A phase I trial using CD19 CAR-T expressing PD-1/CD28 chimeric switch-receptor for refractory or relapsed B-cell lymphoma.

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7557 Background: The anti-CD19 chimeric antigen receptor (CAR)-T cell therapy has established efficacy in the treatment of refractory or relapsed (R/R) B-cell lymphoma. However, the existence of different immunosuppressive pathways such PD-1/PD-L1 pathway can restrict the full potential of CAR-T therapy. A recent study demonstrates that a novel PD-1/CD28 chimeric switch-receptor, comprising the extracellular domain of PD-1 and the transmembrane and cytoplasmic signaling domains of CD28, can be used a modality for augmenting antitumor activity of mesothelin- and prostate specific cancer antigen-specific CAR-T cells in either pleural mesothelioma or prostate cancer xenograft model. Here, we describe the first human trial of CD19-PD-1/CD28-CAR-T cells (a CD19-specific CAR-T expressing PD-1/CD28 chimeric switch-receptor) to evaluate safety and efficacy. Methods: This phase I, single-arm, open-label, multicenter trial enrolled patients (18-75 years) with R/R large B-cell lymphoma. PD-L1 expression was confirmed by immunohistochemistry using an anti-PD-L1 mAb (SP142), and confirmed by the review committee with a central evaluation. Seventeen patients received conditioning chemotherapy (cyclophosphamide [500 mg/m2] and fludarabine [30 mg/m2] on days -5, -4 and -3) and followed by CD19-PD-1/CD28-CART cells infusion at doses ranging 0.5 to 4 × 106 CAR+ T cells/kg on day 0. Response was assessed by F-FDG PET/CT at month 3 after CAR-T infusion, according to the International Working Group Response Criteria for Malignant Lymphoma, and duration of response was evaluated by ultrasonic and computed tomography every three months from month 3 to month 12. Results: At data cutoff, 17 patients had received CD19-PD-1/CD28-CART cells. Overall PD-L1 positivity was 15/17 (88.2%) and the mean percentage of PD-L1 positivity was 19.7% (range, 5-50%). Fourteen patients (82.35%) developed cytokine release syndrome (grade ≤ 2) and four (23.53%) developed neurotoxicity (grade = 1), which was reversible in all. The overall response rate was 58.8% (10/17) and complete remission rate was 41.2% (7/17). At a median follow-up 5 months, median overall survival for all patients was not reached. Conclusions: This trial showed the feasibility, controllable toxicities, and effective activity of CD19-PD-1/CD28-CART cells for treating patients with R/R B-cell lymphoma, providing the first proof-of-principle of the potential therapeutic value of targeting the PD-1/PD-L1 pathway in lymphoma in the clinical setting. Clinical trial information: NCT03258047.