Opinion ID: 1405856
Heading Depth: 1
Heading Rank: 2

Heading: DISCUSSION I Obviousness of the '551 Patent

Text: We first address the district court's holding that claims 1-4 of the '551 patent would have been obvious in light of U.S. Patent Nos. 4,545,382 (the '382 patent) and 4,225,410 (the '410 patent). Obviousness is a question of law based on underlying questions of fact. Daiichi Sankyo Co., Ltd. v. Apotex, Inc., 501 F.3d 1254, 1256 (Fed.Cir.2007) (citing Winner Int'l Royalty Corp. v. Wang, 202 F.3d 1340, 1348 (Fed.Cir.2000)). We therefore review the ultimate determination of obviousness by a district court de novo and the underlying factual inquiries for clear error. Id.