MannKind Corp. announced Monday that the US Food & Drug Administration had requested more information regarding its new Diabetes drug Afrezza, suggesting the approval process could take longer than expected.

Shares of MannKind Corp. (MNKD) fell sharply when the biotech firm announced Monday that it had received a Complete Response letter from the U.S. Food & Drug Administration, requesting more information regarding its New Drug Application for AFREZZA.

AFREZZA is an inhalation powder used to treat hyperglycemia in adults with type one and type two diabetes.

The letter did not cite any safety concerns, but did request updated safety data related to the drug.

“We will work closely with the FDA to answer quickly the agency's questions and satisfy the requirements,” said Chairman and Chief Executive Alfred Mann in a statement. “We are committed to working with the FDA to make AFREZZA available to patients as soon as possible."

Shares of MannKind fell $2.59 or 24.71% in Monday’s session to close at $7.89 a share.  The stock was down another 4 cents in after-hours trading.