In patients with previously untreated chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL), a once-daily oral regimen of ibrutinib and venetoclax was associated with deep molecular remissions in both bone marrow and peripheral blood, including in patients with high-risk disease, according to investigators in the phase 2 CAPTIVATE MRD trial.
An intention-to-treat analysis of 164 patients with CLL/SLL treated with the combination of ibrutinib (Imbruvica) and venetoclax (Venclexta) showed a 75% rate of minimal residual disease (MRD) negativity in peripheral blood, and a 68% rate of MRD negativity in bone marrow among patients who received up to 12 cycles of the combination, reported Tanya Siddiqi, MD, of City of Hope National Medical Center, Duarte, Calif., and colleagues.
“This phase 2 study supports synergistic antitumor activity of the combination with notable deep responses across multiple compartments,” she said in an oral presentation during the virtual annual congress of the European Hematology Association.
Not ready to change practice
A hematologist/oncologist who was not involved in the study said that the data from CAPTIVATE MRD look good, but it’s still not known whether concurrent or sequential administration of the agents is optimal, and whether other regimens may be more effective in the first line.
“I think this is promising, but the informative and practice-changing study would be to compare this combination to ibrutinib monotherapy or to venetoclax and obinutuzumab, and that’s actually the subject of the next large German cooperative group study, CLL17,” said Catherine C. Coombs, MD, assistant professor of medicine at the University of North Carolina, and the UNC Lineberger Cancer Center, Chapel Hill.
She noted that the combination of venetoclax and obinutuzumab (Gazyva) is also associated with high rates of MRD negativity in the first-line setting, and that use of this regimen allows clinicians to reserve ibrutinib or acalabrutinib (Calquence) for patients in the relapsed setting.
Prerandomization results
Dr. Siddiqi presented prerandomization results from the MRD cohort of the CAPTIVATE trial (NCT02910583), which is evaluating the combination of ibrutinib and venetoclax for depth of MRD response. Following 12 cycles of the combinations, patients in this cohort are then randomized based on confirmed MRD status, with patients who are MRD negative randomized to maintenance with either ibrutinib or placebo, and patients with residual disease (MRD positive) randomized to maintenance with either ibrutinib alone or with venetoclax.
A total of 164 patients with previously untreated CLL/SLL and active disease requiring treatment who were under age 70 and had good performance status were enrolled. Following an ibrutinib lead-in period with the drug given at 420 mg once daily for three cycles of 28 days, the patients were continued on ibrutinib, and were started on venetoclax with a ramp up to 400 mg once daily, for 12 additional cycles.
As planned, patients were assessed after 15 cycles for tumor lysis syndrome (TLS) risk assessment, MRD, and hematologic, clinical, imaging, and bone marrow exams for response.
The median patient age was 58, with poor-risk features such as deletion 17p seen in 16%, complex karyotype in 19%, and unmutated immunoglobulin heavy chain variable (IGHV) in 59%.
A total of 152 patients (90%) completed all 12 cycles of the combined agents, with a median treatment duration of 14.7 months on ibrutinib and 12 months on venetoclax. Eight patients had adverse events leading to discontinuation, but there were no treatment-related deaths.
A majority of patients had reductions in lymph node burden after the three-cycle ibrutinib lead in. TLS risk also decreased during the lead-in period, with 90% of patients who had a high baseline TLS risk shifting to medium or low-risk categories, and no patients moved into the high-risk category.
“Hospitalization because of this was no longer required in 66% of at-risk patients after three cycles of ibrutinib lead in, and 82% of patients initiated venetoclax ramp up without the need for hospitalization,” Dr. Siddiqi said.
The best response of undetectable MRD was seen in peripheral blood of 75% of 163 evaluable patients, and in bone marrow of 72% of 155 patients. As noted before, the respective rates of MRD negativity in the intention-to-treat population were 75% and 68%. The proportion of patients with undetectable MRD in peripheral blood increased over time, from 57% after six cycles of the combination, she said.
The overall response rate was 97%, including 51% complete responses (CR) or CR with incomplete bone marrow recovery (CRi), and 46% partial (PR) or nodular PR (nPR). Among patients with CR/CRi, 85% had undetectable MRD in peripheral blood and 80% were MRD negative in bone marrow. In patients with PR/nPR, the respective rates were 69% and 59%. The high rates of undetectable MRD were seen irrespective of baseline disease characteristics, including bulky disease, cytogenetic risk category, del(17p) or TP53 mutation, and complex karyotype.
The most common adverse events with the combination were grade 1 or 2 diarrhea, arthralgia, fatigue, headache, and nausea. Grade 3 neutropenia was seen in 17% of patients, and grade 4 neutropenia was seen in 16%. Grade 3 febrile neutropenia and laboratory confirmed TLS occurred in 2 patients each (1%), and there were no grade 4 instances of either adverse event.
Postrandomization follow-up and analyses are currently being conducted, and results will be reported at a future meeting, real or virtual. An analysis of data on a separate cohort of 159 patients treated with the ibrutinib-venetoclax combination for a fixed duration is currently ongoing.
Dr. Siddiqi disclosed research funding and speakers bureau activity for Pharmacyclics, which sponsored the study, and others, as well as consulting/advising for several companies. Dr. Coombs disclosed consulting for AbbVie.
SOURCE: Siddiqi T et al. EHA25. Abstract S158.