Advancement and Challenges in Monitoring of CAR-T Cell Therapy: A Comprehensive Review of Parameters and Markers in Hematological Malignancies

Abstract

Chimeric antigen receptor T-cell (CAR-T) therapy has revolutionized the treatment for relapsed/refractory B-cell lymphomas. Despite its success, this therapy is accompanied by a significant frequency of adverse events, including cytokine release syndrome (CRS), immune-effector-cell-associated neurotoxicity syndrome (ICANS), or cytopenias, reaching even up to 80% of patients following CAR-T cell therapy. CRS results from the uncontrolled overproduction of proinflammatory cytokines, which leads to symptoms such as fever, headache, hypoxia, or neurological complications. CAR-T cell detection is possible by the use of flow cytometry (FC) or quantitative polymerase chain reaction (qPCR) assays, the two primary techniques used for CAR-T evaluation in peripheral blood, bone marrow (BM), and cerebrospinal fluid (CSF). State-of-the-art imaging technologies play a crucial role in monitoring the distribution and persistence of CAR-T cells in clinical trials. Still, they can also be extended with the use of FC and digital PCR (dPCR). Monitoring the changes in cell populations during disease progression and treatment gives an important insight into how the response to CAR-T cell therapy develops on a cellular level. It can help improve the therapeutic design and optimize CAR-T cell therapy to make it more precise and personalized, which is crucial to overcoming the problem of tumor relapse.

Keywords: biomarkers; chimeric antigen receptor T-cell (CAR-T); flow cytometry (FC); immunotherapy; monitoring; polymerase chain reaction (PCR).

Figure 1

The immune checkpoint molecules on the surface of CAR-T cell. Abbreviations: Glucocorticoid-induced tumor-necrosis-factor-receptor-related protein (GITR), cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), programmed death-1 (PD-1), T-cell immunoglobulin and mucin domain 3 (TIM-3), B and T lymphocyte attenuator (BTLA), V-domain immunoglobulin suppressor of T cell activation (VISTA), lymphocyte activation gene 3 (LAG-3), and chimeric antigen receptor T (CAR-T) [122].

Figure 2

Mechanism leading to CRS and ICANS. The red dots indicate TNF-$\mathsf{\alpha }$ and IFN-$\mathsf{\gamma }$, yellow dots indicate TNF-$\mathsf{\alpha }$, and purple dots indicate IL-1, IL-6, IFN-$\mathsf{\gamma }$, MIP, MCP-1, and NOS. The interactions between them are bidirectional. Abbreviations: tumor necrosis factor α (TNF-$\mathsf{\alpha }$), interferon gamma (IFN-$\mathsf{\gamma })$, macrophage inflammatory proteins (MIP), monocyte chemotactic protein 1 (MCP-1), nitric oxide synthases (NOS), chimeric antigen receptor (CAR), cytokine release syndrome (CRS), immune-effector-cell-associated neurotoxicity syndrome (ICANS), and blood–brain barrier (BBB) [143,144,145].