What happened

Aquestive Therapeutics (AQST 14.80%) was one of the steeper decliners among biotech stocks Tuesday. The company's shares plummeted more than 29% on a rather discouraging piece of news about one of its top drug candidates.

So what

Late Monday night, Aquestive disclosed that it had received notification from the Food and Drug Administration (FDA) regarding its Libervant Buccal Film pipeline drug. The regulator told the company that it is delaying the review of Aquestive's New Drug Application (NDA) for Libervant. This is a treatment targeting breakthrough seizures and seizure clusters suffered by those afflicted by epilepsy.

A medical professional using a microscope.

Image source: Getty Images.

After the regulator accepted the company's NDA in July, a target goal date was set for this coming Thursday, Dec. 23. The FDA wrote that it "is still considering the regulatory issues related to the approvability of Libervant, and will not be ready to take an action, by that date."

The FDA did not provide more detail about the issues it is contemplating, while adding that at present it cannot give an estimate for a new date. 

In a statement disclosing the news, Aquestive CEO Keith Kendall said: "We are surprised to receive this notification from the FDA. We accepted all of the agency's label edits for Libervant last week and, as the agency stated in its notice today, there is no additional information needed from the company at this time."

He added that his company is "reaching out to the FDA to seek further clarity," and is committed to working with the regulator through the review process.

Now what

Investors are likely pressing the panic button due to that language about "regulatory issues" in the FDA's communication. If there are problems with this NDA from Aquestive -- otherwise a promising and up-and-coming biotech -- it's best to know what they are, and how they could be addressed. No investor likes being in the dark for too long, particularly in this high-volatility sector.