Paclitaxel (Taxol) is formulated in 50% Cremophor EL (CrEL)/absolute ethanol for clinical use. In order to reduce vehicle-related side effects, Genetaxyl was developed to have paclitaxel formulated in a solution containing lesser amounts of CrEL and ethanol plus 2 other solvents. The purpose of the study was to evaluate the efficacy and safety of Genetaxyl as first-line therapy to treat breast cancer patients. Patients with newly diagnosed stage III (N = 8) or IV (N = 10), or recurrent (N = 11) breast cancer received single-agent Genetaxyl at 175 mg/m(2) administered in a 3-h infusion every 3 weeks for 3-6 cycles. A total of 148 cycles were delivered to 29 patients. The overall response rate was 41.4% (95% confidence interval, 23.4 to 59.2%), and that of patients with metastatic disease (N = 20) was 30%. Median survival for all patients was 32.4 months and 24.3 months for patients having metastatic disease. The toxicity profile seems favorable, especially regarding myelosuppression and myalgia/arthralgia. No severe hypersensitivity reaction occurred. These phase II trial results demonstrate that a 60% reduction of CrEL by Genetaxyl's formulation does not affect the activity of paclitaxel and could allow for better control of several CrEL-related toxicities.