A single-center, open-label study investigating the excretion balance, pharmacokinetics, metabolism, and absolute bioavailability of a single oral dose of [ 14 C]-labeled idasanutlin and an intravenous tracer dose of [ 13 C]-labeled idasanutlin in a single cohort of patients with solid tumors

Purpose Idasanutlin, a selective small-molecule MDM2 antagonist in phase 3 testing for refractory/relapsed AML, is a non-genotoxic p53 activator with oral administration. To determine the need to conduct dedicated trial(s) for organ impairment on pharmacokinetic (PK) exposure and/or drug–drug interactions, a single dose of [ 14 C]- and [ 13 C]-labeled idasanutlin was evaluated. Methods This study was an open-label, non-randomized, single-center trial of idasanutlin to investigate the excretion balance, pharmacokinetics, metabolism, and absolute bioavailability of a single oral dose of [ 14 C]-labeled idasanutlin and an IV tracer dose of [ 13 C]-labeled idasanutlin in a single cohort of patients with solid tumors. After completing cycle 1 assessments, patients could have participated in an optional treatment extension of idasanutlin. Clinical endpoints were PK, and safety/tolerability. Results Co-administration of an oral dose of idasanutlin with an IV tracer dose revealed low systemic CL, a moderate V d , and a moderate (40.1%) absolute bioavailability of idasanutlin. Idasanutlin and its major inactive metabolite, M4, were the major circulating moieties in plasma, and excretion of idasanutlin-associated radioactivity was primarily via the fecal route (91.5% of the dose), with negligible amounts recovered in urine, following oral administration. Conclusion The clinical implications of this study support the conclusion that renal impairment is unlikely to significantly impact exposure to idasanutlin and M4 metabolite, whereas a significant hepatic impairment may potentially alter exposure to the parent drug and/or metabolite(s). The potential for drug–drug interactions is low.