What happened

Shares of Unity Biotechnology (UBX -1.32%) fell over 63% today after the company announced disappointing results from a clinical trial involving its lead drug candidate, UBX0101. 

At the 12-week mark of a phase 2 study, the pipeline asset failed to meet its primary endpoint in alleviating moderate to severe painful osteoarthritis (OA) of the knee. In fact, there were no statistically significant differences between any dose of UBX0101 and placebo.

As of 1:22 p.m. EDT, the small-cap stock had settled to a 61.3% loss.

A shocked woman checking her phone.

Image source: Getty Images.

So what

Unity Biotechnology is developing a drug pipeline based on the idea that clearing senescent cells, or cells that stop dividing, can help to treat or reverse age-related diseases. The idea has been around for decades and has begun to gain traction in recent years with new developments in living technologies.

Of course, many cellular mechanisms and biomolecules often have multiple roles in the body. Proteins that trigger processes to reduce inflammation in some settings can trigger processes that increase inflammation in other settings. Similarly, senescent cells aren't always a sign of age-related diseases. They play important roles from the development of embryos to the health of centenarians. 

It's possible that a mechanism to finely control senescent cell populations related to age-related diseases -- while sparing health-related cell populations -- will be discovered and commercialized, but there are simply too many unknowns for investors to confidently bet on any pipeline or technology. 

Now what

Unity Biotechnology reported it will complete data collection through the 24-week mark of the phase 2 trial, although it doesn't intend to advance UBX0101 in phase 3 trials. Its next-most advanced pipeline asset is UBX1325, which has yet to enter clinical trials. Given the lack of data to support the pipeline, Unity's $250 million market valuation seems about right, if not generous.