By Randall Osborne

West Coast Editor

Cellegy Pharmaceuticals Inc. began a pivotal Phase III trial of Tostrex, its transdermal testosterone gel for male hypogonadism, and said the product is in a "horse race" with a similar trial of the company's nitroglycerin ointment for anal fissures.

Michael Forrest, president and CEO of South San Francisco-based Cellegy, said the company expects to file a new drug application in the first half of next year for one or both of the products.

The Tostrex study will enroll patients with hyper-gonadism, or low testosterone levels, at eight to 10 U.S. medical centers for six months.

Forrest said the trial will use a small sample of patients and is "very straightforward," measuring blood levels to discover whether the patients achieve the normal range of the hormone.

Low testosterone is characterized by diminished libido, reduced muscle size and strength. Forrest said Tostrex, applied to the outer thigh once a day, has distinct advantages over the currently available treatments: tablets, injectables and patches.

Some of the metabolites in tablets are toxic. "It's not a good trade-off, liver cancer for libido," Forrest said. Injections are painful, and often show "peak/trough" effects, leading to mood swings.

Patches seem to resolve the problems of tablets and shots, but call for "a fairly aggressive use of solvents in order to break down the skin barrier," which leads to irritation.

About 5 million men are affected by hypergonadism, but only about 5 percent of the market has been penetrated, Forrest said, adding that Tostrex has the advantage of being quick to dry and discreet.

"If you go to the beach, you don't want to be wearing a patch that brands you as a testosterone-deficient male," he said.

An even bigger potential for Tostrex lies in the "male andropause" market, Forrest said. Men over the age of 40 with somewhat lower testosterone levels may find their libido weaker, muscle mass down and sense of well-being lowered.

"It's the opposite side of Viagra," Forrest said. The drug, New York-based Pfizer Inc.'s wonder cure for impotence, "deals with plumbing, with blood flow to the penis," Forrest said, whereas Tostrex could address "the desire factor."

Also under way is the Phase III study of Anogesic (nitroglycerin ointment) for anal fissures. The primary endpoint is pain relief. In an earlier Phase III trial, the product failed to reach its primary endpoint, which was complete healing, but did show effectiveness against pain. "We flipped the endpoints," Forrest said. (See BioWorld Today, Dec. 27, 1999, p. 1.)

Cellegy's stock (NASDAQ:CLGY) closed Wednesday at $7.4375, down 50 cents.