Nonclinical Safety Profile of Sotorasib, a KRASG12C-Specific Covalent Inhibitor for the Treatment of KRAS p.G12C-Mutated Cancer

Validated LC-MS/MS method for simultaneous quantification of KRASG12C inhibitor sotorasib and its major circulating metabolite (M24) in mouse matrices and its application in a mouse pharmacokinetic study

We have successfully developed and validated a bioanalytical assay using liquid chromatography tandem mass spectrometry to simultaneously quantify the first approved KRASG12C inhibitor sotorasib and its major circulating metabolite (M24) in various mouse matrices. M24 was synthesized in-house via low-pH hydrolysis. We utilized a fast and efficient protein precipitation method in a 96-well plate format to extract both analytes from biological matrices. Erlotinib was selected as the internal standard in this assay. Gradient elution using methanol and 0.1 % formic acid in water (v/v) was applied on an Acquity UPLC BEH C18 column to separate all analytes. Sotorasib, M24, and erlotinib were detected with a triple quadrupole mass spectrometer in positive electrospray ionization in multiple reaction monitoring mode. During the validation and sample quantification, a linear calibration range was observed for both sotorasib and M24 in a range of 4 - 4000 nM and 1 - 1000 nM, respectively. The %bias and %CV (both intra- and inter-day) for all tested levels in all investigated matrices were lower than 15 % as required by the guidelines. Sotorasib had a rather short room temperature stability in mouse plasma for up to 8 h compared to M24 which was stable up to 16 h at room temperature. This method has been successfully applied to measure sotorasib and M24 in several mouse matrices from three different mouse strains. We can conclude that the plasma exposure of sotorasib in mice is limited via human CYP3A4- and mouse Cyp3a-mediated metabolism of sotorasib into M24.

An evaluation of sotorasib for the treatment of patients with non-small cell lung cancer with KRAS G12C mutations

INTRODUCTION

Improving the clinical outcomes of patients with KRAS^G12C-mutated non-small cell lung cancer (NSCLC), the majority of whom are current or former smokers, has been a barrier to improving population-level outcomes in NSCLC. Novel, effective KRAS^G12C inhibitors are emerging and sotorasib is the first member of that class to achieve commercial availability.

AREAS COVERED

In this review, we survey the epidemiology of KRAS^G12C-mutated NSCLC, as well as sotorasib's chemistry, pharmacology, and clinical trial data.

EXPERT OPINION

While sotorasib's development has been unique and exciting, questions persist regarding its intracranial penetrance, optimal dose, and efficacy relative to standard-of-care therapy. Improvements in the clinical activity of KRAS inhibition will hinge on better understanding of resistance mechanisms, the development of broad-spectrum inhibitors with activity beyond G12C mutations, and combination therapy targeting multiple mediators of KRAS signaling and alternative pathways. From a regulatory perspective, sotorasib's development may, in time, prove to be an instructive example for early-phase clinical trialists and regulators focused on dose optimization.

Absorption, metabolism and excretion of [14C]-sotorasib in healthy male subjects: characterization of metabolites and a minor albumin-sotorasib conjugate

PURPOSE

The objectives of this study were to characterize the absorption, metabolism, and excretion of sotorasib and determine the metabolites present in plasma, urine, and feces in healthy male subjects following a single oral 720 mg dose containing approximately 1 μCi of [¹⁴C]-sotorasib.

METHODS

Urine, feces, and plasma were collected post-dose and assayed for total radioactivity and profiled for sotorasib metabolites. Urine and plasma were also assayed for sotorasib pharmacokinetics. In addition, in vitro studies were performed to determine the enzymes responsible for formation of major circulating metabolites and protein adducts in human plasma.

RESULTS

Sotorasib was rapidly absorbed, with a median time to peak concentration of 0.75 h. Mean t_1/2,z of plasma sotorasib, whole blood total radioactivity, and plasma total radioactivity were 6.35, 174, and 128 h, respectively. The geometric mean cumulative recovery was 80.6%; the majority was excreted in feces (74.4%) with a low percentage excreted in urine (5.81%). M10, sotorasib, and M24 were present at 31.6%, 22.2%, and 13.7% of total radioactivity in plasma extracts, respectively. M10 and sotorasib were present at < 5% of administered radioactivity in urine, while only unchanged sotorasib, at 53% of administered radioactivity, was identified in feces. A sotorasib-albumin adduct was identified in plasma as a minor constituent, consistent with the observed radioactivity profile in plasma/blood.

CONCLUSION

Sotorasib metabolism involves nonenzymatic glutathione conjugation, GGT-mediated hydrolysis of glutathione adduct, and direct CYP3A and CYP2C8-mediated oxidation. Elimination of sotorasib is predominantly fecal excretion, suggesting dose reduction is not necessary with renal impairment.

FDA Approval Summary: Sotorasib for KRAS G12C-Mutated Metastatic NSCLC

On May 28, 2021, the FDA granted accelerated approval to sotorasib (Lumakras, Amgen) for the treatment of adults with advanced non-small cell lung cancer (NSCLC) with a Kirsten rat sarcoma proto-oncogene (KRAS) G12C mutation who have received at least one prior systemic therapy. The approval was based on CodeBreaK 100 (Study 20170543), a dose-escalation and dose-expansion trial in patients with an advanced, KRAS G12C-mutated, solid tumor. The overall response rate (ORR) observed in patients with KRAS G12C-mutated NSCLC treated with sotorasib (n = 124) was 36% [95% confidence interval (CI), 28-45]. The median duration of response was 10.0 months (95% CI, 6.9-not estimable). The most common adverse reactions (≥20%) were diarrhea, musculoskeletal pain, nausea, fatigue, hepatotoxicity, and cough. This is the first approval of a targeted therapy for KRAS G12C-mutated NSCLC. Because of pharmacokinetic data and ORRs of patient cohorts who took sotorasib at lower doses in the dose-escalation portion of CodeBreaK 100, a dose comparison study is being conducted as a post-marketing requirement.