Moreno-Cortes, Eider

Chimeric antigen receptor (CAR) T-cell therapy is an effective treatment for hematologic malignancies. However, it is limited by high costs, risk of severe toxicities such as cytokine release syndrome and neurotoxicity, and heterogeneous patient responses. The current therapy monitoring depends largely on subjective symptom assessment, routine laboratory tests, and basic vital signs, without real-time, quantitative evaluation of CAR T-cell expansion or activation in clinical practice. This lack of timely immune monitoring hampers individualized care and contributes to increased treatment costs. To address this need, we present a proof-of-concept, label-free rapid optical imaging (ROI) biosensor with automated machine learning analysis for direct quantification of CAR T-cells from whole blood. This microfluidic platform integrates red blood cell (RBC) removal, CAR T-cell capture, and imaging-based quantification on a single chip, eliminating the need for centrifugation, staining, and operator-dependent interpretation. For validation, 50 μL whole blood samples spiked with Jurkat cells expressing CD19 CARs underwent RBC depletion by agglutination and microfiltration. The remaining blood components were then incubated on a sensor chip functionalized with recombinant CD19 protein. Captured CAR T-cells were imaged by brightfield microscopy and automatically enumerated using a machine learning algorithm trained on fluorescence-validated cells. The CD-19 cells’ capture performance was validated by flow cytometry and fluorescence imaging. The trained machine learning model validated at 88% sensitivity and 96% specificity. Buffer and whole blood calibration curves were established across clinically relevant concentrations (1–1000 cells/µL) with triple replicates. The results showed high correlation (0.975 and 0.990 R2) between the spiked concentration and the detected CAR T-cells, with a 95% certainty limit of detection (LOD) and quantification (LOQ) of 0.6 and 1.1 cells/µL for spiked buffer, and 14 and 67 cells/µL for spiked whole-blood, respectively.

Background Primary cutaneous diffuse large B-cell lymphoma, leg type (PCDLBCL-LT), is a rare subset of primary cutaneous lymphoma known for its aggressive behavior, poor prognosis, and limited treatment options, particularly in the relapsed or refractory setting. We report a case of a patient diagnosed with PCDLBCL-LT who achieved a clinically significant response and sustained remission for seven months with acalabrutinib, a covalent inhibitor of Bruton’s tyrosine kinase (BTK), before disease progression. Case presentation An 88-year-old woman presented with a rapidly enlarging ulcerated lesion on the left lower leg. Histopathological and immunohistochemical analyses confirmed the diagnosis of PCDLBCL-LT. She was treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) chemoimmunotherapy, followed by external beam radiation therapy (RT). These interventions resulted in only a partial response, and the disease progressed within several months. The patient was receiving direct oral anticoagulant (DOAC) therapy for left lower limb deep vein thrombosis, and she also had a history of hypertension. Considering the increased risk of major bleeding associated with DOAC use and the elevated risk of cardiovascular adverse events previously reported with ibrutinib, an alternative BTK inhibitor was considered. Accordingly, she was initiated on acalabrutinib at a dose of 100 mg orally twice daily. The patient exhibited a rapid and robust clinical response, with complete resolution of cutaneous lesions and sustained remission lasting seven months. Ultimately, the disease progressed, and given her advanced age and overall poor performance status, she was transitioned to hospice care. She subsequently died 14 months after initiating acalabrutinib. Conclusion This report documents the first known case of successful treatment of relapsed/refractory PCDLBCL-LT with acalabrutinib. Despite advanced age and poor performance status, the patient experienced rapid symptom resolution and durable remission without treatment-related adverse events. These findings suggest that BTK inhibitors may represent a promising therapeutic approach for PCDLBCL-LT, either as monotherapy or in combination with anti-CD20 antibodies. Further investigation into novel targeted therapies is urgently needed for this rare and aggressive lymphoma subtype.

