels were measured before each cycle. Tumor response was measured as a secondary endpoint every 6 weeks on study.

Results

Eighteen patients received a total of 116 cycles of therapy through four dose levels of ADI-PEG 20. A single dose-limiting toxicity (grade 3 urticarial rash) was observed at the 1st dose level, with no additional dose-limiting toxicities observed. Hematologic toxicities were common with 14 patients experiencing at least one grade 3 to 4 leukopenia. Fatigue was the most prevalent toxicity reported by 16 patients. Arginine was variably suppressed with 10 patients achieving at least a 50% reduction in baseline values. In 14 patients with evaluable disease, four partial responses (including 2 patients with PSA response) were documented, and 7 patients had stable disease.

Conclusions

ADI-PEG 20 demonstrated reasonable toxicity in combination with docetaxel. Promising clinical activity was noted, and expansion cohorts are now accruing for both castrate-resistant prostate cancer and non-small cell lung cancer at a recommended phase II dose of 36 mg/m(2).