ABSTRACT
BACKGROUND: Immunotherapy targeting the amyloid-ß (Aß) peptide is a promising strategy for the treatment of Alzheimer's disease (AD); however, none of the active or passive vaccines tested have been demonstrated to be effective to date. We have developed the first active vaccine against the C-terminal end of Aß40, ABvac40, and assessed its safety and tolerability in a phase I clinical trial. METHODS: A randomised, double-blind, placebo-controlled, parallel-group, phase I study of ABvac40 was conducted with patients aged 50-85 years with mild to moderate AD. Participants were entered into three separate groups according to time of study entry and were randomly allocated to receive ABvac40 or placebo (overall ratio 2:1). The first group received two half-doses of ABvac40 or placebo, whereas the second and third groups received two and three full doses, respectively. All treatments were administered subcutaneously at 4-week intervals. Patients, carers and investigators were blind to treatment allocation throughout the study. The primary objective was to assess the safety and tolerability of ABvac40 by registering all adverse events (AEs). All patients who received at least one dose of treatment were included in the safety analysis. The secondary objective was to evaluate the immunogenicity of ABvac40 by titration of specific anti-Aß40 antibodies in plasma. RESULTS: Twenty-four patients were randomly allocated: 16 patients to the ABvac40 group and 8 patients to the placebo group. All randomised patients completed the study, therefore the intention-to-treat and safety populations were identical. Overall, 71 AEs affecting 18 patients were recorded: 11 (69%) in the ABvac40 group and 7 (88%) in the placebo group (p = 0.6214). Neither incident vasogenic oedema nor sulcal effusion (amyloid-related imaging abnormalities corresponding to vasogenic oedema and sulcal effusions) nor microhaemorrhages (amyloid-related imaging abnormalities corresponding to microhaemorrhages and hemosiderin deposits) were detected throughout the study period in the ABvac40-treated patients. Eleven of 12 (~92%) individuals receiving three injections of ABvac40 developed specific anti-Aß40 antibodies. CONCLUSIONS: ABvac40 showed a favourable safety and tolerability profile while eliciting a consistent and specific immune response. An ongoing phase II clinical trial is needed to confirm these results and to explore the clinical efficacy of ABvac40. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03113812 . Retrospectively registered on 14 April 2017.
Subject(s)
Alzheimer Disease/immunology , Alzheimer Disease/therapy , Alzheimer Vaccines/therapeutic use , Amyloid beta-Peptides/immunology , Immunogenicity, Vaccine , Peptide Fragments/immunology , Aged , Aged, 80 and over , Alzheimer Disease/blood , Alzheimer Vaccines/adverse effects , Double-Blind Method , Female , Follow-Up Studies , Humans , Male , Middle Aged , Protein Domains , Severity of Illness Index , Treatment OutcomeABSTRACT
The two pathognomonic lesions in the brain of AD patients are senile plaques and intraneuronal neurofibrillary tangles (NFT). Previous studies have demonstrated that amyloid-ß (Aß) is a component of both senile plaques and NFTs, and have showed that intracellular accumulation of Aß is toxic for cells and precedes the appearance of extracellular amyloid deposits. Here we report that there are numerous intraneuronal NFT and extraneuronal NFT immunoreactive for Aßx-40 in which there is no co-localization with tau staining suggesting the existence of two different neurodegenerating populations associated with the intracellular accumulation of either tau protein or Aßx-40 in AD.
