EGFR/HER2-IN-4 is an irreversible, orally active dual inhibitor of EGFR activity (IC50: 0.6 nM). EGFR/HER2-IN-4 shows potent EGFR kinase inhibitory activity against L858R and T790M mutations. EGFR/HER2-IN-4 exhibits significant anti-tumour effects in vivo and can be used to study lung cancer.