What happened

Shares of clinical stage biopharma Geron Corporation (NASDAQ:GERN) fell nearly 17% Tuesday after management provided a clinical update on its only drug candidate, imetelstat, which is being investigated for treating myelofibrosis (MF) and myelodysplastic syndromes (MDS).

Development partner Janssen Oncology, which is a subsidiary of Johnson & Johnson, has decided to alter the ongoing IMerge phase 2/3 trial investigating MDS. Janssen Oncology also hasn't decided whether or not to commit to imetelstat for the IMbark phase 2 trial in MF.

As of 12:06 p.m. EDT, the stock had settled to a 12.3% loss.

A man with his face down on a desk and a graph on the wall behind him showing a decline.

Image source: Getty Images.

So what

The news has put investors on edge because they're worried that Geron Corporation and Janssen don't share the same level of confidence in the drug candidate. For instance, the changes to the IMerge trial will "enroll additional patients in a refined MDS population to confirm the clinical benefit and safety observed from current results."

That's a funny way to say that the patient population being treated with imetelstat is being narrowed. While that could be homing in on more specific patients that are more likely to benefit, failing to "confirm the clinical benefit and safety observed" thus far could mean the end of the study. Given that imetelstat is the company's only drug candidate, such an outcome could be an existential threat to Geron Corporation.

Now what

When the oddly worded language about changes to IMerge is combined with the fact that Janssen is dragging its feet on deciding whether or not to push ahead with the IMbark trial, it's easy to see why Mr. Market is losing faith in Geron Corporation stock on Tuesday. It's still too early to get carried away with interpretations, but the company hasn't exactly accomplished anything of note in its nearly 30-year history.

Maxx Chatsko has no position in any stocks mentioned. The Motley Fool owns shares of and recommends Johnson & Johnson. The Motley Fool has a disclosure policy.