The Schistosomiasis Clinical Trials Landscape: A Systematic Review of Antischistosomal Treatment Efficacy Studies and a Case for Sharing Individual Participant-Level Data (IPD)

Background: Schistosomiasis control mainly relies on preventive chemotherapy with praziquantel (PZQ) distributed through mass drug administration. With a target of 260 million treatments yearly, reliably assessing and monitoring efficacy is all-important. Recommendations for treatment and control of schistosomiasis are supported by systematic reviews and meta-analyses of aggregated data, which however also point to limitations due to heterogeneity in trial design, analyses and reporting. Some such limitations could be corrected through access to individual participant-level data (IPD), which facilitates standardised analyses. Methodology: A systematic literature review was conducted to identify antischistosomal drug efficacy studies performed since 2000; including electronic searches of the Cochrane Infectious Diseases Group specialised register and the Cochrane Library, PubMed, CENTRAL and Embase; complemented with a manual search for articles listed in past reviews. Antischistosomal treatment studies with assessment of outcome within 60 days post-treatment were eligible. Meta-data, i.e. study-level characteristics (Schistosoma species, number of patients, drug administered, country, etc.) and efficacy parameters were extracted from published documents to evaluate the scope of an individual-level data sharing platform. Principal findings: Out of 914 documents screened, 90 studies from 26 countries were included, enrolling 20,517 participants infected with Schistosoma spp. and treated with different PZQ regimens or other drugs. Methodologies varied in terms of diagnostic approaches (number of samples and test repeats), time of outcome assessment, and outcome measure (cure rate or egg reduction rate, as an arithmetic or geometric mean), making direct comparison of published data difficult. Conclusions: This review describes the landscape of schistosomiasis clinical research. The volume of data and the methodological and reporting heterogeneity identified all indicate that there is scope for an individual participant-level database, to allow for standardised analyses. Author Summary: Schistosomiasis is a parasitic disease prevalent in tropical climates, especially Africa. To control morbidity and eventually eliminate the disease, the World Health Organisation recommends that populations living in endemic areas be preventively treated with praziquantel. This means hundreds of million treatments over time, which calls for careful monitoring of drug efficacy. Meta-analyses of aggregated data from clinical trials support this policy, but conclusions are limited because studies use diverse methodologies, and detailed analyses (e.g. by age-groups) are not possible. Access to primary data generated by trials would strengthen the evidence and allow answering key questions, such as what the optimum paediatric dose is. This review assesses the number of trials conducted on antischistosomal drugs and their characteristics (where studies were conducted, in which population, what drug(s)/dose(s) were administered, and the methodologies applied), to determine the merit and scope of a common database of antischistosomal efficacy data.