OA-652 Safety and tolerability of favipiravir for the treatment of Lassa fever: a randomized controlled open label phase II clinical trial

BackgroundLassa fever (LF) is a severe re-emerging infectious disease caused by the Lassa virus (LV). LF is a priority disease on the World Health Organization’s R&D blueprint and affects a large number of countries in West Africa, with Nigeria carrying the highest case burden in the world. Current treatment options are limited to supportive care and the antiviral drug ribavirin. However, evidence for the efficacy of ribavirin in LF is poor. A recent study showed that in vivo plasma concentrations do not suffice to exert a relevant antiviral effect. New drugs for LF treatment are therefore urgently needed but no therapeutic trials have been conducted for this indication in the past decades. Favipiravir is a broad-spectrum antiviral registered for pandemic influenza that has also been clinically evaluated for other viral infections. It shows potent activity against LV in pre-clinical studies. To evaluate the safety and tolerability of favipiravir as repurposed drug in the treatment of LF, a phase II clinical trial was conducted. MethodsLF patients were recruited at the Irrua Specialist Teaching Hospital and the Federal Medical Centre of Owo in Nigeria, which are the worldwide largest LF treatment centres. Blood sampling for virological, serological and immunological analyses, hematology and biochemistry as well as clinical assessments were done on days 1, 2, and then every other day until the end of the study.ResultsIn total, 40 LF patients were included in the trial between 2021 and 2022. Results on cure rates, safety and tolerability of this first GCP compliant phase II clinical trial will be presented to provide first insights into this new treatment option for LF.