RPA563

RPA563 is an investigational protein subunit anthrax vaccine candidate composed of mutant recombinant protective antigen SNKE167-ΔFF-315-E308D (mrPA) without adjuvant. It is designed for post-exposure prophylaxis against Bacillus anthracis infection, aiming to elicit protective immune responses through induction of toxin-neutralizing antibodies[1][2][5][7]. RPA563 differs from Px563L, which contains the same antigen with a liposome-embedded monophosphoryl lipid A adjuvant. In clinical studies, RPA563 was administered as two intramuscular injections 28 days apart and demonstrated an acceptable safety profile (mainly mild injection site reactions) and significant immunogenicity as measured by toxin-neutralizing antibody titers.