Lugano, Switzerland– It’s in the BAG: For patients with treatment-naive or relapsed/refractory chronic lymphocytic leukemia, a regimen consisting of debulking with bendamustine (Treanda) followed sequentially by obinutuzumab (Gazyva) and venetoclax (Venclexta) was associated with a high overall response rate and a large majority of patients being negative for minimal residual disease (MRD) in peripheral blood.
In the open-label, phase II CLL2-BAG study in 66 patients, the overall response rate at the end of induction was 95%, and 87% of patients were negative for MRD, reported Paula Cramer, MD, of the University of Cologne (Germany).
“This sequential treatment of bendamustine followed by obinutuzumab and venetoclax does not lead to any cumulative or unexpected toxicity. As compared to other trials, it’s important to point out that only one laboratory TLS [tumor lysis syndrome] occurred with venetoclax. Maybe that’s explained by the sequential start of all three drugs,” she said at the International Conference on Malignant Lymphoma.
The trial is based on a concept the investigators call “sequential triple-T” (tailored and targeted treatment) aimed at complete eradication of MRD.
The 66 patients (median age, 59 years) had either previously untreated or relapsed/refractory CLL; 34 of the treatment-naive and 29 of the relapsed/refractory patients were evaluable for response.
At enrollment, patients who had an absolute lymphocyte count of 25,000/mcL or greater and/or lymph nodes 5 cm or larger received two cycles of debulking with bendamustine 70 mg/m2 on days 1 and 2 every 28 days, unless this was contraindicated.
The induction phase consisted of obinutuzumab 1,000 mg administered three times in cycle 1, then every 4 weeks for cycles 2 through 6. Venetoclax was started during cycle 2 with a dose escalation to 400 mg daily over a period of 5 weeks.
Maintenance therapy consisted of daily venetoclax and obinutuzumab every 3 months until MRD negativity or up to 24 months.
A total of 45 patients (31 who were treatment naive and 14 with relapsed/refractory disease) underwent debulking. Of this group 36 patients received both cycles, and 9 discontinued early because of either adverse events (5 patients), disease progression (1), or unknown reasons (3).
Sixty of the 66 patients received the full six induction cycles. Three patients who had fewer than two cycles were excluded according to protocol. Of these three, two heavily pretreated patients died of sepsis and one of myocardial infarction in cycle 1.
Responses
In all, 24 patients (53%) who had debulking had a response during that phase based on International Workshop on CLL (IWCLL) criteria, for an overall response rate (ORR) of 53%. Thirteen patients had stable disease after debulking, and four had disease progression.
Responses after induction according to IWCLL criteria, the primary endpoint, included five patients with a complete response (three treatment-naive and two relapsed/refractory patients), and 20 patients (14 treatment-naive and six relapsed/refractory patients) with an unconfirmed or clinical complete response or a complete response with incomplete recovery of counts.
In addition, 35 patients (17 who were treatment naive and 18 with relapsed/refractory disease) had a partial response. No patients had stable disease, and three patients, all with relapsed/refractory disease, had disease progression.
Of the 63 patients who had at least two cycles of therapy, 87% were MRD negative. Eight patients had MRD assessments by bone marrow, and all eight were MRD negative.
The maintenance phase of the trial is ongoing and the data are not mature, but 56 patients (30 who were treatment naive and 26 with relapsed/refractory disease) have started on maintenance therapy. Of this group, 28 have stopped maintenance, including 21 patients who stopped because they achieved MRD negativity, 5 who discontinued because of adverse events, and 2 with disease progression or Richter’s transformation.
At 15 months of follow-up, progression-free survival was 100% in patients who received the combination as the frontline therapy, and 83% in the patients with relapsed/refractory disease.
Adverse events
In the debulking phase, 34 patients (72%) experienced adverse events of any grade, including 16 patients with grade 3 or 4 events
Adverse events associated with debulking included neutropenia and anemia, each seen in five patients, thrombocytopenia and infection each seen in three patients, and coronary artery disorders, rash, tumor lysis syndrome, vomiting, and pyrexia in one patient each.
Sixty of the 66 patients received the full six induction cycles. Three patients who had fewer than two cycles were excluded according to protocol. Of these three, two heavily pretreated patients died of sepsis and one of myocardial infarction in cycle 1.
All but 3 of the 63 patients had an adverse event, and 44 patients had at least one grade 3 or 4 adverse event.
Cytopenias, infections, infusion-related reactions, and neoplasms were the most common adverse events.
There were three grade 3 laboratory-confirmed cases of tumor lysis syndrome, one each occurring during bendamustine debulking, obinutuzumab administration, and venetoclax administration.
Something other than venetoclax?
Davide Rossi, MD, PhD, of the Oncology Institute of Southern Switzerland in Bellinzona, the invited discussant, questioned whether venetoclax is the best agent to use in sequential triple-T therapy.
“We know that venetoclax is more active in blood and bone marrow than in lymph nodes and, indeed, a proportion of cases achieving all the criteria for a CR [complete response] in the bone marrow and the peripheral blood, including MRD negativity, may still have some residual [disease in] lymph nodes,” he said.
Drugs that inhibit the B-cell receptor pathway may be more effective at eradicating MRD in the lymph node compartment, Dr. Cramer said.
The study was sponsored by the German CLL study group. Dr. Cramer disclosed financial ties to multiple entities. Dr. Rossi did not report disclosures.