Development of phospho-tau specific antibodies: Validation and engineering of specificity
July 14-18, 2019
Neurodegenerative disease is a widespread and growing burden with no disease-modifying treatment option. As we gain more knowledge on the source of neurotoxicity, monoclonal antibody-based drugs are actively being pursued as a treatment for neurodegeneration. Moreover, antibodies for detecting trace amounts of biomarker proteins in the cerebrospinal fluid and blood have shown promise in early detection and monitoring of neurodegeneration. However, as evidenced by recent failures in clinical trials of amyloid targeting antibodies, development of a translatable drug for neurodegeneration is extremely challenging. A major hurdle to overcome is the validation and improvement of specificity towards targets that play a causal role in neurotoxicity. In this regard, the microtubule-associated protein tau and its disease-specific post-translational modification (PTM) sites have emerged as a promising target. Disease-specific PTMs appear prior to and drive the formation of tau oligomers, which have been identified as a key source of toxicity. A major clinical trial is underway with a tau monoclonal antibody targeting phosphorylated tau. However, efforts to validate the specificity of these antibodies has been scarce. An alarming and widespread lack of specificity in PTM-targeting antibodies has only recently been noticed. More importantly, we have lacked the capability to improve antibody specificity even when the source of non-specific binding has been uncovered. This presentation will address our recent efforts to meet this urgent need by applying protein engineering approaches to identify high specificity antibodies targeting disease-specific PTM sites in the tau protein. Starting from a structure-based understanding of specificity in PTM-specific antibodies, I will describe our recent work on developing a quantitative parameter for measuring antibody specificity, in vitro directed evolution strategies to identify high specificity antibody variants, and new antibody library screening strategies to discover PTM-specific antibodies. We find that antibody screening approaches that focus solely on affinity improvements likely result in antibody clones that have cross-reactivity towards the non-phosphorylated target. Multi-parameter screens that can measure specificity and affinity were essential in obtaining high quality antibodies that greatly improved phospho-tau detection in human patient samples . These antibodies are invaluable tools for early detection of neurodegeneration, and highlight the importance of specificity validation and engineering in PTM-targeting antibodies. References 1. Li, D., L. Wang, B.F. Maziuk, X. Yao, B. Wolozin, and Y.K. Cho, Directed evolution of a picomolar-affinity, high-specificity antibody targeting phosphorylated tau. J Biol Chem, 2018. 293(31): p. 12081-12094.
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Yongku P. Cho and Dan Li, "Development of phospho-tau specific antibodies: Validation and engineering of specificity" in "Biochemical and Molecular Engineering XXI", Christina Chan, Michigan State University, USA Mattheos Koffas, RPI, USA Steffen Schaffer, Evonik Industries, Germany Rashmi Kshirsagar, Biogen, USA Eds, ECI Symposium Series, (2019). https://dc.engconfintl.org/biochem_xxi/120