Ona Therapeutics closed an oversubscribed $86.6 million Series B to advance two antibody-drug conjugates into human testing. The Barcelona-based biotech will use the funds primarily to push ONA-255 into clinical development in breast cancer and to support ONA-389 toward first-in-human studies in colorectal cancer. The financing includes new investors COFIDES and Korys alongside Columbus Venture Partners and Mérieux Equity Partners as co-leads, with many existing backers participating. Ona says its target discovery platform is built to identify tumor-specific antigens and epitopes, enabling ADC design intended to improve internalization of payloads. Company statements emphasized moving quickly to clinical and regulatory milestones while maintaining execution capacity for both programs.