John F. Seymour, MBBS, PhD
ATLANTA—The combination of venetoclax and rituximab (VR) should be a standard treatment option for adults with relapsed/refractory chronic lymphocytic leukemia (CLL), according to a speaker at the 2017 ASH Annual Meeting.
Data from the phase 3 MURANO study showed that patients with relapsed/refractory CLL who received VR had significantly longer progression-free survival (PFS) than those who received bendamustine and rituximab (BR).
In addition, “secondary endpoints were consistently in favor of venetoclax-rituximab,” said study investigator John F. Seymour, MBBS, PhD, of Peter MacCallum Cancer Centre in Melbourne, Victoria, Australia.
Adverse events (AEs) were largely consistent with the known safety profiles of the drugs studied, but tumor lysis syndrome (TLS) was infrequent and occurred at a similar frequency in both treatment arms.
“Thus, overall, I believe venetoclax and rituximab should be considered as a suitable standard therapeutic option in patients with relapsed/refractory CLL,” Dr Seymour said.
It is important to note, however, that patients in the VR arm of this study could receive venetoclax for up to 2 years, whereas patients in the BR arm received study treatment for a maximum of six 28-day cycles.
Dr Seymour presented results from MURANO as a late-breaking abstract at ASH (LBA-2). The study was sponsored by Hoffman-La Roche and AbbVie.
MURANO enrolled 389 CLL patients who had received 1 to 3 prior therapies. Patients were randomized to receive VR (n=194) or BR (n=195). Baseline characteristics were similar between the treatment arms.
In both arms, patients received a single monthly dose of rituximab for 6 cycles. The first dose was 375 mg/m2, and all subsequent doses were 500 mg/m2.
In the VR arm, patients received a 4-week or 5-week dose ramp-up of venetoclax from 20 mg to 400 mg daily. This was intended to mitigate the risk of TLS, which has been observed in previous studies of venetoclax.
Patients in the VR arm continued with daily venetoclax at 400 mg for a maximum of 2 years or until disease progression or cessation due to toxicity. They started receiving rituximab after the ramp-up period (at week 6).
In the BR arm, patients received bendamustine at 70 mg/m2 on days 1 and 2 of each 28-day cycle for 6 cycles. Patients could proceed to subsequent therapy if they progressed.
The median follow-up was 23.8 months (range, 0-37.4 months).
Twenty-five percent of patients in the VR arm and 17% in the BR arm discontinued treatment ahead of schedule. Reasons for discontinuation (in the VR and BR arms, respectively) were disease progression (5% and 3%), AEs (12% and 6%), death (1% and 2%), and “other” (6% and 7%).
Survival
The study’s primary endpoint was investigator-assessed PFS. PFS according to an independent review committee (IRC) was a secondary endpoint.
According to investigators, the median PFS was not reached in the VR arm and was 17.0 months in the BR arm (hazard ratio [HR]=0.17, P<0.0001). According to the IRC, the median PFS was not reached in the VR arm and was 18.1 months in the BR arm (HR=0.17, P<0.0001).
According to investigators, the estimated PFS at 24 months was 84.9% in the VR arm and 36.3% in the BR arm. According to the IRC, the 24-month PFS was 82.8% and 37.4%, respectively.
The benefit with VR was consistent across subgroups. Patients had a PFS benefit regardless of their number of prior therapies, deletion 17p status, TP53 mutational status, baseline IGHV mutational status, and whether they had relapsed or refractory disease.
Dr Seymour acknowledged that the differences in treatment duration between the BR and VR arms may have affected the interpretation of these results.
“[T]he treatment duration differed, although, of course, the capacity to deliver more than 6 cycles of bendamustine-rituximab would have been problematic,” he said. “There is some data that antibody treatment may prolong progression-free survival. However, when this study was designed, in 2013, that data was certainly not available. And I believe, currently, maintenance antibody is not an accepted standard of treatment.”
The median overall survival (OS) was not reached in either treatment arm. The 1-year OS rate was 95.9% in the VR arm and 91.1% in the BR arm. The 2-year OS rate was 91.9% and 86.6%, respectively (HR=0.48, P=0.0186).
“[W]ith median follow-up of just on 2 years, there is already a clinically meaningful difference [in OS between the treatment arms],” Dr Seymour said.
“This is not attributable to any difference in availability of novel therapies. Of the 54 patients who received subsequent therapy after progression on the bendamustine-rituximab arm, 40 of those received novel targeted agents.”
Response and MRD
According to investigators, the overall response rate was 93.3% (181/194) in the VR arm and 67.7% (312/195) in the BR arm (P<0.0001). According to the IRC, the overall response rate was 92.3% (179/194) and 72.3% (141/195), respectively (P<0.0001).
According to investigators, the rate of complete response (CR) or CR with incomplete marrow recovery (CRi) was 26.8% (n=52) in the VR arm and 8.2% (n=16) in the BR arm. According to the IRC, the CR/CRi rate was 8.2% (n=16) and 3.6% (n=7), respectively.
Dr Seymour acknowledged the differences in CR/CRi between investigator and IRC assessments. He said 28 of the 42 discrepancies in the VR arm “were attributable to residual CT scan nodal abnormalities in the 16- to 30-mm size.” However, he also noted that 88% of these patients were negative for minimal residual disease (MRD) in the peripheral blood at that time point.
MRD was assessed every 3 months. Patients were counted as MRD-positive if they were positive by either allele-specific oligonucleotide polymerase chain reaction or multicolor flow cytometry. Patients were also counted as MRD-positive if there was a failure to collect a sample.
The proportion of patients who were MRD-negative in the VR and BR arms, respectively, was:
- 45% and 6% at 4 months
- 62% and 13% at 9 months
- 60% and 10% at 12 months
- 57% and 9% at 15 months
- 60% and 5% at 18 months.
Dr Seymour pointed out that 65 patients in the VR arm surpassed the maximum treatment duration for venetoclax (2 years) and therefore stopped receiving the drug, but only 12 of these patients have follow-up beyond 3 months.
“So information about the durability of response after cessation remains immature at the moment,” he said.
Safety
All patients in the VR arm and 98% in the BR arm had at least 1 AE. The rate of serious AEs was 46% and 43%, respectively. The rate of grade 3/4 AEs was 82% and 70%, respectively.
Grade 3/4 AEs with at least a 2% difference in incidence between the treatment arms (in the VR and BR arms, respectively) were neutropenia (58% and 39%), anemia (11% and 14%), thrombocytopenia (6% and 10%), febrile neutropenia (4% and 10%), pneumonia (5% and 8%), infusion-related reactions (2% and 5%), TLS (3% and 1%), hypotension (0% and 3%), hyperglycemia (2% and 0%), and hypogammaglobulinemia (2% and 0%).
The rate of grade 5 AEs was 5% in the VR arm and 6% in the BR arm.
Grade 5 AEs in the VR arm were pneumonia (n=3), sepsis (n=1), cardiac failure (n=1), myocardial infarction (n=1), sudden cardiac death (n=1), colorectal cancer (n=1), status epilepticus (n=1), and acute respiratory failure (n=1).
Grade 5 AEs in the BR arm included sepsis (n=2), lung cancer (n=2), Listeria sepsis (n=1), Scedosporium infection (n=1), lymphoma (n=1), hemorrhagic stroke (n=1), pulmonary embolism (n=1), acute myeloid leukemia (n=1), and sudden death (n=1).
