Merck, Aventis Announce Phase I Trials of Combination AIDS VaccineMerck and Aventis Pasteur on Wednesday announced that they have begun Phase I clinical trials of two experimental AIDS vaccines used in combination, the Philadelphia Inquirer reports. The trials are intended to determine whether an Aventis experimental AIDS vaccine can be used to boost Merck's experimental HIV vaccine in order to produce a more effective cellular immune response than that of either vaccine taken alone, according to the Inquirer (Loyd, Philadelphia Inquirer, 9/18). The Merck vaccine, known as the replication-defective adenovirus type 5 vector, uses a modified common cold virus to deliver HIV genes to the body (Reuters, 9/17). The Aventis ALVAC-HIV vaccine uses a canarypox virus, which is harmless to humans, to deliver HIV genes to the body. The study, which will include 250 HIV-negative people at 17 U.S. locations, marks the first time that the Aventis vaccine is being used as a booster. The ALVAC-HIV vaccine has been involved in about 40 clinical trials since 1992, either by itself or boosted by another vaccine. All of the study participants have previously received three doses of the Merck vaccine; in this study, some will receive the Aventis vaccine, and some will receive a fourth dose of the Merck vaccine (Philadelphia Inquirer, 9/18). The decision to test the vaccines in combination comes after tests on rhesus monkeys found that the two vaccines administered together create a greater immune response against HIV than either vaccine administered alone. Monkeys injected first with the Merck vaccine and then with the Aventis vaccine were better prepared to fight off the disease than monkeys given either vaccine separately or in reverse order (Kaiser Daily HIV/AIDS Report, 3/27). Researchers hope to see the same results in humans, according to Merck spokesperson Janet Skidmore. The study is expected to take five years to complete, but preliminary data may be available in about one year, Skidmore said (Philadelphia Inquirer, 9/18).
Merck Global Vaccine Trials
Merck on Friday also announced that is has begun global clinical trials of its HIV-1 gag replication defective-adenovirus vaccine in collaboration with the HIV Vaccine Trials Network, the Wall Street Journal reports. The vaccine uses a modified cold virus to deliver a synthetically produced fragment of HIV-1 into the cells of the body (Wall Street Journal, 9/22). The trial -- which will be conducted on 435 HIV-negative people in 18 cities in North America, South America, the Caribbean, Southern Africa and Southeast Asia -- is meant to determine whether the vaccine candidate is safe, has tolerable side effects and is practical for use in a variety of settings, according to the AP/San Francisco Chronicle (AP/San Francisco Chronicle, 9/19). The study will also examine whether the vaccine stimulates an effective immune response to HIV (Wall Street Journal, 9/22).