Sage Therapeutics Inc. slumped in early trading after regulators granted approval to its fast-acting pill only for postpartum depression, denying the drug clearance for major depressive disorder.

The Food and Drug Administration approved the drug, Zurzuvae, late Friday with a boxed warning that it may affect patients’ ability to drive or operate heavy machinery, and they should avoid doing so for 12 hours after taking it. The agency also told Sage that it lacked the data to show it works in MDD, and more research will be needed.

Sage declined as much as 53% before US markets opened Monday, putting it on pace to sink to its lowest level on record. Partner Biogen Inc. slipped 3.3%

About one in eight new mothers experiences postpartum depression, according to the US Centers for Disease Control and Prevention. Major depressive disorder also represents a large population, with an estimated 21 million adults in the US experiencing at least one episode in 2020, according to the National Institutes of Health.

Taken for only two weeks, Zurzuvae is unlike other depression treatments that generally start working over longer periods. Still, it has faced questions about whether the improvement lasts once people stop taking it. That could limit interest from doctors and insurers, especially with cheap generic drugs so embedded into the current treatment.

Biogen and Sage will also need to raise awareness of postpartum depression. Although it’s common, one study found only about half of women with the condition are diagnosed and only about 10% are adequately treated. Sage sells an infused drug similar to Zurzuvae that’s struggled to gain traction.

Doctors hailed the approval of the fast-acting pill for mothers with depression. Women will be more interested in taking a pill every day for two weeks rather than sitting through a nearly three-day infusion, said Kristina Deligiannidis, a principal investigator on Zurzuvae’s postpartum depression clinical trials.

“This is really going to change the way we treat postpartum depression,” said Deligiannidis, director of women’s behavioral health at Northwell Health’s Zucker Hillside Hospital.

Before Biogen and Sage can start selling Zurzuvae, they’ll need clearance from the Drug Enforcement Administration, which categorizes certain drugs based on their potential for abuse. The companies anticipate that will happen about three months after approval.

This story was produced with the assistance of Bloomberg Automation.

--With assistance from Shiyin Chen.