QS-21 is a purified plant extract used as a vaccine adjuvant. It is derived from the soap bark tree (Quillaja saponaria), which is native to the countries of Chile, Peru, and Bolivia. [1] The crude drug (Quillajae cortex) is imported from Peru and Chile. [2]
The extract contains water-soluble triterpene glycosides, which are members of a family of plant-based compounds called saponins. It has been tested as an adjuvant in various vaccines in attempts to improve their efficacy. It is believed to enhance both humoral and cell-mediated immunity. [1]
Isolation of QS-21 destroys the soap bark tree, which has resulted in regulation of the tree by the governments where it is grown. A semi-synthesis strategy relies on purifying the prosapogenin (triterpene and branched trisaccharide) part of the molecule and adding the rest of QS-21 synthetically; this is reported to increase the yield by 2 orders of magnitude. [1] This semi-synthetic approach has also facilitated experimentation with alternative acyl chain compositions. [3]
QS-21 has undergone clinical evaluation as an additive for various trial vaccines, including those for HIV, malaria and cancer. As of 2002 [update], it had been tested in more than 3000 patients in 60 clinical trials. It is a component of the AS-01 adjuvant used in the Shingrix vaccine [4] and of the Matrix-M adjuvant used in the Novavax COVID-19 vaccine.
Agenus Inc. is the sole US-manufacturer of an FDA-approved, patented extract. Supplies are tightly controlled, and the US has invoked the US Defense Production Act to preserve vaccine raw materials for its own companies. [5] [6]
QS-21 is a purified plant extract used as a vaccine adjuvant. It is derived from the soap bark tree (Quillaja saponaria), which is native to the countries of Chile, Peru, and Bolivia. [1] The crude drug (Quillajae cortex) is imported from Peru and Chile. [2]
The extract contains water-soluble triterpene glycosides, which are members of a family of plant-based compounds called saponins. It has been tested as an adjuvant in various vaccines in attempts to improve their efficacy. It is believed to enhance both humoral and cell-mediated immunity. [1]
Isolation of QS-21 destroys the soap bark tree, which has resulted in regulation of the tree by the governments where it is grown. A semi-synthesis strategy relies on purifying the prosapogenin (triterpene and branched trisaccharide) part of the molecule and adding the rest of QS-21 synthetically; this is reported to increase the yield by 2 orders of magnitude. [1] This semi-synthetic approach has also facilitated experimentation with alternative acyl chain compositions. [3]
QS-21 has undergone clinical evaluation as an additive for various trial vaccines, including those for HIV, malaria and cancer. As of 2002 [update], it had been tested in more than 3000 patients in 60 clinical trials. It is a component of the AS-01 adjuvant used in the Shingrix vaccine [4] and of the Matrix-M adjuvant used in the Novavax COVID-19 vaccine.
Agenus Inc. is the sole US-manufacturer of an FDA-approved, patented extract. Supplies are tightly controlled, and the US has invoked the US Defense Production Act to preserve vaccine raw materials for its own companies. [5] [6]