Jeffrey A. Jones, MD, MPH
In a little over a year, four new therapeutic options have been approved for use in the treatment of patients with chronic lymphocytic leukemia (CLL): obinutuzumab, ibrutinib, ofatumumab, and idelalisib. In a discussion at the 2015 International Congress on Hematologic Malignancies, Jeffrey Jones, MD, discussed the evidence supporting the integration of these treatments into the frontline CLL setting.
Currently, the anti–CD-20 agents obinutuzumab (Gazyva) and ofatumumab (Arzerra) are approved for use in the frontline CLL setting, while the BTK inhibitor ibrutinib (Imbruvica) and the PI3K-delta inhibitor idelalisib (Zydelig) are approved for resistant/relapsed CLL.
Before discussing these novel agents, Jones, who is Section Chief for CLL/HCL at The Ohio State University Comprehensive Cancer Center, noted that even in the targeted era, chemotherapy may still have a role in upfront CLL therapy. He specifically addressed the role of the FCR (fludarabine, cyclophosphamide, rituximab) chemoimmunotherapy regimen.
“There is a subset of younger, fitter patients with favorable genetic risk features who may enjoy prolonged survival after FCR—failure-free survival, treatment-free survival,” said Jones.
However, Jones noted that FCR has a substantial amount of toxicity. “Many of the physicians in the community practices around us in Columbus have discontinued giving FCR because it is a bit challenging for many of the patients.”
Jones said that one of the most common alternatives to FCR in frontline CLL is BR (bendamustine and rituximab). BR has been shown to have a much better toxicity profile than FCR in this setting; however, FCR bests BR in key efficacy outcomes, including complete response (CR) and progression-free survival (PFS).
Neither regimen, however, is effective in patients with a deletion of chromosome 17p, and it is in this population where the novel CLL agents are emerging as an important option in the frontline CLL setting.
“On the basis of data that are available, with much more to come, it’s already appearing that the B-cell receptor targeted agents represent a significant advance for the group of patients at highest risk of treatment failure after chemoimmunotherapy—that is patients with deletion 17p CLL.”
Jones discussed data from a small trial of ibrutinib in 31 previously untreated patients with high-risk CLL/SLL who were aged ≥65 years.1
Patients received 420 mg/daily of ibrutinib in 28-day cycles.
At a median follow-up of 22.1, months overall response rate (ORR) was 71% (n = 22; 95% CI, 52.0-85.8), including 4 CRs, one nodular partial response, and 17 partial responses (PRs).
“Progression-free survival at nearly 3 years of follow-up is largely a straight line. We talk about ‘survival curves,’ but it’s hard to call this one a curve. So for many of the patients who receive ibrutinib in the frontline, we’ll expect long progression-free survival,” said Jones.
Idelalisib has also shown promise in frontline CLL. An abstract presented at the 2013 ASCO Annual Meeting included results for frontline idelalisib plus rituximab in patients with CLL/SLL aged ≥65 years.2
Patients received 150 mg twice daily of idelalisib continuously for 48 weeks plus 375 mg/m2
of rituximab weekly for the first 8 weeks. Patients who did not progress could continue idelalisib on an extension study after 48 weeks.
In the overall population, ORR was 97%, including a 100% ORR in patients with 17p deletion or TP53 mutations (n = 9). The 100% ORR included 3 CRs and 6 PRs. PFS at 2 years’ follow-up was 93%, including in patients with deletion 17p and TP53 mutations.
These early results with frontline ibrutinib and idelalisib “suggest that the biology is feasible and we look forward to larger trials coming that will help us sort out exactly which group of high-risk patients most benefits from ibrutinib, idelalisib, or a combination with an anti-CD20 monoclonal antibody,” said Jones.
Specifically regarding the efficacy of the anti-CD20 monoclonal antibodies in the first-line setting, Jones first discussed the phase III CLL11 trial,3
which was the basis for the FDA’s approval of obinutuzumab in combination with chlorambucil as a first-line treatment for patients with CLL.
In the three-arm study, patients were randomized in a 1:2:2 ratio to receive six cycles every 28 days of chlorambucil (n = 118), chlorambucil plus obinutuzumab (n = 238), or chlorambucil plus rituximab (n = 233). The median age of these patients was 73 years. An additional 192 patients were enrolled for a second stage of the study to allow for the direct comparison of the obinutuzumab and rituximab combinations.