Final Report Summary - REDMAL (Clinical development of a Pfs48/45-based malaria transmission blocking vaccine)
Executive Summary:
Malaria vaccines are needed to reduce the unacceptably high burden of malaria-related morbidity and mortality that occurs in particular in the lowest income countries. The objective of malaria vaccines is to induce human immune responses that interrupt progression of the malaria parasite life cycle. Sexual stage parasites are able to infect blood-feeding mosquitoes which are responsible for spread of the malaria parasite in the population. Transmission-blocking malaria vaccines (TBMV) specifically aim at an arrest of sexual stage development thereby preventing the generation of infectious mosquitoes. TBMVs are considered to be indispensible for sustained control, elimination and eventually eradication. Pfs48/45 is the most advanced EU-developed malaria TB vaccine candidate. PF10C is a subunit of Pfs48/45 that has been produced as R0-PF10C.
The first REDMAL objective was to manufacture R0-PF10C according to standards of current Good Manufacturing Practise (cGMP).
Correctly folded R0-PF10C was able to induce a TB antibody response in 100% of immunized mice. The optimal adjuvant-R0-PF10C combination has been determined. Proper protein folding of the Pfs48/45 fragment i.e. conform the folding in the membrane of the sexual stage parasite, turned out to be essential for recognition and functional activity of the induced antibodies. We developed a protocol for the production and downstream purification of R0-PF10C according to cGMP standards. Although the presence of improperly folded R0-PF10C did not to influence the potency, we aimed for a final product containing > 50% correctly folded R0-PF10C. The first batch of R0-PF10C produced according to cGMP protocols contained 60% correctly folded R0-PF10C. Preliminary immunization studies demonstrated that cGMP produced 60% correctly folded R0-PF10C is able to elicit transmission blocking activity as determined by Standard Membrane Feeding Assay, the gold standard for measuring transmission from humans to mosquitoes.
The second objective of REDMAL is to prepare for clinical TBMV testing in Africa. A Phase II TBMV trial in the more distant future requires considerable preparation not the least because such trial has never taken place in history requiring a specific design. Critical parameters under conditions of natural transmission need to be known at baseline. In collaboration with local investigators base-line data were collected in possible field sites of low-moderate endemicity in Tanzania (KCMC), Ghana (Noguchi Memorial Inst.) and Burkina Faso (CNRFP). This included gametocyte prevalence, transmission patterns and logistical accessibility of sites. Antibodies to R0-PF10C showed a similar pattern of reactivity as asexual stage antibody responses but much lower increasing with age and transmission intensity. There was a strong positive association between naturally acquired antibody responses to PF10C and naturally acquired functional transmission blocking activity.
In addition, the set up of a robust statistical model for the impact of TBMV on transmission intensity was accelerated by the design of a conceptual framework with clear measurable key endpoints. The REDMAL mathematical modeling activities have resulted in considerable progress towards future model-based design of clinical and epidemiological trials with TBMV.
The data generated by the REDMAL project as a whole more specifically on clinical vaccine development and clinical testing, make a significant contribution to society’s ability to manage, control and eventually eradicate malaria.
Project Context and Objectives:
Malaria vaccines are needed to reduce the unacceptably high burden of disease and death in particular in the lowest income countries. Malaria vaccines aim at interruption of the life cycle of the parasite Plasmodium falciparum by induced immune responses in humans. Transmission-blocking malaria vaccines (TBMV) specifically aim at an arrest of sexual stage development preventing the generation of infectious mosquitoes, responsible for spread of the malaria parasite in the population. TBMVs are considered the most effective tools for this purpose, and considered to be indispensible for sustained control, elimination and eventually eradication. Pfs48/45 is the most advanced EU-developed malaria TB vaccine candidate. PF10C is a subunit of Pfs48/45 that has been produced as R0-PF10C. Immunization with 100% properly folded R0-PF10C induced transmission-blocking activity in 100% of immunized mice.
The objectives of REDMAL are; 1) Manufacture R0-PF10C at cGMP grade and 2) Prepare for clinical trials with R0-PF10C in Africa.
