Activity of Anti-CD19 Chimeric Antigen Receptor T Cells Against B Cell Lymphoma Is Enhanced by Antibody-Targeted Interferon-Alpha

Two Are Better than One: The Bi-Specific Antibody Mosunetuzumab Reveals an Improved Immune Response of Vγ9Vδ2 T Cells Targeting CD20 in Malignant B Cells in Comparison to the Mono-Specific Antibody Obinutuzumab

In treating cancer, immunotherapy has been established as a later-line treatment option in clinical practice. That includes stem cell transplantation, modified or activated immune cells, and antibodies directed against aberrant cells. As an unconventional immune cell subgroup, γδ T cells have been shown to provide effects against malignant cells. They exhibit an MHC-independent activation process, which could diminish graft-versus-host disease after an adoptive transfer of allogeneic cells. Over the last years, the efficacy of therapeutic antibodies has been improved. As a bi-specific antibody, mosunetuzumab binds to both CD3 and CD20, thereby providing close proximity between effector and target cells. Here, we set out to analyze the efficiency of γδ T cells' anti-tumor effects in combination with mosunetuzumab vs. the monoclonal anti-CD20 antibody obinutuzumab. Mosunetuzumab revealed improved responses of γδ T cells regarding their expression of IFN-γ and CD107a and their cytotoxicity towards malignant B cells from lymphoma B cell lines. In comparison to obinutuzumab, mosunetuzumab led to an equivalent or enhanced cytotoxicity against B cell lymphoma cell lines and primary patient samples, where this effect was even more prominent. In summary, we consider the combination of stimulated γδ T cells and mosunetuzumab to be a promising therapeutic approach for future clinical trials.

In Vitro Diffuse Large B-Cell Lymphoma Cell Line Models as Tools to Investigate Novel Immunotherapeutic Strategies

Despite the high incidence of diffuse large B-cell lymphoma (DLBCL), its management constitutes an ongoing challenge. The most common DLBCL variants include activated B-cell (ABC) and germinal center B-cell-like (GCB) subtypes including DLBCL with MYC and BCL2/BCL6 rearrangements which vary among each other with sensitivity to standard rituximab (RTX)-based chemoimmunotherapy regimens and lead to distinct clinical outcomes. However, as first line therapies lead to resistance/relapse (r/r) in about half of treated patients, there is an unmet clinical need to identify novel therapeutic strategies tailored for these patients. In particular, immunotherapy constitutes an attractive option largely explored in preclinical and clinical studies. Patient-derived cell lines that model primary tumor are indispensable tools that facilitate preclinical research. The current review provides an overview of available DLBCL cell line models and their utility in designing novel immunotherapeutic strategies.

Anti-CD19 chimeric antigen receptor T-cell followed by interferon-α therapy induces durable complete remission in donor cell-derived acute lymphoblastic leukemia: A case report

Donor cell-derived leukemia (DCL) is a special type of relapse after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Patients with DCL generally have a poor prognosis due to resistance to conventional chemotherapy. Here, we report a case of donor cell-derived acute lymphoblastic leukemia after umbilical cord blood transplantation. The patient didn't respond to induction chemotherapy. She then received anti-CD19 CAR-T cell therapy and achieved MRD-negative complete remission (CR). However, MRD levels rose from negative to 0.05% at 5 months after CAR-T cell therapy. Higher MRD levels were significantly associated with an increased risk of leukemia recurrence. Afterward, preemptive interferon-α treatment was administrated to prevent disease recurrence. To date, the patient has maintained MRD-negative CR for 41 months. Our results suggested that anti-CD19 CAR-T cells followed by interferon-α therapy are effective in treating donor cell-derived acute lymphoblastic leukemia. This report provides a novel strategy for the treatment of DCL.

