AMSTERDAM – Patients with relapsed or refractory acute myeloid leukemia (AML) may be more likely to respond when selinexor is added to standard chemotherapy, according to investigators.
In a recent phase 2 trial, selinexor given with cytarabine and idarubicin led to a 50% overall response rate, reported lead author, of University Medical Center Hamburg-Eppendorf (Germany). This response rate is at the upper end of what has been seen in published studies, Dr. Fiedler said at the annual congress of the European Hematology Association.
He also noted that giving a flat dose of selinexor improved tolerability in the trial, a significant finding in light of common adverse events andfrom the Food and Drug Administration about the safety of selinexor for patients with multiple myeloma.
“The rationale to employ selinexor in this study is that there is a synergy between anthracyclines and selinexor,” Dr. Fiedler said, which may restore anthracycline sensitivity in relapsed or refractory patients. “Secondly, there is a c-myc reduction pathway that leads to a reduction of DNA damage repair genes such as Rad51 and Chk1, and this might result in inhibition of homologous recombination.”
The study involved 44 patients with relapsed or refractory AML, of whom 17 (39%) had previously received stem cell transplantation and 11 (25%) exhibited therapy-induced or secondary disease. The median patient age was 59.5 years.
Patients were given idarubicin 10 mg/m2 on days 1, 3, and 5, and cytarabine 100 mg/m2 on days 1-7. Initially, selinexor was given at a dose of 40 mg/m2 twice per week for 4 weeks, but this led to high rates of febrile neutropenia and grade 3 or higher diarrhea, along with prolonged aplasia. In response to this issue, after the first 27 patients, the dose was reduced to a flat amount of 60 mg, given twice weekly for 3 weeks.
For patients not undergoing transplantation after the first or second induction cycle, selinexor maintenance monotherapy was offered for up to 1 year.
The primary endpoint was overall remission rate, reported as complete remission, complete remission with incomplete blood count recovery, and morphological leukemia-free status. Secondary endpoints included the rate of partial remissions, percentage of patients being transplanted after induction, early death rate, overall survival, event-free survival, and relapse-free survival.
The efficacy analysis revealed an overall response rate of 50%. A total of 9 patients had complete remission (21.4%), 11 achieved complete remission with incomplete blood count recovery (26.2%), and 1 exhibited morphological leukemia-free status (2.4%). Of note, almost half of the patients (47%) who had relapsed after previous stem cell transplantation responded, as did three-quarters who tested positive for an NPM1 mutation. After a median follow-up of 8.2 months, the median overall survival was 8.2 months, relapse-free survival was 17.7 months, and event-free survival was 4.9 months.
Adverse events occurred frequently, with a majority of patients experiencing nausea (86%), diarrhea (83%), vomiting (74%), decreased appetite (71%), febrile neutropenia (67%), fatigue (64%), leukopenia (62%), thrombocytopenia (62%), or anemia (60%).
Grade 3 or higher adverse events were almost as common, and included febrile neutropenia (67%), leukopenia (62%), thrombocytopenia (62%), anemia (57%), and diarrhea (50%). Reducing the dose did improve tolerability, with notable drops in the rate of severe diarrhea (56% vs. 40%) and febrile neutropenia (85% vs. 33%). In total, 19% of patients discontinued treatment because of adverse events.
A total of 25 patients (60%) died during the study, with about half dying from disease progression (n = 12), and fewer succumbing to infectious complications, graft-versus-host disease, multiorgan failure, multiple brain infarct, or asystole. Two deaths, one from suspected hemophagocytosis and another from systemic inflammatory response syndrome, were considered possibly related to selinexor.
“The results should be further evaluated in a phase 3 study,” Dr. Fiedler said. However, plans for this are not yet underway, he said, adding that Karyopharm Therapeutics will be focusing its efforts on selinexor for myeloma first.
The study was funded by Karyopharm. Dr. Fielder reported financial relationships with Amgen, Pfizer, Jazz Pharmaceuticals, and other companies.
SOURCE: Fiedler W et al. EHA Congress, Abstract S880.