Opinions — Thursday, May 21, 2026

Otsuka Pharmaceutical Co. v. Lupin Ltd. concerns patents related to highly pure tolvaptan and methods for synthesizing it with reduced impurities, specifically by limiting the amount of sodium borohydride used during a reduction step. The Federal Circuit affirmed the district court's bench trial findings that Lupin's ANDA manufacturing process did not infringe U.S. Patent Nos. 8,273,735 and 8,501,730, and that certain claims of the '735 patent were invalid for obviousness. The central dispute involved whether Lupin's process—which adds at least 1.2 molar equivalents of sodium borohydride but then quenches the reaction when only 0.05% of precursor compound remains—uses the claimed "amount" of hydrogenating agent present "while the reaction is taking place."

The court's infringement analysis turned on the district court's adoption of a "practical completion" standard for determining when the reduction reaction ceases to be "taking place" under the claim language, rather than a theoretical "absolute completion" standard. Reviewing for clear error after bench trial, the Federal Circuit found no reversible error in the district court's conclusion that Otsuka failed to prove the reaction reaches practical completion before more than 1 molar equivalent of sodium borohydride is added, largely because Otsuka's experimental evidence contained acknowledged anomalies and was performed under different conditions than Lupin's actual DMF process. The court also upheld the district court's forfeiture ruling under Third Circuit law regarding Otsuka's challenge to opposing expert Dr. Dichtel's qualifications as a person of ordinary skill, finding no abuse of discretion where Otsuka failed to file a Daubert motion or timely object at trial despite raising the issue obliquely in opening statements.

The Federal Circuit affirmed the Patent Trial and Appeal Board's final written decision holding all claims of Samesurf's U.S. Patent No. 9,185,145 unpatentable as obvious over Lebrun in view of Wang. The '145 patent relates to synchronized browsing sessions, and the dispute centered on whether the claim term "web browsing interaction data" encompassed partial webpages stripped of multimedia elements, as disclosed in Lebrun. Samesurf argued the term should be limited to data describing host device interactions, not data resulting from those interactions.

The court applied de novo review to claim construction with substantial evidence review of subsidiary factual findings, following Teva Pharmaceuticals and Dionex. The panel held that absent lexicography or disavowal, the patentee was entitled to the full plain and ordinary meaning of the broad term chosen, which encompassed all data related to web browsing interactions including partial webpages. The court rejected Samesurf's attempt to import limitations from a single exemplary embodiment in the specification, citing Liebel-Flarsheim for the principle that claims are not read restrictively based on described embodiments unless the patentee clearly intended to limit scope.