QS-21-Xylose

QS-21-Xylose is a **synthetic isomeric constituent of the clinical vaccine adjuvant QS-21**, a saponin derived from the bark of the Quillaja saponaria tree[1][3][5]. QS-21 is a complex triterpene glycoside adjuvant comprising two principal isomers, QS-21-Xylose (minor, ~35%) and QS-21-Apiose (major, ~65%), which differ by the terminal sugar residue in their linear tetrasaccharide domain[1][3][5]. QS-21-Xylose enhances immune responses, primarily improving antibody generation and cytotoxic T-cell proliferation when used with protein or conjugate vaccines[1][3]. Its mechanism of action involves activation of the **NLRP3 inflammasome**, induction of IL-1β/IL-18 cytokine release, and facilitation of antigen uptake and presentation by dendritic cells, though some details remain unclear[4]. Natural QS-21 is limited by variable composition and scarcity, driving interest in synthetic QS-21-Xylose for defined, consistent adjuvant applications[1][5]. QS-21-Xylose shows **adjuvant activity** in preclinical models, supporting its use in ongoing and future clinical vaccine trials, notably in oncology and infectious disease[1][5]. Recent advances allow biosynthesis of QS-21-Xylose in engineered yeast, enabling scalable production for research and clinical development[5].

Other names

QS-21-XylQS21-XylQS 21-Xylsynthetic QS-21-Xyl