Haemophagocytic lymphohistiocytosis (HLH) in patients with large B-cell lymphoma treated with standard of care (SOC) axicabtagene ciloleucel (Axi-cel).

8057 Background: HLH is a rare but serious complication of chimeric antigen receptor (CAR) T cell therapy, characterized by severe immune activation, and immune mediated multi-organ failure. Diagnosis is difficult in the context of cytokine release syndrome (CRS) and optimal treatment and outcomes are unclear. Methods: Retrospective, descriptive analysis of patients with relapsed/refractory LBCL treated with SOC axi-cel at MD Anderson Cancer Center between 01/2018 - 10/2019 (data cut-off 12/21/2019). Progression-free survival (PFS) defined as time from axi-cel infusion to progression/death or last follow-up. Diagnosis of HLH per HLH-2004 and CART cell therapy toxicity guidelines (Neelapu, 2018) Results: One hundred and five patients with relapsed/refractory LBCL included, 6 diagnosed with HLH. No significant difference in baseline characteristics, disease stage, international prognostic index or inflammatory markers at baseline between groups, with exception of platelet count which was lower in HLH group 116 [37-129] versus 141 [9-391] (p = 0.07). Development of HLH was early after CART cell infusion at a median 11 days [7 – 78 days] with 3 patients having bone marrow hemophagocytosis; all 6 had abnormalities in liver function tests, fibrinogen, triglycerides, and at least 1 ferritin level > 10,000. CART toxicity in HLH cohort: 4 patients experienced grade 0-1 CRS, and 1 with grade 2 CRS while 3 HLH patients experienced grade 3-4 IEC-associated neurotoxicity syndrome ( ICANS), and 2 patients had grade 0-1 ICANS. Five HLH patients treated with high dose steroids, and tocilizumab; anakinra administered in 2 patients. Four of 6 patients had resolution of HLH with treatment and didn’t require escalation to HLH specific therapy however 1 patient was treated with steroids/etoposide. PFS and overall survival (OS) were significantly shorter in HLH group, PFS 1 months vs 8 months, respectively (p < 0.001) and median OS 2 months vs not reached, respectively (p = 0.001) follow up 10 months (95% CI 8-12 months). One patient died of acute respiratory failure, 2 patients died of HLH and multi-organ failure without progressive disease (PD). Of 3 remaining patients, all had radiographic PD at day 30, 2 of whom died of PD. Conclusions: HLH is likely an underreported complication of CART cell therapy, and patients with HLH have significantly worse outcomes. In this series the majority of patients died of PD, not the syndrome itself. More information is necessary to design treatment strategies that won’t compromise CART outcomes.