Amylin Pharmaceuticals Inc., the diabetes drugmaker that’s up for sale, has received first-round bids from Sanofi and Merck & Co., said three people familiar with the process.

The companies made offers of at least $25 a share, said the people, who declined to be identified as the deliberations are private. That would value Amylin at more than $4 billion, based on its shares outstanding as of April 26. Offers were due Friday for the San Diego-based company, whose medicines include Bydureon and Byetta, they said.

Takeda Pharmaceutical Co. and Bristol-Myers Squibb Co. have indicated to Amylin they also will make offers, the people said. Amylin began looking for suitors with Credit Suisse Group AG and Goldman Sachs Group Inc. after rejecting a $3.5 billion offer from Bristol-Myers this year, people with knowledge of the matter said last month.

Pfizer Inc., AstraZeneca Plc and Roche Holding AG had signed confidentiality agreements on the drugmaker’s sale process, people familiar with the matter said this month. It wasn’t clear whether they decided to move ahead with bids.

Spokesmen at Sanofi, Roche and AstraZeneca declined to comment. Representatives at Merck, Amylin, Pfizer and Bristol-Myers declined to comment. A U.S.-based spokeswoman for Takeda declined to comment.

Amylin received approval in January for Bydureon, a once- weekly formulation of its earlier medicine Byetta, and the drugs may draw $1.5 billion in annual revenue in the next few years, said Phil Nadeau, an analyst with Cowen & Co. in New York.

Diabetes Worldwide

Amylin’s revenue topped $650 million last year and is poised to increase about 5 percent in 2012, according to analyst estimates compiled by Bloomberg. About 346 million people in the world have diabetes, and the number of deaths from the chronic disease may double from 2005 to 2030, according to the World Health Organization. Drugmakers are working to introduce new therapies to the market, with mixed results.

Sanofi, based in Paris, is developing its diabetes business and working on lixisenatide, a treatment belonging to the same drug class as Byetta and Bydureon. Roche, based in Basel, Switzerland, returned rights to a similar experimental medicine, known as taspoglutide, to developer Ipsen SA last year after patients dropped out of trials because of side effects.

Bristol-Myers, based in New York, and London-based AstraZeneca failed to win U.S. clearance this year to sell the experimental diabetes treatment dapagliflozin as regulators sought more safety data.

Amylin had been seeking a partner to help market Bydureon outside the U.S. since November, when it ended a collaboration with Eli Lilly & Co. The company rejected Bristol-Myers’s $22-a- share bid in February, said people familiar with the matter.