Pfizer's patent on Viagra's main ingredient ruled invalid

A court has ruled that drug giant Pfizer's European patent on the main ingredient of its anti-impotence drug Viagra is invalid.

A court has ruled that drug giant Pfizer's European patent on the main ingredient of its anti-impotence drug Viagra is invalid.

Patents Court Justice Hugh Laddie allowed a challenge by rival U.S.-based Lilly Icos which had claimed that Pfizer's monopoly right to the active compound in the drug was void and was stifling research by other companies.

The case centered on Pfizer's patent on sildenafil citrate.

Pfizer argued that the commercial success of Viagra was a testimony to its inventiveness, the judge said.

Lilly Icos was in the process of producing its own anti-impotence drug and feared that the patent would stand in its way.

The ruling said the 1993 patent was "invalid for obviousness" because the scientific knowledge on which it was based was already in the public domain.

In the light of that "prior art," Viagra was not an "unexpected discovery", Laddie said.

Sildenafil citrate enhances the effect of the nitric oxide - which plays a key role in creating erections - by inhibiting a chemical which dampens the enzyme in the erectile tissue.

Mark Hodgson, of of the law firm of Taylor, Joynson and Garrett, for Lilly Icos, said: "My clients will be delighted to hear the outcome of this case. It vindicates 18 months of hard work in this case.

"It is up to Pfizer to talk about the financial implications."

There was no immediate reaction from New York-based Pfizer. The company's press office in London was not answering telephone calls.

The judge will hear arguments later on issues such as costs and whether to permit an appeal after the legal teams have digested his judgment.

In the third quarter, Pfizer reported sales of Viagra were up 36 percent to dlrs 332 million, or 6 percent of the company's human drugs sales.

Lilly Icos is a joint venture between Indianapolos-based Eli Lilly & Co. and Icos Corp.