It has been a long and difficult road for Alkermes’ new depression drug, and Thursday’s advisory committee vote won’t make it any easier. The panel voted 21-2 against recommending the drug for approval, teeing it up for a likely rejection come January.

Alkermes is seeking the FDA nod for the drug, ALKS-5461, as a treatment for major depressive disorder, the most common form of depression. The panel included both the Psychopharmacologic Drugs Advisory Committee and the Drug Safety and Risk Management Committee because ALKS-5461 contains an opioid: buprenorphine.

The panel also voted 20-3 that Alkermes did not provide “substantial evidence” to support the efficacy of ALKS-5461, a combination of buprenorphine and samidorphan, a new molecular entity designed to ward off buprenorphine’s negative effects, such as addiction. The only positive vote was the safety one, and even then, ALKS-5461 barely squeaked through—the panel voted 13-10 that Alkermes had “adequately characterized the safety profile of buprenorphine/samidorphan for the adjunctive treatment of major depressive disorder.”

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ALKS-5461 works differently from currently available depression drugs, offering hope in a field that has lacked investment and innovation. If approved, it could become an option for people who don’t respond to traditional antidepressants.

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Felipe Jain, M.D., an assistant clinical professor of psychology at the University of California, San Francisco, voted no “as somebody who prescribes opiates to patients with treatment-resistant depression.”

“I did not feel the evidence was convincing of substantial effectiveness,” he said.

There were “too many methodological issues,” said another panelist, Satish Iyengar, Ph.D., a professor of statistics at the University of Pittsburgh.

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While the FDA is not obligated to heed an advisory committee’s advice, it tends to stick to the recommendation. The agency is expected to make a decision on ALKS-5461 by Jan. 31.

“A combination of poor choice in statistical methods and an unsupported change in clinical endpoints drove the vote. The outcome leads to a high likelihood of issuance of a CRL. We currently still model $250M in peak sales, and we await FDA clarity on requirements for '5461 and whether the ongoing PIIIb would be sufficient,” Jefferies analysts wrote in a note Thursday evening.