In biopharmaceutical R&D, the development of candidate molecules is always accompanied by major scientific challenges and clinical translation risks, among which off-target binding has drawn increasing attention due to its potential clinical impact. Antibody drugs, as highly specific biologics, rely on precise targeting to determine their therapeutic window. However, due to the molecular complexity of biological systems (including protein homology and conformational polymorphism), antibody molecules may cross-react with unintended targets—this phenomenon is called polyspecific binding. This not only can severely reduce drug efficacy but, more seriously, can cause a range of unpredictable adverse effects, from mild discomfort to life-threatening toxic reactions, posing great risks to patients. Examples include severe adverse reactions (such as organ toxicity, cytokine storms), decreased efficacy (antibodies consumed by off-target binding), and clinical trial termination (regulatory halts).
For example, SHR-1210, an anti-PD1 antibody, unexpectedly caused severe capillary hemangiomas in a Phase 1 clinical trial. Studies linked these adverse events to its off-target binding to VEGFR2; SHR-1210 not only bound VEGFR2 but also acted as an agonist promoting angiogenesis, which led to capillary hemangiomas in vivo. In another non-human primate study, development of the anti-β-amyloid antibody ABT-736 was halted due to severe toxicity caused by off-target binding to platelet factor 4 in rhesus monkeys. In the long and arduous journey of antibody drug development, off-target effects are like hidden reefs that can cause the development ship to wreck at any time, significantly increasing R&D costs and failure risk. Therefore, accurately detecting and assessing antibody off-target effects early in development has become a critical issue urgently needing resolution in biopharmaceutical research.
The U.S. company Integral Molecular, in the paper “The emergence of cell-based protein arrays to test for polyspecific off-target binding of antibody therapeutics,” thoroughly discusses the application of cell-based protein array technology in antibody off-target screening, providing innovative ideas for safety assessment in antibody drug development. Kyinno Biotechnology’s MPSA – AB5000 membrane protein engineering screening platform also shines in this key area, echoing Integral Molecular’s philosophy and helping to tackle antibody off-target challenges from a unique perspective.
MPSA – AB5000 Platform: A Powerful Weapon Against Off-Target Issues
Kyinno Biotechnology has launched the MPSA – AB5000 membrane protein engineering screening platform, offering a comprehensive and efficient solution for antibody specificity screening and antigen recognition specificity evaluation of CAR-modified immune cells. The MPSA – AB5000 platform has distinct technical advantages. Compared with traditional detection methods such as flow cytometry, frozen tissue immunohistochemistry, ELISA, and protein arrays, it uses a reporter cell line system and a no-wash protocol, avoiding false negatives caused by extensive washing steps in traditional methods when detecting biologics with weak target binding. Its sensitivity surpasses that of FACS and similar technologies. Meanwhile, the system’s signal amplification strongly detects weak receptor-ligand interactions, effectively distinguishing even weak bindings like PD1 and PDL1 with dissociation constants in the micromolar range. Furthermore, when potential off-target binding signals are initially detected, systematic verification is conducted through cross-validation experimental strategies such as FACS and even ELISA confirmation. Additionally, as a cell-based off-target detection platform, background noise is optimized by using 293T gene knockout (KO) cells to eliminate non-specific binding interference. Kyinno Biotechnology has established an industry-leading 293T knockout cell library covering numerous key targets: immune checkpoint molecules (e.g., B7H3), tumor-associated antigens (e.g., HER2, EGFR), and signaling pathway node proteins, among others.
For CAR-modified immune cell therapy testing, the MPSA – AB5000 platform expresses the CAR on reporter cells, performing specificity detection directly at the cellular level. This highly simulates the actual mechanism of CAR-modified immune cell therapies and, compared to the traditional method of producing CAR fusion proteins, more accurately reflects the CAR’s specificity performance in real applications.
Successful Cases and Wide Applications
As the only company in China providing membrane protein screening and specificity evaluation services for biotherapeutic drug binding, Kyinno Biotechnology has successfully completed over 100 antibody drug and CAR protein specificity evaluation projects in the past year, demonstrating the reliability and effectiveness of the MPSA – AB5000 platform in practice. Among these projects, the off-target rate reached as high as 30%, underscoring the severity of the off-target problem and highlighting the critical value of the MPSA – AB5000 platform in early detection and mitigation of off-target risks. According to a 2024 retrospective analysis by U.S. Integral Molecular of 254 preclinical candidate samples, 83 showed polyspecific off-target binding, with an off-target rate as high as 33%.
The application scope of the MPSA – AB5000 membrane protein off-target screening platform is broad. It is not only used for antibody specificity screening and CAR-modified immune cell antigen recognition specificity evaluation but also plays an important role in drug target discovery and validation. Whether in the development of innovative antibody drugs or optimization of CAR-T cell therapies, this platform provides robust technical support for researchers and biopharmaceutical companies. We look forward to partnering with you to explore the unlimited potential of biopharmaceutical R&D!
Case 1: VHH Antibody
Case 2: CLDN18.2 mAb
