Research on the drug palbociclib is being conducted, focusing on its use in treating hormone receptor-positive breast cancer. Studies are examining biomarkers to determine response to palbociclib, as well as comparing its effectiveness to other treatments, including ribociclib and chemotherapy. The research includes data from various trials, including the PALOMA-2/3 trials, and is exploring the biological activity and real-world effectiveness of palbociclib in different settings.