Tumour cell surface antigen targeted therapies in B-cell lymphomas: Beyond rituximab

Conditional activation of an anti-IgM antibody-drug conjugate for precise B cell lymphoma targeting

Cancerous B cells are almost indistinguishable from their non-malignant counterparts regarding their surface antigen expression. Accordingly, the challenge to be faced consists in elimination of the malignant B cell population while maintaining a functional adaptive immune system. Here, we present an IgM-specific antibody-drug conjugate masked by fusion of the epitope-bearing IgM constant domain. Antibody masking impaired interaction with soluble pentameric as well as cell surface-expressed IgM molecules rendering the antibody cytotoxically inactive. Binding capacity of the anti-IgM antibody drug conjugate was restored upon conditional protease-mediated demasking which consequently enabled target-dependent antibody internalization and subsequent induction of apoptosis in malignant B cells. This easily adaptable approach potentially provides a novel mechanism of clonal B cell lymphoma eradication to the arsenal available for non-Hodgkin's lymphoma treatment.

Diagnostic value of serum tumor-associated autoantibodies in esophageal cancer

Aim: To explore the application value of serum autoantibodies in the early diagnosis of esophageal cancer. Materials & methods: A total of 130 patients with esophageal cancer and 110 controls were included and tested by ELISA. Results: According to the receiver operating characteristic curve, total sensitivity is 83.08%, total specificity is 72.73%. A nomogram was established based on the positive judgment standard, the area under the receiver operating characteristic curve was calculated to be 0.880 after verification with the calibration curve. A 2-week follow-up analysis found compared with the preoperative control, the postoperative model integral value will significantly decrease. Conclusion: The combination of serum autoantibody groups has certain clinical application value in the early diagnosis of esophageal cancer and can be used as an auxiliary index for early diagnosis.

Therapeutic roles of antibody drug conjugates (ADCs) in relapsed/refractory lymphomas

Relapsed or refractory lymphoma is commonly treated with combination chemoimmunotherapy and cellular immunotherapy. Modest response rates and associated toxicities are obstacles to achieving durable remission using traditional cytotoxic chemotherapy, especially in frail patients with advanced disease. Antibody drug conjugates represent a new class of novel targeted agents with significant improvement in therapeutic efficacy in the treatment of lymphomas. Several of these agents, which offer improved targeting, greater potency, and better therapeutic index over traditional chemotherapy, are changing the treatment landscape for lymphomas and other hematological malignancies. Despite the therapeutic potential of these agents, the delivery and release of cytotoxic agents to malignant cells through the combination of a monoclonal antibody, payload, and linker represents a complex design challenge. This article reviews the clinical data on currently available antibody drug conjugates and the ongoing development of novel antibody drug conjugates. Antibody drug conjugates constitute an important armamentarium for treatment of lymphomas and their evolving roles in the treatment spectrum are discussed.

Specific Targeting of Lymphoma Cells Using Semisynthetic Anti-Idiotype Shark Antibodies

The B-cell receptor (BCR) is a key player of the adaptive immune system. It is a unique part of immunoglobulin (Ig) molecules expressed on the surface of B cells. In case of many B-cell lymphomas, the tumor cells express a tumor-specific and functionally active BCR, also known as idiotype. Utilizing the idiotype as target for lymphoma therapy has emerged to be demanding since the idiotype differs from patient to patient. Previous studies have shown that shark-derived antibody domains (vNARs) isolated from a semi-synthetic CDR3-randomized library allow for the rapid generation of anti-idiotype binders. In this study, we evaluated the potential of generating patient-specific binders against the idiotype of lymphomas. To this end, the BCRs of three different lymphoma cell lines SUP-B8, Daudi, and IM-9 were identified, the variable domains were reformatted and the resulting monoclonal antibodies produced. The SUP-B8 BCR served as antigen in fluorescence-activated cell sorting (FACS)-based screening of the yeast-displayed vNAR libraries which resulted after three rounds of screening in the enrichment of antigen-binding vNARs. Five vNARs were expressed as Fc fusion proteins and consequently analyzed for their binding to soluble antigen using biolayer interferometry (BLI) revealing binding constants in the lower single-digit nanomolar range. These variants showed specific binding to the parental SUP-B8 cell line confirming a similar folding of the recombinantly expressed proteins compared with the native cell surface-presented BCR. First initial experiments to utilize the generated vNAR-Fc variants for BCR-clustering to induce apoptosis or ADCC/ADCP did not result in a significant decrease of cell viability. Here, we report an alternative approach for a personalized B-cell lymphoma therapy based on the construction of vNAR-Fc antibody-drug conjugates to enable specific killing of malignant B cells, which may widen the therapeutic window for B-cell lymphoma therapy.

