In the present study, the CDK1/2/9 inhibitor AZD5438 exerted significant tumor inhibition in two PDX models with high copy number of CCNE1, and we also found that AZD5438 exerted antitumor activity by inhibiting the expression of CDK2, CCNE1, and phosphorylated retinoblastoma (pRb). The gene discussed is CDK1; the disease is neoplasm.