By Brady Huggett

Gilead Sciences Inc. has analyzed 24-week data from its ongoing 48-week pivotal Phase III trial with once-daily tenofovir disoproxil fumarate and said it has everything it needs for regulatory filings in both the United States and Europe.

The trial was designed to test the efficacy and safety of tenofovir DF when used to intensify a stable background antiretroviral regimen. The preliminary results of the trial met the study's primary efficacy endpoint, mainly a reduction in viral load, and looked at 552 treatment-experienced patients.

"We were looking for a statistically significant difference between active 300 mg dose and placebo and we achieved that," said Mark Perry, executive vice president, operations, at Foster City, California-based Gilead. "This data is what will be important for regulatory filing. What we file for the FDA and the European regulatory committee will be the 24-week analysis."

The trial, called Study 907, took place in Australia, Europe and North America and enrolled only patients who had HIV RNA levels of between 400 and 10,000 copies per milliliter and were receiving stable antiretroviral therapy for at least eight weeks prior to enrolling. Results showed that treatment of HIV-infected patients with once-daily tenofovir DF 300 mg was associated with a statistically significant average decrease in viral load over 24 weeks (p<0.0001).

"To put it in context," he said, "we saw a drop of 0.61 logs, that transfers to about a 75 percent decrease in HIV RNA." Those results, Perry said, were consistent with what Gilead saw in its 189-patient Phase II trial, though the Phase III trial has a larger patient population and entailed only one dose of tenofovir vs. placebo. In the Phase II trial, three doses were tested.

Tenofovir is a reverse transcriptase inhibitor, as are other HIV drugs such as AZT and 3TC already on the market. Perry said in earlier trials, tenofovir had shown success acting against resistant virus regardless of what therapy the patient had been taking. And treating patients already undergoing some sort of anti-AIDS therapy is daunting, Perry said, because the chance for failure is greater.

"Our intention was to evaluate tenofovir against any regimen that is out there," he said. "Most patients came in on some triple therapy, but they had measurable viral load so they were not benefiting from their therapy.

"It's a study a lot of people don't run because the patient population is difficult to treat," he added. "Most drugs don't work in that circumstance." Perry said the mean time on some prior therapy for the patients in the trial was five-and-a-half years.

Other important data from the trial related to the number of HIV RNA copies found in the bloodstream.

"The proportion of patients that go below 400 copies, how many go undetectable, that is important," Perry said. "We saw that 45 percent of the patients went below detectable, and 13 percent went below on placebo. We were very pleased with that result."

The data will make its way to the FDA sometime around mid-year, with a European filing planned simultaneously.

"I'd have to say this is the biggest value driver for Gilead right now, both in market potential and it being near term," Perry said. "This data is critical for regulatory approval for the drug. We have what we need to file. Anything additional that goes into the filing package will just be safety data."

Gilead's stock (NASDAQ:GILD) rose 37.5 cents Tuesday, to close at $70.125. n