Involvement of African patient populations in clinical trials on leprosy: a scoping review

Leprosy is a neglected tropical disease of public health importance. Although Africa carries a substantial share of the global leprosy burden, there is only limited evidence for African patients based on leprosy-related clinical trials. This scoping review aims to map existing evidence on the involvement of African patient populations in leprosy-related clinical treatment, prophylaxis and vaccine trials.

A scoping review was performed in 2023 by two independent reviewers following the PRISMA guideline. The electronic databases PubMed and Infolep, and clinical trial registries (Cochrane CENTRAL, WHO International Clinical Trials Registry Platform) were systematically searched for past and ongoing clinical trials on leprosy with recruitment in Africa up to 31 December 2022. 16 trials were registered on the WHO platform, but none had published results. Predefined data points were extracted, and study quality was assessed using Cochrane's RoB2 and ROBINS-I tools. The review is registered in PROSPERO.

Out of 198 publications, 22 were eligible for extraction, representing 18 clinical trials. The majority of trials were conducted in Malawi, Ethiopia and Uganda. 12 trials focused on treatment, 2 on vaccines, 3 on treatment reactions and 1 on prophylaxis. 10 clinical trials were randomized, 14 were controlled and 6 trials were blinded. One of these trials was pseudo-randomized and, therefore, not considered as randomized. Dapsone was the most frequently studied drug. 15 (83%) of all identified studies were conducted before the year 2000 having one study that published one paper before 2000 and one after 2000. 11 studies were assessed with the RoB2 tool and 8 (73%) showed high risk of bias. One study with two publications showed one serious and one medium risk of bias. Among 7 studies assessed with the ROBINS-I tool, 2 (29%) showed a serious risk of bias.

This scoping review demonstrates the substantial under-representation of the African patient population in leprosy clinical trials and highlights the low volume and a decrease in clinical trial conduct since the year 2000. To address this imbalance and improve the relevance of trial outcomes, there is a critical need to engage local stakeholders and build research capacities in Africa. These efforts will be essential for more inclusive and effective leprosy interventions.