89Zr-ImmunoPET shows therapeutic efficacy of anti-CD20 interferon-α fusion protein in a murine B-cell lymphoma model

Antibody-mediated tumor delivery of cytokines can overcome limitations of systemic administration (toxicity, short half-lives). Previous work showed improved anti-tumor potency of anti-CD20-interferon alpha (IFNα) fusion proteins in preclinical mouse models of B-cell lymphoma. Although tumor targeting is mediated by the antibody part of the fusion protein, the cytokine component might strongly influence biodistribution and pharmacokinetics, as a result of its affinity, size, valency and receptor distribution. Here, we used positron emission tomography (immunoPET) to study the in vivo biodistribution and tumor targeting of the anti-CD20 rituximab-murine IFNα1 fusion protein (Rit-mIFNα) and compared it to the parental mAb (rituximab, Rit). Rit-mIFNα and Rit were radiolabeled with zirconium-89 (89Zr, t1/2 78.4 h) and injected into C3H mice bearing syngeneic B-cell lymphomas (38C13-hCD20). Dynamic (2 h p.i.) and static (4, 24 and 72 h) PET scans were acquired. Ex vivo biodistribution was performed after the final scan. Both 89Zr-Rit-mIFNα and 89Zr-Rit specifically target hCD20-expressing B-cell lymphoma in vivo. 89Zr-Rit-mIFNα showed specific uptake in tumors (7.6 {plus minus} 1.0 %ID/g at 75 h p.i.), which was significantly lower than 89Zr-Rit (38.4 {plus minus} 9.9 %ID/g, p<0.0001). ImmunoPET studies also revealed differences in the biodistribution, 89Zr-Rit-mIFNα showed rapid blood clearance and high accumulation in the liver compared with 89Zr-Rit. Importantly, immunoPET clearly revealed a therapeutic effect of the single 89Zr-Rit-mIFNα dose, resulting in smaller tumors and fewer lymph node metastases compared to mice receiving 89Zr-Rit. Mice receiving 89Zr-Rit-mIFNα had enlarged spleens, suggesting that systemic immune activation contributes to therapeutic efficacy in addition to the direct antitumoral activity of IFNα. In conclusion, immunoPET allows the non-invasive tracking and quantification of the antibody-cytokine fusion protein and helps understand the in vivo behavior and therapeutic efficacy.

A Bump in the Road: How the Hostile AML Microenvironment Affects CAR T Cell Therapy

Chimeric antigen receptor (CAR) T cells targeting CD19 have been successful treating patients with relapsed/refractory B cell acute lymphoblastic leukemia (ALL) and B cell lymphomas. However, relapse after CAR T cell therapy is still a challenge. In addition, preclinical and early clinical studies targeting acute myeloid leukemia (AML) have not been as successful. This can be attributed in part to the presence of an AML microenvironment that has a dampening effect on the antitumor activity of CAR T cells. The AML microenvironment includes cellular interactions, soluble environmental factors, and structural components. Suppressive immune cells including myeloid derived suppressor cells and regulatory T cells are known to inhibit T cell function. Environmental factors contributing to T cell exhaustion, including immune checkpoints, anti-inflammatory cytokines, chemokines, and metabolic alterations, impact T cell activity, persistence, and localization. Lastly, structural factors of the bone marrow niche, secondary lymphoid organs, and extramedullary sites provide opportunities for CAR T cell evasion by AML blasts, contributing to treatment resistance and relapse. In this review we discuss the effect of the AML microenvironment on CAR T cell function. We highlight opportunities to enhance CAR T cell efficacy for AML through manipulating, targeting, and evading the anti-inflammatory leukemic microenvironment.

