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. 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. While most clinically advanced T cell engaging bsAbs for B cell malignancies target CD20, there are many opportunities to develop bsAb against other targets. We previously reported on a bsAb targeting ROR1. More recently, we focused on Siglec-6, a suitable target for antibody-based therapy due to its overexpression on CLL cells and coincidental absence on most healthy cell types. The Siglec-6 binding antibody JML-1 was isolated from a patient cured of CLL by allogeneic stem cell transplantation. CAR-T cells specific for Siglec-6 based on the sequence of JML-1 effectively targeted CLL cells in vitro and in a xenograft mouse model. Using the patients antibody library our collaborator identified additional high affinity clones targeting Siglec-6 and engineered T-cell recruiting bsAbs. In vitro and in vivo these bsAbs lysed Siglec-6 expressing cell lines and primary CLL cells, while sparing most normal B cells. Using the MEC-1 CLL model, we demonstrated that an anti-Siglec-6 in a dual-affinity re-targeting (DART) format inhibited tumor growth and extended survival, comparable to a CD19-targeting control T-bsAb. 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. With the onset of the COVID pandemic and the development of vaccines for SARS-CoV2, clinical need for effective vaccination strategies became paramount. Due to the distribution of COVID vaccines under Emergency Use Authorization we could not set up prospective interventional vaccine studies. Instead, we prospectively measured anti-spike (S) Ab titers in our clinic to assess patients response to SARS-CoV2 vaccination. Further, our studies on vaccine responses in years prior to the pandemic inspired our recommendation to interrupt BTKi treatment for up to 3 weeks at the time of booster vaccination. 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. The recommendation was judiciously shared with patients expected not to suffer negative consequences as projected from our observation that medically indicated, short dosing interruptions do not reduce the long-term benefit of ibrutinib therapy. Indeed, our analysis indicates that patients who interrupted BTKi had higher anti-S Ab titers than those who continued around the time of SARS-CoV2 booster vaccination.