Carol Moreno

BACKGROUND: In patients with chronic lymphoid leukemia (CLL) or small lymphocytic lymphoma (SLL), a short duration of response to therapy or adverse cytogenetic abnormalities are associated with a poor outcome. We evaluated the efficacy of ibrutinib, a covalent inhibitor of Bruton's tyrosine kinase, in patients at risk for a poor outcome. METHODS: In this multicenter, open-label, phase 3 study, we randomly assigned 391 patients with relapsed or refractory CLL or SLL to receive daily ibrutinib or the anti-CD20 antibody ofatumumab. The primary end point was the duration of progression-free survival, with the duration of overall survival and the overall response rate as secondary end points. RESULTS: At a median follow-up of 9.4 months, ibrutinib significantly improved progression-free survival; the median duration was not reached in the ibrutinib group (with a rate of progression-free survival of 88% at 6 months), as compared with a median of 8.1 months in the ofatumumab group (hazard ratio for progression or death in the ibrutinib group, 0.22; P<0.001). Ibrutinib also significantly improved overall survival (hazard ratio for death, 0.43; P=0.005). At 12 months, the overall survival rate was 90% in the ibrutinib group and 81% in the ofatumumab group. The overall response rate was significantly higher in the ibrutinib group than in the ofatumumab group (42.6% vs. 4.1%, P<0.001). An additional 20% of ibrutinib-treated patients had a partial response with lymphocytosis. Similar effects were observed regardless of whether patients had a chromosome 17p13.1 deletion or resistance to purine analogues. The most frequent nonhematologic adverse events were diarrhea, fatigue, pyrexia, and nausea in the ibrutinib group and fatigue, infusion-related reactions, and cough in the ofatumumab group. CONCLUSIONS: Ibrutinib, as compared with ofatumumab, significantly improved progression-free survival, overall survival, and response rate among patients with previously treated CLL or SLL. (Funded by Pharmacyclics and Janssen; RESONATE ClinicalTrials.gov number, NCT01578707.).

The chronic lymphocytic leukemia (CLL) immunoglobulin repertoire is biased and characterized by the existence of subsets of cases with closely homologous ("stereotyped") complementarity-determining region 3 (CDR3) sequences. In the present series, 201 (21.9%) of 916 patients with CLL expressed IGHV genes that belonged to 1 of 48 different subsets of sequences with stereotyped heavy chain (H) CDR3. Twenty-six subsets comprised 3 or more sequences and were considered "confirmed." The remaining subsets comprised pairs of sequences and were considered "potential"; public database CLL sequences were found to be members of 9 of 22 "potential" subsets, thereby allowing us to consider them also "confirmed." The chance of belonging to a subset exceeded 35% for unmutated or selected IGHV genes (eg, IGHV1-69/3-21/4-39). Comparison to non-CLL public database sequences showed that HCDR3 restriction is "CLL-related." CLL cases with selected stereotyped immunoglobulins (IGs) were also found to share unique biologic and clinical features. In particular, cases expressing stereotyped IGHV4-39/IGKV1-39-1D-39 and IGHV4-34/IGKV2-30 were always IgG-switched. In addition, IGHV4-34/IGKV2-30 patients were younger and followed a strikingly indolent disease, contrasting other patients (eg, those expressing IGHV3-21/IGLV3-21) who experienced an aggressive disease, regardless of IGHV mutations. These findings suggest that a particular antigen-binding site can be critical in determining the clinical features and outcome for at least some CLL patients.

Ibrutinib, a once-daily oral inhibitor of Bruton's tyrosine kinase, is approved in the United States and Europe for treatment of patients with chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL). The phase 3 RESONATE study showed improved efficacy of single-agent ibrutinib over ofatumumab in patients with relapsed/refractory CLL/SLL, including those with high-risk features. Here we report the final analysis from RESONATE with median follow-up on study of 65.3 months (range, 0.3-71.6) in the ibrutinib arm. Median progression-free survival (PFS) remained significantly longer for patients randomized to ibrutinib vs ofatumumab (44.1 vs 8.1 months; hazard ratio [HR]: 0.148; 95% confidence interval [CI]: 0.113-0.196; P˂.001). The PFS benefit with ibrutinib vs ofatumumab was preserved in the genomic high-risk population with del(17p), TP53 mutation, del(11q), and/or unmutated IGHV status (median PFS 44.1 vs 8.0 months; HR: 0.110; 95% CI: 0.080-0.152), which represented 82% of patients. Overall response rate with ibrutinib was 91% (complete response/complete response with incomplete bone marrow recovery, 11%). Overall survival, censored for crossover, was better with ibrutinib than ofatumumab (HR: 0.639; 95% CI: 0.418-0.975). With up to 71 months (median 41 months) of ibrutinib therapy, the safety profile remained consistent with prior reports; cumulatively, all-grade (grade ≥3) hypertension and atrial fibrillation occurred in 21% (9%) and 12% (6%) of patients, respectively. Only 16% discontinued ibrutinib because of adverse events (AEs). These long-term results confirm the robust efficacy of ibrutinib in relapsed/refractory CLL/SLL irrespective of high-risk clinical or genomic features, with no unexpected AEs. This trial is registered at www.clinicaltrials.gov (NCT01578707).

RESONATE-2 is a phase 3 study of first-line ibrutinib versus chlorambucil in chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL). Patients aged ≥65 years (n = 269) were randomized 1:1 to once-daily ibrutinib 420 mg continuously or chlorambucil 0.5-0.8 mg/kg for ≤12 cycles. With a median (range) follow-up of 60 months (0.1-66), progression-free survival (PFS) and overall survival (OS) benefits for ibrutinib versus chlorambucil were sustained (PFS estimates at 5 years: 70% vs 12%; HR [95% CI]: 0.146 [0.098-0.218]; OS estimates at 5 years: 83% vs 68%; HR [95% CI]: 0.450 [0.266-0.761]). Ibrutinib benefit was also consistent in patients with high prognostic risk (TP53 mutation, 11q deletion, and/or unmutated IGHV) (PFS: HR [95% CI]: 0.083 [0.047-0.145]; OS: HR [95% CI]: 0.366 [0.181-0.736]). Investigator-assessed overall response rate was 92% with ibrutinib (complete response, 30%; 11% at primary analysis). Common grade ≥3 adverse events (AEs) included neutropenia (13%), pneumonia (12%), hypertension (8%), anemia (7%), and hyponatremia (6%); occurrence of most events as well as discontinuations due to AEs decreased over time. Fifty-eight percent of patients continue to receive ibrutinib. Single-agent ibrutinib demonstrated sustained PFS and OS benefit versus chlorambucil and increased depth of response over time.