By Randall Osborne

After reporting favorable Phase IIa study results in June for APC-366, its tryptase inhibitor to treat asthma, Arris Pharmaceutical Corp. has met with a disappointment the company characterizes as minor.

Arris, of South San Francisco, said results from a third Phase IIa trial showed a failure of APC-366 to achieve statistical significance in treating bronchial hyperresponsiveness.

The trial was a crossover study designed to find out if APC-366 could relieve lung inflammation after only four days of treatment.

David Gennarelli, director of investor relations for Arris, said the 12-subject study was optional to the ongoing trial. "We were trying to prove that our compound can do in four days what inhaled steroids take at least six weeks to do," he said.

The outcome of the study "doesn't mean the compound doesn't work; it just means it's going to take more than four days." Two-thirds of the subjects showed improvement over those in the placebo control group.

Jean Warner, Arris' vice president and chief medical officer, said the results are "not as exciting as we hoped, but we know something more about the compound. We knew it was risky." The outcome will not change the company's development strategy, she added.

"We'll probably look at this endpoint again, but at a later time point," Warner said. Next year, Arris will begin Phase IIb trials, administering APC-366, steroids and a placebo to 400 to 600 subjects over a four-week period.

APC-366 already has had two successful studies. An earlier Phase IIa study surpassed its primary endpoint by demonstrating statistical significance in late airway response. More than 25 percent of patients showed reduction compared with the placebo patients. (See BioWorld Today, June 27, 1997, p. 3.)

Arris develops synthetic small molecule therapeutics and focuses its research on protease-based discovery programs. The company is developing APC-366 with Bayer A.G., of Leverkusen, Germany.

Arris released details of the third Phase IIa study after the market closed Wednesday. Its stock (NASDAQ:ARRS) ended Thursday down $2 to $12.437. Shares closed Friday at $12, down $0.437. *