Background
Phase 3, open-label, randomized controlled trial (GLOW; PCYC-1142). N=211 previously untreated CLL/SLL patients aged ≥65 or with CIRS >6 (older/unfit). Ibrutinib-venetoclax (I+V) is an all-oral, once-daily, fixed-duration combination; chlorambucil-obinutuzumab (Clb+G) was the established standard from CLL11. Treatment: I+V = 3 cycles ibrutinib lead-in → 12 cycles I+V → stop; Clb+G = 6 cycles. Randomized 1:1. Median age 71 years.
Interventions and follow up
Arm A: Ibrutinib 420 mg PO daily × 3 cycles (lead-in) → ibrutinib 420 mg + venetoclax 400 mg/d (ramp-up over 5 weeks) for 12 cycles q28d → treatment cessation (all-oral fixed-duration, ~15 months total)
Arm B: Obinutuzumab 1000 mg IV (days 1, 8, 15 cycle 1, then day 1 cycles 2–6) + chlorambucil 0.5 mg/kg PO days 1 and 15 q28d × 6 cycles (Clb+G)
Primary endpoint: Sustained uMRD in peripheral blood from 3–12 months after end of treatment
Median follow-up: 27.7 months (primary); 46.9 months (Niemann Lancet Oncol 2023)
Arm B: Obinutuzumab 1000 mg IV (days 1, 8, 15 cycle 1, then day 1 cycles 2–6) + chlorambucil 0.5 mg/kg PO days 1 and 15 q28d × 6 cycles (Clb+G)
Primary endpoint: Sustained uMRD in peripheral blood from 3–12 months after end of treatment
Median follow-up: 27.7 months (primary); 46.9 months (Niemann Lancet Oncol 2023)
Results
Sustained uMRD (PB, post-EOT): 84.5% vs 29.3% (I+V vs Clb+G), P<.001
PFS (primary): HR 0.216 (95% CI 0.131–0.357), P<.001
4-yr update (PMID 37944541): mPFS NR vs 23.1 months, HR 0.206 (P<.001); 42-mo PFS 69.1% vs 28.0%
CR rate: 42% vs 17%
OS: HR 0.487 (P=.22) at primary — not significant
PFS (primary): HR 0.216 (95% CI 0.131–0.357), P<.001
4-yr update (PMID 37944541): mPFS NR vs 23.1 months, HR 0.206 (P<.001); 42-mo PFS 69.1% vs 28.0%
CR rate: 42% vs 17%
OS: HR 0.487 (P=.22) at primary — not significant
Adverse events
Hematologic: Grade ≥3 neutropenia 34.9% (I+V) vs 49.5% (Clb+G); overall grade ≥3 AEs 75.5% vs 69.5%
Cardiovascular: AFib grade ≥3 6.6% and hypertension grade ≥3 6.6% (ibrutinib component)
Tumor lysis / infusion: No TLS reported (ibrutinib lead-in reduces TLS risk); infusion reactions confined to Clb+G arm
Discontinuation due to AEs: 18% (I+V) vs 15% (Clb+G)
Cardiovascular: AFib grade ≥3 6.6% and hypertension grade ≥3 6.6% (ibrutinib component)
Tumor lysis / infusion: No TLS reported (ibrutinib lead-in reduces TLS risk); infusion reactions confined to Clb+G arm
Discontinuation due to AEs: 18% (I+V) vs 15% (Clb+G)
Conclusions
Ibrutinib-venetoclax fixed-duration achieved dramatically superior uMRD (84.5% vs 29.3%) and PFS over Clb+G in older/unfit treatment-naive CLL, with the practical advantage of treatment cessation at ~15 months. The all-oral fixed-duration regimen represents an advance in managing CLL in elderly patients.
Key Limitations
Clb+G is a weak comparator by contemporary standards; CLL17 (I+V, VenO, and continuous ibrutinib head-to-head) provides more clinically relevant data. No OS benefit at primary analysis. AFib risk from the ibrutinib component (6.6% grade ≥3) persists despite limiting treatment to 15 months. The 3-month ibrutinib lead-in adds duration and complexity; zanubrutinib-venetoclax combinations are under investigation. Patients intolerant of ibrutinib are not candidates.
Clinical Context
GLOW data supported FDA approval of ibrutinib+venetoclax (fixed-duration) for CLL in 2024. Together with CAPTIVATE (younger patients), this established fixed-duration I+V as an all-oral alternative to VenObi (CLL14). CLL17 subsequently showed non-inferiority of VenO, VenI (fixed-duration), and continuous ibrutinib at 3-year follow-up. ESMO-MCBS: not yet formally assigned.