Cheng et al. (2023) developed a virtual clinical trial for ER+ breast cancer patients using palbociclib (a cyclin-dependent kinase 4/6 inhibitor) with fulvestrant (an estrogen receptor antagonist) to explore alternatives to standard-of-care palbociclib dosing strategies (Cheng et al. 2023). The authors sought to determine whether alternative dosing strategies would be more effective, improve tolerability and overcome or delay resistance. They used in vitro drug synergy and cell cycle data to model the pharmacodynamics and integrated it with a pharmacokinetics model derived from clinical data. Here, ESR1 is linked to breast cancer.