Senju Pharma. Co., LTO v. Lupin Ltd.

Case Name: Senju Pharma. Co., LTO v. Lupin Ltd., Civ. No. 11-271-SLR (Consol.), 2013 U.S. Dist. LEXIS 112439 (D. Del. August 9, 2013) (Robinson, J.)

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

Nature of the Case and Issue(s) Presented:  The Court previously found that claims 1-3, 6, 7, and 9 of the ’045 patent were infringed, but invalid. The ’045 patent was the subject of a reexamination proceeding and claims 6, 12-16 emerged. Defendants raised collateral estoppel arguments, but the court declined to entertain them. The court previously determined that the plaintiffs did not fully litigate a claim with a limitation of 0.01 w/v% disodium edetate (“EDTA”). The court found that defendants infringed claims 12-16 of the ’045 patent because they presented no evidence of non-infringement at trial and their experts testified that they were not asked to opine on infringement of the reexamined claims. The court also found that defendants infringed claim 6. Claim 6 is a method claim using the components of claim 12. The court construed claim 6 as requiring “an increased concentration of gatifloxacin in the aqueous humor.” Plaintiffs did not test defendants’ ANDA products. Rather, plaintiffs demonstrated that the inclusion of EDTA in the formulation created increased concentration of gatifloxacin, and expert testimony supported that conclusion. The court also rejected defendants’ additional non-infringement arguments. Finally, the court found the patents obvious in view of the prior art. Defendants presented a prima facie case of obviousness, which was not rebutted by plaintiffs’ claim of unexpected results.

Why Defendants Prevailed:  Relying on previous findings concerning the nature of the prior art, the court found the differences between the prior art and the re-examined claims minimal. Those differences were: (i) using 0.3 w/v% to 0.8 w/v% gatifloxacin; (ii) having a pH of above 5 to 6; and (iii) using 0.01 w/v% EDTA to increase corneal permeability. The court adopted its previous analysis concerning the use of gatifloxacin and EDTA. The prior art explicitly recites the claimed concentration range of gatifloxacin and the use of 0.01 w/v% of EDTA. The court also found that the pH range did not distinguish the claims from the prior art since pH ranges from 3 to 6.5 were disclosed in the prior art.

With respect to claim 6, the method claim, plaintiffs argued that the prior art did not demonstrate that its formulation would increase corneal permeability. The court disagreed. Relying on its previous findings, the court found that the prior art demonstrated that one of ordinary skill in the art would understand that EDTA concentrations lower than 0.5 w/v% would be effective when calcium was added. Thus, the asserted claims were prima facie obvious. In response, plaintiffs contended that the claimed invention achieved unexpected results. In particular, plaintiffs argued that the increase in corneal permeability was greater than expected. The court rejected that argument since the increased magnitude was a product of routine optimization that would have been obvious to one skilled in the art.