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Validity of a Process Patent Does Not Turn on Validity of the Product Patent

July 23, 2003

Decision icon Decision

Last Month at the Federal Circuit - August 2003

Judges: Clevenger (author), Newman, and Gajarsa

In Torpharm, Inc. v. Ranbaxy Pharmaceuticals, Inc., No. 02-1590 (Fed. Cir. July 23, 2003), the Federal Circuit reversed a district court’s SJ of invalidity of U.S. Patent No. 5,670,671 (“the ‘671 patent”) for obviousness and remanded for further proceedings.

Torpharm, Inc. (“Torpharm”) owns the ‘671 patent, which discloses a process for preparing “improved Form 1 ranitidine,” an antiulcer medication. The ‘671 patent claims a process for producing improved Form 1 ranitidine by crystallizing ranitidine from a lower alcohol solution.The claims also include density limitations for the improved Form 1 ranitidine product. It is these density limitations that provide acceptable filtration and drying characteristics, and that distinguish “improved” Form 1 ranitidine from Form 1 ranitidine. The improved Form 1 ranitidine product is claimed in U.S. Patent No. 5,523,423 (“the ‘423 patent”), which issued from a divisional of the application leading to the ‘671 patent. The ‘423 patent was the subject of a separate litigation, in which a district court held that the product claim to improved Form 1 ranitidine was invalid by reason of a prior sale.

Torpharm sued Ranbaxy Pharmaceuticals, Inc. (“Ranbaxy”) for infringing the ‘671 patent, and Ranbaxy moved for SJ of invalidity, contending that the ‘671 patent had been allowed only because Torpharm represented to the PTO that the allowance of the ‘423 patent, directed to the improved Form 1 ranitidine product, made the ‘671 patent allowable. As a result, argued Ranbaxy, the subsequent invalidation of the ‘423 patent rendered the ‘671 patent invalid by reason of prosecution history estoppel and collateral estoppel. The district court agreed and granted SJ of invalidity.

Emphasizing that there are no per se rules relating the patentability of a product to the patentability of a process, and vice versa, the Federal Circuit held that Ranbaxy’s position suffered from three serious deficiencies. First, the Federal Circuit did not agree that Torpharm represented to the PTO during prosecution of the ‘671 patent that the process claims were allowable simply because the product claim was allowed in the ‘423 patent. The Court noted that Torpharm advanced a number of arguments during prosecution, including the argument that the prior art failed to disclose the use of a lower alcohol solution during recrystallization. As a result, according to the Federal Circuit, the district court was incorrect in characterizing Torpharm’s position before the PTO as relying exclusively on the novelty of improved Form 1 ranitidine.

The second problem with Ranbaxy’s position, according to the Federal Circuit, was purely logical. Even if Torpharm’s sole argument during prosecution of the ‘671 patent was that if the improved Form 1 ranitidine product is patentable over the prior art, the process of making improved Form 1 ranitidine must also be patentable, the fact that the product is later found unpatentable does not automatically render the process unpatentable as well.

Finally, the Federal Circuit held that even if the PTO allowed the process claims only because the product was novel, it does not necessarily follow that the PTO would never have allowed the process claims. The Court noted that it is not the district court’s responsibility to determine whether or not the PTO would have allowed the process claims had the product claims lacked novelty.

In reversing the district court’s SJ of invalidity, the Federal Circuit concluded that regardless of how Ranbaxy characterized the prosecution history of the ‘671 patent, collateral estoppel from the litigation invalidating the ‘423 patent does not relieve the district court from the necessity of performing a standard obviousness inquiry into the claims of the ‘671 patent.