Introduction and Background of the Project

Introduction

Despite intensive control efforts over the past decade, malaria remains one of the most significant global public health threats, leading to substantial morbidity and mortality. Given the limitations of the currently most advanced malaria vaccine candidate (RTS,S, or Mosquirix), including low efficacy, more effective second-generation malaria vaccines are urgently needed. In this proposal, we build on the success of the previous GHIT-funded T2018-151 project to further advance the development of a blood-stage malaria vaccine candidate based on PfRipr5; this novel antigen may be part of a more effective multi-antigen-multistage second-generation malaria vaccine in the future.

Project objective

This project will build on the established successful collaboration between the partners to further advance the development of the PfRipr5 malaria vaccine candidate. The main objectives are to:

1.   Establish a process for PfRipr5 production compliant with current Good Manufacturing Practice (cGMP)

2.   Produce PfRipr5 for safety-toxicology study according to cGMP

3.   Perform a safety-toxicology study to evaluate PfRipr5 formulated with the SA-1 adjuvant

4.   Prepare the dossier for Phase I/IIa clinical trial

Project design

The project workplan has been structured according to the four research objectives defined above. In objective 1, the production and purification processes of PfRipr5 will be fine-tuned using the optimal expression system identified in the previous project (T2018-151). In objective 2, the established manufacturing process will be transferred to the selected CDMO, where PfRipr5 will be produced in accordance with cGMP. PfRipr5 will be formulated with SA-1 and further evaluated in a pre-clinical GLP safety-toxicology study (objective 3). Finally, under objective 4, the clinical trial documentation will be prepared for subsequent ethical and regulatory approval to conduct a Phase I/IIa clinical trial.

How can your partnership (project) address global health challenges?

Malaria remains a very significant global public health problem, especially in Africa, certain parts of Asia and the Americas, causing substantial morbidity and mortality. The disruption of malaria prevention, diagnosis and treatment that occurred during the COVID-19 pandemic, led to an increase in malaria burden in 2021 compared with 2019 in most moderate and high transmission countries, especially in sub-Saharan Africa (WHO World Malaria Report 2022). The reduction and finally eradication of malaria will require a comprehensive and integrated control strategy in which vaccines – the most cost effective and easily administered means of controlling infectious diseases – represent a key technology. Therefore, the research activities planned within this project will contribute to the development of a more effective second-generation malaria vaccine as part of this public health strategy.

What sort of innovation are you bringing in your project?

Development of effective asexual blood-stage malaria vaccine antigens so far has been hampered by the high polymorphism levels in Plasmodium falciparum antigens, often resulting in strain-specific immunity that reduces vaccine efficacy in clinical trials. In contrast, the antigen targeted in this proposal is a highly conserved and novel asexual blood-stage vaccine candidate antigen that promises to overcome the limitations faced so far with blood-stage antigens. In addition, this project employs a novel TLR7 adjuvant (SA-1) to induce a potent and durable effect.

Role and Responsibility of Each Partner

The project partners have long-standing collaboration histories and will bring complementary expertise to ensure the successful completion of the proposed activities. The European Vaccine Initiative (EVI) will be responsible for overall coordination and management and will lead clinical protocol development and dossier preparation required for future ethical/regulatory submissions. Ehime University (Ehime) will further characterize the PfRipr5 recombinant protein with multiple analytical methods and dissect mode of action of the produced antibodies, focusing on the functional Growth Inhibition Assay (GIA). Sumitomo will be responsible for providing the SA-1 adjuvant, evaluating vaccine immunogenicity in animal studies, and overseeing the safety-toxicology study. iBET will be responsible for final process development, technology transfer to the CDMO and cGMP manufacturing oversight.

Others (including references if necessary)

World Health Organization (WHO). World Malaria Report 2022. Geneva: WHO; 2022.

Final Report

1. Project objective

The main objectives of the project were to:

 1.Establish a process for PfRipr5 production compliant with current Good Manufacturing Practice (cGMP)    

 2.Produce PfRipr5 for safety-toxicology study according to cGMP 

 3.Perform a safety-toxicology study to evaluate PfRipr5 formulated with the SA-1 adjuvant

 4.Prepare the dossier for Phase I/IIa clinical trial

2. Project design

The project was designed around four objectives defined above.

 In objective 1, the production and purification processes of PfRipr5 were fine-tuned.

 In objective 2, the established manufacturing process of PfRipr5 was transferred to the selected CDMO.

 In objective 3, PfRipr5 was formulated with SA-1 and evaluated in a GLP-compliant toxicology study.

 Finally, under objective 4, the clinical trial application dossier was to be prepared, along with a clinical development plan . To further support the dose level justification for the future clinical application, a dose range finding study was conducted in rats.

3. Results, lessons learned

Milestone 1: PfRipr5 production process implemented.

The manufacturing process of PfRipr5, including cell culture, purification steps, and analytical tools, was fine-tuned to make it suitable for cGMP, and applied for production in a 50 L bioreactor. A comparative analysis of PfRipr5 functional epitope binding to mAb 29B11 was performed using surface plasmon resonance across four lots of PfRipr5 (produced in this project and in T2018-151). All lots exhibited comparable nanomolar-level binding profiles.

Milestone 2: Production of PfRipr5 in accordance with cGMP completed.

Technology transfer to a cGMP facility of the processes for manufacturing master cell banks (MCBs), master virus seed stock (MVSS), and PfRipr5 was performed. Two insect MCBs (for generation of MVSS and PfRipr5 expression, respectively) and one baculovirus MVSS (for PfRipr5 expression induction) were produced under cGMP. These substrates were used to produce a non-GMP batch of PfRipr5 (engineering run) at 50 L scale. Quality control tests were completed, and a stability study of PfRipr5 was conducted. A preliminary compatibility study of PfRipr5/SA-1 was performed, assessing potency, purity, appearance, and particle size under conditions simulating clinical handling. Formulations were stored at 5 °C and room temperature for up to 24 hours. The results indicated that the PfRipr5 and SA-1 were stable across all tested conditions.

Milestone 3: CTA-enabling GLP toxicology study completed.

A GLP toxicology study was conducted in rats, where animals received a total of four doses of PfRipr5 /SA-1, control article (saline), or SA-1 alone. All animals survived until the scheduled necropsy. The PfRipr5/SA-1 vaccine was well-tolerated, and there was no unexpected finding.

Milestone 4: Documents for IND filing prepared    .

Due to unexpected results upon transfer of the PfRipr5 manufacturing process to cGMP facility, which required investigations and further process development work, CTA preparation was not initiated.  However, a clinical development plan was prepared. To justify the antigen and adjuvant dose levels for the first-in-human trial, a study was completed in rats immunised three times at four-week intervals with varying amounts of PfRipr5 and SA-1. Two weeks after the last immunisation, elicited antibodies were evaluated by ELISA and GIA (Growth Inhibition Assay). A minimum effective dose of PfRipr5 was identified and the adjuvanticity of SA-1 was shown.