PET of Adoptively Transferred Chimeric Antigen Receptor T Cells with ⁸⁹Zr-Oxine

Abstract

Chimeric antigen receptor (CAR) T cell therapy is a promising clinical approach for reducing tumor progression and prolonging patient survival. However, improvements in both the safety and the potency of CAR T cell therapy demand quantitative imaging techniques to determine the distribution of cells after adoptive transfer. The purpose of this study was to optimize Zr-oxine labeling of CAR T cells and evaluate PET as a platform for imaging adoptively transferred CAR T cells. CAR T cells were labeled with 0-1.4 MBq of Zr-oxine per 10 cells and assessed for radioactivity retention, viability, and functionality. In vivo trafficking of Zr-oxine-labeled CAR T cells was evaluated in 2 murine xenograft tumor models: glioblastoma brain tumors with intracranially delivered IL13Rα2-targeted CAR T cells, and subcutaneous prostate tumors with intravenously delivered prostate stem cell antigen (PSCA)-targeted CAR T cells. CAR T cells were efficiently labeled (75%) and retained more than 60% of the Zr over 6 d. In vitro cytokine production, migration, and tumor cytotoxicity, as well as in vivo antitumor activity, were not significantly reduced when labeled with 70 kBq/10 cells. IL13Rα2-CAR T cells delivered intraventricularly were detectable by PET for at least 6 d throughout the central nervous system and within intracranial tumors. When intravenously administered, PSCA-CAR T cells also showed tumor tropism, with a 9-fold greater tumor-to-muscle ratio than for CAR-negative T cells. Zr-oxine can be used for labeling and imaging CAR T cells while maintaining cell viability and function. On the basis of these studies, we conclude thatZr-oxine is a clinically translatable platform for real-time assessment of cell therapies.

CAR T cells for brain tumors: Lessons learned and road ahead

“…Representative PET images are depicted at 15 min, 6 h, 1 d or 5 d after ICT (top) or ICV (bottom) delivery of 89 Zr‐oxine labeled IL13Rα2‐CAR T cells are depicted. Color scale indicates percentages of injected radioactive dose (ID) per gram weight of voxel that were calculated using Vivo‐Quant (Invicro) analysis of the PET images…”

“…To improve cell localization, chemokine receptor‐engineered T cells should be designed for the chemokine signaling unique to each tumor. Such strategies to improve tumor trafficking are important, as preclinical models suggest that trafficking can often be highly inefficient with only a minor fraction of the adoptively transferred cells infiltrating the tumor …”

“…This approach is the current clinical standard for imaging cells and platelets with SPECT, where lipophilic metal complexes passively diffuse across cell membranes in a rapid and efficient manner . Recently adopted for PET, we imaged 89 Zr‐oxine‐labeled CAR T cells in both subcutaneous prostate and intracranial glioma models . CAR T cells demonstrated tumor tropism and retained therapeutic potential after labeling.…”

“…64 In fact, preclinical studies in which CAR T cells were labeled with the radionuclide 89 Zr and followed by PET imaging in mice, we show that CAR T cells delivered into the brain parenchyma remain localized in the brain, whereas ICV-delivered cells distribute throughout the CNS over 6 days of monitoring by PET (Figure 3). 205 Indeed, direct infusion into the CSF via intraventricular delivery achieved a complete clinical response in a patient with multifocal disease, including a distal lesion in the spine, 69 illustrating the surveillance of CAR T cells throughout the CNS.…”

“…Such strategies to improve tumor trafficking are important, as preclinical models suggest that trafficking can often be highly inefficient with only a minor fraction of the adoptively transferred cells infiltrating the tumor. 205,215 When combined with computed tomography (CT) or MRI, the sensitivity of nuclear imaging is co-registered with anatomical detail.…”