SQS-21

SQS-21 is a synthetic form of the saponin adjuvant QS-21, developed to provide batch-to-batch consistency and molecular homogeneity for use in vaccines[2][3]. QS-21, originally isolated from the bark of the Quillaja saponaria tree, is a potent immunological adjuvant known to enhance both antibody and T-cell responses when combined with a variety of vaccine antigens[1][2][3][7][9]. SQS-21 consists of two isomers—QS-21-Api and QS-21-Xyl—in a defined ratio (65:35), chemically synthesized to replicate the natural product in biological activity and toxicity profiles[3]. The mechanism of action of SQS-21 is not fully elucidated but it is believed to augment immune responses by stimulating antigen-presenting cells, facilitating both humoral and cellular immunity[1][2][3][7]. SQS-21 is under development and investigation as an adjuvant in vaccines against cancers (e.g., melanoma, breast, prostate), malaria, HIV, hepatitis, tuberculosis, and neurodegenerative diseases such as Alzheimer's disease[2][3][5]. Its synthetic nature eliminates issues found in naturally derived QS-21: scarcity, variability, and trace impurities[2][3].

Brand names

SQS-21SQS21SQS 21

Other names

synthetic QS-21