Custirsen Fails to Improve Prostate Cancer in Phase 3 Trial

Company slumps under bad news

OncoGenex Pharmaceuticals has announced results from the final analysis of its phase 3 AFFINITY study of custirsen in men with metastatic castrate-resistant prostate cancer (CRPC) whose disease has progressed after treatment with docetaxel. The international, randomized, open-label trial did not meet its primary endpoint of demonstrating a statistically significant improvement in overall survival for patients treated with custirsen in combination with cabazitaxel/prednisone compared with cabazitaxel/prednisone alone.

Patients received cabazitaxel/prednisone plus weekly custirsen or cabazitaxel/prednisone alone, and treatment continued until disease progression, unacceptable toxicity, or the completion of 10 cycles. The trial enrolled a total of 634 men with metastatic CRPC in North America, Europe, Russia, and Australia.

As a result of the disappointing data and previous custirsen findings, OncoGenex plans to initiate discussions with the FDA to evaluate options related to an early analysis of the phase 3 ENSPIRIT trial, which investigated custirsen in combination with docetaxel as second-line chemotherapy in patients with non–small-cell lung cancer (NSCLC).

Custirsen is a highly specific clusterin inhibitor designed to improve survival in patients with advanced cancer by disabling a fundamental cellular repair mechanism used by tumor cells. Custirsen binds to clusterin mRNA to block the production of clusterin protein and has enhanced the tumor-cell destructive effects of anticancer therapies in tumor models, according to OncoGenix. By inhibiting clusterin, custirsen is designed to alter tumor dynamics by slowing tumor growth and by inhibiting tumor resistance to partner treatments, so that the benefits of therapy, including survival, may be extended.

According to a Reuters report, the AFFINITY results add to several disappointments that OncoGenex has experienced recently. In January, the company said interim data showed that its experimental cancer drug apatorsen did not reach the statistical significance required for progression-free survival in a midstage study in certain lung cancer patients.

The company has lost about 69% of its value since September and is currently trading at 58 cents per share, Reuters said.

Sources: OncoGenix Pharmaceuticals; August 16, 2016; and Reuters; August 16, 2016.