The strategy of simultaneously inhibiting proliferation and reactivating apoptosis can eradicate chronic lymphocytic leukemia (CLL) in a large share of patients, suggest results from the phase 2 CLARITY trial.
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“Both ibrutinib and venetoclax are active in CLL with improved survival; however, as monotherapies, both currently are given until disease progression,” wrote Peter Hillmen, MBChB, PhD, St. James’s University Hospital, Leeds, England, and his colleagues.
In the single-arm, open-label trial, the investigators treated 53 patients with relapsed or refractory CLL with combination ibrutinib (Imbruvica), a small-molecule inhibitor of Bruton’s tyrosine kinase, and venetoclax (Venclexta), a small molecule inhibitor of the anti-apoptotic protein Bcl-2. The primary endpoint was MRD negativity, defined as presence of fewer than one CLL cell in 10,000 leukocytes, after 12 months of combination therapy.
Results reported in the Journal of Clinical Oncology showed that the combination was highly active, with 53% of patients achieving MRD negativity in the blood and 36% achieving MRD negativity in the marrow.
Most patients, 89%, had a treatment response, and slightly more than half, 51%, achieved a complete remission. With a median 21.1-month follow-up, only a single patient experienced progression and all were still alive.
Adverse effects were generally manageable. Grade 3-4 adverse events of special interest included 34 cases of neutropenia and 1 case of biochemical tumor lysis syndrome that was managed by delaying venetoclax.
“We have demonstrated promising efficacy that indicates potent synergy between ibrutinib and venetoclax for inducing MRD-negative responses with manageable adverse effects,” the investigators wrote. “The observation that a significant proportion of patients experience MRD-negative remission indicates that this combination can be given for a limited period and then stopped after patients achieve a deep remission.”
Whether the combination leads to permanent disease eradication in certain patients is still unclear, the investigators added.
The trial was supported by Bloodwise under the Trials Acceleration Programme, by the National Institute for Health Research Leeds Clinical Research Facility, and by an unrestricted educational grant from Janssen-Cilag and AbbVie. Ibrutinib was provided free of charge by Janssen-Cilag, and venetoclax was provided free of charge by AbbVie. Dr. Hillman reported financial relationships with Janssen, AbbVie, Roche, Pharmacyclics, and Gilead Sciences.
SOURCE: Hillmen P et al. J Clin Oncol. 2019 Jul 11. doi: 10.1200/JCO.19.00894.