Updated from 10:42 a.m. EST

Shares of Amylin Pharmaceuticals ( AMLN) plummeted Tuesday after its partner Alkermes ( ALKS) disclosed in a filing with the Securities and Exchange Commission the likelihood of regulatory delays for Byetta LAR.

Shares of Amylin were giving up 20% to $8.49 in recent trading Tuesday, while Alkermes was shedding 9.8% to $9.11.

Alkermes said it recently received feedback from the Food and Drug Administration that data submitted as part of its new-drug application (NDA) for a long-acting version of diabetes drug Byetta do not meet FDA requirements.

The data are from "correlation studies" that Amylin submitted to show that the drug manufactured by Alkermes in its facility and used in clinical trials was the same as that manufactured on a commercial scale in Amylin's facilty.

According to the filing, Amylin is in active discussions with the U.S. regulatory agency regarding the options to allow the application to be filed by the end of the first half of 2009.

Biotech Select

"If Amylin is required to initiate a new clinical study, the timing of the NDA submission would depend on the parameters of the new study, and the submission could be delayed beyond the previously stated filing timeline of by the end of the first half of 2009," Alkermes stated in the SEC filing.

"We believe it is likely they Amylin will have to do more clinical trials and that the LAR submission will be beyond mid '09," wrote Summer Street Research Partner's Tony Caserta. "The political pressure on the FDA is not to approve drugs, but rather to make sure potentially unsafe drugs are not approved."

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