Application of 89Zr-DFO*-immuno-PET to assess improved target engagement of a bispecific anti-amyloid-ß monoclonal antibody

Abstract

Purpose The recent conditional FDA approval of Aducanumab (Adu) for treating Alzheimer’s disease (AD) and the continued discussions around that decision have increased interest in immunotherapy for AD and other brain diseases. Reliable techniques for brain imaging of antibodies may guide decision-making in the future but needs further development. In this study, we used 89Zr-immuno-PET to evaluate the targeting and distribution of a bispecific brain-shuttle IgG based on Adu with transferrin receptor protein-1 (TfR1) shuttling mechanism, mAbAdu-scFab8D3, designated Adu-8D3, as a candidate theranostic for AD. We also validated the 89Zr-immuno-PET platform as an enabling technology for developing new antibody-based theranostics for brain disorders. Methods Adu, Adu-8D3, and the non-binding control construct B12-8D3 were modified with DFO*-NCS and radiolabeled with 89Zr. APP/PS1 mice were injected with 89Zr-labeled mAbs and imaged on days 3 and 7 by positron emission tomography (PET). Ex vivo biodistribution was performed on day 7, and ex vivo autoradiography and immunofluorescence staining were done on brain tissue to validate the PET imaging results and target engagement with amyloid-β plaques. Additionally, [89Zr]Zr-DFO*-Adu-8D3 was evaluated in 3, 7, and 10-month-old APP/PS1 mice to test its potential in early stage disease. Results A 7-fold higher brain uptake was observed for [89Zr]Zr-DFO*-Adu-8D3 compared to [89Zr]Zr-DFO*-Adu and a 2.7-fold higher uptake compared to [89Zr]Zr-DFO*-B12-8D3 on day 7. Autoradiography and immunofluorescence of [89Zr]Zr-DFO*-Adu-8D3 showed co-localization with amyloid plaques, which was not the case with the Adu and B12-8D3 conjugates. [89Zr]Zr-DFO*-Adu-8D3 was able to detect low plaque load in 3-month-old APP/PS1 mice. Conclusion 89Zr-DFO*-immuno-PET revealed high and specific uptake of the bispecific Adu-8D3 in the brain and can be used for the early detection of Aβ plaque pathology. Here, we demonstrate that 89Zr-DFO*-immuno-PET can be used to visualize and quantify brain uptake of mAbs and contribute to the evaluation of biological therapeutics for brain diseases.

[125I]IPC-Lecanemab: Synthesis and Evaluation of Aβ-Plaque-Binding Antibody and Comparison with Small-Molecule [18F]Flotaza and [125I]IBETA in Postmortem Human Alzheimer’s Disease

“…This lack of brain uptake by the radiolabeled antibody is consistent with the observation of [ 125 I]RmAb158, which is unable to permeate the BBB [32]. [ 89 Zr]DFO-Adu-8D3 using the transferrin receptor to shuttle it across the BBB has therefore been used to successfully to image Aβ plaques in APP/PS1 mice brain [41]. Focused ultrasound is emerging as a viable alternative to temporarily make the BBB permeable for drug delivery, while mechanisms and safety investigations in preclinical Focused ultrasound is emerging as a viable alternative to temporarily make the BBB permeable for drug delivery, while mechanisms and safety investigations in preclinical and clinical use still continue to be evaluated [42][43][44].…”

“…This lack of brain uptake by the radiolabeled antibody is consistent with the observation of [ 125 I]RmAb158, which is unable to permeate the BBB [32]. [ 89 Zr]DFO-Adu-8D3 using the transferrin receptor to shuttle it across the BBB has therefore been used to successfully to image Aβ plaques in APP/PS1 mice brain [41].…”

Good practices for 89Zr radiopharmaceutical production and quality control

“…This advancement enables repeated patient scans and provides safer conditions for healthy control groups in clinical trials. Also, it further extends the applicability of 89 Zr-immuno-PET to targets with low abundance that would otherwise necessitate disproportionate amounts of injected radioactivity (Stergiou et al 2023 ).…”

Indium-111 radiolabelling of a brain-penetrant Aβ antibody for SPECT imaging

“…Previous research has also demonstrated high brain uptake of 111 In-labelled TfR targeting antibodies in wild-type mice ( 29 ). In addition, Aβ/TfR bispecific antibodies radiolabelled with zirconium-89 have also demonstrated a relatively high background signal in wild-type mice and a smaller difference in brain retention between Aβ-expressing and wild-type mice compared to radioiodinated versions ( 30 , 31 ). Multiple mechanisms could explain the prolonged retention of 111 In (and other radiometals) in the wild-type mouse brain.…”