Chronic lymphocytic leukemia (CLL) is a clinically heterogeneous disease associated with several known genetic abnormalities, including 17p deletion (del[17p]), 11q deletion (del[11q]), and TP53 gene mutations, which are adverse prognostic markers among patients treated with chemoimmunotherapy.
The Bruton tyrosine kinase (BTK) inhibitor ibrutinib is approved for patients with untreated, relapsed, or refractory disease, including those with del(17p). Clinicians will soon have the chance to pair it with ublituximab, a next-generation, glycoengineered, type I, anti-CD20 monoclonal antibody that binds to a unique epitope on CD20, differentiating it from rituximab, ofatumumab, and obinutuzumab. Results from the phase 3 GENUINE trial, which were recently published in The Lancet Haematology, showed that ublituximab plus ibrutinib was superior to ibrutinib alone for patients with relapsed or refractory high-risk CLL.
This news organization spoke with Jennifer R. Brown, MD, PhD, director of the CLL Center and institute physician at the Dana-Farber Cancer Institute and professor of medicine at Harvard Medical School, both in Boston, about the GENUINE trial and its potential impact on treatment choices going forward.
What type of patients were treated in the GENUINE trial?
Dr. Brown: This is a trial among relapsed/refractory CLL patients with 17p or 11q deletion or TP53 mutation. Patients aged 18 years or older with CLL who warranted treatment, as defined by International Workshop on CLL criteria, were eligible if they had previously received at least two cycles of at least one standard treatment regimen, had an Eastern Cooperative Oncology Group performance status of 2 or lower, and had high-risk cytogenetics, defined as the presence of at least one of del(17p), del(11q), or TP53 mutation confirmed by a central laboratory with fluorescence in situ hybridization and/or next-generation sequencing.
What were the main outcomes of the trial?
Originally, the GENUINE trial had coprimary endpoints of progression-free survival (PFS) and overall response rate. Because of slow accrual, it was amended to have one primary endpoint of independent review committee (IRC)–assessed ORR.
IRC-assessed ORR was improved from 65% to 83% with the addition of ublituximab. PFS also improved significantly in the ublituximab group, with an even greater improvement when the analysis was limited to those with del(17p) or TP53 aberrancy, but this outcome was limited by the reduced sample size of the study as well as the relatively short PFS of the ibrutinib arm.
After a median follow-up of 41.6 months, the median IRC-assessed PFS in all treated patients was not reached in the ublituximab plus ibrutinib group after 15 PFS events but was 35.9 months in the ibrutinib group after 25 PFS events (hazard ratio, 0.46; 95% confidence interval, 0.24-0.87; P = .016).
Undetectable minimal residual disease was also seen in 42% of the combination arm, compared with 6% of the ibrutinib arm.
What types of adverse events were found in the trial?
The researchers found mostly mild and known side effects of ibrutinib. More atrial fibrillation and neutropenia were seen in the antibody group, but this was not marked.
Most adverse events were of grade 1 or 2. The most common grade 3 and 4 adverse events were neutropenia (11 [19%] patients in the ublituximab plus ibrutinib group and 7 [12%] in the ibrutinib group), anemia (5 [8%] and 5 [9%], respectively), and diarrhea (6 [10%] and 3 [5%], respectively).
What about serious adverse events?
Hospitalization from infection was seen, as expected. There were two cardiac arrests and an unexplained death, across both arms, which was concerning, given the known association of ibrutinib with ventricular arrhythmia and sudden death. There were also several hemorrhages, including one fatal one, which was again consistent with the known side effects of ibrutinib.
Are there treatments comparable with ublituximab plus ibrutinib that clinicians should perhaps first consider using?
In terms of other anti-CD20 antibodies, we have two randomized trials that have failed to show a benefit from adding rituximab to ibrutinib.
Obinutuzumab, like ublituximab, is also a next-generation glycoengineered antibody, and it is reasonably likely that it might lead to similar results. However, the only data we have on ibrutinib with obinutuzumab are from a single arm in a more heterogeneous, lower-risk patient population, and it is unlikely that a randomized comparison will ever be done.
On the basis of these trial results, how would you use the combination of ublituximab and ibrutinib for your patients?
I would consider the addition of ublituximab to a BTK inhibitor in high-risk patients (once ublituximab is approved). I already usually use a next-generation BTK inhibitor rather than ibrutinib.
Are there any other implications of the GENUINE trial?
I think this trial underscores the importance of studying genetic subgroups of patients separately. In this case, that was done in high-risk patients, but this observation likely also applies to low-risk patients.
Most trials to date have enrolled unselected patient populations, often without stratification, and their results therefore tend to obscure the outcomes in both the very high risk (as studied here) and in the low risk (patients with immunoglobulin heavy chain variable region gene mutations).
Dr. Brown has served as a consultant for AbbVie, Acerta/AstraZeneca, Beigene, Bristol-Myers Squibb/Juno/Celgene, Catapult, Genentech/Roche, Janssen, MEI Pharma, Morphosys, and Novartis, and has received research funding from Gilead, Loxo/Lilly, TG Therapeutics, Verastem/SecuraBio.
A version of this article first appeared on Medscape.com.