EGFRvIII-CAR-T Cells with PD-1 Knockout Have Improved Anti-Glioma Activity

Glioblastoma multiforme (GBM) is the most malignant form of the brain tumors. EGFR variant III (EGFRvIII) is expressed in about 30% of GBM specimens, but not expressed in normal brain tissues. Therefore, EGFRvIII protein offers an ideal CAR-T therapeutic target for EGFRvIII-positive GBM patients. PD-L1 is expressed in a variety of cancer cells, including GBM. Tumor-associated PD-L1 can bind to PD-1 on T cells and promote apoptosis of T cells, thus suppressing the anti-cancer immune response. In our current studies, PD-1^WT EGFRvIII-CAR-T cells and PD-1^KD EGFRvIII-CAR-T cells were generated. Cytokine production and lytic activity of these two CAR-T cells against to PD-L1^WT EGFRvIII⁺ U373 cells or PD-L1^KO EGFRvIII⁺ U373 cells were evaluated. The results showed that PD-1^KD EGFRvIII-CAR-T cells and PD-1^WT EGFRvIII-CAR-T cells showed same levels of interferon-γ (IFN-γ) and interleukin-2 (IL-2) production as well as cytolytic activity against PD-L1^KO EGFRvIII⁺ U373 cells; however, PD-1^KD EGFRvIII-CAR-T cells exhibited higher levels of IFN-γ and IL-2 production as well as cytolytic activity against PD-L1⁺ EGFRvIII⁺ U373 cells than that of PD-1^WT EGFRvIII-CAR-T cells. PD-1^KD EGFRvIII-CAR-T cells also exhibited higher anti-glioma activity and longer survival in mice in vivo than that of PD-1^WT EGFRvIII-CAR-T cells. Taken together, our findings indicate that PD-1 knockout enhances lytic activity of EGFRvIII-CAR-T cells against PD-L1⁺ EGFRvIII⁺ GBM cells. These might provide a new insight into strategy of GBM CAR-T cell therapy.

Chimeric Antigen Receptor-Engineered T-Cells - A New Way and Era for Lymphoma Treatment

BACKGROUND

Patients with refractory or relapsed diffuse large B-cell lymphoma have a poor prognosis with the current standard of care.

OBJECTIVE

Chimeric Antigen Receptor T-cells (CAR T-cells) are functionally reprogrammed lymphocytes, which are able to recognize and kill tumor cells. The aim of this study is to make progress in this area.

METHODS

A mini-review was achieved using the articles published in Web of Science and PubMed in the last year and the new patents were made in this field.

RESULTS

The responses to CAR T-cell products axicabtagene ciloleucel and tisagenlecleucel are promising; the objective response rate can reach up to 83%, and the complete response rate ranges between 40 and 58%. About half of the patients may have serious side effects, such as cytokine release syndrome and neurotoxicity. Current and future developments include the improvement of CAR T-cell expansion and polyfunctionality, the combined use of CAR T-cells with a fusion protein between interferon and an anti-CD20 monoclonal antibody, with checkpoint inhibitors or small molecule sensitizers that have apoptotic-regulatory effects. Furthermore, the use of IL-12-expressing CAR T-cells, an improved technology for the production of CAR T-cells based on targeted nucleases, the widespread use of allogeneic CAR T-cells or universal CAR T-cells obtained from genetically engineered healthy donor T-cells are future developments actively considered.

CONCLUSION

CAR T-cell therapy significantly improved the outcome of patients with relapsed or refractory diffuse large B-cell lymphoma. The advances in CAR T-cells production technology will improve the results and enable the expansion of this new immunotherapy.

Chimeric Antigen Receptors Incorporating D Domains Targeting CD123 Direct Potent Mono- and Bi-specific Antitumor Activity of T Cells

Chimeric antigen receptor (CAR) T cell therapies have demonstrated impressive initial response rates in hematologic malignancies. However, relapse rates are significant, and robust efficacies in other indications, such as solid tumors, will likely require novel therapeutic strategies and CAR designs. To that end, we sought to develop simple, highly selective targeting domains (D domains) that could be incorporated into complex, multifunctional therapeutics. Herein, we describe the identification and characterization of D domains specific for CD123, a therapeutic target for hematologic malignancies, including acute myelogenous leukemia (AML). CARs comprised of these D domains mediate potent T cell activation and cytolysis of CD123-expressing target cells and induce complete durable remission in two AML xenograft models. We describe a strategy of engineering less immunogenic D domains through the identification and removal of putative T cell epitopes and investigate the binding kinetics and affinity requirements of the resultant D domain CARs. Finally, we extended the utility of D domains by generating functional, bi-specific CARs comprised of a CD123-specific D domain and a CD19-specific scFv. The properties of D domains suggest that this class of targeting domain may facilitate the development of multi-functional CARs where conventional, scFv-based designs may be suboptimal.