The first MultiTEP‐based conjugated vaccine targeting pyroglutamated pE3‐Aβ is immunogenic and effective in a 5xFAD animal model

Background Many ongoing studies for AD immunotherapy are focused on the immunodominant N‐terminus of Aβ. This region is often truncated and post‐translationally modified in amyloid. The pyroglutamate modified variant of Aβ 40/42 (pE3‐Aβ) is more neurotoxic and aggregation‐prone and is thought to play an important role in disease onset. We have previously demonstrated that our proprietary vaccine platform MultiTEP is extremely immunogenic in various mammals, including disease models of AD and aged monkeys, and can be used to generate a robust immune response towards various targets. Based on these we developed a MutiTEP‐based vaccine targeting pE3‐Aβ. Method A genetically engineered variant of MultiTEP was generated to enable chemoselective bioconjugation of synthetic peptides under mild aqueous conditions. The peptide‐protein stoichiometry was selected at 3:1 based on previous data. C57Bl6 and 5xFAD mice were monthly immunized with pE3‐Aβ‐MultiTEP adjuvanted vaccine, AV‐1986R. Antibody titers were tested via ELISA on plates coated with pE3‐Aβ42 and unmodified Aβ42 as control. The reduction of brain pathology in 5xFAD was assessed via biochemical assessment (MSD ELISA) as well as IHC and confocal microscopy using various commercial antibodies. The binding of immune sera to brain sections from non‐AD, MCI, and AD cases was examined. Result The AV‐1986R generates a robust immune response in transgenic and WT mice after two immunizations. The generated antibodies exhibit three orders of magnitude higher affinity (one to a million avg endpoint titer) to the pE3‐Aβ compared to Aβ 42 and recognized Aβ plaques in brain tissue slices from both transgenic animals and AD cases. Importantly, vaccination significantly reduced AD‐like pathology in 5xFAD mice. Conclusion AV‐1986R is immunogenic and effective. A recent report from Elly‐Lilly about the pE3‐Aβ specific monoclonal antibody donanemab shows that treatment slows down the cognitive decline in humans. While this is promising and re‐affirms the selection of pE3‐Aβ as a therapeutic target, the regular injections of monoclonal antibodies are extremely expensive and have low patient compliance due to the frequent and invasive nature of the treatment. We suggest using active vaccine as a feasible alternative, allowing the maintenance of a constant level of therapeutic antibodies with minimal costs and infrequent vaccine injections.