Applications of Bispecific Antibodies in Therapeutics

Bispecific antibodies (bsAbs) represent a significant advancement in therapeutic antibody technology, simultaneously binding to two different antigens to enable novel treatment mechanisms across multiple disease areas, including oncology, hematology, ophthalmology, and diagnostics.

With several bsAbs already approved by regulatory agencies such as the FDA and many more in clinical development, these molecules are transforming modern medicine. This article explores the mechanisms of action of bsAbs, their current and emerging applications, and the future of bispecific antibody therapeutics.

Mechanisms of Action of Bispecific Antibodies

BsAbs function through various mechanisms depending on their specific design and target antigens. The three primary mechanisms include immune cell recruitment, dual-pathway blockade, and cytokine signaling inhibition.

Immune Cell Recruitment for Targeted Cytotoxicity

One of the most established mechanisms of bsAbs is their ability to recruit immune cells, such as T cells or natural killer (NK) cells, to tumor cells. This is achieved by designing bsAbs with one antigen-binding site targeting a tumor-associated antigen and the other binding site targeting an activating receptor on immune cells.

A well-known example is Blinatumomab (Blincyto), which is approved for treating acute lymphoblastic leukemia (ALL). This bsAb binds to CD19 on malignant B cells and CD3 on T cells, effectively bringing them into close proximity to induce targeted cytotoxicity. This approach enhances the immune system's ability to destroy tumor cells and has shown success in overcoming resistance mechanisms seen in traditional monoclonal antibody therapies.

Blinatumomab is a first-in-class bi-specific antibody and targeted immunotherapy designed for treating B-cell malignancies. Its novel mechanism of action enables in-vivo engagement of a patient’s T cells with CD19-expressing tumor cells. Clinical trials have demonstrated its efficacy in relapsed B-cell Acute Lymphoblastic Leukemia (B-ALL) and B-cell Non-Hodgkin’s Lymphoma, particularly in patients refractory to chemotherapy. Historically, B-ALL and diffuse large B-cell lymphoma (DLBCL) have been treated with multi-agent chemotherapy regimens, with notable success in pediatric B-ALL and DLBCL.¹

Dual Blockade of Signaling Pathways

Another mechanism by which bsAbs exert their effects is by blocking two signaling pathways simultaneously. Many diseases, particularly cancers, involve redundant or compensatory pathways that drive tumor progression. BsAbs can address this challenge by inhibiting two critical pathways at the same time, leading to improved therapeutic efficacy compared to single-target mAbs.

For example, Faricimab (Vabysmo), an FDA-approved bsAb for ophthalmic diseases, simultaneously targets vascular endothelial growth factor A (VEGF-A) and angiopoietin-2 (Ang-2). This dual inhibition improves vascular stability and reduces disease progression in neovascular age-related macular degeneration (nAMD) and diabetic macular edema (DME). Faricimab is the first bispecific antibody (bsAb) approved for ophthalmic use and the only FDA-approved injectable eye medication for both conditions that allows for flexible dosing intervals of up to four months, reducing the need for frequent injections compared to standard therapies.

Vabysmo works by simultaneously targeting and inhibiting two key disease pathways: vascular endothelial growth factor-A (VEGF-A), a primary driver of abnormal blood vessel growth and leakage in retinal diseases, and angiopoietin-2 (Ang-2), a factor that destabilizes blood vessels and contributes to inflammation and vascular leakage. By blocking both pathways, Vabysmo helps stabilize blood vessels, reduce leakage, and control inflammation, effectively preserving vision in patients with nAMD and DME.²

Cytokine Signaling Inhibition in Autoimmune Diseases

In autoimmune and inflammatory diseases, excessive cytokine signaling contributes to disease pathology. BsAbs designed to block multiple cytokines or their receptors can provide a more effective therapeutic approach than single-target therapies. By neutralizing multiple inflammatory mediators, bsAbs help reduce disease severity and prevent long-term tissue damage.

Advances in recombinant DNA technology enable precise engineering of bsAbs with optimal binding affinities and pharmacokinetic properties. Production techniques, such as transient or stable transfection in Chinese hamster ovary (CHO) cells, ensure the efficient generation of high-quality bispecific antibodies for clinical applications.

