sum tests were used to compare categorical and non-categorical variables, respectively. Results: Twenty-one pts who received cyclophosphamide and fludarabine lymphodepletion followed by 2x10 CD19 CAR-T cells/kg are included in this study. Eight pts (38%) had FL and 13 (62%) had tFL. The FL pts had received a median of 4 prior therapies (range, 2-7); all had failed chemoimmunotherapy with an anti-CD20 antibody and alkylating agents; 75% had progressive disease after the last therapy; and 50% had failed prior autologous (n=3) or allogeneic (n=1) hematopoietic cell transplantation. Before lymphodepletion, 75% had stage III or IV disease; 62% had extranodal involvement; and 75% had intermediate or high FLIPI score. Seven of 8 pts with FL achieved complete remission (CR, 88%; 95% CI, 47-99) after CAR-T cells. The median time to CR was 29 days (range, 27-42), and all who achieved CR remained in remission without additional therapy (median followup, 24 months). Despite high-risk disease, durable CR was observed in most FL pts, indicating this therapy should be further investigated in larger studies. For the 13 pts with tFL, the best overall response without additional therapy was 46% (95% CI, 20-74), with all responding pts achieving CR. For tFL pts who achieved CR, the median progression-free survival (PFS) was 11.2 months (95% CI, 3.3-NR; median follow-up 38 months). The median PFS for all pts with tFL was 1.4 months (95% CI, 1.2-NR) [Figure 1]. Pts with FL and tFL had comparable baseline and treatment characteristics; however, more tFL pts had elevated lactate dehydrogenase (LDH; FL vs tFL, 13% vs 69%, P = .02) and fewer had bone marrow involvement (50% vs 15%, P = .15). No significant differences were observed between FL and tFL pts in peak CART cell counts in blood, or the incidence and severity of cytokine release syndrome (CRS) or neurotoxicity (NT). No severe (grade ≥3) CRS or NT were observed. Conclusions: CD19 CAR-T cell immunotherapy is highly effective in adults with clinically aggressive R/R FL, with durable CR in a high proportion of FL pts.