[ 18 F]FHBG PET/CT Imaging of CD34-TK75 Transduced Donor T Cells in Relapsed Allogeneic Stem Cell Transplant Patients: Safety and Feasibility

Abstract

Described herein is a first-in-man attempt to both genetically modify T cells with an imagable suicide gene and track these transduced donor T cells in allogeneic stem cell transplantation recipients using noninvasive positron emission tomography/computerized tomography (PET/CT) imaging. A suicide gene encoding a human CD34-Herpes Simplex Virus-1-thymidine kinase (CD34-TK75) fusion enabled enrichment of retrovirally transduced T cells (TdT), control of graft-versus-host disease and imaging of TdT migration and expansion in vivo in mice and man. Analysis confirmed that CD34-TK75-enriched TdT contained no replication competent γ-retrovirus, were sensitive to ganciclovir, and displayed characteristic retroviral insertion sites (by targeted sequencing). Affinity-purified CD34-TK75(+)-selected donor T cells (1.0-13 × 10(5))/kg were infused into eight patients who relapsed after allogeneic stem cell transplantation. Six patients also were administered 9-[4-((18)F)fluoro-3-hydroxymethyl-butyl]guanine ([(18)F]FHBG) to specifically track the genetically modified donor T cells by PET/CT at several time points after infusion. All patients were assessed for graft-versus-host disease, response to ganciclovir, circulating TdT cells (using both quantitative polymerase chain reaction and [(18)F]FHBG PET/CT imaging), TdT cell clonal expansion, and immune response to the TdT. This phase 1 trial demonstrated that genetically modified T cells and [(18)F]FHBG can be safely infused in patients with relapsed hematologic malignancies after allogeneic stem cell transplantation.

Imaging grafted cells with [18F]FHBG using an optimized HSV1-TK mammalian expression vector in a brain injury rodent model

“…Different radioactive compounds are routinely injected in patients for clinical diagnosis. [ 18 F]FHBG appears to be an effective tool for obtaining biological information in a non-invasive manner and has been already tested in a clinical trial, in patient with leukaemia after infusion of Tcell genetically modified [ 7 , 8 ].…”

“…[ 18 F]FHBG is a PET imaging radiotracer that is easily transferrable to human applications [ 7 , 8 ]. PET scans allow radiolabelled markers and their interactions with biochemical processes to be imaged in living subjects.…”

Imaging Biomarkers in Immunotherapy

“… 92 Eissenberg et al recently described an early clinical work in which T-cells were modified with a suicide gene (CD34-HSV1tk) whose distribution could be tracked over time using 9-[4-(18 F)fluoro-3-hydroxymethyl-butyl] guanine ([ 18 F]FHBG). 93 A similar approach had been reported by Dubey et al using 9-[4-[18F]fluoro-3-(hydroxymethyl) butyl]guanine ([ 18 F]FHBG) to image splenic T-cells bearing the HSV1-sr39tk PET reporter gene. 94 Earlier precursor work in 2001 by Ponomarev et al used [ 124 I]-(2′-deoxy-2′-fluoro-β- d -arabinofuranosyl)-5-iodouracil to detect T-cell activation in vivo using an HSV1tk/green fluorescent protein reporter system in rats.…”

CAR-T cell in vivo tracking method using PET scan with the reporter gene and new investigational tracer [18F] FHBG

“…Yaghoubi et al also studied human pharmacokinetics and dosimetry of [ 18 F] FHBG with ten healthy volunteers and showed no toxicity (14). The safety and feasibility of radiolabeled [ 18 F] FHBG PET is studied in several clinical fields including recurrent glioma (7,15). Keu et al reported the in vivo kinetics of CAR-T cells detected by PET scan using [ 18 F] FHBG (16).…”