Toward Cracking The Mystery Of Disease-fighter QS-21A

Called QS-21A, it has been used in more than 80 clinical trials of therapeutic vaccines against melanoma, breast cancer, small cell lung cancer, HIV and malaria.

Unlike more familiar vaccines used to prevent disease, therapeutic vaccines treat disease that already has occurred. QS-21A is added to therapeutic vaccines as an adjuvant, or booster that enhances the vaccine's effects. QS-21A makes vaccines more potent, and allows some to be effective at lower doses.

QS-21A's effects have been known for 80 years. However, the substance previously was available in limited quantities because it had to be extracted from the bark of a South American tree.

In 2005, however, David Y. Gin and colleagues at the University of Illinois at Urbana-Champaign synthesized QS-21A.

In their latest report, scheduled for the Aug. 30 issue of the Journal of the American Chemical Society, the researchers provide key information that should enable scientists to make analogues, or molecular variants of QS-21A. That research may help solve the mystery of how QS-21A works, Gin said, and why it is so potent. Some of the new analogues could be even more effective.

Reference: "Synthetic Studies of Complex Immunostimulants from Quilaja saponaria: Synthesis of the Potent Clinical Immunoadjuvant QS-21Aapi." Journal of the American Chemical Society