What happened

Shares of Biohaven Ltd. (BHVN -3.46%) were crashing 27.5% lower at 11:50 a.m. ET on Thursday. This big sell-off came after the company provided updates on several programs.

The most important news for investors is related to Biohaven's New Drug Application (NDA) filing for troriluzole in treating spinocerebellar ataxia type 3 (SCA3), an ultrarare neurodegenerative disorder. The U.S. Food and Drug Administration (FDA) told the company that it won't review the NDA because the primary endpoint wasn't met in the study that formed the basis for the submission. 

This update overshadowed more encouraging developments for Biohaven on other fronts. The company announced positive interim electroencephalogram (EEG) data from a phase 1 study of the experimental drug BHV-7000. It also reported progress in an ongoing phase 1 study of BHV-8000.

So what

Biohaven had hoped that it would pick up its first FDA approval with troriluzole in the SCA3 indication. CEO Vlad Coric said that he was "deeply disappointed" by the agency's decision.

It's not the end of the road for troriluzole, though. Biohaven will regroup and take another shot at securing FDA approval for the experimental drug in treating SCA3. The company is also evaluating troriluzole in treating obsessive-compulsive disorder (OCD).

Now what

Biohaven's next step is to meet with the FDA to determine how to address the agency's concerns with its NDA. The company said in a press release, "We stand by these data and analyses."

It remains to be seen if it will be able to sway the FDA or if it will have to provide additional data and possibly even conduct another clinical trial. The biotech stock probably won't rebound much until the uncertainty is resolved.