Senju Pharm. Co., Ltd. v. Lupin Ltd.

The finding of obviousness is affirmed in view of at least seven prior-art references and the panel majority’s acceptance of the district court’s credibility finding concerning defendant’s expert witnesses.

Spring 2015

GENERICally Speaking

Case Name: Senju Pharm. Co., Ltd. v. Lupin Ltd., 2013-1630, 2015 U.S. App. LEXIS 4541 (Fed. Cir. Mar. 20, 2015) (Circuit Judges Newman, Plager, and Moore presiding; Opinion by Plager, J.; Dissent by Newman, J.) (Appeal from D. Del., Robinson, J.) 

Drug Product and Patent(s)-in-Suit: Zymar® (gatifloxacin ophthalmic solution); U.S. Pat. No. 6,333,045 (“the ’045 patent”).

Nature of the Case and Issue(s) Presented:  The invention at issue relates to gatifloxacin, a fluoroquinolone-class liquid pharmaceutical eye drop with added disodium edetate (“EDTA”). Seven prior-art patents were alleged as the basis for the obviousness determination, each containing some of the same chemistry as the claimed invention. In addition, several prior litigations involving the same chemistry and the same patent had all been tried before and related to the issues obviousness issue presented here. In the first case, the court in 2010 ruled that the asserted claims were infringed but invalid as obvious over the prior art, and the Federal Circuit affirmed. The patent-in-suit was then reexamined whereby Senju cancelled the invalid claims and added additional claims. In a second district-court action, the court found that “the reexamination of the patent-in-suit did not create a new cause of action against the same previous defendants and accused product.” The Federal Circuit again affirmed. In 2011, Senju filed the suit here, asserting infringement of the ’045 patent. As in the second suit, Senju specifically alleged infringement of the reexamined claims 6 and 12-16. The trial court held that the reexamined claims were infringed, but were invalid for obviousness. The finding of invalidity based on obviousness was appealed, and the Federal Circuit affirmed.

Why Lupin Prevailed:  The earliest prior-art references taught that then-known quinolones were both “compatible with ocular tissue” and useful in treating bacterial ocular infections through topical administration, and provided examples of those compositions’ being administered with EDTA, characterizing EDTA as a “conventional excipient.” Later prior art then brought gatifloxacin, specifically, into the fold and characterized it as an improvement over the prior-art quinolones. Still later prior art described EDTA’s impact on the permeability of organic and inorganic compounds with respect to the corneal epithelia.

Senju argued (i) that the prior art predated the claimed invention by at least eight years, “which is itself evidence of nonobviousness;” (ii) that the district court improperly declined to consider evidence on corneal permeability with reference to the composition claims; and (iii) because not a single piece of prior art disclosed 0.01 w/v% EDTA in combination with gatifloxacin, the district court arrived at its obviousness finding using improper hindsight analysis.

The Federal Circuit found the “eight-year gap” argument unconvincing and not properly raised. Senju first raised this argument in a single citation to the district court in a footnote in which it asked the district court to “acknowledge the vintage of the prior art.” The Federal Circuit found that to be “insufficient discussion to consider this argument” and that Senju had waived this argument. Regarding argument (ii) above, the Federal Circuit held that the district court properly found that corneal permeability was not relevant in the discussion of the composition claims because those claims did not contain the corneal-permeability limitation that was found in the method claim of the same patent. In response to argument (iii), the Federal Circuit found that the earlier prior art disclosed ophthalmic quinolone compositions, which gave reason to a skilled artisan to combine those earlier compositions with gatifloxacin because gatifloxacin was recognized in the art as an improved quinolone. The prior art pointed out the use of 0.01 w/v% EDTA was also known from the older references, which disclosed an exemplary formulation of 0.3% quinolone solution that incorporated 0.01 w/v% EDTA. Moreover, one of skill in the art would have known that using 0.01 w/v% EDTA would result in an increase in corneal permeability: the prior art suggested that EDTA concentrations lower than 0.5 w/v% would be effective in view of the increased corneal permeability of prior-art solutions.

The Federal Circuit also did away with Senju’s argument that the district court did not properly take into account evidence of unexpected results. It found that the increase in corneal permeability shown by plaintiffs using a 0.01 w/v% EDTA is not unexpected, but a product of routine optimization that would have been obvious to a skilled artisan.

Ultimately, the Federal Circuit found that “At bottom, the district court’s analysis rest[ed] largely on a determination that Lupin’s experts were more credible than Senju’s experts. … [T]hat determination by the district court falls well within the wide discretion the court has to weigh expert credibility.”

In her dissent, Judge Newman took issue with the panel majority’s opinion. She opined that the district court gave no deference to the PTO’s review of the restricted claim scope or the unexpected results given that scope, and holding of the narrowed claims invalid on the same grounds it had previously applied to the original claims. The panel majority did not consider the scope of the reexamined claims, the unexpected results given that scope, and the teaching-away of the “crowded” prior art. Judge Newman noted that “the specific combination and concentration here claimed is not shown, and the published scientific data lead away from the claimed subject matter.” Finally, the dissent took issue with the district court’s expert credibility finding, stating, “The published contemporaneous statements of scientists interpreting their experiments warrant more weight than unsupported opinions appearing for the first time in litigation.”

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