Workplan: R0-PF10C production will be optimized and up-scaled for release of clinical grade batches for human trials. To prepare for clinical testing to Africa, preparation for Phase II will be initiated. A Phase II trial of a malaria TB vaccine will require a specific design. Important transmission parameters will be collected and introduced in a mathematical model to study the possible impact on transmission in the selected study area.
Project Results:
The first REDMAL objective is to manufacture R0-PF10C at cGMP grade.
The capacity of R0-PF10C to induce a TB antibody response in rodents has been assessed and immunization with 100% properly folded R0-PF10C induced transmission-blocking activity in 100% of immunized mice. Additionally, the optimal adjuvant-R0-PF10C combination has been determined.
Although the presence of improperly folded R0-PF10C does not influence the potency of correctly folded R0-PF10C, the final product should contain > 50% correctly folded R0-PF10C. At lab scale, 60-65% correctly folded R0.10C can be obtained routinely. The first batch of R0-PF10C produced according to cGMP protocols contained 60% correctly folded R0-PF10C. With minor adjustments in the protocol the percentage correctly folded R0-PF10C may further increase to 65-70%. Preliminary immunization studies demonstrated that cGMP produced 60% correctly folded R0-PF10C is able to elicit transmission blocking activity as determined by SMFA assay.
The second objective of REDMAL is to prepare for clinical TBMV testing in Africa; preparation for Phase Ib and II trials have been initiated as parallel activities. Clinical trial capacity has been created by the construction of a clinical trial institute (KCRI) by partner KCMC in Tanzania. A Phase II TBMV trial in the more distant future requires considerable preparation not the least because such trial has never taken place in history requiring a specific design. Many important parameters under conditions of natural transmission need to be known as baseline. Development of standard operating protocols (SOP) and acquisition of base-line data has been completed in 3 possible field sites under coordination of partners LSTHM and RUNMC. The criteria for initial site characterization included the level of endemicity, gametocyte prevalence, transmission patterns and logistical accessibility of sites. In collaboration with the local investigators in Tanzania (partner KCMC), Ghana (Noguchi Memorial Inst.) and Burkina Faso (CNRFP), an area of reported low-moderate endemicity (<40% parasite prevalence in the general population) was selected in each of the three countries: Bondo, Tanzania; Ouahigouya, Burkina Faso and Asutsuare, Ghana. In each of these areas, 1-2 schools were selected for an initial survey and data collection is completed.
Antibodies to R0-PF10C showed a similar pattern of reactivity as asexual stage antibody responses; they increased with increasing age and with transmission intensity. They were, however, present at much lower levels than the asexual antibody responses and also those to the sexual stage antigen Pfs230. There was a strong positive association between naturally acquired antibody responses to PF10C and naturally acquired functional transmission blocking activity.
The set up of a robust statistical model for the impact of TBMV on transmission intensity was accelerated by the design of a conceptual framework with clear measurable key endpoints. The relative informativeness and precision of the different endpoints has been parametrized by a thorough review of the available literature and a simulated comparison of the ability of different metrics to capture changes in malaria transmission. The REDMAL mathematical modeling activities have thereby resulted in considerable progress towards future model-based design of clinical and epidemiological trials with TBMV.
Potential Impact:
Although significant progress has been made in malaria control during the last decade, malaria remains a serious problem according to the World Health Organization, particularly in sub-Saharan Africa, where approximately 90% of clinical cases occur. Malaria, either alone or in combination with other diseases, is estimated to kill almost 500 000 people worldwide each year, and over 2400 million remain at risk. Malaria has a continuing impact on the EU, both directly and indirectly. Direct impact is mainly through imported malaria cases, which comprise both European travelers exposed to infection in endemic countries, and immigrants and visitors from the (sub)-tropics. Indirect impacts include the significant malaria-related suppression of socio-economic advancement preventing countries in sub-Saharan Africa from reaching their economic potential. Development in Africa would have far-reaching benefits for Europe in trade, supply of mineral and agricultural products, and in reduction of sometimes catastrophic movements of people within Africa and into Europe. This has been a long-term drain on the humanitarian resources of many EU member states.
