Key Points:

• Claim construction — "pharmaceutical material" given plain meaning in Nexletol ANDA litigation. A visiting judge in D.N.J. construed "pharmaceutical material" to mean "a substance suitable for use as an active pharmaceutical ingredient," rejecting generic defendants' argument that the term requires a specific chemical synthesis process.
• Court refuses to import process limitations from specification into patent claims. Applying established Federal Circuit precedent, the court held that permissive specification language describing synthesis methods as "certain embodiments" does not make those methods a required element of the claims — and that the prosecution history reinforced the absence of any intent to limit.
• Implications for Hatch-Waxman patent litigation and claim drafting. The ruling underscores that composition claims defined by physical and chemical characteristics (e.g., purity, crystalline form, controlled impurity levels) generally will not be narrowed to require a particular manufacturing process absent clear intrinsic evidence of the patentee's intent to limit.

A visiting judge in the District of New Jersey has handed Esperion Therapeutics a win at the claim construction stage of its fight to protect Nexletol and Nexlizet, the company's branded non-statin cholesterol drugs, from generic competition.

In her 22-page decision in In re Nexletol/Nexlizet ANDA Litigation, Judge Jennifer Choe-Groves (a U.S. Court of International Trade judge sitting by designation) construed the sole disputed claim term, "pharmaceutical material," to carry its plain and ordinary meaning: "a substance suitable for use as an active pharmaceutical ingredient."

The ruling rejected a coalition of generic defendants' attempt to read specific manufacturing-process limitations into the patent claims. It also reinforces a bedrock principle of patent claim construction: courts generally will not import limitations from the specification into the claims absent clear evidence the patentee intended to narrow them.

Why the Decision Matters

Claim construction often determines the outcome of pharmaceutical patent litigation, and this ruling reaffirms that when a patent's specification uses permissive language — describing a synthesis method as one of "certain embodiments" that processes "generally include" — courts are unlikely to treat that language as a mandatory requirement baked into the claims.

For patentees, the opinion is a reminder that well-drafted claims focused on a composition's physical and chemical characteristics, rather than on how it was made, can survive efforts to narrow their scope at the Markman stage.

For generic challengers, the takeaway is that an argument that a claimed byproduct can only come from one process, so the claims must implicitly require that process may not carry the day when the specification and prosecution history lack a clear statement of limitation.

The litigation centers on five related Esperion patents covering bempedoic acid compositions used in Nexletol. All five share a common specification and claim priority to the same provisional application.

Eight generic pharmaceutical defendants — including Sandoz, Aurobindo, MSN Pharmaceuticals, and others — argued that the term "pharmaceutical material" should be construed to require a particular chemical synthesis process, because the specific diol and acetate impurities recited in the claims are "fingerprint" byproducts of that process. Esperion countered that the claims describe the material by what it is — a highly pure crystalline form of bempedoic acid with controlled impurity levels — not by how it is made.

The Litigation

Plaintiff Esperion Therapeutics, Inc. markets an oral agent for the reduction of low-density lipoprotein (LDL) cholesterol under the brand name Nexletol.

In a consolidated action against eight defendants, Esperion sought to enforce several of its patents directed to the development of bempedoic acid (8-hy-droxy-2,2,14,14-tetramethylpentadecanedioic acid) with purity and impurity profiles of a “commercializable” drug product for the treatment of diseases including liver disorders and cardiovascular disease.

Named as defendants are: Renata Limited, Somerset Therapeutics, LLC, Somerset Pharma, LLC, MSN Pharmaceuticals Incorporated, MSN Laboratories Private Limited, Aurobindo Pharma Limited, Apitoria Pharma Private Limited, and Sandoz Incorporated (collectively, “Defendants”).

Esperion asserted claims from U.S. Patent Numbers 11,760,714 (“the ’714 Patent”), 11,613,511 (“the ’511 Patent”), 11,926,584 (“the ’584 Patent”), 12,398,087 (“the ’087 Patent”), and 12,404,227 (“the ’227 Patent”) (collectively, the Asserted Patents), which share a common specification and claim priority to the same provisional application.

The parties disputed a single term for claim construction: “pharmaceutical material,” found in Claims 1–20 of the ’714, ’584, and ’227 Patents, and Claims 1–17 of the ’511 and ’087 Patents.

The Disputed Claim Term

The parties disputed whether the term “pharmaceutical material” contained in the Asserted Patents related to a substance or a process. Plaintiff advocated the adoption of a plain and ordinary meaning of the term “pharmaceutical material,” which it defined as “[a] substance suitable for use as an active pharmaceutical ingredient.” Plaintiff claimed that in the context of the Asserted Patents, the term “pharmaceutical material” is not just an ingredient that can be used in a drug product, “but a substance suitable for use as an active pharmaceutical ingredient.”

