The Enablement Limit of “Open Claims”

On December 15, 2014, the United States Court of Appeals for the Federal Circuit (CAFC) issued its opinion in Life Technologies Corporation v. Promega Corporation, Inc. regarding the boundaries of the term ‘comprising’. In patent practice the use of the term “comprising” in a claim signifies the elements or components specified plus anything else; this is referred to as “open claim language”.

The court held that claims in four US Patents (‘the Promega patents’) directed to methods and kits for simultaneous analysis of DNA regions comprising 3 specific repeating sequence regions are invalid for lack of enablement. According to the decision, “the surprising and unpredictable nature” of the biotechnology field was an important factor, as the quality of analysis upon inclusion of additional repeating sequence regions to the analytic protocol would result in a potentially unreliable outcome.

Background and key terms

The patents under discussion disclose the amplification of particular loci called “short tandem repeats” (STR) in the DNA sequence that can be used to create a DNA “fingerprint” unique to each individual, which is valuable in criminal forensics and health sciences. The analysis required co-amplification of multiple STR loci (“multiplexing”), a technique considered challenging at the application date of the patents due to the high degree of difficulty in predicting what will be the consequences of adding a new locus to an existing multiplex.

The Promega patents claim identification of specific combinations of loci that will successfully co-amplify, using an “open loci set” limitation, for example: “A kit …comprising… a set of short tandem repeat loci which can be co-amplified, comprising HUMCSF1PO, HUMTPOX, and HUMTH01″. LifeTech manufactures genetic testing kits that provide components for carrying out a multiplex amplification of STR loci from DNA samples. Each of these kits is designed to co-amplify STR loci combinations that include the recited loci listed in the asserted claims of the Promega patents as well as loci that are not listed in the claims.

In 2010, Promega sued LifeTech for infringement of the Promega patents. LifeTech responded that the asserted claims of the Promega patents were invalid. Both parties moved for summary judgment on infringement and invalidity. The district court ruled that LifeTech’s sales of its STR kits directly infringed the claims of the Promega patents. CAFC agreed to hear LifeTech’s challenge of the district court’s finding that the Promega patents are enabled and nonobvious, which led to the current ruling.

CAFC ruling

CAFC disagreed with Promega’s characterization that unrecited STR loci combinations in the “open loci set” claims are merely “unrecited elements” and stated that they are part of the claim scope. The CAFC determined that in this field of technology, introducing even a single STR locus to an existing multiplex has an unpredictable effect on whether the resulting multiplex will successfully co-amplify. As a result, the scope of the claims is broader than the scope of enablement, deeming the Promega patents invalid for lack of enablement. CACF further stated that “the teachings of Promega’s patents would not have enabled a skilled artisan at the time of filing to identify significantly more complicated sets of STR loci combinations that would successfully co-amplify, such as those found in LifeTech’s kits, without undue experimentation.” As a result, practicing the full scope of the claims requires “more than routine experimentation” since the specifications in the Promega patents disclosed “only a starting point for further iterative research in an unpredictable and poorly understood field.”

Future implications 

  • “Open” claim language, and specifically the term ‘comprising’, may be considered precarious, especially, under broad claim construction.
  • Claims that utilize ‘open language’ are within the scope of enablement as long as they do not purport to comprise unpredictable embodiments which include advances in the art.

To end on a positive note the CAFC also determined that substantial evidence supported the jury’s finding that LifeTech infringed U.S. Patent No. RE37,984 (“the Tautz patent”). The Tautz patent, which is owned by Max-Planck-Gesellschaft and is exclusively licensed to Promega, claims a kit for testing at least one STR locus that contains: (1) a mixture of primers; (2) a polymerizing enzyme such as Taq polymerase; (3) nucleotides for forming replicated strands of DNA; (4) a buffer solution for the amplification; and (5) control DNA.

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