AS01B (GSK)

AS01B is a liposome-based adjuvant system developed by GSK, containing two potent immunostimulants: 3-O-desacyl-4'-monophosphoryl lipid A (MPL) and the saponin QS-21. MPL is a detoxified derivative of lipopolysaccharide that acts as a Toll-like receptor 4 (TLR4) agonist, while QS-21 is a purified triterpene glycoside that stimulates the NLRP3 inflammasome. Formulated in liposomes, these components work synergistically to activate antigen-presenting cells (APCs), particularly dendritic cells, and promote strong, durable T-cell and antibody responses. AS01B is the high-dose version (50 µg each of MPL and QS-21) used in the herpes zoster vaccine (Shingrix) and the malaria vaccine (Mosquirix). Beyond its role in prophylactic vaccines, AS01B is being explored as an intratumoral immunotherapy to modulate the tumor microenvironment and enhance the efficacy of checkpoint inhibitors in advanced solid tumors.

Other names

Adjuvant System 01B