The results demonstrated a major response rate of 24% with a median overall survival at follow up of 8.5 months and a median time to progression of 3.5 months. Of the 24 patients on the study, 80% had received prior chemotherapy and 84% of those patients were resistant or refractory to prior taxane chemotherapy.
“The activity of Xyotax in this setting is encouraging given that two-thirds of the patients had failed prior docetaxel therapy, suggesting that Xyotax may offer an alternative to such patients. Importantly, Xyotax was administered in a short, ten to twenty minute, infusion without routine pre-medications. On a monthly dosing regimen, the only grade 4 toxicity was uncomplicated neutropenia,” noted Robert Amato, director, Genitourinary Oncology Program at The Methodist Hospital Research Institute in Houston.
“The next phase of the study will explore the ability of estrogen supplementation to further increase the major response rate in this difficult to treat population of patients with prostate cancer.”
The study continues to enroll and follow patients and the protocol has been amended to include the use of estrogel with Xyotax to determine safety and if efficacy is enhanced.
Preclinical data show that in estradiol supplemented female mice Xyotax demonstrated a nearly two-fold increase in anti-tumor activity compared to non-supplemented animals in a colon cancer tumor model.