Abstract Background Although CAR T-cell therapy has achieved remarkable response in patients (pts) with B-cell non-Hodgkin’s lymphoma (NHL), 20-30% of pts still have primary refractory disease (PD1), and another 30-40% relapse (PD2). We and others have shown that monocytes can modulate T-cell functions and impact clinical response to chemoimmunotherapy in NHL. Given that monocytes nadir and recovery kinetics differ from lymphocytes post lymphodepletion chemotherapy, we hypothesize that monocyte phenotype at peak CAR-T expansion and in the early month post CAR-T can modulate immune responses. Methods scRNAseq were performed on peripheral blood mononuclear cells of NHL pts prior to lymphodepletion chemotherapy (pre), at peak CAR-T expansion (peak), and one month following CAR-T (M1). Seurat v4.3.0 was used for unsupervised hierarchical clustering analysis. Lugano criteria was used to determine clinical responses which were categorized as CR (complete remission), PD1, or PD2. Results We analyzed 129,981 monocytes from 77 samples of 32 pts (16 CR, 4 PD1, 12 PD2) and 5 healthy controls. Unsupervised hierarchical clustering analysis identified 13 monocyte clusters: 4 classical monocyte (CM) clusters with transcriptome profiles for enriched signaling in IL-6, TGFβ, EMT, and p53; 2 intermediate monocyte (IM) clusters enriched for IL-1 or CD38 signaling; 2 non-classical monocytes (NM), one with increased CD36 expression; 3 monocytic MDSC clusters with enrichment of TGFβ, SIRPα, and HIF1α signaling; and 2 lymphoma-associated monocytes, expressing CD163 or CD169. At Pre and Peak, the distribution of the monocyte clusters was similar in pts with CR, PD2, or PD1, with only a slight decrease in the percent of NM in the PD2 group at Pre and slight increase of CD36 NM in PD1 at Peak. Compared to Pre, all pts had increased percent of CD36 NM and IL-1 IM at Peak. Interestingly, while the distribution of monocyte clusters was similar at Pre and Peak across clinical responses, GSEA showed that monocytes in CR pts, compared to PD1 and PD2, had gene expression enrichment of MYC target V2 pathway at Pre and TGFβ pathway at Peak. At M1, pts in PD1 had increased percent of p53 and TGFβ CM and decreased percent of NM. In contrast, pts with CR had decreased percent of IL-6 CM, p53 CM, TGFβ CM, IL-1 IM and increased percent of NM. Notably, as pts with CR and PD2 may appear similar clinically at M1, pts with PD2, compared to CR, have increased IL-6 CM, IL-1 IM, and decreased NM. In addition, GSEA showed that PD2 pts had increased IFNα response. Our results demonstrate that monocyte phenotype differences at Pre and Peak could be associated with CAR-T clinical response, and that persistent inflammatory monocyte signaling at M1 in pts with clinical response is associated with relapse. These data suggest a role for development of monocyte biomarkers to predict response and therapeutic targeting. Citation Format: Andre de Menezes Silva Corraes, Panwen Wang, Radhika Bansal, Henan Zhang, Zuoyi Shao, Kevin Regan, Eider Moreno Cortes, Arushi Khurana, Nora Bennani, Yucai Wang, Paul Hampel, Jonas Paludo, Patrick Johnston, Hemant Murthy, Madiha Iqbal, Stephen Ansell, Javier Munoz, Allison Rosenthal, Mohamed Kharfan-Dabaja, Januario Castro, Saad Kenderian, Haidong Dong, Ying Li, Yi Lin. Monocyte transcriptome profiles associated with clinical response in patients with B-cell non-Hodgkin’s lymphoma receiving CD19-directed CAR-T therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4001.

