Synthetic saponins

Memorial Sloan-Kettering Cancer Center researchers have designed vaccine adjuvants that are synthetic derivatives of Antigenics Inc.'s QS-21,¹ a purified fraction of a plant extract containing a mixture of two natural saponin isomers. The team thinks its molecules could be safer and more stable than the parent compound, although the efficacy of the synthetic adjuvants still needs to be proven.

Adjuvants are inherently risky, as their job is to elicit and increase the body's reaction to a given vaccine. Indeed, the only approved vaccine adjuvants in the U.S. are aluminum salts, which are generically called alum, and AS04, which is a combination of aluminum hydroxide and monophosphoryl lipid A (MPL). Alum and AS04 are safe, but have low immunogenicity and thus low efficacy...