Duvelisib is demonstrating encouraging activity and manageable toxicities among patients with relapsed/refractory peripheral T-cell lymphoma (PTCL) in a phase 2 trial, an investigator said.
The overall response rate in the dose-optimization phase of the PRIMO trial was more than 60% among patients receiving 75 mg of duvelisib twice daily, with a median duration of response exceeding 12 months, said investigator Barbara Pro, MD, of Northwestern University, Chicago.
In the ongoing dose-expansion phase, in which patients start on 75 mg twice daily and then transition to a lower dose, the ORR is over 50%, including complete responses (CRs) in about one-third of patients, Dr. Pro reported at the annual meeting of the American Society of Hematology.
Most previously approved treatments for relapsed/refractory PTCL are associated with ORRs of less than 30%, low rates of CR, and median progression-free survival of less than 4 months, Dr. Pro said in her presentation.
There have been no unexpected toxicities in the dose-expansion phase, and the adverse event profile is consistent with what has been observed previously for this oral phosphatidylinositol 3-kinase (PI3K) inhibitor, according to Dr. Pro.
Based on results to date, Dr. Pro said she and coinvestigators are hopeful that duvelisib will have a place in the treatment armamentarium for relapsed/refractory PTCL in the future.
“This is one of the most effective agents in T-cell lymphoma, and hopefully will be approved and available for treatment soon,” she said in remarks following her presentation of PRIMO study data.
“The next question would be how to try to move this agent up front,” she added. “We’ll have to try to see what could be the possible combinations and evaluate the possible overlapping toxicity with alternative treatments.”
The PRIMO trial provides “very exciting numbers” that include roughly half of relapsed/refractory PTCL patients are responding to the oral therapy, said Andrei R. Shustov, MD, professor of medicine in the division of hematology at the University of Washington, Seattle.
Perhaps more importantly, at least half of those responses have been CRs, Dr. Shustov noted in an interview: “We haven’t seen this yet in T-cell lymphomas, short of brentuximab vedotin targeting CD30,” he said, referring to the 2018 Food and Drug Administration approval of brentuximab vedotin for previously untreated CD30-expressing PTCL.
If duvelisib is approved, it would be the first oral agent with an indication for relapsed/refractory PTCL, which could have important implications for patient quality of life, Dr. Shustov added.
“The fact that you can take a pill at home, and don’t have to be in clinic once a week, or have the port device, or be infused every week would be an incredible change in quality of life,” he said, “and this is really amplified in the older population where quality of life is so important.”
Duvelisib was FDA approved in 2018, at a dose of 25 mg orally twice daily, for the treatment of chronic lymphocytic leukemia/small lymphocytic lymphoma, and follicular lymphoma, following at least two previous treatments.
In relapsed/refractory PTCL, results of a phase 1 study previously published in Blood showed that duvelisib demonstrated an ORR of 50%, or 8 out of 16 patients treated with 25 or 75 mg twice daily continuously.
The phase 2 study described by Dr. Pro at this year’s ASH meeting included 33 patients with relapsed/refractory PTCL treated with duvelisib 25 mg or 75 mg twice daily as part of a dose-optimization phase, and 25 patients treated in an expansion phase at 75 mg twice daily for two 28-day cycles, followed by treatment at 25 mg twice daily.
Starting at the higher dose of 75 mg twice daily is intended to achieve rapid tumor control, while switching to the lower 25-mg twice-daily dose is to maintain long-term control of the disease while mitigating potential for later toxicities, according to the published abstract for the PRIMO trial.
Results of the dose-optimization phase included an ORR by independent review committee of 62% for patients treated at the 75-mg twice-daily dose, and 40% for those treated at 25 mg twice daily. The median duration of response in the 75-mg twice-daily group was 12.2 months, which Dr. Pro said was significantly higher than what was observed for the lower dose.
In the ongoing dose-expansion phase, the ORR by investigator was 52% (13 of 25 patients), with a CR rate of 36% (9 of 25 patients). The reported data show that with a median duration of follow-up of 3.78 months, the median duration of response thus far is 4.1 months.
The most common grade 3 or higher adverse events were increases in ALT and AST, seen in 24% and 20% of patients, respectively. The most common grade 3 or greater hematologic toxicity was decreased lymphocyte count, seen in 16%.
Three serious treatment-emergent adverse events thought to be related to duvelisib occurred in two patients, including grade 5 pneumonitis in one patient, and skin lesion plus posttransplant lymphoproliferative disorder in the other patient, according to Dr. Pro. Serious treatment-emergent adverse events leading to duvelisib discontinuation included increased ALT/AST in 2 patients and pneumonitis in one patient.
Grade 1-2 adverse events reported at ASH included hypertension, nausea, anemia, fatigue, diarrhea, constipation and pyrexia, among others.
Enrollment in the dose-expansion phase of PRIMO is ongoing and should be complete in February, according to Dr. Pro.
Support for the study came from Verastem Oncology and Secura Bio. Dr. Pro reported research funding from Verastem Oncology, Takeda, and other pharmaceutical companies and honoraria from Takeda and Seattle Genetics.
SOURCE: Pro B et al. ASH 2020, Abstract 44.