Exelixis, Inc. (NASDAQ:EXEL) today reported updated interim data from the fully enrolled cohort of patients with metastatic castration-resistant prostate cancer (CRPC) treated with cabozantinib (XL184) in a phase 2 adaptive randomized discontinuation trial (RDT). The data provide additional patient experience and longer-term follow-up showing that cabozantinib results in resolution or stabilization of metastatic bone lesions on bone scan in the majority of patients evaluable by this method. Additionally, cabozantinib treatment relieved or eliminated bone pain in the majority of patients, thus allowing for most who require narcotic analgesic medication to either reduce or eliminate the use of these medicines. Patients with partial or complete resolution of metastatic bone lesions by bone scan were more likely to remain free of disease progression at month 6, experience pain relief, reduce or eliminate their use of narcotic analgesics, achieve tumor regression, and experience marked declines in markers of bone turnover when compared to those who did not achieve bone scan resolution.
“Today's presentation encompasses the largest data set for cabozantinib in CRPC released to date, and the results continue to support cabozantinib as a novel and unique approach to addressing the unmet medical needs of patients with this disease”
Updated progression-free survival (PFS) data show that cabozantinib results in median PFS that appears to be similar in docetaxel-naïve and pretreated patients, and compares favorably to population matched historical controls. In the randomized discontinuation phase of this study, significant improvement in median PFS was observed in patients randomized to cabozantinib. Despite only 31 patients randomized at week 12, the results were highly statistically significant, suggestive of a sizable treatment effect over placebo. Durable increases in hemoglobin levels in anemic patients were also observed.
Maha Hussain, M.D., Associate Director for Clinical Research at the University of Michigan Comprehensive Cancer Center, presented the data today in an oral session at the American Society of Clinical Oncology's 2011 Annual Meeting (Abstract #4516) in Chicago.
As of the February 11, 2011 cut-off date, accrual in this cohort was complete at 171 patients. Randomization was halted, and randomized patients were un-blinded based on an observed high rate of clinical activity. Unlike most clinical trials in CRPC, which is a bone-predominant malignancy, all 171 patients enrolled in this trial had measurable soft tissue disease per mRECIST, of which 37% had evidence of disease in liver or lung. The bone scan evaluable population includes 108 patients with evidence of bone metastasis, a baseline bone scan, and at least 1 post-baseline bone scan assessment. Prior therapies included docetaxel (43%), abiraterone/MDV3100 (9%), and other cytotoxic and/or experimental agents (22%).
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