SAN DIEGO — Median progression-free survival (PFS) improved by about 10 months in patients with relapsed/refractory mantle cell lymphoma (MCL) who were treated with both ibrutinib (Imbruvica) and venetoclax (Venclexta) vs. ibrutinib alone, an interim analysis of a new study finds. However, there was a statistically significant difference in overall survival between the groups.
Still, "in the countries where ibrutinib is indicated, this combination should be a new standard therapy for relapsed/refractory mantle cell lymphoma," Michael Wang, MD, of the University of Texas MD Anderson Cancer Center, Houston, said in a media briefing at the annual meeting of the American Society of Hematology.
Its use would be off label, according to the authors of the industry-funded trial, because no nation has approved the combination therapy for MCL, a rare, aggressive form of non-Hodgkin lymphoma.
As Dr. Wang noted, ibrutinib (a Bruton tyrosine kinase inhibitor) is approved by the Food and Drug Administration to treat MCL, while venetoclax (a BCL-2 inhibitor) is approved for chronic lymphocytic leukemia and previously untreated acute myeloid leukemia. "The combination of these two agents leverages complementary modes of action and has demonstrated synergistic anti-tumor activity in preclinical models of mantle cell lymphoma," he said. And "in patients with relapsed/refractory mantle cell lymphoma, promising clinical activity has also been observed in early-phase studies."
For the multinational, randomized, phase 3, double-blind SYMPATICO study, researchers assigned 267 adults with relapsed/refractory MCL after 1-5 prior therapies 1:1 to receive oral ibrutinib 560 mg daily with oral venetoclax (standard 5-wk ramp-up to a target dose of 400 mg once daily) or placebo for 2 years. Then they continued with ibrutinib alone until progressive disease or unacceptable toxicity.
The study began in 2017. The median age of patients was 68, and the numbers of patients in each group were 134 (both drugs) and 133 (ibrutinib plus placebo).
At a median of 51.2 months, median PFS — the primary endpoint — was higher in the combination group vs. ibrutinib alone (31.9 vs. 22.1 months, hazard ratio [HR] = 0.65, 95% CI, 0.47–0.88, P = .0052). While overall survival was higher in the combination group vs. ibrutinib alone, an interim analysis found that the difference was not statistically significant (44.9 months vs. 38.6 months, 95% CI, HR = 0.85, 0.62-1.19, P = .3465).
When questioned about this finding at the ASH news briefing, Dr. Wang said that 170 events are needed for a full overall survival analysis, and there are just 144 now. The study may reach that point in early 2025, he said.
Over a median treatment duration of 22.0 months for the combination treatment and 17.7 months for ibrutinib alone, grade ≥ 3 adverse events occurred in 84% and 76% of patients, respectively. At 60%, the level of serious adverse events was the same in both groups.
In an interview, Brian T. Hill, MD, PhD, of Cleveland Clinic, noted that in general, MCL "has a pretty relentless pattern of relapses and disease progression without an easy cure in the vast majority of patients."
Ibrutinib has revolutionized treatment over the past decade with generally manageable side effects, and clinicians are now turning to other Bruton tyrosine kinase inhibitors, he said. Still, "there is a need for improving the durability and the response rates second-line treatment or beyond," Dr. Hill said.
The new study is important since it's the first randomized trial "that demonstrates that additional venetoclax significantly improves not only response rates, but also progression-free survival with a trend toward overall survival," he said. "The toxicity profile doesn't really seem to be significantly more worse than what we might expect with each agent given individually."
However, Dr. Hill noted that "it's a relatively small study and relatively short follow-up."
It may be difficult to get an ibrutinib-venetoclax combination approved today since ibrutinib is no longer the preferred Bruton tyrosine kinase inhibitor for clinicians, he said.
Pharmacyclics, maker of ibrutinib, is the study sponsor and Janssen is a collaborator.
Dr. Wang reports research funding Acerta Pharma, AstraZeneca, BeiGene, BioInvent, Celgene, Genentech, Innocare, Janssen, Juno Therapeutics, Kite Pharma, Lilly, Loxo Oncology, Molecular Templates, Oncternal, Pharmacyclics, and VelosBio. Other authors report multiple and various relationships with industry. Dr. Hill discloses research funding and consulting relationships with Pharmacyclics, AbbVie, BeiGene, and AstraZeneca.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.
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