Of 20 efficacy-evaluable patients, a total of 3 partial responses were observed, including 2 patients with osimertinib-resistant NSCLC who had an EGFR T790M mutation….Combination treatment with pelcitoclax and osimertinib at RP2D was safe and feasible. Preliminary synergy and efficacy of both pelcitoclax and osimertinib were also observed in some patients with osimertinib-resistant NSCLC.