Minocin® (minocycline hydrochloride)
Case Name: Melinta Therapeutics, LLC v. Nexus Pharms., Inc., Nos. 2025-1281, 2025-1282, 2026 WL 1622790 (Fed. Cir. June 5, 2026) (Circuit Judges Prost, Bryson, and Reyna presiding; Opinion by Bryson, J.) (Appeal from N.D. Ill., Kness, J.)
Drug Product and Patent(s)-in-Suit: Minocin® (minocycline hydrochloride); U.S. Pat. Nos. 9,084,802 (“the ’802 patent”) and 9,278,105 (“the ’105 patent”)
Nature of the Case and Issue(s) Presented: The patents-in-suit claim methods of treating bacterial infections using injectable minocycline formulations that include magnesium. The claimed methods address injection-site hemolysis, i.e., death of red blood cells at the injection site. Specifically, claim 1 of the ’802 patent requires a magnesium-to-minocycline molar ratio greater than about 4:1, a pH between 4 and 6, and reduced injection-site hemolysis relative to IV administration of a composition that does not include magnesium. Dependent claim 7 narrows the pH range to about 4.5 to 5.5, and dependent claim 18 requires a total administered volume of less than 500 mL. Claim 27 of the ’105 patent depends from claim 1 and similarly covers IV administration of a 7-dimethylamino-tetracycline antibiotic with magnesium, where the antibiotic is minocycline. Minocin has been on the market since 1972, but Melinta later reformulated the product by adding magnesium, increasing the pH of the formulation, and decreasing the injected dose volume to address problems associated with the original formulation.
In October 2020, Nexus filed an ANDA seeking FDA approval to market a generic version of Minocin. Melinta sued and after a four-day bench trial, the district court found that Nexus’s proposed generic product infringed all asserted claims and that Nexus failed to prove invalidity based on obviousness, indefiniteness, lack of written description, or lack of enablement. Nexus appealed and the Federal Circuit affirmed.
Why Melinta Prevailed: Nexus’s principal noninfringement argument turned on claim construction. Nexus argued that because claim 1 of the ’802 patent uses the closed transitional phrase “consists of” to define the claimed composition, the claim excludes any diluent. According to Nexus, its ANDA product could not infringe because the product requires addition of a diluent before IV administration. The Federal Circuit rejected that argument, agreeing with the district court that “composition” refers to the minocycline, magnesium, and base after they are mixed to make a solution but before the further dilution needed for IV administration.
The Federal Circuit found that both intrinsic and extrinsic evidence supported Melinta’s construction. The specification describes preparing an admixture by adding a diluent, which makes the solution ready for administration. Multiple experts testified that a POSA would understand that the composition must be diluted before IV administration. The Minocin prescribing information, including both the 2010 and 1973 labels, likewise instructed that the drug should be reconstituted and then further diluted before IV administration. Nexus’s proposed construction, by contrast, would have excluded not only Nexus’s ANDA product but also Melinta’s own Minocin product, because both required dilution before administration.
Nexus also challenged the ’802 patent for lack of written description based on the claim limitation requiring reduced hemolysis relative to administration of “a composition that does not include magnesium.” Nexus argued that the patent needed to show reduced hemolysis compared to any formulation lacking magnesium, including formulations containing other metal cations such as calcium. The Federal Circuit rejected that argument on the merits, holding that the natural comparator was the same formulation without magnesium—i.e., the prior-art minocycline formulation that lacked magnesium or any other metal cation—not a formulation substituting calcium for magnesium.
The Federal Circuit found that the specification supported the district court’s written-description finding. The patent’s focus was on the benefit of adding divalent or trivalent metal cations, including magnesium, to minocycline formulations that previously lacked such cations. The specification compared formulations containing magnesium or calcium against formulations containing no metal cations, and the prosecution history likewise identified the closest prior art as commercially available IV minocycline without a multivalent cation. Because the record showed that the inventors possessed a magnesium-containing minocycline formulation that reduced hemolysis compared with the prior-art formulation lacking metal cations, the Federal Circuit held that the district court did not clearly err in rejecting Nexus’s written-description challenge.
