Phase II Trial of Regorafenib and Oral Methotrexate in Previously Treated Advanced KRAS-Mutant NSCLC

There are no standard targeted treatment options for advanced KRAS-mutant NSCLC beyond KRAS G12C inhibitors. A computational model identified regorafenib and low-dose methotrexate as synergistic in preclinical models of KRAS-mutant NSCLC. This study evaluated the efficacy and safety of the combination in previously treated advanced KRAS-mutant NSCLC.

This single-arm phase II study included regorafenib 80 to 120 mg oral daily and oral methotrexate dose escalated to tolerability from 10 to 20 mg twice weekly during the first cycle. Both agents were administered on weeks 1 to 3 of each 4-week cycle. The primary end point was progression-free survival.

In total, 18 patients with KRAS-mutant NSCLC were enrolled. Five patients received regorafenib at a 120 mg starting dose with four discontinuing due to toxicity; subsequently, 13 patients were treated at an 80 mg starting dose, with eight dose-escalating to 120 mg after the first cycle. Median progression-free survival was 3.7 months (95% confidence interval 1.8-8.6) and median overall survival was 10.4 months (95% confidence interval 5.2-30.3). The objective response rate was 16.7% and the 8-week disease control rate was 66.7%. Grade 3 treatment-related adverse events occurred in 11 patients, most often oral mucositis (n = 2) and asymptomatic lipase increase (n = 2). One patient developed asymptomatic grade 4 lipase increase.

Combination treatment of regorafenib and oral methotrexate in patients with KRAS-mutant NSCLC was limited due to toxicity, and the study did not meet its primary end point. Computational modeling may aid in repurposing therapeutic options though caution must be exercised with tolerability.