Engineering the Next Generation of Bispecific Antibodies

Emerging clinical validation of costimulatory T cell engager strategies demonstrates the potential to improve the depth and durability of responses in cancer patients. Therapeutic design considerations will be discussed for integrating TCR and costimulatory receptor activation, selecting alternative costimulatory pathways, and employing single versus multiple-tumour antigen targeting strategies, which together are crucial for maximizing selective tumor engagement and optimising T cell effector activity to restore anti-tumour immunity in cancer patients.

We introduce an innovative approach that allows the creation of a huge library of bi- and multispecific nanobody-based TNF receptor targeting biologicals. This type of biological library does not need chain pairing mutations and is obtained by coexpression of genetically engineered constant antibody domains fused with nanobodies. Such fusion proteins proved to be highly homogenous with respect to productivity and stability and are thus of particular translational interest.

Multiple projects in developing multi-specific antibodies have been performed with the aim to develop either innate or T cell immune engagers to treat haematological or solid cancers. Projects were either highly successful resulting in meaningful clinical outcomes or failed. Case studies will be presented from our rich in house database to understand the complex parameters required for successful multispecific development including molecule architecture, synapse distance, structure-function relationship and developability.

Bispecific antibodies that engage blood–brain barrier receptors enable systemic delivery of biologics to the CNS, yet limited cell-type specificity constrains efficacy and safety. We are engineering shuttles that couple BBB transport with targeting to neurons, microglia and other brain cell types. These platforms deliver antibodies, cytokines, and antisense oligonucleotides, achieving selective activation, immune modulation, and gene silencing in vivo. We will discuss design principles, PK/PD relationships, and efficacy results to date across different neurological disease models.

NXT007 is a next-generation FVIIIa-mimetic bispecific antibody designed to achieve hemostatic normalisation in people with the bleeding disorder hemophilia A. This presentation details a comprehensive preclinical comparison between NXT007 and emicizumab across multiple in vitro and in vivo models. We demonstrate that NXT007 provides significantly greater potency in thrombin generation, clotting, and bleeding assays, with no evidence of hypercoagulability. Our results support the ongoing clinical development of NXT007 and its potential to improve therapeutic efficacy and patient outcomes by reaching non-hemophilic levels of hemostasis.

Targeting blood–brain barrier proteins such as TfR and CD98hc enables more effective brain delivery of biotherapeutics for neurological diseases. We engineered a human IgG1 Fc domain to bind both receptors, creating a dual transport vehicle (TV) platform that achieves higher brain concentrations than targeting either receptor alone. By tuning affinities to TfR and CD98hc, we can modulate brain uptake kinetics and biodistribution—where stronger TfR binding drives faster uptake and clearance, while stronger CD98hc binding promotes higher, more sustained brain exposure.

The clinical activity of T cell bispecific antibodies (TCBs) in solid tumours remains limited. Insufficient co-stimulatory signals are suspected to be a major factor contributing to the suboptimal efficacy. Tumour-directed co-stimulation offers a promising strategy to deliver localized co-stimulation while minimising systemic toxicity. While 4-1BB and CD28 are well-characterized co-stimulatory pathways, their relative efficacy in supporting TCBs remains unclear. We systematically compared 4-1BB and CD28 co-stimulation in the context of the HER2xCD3 TCB (runimotamab), using HER2-4-1BBL and HER2-CD28 tumour-targeted co-stimulatory agonists.

• What are the key advantages of in vivo mRNA-encoded TCEs versus recombinant protein TCEs?
• How might transient mRNA-driven expression alter CRS, ICANS, and on-target/off-tumor toxicity risks?
• What are the major barriers to successful in vivo TCE development: LNP delivery, biodistribution, expression control, immunogenicity, or manufacturability?
• Five years from now, will in vivo mRNA-encoded TCEs complement conventional bispecific antibodies—or fundamentally redefine how T-cell engagers are developed and delivered?"

  
  

Immunotherapy-engineering the immune system to treat diseases such as cancer, neurodegeneration, and autoimmune disorders has been explored for over a century but is only now transforming medicine. Recent years have brought major clinical successes, driven by advances in genomics, synthetic biology, and machine learning. Single-cell genomics is further revolutionising our understanding of immune-related diseases. I will highlight these insights and discuss emerging technologies shaping the future of immunology and immunotherapy.

T cell engagers (TCEs) are limited by suboptimal pharmacokinetics and safety. We present an mRNA-LNP platform enabling in vivo expression of bispecific and trispecific TCEs with tunable exposure and tissue-directed activity. Through sequence and formulation engineering, this approach achieves potent efficacy with improved safety and reduced cytokine release compared to recombinant formats. Preclinical data highlight its potential to expand the therapeutic window in oncology and beyond.

The precision activated bispecific VHHs comprise albumin-binding and T cell receptor-binding VHH domains connected via protease-cleavable linkers, remaining masked in healthy tissues but selectively activated in tumours where disease-associated proteases restore T cell engaging activity. Preclinical data demonstrate >1000-fold increases in T cell activation and cytotoxicity upon protease cleavage, with significant tumor growth inhibition and improved safety profiles compared to conventional T cell engagers.