The combination of venetoclax, lenalidomide, and rituximab in patients with newly diagnosed mantle cell lymphoma induces high response rates and MRD undetectability.

7505 Background: MCL is a rare lymphoma without standard of care but several regimens have demonstrated clinical activity, the majority based on traditional chemotherapy. We hypothesized that adding venetoclax (V) to R2 would be safe and effective in pts irrespective age, morphology or stage. Here we present safety efficacy data from on-going phase 1b study + V with newly diagnosed MCL. Methods: This multi-center 1 (NCT03523975) enrolled aged ?18 yrs untreated The primary objective was characterize tolerability determine MTD. During induction (12 months (m)) received lenalidomide (L) 20 mg daily day 1-21, Rituximab (R) given weekly during c1 then every even cycle, escalated over 4 weeks 400 beginning 8. Each cycle 28 days (d). DLT period 42 d C1D8. In maintenance, R 8 for 36m, L at 10 half last dose 24 m minimum 12 m. No been transplanted. Pts progression (PD) came off study. MRD analyzed parallel scans by clonoSEQ assay (Adaptive Biotechnologies). Results: As Feb. 1st, 2021, all planned Pt characteristics/responses are summarized Table. Among who least one dose, median treatment duration so far 278d (IQR 170-560), still (Tx). pt unrelated condition. All w/o any DLTs noted. Treatment-emergent adverse events (TEAEs) were reported 100% pts, grade 3+ TEAEs 26 (93%) patients. most common all-grade (?50% pts), regardless relationship Tx, fatigue, neutropenia diarrhea. Grade ?3 ?50% (68%) thrombocytopenia (50%). withdrawn d/c Tx due AEs. There 5 event, non-evaluable pt, related PE occurred prior period. evaluable ORR (CR/PR) 96% (27/28 pts) CR/CRu 89%. Of responding two had PD, w/ CR PR. PD baseline TP53 mutation. testing successful pts. At time submission (71%) - -6 . Conclusions: Interim results show MTD combination daily, mg, manageable toxicity profile high Safety consistent AE noted each drug unexpected unique Updated including BH3 profiling will presented meeting. Clinical trial information: NCT03523975. [Table: see text]