Pre-clinical characterisation of E2814, a high-affinity antibody targeting the microtubule-binding repeat domain of tau for passive immunotherapy in Alzheimer’s disease

Abstract

Tau deposition in the brain is a pathological hallmark of many neurodegenerative disorders, including Alzheimer’s disease (AD). During the course of these tauopathies, tau spreads throughout the brain via synaptically-connected pathways. Such propagation of pathology is thought to be mediated by tau species (“seeds”) containing the microtubule binding region (MTBR) composed of either three repeat (3R) or four repeat (4R) isoforms. The tau MTBR also forms the core of the neuropathological filaments identified in AD brain and other tauopathies. Multiple approaches are being taken to limit tau pathology, including immunotherapy with anti-tau antibodies. Given its key structural role within fibrils, specifically targetting the MTBR with a therapeutic antibody to inhibit tau seeding and aggregation may be a promising strategy to provide disease-modifying treatment for AD and other tauopathies. Therefore, a monoclonal antibody generating campaign was initiated with focus on the MTBR. Herein we describe the pre-clinical generation and characterisation of E2814, a humanised, high affinity, IgG1 antibody recognising the tau MTBR. E2814 and its murine precursor, 7G6, as revealed by epitope mapping, are antibodies bi-epitopic for 4R and mono-epitopic for 3R tau isoforms because they bind to sequence motif HVPGG. Functionally, both antibodies inhibited tau aggregation in vitro. They also immunodepleted a variety of MTBR-containing tau protein species. In an in vivo model of tau seeding and transmission, attenuation of deposition of sarkosyl-insoluble tau in brain could also be observed in response to antibody treatment. In AD brain, E2814 bound different types of tau filaments as shown by immunogold labelling and recognised pathological tau structures by immunohistochemical staining. Tau fragments containing HVPGG epitopes were also found to be elevated in AD brain compared to PSP or control. Taken together, the data reported here have led to E2814 being proposed for clinical development.

Inhibition of Tau seeding by targeting Tau nucleation core within neurons with a single domain antibody fragment

“…Similarly, treatment with a humanized IgG antibody, binding the R2 and R4 repeats within the MTBD, decreases the level of sarkosyl-insoluble Tau in brain of a mouse model of Tau seeding 56 . VHH Z70 has similar properties but by acting directly intracellularly.…”

Bispecific tau antibodies with additional binding to C1q or alpha-synuclein

“…Antibody 3E8-1A6 binds to one of the two hexapeptides in the repeat domain of tau, which are supposed to be responsible for aggregation [7, 8]. This antibody was selected because antibodies targeting this domain were previously shown to potently inhibit recombinant tau aggregation in similar assays [45, 63]. Negative control antibody 2B11, which only recognizes tau phosphorylated at threonine 231 (absent on recombinant tau), did not reduce tau aggregation (Figure 4B)…”

Aggregated Tau-PHF6 (VQIVYK) Potentiates NLRP3 Inflammasome Expression and Autophagy in Human Microglial Cells

“…The failure of Aβ-targeted therapeutic approaches has led to a shift of the focus on tau-targeted strategies [ 48 ] and, more specifically, on PHF6 in recent years [ 49 ]. A growing body of literature suggests the potential role of microglia in the spread of tau throughout the brain [ 24 , 25 ].…”