Investors’ excitement about a promising new drug for depression reached a fever pitch last week when the CEO of the company behind it likened the drug to an antibiotic.

This drug has the “potential for patients with major depressive disorder to feel well within days, with just a two week course of treatment — similar to how antibiotics are used today — instead of enduring long-term chronic treatment,” Sage Therapeutics’ CEO Jeff Jonas said on Tuesday of his company’s drug, SAGE-217.

The comments came shortly after the company said it had received the green light from the Food and Drug Administration to accelerate the approval process for its drug.

A once-only course of treatment is essentially unheard of for depression or for any other chronic disease. And experts within and outside of the company say they doubt that’s how SAGE-217 would actually work. Instead of working as a once-only treatment, they said that data on the drug suggest that its effects would likely last as long as one month. Patients would still need to take the drug regularly for long-lasting results.

More importantly, although the drug has shown a promising potential ability to treat depression in preliminary studies, those findings have yet to be borne out by the kinds of longer and larger trials that are needed before it gets anywhere near federal approval.

An area in desperate need of new treatments

Depression is the leading cause of disability worldwide, and it can kill. While not the sole cause of suicide, depression is often a contributing factor. And while suicide rates have climbed for nearly 20 years, not a single new drug for depression has emerged.

Most treatments for depression and suicidal thinking are limited to a narrow class of drugs known as selective serotonin reuptake inhibitors, or SSRIs, which includes popular drugs like Prozac and Lexapro. While they can help some people, failure rates hover around 50%.

So researchers are on the hunt for better options — options that could soon include Sage’s new compound, which preliminary studies have suggested works well to treat depressive symptoms within a short time period.