PURPOSE MDM2, a negative regulator of the TP53 tumor suppressor, is oncogenic when amplified. MDM2 amplification (MDM2amp) is mutually exclusive with TP53 mutation and is seen in 6% of patients with lung adenocarcinoma (LUAD), with significant enrichment in subsets with receptor tyrosine kinase (RTK) driver alterations. Recent studies have shown synergistic activity of MDM2 and MEK inhibition in patient-derived LUAD models with MDM2amp and RTK driver alterations. However, the combination of MDM2 and RTK inhibitors in LUAD has not been studied. METHODS We evaluated the combination of MDM2 and RTK inhibition in patient-derived models of LUAD. RESULTS In a RET-fusion LUAD patient-derived model with MDM2amp, MDM2 inhibition with either milademetan or AMG232 combined with selpercatinib resulted in long-term in vivo tumor control markedly superior to either agent alone. Similarly, in an EGFR-mutated model with MDM2amp, combining either milademetan or AMG232 with osimertinib resulted in long-