CLL-045: Long-Term Follow-up, Up to 7 Years, in the RESONATE-2 Study of First-Line Ibrutinib Treatment for Chronic Lymphocytic Leukemia (CLL)

Abstract

Objective: Report RESONATE-2 phase 3 study extended long-term follow-up of first-line ibrutinib vs chlorambucil in older patients with CLL/SLL. Methods: Patients (≥65 years [y]) with previously untreated CLL/SLL (without del[17p]) were randomly assigned 1:1 to once-daily ibrutinib 420 mg, until disease progression (PD) or unacceptable toxicity (n=136); or chlorambucil 0.5–0.8 mg/kg, up to 12 cycles (n=133). Outcomes included progression-free survival (PFS), overall survival (OS), overall response rate (ORR), and safety. Long-term responses were investigator-assessed per 2008 iwCLL criteria. Results: With up to 7y of follow-up (median, 74.9 months; range, 0.1–86.8), significant PFS benefit was sustained for patients treated with ibrutinib vs chlorambucil (HR 0.160 [95% CI: 0.111–0.230]). At 6.5y, PFS was 61% vs 9% for ibrutinib vs chlorambucil. PFS benefit was observed consistently, including ibrutinib-treated patients with high-risk genomic features of unmutated IGHV (HR 0.109 [95% CI: 0.063–0.189]) or del(11q) (HR 0.033 [95% CI: 0.010–0.107]). With ibrutinib, 6.5y OS was 78%; ORR was 92%, and complete response (CR/CRi) rate increased to 34%. Ongoing rates of grade ≥3 AEs of interest remained low for hypertension (5–6y interval: 5%, n=4; 6–7y: 4%, n=3) and atrial fibrillation (5–6y: 1%, n=1; 6–7y: 1%, n=1); no grade ≥3 major hemorrhage in 5–7y. One patient (1%) had dose reduction due to grade ≥3 AEs during years 5–6/6–7. Of 31 patients with dose reductions due to any-grade AEs over full follow-up, 22 (71%) had AE resolution/improvement. Primary reason for discontinuation was PD (5–6y: 5%, n=4; 6–7y: 6%, n=4). Any-grade AEs leading to discontinuations were 3% (n=2) in 5–6y and none in 6–7y. With up to 7y of follow-up, 47% of patients remain on single-agent ibrutinib. Conclusions: Long-term RESONATE-2 data demonstrate sustained PFS and OS benefit with first-line ibrutinib treatment for CLL, including for patients with high-risk genomic features. Responses continued to deepen over time. Rates of grade ≥3 AEs of interest continued to be low with rare further discontinuations and dose reductions due to AEs; most AEs leading to dose reduction resolved/improved. Ibrutinib remains well tolerated with no new safety signals. Funding: Pharmacyclics LLC, an AbbVie Company.