Eli Lilly and Co has hit a tough spot with the pharmaceutical company's top treatment now facing competition from cheaper generic brands and the looming loss of patent protection on other drugs.

It may be one of our most challenging periods in our history because, as the way fate would have it, we lose patent protection on a number of products between now and 2014, Lilly's Chief Executive John Lechleiter told Reuters in an interview on the sidelines of an Asia-Pacific summit.

Lilly's best selling product, its $4.5 billion a year Zyprexa schizophrenia treatment, began facing cheaper generics in the United States a few weeks ago and the company will lose protection for antidepressant Cymbalta in 2013 and its Evista osteoporosis drug the year after.

Right now I have got my hands full. My goal is to help Lilly navigate through this tough patch, said Lechleiter, who joined Lilly in 1979 as an organic chemist and became CEO in 2008.

Lechleiter ruled out acquisitions to plug the hole left by Zyprexa and pointed to Lilly's pipeline of potential medicines that were in the last stages of trials in the United States.

You can't just order up a new menu item like it's McDonald's. It's a longer-term cycle. Investors understand that, he said.

The Indiana-based company has forecast a minimum of $20 billion in sales, $3 billion in net income, and $4 billion in operating cash flow for the next few years.

Lilly, the 10th largest pharmaceutical company in the world, is now vying to become the largest player for diabetes treatments. A recent break-up with long-term biotech partner Amylin Pharmaceuticals Inc has freed up Lilly to pursue all types of diabetes products instead of being blocked by firewalls enacted as part of their partnership.

Becoming No. 1 is not out of the realm of possibility, said Lechleiter. The company, which was the first to bring insulin to consumers in the 1920s, trails Danish drugmaker Novo Nordisk.

Lechleiter said his company could be in a position to compete effectively in insulin and oral diabetes medicines as well as maintaining its presence among a type of drug that stimulates insulin release when glucose levels become too high.

Lechleiter and dozens of other executives were in Honolulu for the Asia Pacific Economic Cooperation summit and discussed trade and business concerns with officials from the 21 Asia Pacific countries, including China.

(Editing by Maureen Bavdek)

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