A phase-2, randomized, multicenter, placebo-controlled, proof-of-concept trial of oral fexinidazole in adults with chronic indeterminate Chagas disease

BACKGROUND: Chagas disease (CD) has significant global health impact, but safe and effective treatments remain elusive. The nitroimidazole fexinidazole is a potential treatment.

METHODS: This double-blind, randomised, placebo-controlled, dose-finding, proof-of-concept study was conducted in Bolivia. Adults with serologically-confirmed chronic indeterminate CD and positive PCR were randomly assigned to one of six fexinidazole regimens (1200 or 1800 mg/day for 2, 4, or 8 weeks) or placebo. Target recruitment was 20 patients/arm. The primary endpoint was sustained parasitological clearance by serial negative qPCR from end of treatment (EOT) until 6 months follow-up in the intention-to-treat population (ITT). Follow-up was extended to 12 months.

RESULTS: Enrollment was interrupted after 4/47 patients presented with transient asymptomatic grade-3 and 4 neutropenia. Treatment of ongoing patients was stopped in all patients administered >2 weeks. A total of 40 patients received from 3 days to 8 weeks of treatment with fexinidazole. Delayed onset neutropenia (n = 8) and increased liver enzymes (n = 8) were found in fexinidazole patients, versus none in the placebo arm. In the ITT analysis, sustained parasitological clearance from EOT to 12 months follow-up varied between 66.7% ("1200mg-2week") and 100.0% ("1800mg-2week"). Rapid, sustained clearance of parasitemia was observed in all treated patients with available data, but not in any patients in the placebo group, at 12 months (p = 0.0056). Further exploratory exposure-response analysis suggested low dosages of fexinidazole may be safe and effective.

CONCLUSIONS: Further evaluation is needed to establish fexinidazole's minimum effective dosage and risk-benefit relationship. Results suggest potential for effective treatment regimens of <10 days.