Ona Therapeutics Raises $86.6 Million Series B to Advance First-in-Class ADCs into Clinical Development
Key Insights
Ona Therapeutics (search) closed an oversubscribed $86.6 million Series B financing co-led by Columbus Venture Partners (search) and Mérieux Equity Partners (search), alongside new investors COFIDES and Korys and all existing investors.
Proceeds will fund clinical development of lead program ONA-255 (search), a first-in-class ADC for breast cancer (search), toward clinical proof of concept, and advance ONA-389 (search) toward first-in-human studies in colorectal cancer (search).
The financing marks Ona's transition to a clinical-stage company, supported by an experienced leadership team including Antoine Yver as Chair and Jutta Amersdorffer as Chief Medical Officer.
Barcelona-based Ona Therapeutics (search), a biopharmaceutical company pioneering first-in-class antibody-drug conjugates (ADCs) for treatment-resistant cancers, announced the closing of an oversubscribed $86.6 million Series B financing on June 4, 2026. The round was co-led by new investors Columbus Venture Partners (search) and Mérieux Equity Partners (search), with participation from additional investors COFIDES and Korys, alongside all existing investors — Alta Life Sciences, Asabys Partners, Bpifrance (as part of the InnoBio investment strategy), CDTI through SICC Innvierte, FundPlus NV, and Ysios Capital.
The financing propels Ona Therapeutics (search) into clinical-stage operations, with proceeds directed toward advancing its lead program, ONA-255 (search), a first-in-class ADC initially focused on breast cancer (search), toward clinical proof of concept. A second program, ONA-389 (search), targeting colorectal cancer (search), will progress toward first-in-human studies. Ona Therapeutics currently retains full worldwide commercial rights to all its assets.
A Differentiated Approach to ADC Engineering
Ona's pipeline is built on a proprietary patient-driven target discovery platform that identifies novel tumor-specific antigens and epitopes associated with resistance biology and advanced disease. The company's approach integrates deep biological insight with rigorous target validation, antibody engineering, optimized payload selection, and validated linker-payload technologies to generate precision-engineered ADCs.
According to the company, ONA-255 (search) is designed to address treatment-resistant tumor biology through a differentiated mechanism aimed at improving the therapeutic index compared to earlier approaches. The platform is engineered to maximize therapeutic activity while minimizing on-target toxicities and addressing key biological mechanisms of resistance in advanced tumors.
Leadership and Strategic Momentum
The financing arrives at what the company describes as a pivotal inflection point, as Ona enters clinical development and begins generating initial human safety and efficacy data for ONA-255 (search). The company's clinical leadership includes Antoine Yver as Chair of the Board, bringing deep expertise in global oncology drug development; Pamela Klein, Independent Board Member, with extensive experience advancing oncology therapeutics; Aleix Prat, a world-renowned breast cancer (search) oncologist serving as Chair of the Advisory Board; and Jutta Amersdorffer, Chief Medical Officer, leading clinical strategy and execution.
Valerie Vanhooren, PhD, Co-Founder and Chief Executive Officer at Ona Therapeutics (search), stated: "The oversubscribed Series B marks an important step to advancing ONA-255 (search) toward clinical proof of concept in breast cancer (search), while progressing early clinical development activities for ONA-389 (search) in colorectal cancer (search). We are proud to have assembled a high-quality syndicate of investors who share our conviction in the differentiated science behind Ona's novel targets and their potential to address drug resistance."
Investor Perspectives
Jose Mesa, Partner at Columbus Venture Partners (search) and incoming Board member, remarked: "At Columbus, we look for companies that combine world-class science with a clear path to clinical impact. Ona is a strong example of that. Its work on cancer resistance and metastasis addresses one of the most important challenges in oncology, and its pipeline, led by ONA-255 (search) and followed by ONA-389 (search), provides a compelling opportunity to build a differentiated oncology platform."
Valérie Calenda, Managing Partner and Head of Innovation at Mérieux Equity Partners (search) and incoming Board member, added: "The strength of Ona's preclinical data package behind ONA-255 (search), the breadth of opportunity across the pipeline, and the team's clear vision for translating novel biology into clinically meaningful therapies give us strong confidence in the Company's long-term potential."
Pipeline Expansion and Board Changes
Beyond breast and colorectal cancers, Ona is expanding its focus into additional aggressive cancer indications, including gastric and liver cancers. In connection with the financing, Jose Mesa, Valérie Calenda, and Eva Van Overmeire, Senior Investment Manager at Korys, will join Ona's Board of Directors.
Ona Therapeutics (search), a spin-off from IRB Barcelona and ICREA based at the Barcelona Science Park, continues to build on its foundational science in tumor biology and ADC engineering as it transitions into a clinical-stage biotechnology company.