Eli Lilly ( LLY - Analyst Report ) will now enjoy an additional six months of exclusivity in the US for one of its lead products, Cymbalta. The US Food and Drug Administration (FDA) recently granted pediatric exclusivity to Cymbalta, which means that Cymbalta will be protected from generic competition in the US until December 2013 instead of June 2013.

Eli Lilly, however, pointed out that Cymbalta is not approved for use in children and the company does not intend to seek approval for this patient population.

Cymbalta, one of the key products in Eli Lilly’s pipeline, is approved for a wide range of indications including the treatment of major depressive disorder and generalized anxiety disorder and the management of diabetic peripheral neuropathic pain and fibromyalgia. Cymbalta is also approved for the management of chronic musculoskeletal pain in people with chronic osteoarthritis pain or chronic low back pain.

Cymbalta, which accounted for 17.1% of Eli Lilly’s total revenues in 2011, posted total sales of $4.16 billion in 2011. US sales were $3.2 billion in 2011.

Cymbalta continues to perform well with first quarter 2012 sales in the US coming in at $857.6 million. Given Cymbalta’s current performance, the additional six month exclusivity period could result in sales of at least $1.6 billion in the US.

This bodes well for Eli Lilly, which currently faces a major patent cliff. Zyprexa, which posted sales of $4.62 billion in 2011, lost exclusivity in the EU and US in late 2011. Companies like Teva ( TEVA - Analyst Report ) and Dr. Reddy’s ( RDY - Snapshot Report ) have launched their generic version of the product and we expect a rapid erosion in Zyprexa sales. In fact, Eli Lilly expects Zyprexa sales to fall by more than $3 billion in 2012. First quarter 2012 Zyprexa sales fell 56% to $562.7 million.

We currently have a Neutral recommendation on Eli Lilly, which carries a Zacks #3 Rank (short-term Hold rating).