The landscape of cancer treatment is rapidly evolving, driven by relentless innovation and a deepening understanding of tumor biology. Among the leading developers in this revolution is Byondis, an independent Dutch biopharmaceutical company with a bold mission: to deliver breakthrough solutions for patients with cancer through the creation of innovative, targeted medicines.
At the annual meeting of the American Society for Cancer Research (AACR), held April 17 – 22, 2026, in San Diego, CA, Byondis is set to showcase two of its most advanced antibody-drug conjugate (ADC) technology platforms—in what promises to be a defining moment for the future of targeted cancer therapies.[1][2]
The Next Frontier in ADC Technology
Antibody-drug conjugates represent a unique therapeutic approach, combining the precision of monoclonal antibodies with the potent cell-killing ability of cytotoxic drugs. This marriage enables highly selective targeting of cancer cells while sparing healthy tissue—a paradigm shift from traditional chemotherapies. However, as with many transformative technologies, ADCs face significant hurdles: resistance to current payloads is on the rise, and many patients remain unresponsive to available immune therapies.
Byondis is tackling these challenges head-on, unveiling two state-of-the-art ADC platforms at AACR 2026. These platforms—the first-in-class antifolate linker-drug platform and the innovative phosphonate linker-drug platform—are engineered to overcome the limitations of existing therapies, expand the horizons of cancer treatment, and offer hope to patients with limited options.
Antifolate ADCs: A Novel Mechanism for Overcoming Resistance
Resistance to widely used ADC payloads, such as topoisomerase I (TOPO1) and tubulin inhibitors (e.g., Auristatins and Maytansinoids), poses a growing obstacle in oncology, wich limited efficacy through acquired resistance, dose-limiting toxicities, and poor delivery, and often <1% of the dose reaches solid tumors. Many tumors eventually develop mechanisms to evade these agents, leading to relapse and treatment failure. [1] Recognizing this, Byondis has revisited the antifolate class—a group of drugs with a long history in cancer therapy but previously hampered by poor tumor selectivity and systemic toxicity.[2]
The Byondis antifolate linker-drug platform is a proprietary advance, featuring an orthogonal mechanism of action based on clinically validated biology. This approach is designed to address acquired resistance that can develop with current ADC treatments, positioning it for use across multiple lines of therapy. The optimized payload demonstrates low- to sub-nanomolar potency, robust inhibition of the target enzyme dihydrofolate reductase (DHFR), and broad cytotoxicity against a spectrum of cancer cell lines.[2]
A key innovation is the use of a glucuronide-based linker, which enhances the ADC’s therapeutic index. This linker maintains favorable physicochemical properties, preserves ADC stability, and supports dual-payload strategies—where two different drugs can be delivered simultaneously to maximize tumor killing.
The lead antifolate ADC, which targets an undisclosed tumor antigen, has shown strong in vitro activity and achieved robust tumor regressions in patient-derived xenograft models of non-small cell lung cancer (NSCLC) and head and neck squamous cell carcinoma (HNSCC). Notably, these effects were observed without significant toxicity at active doses—a critical consideration for the successful translation of new therapies to the clinic.
Addressing Unmet Needs
Methotrexate (MTX), the prototypical antifolate, revolutionized oncology and autoimmune disease treatment but was limited by off-target effects and systemic toxicity. Byondis’ antifolate ADC platform reintroduces this class with a new level of precision, leveraging antibody targeting to deliver the payload directly to tumor cells. The optimized antifolate linker-drug (LD) is currently undergoing GMP-scale manufacturing to support future clinical studies.
This differentiated profile supports broad tumor applicability and positions antifolate-based ADCs as a promising solution for patients with resistant disease. By enabling sequential ADC therapy and overcoming the limitations of existing payloads, Byondis’ platform offers a much-needed alternative in the evolving field of targeted cancer treatment.
Phosphonate ADCs: Harnessing the Power of Immunostimulation
While targeted cytotoxicity is a proven strategy, harnessing the body’s immune system to attack cancer has emerged as one of the most exciting frontiers in oncology. However, a significant proportion of patients do not respond to current immune therapies, such as checkpoint inhibitors. Recognizing this gap, Byondis has developed a groundbreaking immunostimulatory ADC platform—ByonBoost™—that activates a unique subset of immune cells: Vγ9Vδ2 (gamma delta) T cells.[3]
Gamma delta (γδ) T cells are potent cytotoxic effectors that bridge innate and adaptive immunity and can recognize and eliminate tumor cells independently of major histocompatibility complex (MHC) presentation. [4] Their presence within tumors correlates with improved clinical outcomes across diverse cancer types. The Vγ9Vδ2 subset, predominant in human blood, recognizes intracellular phosphoantigens via a process called inside-out activation of the butyrophilin (BTN)3A/BTN2A complex.[5]
Previous attempts to activate these cells in cancer patients have been stymied by a lack of tumor specificity and rapid clearance from the body. Byondis’ phosphonate ADCs overcome these barriers by coupling a tumor-associated antigen (TAA)-targeting antibody with a cleavable phosphonate payload. This design ensures that the immunostimulatory agent is delivered directly to tumor cells, where it can trigger robust activation of Vγ9Vδ2 T cells within the tumor microenvironment.
