Background: Epcoritamab is a CD20xCD3 bispecific antibody that induces T-cell–mediated killing of CD20–positive malignant B-cells. We present updated data, including progression-free survival (PFS) from the dose escalation part of the first-in-human phase 1/2 study of epcoritamab in pts with relapsed or refractory (R/R) B-cell non-Hodgkin lymphoma (B-NHL; NCT03625037). Methods: Adults with R/R CD20+ B-NHL received flat-dose 1 mL SC epcoritamab (step-up dosing approach) in 28-day cycles (q1w: cycles 1–2; q2w: cycles 3–6; q4w thereafter) until disease progression or unacceptable toxicity. Step-up dosing and standard prophylaxis were used to mitigate severity of cytokine release syndrome (CRS). Results: At data cut off (1/31/2021), 68 pts with B-NHL were enrolled across histologies including diffuse large B-cell lymphoma (DLBCL; n = 46 [67.6%]; de novo and transformed), follicular lymphoma (FL; 12 [17.6%]), mantle cell lymphoma (MCL; 4 [5.9%]), and others (6 [8.8%]). Majority were heavily pretreated (median [range] prior lines: DLBCL, 3 [1–6]; FL, 4.5 [1–18]); including prior CAR-T (n = 6) and prior ASCT (n = 10). At median follow-up of 14.1 mo (DLBCL, 10.2 mo; FL, 15.2 mo), treatment was ongoing in 15 (22%) pts. Most common treatment-emergent adverse events (AEs) were pyrexia (69%), CRS (59%), and injection site reaction (47%). CRS events were all grade 1 or 2 and most occurred in cycle 1; neurotoxicity was limited (6%; grade 1: 3%; grade 3: 3%; all transient). One case of tumor lysis syndrome was observed (1.5%; grade 3); there were no cases of febrile neutropenia or treatment-related death. Overall response is shown for DLBCL ≥12 mg and ≥48 mg and FL ≥12 mg, corresponding to the minimal efficacy threshold (Table). Responses deepened over time (PR converted to CR: DLBCL, 6 pts; FL, 3 pts). Median time to response was 1.4 mo (DLBCL) and 1.9 mo (FL). Among DLBCL pts achieving CR with ≥6 mg (n = 11), none relapsed while on treatment. The median PFS for pts with DLBCL ≥12 mg (n = 22) was 9.1 mo (95% CI: 1.6, NE; median follow-up 9.3 mo) and for pts with DLBCL ≥48 mg (n = 11) median PFS was not reached (median follow-up 8.8 mo). Updated analyses will be presented. Conclusions: With longer follow-up, SC epcoritamab demonstrated substantial single-agent activity, inducing deep and durable clinically meaningful responses, with a consistent safety profile. Notably no severe (grade ≥3) CRS events, no febrile neutropenia, and limited neurotoxicity was observed. Clinical trial information: NCT03625037