Based on two cases of severe rhabdomyolysis in patients taking a CDK4/6 inhibitor and simvastatin, a CYP3A and OATP1B substrate, we tested the hypothesis that CDK4/6 inhibitors may precipitate drug-drug interactions through these mechanisms.<h4>Methods</h4>We assessed the ability of CDK4/6 inhibitors to inhibit CYP3A and OATP1B-type transporters. This evidence concerns the gene CYP3A4 and rhabdomyolysis.