Genentech and Biogen Idec claim that the decision from the US court of appeals announced on April 16, 2013 in favor of GSK was against court precedent and request the US court of appeals to reconsider the case. The court of appeals will now decide whether to grant the rehearing. Genentech and Biogen Idec originally filed the lawsuit in 2010 in the U.S. District Court for the Southern District of California claiming that Arzerra infringed U.S. Patent No. 7,682,612 covering methods of treating Chronic Lymphocytic Leukemia (CLL) with CD20 antibodies. GSK denied infringement and claimed the patent was invalid and unenforceable. An initial judgement by the court in favor of GSK in December 2011 was subsequently appealed by Genentech and Biogen Idec. In April 2013 the US court of appeals upheld the original decision by the US district court in favor of GSK.