MICA: A novel P. vivax pre-erythrocytic malaria vaccine for broad coverage: Progression to GMP manufacture of a clinical vaccine lot

Plasmodium vivax is the world's most widely distributed human malaria parasite. Approximately 2.49 billion people live at risk of infection and an estimate of 132-391 million clinical episodes per year. Elimination of P. vivax from endemic regions is substantially more difficult than P. falciparum, due to the ability to relapse in the weeks and months following a primary parasitaemia, via a dormant liver structure known as hypnozoite. The highest endemicity estimates of P. vivax malaria globally are fast growing economies in Asia, with the largest population at risk (84% of the global population or over 2 billion people). The southern islands of Asia-Pacific are also highly endemic, followed by the Americas and Africa. The current best practice to tackle vivax malaria is a drug (primaquine) that cannot be mass administered due to the risk of haemolysis caused by the frequent G6PD genetic trait. There is no licensed vaccine yet.

Elimination of Plasmodium vivax (Pv) will be key to achieve malaria eradication, but it is proving to be far more difficult than elimination of P. falciparum (Pf). Countries where both malaria parasites co-exist have found that elimination of Pf is feasible but Pv is more resilient and extremely difficult to eliminate.
The major reason for such resilience is the liver hypnozoite. This is an extraordinary structure that P. vivax has evolved to survive in temperate and cold regions. A hypnozoite can have the ability to hide for a long period of time to reactivate in a following hot season, where mosquitoes will be next available to take a blood meal containing parasites coming from the liver rather than from a mosquito bite. Major vivax drug developments are aimed at targeting the hypnozoite, but only one drug, primaquine, is effective to treat these structures. Therefore, pre-erythrocytic vaccines such as the one proposed here, could make P. vivax elimination economically feasible or even possible, by preventing hypnozoite formation or by eliminating such structure.

We have developed a highly protective P. vivax pre-erythrocytic vaccine using the major sporozoite surface antigen (CSP) fused to the Hepatitis B virus Surface Antigen. This forms a virus-like particle (VLP) similar to Glaxo's RTS,S vaccine currently in phase III clinical trials. Our Rv21 particle in Matrix M adjuvant is highly efficacious, inducing complete, sterile protection in a highly sensitive mouse malaria model, using a very high challenge doses of transgenic parasites expressing vivax CSP. A P. vivax malaria vaccine inducing protection against the two major circulating P. vivax parasites (based on the CSP allele) is an ideal solution. Our Rv21 is the first vaccine that demonstrates high efficacy against both Pv CSP alleles, VK210 and VK247. The Rv21 VLP can form particles without the need of an extra HepB S antigen copy, which is the technology used by GSK's RTS,S and CSV-S,S. This permits the presence of more CSP antigen per HepB S (ratio 1:1), thus focusing the immune response towards the malaria antigen, rather than the carrier.

We propose here to manufacture the Rv21 candidate vaccine to GMP standards. Our pre-clinical results indicate that this could be the most effective P. vivax vaccine yet developed with additional potential to prevent hypnozoite and relapse, while offering the possibility of medium term licensure and deployment. This project will take 30 months to complete and will involve GMP production of a vaccine lot, as well as ethics and regulatory approvals for a first-in-human clinical trial.

Amongst the approximately 50 malaria vaccine candidates entering clinical trials, only two types have shown repeated clinical efficacy and remain under active development for P. falciparum malaria. These are a virus-like particle (VLP) targeting the malaria sporozoite and vectored vaccines targeting the liver-stage of the parasite's life-cycle. Both vaccine types have been shown to be safe and very immunogenic but a cost-effective deployment will require a wider coverage to prevent the two major malaria parasites: P. falciparum and P. vivax. We have recently developed a VLP presenting the P. vivax circumsporozoite on its surface. This new VLP, known as Rv21, is able to provide complete, sterile protection to 100% of the mice receiving only 5ug of Rv21 in Matrix M adjuvant, using a homologous prime boost vaccination regimen. This result contrasts with the 0% efficacy induced by heterologous prime boost regimens using recombinant chimpanzee adenovirus and MVA, which is a vaccination regimen develop at the Jenner Institute and used for other diseases.
The Rv21 vaccine candidate has a series of repeats belonging to the VK210 and VK247 alleles. This design has the aim to provide protection against the two types of P. vivax parasites that circulate in the world. Using our novel P. berghei transgenic parasites expressing the VK210 and VK247 P. vivax CSP proteins, we have found that our vaccine provides high protective levels against parasites expressing either protein.

The primary objectives of this proposal are to:
-Produce Rv21 to GMP standards and we will deliver a product suitable for a future phase I clinical trial in quantity and quality. We will rely on the Jenner's clinical biomanufacturing facility (CBF) to produce the vaccine, which has recently succeeded in producing a similar VLP for falciparum: R21.
-We will perform toxicology and stability testing.
-We will apply for ethics and regulatory approvals for a future clinical trial.

Major potential beneficiaries of our work outside the academic research environment include National Malaria Control Programmes and Ministries of Health in the approximately 95 countries where vivax malaria is endemic. Plasmodium vivax and Plasmodium falciparum are responsible for nearly all the malaria cases in the world and despite difficulties in obtaining an exact number, estimates indicate between 132-391 million clinical episodes due to P. vivax in 2009. Some countries affected by malaria are experiencing an important economical growth, such as Brazil in South America and various countries in Asia, the fastest growing economic region in the world. Unfortunately, presence of infectious diseases are slowing down the development of some of the largest economies in this region, such as India, China, Pakistan, Indonesia, Philippines and Thailand, amongst others. Such countries have a major interest in the elimination of malaria and other infectious diseases that impair economical growth. Development of an efficacious vaccine against P. falciparum and P. vivax malaria would be a major tool available for Ministries of Health to eliminate malaria from these regions.

I have participated in the presentation of seminars for wider audiences outside the university millieu. One of these was particularly attractive within our city and consisted on a seminar called 'Making Malaria History', presented in the Oxford Science venue (http://www.connectedoxford.com/events/article/?id=33458). This talk attracted secondary school students, one of whic spent some days as an intern in my lab.

Additionally, in my role as a Head of Graduate Studies at the Jenner Institute, I am participating in the Oxford's NDM summer internship programme to receive students from Asia, allowing them to spend time in our laboratory to do research on vaccine development. I have also developed a summer internship programme to receive students from Brazil and Mexico to participate in my research programmes in malaria, dengue, chagas and chikungunya and we received the first 5 summer interns in 2014, two of these in my lab and three other in various labs across the NDM department. In addition, I have established a collaborative network with the governments of Mexico and Brazil to receive graduate students and post-doctoral scientists from both countries. I have recruited in my group 7 post-doctoral scientists and 2 PhD students from Brazil and Mexico, all supported by the governments of those countries. As part of these activities, I received a departmental recognition and award for leading the organisation of a workshop 'Brazil-Mexico-Oxford' to bring scientists and directors together for discussions on potential research projects between the major universities in Brazil and the University of Oxford.