A Study of Lenvatinib, Pembrolizumab, and Fulvestrant in People With Breast Cancer

This study tests a three-drug combination — lenvatinib (a targeted therapy), pembrolizumab (an immunotherapy), and fulvestrant (a hormone-blocking drug) — in patients with advanced hormone-receptor-positive, HER2-negative breast cancer that has progressed after standard hormone therapy and CDK4/6 inhibitor treatment. **You may be eligible if...** - You are 18 or older with confirmed ER-positive, HER2-negative locally advanced or metastatic breast cancer - Your cancer progressed after at least one prior hormone therapy combined with a CDK4/6 inhibitor - You have measurable disease on scans - Your ECOG performance status is 0 or 1 - Your organ function (blood, liver, kidney, heart) is within acceptable range **You may NOT be eligible if...** - You have received prior pembrolizumab, lenvatinib, or other PD-1/PD-L1 or VEGF-targeting drugs - You have active, untreated cancer spread to the brain - You have an active autoimmune disease requiring systemic treatment - You have active HIV, untreated hepatitis B or C - You are unable to swallow capsules - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.