Abstract Background: Although CAR T-cell therapy has achieved remarkable response rates in adult patients (pts) with relapsed and refractory B-cell non-Hodgkin’s lymphoma (NHL), 20-30% of pts still have primary refractory disease, and 30-40% of pts relapse, often within 6 months of therapy. Given that durable clinical response can be achieved without CAR T cell persistence, we hypothesized that durable remission is correlated with the expansion of tumor-reactive T-cell receptor (TCR) clones following CAR T-cell infusion. To assess this, we examined the TCR repertoire of adult pts with B-NHL who received CD19 CAR T-cell (axi-cel) therapy to identify correlates of clinical response. Methods: Single-cell (sc) RNA sequencing (seq) and scTCR-seq were performed on peripheral blood mononuclear cells from B-NHL pts before lymphodepletion chemotherapy (pre), at peak CAR-T expansion (peak), and one month following CAR-T (M1). scRNAseq and scTCR-seq data were processed using CellRanger v7.0.1, which were then analyzed using Immunarch (v0.9.0) for TCR clonality and sample diversity. Diversity was assessed using the Gini coefficient to indicate clone size inequality (0 = maximum diversity). TCR diversity and phenotype of expanded and emerged TCR clones post CAR-T were compared across clinical response categories: CR (complete remission for at least 6 months), PD1 (primary refractory), and PD2 (relapsed after partial or complete response). Results: We analyzed 107,035 T cells from 77 serial samples of 32 pts (16 CR, 4 PD1, 12 PD2) and 5 healthy controls. Compared to pts with PD1 and PD2, pts with CR had a larger Gini coefficient for TCR clones at M1 relative to Pre and Peak. The Gini coefficient was the largest for tumor recirculating CD8 T effector memory (Tem) and activated CD8 peripheral memory (Tpm) cells at M1 for pts with CR. Examining the repertoire of emerged and expanded TCR clones at Peak and M1 from Pre, pts with PD2, compared to pts with CR, had a higher percentage of activated CD8 T peripheral memory (Tpm) and T regulatory cells (Treg) among the emerged clones and activated CD8 Tpm among the expanded clones. Patients with PD1, relative to patients with CR, had more proliferating and non-activated CD8 Tpm among the expanded and emerged clones. Conclusion: NHL pts with CR after CAR-T had more robust clonal expansion of T cells, particularly tumor recirculating CD8 Tem and activated CD8 Tpm, compared to pts with relapsed or refractory disease. In contrast, pts with relapsed or refractory disease had an expansion of TCR clones with a larger proportion of CD8 Tpm and Tregs. Endogenous tumor-reactive TCR expansion may help predict favorable clinical response following CAR T-cell therapy. Citation Format: Aiman J. Faruqi, Panwen Wang, Radhika Bansal, Andre De Menezes Silva Corraes, Henan Zhang, Zuoyi Shao, Kevin Regan, Eider Moreno Cortes, Arushi Khurana, Nora Bennani, Yucai Wang, Paul Hampel, Jonas Paludo, Patrick Johnston, Hemant Murthy, Madiha Iqbal, Stephen Ansell, Javier Munoz, Allison Rosenthal, Mohamed Kharfan Dabaja, Januario E. Castro, Saad Kenderian, Haidong Dong, Ying Li, Yi Lin. T-cell receptor repertoire changes associated with clinical response in patients with B-cell non-Hodgkin’s lymphoma receiving CD19 CAR-T therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 53.

Introduction: Pancreatic ductal adenocarcinoma (PDAC) is one of the most devastating cancers, and therapies to treat this malignancy have not evolved rapidly to fulfill the need of affected patients. PDAC, like many solid malignancies, is considered a “cold immunological tumor” where the lack of targetable tumor-associated antigens has hampered the development of successful immunotherapies. Despite newer treatment approaches, PDAC patients with advanced disease have a dismal prognosis. Therefore, there is an urgent need to develop new therapies. Plectin-1 is a high molecular weight protein (∼500 kDa) that participates in cytoskeleton network organization linking intermediate filaments to microtubules and microfilaments. Plectin-1 is aberrantly expressed in the PDAC cellular membrane, contributes to PDAC pathogenesis, and confers a poor prognosis. Plectin-1-targeting peptides (PTP) in mice and humans have been successfully explored for their use in PDAC imaging and targeted payload delivery (small molecules, radioisotopes, and chemotherapy). We sought to take advantage of the specific binding of PTP and develop a peptide-based plectin-1 chimeric antigen receptor (CAR), and test T-cell transduced with this construct in vitro against PDAC cell lines. Methods: Using in silico tools, we optimized different pepto-CAR constructs and selected one that showed the highest levels of cytotoxicity against plectin-1-expressing PDAC cell lines. A myc tag was incorporated in the hinge region for flow cytometry or western blot detection. The intracellular signaling domain of these CAR sequences included 4-1BB and the zeta chain of the CD3 molecule ( Figure 1A). Plasmids containing the CAR sequence were packaged on lentivirus particles using HEK293T cells. Purified plectin-1 CAR lentiviruses were used to transduce T-cells derived from