While CDK4/6i impacts the specific component of the cell cycle machinery with significantly reduced toxicity compared to pan-CDK inhibitors, FDA recently published a safety warning for all three approved CDK4/6i on the rare but severe inflammation in the lungs, which may lead to fatality (https://www.fda.gov/drugs/drug-safety-and-availability/fda-warns-about-rare-severe-lung-inflammation-ibrance-kisqali-and-verzenio-breast-cancer). Here, CDK4 is linked to breast carcinoma.