Pfizer drops Viagra infringement case against Lilly

WILMINGTON, Del., March 17 (Reuters) - Pfizer Inc (PFE.N) agreed to drop an eight-year-old patent infringement lawsuit against Eli Lilly & Co (LLY.N) over Viagra after a U.S. government agency rejected part of the male impotence drug's patent.

The notice of agreement was filed Monday in Delaware's District Court, where Pfizer brought the case in 2002.

The district court put the case on hold last year, pending a review of Pfizer's Viagra patent by the U.S. Patent and Trademark Office.

Lilly makes the longer-acting rival Cialis.

Last month, the office partially rejected the patent because it works in a way similar to the Chinese herb Yin Yang Huo, which is sold on websites under the name Horny Goat Weed.

"We've reached an agreement with Eli Lilly with respect to the litigation, but terms of the agreement are confidential," a Pfizer spokesman said.

Officials at Lilly could not immediately be reached for comment.

The case is Pfizer Inc et al v Lilly ICOS LLC et al, U.S. District Court, District of Delaware, No. 02-01561. (Reporting by Tom Hals in Wilmington and Ransdell Pierson in New York. Editing by Robert MacMillan)