Comparative efficacy of zanubrutinib plus obinutuzumab versus last prior treatment in relapsed/refractory follicular lymphoma: growth modulation index analysis from the ROSEWOOD study

BACKGROUND: The phase II ROSEWOOD study (NCT03332017) compared zanubrutinib plus obinutuzumab (ZO) with obinutuzumab monotherapy (O) in patients with relapsed/refractory (R/R) follicular lymphoma (FL) who had received two or more prior lines of systemic therapy. Median progression-free survival (PFS) was longer with ZO versus O [28.0 versus 10.4 months; hazard ratio 0.50, 95% confidence interval (CI) 0.33-0.75]. MATERIALS AND METHODS: In this post hoc analysis, an intra-patient comparative analysis was carried out using the growth modulation index (GMI) to analyze the efficacy of ZO versus the last prior treatment received by patients in the ROSEWOOD study. A GMI of ≥1.33 was used as a threshold for significant clinical activity. RESULTS: In the overall population, median GMI was 2.7 (95% CI 1.6-4.9) in the ZO arm and 0.9 (95% CI 0.5-1.7) in the O arm. Analysis in subgroups of clinical interest in the ZO arm showed that PFS was longer with ZO than with the last prior treatment, and median GMI was ≥1.33 in all subgroups tested. Overall, PFS had improved (GMI ≥1.33) in >60% of patients with R/R FL who received ZO versus their last prior treatment. CONCLUSIONS: This GMI analysis further supports the benefit of ZO as a novel therapeutic option for patients with R/R FL.