Monophosphoryl lipid A receptor (Toll-like receptor 4) (TLR4)

Monophosphoryl lipid A (MPLA) is a detoxified derivative of lipid A, the bioactive component of lipopolysaccharide (LPS or endotoxin) from Gram-negative bacteria. When incorporated into liposomes, MPLA functions as a potent and safe vaccine adjuvant. The liposomal formulation enhances antigen delivery, stabilizes MPLA, and dramatically reduces toxicity compared to free lipid A. MPLA acts primarily as an agonist of Toll-like receptor 4 (TLR4), activating innate immune responses, boosting antigen presentation, and promoting cytotoxic T cell induction. Liposomal MPLA is widely used in modern adjuvant systems—such as AS01 and ALFQ—for vaccines against infectious diseases and in experimental immunotherapies for cancer and substance abuse. The advantage of this formulation is sustained immunostimulation with minimal side effects, supporting strong antibody and cell-mediated immunity

Other names

MPLAliposomal MPLAmonophosphoryl lipid AArmy Liposome FormulationALF3D-PHAD®

Agonist at Toll-like receptor 4 (TLR4); Binding to C-type lectin receptors (via glycans); Modulation of antigen presentation pathways (MHC class I); Induction of cytokine and inflammasome responses (Th1 bias)