Acalabrutinib monotherapy can produce durable responses in relapsed/refractory mantle cell lymphoma (MCL), according to updated results from a phase 2 trial.
The drug produced an overall response rate (ORR) of 81%, and the median duration of response was 26 months.
These are the highest such figures reported “among all approved single-agent therapies for the treatment of relapsed/refractory MCL,”, of the MD Anderson Cancer Center at the University of Texas in Houston and colleagues wrote in a letter in .
Dr. Wang and colleagues reported updated results in 124 patients treated on the ACE-LY-004 trial. At baseline, the patients had a median age of 68 years (range, 42-90 years), and 80% were men. Three-quarters of patients had stage IV disease, 72% had extranodal disease, 21% had blastoid/pleomorphic MCL, and 26% had a Ki-67 proliferation index of 50% or greater.
At a median follow-up of 26 months, 40% (n = 49) of patients were still on acalabrutinib, and 61% (n = 76) were still in follow-up for survival. Six patients went on to allogeneic transplant at a median of 19 days after stopping acalabrutinib.
The ORR was 81% (100/124), and the complete response (CR) rate was 43% (n = 53). Four patients who initially had a partial response converted to a CR with longer follow-up. The estimated 24-month duration of response was 52.4%.
“ORR was consistent across patients with refractory disease and those with blastoid/pleomorphic MCL, despite those patients having a higher mean Ki-67 index [of 50% or greater], suggesting that some patients with poorer prognosis may also benefit from acalabrutinib,” Dr. Wang and colleagues wrote.
There were 29 patients evaluable for minimal residual disease (MRD) assessment. Seven patients (24%) had MRD-negative disease in the peripheral blood after they achieved a CR. An additional patient with a CR became MRD negative when a second blood sample was taken about 6 months after the first.
“Despite limited samples, these results demonstrate that continued use of acalabrutinib can lead to undetectable MRD in patients with CR,” Dr. Wang and his colleagues wrote. “Since most patients with MRD data are still on treatment (27/29), relationships between MRD negativity and durability of response cannot be made at this time.”
The median progression-free survival was 20 months, and the median overall survival was not reached. The estimated 24-month progression-free survival rate was 49.0%, and the estimated 24-month overall survival rate was 72.4%. Patients with low/intermediate Mantle Cell Lymphoma International Prognostic Index scores, classical MCL, and a Ki-67 index less than 50% had a longer duration of response and survival.
The adverse event profile was “largely consistent with earlier reporting,” Dr. Wang and colleagues wrote. The most frequent adverse events were headache (38%), diarrhea (36%), fatigue (28%), cough (22%), and myalgia (21%). The most common grade 3/4 adverse events were anemia (10%), neutropenia (10%), and pneumonia (6%).
Ten patients developed second primary cancers. There were no new atrial fibrillation events and no new hypertension events. The frequency of infections decreased over time, as did the number of bleeding events. However, two of three major hemorrhage events occurred after the previous report was published.
There were 43 deaths (35%), 29 of them because of disease progression. Six patients died of adverse events, two died of unknown causes, and two died of secondary acute myeloid leukemia. Other causes of death included multiorgan failure, intestinal obstruction, lung cancer, and graft-versus-host disease.
This study was sponsored by Acerta Pharma, a member of the AstraZeneca Group. The researchers reported relationships with AstraZeneca/Acerta Pharma and many other companies.
SOURCE: Wang M et al. Leukemia. 2019 Sep 26. .