A study of a new mechanism: Intracellular retention allo-CART safety and efficacy for extranodal bulky B-NHL.

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e19007 Background: Extranodal bulky lesions, a significant adverse prognostic factor in lymphoma, commonly denote a more aggressive disease course, mandating prompt and intensified treatment strategies. In response, we developed ThisCART19A, a non-genetic editing and off-the-shelf anti-CD19 CAR T-cell therapy incorporating intracellular retention of membrane proteins, representing a novel approach that downregulates surface expression of TCRαβ/CD3 complexes. ThisCART19 has exhibited a favorable safety profile and promising efficacy in patients with relapsed/refractory bulky B-cell Non-Hodgkin Lymphoma. Methods: This is an investigator-initiated trial employing an open-label, dose escalation, and expansion design to evaluate the safety and efficacy of ThisCART19A in patients with relapsed or refractory bulky B-cell non-Hodgkin lymphoma (B-NHL). Bulky disease was defined as the longest diameter of the mass >5 cm at baseline. Results: Between June, 2021, and June, 2023, 13 extranodal bulky disease were enrolled in the studies and successfully received ThisCART19A. The median age was 56 (range, 37~67) years. All 13 patients had 3 median prior lines of therapy (range, 2-5). All patients received anti-CD20 and multi- agent chemotherapy. 8 (61.54%) patients had prior auto CART. mSPD was 48 (range, 16~162) cm². mTMTV was 114.9 (range, 14~483) ml. As of February 2024, The most common adverse events were CRS (100%) , infections (30.77%), ICANS (23.08%) and cytopenias(100%); This is no grade 3 or higher CRS occurred;only 1(7.69%)patient experienced grade 4 ICANS and relieved after intravenous dexamethasone treatment. This is no treatment-related deaths occurred. Among the 13 patients, 10 were evaluable, with an ORR and CR of 90% and 80%, respectively, at 28 days post-infusion. mPFS was 62 days (range, 28~227). The patient who achieved a PR received chemotherapy and radiotherapy as consolidation, As of February 5th, 2024, the patient has survived for 263 days and is still under follow-up. Additionally, two patients progressed after CR received sequential chemotherapy and BCL-2 Inhibitor, with an average OS of 326.5 days, still being under follow-up. In 13 evaluable patients, the mean C-max was 1043.13 cells/μL(range, 0.59~10045.4), and the mean AUC0-28d was 1542.23 cells/μL × day(range, 0.91~11724).In this cohort, two patients received low-dose infusions at 1×106 cells/kg and still achieved excellent expansion, the respective C-max were 726.432 cells/μL and 336.67 cells/μL. Conclusions: This CART19A exhibited favorable safety, remarkable expansion potential, and efficacy profiles in the treatment of r/r bulky lymphoma. Notably, it achieved a high ORR of 90%, providing a favorable window of opportunity for subsequent consolidation and intensification treatments. Moreover, this transition from a bulky to a non-bulky disease state reduces the intricacy of follow-up treatments. Clinical trial information: NCT04384393 .

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