Absorption, single-dose and steady-state metabolism, excretion, and pharmacokinetics of adagrasib, a KRAS^G12C inhibitor

Objective: This study investigated absorption, metabolism, and excretion of adagrasib after a single oral 600 mg dose (1 µCi [¹⁴C]-adagrasib) in 7 healthy subjects and compared the metabolite profile to the profile at steady-state in 4 patients dosed at 600 mg twice daily.

Methods: Plasma, urine, and feces were collected post [¹⁴C]-adagrasib administration and total radioactivity and pooled sample metabolite profiles were determined. Adagrasib pharmacokinetics were determined in plasma and urine. The steady-state plasma metabolite profile was examined in patients and in vitro studies were performed to understand adagrasib's potential to inhibit CYP enzymes and identify CYPs involved in its metabolism.

Results: The total mean recovery of the administered radioactivity was 79.2%, with 74.7% and 4.49% of total radioactivity recovered from feces and urine, respectively. Only 1.8% of the dose was excreted in urine as unchanged adagrasib, indicating negligible renal clearance. Adagrasib, M55a, M11, and M68 were major plasma components accounting for 38.3%, 13.6%, 13.4%, and 11.0% of the total plasma radioactivity exposure, respectively. Metabolite M55a was not detected in plasma at steady state where only M68 (24%) and M11 (17.1%) were abundant. In vitro data showed that CYP3A4 (72%) and CYP2C8 (28%) are main contributors to metabolism and adagrasib is a time-dependent inhibitor of CYP3A4.

Conclusion: Elimination of adagrasib is mainly by fecal excretion. Adagrasibs altered metabolite profile at steady state is likely due to CYP3A4 autoinhibition. The abundant steady-state plasma metabolites, M68 and M11, are not human specific and do not contribute significantly to the pharmacological activity of adagrasib.