Swiss drugmaker Roche has filed for approval of a new red blood cell stimulator product, CERA, in the USA, despite ongoing patent litigation with rival Amgen.

CERA is a long-acting erythropoietin product, filed as a treatment for renal anemia, which will compete directly with Amgen’s Aranesp (darbepoetin alfa), the latter’s top-selling product with first-quarter sales of $893 million, up 24% over the previous year.

Earlier this month, Amgen sought to ban the importation of CERA, having already filed with the US courts for an injunction preventing the manufacture or sale of the product, arguing patent infringement. Roche has countered that CERA was awarded its own US patent in 2003, a move which acknowledges that it is a novel medicine.

Analysts at Merrill Lynch said the patent litigation with Amgen made it hard to predict CERA’s sales potential, but they have forecast ex-US sales for the product of 1.3 billion Swiss francs ($1bn) in 2010, which could be hiked further by approval in chemotherapy-induced anaemia. Filings in the latter indication, which represents a global market of around $7 billion, are expected in 2009.

CERA is Roche's follow-up offering to its NeoRecormon (epoetin beta) product, and requires just once-monthly dosing, compared to Aranesp which is given weekly or every other week. NeoRecormon (also sold as Epogin) was Roche’s second best-selling drug in 2005 with sales of 2.3 billion francs.