Melinta Therapeutics v. Nexus Pharmaceuticals — Federal Circuit Affirms Patent Infringement in Generic Antibiotic Case

Background

Melinta Therapeutics holds U.S. Patent Nos. 9,084,802 and 9,278,105, which cover methods of treating bacterial infections using a reformulated version of the injectable antibiotic Minocin. The key innovation: adding magnesium cations to the minocycline formulation to reduce hemolysis (cell death) at the injection site. The original Minocin entered the market in 1972, but the reformulated version addressed longstanding problems with the original formulation by adding magnesium, adjusting the pH, and reducing the injection volume.

Nexus Pharmaceuticals filed an Abbreviated New Drug Application (ANDA) seeking FDA approval for a generic version of Minocin, triggering a Hatch-Waxman infringement action under 35 U.S.C. § 271(e)(2). After a four-day bench trial, the Northern District of Illinois (Judge Kness) found that Nexus’s generic product infringed all asserted claims and that Nexus failed to prove invalidity on any ground — obviousness, indefiniteness, inadequate written description, or lack of enablement. The court permanently enjoined Nexus from manufacturing or selling its ANDA product until the patents expire.

The Court’s Holding

Claim construction — “composition” and “administering.” Nexus argued that because claim 1 of the ‘802 patent uses the closed transitional phrase “consists of” and does not list a diluent among the composition’s ingredients, adding a diluent before administration should take the product outside the claim’s scope. The Federal Circuit rejected this argument. The court agreed with the district court that “composition” refers to the concentrated reconstituted solution of minocycline, magnesium, and a base — before the diluent is added. The term “administering” means giving the diluted composition to a patient. Both the specification’s instructions for preparing admixtures and expert testimony confirmed that a person of ordinary skill would understand a diluent must be added before intravenous administration. Notably, the court observed that Nexus’s own construction would exclude Melinta’s commercial product as well, since both Minocin and Nexus’s generic require dilution before use.

Written description — hemolysis comparator. Nexus also challenged the written description of the ‘802 patent’s hemolysis-reduction limitation, which requires that injection-site hemolysis “is reduced relative to intravenous administration of a composition that does not include magnesium.” Nexus argued this meant hemolysis must be reduced compared to any formulation without magnesium — including those containing calcium cations — and that the inventors never demonstrated superiority over calcium. The Federal Circuit found no clear error. The specification’s focus is on comparing magnesium-containing formulations to prior art formulations that lacked any metal cation, not on a magnesium-versus-calcium comparison. The court noted that the original 1973 Minocin prescribing information actually warned against using calcium-containing diluents due to precipitation risk, further supporting that the claims were not aimed at a magnesium-calcium comparison.

Because the ‘802 patent was upheld and both patents share the same expiration date, the court declined to reach the validity issues raised regarding the ‘105 patent, as counsel agreed that upholding either patent would sustain the injunction.

Key Takeaways

• “Consists of” does not always exclude necessary preparation steps. In pharmaceutical patent claims, the closed transitional phrase “consists of” defines the composition’s ingredients but does not preclude the addition of a diluent that is universally understood to be necessary for administration.
• Written description comparators are read in context. When a patent claims improvement over a baseline (here, reduced hemolysis “relative to” a composition without magnesium), courts will look to the specification’s focus and the relevant prior art to determine the scope of that comparison — not read the limitation to require comparison against every possible alternative.
• Practical implications for ANDA litigation. Generic challengers arguing non-infringement based on the inclusion of standard pharmaceutical excipients (like diluents) face an uphill battle when the specification and prescribing information make clear that those excipients are universally required for administration.

Why It Matters

This decision is significant for Hatch-Waxman practitioners because it addresses a recurring tension in pharmaceutical patent claims: how to interpret “consists of” language when the claimed composition requires preparation steps before administration. The Federal Circuit’s holding that a diluent — universally required for intravenous delivery — does not break the “consists of” boundary provides useful guidance for both patent drafters and generic challengers. For the pharmaceutical industry, the ruling sustains Melinta’s market exclusivity for its reformulated Minocin product until the patents expire, blocking Nexus’s entry with a generic alternative.