Phase 1 trial of AMA1-C1/Alhydrogel plus CPG 7909: An asexual blood-stage vaccine for Plasmodium falciparum malaria

Abstract

Background: Apical Membrane Antigen 1 (AMA1), a polymorphic merozoite surface protein, is a leading blood-stage malaria vaccine candidate. This is the first reported use in humans of an investigational vaccine, AMA1-C1/Alhydrogel, with the novel adjuvant CPG 7909. Methods: A phase 1 trial was conducted at the University of Rochester with 75 malaria-naive volunteers to assess the safety and immunogenicity of the AMA1-C1/Alhydrogel+CPG 7909 malaria vaccine. Participants were sequentially enrolled and randomized within dose escalating cohorts to receive three vaccinations on days 0, 28 and 56 of either 20 μg of AMA1-C1/Alhydrogel®+564 μg CPG 7909 (n=15),80 μg of AMA1-C1/ Alhydrogel® (n=30), or 80 μg of AMA1-C1/Alhydrogel+564 μq CPG 7909 (n=30). Results: Local and systemic adverse events were significantly more likely to be of higher severity with the addition of CPG 7909. Anti-AMA1 immunoglobulin G (IgG) were detected by enzyme-linked immunosorbent assay (ELISA), and the immune sera of volunteers that received 20 μg or 80 μg of AMA1-C1/Alhydrogel+CPG 7909 had up to 14 fold significant increases in anti-AMA1 antibody concentration compared to 80 μg of AMA1-C1/Alhydrogel alone. The addition of CPG 7909 to the AMA1-C1/ Alhydrogel vaccine in humans also elicited AMA1 specific immune IgG that significantly and dramatically increased the in vitro growth inhibition of homologous parasites to levels as high as 96% inhibition. Conclusion/Significance: The safety profile of the AMA1-C1/ Alhydrogel+CPG 7909 malaria vaccine is acceptable, given the significant increase in immunogenicity observed. Further clinical development is ongoing.