Investigation of the Impact of the H310A FcRn Region Mutation on 89Zr-Immuno-PET Brain Imaging with a BBB-Shuttle Anti‑Amyloid Beta Antibody

Mol Imaging Biol. 2024 Oct;26(5):823-834. doi: 10.1007/s11307-024-01931-z. Epub 2024 Aug 2.

Abstract

Purpose: In the emerging field of antibody treatments for neurodegenerative diseases, reliable tools are needed to evaluate new therapeutics, diagnose and select patients, monitor disease progression, and assess therapy response. Immuno-PET combines the high affinity and exceptional specificity of monoclonal antibodies with the non-invasive imaging technique positron emission tomography (PET). Its application in neurodegenerative disease brain imaging has been limited due to the marginal uptake across the blood-brain barrier (BBB). The emergence of BBB-shuttle antibodies with enhanced uptake across the BBB extended immuno-PET to brain imaging. We recently reported about specific brain uptake of a bispecific aducanumab mTfR antibody in APP/PS1 TG mice using 89Zr-immuno-PET. However, a sufficient target-to-background ratio was reached at a relatively late scanning time point of 7 days post-injection. To investigate if a better target-to-background ratio could be achieved earlier, an aducanumab BBB-shuttle with a mutated Fc region for reduced FcRn affinity was evaluated.

Procedures: AduH310A-8D3 and Adu-8D3 were modified with DFO*-NCS and subsequently radiolabeled with 89Zr. The potential influence of the H310A mutation, modification with DFO*-NCS, and subsequent radiolabeling on the in vitro binding to amyloid-beta and mTfR1 was investigated via amyloid-beta peptide ELISA and FACS analysis using mTfR1 transfected CHO-S cells. Blood kinetics, brain uptake, in vivo PET imaging and target engagement of radiolabeled AduH310A-8D3 were evaluated and compared to non-mutated Adu-8D3 in APP/PS1 TG mice and wild-type animals as controls.

Results: Radiolabeling was performed with sufficient radiochemical yields and radiochemical purity. In vitro binding to amyloid-beta and mTfR1 showed no impairment. [89Zr]Zr-AduH310A-8D3 showed faster blood clearance and earlier differentiation of amyloid-beta-related brain uptake compared to [89Zr]Zr-Adu-8D3. However, only half of the brain uptake was observed for [89Zr]Zr-AduH310A-8D3.

Conclusions: Although a faster blood clearance of AduH310A-8D3 was observed, it was concluded that no beneficial effects for 89Zr-immuno-PET imaging of brain uptake were obtained.

Keywords: 89Zr-immuno-PET; Aducanumab; Amyloid-beta; BBB-shuttle; FcRn; H310A; Transferrin receptor.

MeSH terms

  • Amyloid beta-Peptides* / metabolism
  • Animals
  • Antibodies, Monoclonal / chemistry
  • Antibodies, Monoclonal / pharmacokinetics
  • Antibodies, Monoclonal, Humanized / chemistry
  • Antibodies, Monoclonal, Humanized / pharmacokinetics
  • Blood-Brain Barrier* / metabolism
  • Brain* / diagnostic imaging
  • Brain* / metabolism
  • CHO Cells
  • Cricetulus
  • Histocompatibility Antigens Class I / metabolism
  • Humans
  • Mice
  • Mice, Transgenic
  • Mutation*
  • Positron-Emission Tomography* / methods
  • Radioisotopes* / chemistry
  • Receptors, Fc / metabolism
  • Tissue Distribution
  • Zirconium* / chemistry

Substances

  • Zirconium
  • Radioisotopes
  • Zirconium-89
  • Amyloid beta-Peptides
  • Receptors, Fc
  • Histocompatibility Antigens Class I
  • Antibodies, Monoclonal, Humanized
  • Antibodies, Monoclonal
  • aducanumab