Ona Therapeutics secured $86.6 million in an oversubscribed Series B round to advance two antibody-drug conjugate programs into human testing. The financing is aimed primarily at ONA-255 in breast cancer and ONA-389 in colorectal cancer, with both candidates built on Ona’s patient-driven antigen and epitope discovery approach. The company said its strategy is designed to identify tumor-specific targets that can improve internalization and targeted payload delivery, aiming to reduce on-target/off-tumor toxicity. This funding adds momentum for next-wave ADC development focused on differentiating antigen selection and payload delivery mechanisms rather than competing only on linker chemistry or generic targeting. Key investor participation includes new backers and co-leads, signaling that capital is continuing to concentrate around teams with proprietary target identification and clear clinical sequencing plans.