Therapeutic Applications of Bispecific Antibodies

BsAbs are revolutionizing multiple fields of medicine, providing innovative solutions where conventional therapies have limitations. Their ability to target multiple molecules simultaneously enhances treatment efficacy across oncology, hematology, ophthalmology, and diagnostics.

Oncology: Tumor Targeting and Immune Activation

Cancer therapy remains the leading field for bsAb development. BsAbs improve upon traditional mAb-based cancer therapies by enhancing immune system activation and overcoming resistance mechanisms.

T-Cell Engagers (TCEs) in Hematologic Malignancies: T-cell engaging bsAbs, such as Blinatumomab, are transforming the treatment of hematologic malignancies by redirecting T cells toward cancer cells. Blinatumomab’s ability to bind both CD19 on malignant B cells and CD3 on T cells has shown significant efficacy in B-cell precursor ALL, particularly in patients with minimal residual disease.

Dual-Targeting in Solid Tumors: BsAbs are also being developed for solid tumors to target tumor antigens while simultaneously engaging the immune system. For instance, bsAbs targeting PD-L1 and CTLA-4 enhance immune checkpoint blockade, providing a more comprehensive anti-tumor immune response.

BsAbs are also employed to inhibit angiogenesis by simultaneously blocking VEGF and other angiogenic factors, preventing tumor growth by disrupting its blood supply.

Related: Bispecific Antibody Production

Hematology: Clotting Disorders

In hematology, bsAbs offer novel solutions for coagulation disorders, particularly hemophilia A.

Emicizumab (Hemlibra) for Hemophilia A: Patients with hemophilia A lack functional Factor VIII, a crucial protein for blood clotting. Emicizumab, an FDA-approved bsAb, bridges activated Factor IX and Factor X, mimicking the function of Factor VIII to restore proper clotting. This approach has significantly reduced bleeding episodes and improved patient outcomes.

Hemophilia A, characterized by FVIII deficiency, leads to significant morbidity due to impaired coagulation, requiring ongoing prophylaxis and acute bleeding treatment. Traditional FVIII replacement involves frequent intravenous dosing, which poses challenges for patients. Emicizumab, approved by the FDA in 2017, addresses these issues by providing a standardized prophylactic option for patients with and without FVIII inhibitors. It functions by mimicking activated FVIII, bridging activated Factor IX (FIXa) and Factor X (FX) to facilitate coagulation independently of FVIII levels. Administered subcutaneously, Emicizumab has demonstrated favorable pharmacokinetics with a long elimination half-life of approximately 27 days, allowing for less frequent dosing regimens. Its introduction has improved bleeding control and patient adherence while requiring careful coordination among healthcare professionals to manage potential adverse events, laboratory interferences, and optimize treatment outcomes.³

BsAbs are also under investigation for other hematological conditions, including immune thrombocytopenia (ITP) and sickle cell disease, where multi-targeted approaches could improve disease management.

Related: Bispecific Antibodies for In Vivo Research

Ophthalmology: Retinal Disease Treatment

In ophthalmology, mAbs have become essential for managing a variety of sight-threatening diseases, including age-related macular degeneration (AMD), diabetic retinopathy, and uveitis. These biologic agents function by targeting specific molecules involved in pathological processes, such as vascular endothelial growth factor (VEGF), which plays a central role in abnormal blood vessel growth and leakage in retinal diseases. Anti-VEGF mAbs, such as bevacizumab, ranibizumab, and aflibercept, have dramatically improved visual outcomes by reducing neovascularization and stabilizing the retina in conditions like AMD and diabetic macular edema.

Beyond VEGF inhibition, mAbs are also being explored for inflammatory eye diseases, with drugs like adalimumab targeting tumor necrosis factor-alpha (TNF-α) to treat non-infectious uveitis. The development of chimeric, humanized, and fully human mAbs has minimized immunogenicity risks while enhancing efficacy and patient tolerance. Furthermore, emerging research suggests that mAbs could play a role in addressing viral infections affecting the eye, such as SARS-CoV-2-associated conjunctivitis.⁴

BsAbs are emerging as a promising class of therapies for complex eye diseases such as nAMD and DME, which are leading causes of blindness.

