EDINBURGH – Consolidation therapy with obinutuzumab after chemoimmunotherapy for B-cell chronic lymphocytic leukemia (B-CLL) was highly effective for eradicating minimal residual disease (MRD) within 6 months following randomization in the seamless phase 2/3 GALACTIC trial.
Of 14 patients who were MRD positive after chemoimmunotherapy and randomized to consolidation with the type II monoclonal antibody targeting the CD20 antigen, 10 achieved MRD negativity in the bone marrow by 6 months, and 13 achieved MRD negativity in the peripheral blood by 6 months,, reported at the International Workshop on Chronic Lymphocytic Leukemia.
“And that translated into [progression-free survival] improvement in the consolidation arm,” said Dr. Munir of St. James’s University, Leeds, England.
The median progression-free survival in that arm was not reached, whereas progression-free survival in 15 MRD-positive patients randomized to the nonconsolidation arm was 16.6 months, he said.
Further, no difference was seen in median progression-free survival, overall survival, or MRD duration between the consolidation arm and 19 patients who were not randomized because of MRD negativity after chemoimmunotherapy, he noted.
Achieving MRD negativity in CLL confers a survival advantage, and obinutuzumab has shown greater efficacy with respect to MRD in CLL when compared with previous anti-CD20 antibodies, and it is less immune suppressive than the anti-CD52 antibody alemtuzumab, he explained.
The GALACTIC trial was designed to assess the safety and efficacy of obinutuzumab consolidation for eradicating MRD and whether its effects would prolong progression-free survival in patients with B-CLL who recently responded to chemoimmunotherapy. Those achieving complete response or partial response at 3-24 months after chemoimmunotherapy, and who remained MRD-positive, were eligible for randomization.
The planned sample size was 188 patients, but the trial was closed early in February 2017 because of poor recruitment; a total of 48 patients were enrolled, including the 19 nonrandomized, MRD-negative patients.
Patients randomized to consolidation received 1,000 mg of obinutuzumab weekly for the first four doses, and then every other week for four additional doses.
Obinutuzumab was well tolerated with minimal infusion-related reactions and toxicity, Dr. Munir said.
Despite the low recruitment, both the phase 2 and 3 endpoints were assessed as positive, because the consolidation strategy was so efficacious, Dr. Munir noted, concluding that the findings provide further evidence of the value of MRD negativity for improving outcomes in CLL.
The GALACTIC trial was developed by the GALACTIC Trial Management Group with the support of the UKCLL/NCRI CLL Clinical Trials Subgroup. The trial is funded by Cancer Research UK and Roche and sponsored by the University of Leeds. Dr. Munir reported having no disclosures.