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Radionuclide-based molecular imaging allows CAR-T cellular visualization and therapeutic monitoring.

ABSTRACT: Chimeric antigen receptor T cell (CAR-T) therapy is a new and effective form of adoptive cell therapy that is rapidly entering the mainstream for the treatment of CD19-positive hematological cancers because of its impressive effect and durable responses. Huge challenges remain in achieving similar success in patients with solid tumors. The current methods of monitoring CAR-T, including morphological imaging (CT and MRI), blood tests, and biopsy, have limitations to assess whether CAR-T cells are homing to tumor sites and infiltrating into tumor bed, or to assess the survival, proliferation, and persistence of CAR-T cells in solid tumors associated with an immunosuppressive microenvironment. Radionuclide-based molecular imaging affords improved CAR-T cellular visualization and therapeutic monitoring through either a direct cellular radiolabeling approach or a reporter gene imaging strategy, and endogenous cell imaging is beneficial to reflect functional information and immune status of T cells. Focusing on the dynamic monitoring and precise assessment of CAR-T therapy, this review summarizes the current applications of radionuclide-based noninvasive imaging in CAR-T cells visualization and monitoring and presents current challenges and strategic choices.

SUBMITTER: Shao F

PROVIDER: S-EPMC8171102 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundGenetically engineered chimeric antigen receptor (CAR) T lymphocytes are promising therapeutic tools for cancer. Four CAR T cell drugs, including tisagenlecleucel (tisa-cel) and axicabtagene-ciloleucel (axi-cel), all targeting CD19, are currently approved for treating B cell malignancies. Flow cytometry (FC) remains the standard for monitoring CAR T cells using a recombinant biotinylated target protein. Nevertheless, there is a need for additional tools, and the challenge is to develop an easy, relevant, highly sensitive, reproducible, and inexpensive detection method. Molecular tools can meet this need to specifically monitor long-term persistent CAR T cells.MethodsBased on 2 experimental CAR T cell constructs, IL-1RAP and CS1, we designed 2 quantitative digital droplet (ddPCR) PCR assays. By targeting the 4.1BB/CD3z (28BBz) or 28/CD3z (28z) junction area, we demonstrated that PCR assays can be applied to approved CD19 CAR T drugs. Both 28z and 28BBz ddPCR assays allow determination of the average vector copy number (VCN) per cell. We confirmed that the VCN is dependent on the multiplicity of infection and verified that the VCN of our experimental or GMP-like IL-1RAP CAR T cells met the requirement (< 5 VCN/cell) for delivery to the clinical department, similar to approved axi-cel or tisa-cel drugs.Results28BBz and 28z ddPCR assays applied to 2 tumoral (acute myeloid leukemia (AML) or multiple myeloma (MM) xenograft humanized NSG mouse models allowed us to quantify the early expansion (up to day 30) of CAR T cells after injection. Interestingly, following initial expansion, when circulating CAR T cells were challenged with the tumor, we noted a second expansion phase. Investigation of the bone marrow, spleen and lung showed that CAR T cells disseminated more within these tissues in mice previously injected with leukemic cell lines. Finally, circulating CAR T cell ddPCR monitoring of R/R acute lymphoid leukemia or diffuse large B cell lymphoma (n = 10 for tisa-cel and n = 7 for axi-cel) patients treated with both approved CAR T cells allowed detection of early expansion, which was highly correlated with FC, as well as long-term persistence (up to 450 days), while FC failed to detect these events.ConclusionOverall, we designed and validated 2 ddPCR assays allowing routine or preclinical monitoring of early- and long-term circulating approved or experimental CAR T cells, including our own IL-1RAP CAR T cells, which will be evaluated in an upcoming phase I clinical trial.

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Radionuclide-based molecular imaging allows CAR-T cellular visualization and therapeutic monitoring.

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