Mass balance, pharmacokinetics, metabolism, and excretion of radiolabeled acoziborole, a potential novel treatment for human African trypanosomiasis, following single microtracer oral dose to humans

Acoziborole is an oxaborole 6-carboxamide active against <i>Trypanosoma brucei gambiense</i> and <i>rhodesiense</i>, the parasites responsible for human African trypanosomiasis. This open-label, phase I study in six healthy male participants evaluated the mass balance, pharmacokinetics, metabolism pathways, and excretion of a single oral 960 mg dose of [¹⁴C]-acoziborole. Blood, plasma, and feces were collected for 120 days and urine for 16 days. The excretion balance and systemic exposure of total circulating radioactivity were determined using accelerator mass spectrometry. Metabolism profiling was performed in pools of plasma, urine, and feces. Liquid chromatography coupled with tandem mass spectrometry quantified acoziborole and its metabolite SCYX-3109 in plasma and urine. By Day 60, 87.3% of the total radioactivity had been recovered (10.9% and 74.2% of the total dose in urine and in feces, respectively), with an excretion increment of <1% between Days 59 and 61. Mean ratios of total radioactivity indicated an equivalent distribution between blood cells and plasma. The concentration-time profiles of total radioactivity and acoziborole in plasma were similar. In plasma, acoziborole accounted for 95.1%, an oxidized form of acoziborole for 2.3% of the total radioactivity, while SCYX-3109 was not detected. Seven metabolites (oxidative deboronation, glucuronidation, and mono-oxidation) were detected in urine with individual abundances relative to the dose of 0.1-2.1%; unchanged acoziborole accounted for 0.6%. In feces, acoziborole, SCYX-3109, and two other oxidized or deboronated forms of acoziborole represented 33.6%, 12.3%, and 2.3% of the dose, respectively. Acoziborole showed good absorption, limited metabolism, minimal urinary elimination, and predominant but slow biliary-fecal elimination.