What: After announcing yesterday afternoon a key mid stage clinical trial failure, shares in Flexion Therapeutics, (FLXN) tumbled by 28% earlier today.

So what: Flexion Therapeutics' lead product candidate, FX006, was being studied to reduce pain in patients with moderate-to-severe osteoarthritis of the knee.

Unfortunately, results from a phase 2b study evaluating FX006 in 310 of these patients failed to show that it provides better pain relief than a placebo at 12 weeks of treatment.

Now what: Flexion Therapeutics may be able to salvage FX006, however, because a sensitivity analysis taking into consideration people who dropped out of the trial resulted in a positive finding.

Additionally, positive efficacy was noted at several other time periods throughout the trial, including for average pain relief over weeks one through 12. Also, Flexion Therapeutics analysis shows that a higher 40 mg dose of FX006 works better than a lower 20 mg dose, which leaves the door open for developing the higher dose and abandoning the lower dose in the future.

Because Flexion Therapeutics' additional analysis suggests that FX006 works in some patients, investors might want to wait for results from an ongoing phase 3 trial of the drug before buying or selling Flexion Therapeutics shares. Results from that trial are expected early next year, so stay tuned.