San Francisco-based drugmaker Exelixis is halting research into the use of its thyroid cancer therapy Cometriq for treating prostate cancer after the drug failed a Phase III trial for that indication.

Median overall survival rates were not statistically significant in men taking the drug for metastatic treatment-resistant prostate cancer, only 1.2 months longer than patients given prednisone, a generic drug that treats inflammation and some types of cancer, the company said Tuesday. Cometriq (cabozantinib) did slightly better with progression-free survival, extending the time to disease progression by 2.7 months longer than prednisone.

Progression-free survival, however, is not an endpoint that has resulted in approval for other prostate-cancer drugs, Chief Medical Officer Gisela Schwab told a Tuesday teleconference to discuss the results.

As a result of the study outcomes, the company said it will reduce its workforce by 160 people, leaving roughly 70 employees remaining.

Exelixis is still sorting through secondary and exploratory endpoint data from the trial, Schwab said. Enrollment in another Phase III trial evaluating cabozantinib for pain palliation also was halted. Results from this trial, which are expected later this year, will decide whether the company will continue to explore the drug for treating prostate cancer, she added.

Meanwhile, the company continues to study the drug for metastatic kidney cancer and advanced liver cancer indications. A Phase Ib kidney cancer trial showed that the tumor shrank in 19 out of 21 patients, while a Phase II liver cancer trial had 4.4 months of progression-free survival and 15.1 months of overall survival.

Cometriq won FDA approval in 2012 for progressive, metastatic medullary thyroid cancer, and European approval for progressive, unresectable locally advanced or metastatic MTC. — Lena Freund

Originally appeared in Drug Industry Daily, the pharmaceutical industry’s number one source for regulatory news and information. Click here for more information.