Dual Mechanisms: Direct Killing and Immune Activation
Byondis’ phosphonate ADCs have been successfully applied to antibodies targeting multiple TAAs—including CD123, CD20, TROP2, and HER2—demonstrating broad applicability. In preclinical studies, these ADCs drive robust and targeted immune activation, inducing cytokine release, degranulation, and efficient tumor cell lysis. Notably, these effects have been validated both in vitro (using cancer cell lines and primary patient material) and in vivo (in animal models of acute myeloid leukemia and solid tumors).
In non-human primate models, the lead phosphonate ADC candidate displayed excellent tolerability, with no clinical signs of cytokine release syndrome (CRS) even at high doses—an important safety milestone for immunostimulatory therapies.
The modular nature of the ByonBoost™ phosphonate linker-drug technology platform allows it to be paired with virtually any tumor-targeting antibody, and its dual mechanism (direct cytotoxicity plus immune activation) positions it as a versatile and powerful therapeutic modality. Importantly, the platform preserves the antibody’s Fcγ receptor-mediated effector functions, further enhancing its antitumor potential.
Translational Relevance and Broad Applicability
The innovations presented by Byondis at AACR 2026 are more than incremental advances—they are foundational shifts in how ADCs can be designed, manufactured, and deployed against cancer. The antifolate platform reintroduces a clinically validated mechanism of action with enhanced selectivity, potency, and manufacturability, making it suitable for use across a variety of tumor types. The phosphonate platform, meanwhile, brings the promise of targeted immunotherapy to patients who may not benefit from existing immune therapies.
Byondis’ research underscores the importance of mechanistic diversity in ADC design. As resistance to dominant payloads increases, the need for novel approaches becomes ever more pressing. Both the antifolate and phosphonate ADC platforms offer differentiated mechanisms of action and have demonstrated efficacy and safety in rigorous preclinical models.
Overcoming the Limitations of Current Therapies
A recurring theme in cancer therapy is the emergence of resistance. Tumors are remarkably adept at evolving to evade the effects of cytotoxic agents, whether by upregulating drug efflux pumps, mutating target enzymes, or altering cellular pathways. Byondis’ antifolate ADCs are specifically engineered to overcome these resistance mechanisms. The optimized payloads show minimal affinity for resistance-associated transporters such as BCRP and PGP, ensuring sustained intracellular activity.
Moreover, the glucuronide-based linker not only improves the therapeutic index but also maintains the ADC’s hydrophilic properties, supporting manufacturability and stability. This is a critical advantage as the field moves toward more complex and potent ADCs, where balancing efficacy with safety and scalability is paramount.
On the immunotherapy front, Byondis’ phosphonate ADCs represent a new class of immunostimulatory agents that directly activate Vγ9Vδ2 T cells in the tumor microenvironment. Vγ9Vδ2 T cells are the predominant subset of γδ T cells in human peripheral blood, acting as innate-like lymphocytes that recognize non-peptide phosphoantigens (like IPP) in an MHC-unrestricted manner. They are highly promising in cancer immunotherapy, capable of directly killing tumor cells and producing cytokines like IFN-ϒ. [6]
Byondis’ approach bypasses MHC presentation and offers a route to effective immunotherapy for patients whose tumors are refractory to current treatments. The successful demonstration of robust immune activation, tumor cell lysis, and excellent tolerability in preclinical models paves the way for clinical translation.
Towards a New Generation of Cancer Therapeutics
Byondis’ commitment to innovation is evident in its strategic focus on modularity and scalability. Both ADC platforms are designed to be compatible with a range of antibodies and payloads, enabling rapid adaptation to emerging targets and evolving clinical needs. The potential for dual-payload strategies further enhances the therapeutic flexibility of these platforms.
As Byondis prepares to advance its lead candidates into clinical development, the implications for patients are profound. For those with tumors resistant to existing ADCs, the antifolate platform offers a new line of attack. For patients ineligible for immune therapy or unresponsive to checkpoint inhibitors, the phosphonate platform provides a novel approach to harnessing the immune system’s power.
A Vision Realized, a Future Transformed
The presentations at AACR 2026 mark a milestone for Byondis and for the field of targeted cancer therapy. By combining scientific rigor with a patient-centric vision, Byondis is setting new standards in the design and application of ADCs. Its antifolate and phosphonate platforms are poised to address unmet clinical needs, offering hope to patients who have exhausted other options.
As the oncology community gathers in San Diego, CA, the promise of these innovations will be on full display. The next generation of cancer therapeutics is taking shape—not only in the laboratory and the clinic, but in the lives of patients around the world.
Byondis’ journey is a testament to the power of innovation, collaboration, and unwavering commitment to patient care. With its pioneering ADC platforms, Byondis is not just imagining the future of cancer treatment—it is building it, one breakthrough at a time.
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Reference
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[5] Xin W, Huang B, Chi X, Liu Y, Xu M, Zhang Y, Li X, Su Q, Zhou Q. Structures of human γδ T cell receptor-CD3 complex. Nature. 2024 Jun;630(8015):222-229. doi: 10.1038/s41586-024-07439-4. Epub 2024 Apr 24. PMID: 38657677; PMCID: PMC11153141.
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Featured image courtesy © 2022 – 2026 Byondis. Used with permission.
DOI: 10.14229/jadc.2026.17.04.020
