Mechanisms of Acquired Resistance to Savolitinib, a Selective MET Inhibitor in

PURPOSE Some gastric cancers harbor MET gene amplifications that can be targeted by selective MET inhibitors to achieve tumor responses, but resistance eventually develops. Savolitinib, a selective MET inhibitor, is beneficial for treating patients with MET-driven gastric cancer. Understanding the resistance mechanisms is important for optimizing postfailure treatment options. PATIENTS AND METHODS Here, we identified the mechanisms of acquired resistance to savolitinib in 3 patients with gastric cancer and MET-amplified tumors who showed a clinical response and then cancer progression. Longitudinal circulating tumor DNA (ctDNA) is useful for monitoring resistance during treatment and progression when rebiopsy cannot be performed. RESULTS Using a next-generation sequencing 100-gene panel, we identified the target mechanisms of resistance MET D1228V/N/H and Y1230C mutations or high copy number MET gene amplifications that emerge when resistance to savolitinib develops in patients with MET-amplified gastric cancer. CONCLUSION We demonstrated the utility of ctDNA in gastric cancer and confirmed this approach using baseline tumor tissue or rebiopsy.