8009 Background: CD3×CD20 bispecific antibodies (bsAbs) have demonstrated promising results for the treatment of pts with R/R B-NHL. Epcoritamab is a novel subcutaneously administered bsAb with a favorable safety profile and encouraging preliminary anti-tumor activity at low doses in both aggressive and indolent B-NHL. Here we present updated safety and efficacy data from the ongoing trial (NCT03625037). Methods: Adults with R/R CD20+ B-NHL received a single SC injection of flat-dose epcoritamab in 28-day cycles (q1w: cycle 1–2; q2w: cycle 3–6; q4w thereafter) until disease progression or unacceptable toxicity. Primary objectives are determination of maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D). Secondary objectives include anti-tumor activity. Results: As of 8 Jan 2020, 41 pts with median age of 66 (range: 21–82) were enrolled. Most pts had DLBCL/HGBCL (73%) or FL (20%) and received a median (range) of 3 (1–6) and 5 (2–18) prior lines of treatment. No DLTs were observed (median follow-up: 4.7 mo; range: 3.7– 5.6). MTD has not been reached. Most common TEAEs (>35%) were pyrexia (71%), fatigue (46%), and injection site reaction (39%; all Gr 1). AEs of special interest included cytokine release syndrome (59%; all Gr 1/2; all resolved) and cytokine release-related decreased CARTOX-10 score (n=1). There was no clinical tumor lysis syndrome or treatment-related deaths. Treatment is ongoing in 13 pts. Anti-tumor activity was observed at minimal efficacy threshold (based on PK modelling) for DLBCL/HGBCL and FL (Table). Complete dose escalation data and RP2D will be presented. Conclusions: SC epcoritamab continues to demonstrate a favorable safety profile across all doses with no ≥Gr 3 CRS and no DLTs. Dose escalation data show improved efficacy as doses reach above the modeled predicted exposure threshold, inducing CRs in heavily pretreated DLBCL pts. All pts achieving CRs remain in remission. Clinical trial information: NCT03625037 . [Table: see text]