HLD-0117

HLD-0117 is an orally bioavailable small molecule and the lead development candidate from Halda Therapeutics' proprietary Regulated Induced Proximity TArgeted Chimera (RIPTAC) platform. It is designed for the treatment of patients with estrogen receptor-positive (ER+), HER2-negative metastatic breast cancer, particularly those who have progressed on standard-of-care treatments such as endocrine therapies and CDK4/6 inhibitors. HLD-0117 employs a "hold-and-kill" mechanism of action, functioning as a heterobifunctional molecule that simultaneously binds to the Estrogen Receptor and a second, ubiquitously expressed intracellular protein. This binding induces the formation of a stable ternary complex that physically blocks ER-mediated gene transcription and triggers selective apoptosis in cancer cells. This mechanism is distinct from targeted protein degradation (PROTACs) as it does not rely on the ubiquitin-proteasome system, potentially offering a broader therapeutic window and overcoming resistance to existing ER-targeted agents.