IP Law Daily, PATENT—Fed. Cir.: Infringement and validity of patents for antibiotic drug Minocin affirmed, (Jun 9, 2026)

By Brian Craig, J.D.

The district court properly construed the patent claims and found that Nexus’s generic product infringed the patents.

The United States Court of Appeals for the Federal Circuit has affirmed the judgment of the federal district court in Illinois that the patents owned by Melinta Therapeutics, LLC, covering Minocin for treating bacterial infections are valid and infringed by the generic product developed by Nexus Pharmaceuticals, Inc. In affirming the finding of infringement, the Federal Circuit held, in a nonprecedential decision, that the district court did not err in construing the terms “composition” and “administering” in the patent claims. The Federal Circuit also affirmed the validity of the patents and held that the written description specification fully supported the district court’s observation (Melinta Therapeutics, LLC v. Nexus Pharmaceuticals, Inc., No. 25-1281 (Fed. Cir. Jun. 5, 2026)).

Melinta Therapeutics, LLC (Melinta) owns U.S. Patent Nos. 9,084,802 (“the ’802 patent”) and 9,278,105 (“the ’105 patent”). Melinta is now a wholly-owned subsidiary of the pharmaceutical company CorMedix Inc. The two patents are directed to methods in which the addition of magnesium to an injectable antibiotic formulation reduces hemolysis of red blood cells at the injection site. Melinta produces Minocin, an aqueous solution consisting of minocycline and magnesium used to treat bacterial infections. Although Minocin first entered the market in 1972, Melinta later reformulated its product to address problems with the original formulation. The patents relate to the reformulated Minocin, which added magnesium, increased the pH of the formulation, and decreased the size of the dose of the injected formulation.

In 2020, Nexus Pharmaceuticals, Inc. filed an Abbreviated New Drug Application with the FDA seeking to develop a generic version of Minocin. Melinta sued Nexus, alleging infringement of the ’802 and ’105 patents. After a bench trial, the district court found that Nexus’s generic product infringed all the asserted claims. The court also found that Nexus failed to prove the asserted claims were invalid. The district court permanently enjoined Nexus from manufacturing and selling its product until the expiration of the ’802 and ’105 patents. Nexus appealed arguing that the district court erred with both the claim construction and the challenge of patent validity.

Claim construction. The Federal Circuit first concluded that the district court properly construed the patent claims, affirming the finding of infringement. The district court properly construed the terms “composition” and “administering” in the patent claims. Although the asserted claims of the ’802 patent do not refer to a diluent, both the intrinsic and extrinsic evidence support the district court’s construction. Nexus’s proposed construction of the term “composition” suffers from an inconsistency. The district court noted that to simultaneously hold that “composition” includes a diluent but that “consists” or “consisting of” does not include a diluent is inconsistent at best, because both terms describe the same list of ingredients. A person of ordinary skill would know that it is necessary to add a diluent to the composition before administering it to the patient, as indicated in the instructions provided with the prescribing information. Therefore, the Federal Circuit affirmed the district court’s finding of patent infringement and claim construction.

Validity. The Federal Circuit also rejected the argument that the ’802 patent is invalid for lack of a written description. The most natural comparison for the claim limitation “does not include magnesium” is between a formulation that contains magnesium and one that is the same as that formulation, except without magnesium. In this case, the formulation that is otherwise the same but lacks magnesium is the prior art product, which contained minocycline without adding magnesium or any other metal cation. The specification encompasses the administration of minocycline with various metal cations, but the focus throughout is on the differences between formulations with divalent metal cations—whether magnesium or calcium—and those without. Because both the ’802 patent and the ’105 patent have the same expiration date, the Federal Circuit found it unnecessary to address the question of the validity of the ’105 patent.

Thus, the Federal Circuit affirmed the district court’s finding that Nexus’s generic product infringed the patent claims and that the patent claims are valid.

The Case is No. 25-1281.

Judge: Bryson, W.

Attorneys: Damien N. Dombrowski (Venable LLP) for Melinta Therapeutics, LLC. Imron T. Aly (Arentfox Schiff LLP) for Nexus Pharmaceuticals, Inc.

Companies: Melinta Therapeutics, LLC; Nexus Pharmaceuticals, Inc.

Cases: Patent FedCirNews GCNNews