The famed corporate raider recently bought $200 million worth of stock in Amylin Pharmaceuticals, which is one of Lilly’s most critical partners, and the move raises questions about whether Icahn plans to push Amylin for a shakeup or a takeover, and whether that would threaten Lilly’s interests in the Byetta diabetes drug, The Indianapolis Star writes.

On the other hand, pressure from Icahn could create an opportunity for Lilly to buy out its partner and get full control of the diabetes med, which generated $650 million in sales last year. But some analysts say it could become a multibillion-dollar blockbuster if a new long-acting version in clinical trials wins approval. Recently released clinical data seemed to raise its prospects, the paper notes.

Icahn has disclosed no plans or demands yet for Amylin. If the opportunity arises, Lilly could wind up paying a ton of money to snap little Amylin away from Icahn if he decides to force the sale or restructuring of the promising San Diego drug inventor, the Star writes. Amylin has a market value of about $3.6 billion, with its shares trading in the mid-$20s.

Keeping control of Byetta is critical for Lilly as it tries to shore up its revenue base. Lilly hasn’t launched a new drug for humans since it launched Byetta three years ago, andy needs to keep Byetta to compete against other diabetes drugmakers, the paper adds. In recent years, Lilly has lost share in the diabetes drug market to Sanofi Aventis and Novo Nordisk, and is still trying to catch up.

“Lilly needs to keep this drug in the worst way,” David Kliff, publisher of Diabetic Investor, a newsletter for investors in diabetes companies, tells the Star.

“We have no way of knowing what his plans are,” Alice Izzo, an Amylin spokeswoman tells the Star. “We share his interest in our shareholder value. We’re happy to engage in dialogue with him just like with any other shareholder.”

Icahn’s interest in its partner would have no ramifications on its part-ownership in Byetta, a Lilly spokesman wrote The Star. According to language in its partnership agreement, if Amylin were to have a change in control, Lilly has 90 days to let the new partner know if it wants to end the agreement, and either side could buy out the other’s interest. Lilly also could just continue with the partnership, the spokesman adds.