Ona Therapeutics secured an oversubscribed $86.6 million Series B to advance two antibody-drug conjugates toward clinical proof of concept. The funding is set to accelerate ONA-255 in breast cancer while supporting ONA-389 as it moves toward first-in-human studies in colorectal cancer. The financing reinforces investor appetite for next-generation ADCs built around tumor-specific target discovery and aiming to improve therapeutic index by reducing off-tumor toxicity. Co-leads and new backers were named in connection with the round, signaling confidence in Ona’s platform and oncology execution. For the ADC market, the move adds another differentiated contender focused on patient stratification and payload delivery design, while highlighting that funding continues to flow even as trial differentiation becomes more scrutinized by regulators and payers.