A Distinct Advantage to Intraarterial Delivery of 89Zr-Bevacizumab in PET Imaging of Mice With and Without Osmotic Opening of the Blood-Brain Barrier

Abstract

Glioblastoma multiforme (GBM) is the most aggressive and common type of brain cancer. Five-year survival rates are below 12%, even with the most aggressive trimodal therapies. Poor blood-brain barrier (BBB) permeability of therapeutics is a major obstacle to efficacy. Intravenous administration of bevacizumab is the standard treatment for GBM. It has been recently demonstrated that a single intraarterial infusion of bevacizumab provides superior therapeutic outcomes in patients with recurrent GBM. Further GBM treatment benefits can be achieved through opening of the BBB before intraarterial infusion of bevacizumab. However, a rationale for intraarterial delivery and BBB opening when delivering antibodies is lacking. A method facilitating quantification of intraarterial delivery of bevacizumab is needed for more effective and personalized GBM treatment. Here, we demonstrate such a method using PET imaging of radiolabeled bevacizumab. Methods: Bevacizumab was conjugated with deferoxamine and subsequently radiolabeled with ⁸⁹Zr. ⁸⁹Zr-bevacizumab deferoxamine (⁸⁹Zr-BVDFO) was prepared with a specific radioactivity of 81.4 ± 7.4 MBq/mg (2.2 ± 0.2 μCi/mg). Brain uptake of ⁸⁹Zr-BVDFO on carotid artery and tail vein infusion with an intact BBB or with BBB opening with mannitol was initially monitored by dynamic PET, followed by whole-body PET/CT at 1 and 24 h after infusion. Th ex vivo biodistribution of ⁸⁹Zr-BVDFO was also determined. Results: Intraarterial administration of ⁸⁹Zr-BVDFO resulted in gradual accumulation of radioactivity in the ipsilateral hemisphere, with 9.16 ± 2.13 percentage injected dose/cm³ at the end of infusion. There was negligible signal observed in the contralateral hemisphere. BBB opening with mannitol before intraarterial infusion of ⁸⁹Zr-BVDFO resulted in faster and higher uptake in the ipsilateral hemisphere (23.58 ± 4.46 percentage injected dose/cm³) and negligible uptake in the contralateral hemisphere. In contrast, intravenous infusion of ⁸⁹Zr-BVDFO and subsequent BBB opening did not lead to uptake of radiotracer in the brain. The ex vivo biodistribution results validated the PET/CT studies. Conclusion: Our findings demonstrate that intraarterial delivery of bevacizumab into the brain across an osmotically opened BBB is effective, in contrast to the intravenous route.

Keywords: brain; drug delivery; endovascular; molecular imaging; nuclear medicine.

FIGURE 1.

Radiolabeling of bevacizumab with ⁸⁹Zr. (A and B) Reaction schemes demonstrating conjugation of bevacizumab with deferoxamine and its subsequent radiolabeling with ⁸⁹Zr. (C) Matrix-assisted laser desorption ionization time-of-flight spectra of bevacizumab and BVDFO, showing increase of molecular weight that indicates conjugation on average of 3 molecules of deferoxamine with each antibody. (D) Evaluation of bevacizumab and BVDFO biding to VGEF, showing that conjugation of deferoxamine with antibody did not affect its targeting properties. (E) Size-exclusion chromatograms illustrating coelution of bevacizumab (black line, based on absorbance at 280 nm) and ⁸⁹Zr-BVDFO (red line, derived using flow-through radiation detector), indicating successful radiolabeling of BVDFO with ⁸⁹Zr. RT = room temperature; HEPES = 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid.

FIGURE 2.

Dynamics of ⁸⁹Zr-BVDFO delivery with and without BBB opening. (A–C) Representative axial, sagittal, and coronal PET/CT images showing brain uptake with IA/BBBI (A), BBBO/IA (B), and IV/BBBO (C). (D) Graph showing faster and higher ipsilateral hemisphere uptake with BBBO/IA (red) than with IA/BBBI (blue) or IV/BBBO (gray). (E) Graph showing increase in heart uptake with IA/BBBI (blue), BBBO/IA (red), and IV/BBBO (gray) (n = 4). No increase in brain uptake was observed with IV/BBBO on 45-min dynamic PET scans. NS = statistically nonsignificant. *Statistically significant difference.

FIGURE 3.

Distribution of ⁸⁹Zr-BVDFO in brain. Representative coronal, sagittal, and transverse PET images overlaid by mouse brain template are shown for IA/BBBI (A), BBBO/IA (B), and IV/BBBO (C). Uptake of ⁸⁹Zr-BVDFO is significantly higher with BBBO/IA than with IA/BBBI or IV/BBBO and is highest in right striatum, hippocampus, and amygdala. *Statistically significant difference.

FIGURE 4.

⁸⁹Zr-BVDFO delivery to, and its biodistribution in, brain with and without BBB opening. (A–C) Representative whole-body PET/CT images obtained with IA/BBBI (A), BBBO/IA (B), and IV/BBBO (C). (D) PET-based quantification of ⁸⁹Zr-BVDFO uptake in ipsilateral hemisphere. (E) Ex vivo biodistribution 24 h after infusion, showing agreement with higher uptake in ipsilateral than contralateral hemisphere in BBBO/IA group and with higher brain uptake in BBBO/IA group than in IA/BBBI and IV/BBBO groups.