Byondis Announces Strategic Transformation to Deliver Next Generation Antibody-Drug Conjugate Technology Platforms & Focus on Partnering

Prioritizing High-Potential Earlier Stage Pipeline of Novel Cytotoxic- and Immune-Stimulating Linker-Drug Platforms, Tumor-Specific Masking and Proprietary Dual Payload Technologies

Discontinuation of Clinical Stage Programs and Restructuring Organization to Speed Advancement of Novel ADC Technology Platforms

Nijmegen, The Netherlands, − 11 December 2025 – Byondis B.V., an independent biopharmaceutical company creating innovative targeted medicines for patients with cancer, announces today the Company has undergone a strategic transformation to focus its research and development efforts on its novel antibody-drug conjugate (ADC) technology platforms. Byondis’ technology platforms combine the Company’s proprietary payloads with state-of-the-art linker- and conjugation technologies and improved targeting. This includes clinically validated MoAs, dual payloads and tumor specific release.  

“Our ADC technology platforms are generating potential first and best-in-class assets and prioritizing their advancement reflects Byondis’ pioneering vision and 20 years of expertise in the ADC field to make meaningful contributions to science and patient care,” said Jacques Lemmens, PhD, Founder and Chief Executive Officer of Byondis. “We recognize the rapid and exciting pace of ADC development, and we plan to leverage our deep knowledge of ADCs, focused clinical development plans and partnership options to act on the urgency and possibility of addressing high unmet medical needs with next generation solutions.”

Each of Byondis’ technology platforms has generated frontrunner and multiple follower drug candidates. Given the breadth and depth of the new ADC technology portfolio, Byondis will focus on pursuing strategic partnerships with leading Biotechs, Pharma and Venture Capital across its technology platforms and assets to accelerate development and maximize the commercial potential, while developing the lead candidates towards the clinic independently.

• Antifolate Linker-Drug Platform: Working to overcome ADC resistance as therapies move into earlier treatment lines and in combination, the antifolate platform provides a differentiated yet clinically validated MoA that is orthogonal to commonly used ADC payloads and is designed to overcome systemic side effects.

• Masking Platform ByonGuardTM: Universal, protease‑cleavable, steric masking platform, that limits binding in healthy tissues and restores full target engagement in tumors, designed to improve the therapeutic index of ADCs and other antibody-based therapies.

• Phosphonate Linker-Drug Platform ByonBoostTM: Addressing a critical need for patients who do not respond to immune therapy, the ByonBoost linker-drug platform is engineered to activate Vγ9Vδ2 (γδ) T cells in the tumor microenvironment, enabling targeted delivery with an immunologic anti‑tumor effect and compatibility with single‑ and dual‑payload concepts.

With Byondis’ fully integrated discovery, development and manufacturing capabilities, the Company has the flexibility to conduct all important and essential activities in-house. As part of the strategic transformation, Byondis has halted development of its two clinical stage programs: The anti-SIRPα monoclonal antibody, BYON4228, and the CD123 targeting ADC, BYON4413 and has restructured its operational efforts to reflect the earlier stage program focus, with approximately 200 employees making up the Company moving forward.

About Byondis

Driven to improve patients’ lives, Byondis is an independent, fully integrated biopharmaceutical research and development company creating innovative targeted medicines for cancer. The company is developing new biological entities (NBEs) with a focus on antibody-drug conjugates.

Byondis’ development portfolio leverages its expertise in linker-drug (LD) technology, antibody-drug conjugation and disease biology. Byondis’ fully integrated drug development capabilities cover all stages from pre-clinical and clinical R&D, production of clinical batches of the selected product candidates and regulatory filings, which are all done in-house.

The company has a dedicated team of more than 200 staff working in its state-of-the-art R&D and GMP manufacturing facilities in Nijmegen, the Netherlands.