Millions of Americans who experience debilitating bouts of depression could have a new treatment option this summer. On Monday, the FDA began reviewing a New Drug Application from Axsome Therapeutics (AXSM -5.72%) for its lead candidate, AXS-05.

Instead of the standard review that takes 10 months, the FDA gave AXS-05 a Priority Review that shaves four months off the process. The agency expects to issue a decision on or before Aug. 22.

Smiling doctor

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Both active ingredients in AXS-05, bupropion and dextromethorphan, are well-understood drugs that complement each other. In the pivotal Gemini study, patients treated with AXS-05 were more than twice as likely to achieve remission than the placebo group. Strong data, decades of experience with the active ingredients, and a lack of safety issues with AXS-05 so far make its approval seem like a foregone conclusion.

An estimated 7.8% of American adults experience major depressive disorder each year, and many of them could use a novel new drug. Popular serotonin reuptake inhibitors (SRIs) like Celexa and Zoloft get the job done for some, but roughly a third don't respond well to their first two attempts at treatment. 

Bupropion isn't free from side effects, but it's a walk in the park compared to the average SRI, and it's already prescribed around 24 million times a year for depression and smoking cessation. Pharmacies in the U.S. fill out about 88 million prescriptions for the three most popular SRIs each year. This means approval for AXS-05 this summer could be its first step on the way to becoming one of the country's most prescribed drugs.