AMA1-DiCo

Long title:

AMA1 Diversity Covering

Image:

Background

Apical Membrane Antigen 1 (AMA-1) is a leading candidate for a vaccine against Plasmodim falciparum. Recombinant proteins representing the whole ectodomain (Domains I – III) of Plasmodium falciparum AMA-1 can induce antibodies that recognise native parasites and inhibit merozoite invasion of erythrocytes in vitro. To investigate the role of human antibodies in naturally acquired immunity, children in three separate endemic populations were analysed for reactivities prior to a malaria transmission season and whether or not they suffered an episode of malaria throughout the subsequent transmission season. Recombinant proteins representing the various domains of AMA-1 were used to dissect the antibody reactivities in detail. In two different communities in Kenya, antibodies against domain I were significantly associated with protection from subsequent malaria infections, in both univariate analyses and after adjusting for age. One of the Kenyan cohorts and a separate Gambian cohort antibodies to domain II were also associated with protection. However, for the Kenyan cohorts the protective associations of antibodies were only seen among the subjects that were parasite slide positive at the time of pre-season serum sampling, a phenomenon noted in previous studies from this area on antibodies to the infected erythrocyte surface. Antibodies to domain III were very rare in all populations. Results support the development of AMA-1 as a vaccine candidate and particularly the inclusion of domains I and II to induce antibody responses. They also highlight the importance of conducting prospective cohort studies in different endemic areas^1-3.

In an earlier phase of this project, a single allele PfAMA1 FVO [25-545] was produced under current Good Manufacturing Practice (cGMP)⁴. The product was subsequently clinically evaluated in a Phase I with three different adjuvants: alhydrogel, GSK’s AS02A and Montanide ISA720. The results obtained were very promising, with average growth inhibition levels of up to 50% in the higher dosages AS02A and Montanide ISA720⁵. One of the conclusions of this clinical trial was that the polymorphism in the PfAMA1 protein is a feature that should be addressed for the vaccine to be highly efficacious in the field.

The limited polymorphism (bi/trimorphism) of PfAMA1 enabled the design of three artificial PfAMA1 sequences with a very high coverage of naturally occurring alleles (on average > 97%)⁶. This Diversity Covering approach (DiCo) is expected to overcome the polymorphism found in nature and to allow a broad response to all naturally occurring AMA1 alleles. Both in rhesus and rabbit immunogenicity studies this expectation has been met^7-8.

Objectives

A major objective of the AMA1-DiCo project supported by EVI is to assess the clinical safety and immunogenicity of the AMA1-DiCo molecules as a malaria vaccine candidate.

Other objectives are successful process development, GMP manufacturing, toxicology studies and a Phase I clinical trial.

Major Milestones

Drug Substance GMP batch release: Q3 2011
Drug Product vials available for toxicity studies: Q1 2012
Toxicity studies final report: Q3 2012
Investigational Medicinal Product Dossier (IMPD) and Investigator’s Brochure (IB) preparation: in parallel to be ready for submission on receipt of the final toxicity study report
Investigational Medicinal Product Dossier submission: Q4 2012
Selection of investigational site and sponsor: Q2 2012
Planned start of clinical trial: Q1 2013
Planned end of the clinical trial: Q1 2014

In 2009, the EVI team with the help from reliable subcontractors solved a major stability and consistency issue in the DiCo molecules manufacturing process. By fine tuning the fermentation and purification processes and by applying lyophilisation to the final purified product, EVI could obtain a product stable enough to be stored frozen and used in Phase I clinical trials by meeting GMP stability requirements.

References:

I. Nebie, A. Diarra, A. Ouedraogo, I. Soulama, E. Bougouma, A. Tiono, A. Konate, R. Chilengi, M. Theisen, D. Dodoo, E. Remarque, S. Bosomprah, P. Milligan and S. Sirima, "Humoral responses to Plasmodium falciparum blood-stage antigens and association with incidence of clinical malaria in children living in an area of seasonal malaria transmission in Burkina Faso," West Africa Infect Immun, vol. 76, no. 2, pp. 759-66, 2007.
F. Osier, G. Fegan, S. Polley, L. Murungi, F. Verra, K. Tetteh, B. Lowe, T. Mwangi, P. Bull, A. Thomas, D. Cavanagh, J. McBride, D. Lanar, M. Mackinnon, D. Conway and K. Marsh, "Breadth and magnitude of antibody responses to multiple Plasmodium falciparum merozoite antigens are associated with protection from clinical malaria," Infect Immun., vol. 76, no. 5, pp. 2240-8, 2008.
S. Polley, T. Mwangi, C. Kocken, A. Thomas, S. Dutta, D. Lanar, E. Remarque, A. Ross, T. Williams, G. Mwambingu, B. Lowe, D. Conway and K. Marsh, "Human antibodies to recombinant protein constructs of Plasmodium falciparum apical membrane antigen 1 (AMA1) and their associations with protection from malaria.," Vaccine, vol. 23, pp. 718-728, 2004.
B. Faber, E. Remarque, C. Kocken, P. Cheront, D. Cingolani, F. Xhonneux, M. Jurado, M. Haumont, S. Jepsen, O. Leroy and A. Thomas, "Production, quality control, stability and pharmacotoxicity of cGMP-produced Plasmodium falciparum AMA1 FVO strain ectodomain expressed in Pichia pastoris.," Vaccine, vol. 26, pp. 6143-6150, 2008.
M. Roestenberg, E. Remarque, E. de Jonge, R. Hermsen, H. Blythman, O. Leroy, E. Imoukhuede, S. Jepsen, O. Ofori-Anyinam, B. Faber, C. Kocken, M. Arnold, V. Walraven, K. Teelen, W. Roeffen, Q. de Mast, W. Ballou, J. Cohen, M. Dubois, S. Ascarateil, A. van der Ven, A. Thomas and R. Saurwein, "Safety and Immunogenicity of a Recombinant Plasmodium falciparum AMA1 Malaria Vaccine Adjuvanted with AlhydrogelTM, Montanide ISA 720 or AS02.," PLoS One, vol. 3, no. 12, 2008.
E. Remarque, B. Faber, C. Kocken and A. Thomas, "A Diversity-Covering Approach to Immunization with Plasmodium falciparum Apical Membrane Antigen 1 Induces Broader Allelic Recognition and Growth Inhibition Responses in Rabbits," Infect Immun., vol. 76, no. 6, pp. 2660-2670, 2008.
K. Kusi, B. Faber, V. Riasat, A. Thomas, C. Kocken and E. Remarque, "Generation of Humoral Immune Responses to Multi-Allele PfAMA1 Vaccines; Effectof Adjuvant and Number of Component Alleles on the Breadth of Response.," PLoS One, vol. 5, no. 11, 2010.
K. Kusi, E. Remarque, V. Riasat, V. Walraven, A. Thomas, B. Faber and C. Kocken, "Safety and immunogenicity of multi-antigen AMA1-based vaccines formulated with CoVaccine HTTM and Montanide ISA 51 in rhesus macaques.," Malar J., vol. 10, no. 182, 2011.