The PrEPVacc trial is the first to test whether a combination of pre-exposure prophylaxis and an experimental vaccine can prevent HIV infection.

Combining drugs and vaccines to prevent HIV infection

An effective HIV vaccine is likely to be key to controlling the HIV epidemic. Unfortunately, HIV is very difficult to target with vaccines and past trials have had limited success. However, the RV144 trial in Thailand did find that a DNA vaccine ‘prime’ followed by a protein vaccine ‘boost’ appeared to offer modest levels of protection.

Nevertheless, more innovative approaches may be needed. One possibility is pre-exposure prophylaxis (PrEP), in which high-risk populations receive antiretroviral dugs to prevent HIV infection.

The challenge

The PrEPVacc trial is combining these two approaches to HIV prevention in a large-scale phase II trial. It will assess the impact of two experimental HIV vaccine regimens, already tested and shown to be safe in people, when used alongside antiretroviral-based PrEP. The vaccine regimens both combine DNA-based and protein-based elements, as used in the RV144 trial.

The trial will be carried out in high-risk populations in four sub-Saharan African countries. It also includes an innovative design feature: PrEPVacc will be an ‘adaptive’ trial, so that combinations can be halted mid-trial if they are turning out to be ineffective – the first time this approach has been adopted in an HIV vaccine trial.

The project

PrEPVacc will generate the first evidence of the ability of vaccine plus PrEP combinations to prevent HIV infections – information that would have major public health importance. It will also provide key data on the ability of the experimental vaccines to stimulate protective immune responses, and the likely success of DNA plus protein prime–boost vaccine strategies. Data on the nature of the immune responses triggered by the vaccines may also reveal which are key to prevention of HIV infection.

Impact


crucial in

widening African

children’s access

to antiretrovirals

Bringing antiretroviral drugs to children

The CHAPAS trials have ensured that many more children with HIV have benefited
from life-saving antiretrovirals.

EDCTP portfolio: HIV & HIV-associated infections

The challenge

An effective HIV vaccine is likely to be key to controlling the HIV epidemic. Unfortunately, HIV is very difficult to target with vaccines and past trials have had limited success. However, the RV144 trial in Thailand did find that a DNA vaccine ‘prime’ followed by a protein vaccine ‘boost’ appeared to offer modest levels of protection.

Nevertheless, more innovative approaches may be needed. One possibility is pre-exposure prophylaxis (PrEP), in which high-risk populations receive antiretroviral dugs to prevent HIV infection.

The PrEPVacc trial is combining these two approaches to HIV prevention in a large-scale phase II trial. It will assess the impact of two experimental HIV vaccine regimens, already tested and shown to be safe in people, when used alongside antiretroviral-based PrEP. The vaccine regimens both combine DNA-based and protein-based elements, as used in the RV144 trial.

The trial will be carried out in high-risk populations in four sub-Saharan African countries. It also includes an innovative design feature: PrEPVacc will be an ‘adaptive’ trial, so that combinations can be halted mid-trial if they are turning out to be ineffective – the first time this approach has been adopted in an HIV vaccine trial.

The project

The later CHAPAS-3 trial compared the efficacy and safety of three fixed-dose combinations including two without stavudine (found to have some long-term side effects in adults, leading to a recommendation that its use be discontinued in children). The trial the first of its kind in Africa studied nearly 500 children at four sites in two African countries.

PrEPVacc will generate the first evidence of the ability of vaccine plus PrEP combinations to prevent HIV infections – information that would have major public health importance. It will also provide key data on the ability of the experimental vaccines to stimulate protective immune responses, and the likely success of DNA plus protein prime–boost vaccine strategies. Data on the nature of the immune responses triggered by the vaccines may also reveal which are key to prevention of HIV infection.

ratios forfixed-dose combinations and on appropriatedosage according to weight. 

The CHAPAS-3 trial confirmed the effectiveness of fixed-dose combinations, providing further impetus to the rollout of antiretrovirals to children. Its evidence on abacavir informed the WHO recommendation of abacavir-containing combinations for first-line therapy in children. Trial data have also been used to support applications for regulatory approval for new scored efavirenz tablets.

Impact

Projects: CAPRISA 018 study

Project lead: Professor Salim Abdool Karim, Centre for the AIDS Programme of Research in South Africa, South Africa

Countries involvedFrance, The Netherlands, South Africa

Target population(s): Women

Year funded: 2017

EDCTP funding: €9.8 M

Total project funding: €11.4M plus donation of study drugs

About us

The European & Developing Countries Clinical Trials Partnership (EDCTP) is a public–public partnership between 14 European and 16 African countries, supported by the European Union. EDCTP’s vision is to reduce the individual, social and economic burden of poverty-related infectious diseases by affecting sub-Saharan Africa. EDCTP’s mission is to accelerate the development of new or improved medicinal products for the identification, treatment and prevention of infectious diseases, including emerging and re-emerging diseases, through pre- and postregistration clinical studies, with emphasis on phase II and III clinical trials. Our approach integrates conduct of research with development of African clinical research capacity and networking. The second EDCTP programme is implemented by the EDCTP Association supported under Horizon 2020, the European Union’s Framework Programme for Research and Innovation.

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