Ona Therapeutics closed an oversubscribed $86.6 million Series B to advance two antibody drug conjugates into human testing. The Barcelona-based biotech plans to move ONA-255, initially targeting breast cancer, toward clinical proof of concept while progressing ONA-389, designed for colorectal cancer, into first-in-human studies. The financing included co-leads Columbus Venture Partners and Mérieux Equity Partners and new backers COFIDES and Korys, with existing investors such as Alta Life Sciences and Ysios Capital participating. Ona said the funding is intended to support rapid and rigorous clinical execution and key regulatory milestones. CEO Valerie Vanhooren highlighted a syndicate aligned with Ona’s ADC discovery platform, which the company says enables targeted payload delivery with efficient internalization to reduce toxicity.