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Poster session at ASCO 2018
©ASCO/Scott Morgan 2018

CHICAGO—Minimal residual disease (MRD) kinetics confirms the high, durable MRD-negativity with venetoclax plus rituximab in relapsed/refractory chronic lymphocytic leukemia (CLL), according to a further examination of the phase 3 MURANO study.

Undetectable MRD-negativity is associated with extended progression-free survival (PFS) and overall survival in patients receiving chemoimmunotherapy for CLL.

“Attainment of MRD-negativity in relapsed/refractory CLL is also a desired trial endpoint due to the subjectivity of complete response definition regarding pathologic lymph node size,” said Peter Hillmen, MD, of St James’s University Hospital, Leeds, United Kingdom, at the 2018 ASCO Annual Meeting.

Dr Hillmen reported new data on MRD response in cytogenetic and molecular risk groups, MRD sustainability and kinetics, and MRD conversion in the MURANO trial (abstract 7508).

MURANO trial (NCT02005471)

In the trial, venetoclax-rituximab showed superior PFS and peripheral blood and bone marrow MRD-negativity as compared to bendamustine plus rituximab (BR) in relapsed/refractory CLL patients.

Patients were randomized to venetoclax-rituximab for 6 months, followed by single-agent venetoclax for up to 1.5 years, or BR for 6 months. Peripheral blood samples were serially collected and bone marrow was collected at the end of combination treatment or at best response.

MRD findings

The new results show higher concordance in MRD-negativity between bone marrow and peripheral blood in venetoclax-rituximab (45 of 50 patients, 90%) vs BR (3 of 10 patients, 30%) in paired samples.

Focusing on peripheral blood MRD, Dr Hillmen said the best MRD-negativity rates were higher with venetoclax-rituximab (84%) than BR (23%). These results were independent of high-risk factors—such as del 17p, IGVH unmutated, and mutated TP53—only for venetoclax-rituximab treated patients.

“The superior peripheral blood MRD response with venetoclax-rituximab was consistent across subgroups at the end of completion of treatment,” Dr Hillmen said. “Most patients who achieved peripheral blood MRD-negativity on venetoclax-rituximab remained MRD-negative and were progression-free.”

Among 121 of 194 (62%) patients on venetoclax-rituximab who achieved MRD-negativity at the end of combination therapy, 100 (83%) patients maintained MRD-negativity and were progression-free at a median follow-up of 13.8 months. Two patients developed progressive disease and 2 patients died (unrelated to CLL).

Two patients developed Richter’s disease (with one MRD-positive directly before therapy) and 15 (12%) patients converted to confirmed MRD-positive at a median MRD-positive follow-up of 5.6 months.

“High peripheral blood MRD-negativity at the end of combination treatment and concordance with bone marrow MRD with venetoclax-rituximab,” Dr Hillmen said, “confirms the value of peripheral blood MRD for evaluation of treatment benefit in relapsed/refractory CLL patients. The high rate of peripheral blood MRD-negativity at end of combination treatment with venetoclax-rituximab was attained regardless of risk features.”

Some conversion to MRD-positivity occurred only in a small proportion of patients. Most cases were of intermediate level and remained progression-free, he said.

“MRD kinetics indicate that peripheral blood MRD-negativity with venetoclax-rituximab occurs early and is maintained over time with current follow-up,” Dr Hillmen added. The MRD data now provide a framework for designing response adaptive therapy.

The US Food and Drug Administration recently approved venetoclax-rituximab for CLL or small lymphocytic lymphoma for patients with or without del 17p.

Venetoclax is being developed by Genentech and Abbvie. 

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