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Federal Circuit Provides Guidance for Stereochemistry Claim Construction

On April 16, 2018 in a precedential opinion, the United States Court of Appeals for the Federal Circuit, Sumitomo Dainippon Pharma v. Emcure Pharms., Nos. 2017-1798, -1799, -1800, affirmed the United States District Court for the District of New Jersey by construing the claimed chemical structure diagram to encompass at least the specific enantiomer depicted, refusing to limit the claim to only cover a racemic mixture of the (+) and (–) enantiomers, absent clear indication that the depicted enantiomer should be excluded from the claim.

As a background on stereochemistry, enantiomers are different molecules with the same chemical formula and sequence of atoms but different three-dimensional configurations. Though they often have identical physical properties, enantiomers frequently have different pharmacological properties. Enantiomers may be characterized as (+) and (–) versions based on their ability to rotate polarized light in different directions. Racemates, or racemic mixtures, do not rotate polarized light because they contain equal proportions of (+) and (–) enantiomers of the same compound.

Claim 14 of asserted U.S. Patent No. 5,532,372 recited a structural drawing of the (–) enantiomer of the active ingredient in Appellee’s LATUDA® drug. Appellant ANDA filers sought to limit claim 14 to cover only racemic mixtures of the recited structure. But the district court disagreed and construed the claim to cover the specifically depicted (–) enantiomer, as well as the (+) enantiomer and mixtures of the two in any ratio. Because the branded and proposed ANDA drug products include the (–) enantiomer, this construction was dispositive as to infringement.

In affirming the district court’s claim construction, the Federal Circuit held that the plain claim language covered, at a minimum, the (–) enantiomer, without opining on whether it also covered the (+) enantiomer or mixtures. The Federal Circuit rejected Appellants’ arguments that the claim should be construed to cover only a racemic mixture of the depicted compound because one of skill in the art would understand the claim’s structural formula image to specifically depict the (–) enantiomer and nothing in the claim or specification expressly limited the claim to the racemic mixture or disclaimed/disparaged the (–) enantiomer.

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About this Author

Adam Samansky, Mintz Levin Law Firm, Boston, Patent Litigation Attorney

Adam’s practice focuses on intellectual property litigation. He handles patent, trademark, and trade secret matters on behalf of innovators and investors in a range of industries. His core practice includes patent and trade secret litigation involving complex technologies in the pharmaceutical, medical, high-tech, and defense industries. Adam has tried cases before multiple US District Courts, briefed and argued cases before the US Court of Appeals for the Federal Circuit, and has briefed bet-the-company issues before the US Supreme Court.

Joseph D. Rutkowski, Mintz Levin, Civil Litigation Matters Lawyer, Intellectual Property Litigation Matters

Joseph’s practice focuses on a variety of civil litigation matters, including patent litigation, trade secret disputes, and complex commercial litigation. Joseph’s primary focus is intellectual property litigation, and he is experienced in many aspects, including expert discovery and pretrial motion practice.

In addition, Joseph gained valuable experience representing a homeless shelter, pro bono, as lead attorney in over a dozen housing court matters, including summary process jury trial and mediations, and he supervised junior associates on related matters.

Prior to joining Mintz Levin, Joseph was an associate in the Boston litigation practice of another international law firm. During law school, Joseph was an editor on the Boston University Law Review.

Before law school, Joseph was a business and systems integration consultant, and he worked with Fortune 500 clients to implement enterprise-wide IT systems across US markets.