Health Law Daily Wrap Up, HATCH WAXMAN ACT—D. Del.: Court rejects Vertex bid to expand ivacaftor patent scope, (Aug 28, 2026)

By WK Editorial Staff

Lupin’s generic cystic fibrosis drug did not infringe Vertex patents because the patents were limited to formulations containing approximately 80% ivacaftor.

A federal district court in Delaware rejected Vertex Pharmaceuticals Inc.’s attempt to stop a generic version of its cystic fibrosis treatment, concluding that the company was trying to stretch narrowly claimed patent limitations far beyond the boundaries it established when obtaining the patents (Vertex Pharmaceuticals Inc. v. Lupin Limited, No. 22-cv-966-SB (D. Del. Aug. 24, 2026)).

Active ingredient. The dispute centered on how much ivacaftor, the active ingredient in Vertex’s Kalydeco drug, must be present in a formulation to fall within the scope of several patents. Vertex sued Lupin Limited under the Hatch-Waxman Act, claiming that Lupin’s application for its own ivacaftor drug infringed its patents. Specifically, Vertex argued that Lupin’s proposed generic product infringed patents covering formulations containing either 80% ivacaftor or “about 80%” ivacaftor. The court disagreed, holding that a product containing roughly 74.25% ivacaftor could not reasonably be treated as the same thing.

Patent applications. The court’s analysis focused heavily on the history of Vertex’s patent applications. Years earlier, Vertex had published research describing amorphous solid dispersions of ivacaftor and broadly disclosed formulations containing between about 10% and about 80% ivacaftor. When Vertex later sought patent protection, a patent examiner initially rejected the claims based on that earlier disclosure. Vertex overcame the rejection by presenting evidence that a formulation containing exactly 80% ivacaftor produced unexpectedly favorable solubility results. According to the court, that showing persuaded the examiner that the specific 80% concentration was distinctive and patentable.

The court emphasized that Vertex subsequently attempted to claim a broader range, covering approximately 72% to 88% ivacaftor, but the examiner rejected those claims. The examiner reasoned that unexpected results demonstrated at a single concentration do not automatically extend across a broad range of concentrations. As a result, Vertex ultimately obtained claims limited to 80% ivacaftor or “about 80%” ivacaftor.

That prosecution history became the foundation of the court’s infringement analysis. Vertex contended that “about 80%” should be understood as referring more generally to a “high drug load” formulation, potentially encompassing concentrations from approximately 70% to 90%. The court found that argument unsupported by either the patent language or the prosecution record. The phrase “high drug load” appeared nowhere in the patents, and Vertex offered no persuasive scientific rationale for treating a formulation containing about 74% ivacaftor as equivalent to one containing about 80%.

Expert testimony. The court instead credited testimony from Lupin’s expert, who testified that a person skilled in pharmaceutical formulation would understand “about” to mean “nearly the same as.” The expert also explained that the patents and prosecution materials repeatedly measured ivacaftor content with substantial precision, often to a tenth of a percentage point. That interpretation aligned with statements made by the patent examiner, who had viewed “about 80%” as encompassing only very small variations from 80%.

Because Lupin’s formulation differed from the claimed concentration by more than a few percentage points, the court found no literal infringement. The gap between roughly 74% and 80% was simply too large to fit within the ordinary meaning of “about 80%” as reflected in the patents and their prosecution history.

Doctrine of equivalents. The court also rejected Vertex’s fallback argument under the doctrine of equivalents. That doctrine allows patentees in limited circumstances to reach products that do not literally satisfy claim language but are substantially the same as the claimed invention. The court concluded that the doctrine could not be used to erase the precise numerical limitations that Vertex itself relied on to secure patent protection.

According to the court, the patents claimed specific percentages rather than broad categories of “high drug load” formulations. Allowing Vertex to treat a 74% formulation as equivalent to an 80% formulation would effectively eliminate the numerical boundaries that defined the invention. The court further noted that Vertex had previously failed to obtain patent claims covering broader concentration ranges and could not use the doctrine of equivalents to recapture subject matter that the patent examiner had already refused to allow.

Performance characteristics. The court was also unpersuaded by Vertex’s emphasis on the products’ similar performance characteristics. Vertex pointed to evidence that the two drugs had comparable dissolution profiles and were bioequivalent. But the court explained that bioequivalence is not the same as patent infringement. Generic drugs are expected to perform similarly to brand-name products, and treating bioequivalence as proof of infringement would effectively prevent the marketing of lawful generics.

In the court’s view, the case ultimately came down to the limits Vertex accepted during patent prosecution. Vertex persuaded the Patent Office that a specific concentration produced unexpected results and thereby secured patents tied to that concentration. Having obtained those narrower claims, the company could not later argue that the patents covered a much broader range that it never succeeded in patenting. The court therefore rejected all infringement claims against Lupin.

The case is No. 22-cv-966-SB.

Judge: Bibas, S.

Attorneys: Alexandra J. Cho (White & Case LLP) for Vertex Pharmaceuticals Inc. Francis J. Murphy, Jr. (Murphy, Spadaro & Landon) for Lupin Ltd.

Companies: Vertex Pharmaceuticals Inc.; Lupin Ltd.

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