Merck and Aventis Combine AIDS Drugs

Merck & Co. and Aventis SA are combining their AIDS vaccine candidates in a joint human test in the United States that will begin later this year. For reasons neither company understands, monkeys that were injected first with the Merck vaccine and then later with the Aventis medicine achieved a better immune response than monkeys given either vaccine separately or in reverse order. "It's very clear that there's a certain order of these candidates that's preferred," said Dr. John Shiver, Merck's HIV vaccine program head.

Aware that hopes for vaccine candidates have been raised and dashed numerous times, Shiver warned that the Merck and Aventis vaccine programs and newly combined effort are still in their early stages.

Merck's vaccine candidate is a modified version of a cold virus, while the Aventis candidate comes from the pox family. Merck called the French-German company to see if they could test them together. Late last year, data started to develop that a certain combination seemed to work well, Shiver said.

"This is not a sign of desperation" that the companies are testing their vaccine candidates together, said Shiver. Both companies are also continuing vaccine development independently. Merck is now testing a vaccine in 1,300 HIV-positive and HIV-negative volunteers in 70 clinical sites.

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