Reprogramming the immune system
showing Hodgkin lymphoma
NEW YORK—Using a 3-pronged approach to reprogram the immune system—inhibition of critical pathways, activation of others, and depletion of malignant cells—may be the best strategy to optimize immune function in B-cell lymphomas, according to Stephen M. Ansell, MD, PhD, of the Mayo Clinic in Rochester, Minnesota.
“[A]ll told, there are multiple immunological barriers to an effective immune response,” Dr Ansell said at Lymphoma & Myeloma 2015.
“So the questions are how can you use an immune checkpoint approach to try and modulate this and improve the outcome.”
Dr Ansell discussed checkpoint inhibitors, immune signal activators, and the potential of combining the approaches in Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) in a way that enhances rather than antagonizes their effects.
Blocking CTLA-4
Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) functions as an immune checkpoint that downregulates the immune system. A receptor found on the surface of inhibitor T cells, it acts as an off switch when it binds to CD80 or CD86 on the surface of antigen-presenting cells.
Ipilimumab, an antibody that targets CTLA-4, has been approved by the US Food and Drug Administration for the treatment of melanoma and is in clinical trials for lung, bladder, and prostate cancer.
Investigators wanted to see whether it also works in lymphoma, so they conducted a phase 1 study in relapsed/refractory B-cell NHL.
Eighteen patients received 3 mg/kg of ipilimumab. Two patients responded, 1 with a complete response (CR) that lasted more than 31 months, and 1 with a partial response (PR) that lasted 19 months. In 5 of 16 patients (31%), T-cell proliferation to recall antigens increased more than 2-fold.
As Dr Ansell explained, “Immune response doesn’t always correlate directly with the clinical responses. So I think we really have a lot to learn about what is really a biomarker of efficacy.”
Ipilimumab was also evaluated to treat relapse after allogeneic hematopoietic stem cell transplantation (HSCT) in 29 patients with relapsed hematologic disease. Two patients with HL achieved a CR and 1 patient with mantle cell lymphoma achieved a PR.
The investigators observed that ipilimumab did not induce or exacerbate clinical graft-versus-host disease.
Blocking PD-1
Programmed cell death protein 1 (PD-1) is a surface receptor expressed on T cells and pro-B cells. PD-1 binds 2 ligands, PD-L1 and PD-L2.
PD-1 ligands are overexpressed in inflammatory environments and attenuate the immune response through PD-1 on immune effector cells. In addition, PD-L1 expressed on malignant cells or in the tumor microenvironment suppresses tumor-infiltrating lymphocyte activity.
Pidilizumab, a humanized monoclonal antibody that binds to PD-1, weakens the apoptotic processes in lymphocytes and augments the antitumor activities of NK cells.
Investigators conducted a phase 2 trial of pidilizumab in patients with diffuse large B-cell lymphoma (DLBCL) after autologous HSCT to modulate the immune system after a transplant.
The team treated 66 patients with the antibody. At 16 months, progression-free survival (PFS) was 72%. For the 24 high-risk patients who were PET-positive after salvage chemotherapy, the 16-month PFS was 70%.
“And I think that what was most interesting,” Dr Ansell said, when focusing on the 35 patients with measurable disease after transplant, pidilizumab produced a 51% response rate “even in patients that actually had active disease.”
When pidilizumab was combined with rituximab in another trial in patients with relapsed follicular lymphoma (FL), 19 of 29 evaluable patients (66%) achieved an objective response: 15 (52%) CRs and 4 (14%) PRs.
“You might say, ‘Who cares? That’s not that great,’” Dr Ansell said. “But I think what was pretty impressive is that 52% CR rate. And most of you who treat patients with rituximab would know that that’s quite surprising, suggesting that there may be additional benefit for the use of PD-1 blockade in this subset of patients.”