Polatuzumab Vedotin for the Treatment of Relapsed/Refractory Diffuse Large B-Cell Lymphoma in Transplant-Ineligible Patients

Diffuse large B-cell lymphoma is the most common subtype of non-Hodgkin lymphoma. Although 5-year survival rates in the first-line setting can range from 60% to 70%, up to 50% of patients become refractory or relapse after treatment (Crump et al., 2017). The standard treatment for relapsed/refractory diffuse large B-cell lymphoma is salvage chemotherapy followed by autologous stem cell transplant. Nonetheless, over 60% of patients are transplant ineligible, and there is currently no standard treatment option for these patients (Sarkozy & Sehn, 2018). Age, comorbidities, performance status, and disease deemed not responsive to chemotherapy conditioning are various factors potentially disqualifying patients for transplant. There is a strong demand for novel therapies. Polatuzumab vedotin, a targeted immunotherapy, was approved in 2019 by the U.S. Food & Drug Administration for the treatment of relapsed/refractory diffuse large B-cell lymphoma and is recommended by the National Comprehensive Cancer Network for patients who are transplant ineligible. This article reviews the pharmacology of polatuzumab vedotin, along with its performance in clinical trials, financial considerations, and management of adverse effects.

Development of Traceable Rituximab-Modified PEO-Polyester Micelles by Postinsertion of PEG-phospholipids for Targeting of B-cell Lymphoma

The objective of this work was to develop rituximab (RTX)-modified polymeric micelles for targeting of B-cell lymphoma cells, through postinsertion of RTX-poly(ethylene glycol)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine (RTX-PEG-DSPE) into methoxy poly(ethylene oxide)-poly(ε-caprolactone) (PEO-PCL) or methoxy poly(ethylene oxide)-poly(ε-benzylcarboxylate-ε-caprolactone) (PEO-PBCL) micelles. Mixed micelles were made traceable by introducing Cy5.5 to RTX and conjugating Cy3 to propargyl moiety, end-capped PCL or PBCL. Successful adaptation of the postinsertion method for the formation of immunomicelles was evidenced by measurement of RTX levels on the micellar surface, purified from free RTX by size exclusion chromatography, using microBSA assay. A change in the micellar diameter, from 50-70 nm for PEO-PCL and PEO-PBCL micelles and 20 nm for PEG-DSPE micelles, to 80-95 nm for the mixed micellar population as well as the critical micellar concentration of mixed micelles provided further proof for the success of the postinsertion method applied here. Mixed micelles containing PCL or PBCL with a degree of polymerization of 22 (PCL₂₂ and PBCL₂₂) were thermodynamically and kinetically more stable than those with PCL₁₅. Accordingly, RTX micelles containing PCL₂₂ or PBCL₂₂ showed a higher percentage of Cy³⁺/Cy^5.5+ cell population in CD20⁺ KG-15 cells, than those with PCL₁₅. The percentage of Cy³⁺/Cy^5.5+ cell population drastically reduced in the presence of competing RTX for micelles containing PCL₂₂ or PBCL₂₂ cores, indicating the superiority of these structures for active targeting of CD20⁺ cells. No significant difference in the cytotoxicity of paclitaxel in RTX-micelles versus plain ones was observed, reflecting the noninternalizing function of CD20. The results show that traceable mixed micelles prepared through postinsertion of RTX-PEG-DSPE to PEO-PCL₂₂ or PEO-PBCL₂₂ micelles can be used for targeting and/or imaging of CD20⁺ B cell lymphoma cells. The postinsertion method can be adopted to prepare other PEO-poly(ester)-based immunomicelles for active targeting of other diseased cells.

