Abstract
PI3K and CDK4/6 inhibitors (CDK4/6i) are targeted therapies approved to treat advanced breast cancer; CDK4/6is are more widely used. Here, we discuss trials that examine PI3K inhibitors with novel drug combinations, including a CDK4/6i, given data implicating the pathway in CDK 4/6 resistance.See related articles by Lu et al., p. 408, and Tolaney et al., p. 418.