As reported in an earlier post, on March 1, 2011, Cellectis sued Precision Biosciences in the District Court of Delaware [CIV-No.-11-173] for allegedly infringing US patent number 7,897,372, directed to "I-CreI Meganuclease Variants with Modified Specificity.” The companies are both attempting to commercialize engineered meganucleases for use in genetic engineering. The litigation between Cellectis and Precision Biosciences has come to include 20 distinct lawsuits filed in Delaware and Eastern North Carolina (Precision licenses its patents from Duke University), and to involve multiple patents owned by both companies, a couple of which were discussed in this earlier post.
On May 3, the jury issued a verdict with respect to asserted claims 37, 40 and 50 from the ‘372 patent, finding all of the claims invalid for obviousness and inadequate written description. The jury also found that none of the claims are literally infringed by Precision’s meganucleases, and that Precision is not liable for inducing or contributory infringement of the claims. The jury did find that Precision meganucleases infringe claims 37 and 50 under the doctrine of equivalents.
Here are the claims:
37. A recombinant monomer of an I-CreI meganuclease variant comprising at least one mutation in the amino acid sequence of SEQ ID NO: 70, wherein said at least one mutation comprises a substitution at one or more of the amino acids residues at positions 44, 68 and 70 and said monomer further comprises at least one additional mutation of an amino acid residue directly contacting a DNA target sequence wherein said amino acid residue directly contacting a DNA target sequence is selected from the group consisting of positions 26, 28, 30, 32, 33 and 38, wherein said monomer when in a dimeric form is able to cleave DNA.
40. The monomer of an I-CreI meganuclease variant of claim 37, wherein said monomer when in a dimeric form has a modified DNA cleavage specificity relative to the I-CreI meganuclease of SEQ ID NO: 70 in at least one nucleotide in the .+-.3 to 5 triplets.
50. A single-chain chimeric meganuclease comprising the fusion of two different monomers according to claim 37.
Earlier, on April 9, 2013, the District Court issued an order denying multiple motions on summary judgment, including one relating to literal infringement of Claim 40. In one interesting aspect of the decision, the District Court judge held that the term "variant of the wild-type monomer from 1-Crel" (which appears in the preamble of claim 37, from which claim 40 depends) is an indefinite “limitation,” essentially because the court found that one of skill in the art would not be able to discern the breath of the term "variant." The court pointed out that the claim does not limit the number of mutations that could be present in the amino acid sequence of the claimed “variant,” and it is unclear at what point the number of mutations would cause the sequence to diverge so substantially from wild- type as to no longer constitute a "variant" of the wild type protein, but rather a distinct protein. The use of this sort of open-ended "variant" language is not uncommon in patent claims of this type.
It will be interesting to follow this case if it is appealed to the Federal Circuit, particularly with respect to the issue of infringement under the doctrine of equivalents. The most important Federal Circuit precedent in this area of which I am aware comes from Genentech v. Wellcome, a 1994 decision in which the Federal Circuit reversed a jury's verdict which found a claim reciting tissue plasminogen activator (t-PA) infringed under the doctrine of equivalents by a substantially re-engineered, synthetic version of t-PA (marketed as a pharmaceutical). The allegedly infringing product differed substantially in structure from the claimed protein, with 15% fewer amino acids and 10-fold greater half-life. In a concurrence, Judge Lourie pointed out that while the traditional "function-way-result" test for infringement under the doctrine of equivalents might work well for some inventions, such as in the mechanical arts, it seems a poor fit for inventions like recombinant proteins.