A recent downward trend in malaria has been observed in certain notably low endemic areas as a result from the WHO’s Global Malaria Control Strategy based on i) early diagnosis and prompt effective treatment using ACT (artemisinin-based combination therapy) ii) implementation of selective and sustainable preventive measures, including insecticide impregnated bed nets and presumptive treatment in certain risk groups iii) access to clinical care.
There is now emerging broad consensus that control and certainly elimination or even eradication of malaria will need control measures that target the transmission reservoir. For efficient and sustainable elimination/eradication, availability of a malaria vaccine including a Malaria Transmission Blocking Vaccine (TBMV) is considered to be indispensible, but no vaccine is available as yet. Clinical development of a TBMV as proposed in REDMAL will be an important additional tool to be potentially integrated in this policy.
Exploitable foreground
R0-PF10C is currently one of the most promising transmission blocking vaccine candidates in development. Further research will require a (proof of concept) phase 1 clinical trial at Radboudumc, the Netherlands, followed by a Phase Ib safety and immunogenicity trial in Africa and a Phase IIb trial in area with low transmission in Africa. The target population in an endemic area will be initially healthy individuals of all age groups. For coverage of special groups that may also contribute to transmission e.g. pregnant women additional safety studies will need to be conducted. Once efficacy (reduced transmission) has been shown the product will be subsequently evaluated in a variety of transmission settings. Once accepted and recommended by WHO standards, the product will be registered by competent authorities and made available to populations of malaria endemic countries. Special mechanisms will need to be explored with specialized organizations to ensure access by financially resource-poor countries. A transmission blocking vaccine can confer immense public benefit and likely be part of a larger package of malaria control measure. As stand-alone this product can probably be effective in very low transmission conditions or at the last step of elimination. In higher transmission conditions, the product will be combined or incorporated in other malaria vaccine platforms. It is important to note that elimination needs to be complete and sustainable to avoid a situation of unstable malaria and increased susceptibility. Therefore, the foreground generated by the REDMAL project as a whole can make a significant contribution to society’s ability to manage, control and eventually eradicate malaria.
Plan for the use and dissemination of foreground
REDMAL partners are participating in a number of international policy and research initiatives on malaria transmission and eradication. Regular conference calls and meetings between partners will be continued after completion of the REDMAL project to discuss dissemination of REDMAL project results and foreground. Memberships in national and international scientific societies provide additional means to disseminate results to interested individuals and groups. The Pfs48/45 R0-PF10C product generated by the REDMAL program, is one of the very few leading transmission blocking vaccine candidates and this outcome ensures permanent contact with the scientific community. The participation of the sub-Saharan partner KCMC will allow the Consortium to enlarge the dissemination of the results to the African scientific community.
The results of REDMAL will be mainly disseminated by: a) publication of research articles in specialized and high-impact journals, b) press releases c) publication in general press and d) scientific lectures at (inter)national conferences. In addition, the results of the project, constituting its foreground, will be described in review articles and book chapters, to which most members of the team are regularly invited to contribute. We aim for publication in open access journals to ensure that our results become freely available for the research community in developing countries.
In addition to scientific publications, we will disseminate our results through popular science presentations and reviews that are part of our usual activity. Associated dissemination activities will include participation in workshops and programs of vaccine initiatives (focused on malaria endemic countries). This will make it possible to rapidly exploit the results of the project in the regions in most need.
The Media Relation Officers of the partners have experience making results known to general public through the media and we will duly liaise with them to ensure that our results reach the public e.g. local and national writing press, radio and television.
Dissemination will also occur through the websites of the partners, public sections with available scientific data (as allowed by copyright laws), summaries of the main results (written in plain language accessible to the non-specialists) and links to and from relevant websites will be set-up when not yet available. Appropriate Web linking and indexing is a potentially powerful way of achieving dissemination. In each case of scientific dissemination, the support by the EU will be acknowledged.
