A Study of HLD-0117 in Patients With Metastatic Breast Cancer

This Phase 1 study is testing HLD-0117, a new oral drug, in women with estrogen receptor-positive (ER+) metastatic or locally advanced breast cancer whose disease has progressed on prior treatments including CDK4/6 inhibitors and at least one endocrine therapy. The trial will first find the maximum safe dose through dose escalation, then expand to explore the drug's anti-tumor activity. Women aged 18 or older who are postmenopausal (through surgery, natural menopause, or ovarian suppression), have measurable disease, an ECOG performance status of 0–1, and adequate organ function are eligible, excluding those with inflammatory breast cancer, brain metastases, or significant cardiovascular disease. Participants will take HLD-0117 orally at assigned doses, attend regular clinic visits for safety and tumor monitoring, and provide tumor biopsies at the start and during treatment where feasible. This summary was prepared to help patients understand the study in plain language.