Vacating an earlier panel decision that found Ariad Pharmaceuticals Inc.’s patent invalid, the U.S. Court of Appeals for the Federal Circuit granted Ariad’s request for an en banc rehearing of its patent infringement suit against Eli Lilly and Co. over the drugs Evista and Xigris, agreeing to consider the issue of whether 35 U.S.C. §112 includes separate written description and enablement requirements. Ariad Pharmaceuticals, Inc. v. Eli Lilly and Co., Case No. 08-1248 (Fed. Cir., August 21, 2009) (en banc) (per curiam).

Ariad first filed suit in June 2002 to obtain royalties on Lilly’s past and future sales of Evista (an osteoporosis treatment) and Xigris (a treatment for septic shock). A jury in the district court of Massachusetts found in 2006 that Ariad’s patent was valid and that Lilly’s Evista and Xigris products infringed. Ariad and its co-plaintiffs were awarded $65.2 million in back royalties and a 2.3 percent royalty on U.S. sales of the drugs until the expiration of the patent in 2019. The jury rejected Lilly’s arguments that the asserted claims were invalid for anticipation, lack of enablement or lack of written description. Following a separate bench trial, the district court ruled that the asserted claims were directed to patentable subject matter and that the patent was not unenforceable.

Lilly appealed to the Federal Circuit on several issues in the case, and a three-judge panel ruled that four claims of the patent at issue were invalid for lack of written description. The Court maintained the holding that the patent was not unenforceable for inequitable conduct, however. Ariad petitioned the Federal Circuit for rehearing en banc in June.

The Court agreed to rehear Lilly’s appeal of the judgment holding Lilly liable for infringing Ariad’s patent, which covers methods of treating human disease by regulating natural cell-signaling activity. In its decision to grant an en banc hearing, the Court requested further briefing on two issues: whether patent law contained a written description requirement separate from an enablement requirement and, if so, what the scope of the written description requirement was.

The appeal will be heard en banc on the basis of the originally filed briefs, the additional briefing requested in the order and oral argument. The Federal Circuit also invited the U.S. Solicitor General’s Office to submit an amicus brief in the case. Additional briefs of amici curiae will also be entertained and may be filed without leave of court.