human peripheral blood T-cells obtained and purified from healthy donor whole blood. The expanded CAR T-cells were used for cytotoxic experiments against different cell lines. Results: Expression of plectin-1 CAR was confirmed by flow cytometry using an anti-myc tag antibody ( Figure 1B). Plectin-1 expression was analyzed in different pancreatic cancer cell lines, and the BxPC-3 cells showed the highest expression level ( Figure 1B). Using a luciferase-based assay, we plated 50,000 BxPC-3 cells per well in duplicates with different effector-to-target (E:T) ratios. After 24 hours, luciferin was added, and the plate was read using a luminometer. As a negative control for effector cells, we use T-cells without a CAR ( Figure 1B), and for the target cells, we use the plectin-1 negative lung cancer cell line A549 ( Figure 1B). Plectin-1 CAR T-cells effectively killed BxPC-3 cells at different E:T ratios in a specific manner compared with controls using unmodified T-cells. Furthermore, no cytotoxicity was observed against plectin-1 negative A549 cells ( Figure 1A). Conclusion: Our results show that a novel peptide-based CAR construct design against plectin-1 can induce specific cytotoxicity on plectin-1 expressing PDAC cell line BxPC-3. Furthermore, these data demonstrate the feasibility of using a CAR with a peptide-based antigen binding domain instead of the traditional antibody-derived scFv. This novel peptide-based CAR design offers alternatives for cellular therapy bioengineering. Moreover, our results can significantly impact immune-oncology therapeutic applications, particularly in challenging diseases like pancreatic cancer. Figure 1 . A) In the above section, the Plectin-1 CAR construct is depicted. Cytotoxicity of unmodified T-cells and Plectin-1 CAR T-cells against BxPC-3 and A549 is shown below. B) Expression of Plectin-1 CAR in unmodified T-cells and Plectin-1 CAR T-cells is shown on the left. The expression of plectin-1 antigen on the surface of BxPC-3 cells and A549 cells is shown on the right. PTP: plectin-1 targeting peptide.

Background: Chimeric Antigen Receptor (CAR) T-cell clinical trials are growing exponentially. Database analysis can help identify scientific trends and generate projections regarding potential approvals before the results of the studies are completed or published. This is particularly interesting in pediatric oncology, where available analyses from repository databases are scarce or not available. Because of that reason, we sought to analyze the clinical trial public records from entries related to CAR T-cell clinical studies in pediatric patients (18 years or younger) uploaded to the clinicaltrials.gov database. Methods: We query the available data from clinicaltrials.gov using the following keywords: “CAR T cell in pediatrics”, “CAR T cell and cancer”, “chimeric antigen receptor”, “CAR T AND tumor antigen”, 'CAR T cell antigens“, ”Tumor antigens targeted by CAR T cells“, ”engineered T cells“, ”modified T cell“, ”CAR T cells in Cancer“, ”CAR T cell therapy“, ”CAR T cell therapy AND Cancer“ (data cut off July-2023). The data were tabulated, and the trials that did not meet the search criteria were excluded manually. Data cleansing was performed using published scientific data, web search-based information, and patent databases. Results: We found 4297 results in the Clinicaltrials.gov platform; we excluded 3978 clinical trials that did not involve the pediatric population (<18 years) or CAR T-cell intervention. The final analysis included 319 clinical trials posted on the clinicaltrials.gov website by the cut-off date. 207 (64.9%) were conducted in China, 74 (23.2%) in the US, and 21 (6.5%) in Europe. Most CAR T-cell trials focused on hematological cancer (89%), followed by non-CNS solid tumors 8%, and CNS tumors 3%. The most frequent targets were CD19 (46%), CD7 (7%), followed by GD2, CD22, CD123, CD19 + CD22 and CD30. Most clinical trials did not report the construct generation used in their CAR T cell product (58%). Among the trials with that information, second-generation constructs (2G) were used in 32% of the studies, followed by 3G and 4G constructs (5% of studies each). Most clinical trials were in early stages of development, Phase 1 or 2 (75%). We observed a continuous increase in the number of clinical trials registered yearly, except for a small reduction in 2022 and 2021, probably related to COVID restrictions and challenges. Overall, the general trend predicts at least a 50% yearly increase in registered studies ( Figure 1). Similarly, to what is observed in adult clinical trials, the most common signaling domains are 2G CAR constructs expressing either CD28 or 4-1BB as costimulatory domains. Among those, 4-1BB being is the most popular choice. Conclusion: Our findings indicate a growing interest in the clinical development of CAR T-cell therapies applied to pediatric oncology. Most of these studies are in early phase I and II and focus primarily on hematological cancers using second-generation constructs targeting CD19. The is a steady increase in the number of studies registered each year that predicts future FDA approvals using CAR T-cell products.

