The U.S. Food & Drug Administration has requested four additional weeks to review MannKind’s (MNKD) experimental diabetes drug.  

The FDA was supposed to complete the review of Afrezza, an insulin therapy used to treat diabetes type 1 and 2 in adults, on Dec. 29, however the action date has been pushed to the end of January.

The move has lifted MannKind's shares more than 7.5% as previously skeptical investors turn more optimistic. As of November 30, some 24% of the Valencia, Calif-based company’s regularly traded shares were held short by investors who believed the drug would be outright rejected and the stock would fall.

Afrezza was denied by the FDA in March, which said at the time it needed more information on the product. In July, however, the FDA accepted a resubmission on the product.

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