Natco Pharma, a Hyderabad based pharma major with net sales of over Rs 390 crore, has filed an abbreviated new drug application with the US FDA for approval to market lenalidomide capsules in 5, 10, 15 and 25 mg strengths prior to the expiration of various US patents. Natco's lenalidomide capsules are the generic version of Celgene Corporation's Revlimid.

The company notified Celgene that its ANDA requesting approval from the FDA for a generic version of Revlimid contained a paragraph IV certification asserting that various Revlimid patents are invalid, unenforceable and/or not infringed. Lenalidomide, which is presently marketed as Revlimid by Celgene, is a derivative of thalidomide and is used in the treatment of multiple myeloma. Lenalidomide has also shown efficacy in the class of hematological disorders known as myelodysplastic syndromes (MDS).

The company believes that it will entitled to 180 days of generic market exclusivity for 25 mg strength. The market size of Revlimid in the USA is estimated to be around US$1.5 billion, growing at 44 per cent compared to last year.