Dr. Link: Novel agents
“I actually happen to agree with very much of what Carla had to share, but I do have a couple of caveats,” Dr. Link said.
“The focus of this discussion is on patients with high-risk follicular lymphoma, as Carla very carefully defined in her analysis of the NLCS. These are the early progressors,” he said.
Dr. Brian K. Link
He cited data from the University of Iowa/Mayo Clinic series, validated in a cohort of patients from Lyon, France, showing that high-risk patients with early progression after immunochemotherapy had “especially poor outcomes.” In contrast, patients who were not early progressors fared quite well.
“It suggested that with agents that were available as of 2015, if you’re not an early progressor, your survival at least matches, or essentially matches with statistical power, that of the expected age- and gender-matched populations. So, novel agents are not required necessarily nor are clinical trials necessarily required for people who have good early outcomes,” Dr. Link said.
The best snapshot of current practice for high-risk patients comes from unpublished data from the NLCS showing that after a median follow-up of 8 years, 889 of 2,652 patients had received a second line of therapy, with the choice of agents or approaches generally similar between early progressors and others.
Early progressors were slightly less likely to receive rituximab monotherapy (30% vs. 36%) or an investigational agent (4.4% vs. 5.5%), whereas they were slightly more likely to receive an anthracycline (18% vs. 13%) or to undergo ASCT (3.5% vs. 1.1%).
In the treatment of patients with high-risk follicular lymphoma, a novel agent can be considered as one that was either not available or had not been used in follicular lymphoma when the previously mentioned survival data were generated, including immunomodulators such as thalidomide analogues, targeted kinase inhibitors, new anti-CD20 antibodies such as obinutuzumab (Gazyva), and immune checkpoint inhibitors.
For example, in Alliance 50803, a phase 2 trial in patients with previously untreated stage II-IV follicular lymphoma, the combination of lenalidomide (Revlimid) and rituximab was associated with a 95% overall response rate (ORR), including 72% complete response, and 5-year PFS rate of 70%, comparable to trials with rituximab plus bendamustine, CHOP, or cyclophosphamide-vincristine-prednisone, Dr. Link said.
In the phase 2 GALEN study, the combination of lenalidomide and obinutuzumab was associated with an ORR of 74% among 86 patients with relapsed/refractory follicular lymphoma, with a 1-year PFS rate of 76%.
An analysis of responses by time to relapse in GALEN showed that the ORR among 24 patients with disease progression within 24 months was 70.8%, including 33.3% complete or unconfirmed complete responses by the 1999 International Working Group criteria, and 66.7% with 54.2% complete or unconfirmed complete responses by the 2007 criteria.
Idelalisib, an inhibitor of the delta isoform of phosphatidylinositol 3-kinase (PI3K), was granted accelerated approval in 2014 for treatment of patients with follicular lymphoma after two or more prior lines of therapy, but toxicities associated with this agent caused the drug maker Gilead to dial back its development of this agent.
“But idelalisib is not the only PI3 kinase inhibitor on the block,” Dr. Link said, noting that more than a dozen similar agents are currently in development.
In clinical trials, PI3 kinase inhibitors have been associated with ORRs of about 60% in patients who experience early disease progression on other therapies, “suggesting an uncoupling between the paradigm that says that early progressors are going to have a less effective outcome than late progressors, perhaps, with targeted therapies.
The best evidence for the Bruton’s tyrosine kinase inhibitor ibrutinib (Imbruvica) comes from the DAWN study, a phase 2 trial in patients with follicular lymphoma refractory to immunochemotherapy. The drug showed some biologic activity, but only a 21% ORR.
Dr. Link noted that the S1608 trial, currently recruiting patients, may give clinicians a better idea of which novel agent is most effective. The phase 2 trial is enrolling patients with early-progressing or refractory follicular lymphoma who will be randomized to receive obinutuzumab with either the investigational PI3 kinase inhibitor TGR-1202, lenalidomide, or CHOP chemotherapy.
“High-risk follicular lymphoma is a bad hombre,” Dr. Link said. “If we want to be any smarter as a society 10 years from now, we should incorporate clinical trials with novel therapies as standard operating practice into this setting of high-risk follicular lymphoma.”
Dr. Casulo reported serving on the speakers bureau for Gilead. Dr. Link reported serving as a consultant to AbbVie, Celgene, Genentech, and Gilead.