Keywords: Chimeric Antigen Receptor T cell, Pharmacoeconomic, Pediatric, Clinical Trials With the success of Chimeric Antigen Receptor (CAR) T-cell therapy in the pediatric population, new clinical trials have surged worldwide. To date, no previous study has analyzed the effect of socioeconomic factors on the development of clinical trials for CAR T-cells in the pediatric population. In recent years new countries and emerging economies have contributed significantly to the development of CAR T-cell clinical trials. A better understanding of the socioeconomic factors that influenced these trends will facilitate the future development of this cellular therapy field. To assess the impact of socioeconomic factors related to the development of clinical trials on CAR T-cell therapies in the pediatric population, we analyzed data entries from clinical trials registered to the Clinicaltrials.gov database. To query the information, we used the following keywords “(leukemia OR cancer OR lymphoma OR malignancies OR tumor OR solid tumor) AND (CAR OR chimeric antigen receptor OR CAR T-cell OR adoptive immunotherapy OR immune effector OR cellular therapy) AND (Child)”. In addition, we used different filters that allowed the selection of studies that focused on patients 18 years of age and younger. Data corresponding to entries with a data cut-off of July-2023 were included. In addition, we use the World Bank country's macroeconomic database (January 1 st, 2009 to December 31 st, 2022). We found 4,297 results in the Clinicaltrials.gov platform; we excluded 3,978 clinical trials that did not involve the pediatric population (≤18 years) or CAR T-cell intervention. There were 319 clinical trials included, sponsored in 19 countries, as shown in Figure A. Of those studies, 207 (64.9%) were conducted in China, 74 (23.2%) in the U.S., and 21 (6.5%) in Europe. Not surprisingly, the number of clinical trials is strictly proportional to each country's Gross Domestic Product (GDP) and Research and Development (R&D) expenditure, as shown in Figure B. Pearsons' coefficient between GDP and the number of trials registered per country is 0.8 (p-value < 0.001); similarly, Pearsons's coefficient between R&D expenditure and the number of problems reported per country is 0.64 (p-value < 0.004). The United States and China are developing 88% of the Clinical trials, and 96% of the clinical trials occur in countries ranked in the top 10 highest GDP. Our database analysis shows a notable disparity in the countries leading cutting-edge research in CAR T-cell therapy for pediatric oncology. The primary locations for these clinical studies are countries ranked in the top 10 in terms of GDP, with China and the USA being the main contributors. Access to clinical trials plays a crucial role in improving cancer patients' outcomes, and this disparity in the development of cellular therapies is likely to impact children from middle and low-GDP countries significantly. Urgent strategies are required to address this issue and ensure more equitable access to advanced technologies and clinical trials in cellular therapy for pediatric cancers. These strategies should become a high priority for national and international health departments and organizations in the coming years. By promoting more comprehensive clinical trial access and collaboration, we can work towards reducing these disparities and providing better treatment options for all children facing pediatric cancer.

The Health Level 7 (HL7) organization introduced the Information Sensitivity Policy Value Set with 45 sensitive data categories to facilitate the implementation of granular electronic consent technology. The goal is to allow patients to have control over the sharing of their sensitive medical records. This study represents the first attempt to explore physicians’ viewpoints on these categories. Twelve physicians participated in a survey, leading to revisions in 21 HL7 categories. They later classified 600 clinical data items through a second survey using the updated categories. Participants’ perspectives were documented, and data analysis included descriptive measures and heat maps. In the first survey, six participants suggested adding 19 new categories (e.g., personality disorder), and modifying 25 category definitions. Two new categories and sixteen revised category definitions were incorporated to support more patient-friendly content and inclusive language. Fifteen new category recommendations were addressed through a revision of category definitions (e.g., personality disorder described as a behavioral health condition). In the second survey, data categorizations led to recommendations for more categories from ten participants. Future revisions of the HL7 categories should incorporate physicians’ viewpoints, validate the categories using patient data or/and include patients’ perspectives, and develop patient-centric category specifications.

Ibrutinib-based therapies are costly and require continuous administration. We hypothesized combining BTK inhibition with anti-CD20 monoclonal antibodies would yield deep remissions allowing discontinuation. We enrolled 32 therapy-naïve CLL patients to receive ibrutinib plus obinutuzumab, followed by single-agent ibrutinib. Patients could discontinue ibrutinib after 36 months with sustained complete response (CR). We evaluated treatment safety, efficacy, and outcomes after ibrutinib discontinuation. The overall response rate was 100%, 28% achieved a CR, and 12.5% achieved bone marrow undetectable minimal residual disease. At a three-year median follow-up, 91% remain in remission with 100% overall survival. Five patients in sustained CR stopped ibrutinib and have not progressed. Eight non-CR patients discontinued for other reasons, with only two progressing. The treatment was safe, with a lower IRR rate. All patients responded to treatment with longer time-to-progression after discontinuation of ibrutinib. Our data support the evaluation of ibrutinib discontinuation strategies in more extensive clinical trials (https://Clinicaltrials.gov Identifier https://clinicaltrials.gov/ct2/show/NCT02315768).

