Danish biotech company Genmab on Tuesday said rivals Genentech and Biogen Idec had appealed a judgment in favour of its partner GlaxoSmithKline in a patent infringement case involving blood cancer drug Arzerra.

Arzerra is Genmab's only commercially available product and is sold by GlaxoSmithKline.

Last month, a U.S. court ruled in favour of Arzerra, stating the drug did not infringe Genentech and Biogen Idec U.S. patent covering methods.

Genmab said Genentech and Biogen Idec originally filed the lawsuit in the first quarter of 2010.

(Reporting by Copenhagen Newsroom; Editing by Mike Nesbit)