Faricimab (Vabysmo) represents a major breakthrough in retinal disease treatment. By targeting VEGF-A (a key driver of abnormal blood vessel growth) and Ang-2 (a regulator of vascular destabilization), Faricimab provides better disease control compared to anti-VEGF monotherapies. This dual inhibition reduces vascular leakage, inflammation, and fibrosis, prolonging treatment intervals and reducing the treatment burden for patients.

Diagnostics: Improving Biomarker Detection

BsAbs are also playing an increasing role in diagnostic applications, offering specificity and sensitivity in biomarker detection. They can be engineered to recognize two biomarkers simultaneously, increasing the accuracy of diagnostic tests. This approach is particularly useful in early cancer detection, where multiple markers may be indicative of disease progression.

For example, bsAbs targeting prostate-specific antigen (PSA) and an additional tumor marker can improve prostate cancer diagnosis by reducing false positives and negatives. Meanwhile, antibodies such as LY3164530, a bispecific anti-EGFR/c-MET antibody, disrupts signaling by targeting both receptors though faces limitations due to significant toxicities and a lack of predictive biomarkers. Amivantamab (JNJ-61186372), another bispecific EGFR/c-MET antibody, has shown efficacy against tumors with EGFR T790M resistance mutations, c-MET pathway activation, and EGFR exon 20 insertion mutations. It is being tested in multiple clinical trials and has been approved for treating metastatic NSCLC patients with EGFR exon 20 insertion mutations who have developed resistance to platinum-based chemotherapy.⁵

Future Perspectives

The pipeline for bsAbs continues to grow, with over 200 bsAbs currently in clinical development. Future applications include:

• Autoimmune diseases: Targeting multiple inflammatory mediators in conditions like rheumatoid arthritis and multiple sclerosis.

• Infectious diseases: Developing bsAbs to neutralize multiple viral antigens for HIV and SARS-CoV-2.

• Neurodegenerative disorders: Targeting multiple amyloidogenic proteins in Alzheimer’s disease.

Advances in recombinant antibody expression systems, including CHO cell-based production, will further improve the scalability and accessibility of bsAbs for both research and therapeutic applications.

Companies specializing in custom bispecific antibody production like Biointron are playing a key role in accelerating these advancements. By leveraging expertise in antibody engineering and rapid expression technologies, researchers and pharmaceutical companies can efficiently develop bsAbs for diverse applications.

At Biointron, we are dedicated to accelerating antibody discovery, optimization, and production. Our team of experts can provide customized solutions that meet your specific research needs, including Bispecific Antibody Production. Contact us to learn more about our services and how we can help accelerate your research and drug development projects.

References:

1. Burt, R., Warcel, D., & Fielding, A. K. (2018). Blinatumomab, a bispecific B-cell and T-cell engaging antibody, in the treatment of B-cell malignancies. Human Vaccines & Immunotherapeutics, 15(3), 594. https://doi.org/10.1080/21645515.2018.1540828

2. Roche. (2022, January 30). FDA approves Roche’s Vabysmo, the first bispecific antibody for the eye, to treat two leading causes of vision loss. Roche.com. https://www.roche.com/investors/updates/inv-update-2022-01-31

3. Parisi, K., & Kumar, A. (2023, July 4). Emicizumab. Nih.gov; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK559180/

4. Henriques, C., Da Ana, R., Krambeck, K., Miguel, S., Santini, A., Zielińska, A., & Souto, E. B. (2024). Monoclonal Antibodies for the Treatment of Ocular Diseases. Journal of Clinical Medicine, 13(19), 5815. https://doi.org/10.3390/jcm13195815

5. Zhou, Y., Tao, L., Qiu, J., Xu, J., Yang, X., Zhang, Y., Tian, X., Guan, X., Cen, X., & Zhao, Y. (2024). Tumor biomarkers for diagnosis, prognosis and targeted therapy. Signal Transduction and Targeted Therapy, 9(1), 1-86. https://doi.org/10.1038/s41392-024-01823-2