Abstract Introduction: CAR T-cell therapy has revolutionized the treatment of patients with relapsed/refractory (R/R) acute leukemia, NHL, and multiple myeloma. However, there are still areas of improvement in their clinical activity, source of the effector cells, prevention, and management of adverse events that require particular attention. Because of those reasons, NK cells appear as a viable effector cell alternative that can help address these challenges. NK cells offer a profile of activation, expansion, persistence, and cytotoxicity that is different from T cells and, when modified to bear CAR constructs, may provide significant advantages. However, the preclinical development of NK-CARs is challenging mainly because of the difficulty of generating large quantities of cells for testing and well-established pathways for CAR optimization before in vivo evaluation. Therefore, we developed a CAR optimization platform using the NK-92 cell line. NK-92 cells conserve their cytotoxic ability and can be easily expanded in vitro and used for functional and phenotypical evaluations of novel CAR-NK constructs. Here we present a rechallenge cytotoxic assay that mimics repetitive in vivo effector interactions with the target cells and its use for optimization, comparison, and development of NK-based cellular therapies. Methods: We generated lentivirus transduced CD19 CARs (FMC63-41BB-z) using T cells from healthy donors and NK-92 cells for comparison.T cells were expanded for 12 days, and a 41.9% CAR+ expression was achieved (CART19). Transduced NK-92 cells were sorted by FACS to obtain a population of 98.3 % CAR+ cells (CARNK19) and subsequently expanded for 12 days. JeKo-1 cells were used as CD19+ targets and BxPC3 cells as CD19 neg control (both cell types were GFP-Luc-PuroR). We developed a Luciferase-based rechallenge cytotoxicity assay. For this, we diluted the effector to target (E/T) ratio to obtain a logarithmic trendline of the cells' cytotoxicity. E/T ratio to get viability of 50% (IC50) measured at 4h (for CARNK19) and 24h (for CART19) was used as a proxy of the product's potency. Both CAR Immune Effector Cells (IECs) were co-cultured with their targets at an E/T ratio to obtain 70% cytotoxicity. After 24 hours with the target, we estimated the remaining IEC amount in the culture using GFP exclusion in flow analysis (IEC cells/mL = total cells/mL x GFP neg%). We repeated the plating of E/T ratio dilutions to perform daily IC50 curves using this rechallenge strategy for a total of 5 days. CAR and PD1 expression were measured on Day 0 and Day 5 by flow cytometry. Results: CART19 showed a higher IC50 than CARNK19 at baseline, 1.7 vs. 0.19 (Figure 1A). The IC50 trend of both IECs over time showed an uptrend that suggests progressive functional exhaustion (Figure 1B). At 5 days of rechallenge, it was 29 times higher in T cells than in NK-92 (12.07 vs. 0.42) and with a slope 265 times higher (10.6 vs. 0.04). Furthermore, we observed that when comparing the levels of CAR expression on Day 0 vs. Day 5, CART19 showed a decrease in CAR expression that was not present in CARNK19 (41.9 to 10.9% vs. 98.3 to 95.5%) (Figure 1C). In addition, there was a higher increase in PD1 expression in CART19 cells than CARNK19 cells from Day 0 to Day 5 of the in vitro rechallenge (9.9 to 46.8% vs. 0.88 to 8.88%) (Figure 1D). Conclusion: Our data shows the use of NK-92 cells as a tool for optimization and preclinical development of NK cell-based cellular therapies. We demonstrated that it is feasible to set up repetitive cytotoxic challenges that mimic closer in vivo E/T engagement. Moreover, using the cytotoxic IC50 calculated with this platform, we show increased cytotoxicity, less functional exhaustion, and less expression of PD1 in CARNK19 than in its T cell counterpart. Overall, the NK-92 rechallenge cytotoxicity assay platform constitutes a helpful tool for research, development, and optimization of cellular therapies based on NK cell effector function. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.