By Randall Osborne

Gearing up for a Phase III trial of the "improved version" of its breast cancer vaccine, Biomira Inc. said the bridging study required by the FDA is fully enrolled and the international study will begin overseas in the fourth quarter of this year.

Bill Wickson, spokesman for Edmonton, Alberta-based Biomira, said the FDA asked for 23 patients in the bridging trial, and all are enrolled.

"[The FDA] picked that number because they had historical data on 23 patients with the old drug," Wickson told BioWorld Today. "We're hopeful they will give us approval to go ahead, and [the U.S. branch of the Phase III trial] also will start in the fourth quarter."

Planned to include 900 patients, the international trial will start first in Belgium and Germany, and then in the U.K.

The FDA requires the bridging study to show safety and efficacy of the synthetic, carbohydrate-based vaccine, Theratope, in its new version.

"It's the same drug, and the dose is the same, but the proportion of what patients get is different," Wickson said.

Theratope, which Biomira is developing with Emeryville, Calif.-based Chiron Corp., contains a mimic of Stn, a naturally occurring protein found on cancer cells. In the new vaccine recipe, Biomira increased the amount of Stn on the carrier molecule.

Vaccine Aimed At Treating 90 Percent Of Patients

Biomira believes the vaccine will work in 90 percent of women with breast cancer, Wickson said. "Rather than take the older formulation, which had very good results in Phase II, we delayed [the Phase III trial]," which had been slated to begin earlier this year. (See BioWorld Today, Aug. 22, 1997, p. 1.)

The trial, to test Theratope with low-dose cyclophosphamide after a conventional, six-month course of chemotherapy, was put off after scientists discovered a new formulation that elicited a better immune response, said Grant MacLean, Biomira's vice president for clinical and regulatory affairs.

"We found the new formulation to be 100 times more potent than the old formulation," he said. "It's the immune response to Stn that's critical, not just whether the patients are well enough to make a good immune response. The protein carrier, KLH, is also very immunogenic."

Earlier, in a Phase II trial, the vaccine boosted survival for 25 metastatic breast cancer patients to a median of 26.5 months, a statistically significant improvement over the control group's 9.2 months.

"The aim is not necessarily to drive the immune response higher in patients who already have a good immune response," MacLean added. "The aim is to have more patients with a good response."

Data from the bridging study, which will evaluate patients for 12 weeks, are expected later in the year, and the international Phase III study could yield results fit for a regulatory submission in two years, Wickson said. Endpoints of the Phase III trial will be time to disease progression and survival.

"It's a four-year trial, but we're hoping that, at the first look in two years, we'll have enough information to apply for expedited approval," Wickson said. "We'll still continue the trial." The study has been designed to evaluate survival at 36 months and 48 months.

Biomira's stock (NASDAQ:BIOMF) closed Tuesday at $1.656, up $0.093. *