The U.S. Court of Appeals for the Federal Circuit reversed and remanded a declaratory judgment of non-infringement based on the errors in the district court’s claim construction and infringement analysis. Intervet, Inc. v. Merial Ltd., Case No. 09-1568 (Fed. Cir., Aug. 4, 2010) (Prost, J.) (Dyk, J., concurring-in-part, dissenting-in-part). In his dissenting opinion, Judge Dyk, sua sponte, raised the issue of patent eligibility for isolated DNA sequences.

Merial’s patent was directed to “Type II” porcine circovirus (PCV-2) strains that cause post-weaning multisystemic wasting syndrome in pigs. “Type I” (PCV-1) strains were previously known, but were found not to be pathogenic. The specification disclosed five PCV-2 strains. The complete nucleotide sequences of four of the five PCV-2 strains were disclosed and compared with a representative PCV-1 sequence.

The district court construed claims as being limited to the five disclosed strains. The Federal Circuit disagreed, noting that “[s]equences are representative of the scope of broader genus claims if they indicate that the patentee has invented species sufficient to constitute the genera.” The Federal Circuit held that, by disclosing five PCV-2 species and providing a PCV-1 counter-example that does not fall under the claims, Merial had properly defined the scope of the claimed PCV-2 genus.

The Federal Circuit also held that the district court had improperly applied prosecution history estoppel under the doctrine of equivalents. During prosecution, a claim directed to 13 open reading frames (ORFs) of PCV-2 was rejected on the grounds that it “could encompass ORFs from any organism.” Merial disagreed with the examiner, but nonetheless amended the claim by adding the limitation that the ORFs were “of porcine circovirus type II.” The district court determined that this narrowing amendment estopped Merial from asserting that the claim covered other non-claimed PCV-2 ORFs as equivalents. The Federal Circuit disagreed and held that “[s]uch a draconian preclusion would be beyond a fair interpretation of what was surrendered.” According to the Federal Circuit, the proper extent of the estoppel was that Merial was estopped from arguing that ORFs of circoviruses found in other organisms or ORFs of PCV-1 are equivalent to the claimed PCV-2 ORFs, but Merial was not estopped from asserting a non-claimed PCV-2 ORF as an equivalent.

Judge Dyk dissented in part and expressed his opinion that isolated DNA sequences are likely unpatentable subject matter under § 101. Judge Dyk noted that the claims were not limited to use of an isolated DNA in a vaccine or other applications, but were directed to an isolated DNA molecule itself. While the Federal Circuit has upheld the validity of gene patents before, Judge Dyk pointed out that none of the cases directly address the patent eligibility requirement under Section 101. Citing Bilski, Funk Bros., and Chakrabarty, Judge Dyk argued that in order for a product of nature to satisfy § 101, “it must be qualitatively different from the product occurring in nature, with ‘markedly different characteristics from any found in nature.’” Judge Dyk believed that “[i]t is far from clear that an ‘isolated’ DNA sequence is qualitatively different from the product occurring in nature” and that “allowing the patenting of naturally occurring substances” like DNA would “preempt the use by others of substances that should be freely available to the public.”