Bayer Pharma AG v. Watson Labs., Inc.

Case Name: Bayer Pharma AG v. Watson Labs., Inc., Civ. No. 12-cv-517 (GMS), 2016 U.S. Dist. LEXIS 57888 (D. Del. May 2, 2016) (Sleet, J.) 

Drug Product and U.S. Patent(s)-in-Suit: Staxyn® and Levitra® (vardenafil hydrochloride trihydrate); U.S. Patents Nos. 8,613,950 (“the ’950 patent), 6,362,178 (“the ’178 patent”), and 7,696,206 (“the ’206 patent”)

Nature of the Case and Issue(s) Presented: Watson asserted that that claims of the ’178 and ’206 patents were invalid as obvious based on a combination using sildenafil as the lead compound. Watson proposed that one of skill would have modified the structure of sildenafil to arrive at the claimed invention.

Bayer argued that one of skill would not have selected sildenafil as the lead compound because it had less desirable potency and selectivity than other compounds that were known at the time. Even if one of skill would have started with sildenafil, one of skill would not have a reasonable expectation of success in modifying sildenafil to achieve the claimed invention. Such modifications would have included changing the core structure of sildenafil, changing substituents, and preparing sildenafil as a hydrochloride salt as compared to a citrate salt.

The court agreed with Bayer that Watson had not proven by clear and convincing evidence that the asserted claims were obvious.

Why Bayer Prevailed: The district court agreed with Bayer that one of skill would not have chosen sildenafil as a lead compound to address the problem.  There were well-known, better potency and selectivity PE5 inhibitors that one of skill would have chosen over sildenafil. The court noted that Watson’s expert’s reason for selecting sildenafil was based mostly on improper hindsight.

The court further agreed with Bayer that even if sildenafil were selected, significant modifications and choices would have been needed to be made to arrive at the claimed invention. In particular, the proposed combination would have required several alterations to the core structure of sildenafil. Those changes would have impacted the efficacy and biologic activity of the modified structure to eliminate any expectation of success based on studies regarding unmodified sildenafil.

Lastly, the court found that secondary considerations of non-obviousness favored Bayer. In particular, one of skill would not have expected vardenafil’s structure to be an effective PE5 inhibitor given the scope and content of the literature at the time. In addition, vardenafil demonstrated effectiveness in patients that were considered sildenafil non-responders. As such, vardenafil solved a long felt need.