SB AS-2

**Semantic type:** Pharmacologic Substance

**Definition:** A proprietary vaccine adjuvant consisting of an oil-in-water emulsion of saponin QS21 and monophosphoryl lipid A with potential immunostimulating activity. Mono-phosphoryl lipid A is a detoxified derivative of lipid A, a component of lipopolysaccharide (LPS) found in most gram-negative bacteria. QS21 is a purified saponin fraction extracted from the South American tree Quillaja saponaria Molina. When co-administered with peptide vaccines, the adjuvant vaccine may elicit strong humoral and cellular immune responses.