Efficacy & Tolerability of Ibrutinib/Venetoclax in Untreated CLL

Chronic Lymphocytic LeukemiaA 64-month follow-up of the GLOW study reaffirms the efficacy and tolerability of ibrutinib plus venetoclax (Ibr+Ven) over chlorambucil and obinutuzumab (Clb+O) in untreated CLL, highlighting sustained progression-free survival, overall survival, and reduced need for second-line therapy. The findings were presented at the 66th ASH Annual Meeting and Exposition (Abstract 1871). The GLOW study randomized 211 patients in a 1:1 ratio to either Ibr+Ven or Clb+O. Patients in the Ibr+Ven arm received a 3-cycle ibrutinib lead-in followed by 12 cycles of combination therapy, while the Clb+O arm included 6 cycles of treatment. Outcomes were evaluated based on progression-free survival (PFS), time to next treatment, overall survival (OS), and Grade 3/4 treatment-emergent adverse event (TEAE)-free PFS. Additionally, minimal residual disease (MRD) was assessed 3 months post-treatment completion (EOT+3). Long-Term Efficacy & Subgroup Insights At 64 months, the Ibr+Ven combination demonstrated robust long-term efficacy, significantly reducing the risk of progression or death by 73 percent compared to Clb+O (HR: 0.27; P<.0001). The 60-month PFS rates were 59.9 percent for Ibr+Ven and 17.8 percent for Clb+O. Subgroup analysis showed that the PFS benefit was consistent across genetic profiles, with patients having unmutated IGHV experiencing a PFS HR of 0.26 (P<.0001), while those with mutated IGHV demonstrated a similar advantage (HR: 0.24; P=.0014). Patients achieving undetectable MRD (uMRD) at EOT+3 also showed improved 48-month PFS rates (69% vs. 61% for detectable MRD). The OS analysis further highlighted the benefit of Ibr+Ven, with a 54 percent reduction in the relative risk of death (HR: 0.46; P=.004). The 60-month OS rates were 81.6 percent for Ibr+Ven and 60.8 percent for Clb+O, with mIGHV patients experiencing the most pronounced survival benefits (HR: 0.22; P=.010). Safety & Tolerability The analysis also emphasized the tolerability of Ibr+Ven. Despite a slightly longer time experiencing Grade 3/4 toxicities (2 months for Ibr+Ven vs. 1 month for Clb+O), patients in the Ibr+Ven arm had a significantly longer period of AE-free PFS—50 months compared to 30 months for Clb+O. This 20-month improvement reflects the regimen's ability to maintain effective disease control with manageable toxicity, offering valuable insights for clinical decision-making. To gain additional insights into the study, Oncology Times chatted with lead study author, Carsten Utoft Niemann, MD, PhD, who is affiliated with the Department of Hematology, Copenhagen University Hospital - Rigshospitalet in Denmark. Oncology Times: How do the 64-month follow-up results of the GLOW study reinforce the efficacy of Ibr+Ven over Clb+O for elderly or comorbid patients with untreated CLL? Niemann: “BTK inhibitors such as Ibr and BCL2 inhibitors such as Ven have significantly improved the treatment landscape of CLL. With 64-month follow-up, Ibr+Ven continues to show superior PFS, reduced risk of requiring second-line therapy, and sustained OS advantage over Clb+O in this population. “At a median follow-up of 64 months, Ibr+Ven prolonged PFS, reducing the risk of progression or death by 73 percent versus Clb+O. The 60-month PFS rates were 59.9 percent for Ibr+Ven and 17.8 percent for Clb+O.” Oncology Times: What are the implications of the superior PFS observed with Ibr+Ven, particularly for patients with unmutated IGHV status? Niemann: “Ibr+Ven significantly prolonged PFS regardless of IGHV status, with estimated 60-month PFS rates of 52.2 percent for patients with unmutated IGHV and 82.5 percent for those with mutated IGHV.” Oncology Times: What practical considerations should clinicians keep in mind when weighing the longer treatment duration and associated toxicity of Ibr+Ven against its robust efficacy and tolerability profile? Niemann: “At 64 months of follow-up, the time patients spent without significant toxicity or progression was significantly longer for Ibr+Ven versus Clb+O (52 vs. 31 months, respectively). These results show a 20-month improvement in TEAE-free PFS with Ibr+Ven versus Clb+O, indicating longer disease control without significant toxicity. These data provide valuable insights into the combination's durable efficacy and tolerability profile, offering a robust foundation for informed clinical decision-making in patients with previously untreated CLL.” Dibash Kumar Das is a contributing writer.