Background
Melinta Therapeutics sued Nexus Pharmaceuticals alleging that Nexus’s generic version of the antibiotic Minocin infringed two of Melinta’s patents, the eight hundred and two patent and the one hundred and five patent. These patents cover methods for treating bacterial infections by administering an injectable composition containing minocycline and magnesium to reduce red blood cell hemolysis at the injection site. The district court found that Nexus’s product infringed the patents and rejected Nexus’s arguments that the patents were invalid for lack of written description. The district court permanently enjoined Nexus from selling its generic product until the patents expired.
The court’s reasoning
The court reviewed the district court’s construction of the terms composition and administering de novo. It agreed that a person of ordinary skill in the art would understand that a diluent must be added to the composition before administration, consistent with the patent specification and prescribing information. The court also addressed whether the patent specification adequately described the reduction of hemolysis. It held that the natural comparison for the claim limitation was between a formulation with magnesium and one without magnesium, rather than a comparison with formulations containing other metal cations like calcium. The specification and evidence showed that the invention reduced hemolysis compared to prior art formulations lacking any metal cations. The court found no clear error in the district court’s conclusion that the written description requirement was met. Because the affirmation of the eight hundred and two patent was sufficient to uphold the infringement finding, the court declined to reach the issues regarding the one hundred and five patent.
We agree with the district court’s construction of both terms.
Melinta Therapeutics, LLC v. Nexus Pharmaceuticals, Inc, 2025-1281 (Fed. Cir. 2026)
What it means going forward
The decision reinforces that generic manufacturers cannot avoid patent infringement by adding standard diluents to a patented pharmaceutical composition if the patent claims the composition itself. It also clarifies that written description requirements in Hatch-Waxman cases are satisfied when the specification demonstrates a reduction in a side effect compared to the relevant prior art, even if the prior art contained different metal cations.