The MONARCH 1 trial showed that 26.2% of patients (34 of 130) reported hypokalaemia of all grades treated with abemaciclib alone, while 2 patients reported hypokalaemia of grade 3.6 These findings suggest that CDK4/6 inhibitors may increase the risk of GGT abnormality and hypokalaemia, warranting ongoing monitoring in subsequent SPH4336 studies. This evidence concerns the gene CDK4 and Hypokalemia.