INTRODUCTION: KRAS glycine-to-cysteine substitution at codon 12 (G12C) mutation is a well-recognized and increasingly promising therapeutic target with huge unmet clinical needs in NSCLC patients. IBI351 is a potent covalent and irreversible inhibitor of KRAS G12C. Here, we present the efficacy and safety of IBI351 from an open-label, single-arm, phase 2 pivotal study.
METHODS: Eligible patients with NSCLC with KRAS G12C who failed standard therapy were enrolled. IBI351 was orally administered at a dose of 600 mg twice daily. The primary endpoint was confirmed objective response rate assessed by an independent radiological review committee (IRRC) as per Response Evaluation Criteria in Solid Tumors v1.1. Other endpoints were safety, IRRC-confirmed disease control rate, duration of response, progression-free survival (PFS), and overall survival.
RESULTS: As of December 13, 2023, 116 patients were enrolled (Eastern Cooperative Oncology Group Performance Status 1: 91.4%; brain metastasis: 30.2%; prior treatments with both anti-PD-1 or anti-PD-L1 inhibitors and platinum-based chemotherapy: 84.5%). As per the IRRC assessment, the confirmed objective response rate was 49.1% (95% confidence interval [CI]: 39.7-58.6), and the disease control rate was 90.5% (95% CI: 83.7-95.2). The median duration of response was not reached whereas disease progression or death events occurred in 22 patients (38.6%), and the median PFS was 9.7 months (95% CI: 5.6-11.0). overall survival data was immature. Treatment-related adverse events (TRAEs) occurred in 107 patients (92.2%) whereas 48 patients (41.4%) had equal to or higher than grade three TRAEs. Common TRAEs were anemia (44.8%), increased alanine aminotransferase (28.4%), increased aspartate aminotransferase (27.6%), asthenia (26.7%) and presence of protein in urine (25.0%). TRAEs leading to treatment discontinuation occurred in nine patients (7.8%). In biomarker evaluable patients (n = 95), all patients had positive KRAS G12C in tissue whereas 72 patients were blood-positive and 23 were blood-negative for KRAS G12C. Patients with KRAS G12C in both blood and tissue had higher tumor burden at baseline (p < 0.05) and worse PFS (p < 0.05). Tumor mutation profiling identified tumor protein p53 (45.3%), serine/threonine kinase 11 (STK11) (30.5%), and kelch-like ECH-associated protein 1 (21.1%) as the most common genes co-mutated with KRAS G12C. Among 13 genes with mutation frequency equal to or higher than 5%, mutations of six genes (STK11, kelch-like ECH-associated protein 1, phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit gamma, DNA polymerase epsilon, SMAD family member 4, and BMP/retinoic acid-inducible neural-specific protein 3) were significantly associated with worse PFS (p < 0.05). Mutation in STK11 was also found to have a significant association with higher tumor burden at baseline and lower response rate (p < 0.05).
CONCLUSIONS: IBI351 monotherapy demonstrated promising and sustained efficacy with manageable safety, supporting its potential as a new treatment option for KRAS G12C-mutant NSCLC.
