Federal Circuit Affirms Non-Infringement Ruling, Clearing Path for Aveva's Generic ZTlido Launch
Key Insights
The U.S. Court of Appeals for the Federal Circuit affirmed a district court ruling that Aveva's proposed generic lidocaine patch does not infringe Scilex's ZTlido patents.
The appellate court upheld the construction of "dissolving agent" as requiring the function of dissolving lidocaine, which Aveva's n-heptane-based formulation does not satisfy.
Aveva is now positioned for an imminent commercial launch of its generic lidocaine topical system 1.8% with 180-day exclusivity.
The U.S. Court of Appeals for the Federal Circuit (CAFC) on Tuesday affirmed a judgment of non-infringement in a patent dispute concerning generic versions of the topical pain patch ZTlido, clearing the way for Aveva Drug Delivery Systems (search) to launch its generic lidocaine topical system 1.8% with 180-day exclusivity.
The panel of Judges Reyna, Mayer, and Hughes, ruling per curiam, upheld the U.S. District Court for the Southern District of Florida's construction of the term "dissolving agent" and its determination that Aveva's proposed generic product did not infringe under the doctrine of equivalents.
The Underlying Patent Dispute
Scilex Pharmaceuticals Inc. holds an exclusive license to U.S. Patent Nos. 9,283,174, 9,931,403, and 9,925,264, with Itochu Chemical Frontier Corp. (search) and Oishi Koseido Co., Ltd. serving as assignees. The patents cover non-aqueous lidocaine patch compositions and methods of using them. Representative claim 1 of the '174 patent recites a non-aqueous patch containing between 0.5 and 7 mass percent lidocaine along with a dissolving agent consisting of an organic acid and a polyalcohol. Dependent claim 4 narrows that dissolving agent to a combination of isostearic acid and dipropylene glycol.
In May 2022, Aveva notified Scilex that it had submitted an Abbreviated New Drug Application (ANDA) with a Paragraph IV certification to the U.S. Food and Drug Administration, seeking approval to market a generic version of ZTlido, Scilex's branded lidocaine patch indicated for post-herpetic neuralgia (search) pain relief. Scilex, Itochu, and Oishi subsequently filed a lawsuit against Aveva in June 2022, alleging that its proposed formulation infringed claim 4 of each asserted patent under the doctrine of equivalents. At trial, Scilex conceded that Aveva's product did not literally infringe, narrowing the dispute to equivalence.
The District Court's Findings
Following a four-day bench trial in July 2024, Judge William P. Dimitrouleas rejected Scilex's reading of the claims. Scilex had argued that a "dissolving agent" is simply a substance that maintains lidocaine in a dissolved state within the finished patch, regardless of whether it also performed the dissolving function itself. The district court determined that a person of ordinary skill in the art would understand the claimed dissolving agent to serve two functions: dissolving the lidocaine and preventing its crystallization.
Based on that construction, the court found that Aveva's use of a single solvent, n-heptane, did not satisfy the limitation under the doctrine of equivalents. The district court further held that prosecution history estoppel and claim vitiation independently barred Scilex from asserting equivalence between the two-component claimed agent and Aveva's formulation.
The Federal Circuit's Analysis
On appeal, the CAFC examined the claim language and reasoned that since the patch combines a solid active ingredient with a component labeled a "dissolving agent," a skilled artisan would presume that component functions to dissolve the lidocaine. The court then turned to the specification, which describes prior art patches as suffering from poor skin permeability because the lidocaine remained undissolved and crystalline. The specification also states that the invention combines lidocaine and the dissolving agent to produce a patch in which the lidocaine is completely dissolved.
The Federal Circuit observed that all six working examples in the shared specification describe using the organic acid and polyalcohol combination to dissolve solid lidocaine before it is mixed with adhesives. The court stated that this consistent pattern bolstered the conclusion that the dissolving agent must dissolve the lidocaine, rather than merely prevent crystallization in the finished product.
During examination, the applicant Oishi had distinguished the claims from a prior art reference known as Hanma by representing, on at least three occasions, that in the claimed invention "lidocaine is dissolved in an organic acid and a polyalcohol." The CAFC acknowledged that these statements may not rise to the level of a disclaimer but noted that, under its precedent, an applicant's repeated and consistent remarks during prosecution can still inform claim construction by showing how the inventor understood the invention.
Ultimately, the Federal Circuit affirmed the district court's construction and agreed that Scilex could not establish infringement. As the opinion stated: "n-heptane, either alone or in combination with any other component, is not equivalent to the claimed 'dissolving agent.'" Since the claim construction ruling resolved the appeal, the CAFC found it unnecessary to reach the district court's alternative holdings on claim vitiation and prosecution history disclaimer.
Path to Market
With the Federal Circuit's affirmance, Aveva is now positioned for an imminent commercial launch of its generic lidocaine topical system 1.8% product, which will enjoy 180-day exclusivity as the first Paragraph IV ANDA filer. Aveva was represented on appeal by Joseph Thomas Jaros of Rakoczy Molino Mazzochi Siwik LLP, along with William A. Rakoczy, Dylan Sacenti, and Conly S. Wythers.
Aveva Drug Delivery Systems (search), a company in the DifGen Pharmaceuticals (search) family, is a fully integrated developer and manufacturer of sterile products, Transdermal Delivery Systems (TDS), and Oral Dissolvable Films (ODF), operating from licensed facilities in Miramar, Florida spanning four sites totaling 210,000 square feet.