Introduction::Avacopan (Tavneos®) is approved as an oral adjunctive treatment at a dose of 30 mg twice daily with food for adult patients with severe active Granulomatosis with Polyangiitis (GPA) and Microscopic Polyangiitis (MPA) in combination with standard therapy including glucocorticoids.
Methods::In this Pharmacokinetic (PK) study, the absorption, metabolism, and excretion of avacopan were evaluated following a single 100 mg/400 μCi oral 14C-avacopan dose solution in six healthy male participants. The mass balance recovery, plasma concentrations, and metabolite profile in plasma, urine, and feces were determined.
Results::Fecal and renal excretion accounted for 77.2% and 9.5%, respectively, of the total administered ra-dioactivity, with none of the mono- or bis-oxidation metabolites present at greater than 7% of the total radio-active dose. In urine, intact avacopan was present at <1% of the radioactive dose. In feces, intact avacopan was present at 8.7%, which represented 6.7% of the total radioactive dose, suggesting at least 93.3% of the radioactive dose was absorbed. The predominant component in plasma was avacopan, which accounted for 18.0% of the dose. The major circulating metabolite, M1, a monohydroxylation metabolite with similar po-tency in C5a receptor inhibition as avacopan, accounted for 11.9% of the total radioactivity.
Discussion::The primary route of elimination of avacopan is phase I metabolism, followed by biliary excre-tion. CYP3A4 is the primary isozyme involved in the in vitro metabolism of avacopan and formation of metabolite M1.
Conclusion::Study results provide a definitive assessment of the absorption, elimination, and the nature of metabolism of avacopan in humans.