NEW: AS-AQ Post-Treatment Prophylaxis Study Group

The burden of disease caused by Plasmodium falciparum malaria is considerable. Estimated to kill approximately 627,000 people each year, it is one of the leading causes of child mortality. People living in moderate to highly endemic areas frequently become re-infected very quickly after treatment. Some drugs, however, protect the patient for a prolonged time - known as chemoprophylaxis. This provides individual-level protection from reinfection and also reduces the spread of malaria within the community, potentially reducing overall malaria disease in endemic regions.

Artesunate-amodiaquine (AS-AQ) is currently the second most widely used antimalarial treatment after artemether-lumefantrine (AL). In recent years, researchers have demonstrated a potential post-treatment prophylactic effect of the amodiaquine component of AS-AQ. It is believed that AS-AQ could protect patients for prolonged periods, reducing malaria morbidity and transmission, but the size of this potential prophylactic effect is not well understood.

To answer this question a new study group, led by researchers at the MRC Study Centre for Outbreak Analysis and Modelling at Imperial College London, are utilising data from WWARN’s pooled drug-efficacy trials to estimate the duration of chemoprophylaxis after treatment, comparing the drugs AS-AQ and AL.

Azra Ghani, Professor at Imperial College, London, one of the leaders of the Study Group, highlights: “At present there is very little evidence to inform the choice of first-line therapy in different countries. We hope that our modelling results can contribute to the evidence base for treatment guidelines both at an international level and for National Malaria Control Programs.”

How can we improve our understanding of malaria post-treatment prophylaxis and treatment?

The Imperial-led Study Group has developed a statistical model that estimates the duration of patient protection using the time to re-infection during the 42 days after initial treatment. This will be combined with estimates of malaria prevalence made by the Malaria Atlas Project (MAP) to estimate the potential impact of switching first-line therapy.

In particular, the group is interested in how patient age, weight, and the dosage level per kg weight, can affect the duration of disease protection with AS-AQ. These are important factors that can potentially influence the way in which the drug interacts with the patient’s body, from when it is first administered to when it leaves the body (pharmacokinetics).

Once the Study Group has established the duration of post-treatment prophylaxis provided by AS-AQ, they will apply an epidemiological simulation model to determine the likely public-health impact of switching to AS-AQ as a first-line drug in different countries. This approach will take into account the varying conditions across different settings in Africa, including transmission intensity and treatment coverage levels achieved by different national health systems.

This article was written by the AS-AQ Post-Treatment Prophylaxis Study Group led by Dr Michael Bretscher, Dr Lucy Okell, and Prof Azra Ghani from the MRC Center of Outbreak Analysis at Imperial College, London. To find out more, email malaria@imperial.ac.uk