Monoclonal antibodies targeting CD38 in hematological malignancies and beyond

Impact of new myeloma agents on the transfusion laboratory

Monoclonal antibody (mAb) therapy targeting CD38 and CD47 antigens expressed on cancer cells has transformed therapy options for patients with multiple myeloma as well as other haematological and non-haematological malignancies. While the on target effects of these new drugs highlight the promise of precision cancer therapeutics, the unintended, off target binding of drugs to red blood cells (RBCs) and platelets has required transfusion service laboratories (TSL) and immunohaematology reference laboratories (IRL) to innovate and rapidly set up processes and testing protocols to overcome the significant interference in routine pre-transfusion tests caused by these agents. Binding of anti-CD38 and anti-CD47 drugs to reagent RBCs leads to false positive pan-agglutination during the antihuman globulin phase of testing, making it difficult to rule out underlying alloantibodies, and leading to delays in setting up compatible units for RBC transfusion. Anti-CD47 agents can also interfere with ABO/Rh typing studies. Several methods to successfully mitigate interference have been described, such as treatment of reagent RBCs with reducing agents or enzymes, allogeneic RBC adsorption studies and drug specific neutralisation assays; all methods have limitations. TSLs should select an approach that best fits their workflow and expertise and takes into consideration their level of access to specialised outside testing, local blood supplier capabilities, and the type of patient population served. For platelet refractory patients, samples should be tested by platelet antibody assays that are known to be unaffected by drug therapy. RBC transfusion support for multiple myeloma patients receiving anti-CD38 or anti-CD47 drugs can be optimised by establishing good communication between the clinical teams and TSLs, building electronic notification processes, and ensuring timely completion of baseline pre-transfusion testing and RBC phenotype/genotype prior to starting therapy. Staff education, standardisation of laboratory mitigation measures, and implementation of testing algorithms that consider mAb-induced interference when working up a pan-agglutinin help to significantly decrease delays that would otherwise result if standard methods were employed to complete antibody identification studies.

Evaluation of Cardiac Repolarization in the Randomized Phase 2 Study of Intermediate- or High-Risk Smoldering Multiple Myeloma Patients Treated with Daratumumab Monotherapy

Introduction

Daratumumab is a CD38-targeting monoclonal antibody that has demonstrated clinical benefit for multiple myeloma. Daratumumab inhibition of CD38, which is expressed on immune cell populations and cardiomyocytes, could potentially affect cardiac function. This QTc substudy of the phase 2 CENTAURUS study investigated the potential effect of intravenous daratumumab monotherapy on QTc prolongation and other electrocardiogram (ECG) parameters, including concentration-QTc effect modeling.

Methods

Patients had intermediate- or high-risk smoldering multiple myeloma. Patients with QT interval corrected by Fridericia’s formula (QTcF) > 470 ms, QRS interval ≥ 110 ms, or PR interval ≥ 200 ms were excluded. Triplicate ECGs were collected at screening, Dose 1, and Dose 8. Analyses of on-treatment ECGs were conducted with a time-matched baseline (primary analysis). By time-point, pharmacokinetic-pharmacodynamic (PK/PD), and outlier analyses were conducted.

Results

Of 123 patients in CENTAURUS, 31 were enrolled in the QTc substudy. Daratumumab produced a small increase in heart rate (5–12 beats per minute) of unclear significance. There was a small but clinically insignificant effect on QTc, as measured by both time-matched time-point and PK/PD analyses. The primary analysis demonstrated a maximum mean increase in QTcF of 9.1 ms (90% 2-sided upper confidence interval [CI], 14.1 ms). The primary PK/PD analysis predicted a maximum QTcF increase of 8.5 ms (90% 2-sided upper CI, 13.5 ms). No patient had an abnormal U wave, a new QTcF > 500 ms, or > 60 ms change from baseline for QTcF.

Conclusion

Analysis of ECG intervals and concentration-QTc relationships showed a small but clinically insignificant effect of daratumumab.

Trial Registration

ClinicalTrials.gov Identifier: NCT02316106.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12325-020-01601-w.

Health-Related Quality of Life in Transplant-Ineligible Patients With Newly Diagnosed Multiple Myeloma: Findings From the Phase III MAIA Trial

PURPOSE

To evaluate the effects of daratumumab, lenalidomide, and dexamethasone (D-Rd) versus lenalidomide and dexamethasone (Rd) on patient-reported outcomes (PROs) in the phase III MAIA study.

PATIENTS AND METHODS

PROs were assessed on the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30-item and the EuroQol 5-dimensional descriptive system at baseline and every 3 months during treatment. By mixed-effects model, changes from baseline are presented as least squares means with 95% CIs.

