The tumor cell inhibition rates of WX-0593 and panitumumab alone or combined were assessed in osimertinib-resistant cis EGFR triple-mutant cell lines, including PC9 (EGFR Del19/T790M/C797S), NCI-H1975 (EGFR L858R/T790M/C797S), Ba/F3 (EGFR L858R/T790M/C797S and EGFR Del19/T790M/C797S). The in vivo tumor suppressive efficacy of single-agent WX-0593, panitumumab, and their combination was evaluated in H1975 (EGFR del19/T790M/C797S) and Ba/F3 (EGFR L858R/T790M/C797S) cell line-derived xenograft (CDX) models of BALB/c nude mice...the combination of WX-0593 and panitumumab had a potent synergistic effect on proliferation inhibition in all the four cell lines with cis EGFR triple mutations resistant to osimertinib. WX-0593 and panitumumab alone had tumor suppressive effects in the Ba/F3 CDX model. The data from the study suggested that WX-0593 and panitumumab had a promising synergistic effect on osimertinib-resistant EGFR-mutant NSCLC both in vitro and in vivo.