Geron's cancer drug shakes off one FDA hold but remains on pause

The FDA has loosened its grip on imetelstat, Geron's ($GERN) in-development blood cancer treatment, lifting a partial clinical hold on a Mayo Clinic-sponsored study of the drug. However, a separate agency hold on the company's own Phase II trials remains in effect, tying Geron's hands with its one and only candidate.

Despite the ongoing delay, however, the latest news sent Geron's long-battered shares up more than 35% in premarket trading Thursday, reflecting investor optimism that the FDA will circle back and release its other clinical hold.

The agency first stepped in on the Mayo trial in March, hitting pause on the study until investigators could demonstrate that an imetelstat-caused spike in liver toxicity among myelofibrosis patients was reversible. The FDA cited similar concerns over long-term liver damage in its full clinical hold on Geron's mid-stage programs, which were charting the drug's effects on multiple myeloma and thrombocythemia.

That stoppage is still in effect, leaving Geron unable to submit new protocols or start further trials for imetelstat and delaying a planned Phase II myelofibrosis study of the company's own. Geron said in its announcement that it's "working diligently to seek release of the full clinical hold."

Imetelstat has led Geron--and its investors--on a volatile trail over the past year. In December, an early peek at data from the Mayo trial revealed that the drug triggered complete remission in some myelofibrosis patients and charted an overall response rate of 41%, sending the company's shares skyward. Months later, when the FDA stepped in with its first clinical hold, Geron tanked more than 60% in a single day.

After more than 20 years in drug development, Geron has never quite found its way to the finish line, and imetelstat was meant to be the star of the biotech's latest makeover. The company backed away from its ambitions in stem cells in 2011 and rebranded itself as a cancer-focused outfit, but repeated failures in breast cancer and lung cancers led Geron to pare down imetelstat's hoped-for indications, and a Phase II failure for the brain cancer-treating GRN1005 reduced Geron's pipeline to a single candidate.

- read the announcement