Federal Circuit No. 2015-1407
In Spectrum v. Sandoz, the Federal Circuit affirmed the district court’s ruling of obviousness of claims 1-2 of U.S. Patent 6,500,829 claiming a "substantially pure” pharmaceutical compound that was 92–95% pure and non-infringement of claims 5-9 of the ‘829 patent by Sandoz's ANDA product.
The Federal Circuit ruled that a substantially pure compound (92%-95% of (6S) leucovorin, also called levoleucovorin) would have been obvious when both the 50/50 mixture ((6R) and (6S) diastereoisomers) and the pure compound were known in the art. Per the Court, the skilled artisan would have been motivated by the knowledge that the biological activity of leucovorin resides in the (6S) isomer to differentially purify that isomer from a mixture, and there is always in such cases a motivation to aim for obtaining a pure, resolved material.
The Federal Circuit also held that Sandoz would be entitled by FDA approval of its ANDA to sell “single-use vials with 175 mg or 250 mg of substantially pure levoleucovorin.” Per the Court, this was "far less" than the “at least two doses of 2000 mg each” recited in claims 5-9 of the ‘829 patent, and thus Spectrum had not established literal infringement. As for infringement under the doctrine of equivalents, the Court found that the "claim amendments and distinguishing statements on the prior art during prosecution" estopped Spectrum from asserting infringement under the doctrine. Specifically, Applicants had distinguished the prior art based on the “more stringent quantity limitations” of their claims.