Ona Therapeutics raised $86.6 million in an oversubscribed Series B to advance two antibody drug conjugates into early clinical testing. The Barcelona-based biotech plans to prioritize ONA-255 in breast cancer and progress ONA-389 in colorectal cancer, with capital aimed at clinical proof-of-concept and first-in-human execution. Ona’s funding round included participation from existing investors and new backers, with co-leads Columbus Venture Partners and Mérieux Equity Partners. The company described a patient-driven target discovery platform designed to identify tumor-specific antigens and epitopes that support targeted payload delivery while aiming to reduce on-target off-tumor toxicity. The financing reflects continuing investor appetite for next-generation ADC approaches focused on improved selectivity and internalization. With ONA preparing clinical launches, the company’s early trial design and biomarker strategy will likely determine how quickly it can differentiate from crowded ADC competitors.