Defendants argued that the term “pharmaceutical material” described the result of a particular process with specific steps that had distinguished the claimed invention from the prior art. Accordingly defendants argued that the claimed invention required the result of a specific synthesis process and that the construction of “pharmaceutical material” should also require specific process steps.

The Court’s Analysis

The Court analyzed the parties’ claims under established Federal Circuit precedent that “[t]he best source for understanding a technical term is the specification from which it arose, informed, as needed, by the prosecution history … [w]hen the specification explains and defines a term used in the claims, without ambiguity or incompleteness, there is no need to search further for the meaning of the term.”

The Court considered plaintiff’s argument that language in the specification that describes the methods of preparing bempedoic acid refers to one aspect of the invention, and pharmaceutical materials comprising bempedoic acid as another aspect. Plaintiff argued that the “pharmaceutical material” referred to in multiple claims is comprised of: (1) a stable “crystalline form” of bempedoic acid; (2) a level of purity within a specified range; and (3) a controlled amount of a specified diol impurity and/or a specified acetate impurity. Plaintiff further asserted that the “specification does not state that any specific process is a requirement of the claimed inventive compositions.”

Defendants argued that the common specification makes clear the claimed “pharmaceutical material” must be bempedoic acid “produced by a particular synthetic route that generates the ‘fingerprint’ diol and acetate impurities.” Defendants asserted each claim of the ’714, ’511, ’584, and ’087 Patents states that the “pharmaceutical material” includes both bempedoic acid and the diol impurity, while each claim of the ’227 Patent states that the “pharmaceutical material” includes both bempedoic acid and the acetate impurity.

Because the combination of bempedoic acid and the diol impurity results from a synthetic process used to make the bempedoic acid, defendants argued that “pharmaceutical material” must be made by the process, otherwise the specific fingerprint impurity would not be generated.

The Court noted Federal Circuit guidance that courts generally “do not read limitations from the specification into claims.” The Court held the claim language employed “permissive language,” as advocated by Plaintiff. The Court further held it was “not evident from the specification that there was an intention to read a process limitation into the claims.”

The Court specifically determined “[t]he specification of the Asserted Patents does not describe the process recited by Defendants’ proposed construction as essential to the claimed invention,” holding it “improper to read a process limitation into the claims when there is an absence of a clear indication in the intrinsic record that the patentee intended the claims to be so limited.”

The Court rejected defendants’ reliance on the prosecution history of the Asserted Patents in support of a more narrow claim construction. During prosecution, an Examiner rejected the pending application because “the prior art already taught a high purity form of bempedoic acid,” stating “only in those cases where the purified product is as a result of the purification so different in properties and uses as to be in effect a new compound has such a purified product been considered patentable … The instant case does not come under this exception.” In response, the applicant stated that the “claimed invention is a pharmaceutical material that contains primarily an [active pharmaceutical ingredient] with a fingerprint impurity that is indicative of a method used to make the pharmaceutical material on a commercial scale, in contrast to the laboratory scale synthetic processes of the cited references.”

The Court held the prosecution history “further supports that there was no intention to read a process limitation into the claims of the Asserted Patents.”

'Ordinary Meaning' Prevails

Ultimately, the Court concluded that plaintiff’s ordinary meaning argument carried the day.

“Defendants’ proposed construction seeks to import process limitations from the specification into the claim term, while Plaintiff’s proposal seeks to define the term ‘pharmaceutical material’ by its ordinary meaning in light of a problem and solution identified in the specification,” the Court wrote.

The Court rejected defendants’ construction because it did not “read all portions of the written description in a manner that renders the Asserted Patents internally consistent” and imported “a specific process limitation contained in an embodiment of the specification based on the resulting diol and acetate impurities produced by that process.” The Court held defendants’ proposed process limitation to be inconsistent with the entire written description because “the specification discloses multiple other impurities that represent several different embodiments of the invention.”

In contrast, the Court credited plaintiff’s proposed construction as “supported by the context of the specification and prosecution history.” Thus, the Court ruled in favor of plaintiff and adopted the plain and ordinary meaning of the disputed claim term which it construed as “a substance suitable for use as an active pharmaceutical ingredient.”

Paul W. Kalish and Jonathan J. Madara are members of the IP Litigation team in Fox Rothschild’s Princeton, NJ office and write about patent litigation decisions in the District of New Jersey. Contact Paul at pkalish@foxrothschild.com or 609.895.6751 and Jonathan at jmadara@foxrothschild.com or 609.844.7428.

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