Background: Progress in chimeric antigen receptor (CAR) T-cell therapy has included reduction in life-threatening toxicity. Rates of severe cytokine release syndrome (CRS) have declined from 50% in early trials to 7% in the most recent real-world experience. However, rates of severe immune effector cell-associated neurotoxicity (ICANS) associated with axicabtagene ciloleucel (Axicel) remain unchanged. IL-1 is a major driver of ICANS pathophysiology that is produced upstream of IL-6. The IL-1 receptor antagonist, Anakinra, can prevent neurotoxicity in animal models when given at fever onset. We present our early experience of the first 13 participants enrolled into a phase II trial evaluating Anakinra to prevent severe ICANS (NCT4205838). Methods: This investigator-sponsored trial included adults eligible for standard-of-care Axicel for large B-cell lymphoma after ≥2 lines of intensive chemoimmunotherapy. Participants received Anakinra 100 mg SQ q6h x 12-36 doses until ICANS returned to grade ≤1. The trigger to initiate Anakinra was any grade ICANS or grade ≥3 CRS in the absence of ICANS. A protocol modification, made after the first 3 participants were treated, changed the trigger for Anakinra to grade ≥2 CRS. In addition to Anakinra, all participants received standard-of-care interventions for CRS and ICANS. The primary objective is to estimate the efficacy of Anakinra in preventing severe ICANS (grade ≥3) according to ASTCT 2018 consensus grading. Results: To date, 13 participants have been enrolled, and 7 met criteria to initiate Anakinra and received the first dose prior to severe ICANS. Median age was 56 years (range, 23-84 years). Of the 7 participants whom received Anakinra prior to severe ICANS, only 1 of 7 (14%) developed grade 3 ICANS. The most common adverse event was injection site reaction, which peaked at grade 2. There were no unexpected toxicities. Once the protocol was amended to initiate Anakinra for grade ≥2 CRS (N = 4), no participant developed severe ICANS, and only one participant met the institutional standard to receive corticosteroids (Table). Conclusions: Anakinra is feasible to initiate in the non-prophylactic setting in patients at increased risk for severe ICANS. These early results demonstrate potential to reduce severe ICANS associated with Axicel to a rate similar to other CAR T-cell products, and to reduce corticosteroid use. Further enrollment to the pre-planned sample size of N=36 is required to demonstrate statistical efficacy. Serum IL-1 analysis is also ongoing. Clinical trial information: NCT4205838