ONA-255

ONA-255 is a first-in-class antibody-drug conjugate (ADC) developed by Ona Therapeutics for the treatment of multiple solid tumors, including breast and gastric cancers. The drug is designed to target a novel, undisclosed antigen that acts as a universal driver of resistance in advanced cancers. By leveraging privileged insights into this target’s biology, ONA-255 aims to deliver highly potent cytotoxic agents directly to resistant tumor clones, with the goal of achieving deeper and more durable responses in patients who have limited treatment options. The ADC is engineered using advanced biologic techniques for optimized pharmacokinetics and tolerability. As of mid-2025, ONA-255 remains in IND-enabling preclinical development with clinical trials anticipated to begin by late 2025[1][2][3][4][5][6][7].