UPDATE 5-FDA asks Amylin for more details but no new trials

* FDA requests finalization of product labeling

* FDA does not ask for additional trials

* Amylin shares rise 13 pct in afternoon trading

* Alkermes shares rise 12 pct (Adds analyst comment, updates share price)

By Toni Clarke

BOSTON, March 15 (Reuters) - Amylin Pharmaceuticals Inc (AMLN.O) said U.S. health regulators did not immediately approve a once-weekly form of its diabetes drug Byetta but did not ask for lengthy new clinical trials -- a relief to investors who pushed the company's stock up over 13 percent.

In a letter to Amylin and partner Eli Lilly and Co (LLY.N), the U.S. Food and Drug Administration requested finalization of information to be included in the drug's label, and a risk evaluation and mitigation strategy, Amylin said on Monday.

"This development is positive in that it most likely removes the possibility of a lengthy delay beyond 2010," Cory Kasimov, an analyst at J.P. Morgan, said in a research report.

The agency also requested clarification of Amylin's manufacturing processes, but it did not make requests related to observations from a pre-approval inspection at an Ohio manufacturing plant.

U.S. regulators found shortcomings at the plant during an inspection in December, but Amylin said all of those observations have been addressed. [ID:nN12246564]

The new drug, with a proposed name of Bydureon, is a once-weekly version of Byetta, which is given twice daily by injection and which had sales last year of $797 million.

Byetta, whose chemical name is exenatide, is used to treat type II diabetes -- the more common form of the disease that is closely linked to obesity. Bydureon, known chemically as exenatide LAR, uses technology from Alkermes Inc (ALKS.O) to release the drug at a controlled rate.

Shares of Alkermes rose $1.54 or 12.6 percent to $13.75 in afternoon trading on Nasdaq.

In January, the FDA approved a similar drug -- Novo Nordisk A/S's (NOVOb.CO) Victoza. Both drugs belong to the GLP-1 class of drugs that stimulate insulin production to regulate blood sugar levels.

The FDA approval of Victoza, a once-daily injection, included a boxed warning for the risk of thyroid cancer.

The company declined on a conference call to give details of what it expects to see in the final label, but J.P. Morgan's Kasimov said he sees a low probability of a label that avoids a cancer risk warning.

"We still believe there's a relatively high probability of a Victoza-like label," he said. "Differentiation may occur on the breadth of the indicated target population."

Byetta has been associated with a risk of pancreatitis, a potentially fatal inflammation of the pancreas.

Amylin's shares rose $2.72 or 13.4 percent to $22.98 on Nasdaq. Shares of much larger partner Eli Lilly were off 9 cents or 0.3 percent at $35.84. (Additional reporting by Esha Dey; Editing by Gerald E. McCormick and John Wallace)