After zooming up on positive data for its telomerase inhibitor imetelstat in myelofibrosis and multiple myeloma, Geron (NASDAQ:GERN) came crashing back to earth this month when the biotech announced that the FDA was putting its clinical trial on hold due to persistent low-grade liver function test.

Clinical holds can be lifted, but as Fool contributor Brian Orelli and health-care bureau chief Max Macaluso discuss in the vide below, it's really hard for investors to determine if Geron will be able to convince the FDA to let the drug back into the clinic.

Prime example: Idenix Pharmaceuticals (UNKNOWN:IDIX.DL), which had its hepatitis C drugs put on clinical hold because it had a similar structure to Bristol-Myers Squibb's (NYSE:BMY) BMS-986094, which had serious cardiac side effects. Despite a lack of side effects for its drug, Idenix was never able to convince the FDA to restart its program, and eventually dropped development.