AS04

AS04 is an adjuvant system used in human vaccines, developed by GlaxoSmithKline. It comprises an aluminum salt (aluminum hydroxide) and monophosphoryl lipid A (MPLA), a detoxified lipopolysaccharide derivative that acts as a toll-like receptor 4 agonist.

Mechanism: The combination is designed to stimulate innate immunity through MPLA and sustain antigen presentation with aluminum, resulting in enhanced adaptive responses. This can lead to higher and broader antibody responses, and may improve cellular immunity.

Clinical use: AS04 is used in Cervarix, GlaxoSmithKline's human papillomavirus vaccine against HPV types 16 and 18. It is also used in Fendrix, a hepatitis B vaccine for individuals who fail to respond to standard vaccines. Other vaccines may incorporate AS04 in various regions.

Safety and regulatory status: As with other adjuvants, AS04 can increase local and systemic reactogenicity, such as injection-site pain and fever, but overall adverse events are comparable to other licensed vaccine formulations. Cervarix and Fendrix have received regulatory approvals in many markets, subject to local licensing.

Research and alternatives: AS04 is one of multiple adjuvant systems used to enhance vaccine immunogenicity. Ongoing work investigates its performance in other vaccine targets and in diverse populations.