Ashley Birkett, director of pre-clinical development at the PATH Malaria Vaccine Initiative discusses their strategy towards new vaccine development
.

We’re eager at MVI to build on the progress that we’ve achieved with RTS,S. Even as we look forward to taking this first vaccine candidate through a large Phase 3 clinical trial with GlaxoSmithKline Biologicals and African scientists, we’re also moving ahead with a strategy for developing a next-generation vaccine that includes candidates that can block transmission of the parasite.

A key part of our strategy is to build on current progress. RTS,S, which is a pre-erythrocytic candidate that aims to protect against the early stage of Plasmodium falciparum malaria infection, was found to be 53 percent effective against clinical disease in Phase 2 trials. As we test this candidate in phase 3 trials at 11 sites in seven African countries, we’re already working on approaches that should help us to achieve the 2025 goal of a product that is at least 80 percent effective against clinical malaria for at least four years.

How do we plan to do this? Our approach involves a number of aspects. Our focus on pre-erythrocytic vaccine candidates—those that target the parasite on its journey to the liver or while it matures in an infected person’s liver cells—will continue. However, we plan to target other stages of the parasite’s development as well. 
In addition to widening our focus to include transmission-blocking vaccines and other approaches, we’re also pursuing candidates that target the less deadly but more widespread P. vivax malaria. These steps to further diversify our portfolio of vaccine candidates are helping to set the stage for the malaria community’s push to control malaria and to eliminate the disease in the long term.

Transmission-blocking vaccine candidates typically seek to interrupt the life cycle of the parasite by inducing antibodies that prevent the parasite from maturing in the mosquito after being taken up during a blood meal from a vaccinated person. Further, MVI has had an increasing interest in multi-stage, multi-antigen vaccines. We believe that a highly effective pre-erythrocytic, transmission-blocking vaccine that could block the parasite’s lifecycle, to reduce transmission in endemic areas, as well as provide protection from clinical disease would be a key tool in the global effort to beat back the disease.