Safety and short-term efficacy of a single dose of 2 mg moxidectin in Loa loa infected individuals: a double-blind, randomized ivermectin-controlled trial with ascending microfilarial densities

In 2018, the US FDA approved the macrocylic lactone moxidectin (MOX) at 8 mg dosage for onchocerciasis treatment in individuals aged ≥12 year-old. Severe adverse reactions have occurred after ivermectin (IVM), also a macrocyclic lactone, in individuals with high Loa loa microfilaria density (MFD). This study compared the safety and efficacy of a 2 mg MOX dose and the standard 150 µg/kg IVM dose in individuals with low L loa MFD. A double-blind randomized, ivermectin-controlled, trial of a 2 mg moxidectin dose was conducted in Cameroon between May and July 2022. It enrolled 72 adult men with L. loa MFD between 5-1000 microfilaria/mL. Outcomes were occurrence of adverse events (AE) and L loa MFD reduction rate during the first month off treatment. No serious or severe AEs occurred among the 36 MOX or the 36 IVM treated individuals. Forty-nine AEs occurred in the MOX arm vs 59 AEs in the IVM arm. Grade 2 AE incidence was higher among IVM than MOX treated participants (38.5% and 14.3%, respectively, p = 0.043). Median MFD reduction rates were significantly higher after IVM than MOX at day 3 (D3) (70.2% vs 48.5%), D7 (76.4% vs 50.0%) and D30 (79.8% vs 48.1%). A single 2 mg MOX dose is as safe as 150 µg/kg IVM in patients with low L loa MFD. Further studies with higher moxidectin doses and in patients with higher MFD are warranted.