IP Law Daily, PATENT—Fed. Cir.: No infringement found with Lupin’s generic kidney function decline drug, (May 26, 2026)

By Brian Craig, J.D.

The Federal Circuit affirmed the district court’s non-infringement and obviousness determinations of the generic version for JYNARQUE (tolvaptan).

In an infringement case involving a generic version of the drug JYNARQUE (tolvaptan) used to slow kidney function decline, the U.S. Court of Appeals for the Federal Circuit has affirmed the decision by the federal district court in Delaware that generic drug manufacturer Lupin did not infringe Otsuka Pharmaceutical’s patents. Following a bench trial, the Federal Circuit held that district court in Delaware did not err in construing the patent claims and in applying the claim construction in determining that Lupin’s process does not infringe the patent. The panel also found that the Delaware district court did not err in finding that certain of the patent claims are obvious and thus invalid (000000000000 Co., Ltd. v. Lupin Ltd., No. 24-2297 (Fed. Cir. May 21, 2026)).

Otsuka Pharmaceutical Co., Ltd. (Otsuka) owns U.S. Patent Nos. 8,501,730 and 8,273,735. The patents claim highly pure tolvaptan—a compound used to treat Autosomal Dominant Polycystic Kidney Disease (ADPKD)—and improved methods for synthesizing tolvaptan. JYNARQUE is a prescription medication used to slow kidney function decline in adults at risk of rapidly progressing Autosomal Dominant Polycystic Kidney Disease (ADPKD). In 2021, Lupin Ltd. submitted an application to the FDA seeking approval to market generic versions of JYNARQUE. Otsuka then filed a patent infringement suit against Lupin. Following a bench trial, the federal district court in Delaware concluded that the claims of both patents were not infringed. The district court also held certain claims of U.S. Patent No. 8,273,735 (the ’735 patent) were invalid for obviousness. Otsuka appealed.

Infringement. The Federal Circuit first concluded that the district court did not err in construing the patent claims and finding that Lupin did not infringe the patents. Otsuka’s primary infringement argument on appeal is that the district court adopted a “practical completion” construction for the claim term “amount” but applied a different and contradictory “absolute completion” construction in determining that Lupin’s process does not infringe the patent. Under the proper understanding of “amount,” Otsuka claims that Lupin infringes because the reaction is practically complete before 1 molar equivalent of hydrogenating agent is added to the reaction mixture. Considering the totality of the evidence, the Federal Circuit found no clear error in district court’s conclusion that Otsuka failed to prove by a preponderance of the evidence that the reduction reaction in Lupin’s tolvaptan synthesis process reaches completion before more than 1 molar equivalent of sodium borohydride has been added. Record evidence from both experts supports the district court’s conclusion. The panel found no clear error in the district court’s decision not to rely on experimental data that is, by one of the testifying expert’s own admission, flawed.

Expert testimony. Next, the Federal Circuit held that the district court did not err in admitting certain expert testimony. Patent owner Otsuka argued that Lupin’s expert was not qualified to testify as an expert. But Otsuka failed to timely object to the expert testimony before or during the bench trial. By failing to object timely, Otsuka forfeited the right to later object to the admissibility of the expert testimony. Thus, the district court did not abuse its discretion in finding that Otsuka forfeited its challenges to the expert’s status as a skilled artisan.

Obviousness. Finally, the Federal Circuit rejected Otsuka’s arguments that the district court erred in invalidating the asserted claims of the ’735 patent based on obviousness. The Federal Circuit examined the prior art and found that Lupin presented clear and convincing evidence that a person of ordinary skill in the art would have recognized a prior art reference as a viable starting point. While the Federal Circuit found that the district court overlooked certain evidence from expert testimony, any error in evaluating this secondary consideration is harmless. The appeals court confirmed that weak secondary considerations generally do not overcome a strong prima facie case of obviousness.

Therefore, the Federal Circuit affirmed the district court’s findings of non-infringement and obviousness, and that Lupin does not infringe Otsuka’s patents for the generic version of the drug.

The Case is No. 24-2297.

Judge: Hughes, T.

Attorneys: John D. Murnane (Venable LLP) for Otsuka Pharmaceutical Co. Ltd. William R. Zimmerman (Knobbe, Martens, Olson & Bear, LLP) for Lupin Ltd.

Companies: Otsuka Pharmaceutical Co. Ltd.; Lupin Ltd.

Cases: Patent FedCirNews