Background: Pts with R/R LBCL after first-line (1L) treatment (tx) who are unable to undergo high-dose chemotherapy (HDCT) and HSCT have poor outcomes and limited tx options. PILOT (NCT03483103) evaluated liso-cel, an autologous, CD19-directed chimeric antigen receptor (CAR) T cell product, as 2L tx in pts with R/R LBCL not intended for HSCT. Methods: Eligible pts were adults with R/R LBCL after 1L tx who were not deemed candidates for HDCT and HSCT by their physician and met ≥ 1 frailty criteria: age ≥ 70 yr, ECOG PS = 2, DLCO ≤ 60%, LVEF < 50%, CrCl < 60 mL/min, or ALT/AST > 2 × ULN. Bridging tx was allowed. Pts received lymphodepletion with cyclophosphamide and fludarabine, followed 2–7 days later by liso-cel at a target dose of 100 × 10⁶ CAR⁺ T cells. Cytokine release syndrome (CRS) was graded per Lee 2014 criteria and neurological events (NE) per NCI CTCAE, version 4.03. Primary endpoint was ORR per independent review committee (IRC); all pts had ≥ 6 mo follow-up (f/u) from first response. Results: Of 74 pts leukapheresed, 61 received liso-cel and 1 received nonconforming product. Common reasons for pre-infusion dropout included death and loss of eligibility (5 each). For liso-cel–treated pts, median age was 74 yr (range, 53–84; 79% ≥ 70 yr) and 69%, 26%, and 5% met 1, 2, and 3 frailty criteria, respectively; 26% had ECOG PS = 2 and 44% had HCT-CI score ≥ 3. After 1L tx, 54% were chemotherapy refractory, 21% relapsed ≤ 12 mo, and 25% relapsed > 12 mo; 51% of pts received bridging chemotherapy. Median (range) on-study f/u was 12.3 mo (1.2–26.5). ORR and CR rate was 80% and 54%, respectively. Median DOR and PFS was 12.1 mo and 9.0 mo, respectively. Median OS has not been reached (Table). Most frequent tx-emergent AEs (TEAE) were neutropenia (51%), fatigue (39%), and CRS (38%), with grade (gr) 3 CRS in 1 pt (2%) and no gr 4/5 CRS. Any-grade NEs were seen in 31%, gr 3 in 5% (n = 3), and no gr 4/5 NEs; 7% received tocilizumab, 3% corticosteroids, and 20% both for tx of CRS/NEs. Overall, gr ≥ 3 TEAEs occurred in 79%, with gr 5 in 2 pts (both due to COVID-19). Two pts (3%) had gr 3/4 infections and 15 (25%) had gr ≥3 neutropenia at Day 29. Conclusions: In the PILOT study, liso-cel as 2L tx in pts with LBCL who met ≥ 1 frailty criteria and for whom HSCT was not intended demonstrated substantial and durable overall and complete responses, with no new safety concerns. Clinical trial information: NCT03483103.