New transgenic NIS reporter rats for longitudinal tracking of fibrogenesis by high-resolution imaging

PET/CT in the Evaluation of CAR-T Cell Immunotherapy in Hematological Malignancies

Chimeric antigen receptor (CAR)-T cell-based immunotherapy has emerged as a path-breaking strategy for certain hematological malignancies. Assessment of the response to CAR-T therapy using quantitative imaging techniques such as positron emission tomography/computed tomography (PET/CT) has been broadly investigated. However, the definitive role of PET/CT in CAR-T therapy remains to be established. [18F]FDG PET/CT has demonstrated high sensitivity and specificity for differentiating patients with a partial and complete response after CAR-T therapy in lymphoma. The early therapeutic response and immune-related adverse effects such as cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome can also be detected on [18F]FDG PET images. In otherwise asymptomatic lymphoma patients with partial response following CAR-T therapy, the only positive findings could be abnormal PET/CT results. In multiple myeloma, a negative [18F]FDG PET/CT after receiving B-cell maturation antigen-directed CAR-T therapy has been associated with a favorable prognosis. In leukemia, [18F]FDG PET/CT can detect extramedullary metastases and treatment responses after therapy. Hence, PET/CT is a valuable imaging tool for patients undergoing CAR-T therapy for pretreatment evaluation, monitoring treatment response, assessing safety, and guiding therapeutic strategies. Developing guidelines with standardized cutoff values for various PET parameters and tumor cell-specific tracers may improve the efficacy and safety of CAR-T therapy.

Development of a Clinically Relevant Reporter for Chimeric Antigen Receptor T-cell Expansion, Trafficking, and Toxicity

Although chimeric antigen receptor T (CART)-cell therapy has been successful in treating certain hematologic malignancies, wider adoption of CART-cell therapy is limited because of minimal activity in solid tumors and development of life-threatening toxicities, including cytokine release syndrome (CRS). There is a lack of a robust, clinically relevant imaging platform to monitor in vivo expansion and trafficking to tumor sites. To address this, we utilized the sodium iodide symporter (NIS) as a platform to image and track CART cells. We engineered CD19-directed and B-cell maturation antigen (BCMA)-directed CART cells to express NIS (NIS⁺CART19 and NIS⁺BCMA-CART, respectively) and tested the sensitivity of ¹⁸F-TFB-PET to detect trafficking and expansion in systemic and localized tumor models and in a CART-cell toxicity model. NIS⁺CART19 and NIS⁺BCMA-CART cells were generated through dual transduction with two vectors and demonstrated exclusive ¹²⁵I uptake in vitro. ¹⁸F-TFB-PET detected NIS⁺CART cells in vivo to a sensitivity level of 40,000 cells. ¹⁸F-TFB-PET confirmed NIS⁺BCMA-CART-cell trafficking to the tumor sites in localized and systemic tumor models. In a xenograft model for CART-cell toxicity, ¹⁸F-TFB-PET revealed significant systemic uptake, correlating with CART-cell in vivo expansion, cytokine production, and development of CRS-associated clinical symptoms. NIS provides a sensitive, clinically applicable platform for CART-cell imaging with PET scan. ¹⁸F-TFB-PET detected CART-cell trafficking to tumor sites and in vivo expansion, correlating with the development of clinical and laboratory markers of CRS. These studies demonstrate a noninvasive, clinically relevant method to assess CART-cell functions in vivo.