Shares of the brain-health specialist Sage Therapeutics (NASDAQ: SAGE) are having a tough trading session today. Specifically, the biotech's stock was down by approximately 13% on heavy volume as of 2:38 p.m. ET Wednesday afternoon. 

The spark? Yesterday, (NASDAQ: BIIB) Chief Executive Officer Christopher Viehbacher barely mentioned the upcoming regulatory decision for zuranolone as a treatment for major depressive disorder (MDD) and postpartum depression (PPD). Biogen and Sage co-developed zuranolone as a fast-acting option for patients with these debilitating forms of depression. The Food and Drug Administration (FDA) is slated to hand down a regulatory decision in these two settings by Aug. 5. 

Investors took Viehbacher's silence as a troubling sign that all is not well with zuranolone's regulatory review. Normally, labeling discussions are taking place at this late stage in a drug review. However, Biogen's leader didn't mention anything on the topic, leading some nervous investors to speculate that a regulatory delay, or an outright rejection, was on the way.

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Source Fool.com