A US court of appeal yesterday ruled that an erythropoietin-based product in development at Shire unit Transkaryotic Therapies and Sanofi-Aventis does infringe two patents held by biotechnology company Amgen.

However, the court also overturned an earlier district court ruling that TKT had infringed another patent held by Amgen, and handed the decision on a fourth back to lower court for consideration. The district court ruled in 2004 largely in favour of Amgen in the case, and TKT and Sanofi-Aventis appealed, which led to yesterday’s ruling.

One of the appellate judges presiding over the case reportedly remarked wryly that at the current rate the disputed patents could expire before the long-running litigation, which started in 1997, actually comes to an end, according to Dow Jones.

Amgen claimed victory in the lawsuit, saying that one of the upheld patients protects its EPO franchise out to 2015. The company sells two EPO products, Aranesp (darbepoetin alfa) and Epogen (epoetin alfa), which brought in revenues of $1.31 billion and $1.22 billion, respectively, in the first half of this year.

Shire is hoping to bring its Dynepo (epoetin delta) product to market, but is unlikely to do so while the litigation with Amgen drags on. Meantime, the company still intends to roll Dynepo out in Europe, where Amgen does not sell its Epogen product itself. Here the drug is sold under license, as Procrit, by Johnson & Johnson. TKT won a pivotal legal battle clearing the way for Dynepo’s launch in Europe in 2004.

Sanofi-Aventis returned the European rights to Dynepo to TKT in the same year, and has abandoned plans at present to launch the product in the USA.

Amgen is also battling to defend its EPO franchise from Roche, whose rival product Mircera (CERA) has been filed for approval on both sides of the Atlantic. Amgen has tried and failed to ban the import of Mircera into the USA via a complaint to the International Trade Commission, and also has a pending patent infringement lawsuit against Roche.