CHICAGO – A fixed-duration venetoclax-obinutuzumab regimen is safe and provides a superior outcome versus standard chlorambucil-obinutuzumab in elderly patients with untreated chronic lymphocytic leukemia (CLL) and comorbidities, results of a randomized phase 3 trial showed.
At 24 months, progression-free survival was 88.2% for the venetoclax-obinutuzumab regimen, versus 64.1% for chlorambucil-obinutuzumab (hazard ratio, 0.35; 95% confidence interval, 0.23-0.53; P less than .0001) in CLL-14, an open-label, multinational trial presented at the annual meeting of the American Society of Clinical Oncology.
The regimen, given for just 12 28-day cycles, also achieved the highest rate of minimal residual disease (MRD)-negative responses ever seen in a randomized prospective CLL study, according to investigator Kirsten Fischer, MD, of the University of Cologne in Germany.
“We really think that these unprecedented MRD negativity levels will eventually translate into an improved overall survival,” Dr. Fischer said during an oral abstract presentation.
Matthew Steven Davids, MD, of Dana-Farber Cancer Institute/Harvard Medical School, Boston, said venetoclax plus obinutuzumab offers the potential for 1-year, time-limited therapy, which limits concerns over long-term adherence and has the potential for cost savings, should the therapy prove to be highly durable with further follow-up.
“A limitation of the study is that the comparator arm – chlorambucil plus obinutuzumab – is directly applicable to only a relatively small subset of our older and frailer CLL patients,” Dr. Davids said during a podium discussion of the results.
“But nonetheless, venetoclax plus obinutuzumab is a promising, time-limited regimen, and CLL14 is an immediately practice-changing study for frontline CLL treatment,” he added.
The regimen stands in contrast to ibrutinib, which offers durable responses but requires continuous dosing, and FCR (fludarabine, cyclophosphamide, and rituximab), a time-limited therapy with curative potential that is restricted to younger patients with IGHV-mutated CLL, according to Dr. Davids.
In CLL-14, 432 patients were randomized 1:1 to receive venetoclax-obinutuzumab for six cycles followed by venetoclax for six cycles, or chlorambucil-obinutuzumab for six cycles followed by chlorambucil for six cycles. The median age was 72 years in the venetoclax-obinutuzumab arm and 71 years in the chlorambucil-obinutuzumab arm.
The overall response rate was 85% for venetoclax-obinutuzumab and 71% for chlorambucil-obinutuzumab (P = .0007), Dr. Fischer reported at the meeting.
The improvement in progression-free survival seen in the overall study population was also seen in patients with TP53 deletions or mutations, and in those with unmutated IGHV, Dr. Fischer reported.
Rates of MRD negativity in peripheral blood were 76% versus 35% for the venetoclax- and chlorambucil-containing combinations, respectively (P less than .001), and similarly, MRD negativity in bone marrow was 57% versus 17% (P less than .001), she said.
There were no significant differences in the rates of grade 3 or 4 neutropenia, which occurred in 52.8% of the venetoclax–obinutuzumab treated patients and 48.1% of the chlorambucil-obinutuzumab treated patients, or in grade 3 or 4 infections, which occurred in 17.5% and 15.0%, respectively, according to a report, published simultaneously in the New England Journal of Medicine (2019;380:2225-36).
Likewise, all-cause mortality was not significantly different between the arms, at 9.3% and 7.9%, respectively.
F. Hoffmann-La Roche and AbbVie supported the study. Dr. Fischer reported travel, accommodations, or expenses from Roche in her abstract disclosure.
SOURCE: Fischer K et al. ASCO 2019, Abstract 7502.