List of Websites:
www.REDMAL.eu
Malaria vaccines are needed to reduce the unacceptably high burden of malaria-related morbidity and mortality that occurs in particular in the lowest income countries. The objective of malaria vaccines is to induce human immune responses that interrupt progression of the malaria parasite life cycle. Sexual stage parasites are able to infect blood-feeding mosquitoes which are responsible for spread of the malaria parasite in the population. Transmission-blocking malaria vaccines (TBMV) specifically aim at an arrest of sexual stage development thereby preventing the generation of infectious mosquitoes. TBMVs are considered to be indispensible for sustained control, elimination and eventually eradication. Pfs48/45 is the most advanced EU-developed malaria TB vaccine candidate. PF10C is a subunit of Pfs48/45 that has been produced as R0-PF10C.
The first REDMAL objective was to manufacture R0-PF10C according to standards of current Good Manufacturing Practise (cGMP).
Correctly folded R0-PF10C was able to induce a TB antibody response in 100% of immunized mice. The optimal adjuvant-R0-PF10C combination has been determined. Proper protein folding of the Pfs48/45 fragment i.e. conform the folding in the membrane of the sexual stage parasite, turned out to be essential for recognition and functional activity of the induced antibodies. We developed a protocol for the production and downstream purification of R0-PF10C according to cGMP standards. Although the presence of improperly folded R0-PF10C did not to influence the potency, we aimed for a final product containing > 50% correctly folded R0-PF10C. The first batch of R0-PF10C produced according to cGMP protocols contained 60% correctly folded R0-PF10C. Preliminary immunization studies demonstrated that cGMP produced 60% correctly folded R0-PF10C is able to elicit transmission blocking activity as determined by Standard Membrane Feeding Assay, the gold standard for measuring transmission from humans to mosquitoes.
The second objective of REDMAL is to prepare for clinical TBMV testing in Africa. A Phase II TBMV trial in the more distant future requires considerable preparation not the least because such trial has never taken place in history requiring a specific design. Critical parameters under conditions of natural transmission need to be known at baseline. In collaboration with local investigators base-line data were collected in possible field sites of low-moderate endemicity in Tanzania (KCMC), Ghana (Noguchi Memorial Inst.) and Burkina Faso (CNRFP). This included gametocyte prevalence, transmission patterns and logistical accessibility of sites. Antibodies to R0-PF10C showed a similar pattern of reactivity as asexual stage antibody responses but much lower increasing with age and transmission intensity. There was a strong positive association between naturally acquired antibody responses to PF10C and naturally acquired functional transmission blocking activity.
In addition, the set up of a robust statistical model for the impact of TBMV on transmission intensity was accelerated by the design of a conceptual framework with clear measurable key endpoints. The REDMAL mathematical modeling activities have resulted in considerable progress towards future model-based design of clinical and epidemiological trials with TBMV.
The data generated by the REDMAL project as a whole more specifically on clinical vaccine development and clinical testing, make a significant contribution to society’s ability to manage, control and eventually eradicate malaria.
Project Context and Objectives:
Malaria vaccines are needed to reduce the unacceptably high burden of disease and death in particular in the lowest income countries. Malaria vaccines aim at interruption of the life cycle of the parasite Plasmodium falciparum by induced immune responses in humans. Transmission-blocking malaria vaccines (TBMV) specifically aim at an arrest of sexual stage development preventing the generation of infectious mosquitoes, responsible for spread of the malaria parasite in the population. TBMVs are considered the most effective tools for this purpose, and considered to be indispensible for sustained control, elimination and eventually eradication. Pfs48/45 is the most advanced EU-developed malaria TB vaccine candidate. PF10C is a subunit of Pfs48/45 that has been produced as R0-PF10C. Immunization with 100% properly folded R0-PF10C induced transmission-blocking activity in 100% of immunized mice.
The objectives of REDMAL are; 1) Manufacture R0-PF10C at cGMP grade and 2) Prepare for clinical trials with R0-PF10C in Africa.
