AD Immunotherapy with a Novel CDC-Mutant Anti-Pyroglutamate-3 Abeta Antibody to Avoid Vascular Side Effects

Lemere, Cynthia

Abstract

N-terminally-truncated and modified amyloid-beta (A?) peptides are abundant in cerebral amyloid deposits in Alzheimer's disease (AD). Pyroglutamate3 A? (pyroGlu3 A?) is generated upon N-terminal truncation of A? followed by cyclization by glutaminyl cyclase to convert glutamic acid at residue 3 to pyroGlu3 A?, which aggregates quickly, resists degradation, and is neurotoxic. AD progression appears to correlate with the presence of pyroGlu3 A? peptide aggregates in brain. Growing evidence, including our own, indicates that pyroGlu3 A? acts as a seed for A? deposition and accelerates inflammation, neurodegeneration and cognitive decline; therefore, targeted removal of this toxic species by immunotherapy will reduce A? deposition, inflammation and neuritic dystrophy, and protect cognition. We have demonstrated that targeted removal of pathogenic pyroGlu3 A? by immunotherapy using an anti-pyroGlu3 A? IgG1 mAb (07/1) in a prevention study and the IgG2a version of the same antibody (07/2a) in a therapeutic study, reduced pyroGlu3 A? and general (non-pyroGlu3) A?, suggesting that pyroGlu3 A? acts as a seed for A? deposition. Furthermore, the anti- pyroGlu3 A? mAbs protected cognition. Together with Probiodrug AG, we have developed a CDC-mutant (K332A) version of the 07/2a mAb (07/2a-k) to avoid vascular inflammation observed in clinical trials using plaque binding A? antibodies. Here, we propose the following hypotheses: 1. 07/2a-k, a novel murine anti- pyroGlu3 IgG2a CDC-mutant antibody, will effectively reduce plaques and protect cognition while avoiding potential inflammatory vascular side effects in APP/E4 mice that are prone to vascular amyloid and microhemorrhages; 2. Microglia will have a less inflammatory response to 07/2-k exposure. 3. 07/2a-k antibody will neutralize the toxic effects of pyroGlu3 A? on neurons (in vitro). Our collaborators at Probiodrug AG (Halle, Germany) will provide us with 4 high-affinity, highly selective pyroGlu A? mAbs (including 07/2a-k, the CDC mutant version of 07/2a) and an Asp1 3D6-mimic (3D6-L), identical to the murine precursor to bapineuzumab, which led to vascular inflammation in clinical trials. The goal is to determine whether passive immunotherapy with the novel CDC-mutant anti-pyroGlu3 A? mAb (07/2a-k) is safe and effective in a relevant pre-clinical animal model as a prelude to a clinical trial for AD.

Public Health Relevance

Previously, we demonstrated both preventive and therapeutic efficacy of an anti-pyroglutamate-3 amyloid-? monoclonal antibody (mAb) to lower plaque burden and spare cognition. Here, we propose to characterize and test the efficacy of a CDC-mutant form of the anti-pyroGlu3 A? IgG2a mAb developed to avoid inflammation in the brain and reduce the vascular side effects (e.g., vasogenic edema; microhemorrhage) seen in human A? immunotherapy trials in AD mice with humanized Apo E4, the Apo E genotype at highest risk for these side effects in human clinical trials.