Motivation To Combine Can Arise From Problem To Be Solved

Finding a new salt form of a composition obvious in view of the prior art, the U.S. Court of Appeals for the Federal Circuit held that a motivation to combine references can be gleaned not only from the prior art as a whole, but also from the nature of the problem to be solved. Pfizer Inc. v. Apotex, Inc., Case No. 06-1261 (Fed. Cir., Mar. 22, 2007,) (Michel, C.J.).

Pfizer owns U.S. Patent No. 4,879,303 (the ’303 patent), which relates to amlodipine besylate, marketed as Norvasc® for treatment of hypertension and angina. Pfizer was previously awarded U.S. Patent No. 4,572,909 (the ’909 patent), which claims certain dihydropyridine compounds and their pharmaceutically acceptable acid addition salts. The ’909 patent discloses 10 pharmaceutically acceptable acid addition salts of amlodipine and describes maleate as the preferred salt. Pfizer scientists subsequently encountered two problems with the amlodipine maleate tablet formulation: chemical instability and stickiness. After testing