What happened

After reporting that it has received a refuse-to-file letter from the FDA regarding its Parkinson's disease drug, Inbrija, shares in Acorda Therapeutics (NASDAQ:ACOR) are crashing 25% at 12:30 p.m. EDT Tuesday.

So what

Acorda Therapeutics reported positive phase 3 trial results for Inbrija in February, and optimism that it could win FDA approval in time to offset the risk of generic competition to the company's multiple sclerosis drug, Ampyra, has helped prop up the company's share price.

A rubber stamp on a white background that reads, "Rejected."

Image source: Getty Images.

Unfortunately, hope for a speedy review of Inbrija was dashed Tuesday by news that the FDA isn't accepting Inbrija's application for approval, which Acorda Therapeutics filed with the regulator in late June.

The FDA cited two reasons for its decision. First, an objection to "the date when the manufacturing site would be ready for inspection," and second, "a question regarding the submission of the drug master production record," which details the uniformity of manufactured drugs.

Acorda Therapeutics also said the FDA wants "additional information at resubmission." That wasn't a reason for the refuse-to-file letter, however, management didn't explain in its press release what information the FDA is requesting.

Now what

In trials, Inbrija improved patient motor function during "off" times, and therefore it could eventually be an important drug for patients. But now, it's anyone's guess when -- or if -- this drug will pass muster with regulators.

Management thinks it can address the FDA's concerns, and the FDA isn't asking for any additional trials. However, there's no timeline for a resubmission of Inbrija's application, and that's a problem, because earlier this year, four patents protecting Amprya were invalidated. The patent decision could lead to generic versions of Amprya launching next year, and given Amprya accounts for $131.6 million of Acorda Therapeutics $141.1 million in second-quarter sales, a delay in launching Inbrija increases the risk to the company's top line.

Until we find out more from management about the refuse to file letter, and how quickly it can resubmit an application for approval, it's probably best to focus on other companies with fewer question marks.

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