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tory (R/R) FL or DLBCL have poor outcomes. Polatuzumab vedotin (pola), an antibody drug conjugate that targets delivery of the microtubule inhibitor MMAE to cells expressing CD79b, + rituximab (R) has showed promising responses in R/R FL and DLBCL. Adding bendamustine (B) to pola‐R and substituting obinutuzumab (G) for R could improve outcomes. We report updated results from the Phase (P) 1b/2 study evaluating pola + BR or BG and the P2 expansion cohorts evaluating pola + BG in patients (pts) with R/R FL and DLBCL (ClinicalTrials.gov NCT02257567). Methods: All pts provided informed consent to participate in the study and were treated with pola (1.8 mg/kg) + B (90 mg/m) and R (375 mg/ m) or G (1000 mg) every 28 days (FL) or 21 days (DLBCL) for 6 cycles. Responses were assessed by modified Lugano 2014 criteria after 3 cycles, end of treatment (tx), and every 6 months (mo) for 2 years during follow‐up (fu). Results: As of 14 Nov 2016, 65 pts were enrolled: 24 pts (12 FL, 12 DLBCL) in P1b and 41 pts (20 FL and 21 DLBCL) in P2. In safety evaluable pts, FL pts (N = 32) were median age 63 yr (37– 86), 82% ECOG 0–1, 6% ECOG 2, 44% FLIPI1 3–5, 78% Stage III/IV, 2 (1–7) median lines of prior tx, 38% refractory to last tx, 13% prior transplant (BMT). DLBCL pts (N = 32) were median age 66 (30–86), 88% ECOG 0–1, 13% ECOG 2, 59% IPI 3–5, 75% Stage III/IV, 2 (1–7) median lines of prior tx, 82% refractory to last tx, 3% prior BMT. Among 64 pts who received ≥1 dose, adverse events (AEs) that occurred in >20% of pts were fatigue (67%), nausea (54%), diarrhea (54%), vomiting (42%), pyrexia (39%), and constipation (39%). As expected, grade (Gr) 3/4 cytopenias were common: neutropenia (34% FL, 28% DLBCL), thrombcytopenia (16% FL, 13% DLBCL), and anemia (6% FL, 9% DLBCL). Tx emergent neuropathy occurred in 19/ 64 (30%) of pts, with 1 Gr 3 event, and led to pola discontinuation in 1 pt, dose reduction in 2 pts, and interruption in 1 pt. In FL (n = 32), 75% (24/32) had Gr 3/4 AEs and 41% (13/32) had serious AEs (SAEs). The only SAE occurring in ≥10% was infection (22%). The most common Gr 3/4 non‐heme AEs were infection (16%) and hypokalemia (9%). AEs led to study tx discontinuation in 6 pts. B was stopped in 2 pts due to Gr 3 thromboctyopenia. Of 4 deaths, 2 were PD and 2 were Gr 5 AEs (1 tx related: PML). In DLBCL (n = 32), 88% (28/32) had Gr 3/4 AEs and 63% (20/32) had SAEs. SAEs occurring in ≥10% of pts were infection (33%) and pyrexia (22%). The most common Gr 3/4 non‐heme AEs were febrile neutropenia (13%), fatigue (13%), and diarrhea (13%). AEs led to study tx interruption in 19 pts and discontinuation in 8 pts. There were 13 deaths: 9 PD, 4 AE (all unrelated to tx).Responses are shown in Table1. Median duration of response (DoR) for FL P1b pts was 16 mo (median fu 14.5 mo) but not reached for FL P2 (median fu 6.5 mo) and DLBCL P1b/2 (median fu 13.7 mo P1b, 6.4 mo P2). Conclusions: Updated evaluation of pola + BR and pola + BG shows promising durable responses and an acceptable safety profile in heavily pre‐treated R/R FL and DLBCL pts. Safety and efficacy data will be updated at the time of presentation.