Assessment of CD52 expression in "double-hit" and "double-expressor" lymphomas: Implications for clinical trial eligibility

"Double-hit" and "double-expressor" lymphomas represent distinct but overlapping subsets of aggressive B-cell non-Hodgkin lymphoma. The high rates of bone marrow involvement by these lymphomas pose a major therapeutic challenge due to the chemotherapy-resistant nature of the bone marrow microenvironment and the limited utility of rituximab-based salvage regimens in patients with relapsed/refractory disease. Preclinical studies utilizing high-dose cyclophosphamide in combination with the anti-CD52 monoclonal antibody alemtuzumab have recently shown promise in the treatment of intramedullary disease, and a Phase I human trial is now underway. In support of such efforts, here we perform CD52 target validation on a series of double-hit (n = 40) and double-expressor (n = 58) lymphomas using immunohistochemistry. CD52 expression levels varied considerably across samples, however positive staining was observed in 75% of both double-hit and double-expressor lymphomas. Similarly, high levels of CD52 expression were seen in patients whose disease was associated with high-risk clinical features, including primary refractory status (73%), higher IPI score (76%), and bone marrow involvement (74%). CD52 expression was not significantly correlated with diagnostically relevant pathologic features such as morphology, cytogenetic findings or other immunophenotypic features, but was notably present in all cases lacking CD20 expression (n = 6). We propose that CD52 expression status be evaluated on a case-by-case basis to guide eligibility for clinical trial enrollment.

IMGN779, a Novel CD33-Targeting Antibody-Drug Conjugate with DNA-Alkylating Activity, Exhibits Potent Antitumor Activity in Models of AML

The myeloid differentiation antigen CD33 has long been exploited as a target for antibody-based therapeutic approaches in acute myeloid leukemia (AML). Validation of this strategy was provided with the approval of the CD33-targeting antibody-drug conjugate (ADC) gemtuzumab ozogamicin in 2000; the clinical utility of this agent, however, has been hampered by safety concerns. Thus, the full potential of CD33-directed therapy in AML remains to be realized, and considerable interest exists in the design and development of more effective ADCs that confer high therapeutic indices and favorable tolerability profiles. Here, we describe the preclinical characterization of a novel CD33-targeting ADC, IMGN779, which utilizes a unique DNA-alkylating payload to achieve potent antitumor effects with good tolerability. The payload, DGN462, is prototypical of a novel class of purpose-created indolinobenzodiazeprine pseudodimers, termed IGNs. With low picomolar potency, IMGN779 reduced viability in a panel of AML cell lines in vitro Mechanistically, the cytotoxic activity of IMGN779 involved DNA damage, cell-cycle arrest, and apoptosis consistent with the mode of action of DGN462. Moreover, IMGN779 was highly active against patient-derived AML cells, including those with adverse molecular abnormalities, and sensitivity correlated to CD33 expression levels. In vivo, IMGN779 displayed robust antitumor efficacy in multiple AML xenograft and disseminated disease models, as evidenced by durable tumor regressions and prolonged survival. Taken together, these findings identify IMGN779 as a promising new candidate for evaluation as a novel therapeutic in AML. Mol Cancer Ther; 17(6); 1271-9. ©2018 AACR.