Workplan: R0-PF10C production will be optimized and up-scaled for release of clinical grade batches for human trials. To prepare for clinical testing to Africa, preparation for Phase II will be initiated. A Phase II trial of a malaria TB vaccine will require a specific design. Important transmission parameters will be collected and introduced in a mathematical model to study the possible impact on transmission in the selected study area.
Project Results:
The first REDMAL objective is to manufacture R0-PF10C at cGMP grade.
The capacity of R0-PF10C to induce a TB antibody response in rodents has been assessed and immunization with 100% properly folded R0-PF10C induced transmission-blocking activity in 100% of immunized mice. Additionally, the optimal adjuvant-R0-PF10C combination has been determined.
Although the presence of improperly folded R0-PF10C does not influence the potency of correctly folded R0-PF10C, the final product should contain > 50% correctly folded R0-PF10C. At lab scale, 60-65% correctly folded R0.10C can be obtained routinely. The first batch of R0-PF10C produced according to cGMP protocols contained 60% correctly folded R0-PF10C. With minor adjustments in the protocol the percentage correctly folded R0-PF10C may further increase to 65-70%. Preliminary immunization studies demonstrated that cGMP produced 60% correctly folded R0-PF10C is able to elicit transmission blocking activity as determined by SMFA assay.
The second objective of REDMAL is to prepare for clinical TBMV testing in Africa; preparation for Phase Ib and II trials have been initiated as parallel activities. Clinical trial capacity has been created by the construction of a clinical trial institute (KCRI) by partner KCMC in Tanzania. A Phase II TBMV trial in the more distant future requires considerable preparation not the least because such trial has never taken place in history requiring a specific design. Many important parameters under conditions of natural transmission need to be known as baseline. Development of standard operating protocols (SOP) and acquisition of base-line data has been completed in 3 possible field sites under coordination of partners LSTHM and RUNMC. The criteria for initial site characterization included the level of endemicity, gametocyte prevalence, transmission patterns and logistical accessibility of sites. In collaboration with the local investigators in Tanzania (partner KCMC), Ghana (Noguchi Memorial Inst.) and Burkina Faso (CNRFP), an area of reported low-moderate endemicity (<40% parasite prevalence in the general population) was selected in each of the three countries: Bondo, Tanzania; Ouahigouya, Burkina Faso and Asutsuare, Ghana. In each of these areas, 1-2 schools were selected for an initial survey and data collection is completed.
Antibodies to R0-PF10C showed a similar pattern of reactivity as asexual stage antibody responses; they increased with increasing age and with transmission intensity. They were, however, present at much lower levels than the asexual antibody responses and also those to the sexual stage antigen Pfs230. There was a strong positive association between naturally acquired antibody responses to PF10C and naturally acquired functional transmission blocking activity.
The set up of a robust statistical model for the impact of TBMV on transmission intensity was accelerated by the design of a conceptual framework with clear measurable key endpoints. The relative informativeness and precision of the different endpoints has been parametrized by a thorough review of the available literature and a simulated comparison of the ability of different metrics to capture changes in malaria transmission. The REDMAL mathematical modeling activities have thereby resulted in considerable progress towards future model-based design of clinical and epidemiological trials with TBMV.
Potential Impact:
Although significant progress has been made in malaria control during the last decade, malaria remains a serious problem according to the World Health Organization, particularly in sub-Saharan Africa, where approximately 90% of clinical cases occur. Malaria, either alone or in combination with other diseases, is estimated to kill almost 500 000 people worldwide each year, and over 2400 million remain at risk. Malaria has a continuing impact on the EU, both directly and indirectly. Direct impact is mainly through imported malaria cases, which comprise both European travelers exposed to infection in endemic countries, and immigrants and visitors from the (sub)-tropics. Indirect impacts include the significant malaria-related suppression of socio-economic advancement preventing countries in sub-Saharan Africa from reaching their economic potential. Development in Africa would have far-reaching benefits for Europe in trade, supply of mineral and agricultural products, and in reduction of sometimes catastrophic movements of people within Africa and into Europe. This has been a long-term drain on the humanitarian resources of many EU member states.
