Polatuzumab vedotin + obinutuzumab + venetoclax in patients with relapsed/refractory (R/R) follicular lymphoma (FL): Primary analysis of a phase 1b/2 trial.

Abstract

7534 Background: Polatuzumab vedotin (Pola) + obinutuzumab (G) demonstrated activity and tolerability in a Phase 1b/2 trial of patients (pts) with R/R FL (Phillips, et al. Blood 2016). Preclinical studies with venetoclax (Ven) showed that concurrent treatment with Pola promotes MCL-1 degradation, a known mechanism of resistance to Ven, and enhances in vivo anti-tumor efficacy (Amin, et al. AACR 2020). Here, we report the primary safety/efficacy analysis with Pola-G-Ven in a Phase 1b/2 study of pts with R/R FL (GO29833; NCT02611323). Methods: Pts received induction treatment every 21 days (D) x six cycles (C) of: Pola 1.4–1.8mg/kg intravenously (IV) in dose escalation (DE) or recommended Phase 2 dose (RP2D) on D1; G 1000mg IV (C1: D1, D8, D15; C2–6: D1); and oral Ven 200–800mg (DE or RP2D; D1–21). Pts with complete response/partial response/stable disease (CR/PR/SD) at end of induction (EOI) received maintenance with G (1000mg on D1 every 2 months [mo] for 24 mo) and Ven (200–800mg daily) for 8 mo. Primary endpoints were safety/tolerability and positron emission tomography (PET)-CR rate at EOI by independent review committee (IRC) using modified Lugano criteria. Results: At the primary analysis (Oct 05, 2020), 74 pts were enrolled. Median pt age was 64 years (range 36–78); male (57%); Ann Arbor Stage III–IV (86%); FL International Prognostic Index high risk ≥3 (55%); bulky disease ≥7cm (16%); prior lines of therapy ≥2 (74%); refractory to: last prior therapy (51%), any prior anti-CD20 therapy (55%), both anti-CD20 therapy and an alkylating agent (double refractory; 55%). Grade 3–4 adverse events (AEs) were experienced by 73% of pts; most commonly, neutropenia (39%), thrombocytopenia (19%), and infections (16%; mainly pneumonia). AEs led to dose reduction in 38% and interruption in 68% of pts (mainly modifications to Ven). One fatal AE was reported (pneumonia). In total, 49 pts were treated at RP2D (Pola 1.8mg/kg + Ven 800mg) and were evaluable for efficacy. PET-CR rate at EOI by IRC was 57% (Table). With a median follow-up of 14.4 mo (range 8.2–28.4), the 12-mo progression-free survival (PFS) was 73% (95% confidence interval: 59.4–86.9). Median PFS was not reached. Conclusions: The safety profile of Pola-G-Ven is consistent with the known profiles of the individual drugs. Response rates at EOI with Pola-G-Ven are encouraging in this R/R FL patient population. Additional follow-up is needed to assess PFS benefit during maintenance treatment and beyond. Clinical trial information: NCT02611323. [Table: see text]