Evaluation of Next-Generation Anti-CD20 Antibodies Labeled with 89Zr in Human Lymphoma Xenografts

Radioimmunotherapies with monoclonal antibodies to the B-lymphocyte antigen 20 (CD20) are effective treatments for B-cell lymphomas, but U.S. Food and Drug Administration-approved radioimmunotherapies exclusively use radiolabeled murine antibodies, potentially limiting redosing. The Food and Drug Administration recently approved 2 unlabeled anti-CD20 monoclonal antibodies, obinutuzumab and ofatumumab, termed next generation as they are humanized (obinutuzumab) or fully human (ofatumumab), thus potentially allowing a greater potential for redosing than with previous-generation anti-CD20 antibodies, including rituximab (chimeric) and tositumomab (murine), which contain more murine peptide sequences. We prepared ⁸⁹Zr-ofatumumab and ⁸⁹Zr-obinituzumab and assessed their tumor targeting by PET/CT imaging and their biodistribution in a preclinical mouse model with CD20 xenografts to determine whether these antibodies have potential as theranostics or for radioimmunotherapy. Methods: Obinutuzumab, ofatumumab, rituximab, tositumomab, and human IgG (as control) were radiolabeled with ⁸⁹Zr. Raji Burkitt lymphoma xenografts were established in severe combined immunodeficient mice. Mice with palpable tumors (n = 4-9) were injected with ⁸⁹Zr-obinutuzumab, ⁸⁹Zr-ofatumumab, ⁸⁹Zr-rituximab, ⁸⁹Zr-tositumomab, or ⁸⁹Zr-IgG, with small-animal PET/CT images acquired at 1, 3, and 7 d after injection, and then sacrificed for biodistribution analyses. Results: At 1, 3, and 7 d after injection, all anti-CD20 antibodies showed clear tumor uptake on PET/CT, with minimal tumor uptake of IgG. Biodistribution data showed significantly (P < 0.005) higher tumor uptake for obinutuzumab (41.4 ± 7.6 percentage injected dose [%ID]/g), ofatumumab (32.6 ± 17.5 %ID/g), rituximab (28.6 ± 7.6 %ID/g), and tositumomab (28.0 ± 6.5 %ID/g) than IgG (7.2 ± 1.2 %ID/g). Tositumomab had much higher splenic uptake (186.4 ± 49.7 %ID/g, P < 0.001) than the other antibodies. Conclusion:⁸⁹Zr-labeled obinutuzumab and ofatumumab localized to tumor as well as or better than labeled rituximab and tositumomab, 2 monoclonal antibodies that have been used previously in B-cell lymphoma radioimmunotherapy, and both obinutuzumab and ofatumumab have the potential for repeated dosing.

The Antitumor Activity of IMGN529, a CD37-Targeting Antibody-Drug Conjugate, Is Potentiated by Rituximab in Non-Hodgkin Lymphoma Models

Naratuximab emtansine (IMGN529) is an investigational antibody-drug conjugate consisting of a CD37-targeting antibody conjugated to the maytansine-derived microtuble disruptor, DM1. IMGN529 has shown promising preclinical and clinical activity in non-Hodgkin lymphoma, including diffuse large B-cell lymphoma (DLBCL). Due to the aggressive nature of the disease, DLBCL is often treated with combination therapies to maximize clinical outcomes; therefore, we investigated the potential of combining IMGN529 with both standard-of-care and emerging therapies against multiple oncology-relevant targets and pathways. The strongest enhancement in potency was seen with anti-CD20 antibodies, including rituximab. The combination of IMGN529 and rituximab was more potent than either agent alone, and this combinatorial benefit was associated with increased apoptotic induction and cell death. Additional studies revealed that rituximab treatment increased the internalization and degradation of the CD37-targeting antibody moiety of IMGN529. The combination of IMGN529 and rituximab was highly efficacious in multiple xenograft models, with superior antitumor efficacy seen compared to either agent alone or treatment with R-CHOP therapy. These findings suggest a novel mechanism whereby the potency of IMGN529 can be enhanced by CD20 binding, which results in the increased internalization and degradation of IMGN529 leading to the generation of greater amounts of cytotoxic catabolite. Overall, these data provide a biological rationale for the enhanced activity of IMGN529 in combination with rituximab and support the ongoing clinical evaluation of IMGN529 in combination with rituximab in patients with relapsed and/or refractory DLBCL.