A recent downward trend in malaria has been observed in certain notably low endemic areas as a result from the WHO’s Global Malaria Control Strategy based on i) early diagnosis and prompt effective treatment using ACT (artemisinin-based combination therapy) ii) implementation of selective and sustainable preventive measures, including insecticide impregnated bed nets and presumptive treatment in certain risk groups iii) access to clinical care.
There is now emerging broad consensus that control and certainly elimination or even eradication of malaria will need control measures that target the transmission reservoir. For efficient and sustainable elimination/eradication, availability of a malaria vaccine including a Malaria Transmission Blocking Vaccine (TBMV) is considered to be indispensible, but no vaccine is available as yet. Clinical development of a TBMV as proposed in REDMAL will be an important additional tool to be potentially integrated in this policy.
Exploitable foreground
R0-PF10C is currently one of the most promising transmission blocking vaccine candidates in development. Further research will require a (proof of concept) phase 1 clinical trial at Radboudumc, the Netherlands, followed by a Phase Ib safety and immunogenicity trial in Africa and a Phase IIb trial in area with low transmission in Africa. The target population in an endemic area will be initially healthy individuals of all age groups. For coverage of special groups that may also contribute to transmission e.g. pregnant women additional safety studies will need to be conducted. Once efficacy (reduced transmission) has been shown the product will be subsequently evaluated in a variety of transmission settings. Once accepted and recommended by WHO standards, the product will be registered by competent authorities and made available to populations of malaria endemic countries. Special mechanisms will need to be explored with specialized organizations to ensure access by financially resource-poor countries. A transmission blocking vaccine can confer immense public benefit and likely be part of a larger package of malaria control measure. As stand-alone this product can probably be effective in very low transmission conditions or at the last step of elimination. In higher transmission conditions, the product will be combined or incorporated in other malaria vaccine platforms. It is important to note that elimination needs to be complete and sustainable to avoid a situation of unstable malaria and increased susceptibility. Therefore, the foreground generated by the REDMAL project as a whole can make a significant contribution to society’s ability to manage, control and eventually eradicate malaria.
Plan for the use and dissemination of foreground
REDMAL partners are participating in a number of international policy and research initiatives on malaria transmission and eradication. Regular conference calls and meetings between partners will be continued after completion of the REDMAL project to discuss dissemination of REDMAL project results and foreground. Memberships in national and international scientific societies provide additional means to disseminate results to interested individuals and groups. The Pfs48/45 R0-PF10C product generated by the REDMAL program, is one of the very few leading transmission blocking vaccine candidates and this outcome ensures permanent contact with the scientific community. The participation of the sub-Saharan partner KCMC will allow the Consortium to enlarge the dissemination of the results to the African scientific community.
The results of REDMAL will be mainly disseminated by: a) publication of research articles in specialized and high-impact journals, b) press releases c) publication in general press and d) scientific lectures at (inter)national conferences. In addition, the results of the project, constituting its foreground, will be described in review articles and book chapters, to which most members of the team are regularly invited to contribute. We aim for publication in open access journals to ensure that our results become freely available for the research community in developing countries.
In addition to scientific publications, we will disseminate our results through popular science presentations and reviews that are part of our usual activity. Associated dissemination activities will include participation in workshops and programs of vaccine initiatives (focused on malaria endemic countries). This will make it possible to rapidly exploit the results of the project in the regions in most need.
The Media Relation Officers of the partners have experience making results known to general public through the media and we will duly liaise with them to ensure that our results reach the public e.g. local and national writing press, radio and television.
Dissemination will also occur through the websites of the partners, public sections with available scientific data (as allowed by copyright laws), summaries of the main results (written in plain language accessible to the non-specialists) and links to and from relevant websites will be set-up when not yet available. Appropriate Web linking and indexing is a potentially powerful way of achieving dissemination. In each case of scientific dissemination, the support by the EU will be acknowledged.
List of Websites:
www.REDMAL.eu