OncoGenex’s Long Wait For Cancer Drug Ends With a Phase 3 Stumble

4/28/14Follow @benthefidler

OncoGenex has waited for years for the outcome of a Phase 3 trial that would tell it whether it had a real treatment for prostate cancer patients on its hands—all while watching increasingly effective drugs seep into the marketplace. The news finally came down today, and unfortunately for the Bothell, WA- and Vancouver, BC-based company, it wasn’t good.

OncoGenex (NASDAQ: OGXI) said today that its lead experimental prostate cancer drug, custirsen, failed to meet its main goal of helping patients live longer in a late-stage clinical trial. Specifically, prostate cancer patients taking OncoGenex’s drug along with chemo drug docetaxel and prednisone fared only slightly better than the placebo group—they had a median survival rate of 23.4 months, compared to 22.2 months for patients dosed with a placebo—and the results weren’t close to being statistically significant. OncoGenex’s shares plummeted more than 50 percent in pre-market trading on Monday. The company is partnering with Teva Pharmaceutical Industries (NYSE: TEVA) on custirsen.

Still, OncoGenex hasn’t given up on custirsen. The company has a second late-stage trials of the drug ongoing called Affinity, and still believes in the mechanism of the drug, which, unlike other prostate cancer drugs, is genetically engineered to block RNA that creates the protein clusterin. That protein is thought to serve as a defense mechanism tumors use to resist chemotherapy, so OncoGenex has been trying to show that disabling it with a drug could make chemotherapy like docetaxel more effective.

“The results…are unexpected, particularly given the wealth of scientific evidence supporting the targeting of clusterin to combat treatment resistance in first-line prostate cancer,” OncoGenex president and CEO Scott Cormack said in a statement. “A thorough analysis of the data is underway to understand the potential factors that may have contributed to the results.”

Even so, it’s a big setback for OncoGenex. The company charged into a massive Phase 3 program after a study of 82 men with prostate cancer showed that custirsen, in combination with docetaxel, helped patients live a median of 6.9 months longer than those on chemo alone and even appeared to reduce patients’ bone pain—often a significant problem for men with terminal prostate cancer as tumors spread to their bones. But as OncoGenex was waiting for these studies to read out, the field for prostate cancer drugs became much more competitive. Johnson & Johnson was cleared to begin selling abiraterone (Zytiga). San Francisco-based Medivation (NASDAQ: MDVN) and partner Astellas Pharma won FDA approval of enzalutamide (Xtandi).

Worse for OncoGenex, both Medivation/Astellas and Johnson & Johnson’s drugs have proven to show a tangible benefit for patients who haven’t yet progressed to needing chemotherapy. OncoGenex has been hoping its drug could find a niche among patients at the next step, those who have started chemotherapy. But as treatment options for prostate cancer change, it’s unclear just how big a market would be available for OncoGenex if it even produced good results.

That’s not a question OncoGenex is likely worrying about today, however.

Ben Fidler is Xconomy's Deputy Biotechnology Editor. You can e-mail him at bfidler@xconomy.com Follow @benthefidler

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