Sage shares cut in half after postpartum drug approval. Here’s what happened.

The Cambridge drugmaker saw its market value drop by about $1 billion in the first minutes of trading Monday, following a partial approval of a new depression drug late Friday. Cambridge-based Sage had applied to market the depression drug, zuranolone, as a treatment for both major depressive disorder (MDD) and postpartum depression (PPD). The U.S. Food and Drug Administration approved zuranolone, now marketed under the name Zurzuvae, for PPD but rejected it as a treatment for MDD, citing a lack of substantive data. The latter disorder would have presented a much larger market opportunity, analysts have noted. "We are devastated for patients and deeply disappointed with the FDA’s position in issuing the [rejection]," Sage CEO Barry Greene said on a conference call Monday morning.