Immunotherapy of low grade lymphoid malignancies

National Heart, Lung, And Blood Institute

Investigators

Linked publications & trials

Abstract

Monoclonal antibodies (mAbs) combined with chemotherapy improve survival of lymphoma patients. Fc receptor-dependent effector mechanisms achieve tumor cell killing but also induce antigen loss through trogocytosis. Activation of complement can lead to cell lysis and invariably deposits complement C3 activation fragments on the cell surface. For chronic lymphocytic leukemia (CLL) it is well established that not all of the mAb-targeted B cells are killed during these reactions. Instead, substantial numbers of surviving B cells that have lost CD20 due to trogocytosis and are covalently tagged with the complement breakdown product C3d are readily demonstrable in blood and bone marrow. We tested the hypothesis that covalently attached C3d fragments deposited on B cells by anti-CD20 mAbs constitute a neoantigen suitable for targeting antigen loss variants and, when used in combination with a complement fixing mAb, can increase efficacy of mAb therapy. We generated mouse and rabbit mAbs specific for C3d and selected three mAbs that bind distinct epitopes to construct human IgG1 chimeric mAbs. In lymphoma xenografts, co-administration of anti-C3d mAbs with either rituximab or ofatumumab was more effective than the anti-CD20 mAb alone. To extend the application of this invention to Multiple Myeloma (MM) we investigated the combination of the anti-C3d mAbs with the anti-CD38 mAb daratumumab (DARA) that is widely used in patients with MM. In xenograft models, the combination of DARA + anti-C3d antibody was superior to single agent DARA. In conclusion, our findings indicate that C3d-targeting with a specific mAb can provide a decisive second hit to enhance the efficacy of complement fixing mAbs commonly used in lymphoma and MM therapy. Patients with CLL have impaired responses to vaccines, and work within our group has yielded insights informing clinical approaches to vaccination in CLL. In two open-label, single-arm clinical trials, we measured the effect of BTKis on de novo immune response against recombinant hepatitis B vaccine (HepB-CpG) and recall response against recombinant zoster vaccine (RZV, Shingrix) in CLL patients who were treatment-naive or on BTKi therapy (ibrutinib or acalabrutinib) for 6 months. The primary endpoint was serologic response to HepB-CpG (anti-HBs 10 mIU/mL) and RZV (4-fold increase in anti-glycoprotein E (gE)). 78 patients received HepB-CpG and 116 patients RZV. Among patients receiving HepG-CpG; 1 (3.8%) of 26 patients on BTKi, and 9 (28.1%) of 32 treatment-nave patients responded (P =.017). At that point, we closed the HepB-CpG arm of the study to patients on BTKi therapy due to futility. In 106 patients evaluable following RZV vaccination, the humoral response rate was significantly higher in the treatment-naive cohort (76.8%) compared to patients receiving a BTKi (40.0%; P = .0002). Similar to humoral responses, the rate of cellular immunity was significantly higher in the treatment-naive cohort (70.0%) compared to patients treated with a BTKi (41.3%; P = .0072). Median anti-gE T-cell frequencies rose from 36 cells per million prior to vaccination to 475 cells per million after completing the vaccine series. There was no difference in T-cell frequencies at baseline between cohorts. Interestingly, 39.0% of subjects attained a cellular immune response in absence of a serologic response. We investigated whether interruption of BTKi treatment for up to 3 weeks at the time of vaccination might increase vaccine responses. Our strategy was a response to the relatively low success rate of the primary vaccine series in patients with CLL and informed by our investigations on the rate of BTK resynthesis. This study is ongoing. We are also investigating whether treatment with venetoclax impairs immune responses. Immune checkpoint blockade has been shown to restore anti-tumor T-cell function and elicit durable responses in select solid and hematopoietic malignancies. However, single-agent anti-programmed death 1 (PD-1) antibodies proved less efficacious in patients with chronic lymphocytic leukemia (CLL). In patients with high-risk or relapsed/refractory CLL, we conducted a phase 2 study testing the combination of lead-in ibrutinib and up to 2 cycles of fludarabine, followed by continuous therapy with ibrutinib and 17 cycles of pembrolizumab administered every 3 weeks. A total of 15 patients were enrolled. In 10 patients evaluable for response, we observed one complete and 9 partial responses. There was no discernible benefit of the combination beyond what is expected from ibrutinib monotherapy. However, 3 weeks after the first dose of pembrolizumab we detected CD8 T-cell proliferation in a subset of patients, whom we called “immune responders”. In the responders, CD27 expressing CD8 T cells were relatively increased over immune non-responders. Paired single-cell RNA and TCR-sequencing revealed clonal expansion of activated GZMK+ CD8 effector memory and terminally differentiated effector cells. After 6 months of pembrolizumab treatment, the proportion of activated and proliferating CD8 T cells returned to baseline levels. Similarly, most novel clonotypes identified after one cycle of pembrolizumab decreased in frequency on long-term treatment. In summary, pembrolizumab did not improve the clinical response over ibrutinib monotherapy but transiently activated distinct clonotypes of CD8 T cells in a subset of CLL patients. In a collaborative agreement with Genmab, we investigated epcoritamab, a CD20xCD3 T cell engaging bispecific antibody in CLL samples in vitro and in the patient-derived xenograft model. Epcoritamab, is in clinical development for B cell malignancies. We found that epcoritamab effectively induced autologous T cells to lyse CLL cells in vitro. Compared to samples from treatment-nave patients, epcoritamab-mediated cytotoxicity was higher in PBMCs from patients being treated with a BTKi, including for patients who had progressive disease on BTKi therapy. Epcoritamab induced CLL cell lysis was correlated with effector to target ratio but not to CD20 expression. Epcoritamab expanded CD4+ and CD8+ T cells, induced memory T-cell differentiation and promoted Th1 polarization; attributes associated with long-term protective responses to cancer immunotherapy. We also tested epcoritamab in our PDX mouse model. Compared to controls treated with non-targeting B12, the median leukemic cell burden was reduced by 71% after one injection of epcoritamab and by 94% after a second injection (P = .003). There was no apparent difference in efficacy of epcoritamab against CLL cells obtained from treatment-nave patients or patients who were progressing but remained on continuous BTKi treatment. Reflecting the situation in patients, the activity of the bsAb in this model depends entirely on effector functions of autologous T cells. The Bcl-2 inhibitor venetoclax, combined with anti-CD20 antibodies, is a commonly used next therapy for patients resistant to or intolerant of BTKis. We tested single agent epcoritamab and venetoclax and their combination in PBMCs from treatment-nave, BTKi-treated, and BTKi resistant patients. In all 3 settings, the combination was significantly more cytotoxic than either agent alone. We opened a clinical trial sponsored by Genmab investigating epcoritamab in various combinations including epcoritamab with venetoclax and epcoritamab with pirtobrutinib. We enrolled 4 patients at time of reporting and have established a robust pipeline for translational analyses.