RESULTS

A total of 737 transplant-ineligible (TIE) patients with newly diagnosed multiple myeloma were randomly assigned to D-Rd (n = 368) or Rd (n = 369). Compliance with PRO assessments was high at baseline (> 90%) through month 12 (> 78%) for both groups. European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30-item global health status scores improved from baseline in both groups and were consistently greater with D-Rd at all time points. A global health status benefit was achieved with D-Rd, regardless of age (< 75 and ≥ 75 years), baseline Eastern Cooperative Oncology Group (ECOG) performance status score, or depth of response. D-Rd treatment resulted in significantly greater reduction in pain scores as early as cycle 3 (P = .0007 v Rd); the magnitude of change was sustained through cycle 12. Reductions in pain with D-Rd were clinically meaningful in patients regardless of age, ECOG status, or depth of response. Similarly, PRO improvements were observed with D-Rd and Rd on the EuroQol 5-dimensional descriptive system visual analog scale score.

CONCLUSION

D-Rd compared with Rd was associated with faster and sustained clinically meaningful improvements in PROs, including pain, in transplant-ineligible patients with newly diagnosed multiple myeloma regardless of age, baseline ECOG status, or depth of treatment response.

Updating targets for natural killer/T-cell lymphoma immunotherapy

Natural killer/T-cell lymphoma (NKTCL) is a highly invasive subtype of non-Hodgkin lymphoma, typically positive for cytoplasmic CD3, CD56, cytotoxic markers, including granzyme B and TIA1, and Epstein-Barr virus (EBV). The current treatment methods for NKTCL are associated with several drawbacks. For example, chemotherapy can lead to drug resistance, while treatment with radiotherapy alone is inadequate and results in frequent relapses. Moreover, hematopoietic stem cell transplantation exhibits limited efficacy and is not well recognized by domestic and foreign experts. In recent years, immunotherapy has shown good clinical results and has become a hot spot in cancer research. Clinical activity of targeted antibodies, such as daratumumab (anti-CD38 antibody) and brentuximab vedotin (anti-CD30 antibody), have been reported in NKTCL. Additionally, dacetuzumab and Campath-1H have demonstrated promising results. Further encouraging data have been obtained using checkpoint inhibitors. The success of these immunotherapy agents is attributed to high expression levels of programmed death-ligand 1 in NKTCL. Furthermore, anti-CCR4 monoclonal antibodies (mAbs) exert cytotoxic actions on both CCR4+ tumor cells and regulatory T cells. Depletion of these cells and the long half-life of anti-CCR4 mAbs result in enhanced induction of antitumor effector T cells. The role of IL10 in NKTCL has also been investigated. It has been proposed that exploitation of this cytokine might provide potential novel therapeutic strategies. Cellular immunotherapy with engineered cytotoxic T lymphocytes targeted against LMP1 and LMP2 has shown promising results and sustained remission. Cellular immunotherapy may be used either as maintenance therapy following initial induction chemotherapy or in cases of relapsed/refractory disease. The present review outlines the known immunotherapy targets for the treatment of NKTCL.

Nanobodies as probes to investigate purinergic signaling

Nanobodies (VHHs) are the single variable immunoglobulin domains of heavy chain antibodies (hcAbs) that naturally occur in alpacas and other camelids. The two variable domains of conventional antibodies typically interact via a hydrophobic interface. In contrast, the corresponding surface area of nanobodies is hydrophilic, rendering these single immunoglobulin domains highly soluble, robust to harsh environments, and exceptionally easy to format into bispecific reagents. In homage to Geoffrey Burnstock, the pioneer of purinergic signaling, we provide a brief history of nanobody-mediated modulation of purinergic signaling, using our nanobodies targeting P2X7 and the NAD⁺-metabolizing ecto-enzymes CD38 and ARTC2.2 as examples.

Daratumumab and Nanobody-Based Heavy Chain Antibodies Inhibit the ADPR Cyclase but not the NAD+ Hydrolase Activity of CD38-Expressing Multiple Myeloma Cells

Simple Summary

Multiple myeloma is a hematological malignancy of antibody-producing plasma cells in the bone marrow. Nucleotides released from cells in the tumor microenvironment act as inflammatory danger signals. CD38 and other enzymes on the surface of cancer cells hydrolyze these nucleotides to immunosuppressive mediators, thereby hampering anti-tumor immune responses. Daratumumab and other CD38-specific antibodies mediate killing of tumor cells by natural killer cells, macrophages, and the complement system. Here, we investigated whether CD38-specific antibodies also inhibit the enzyme activity of CD38-expressing tumor cells, thereby providing a potential second mode of action. Our results showed that daratumumab and nanobody-based heavy chain antibodies inhibit the ADPR cyclase but not the NAD⁺ hydrolase activity of CD38. Thus, there remains a need for better CD38-inhibitory antibodies.

Abstract

The nucleotides ATP and NAD⁺ are released from stressed cells as endogenous danger signals. Ecto-enzymes in the tumor microenvironment hydrolyze these inflammatory nucleotides to immunosuppressive adenosine, thereby, hampering anti-tumor immune responses. The NAD⁺ hydrolase CD38 is expressed at high levels on the cell surface of multiple myeloma (MM) cells. Daratumumab, a CD38-specific monoclonal antibody promotes cytotoxicity against MM cells. With long CDR3 loops, nanobodies and nanobody-based heavy chain antibodies (hcAbs) might bind to cavities on CD38 and thereby inhibit its enzyme activity more potently than conventional antibodies. The goal of our study was to establish assays for monitoring the enzymatic activities of CD38 on the cell surface of tumor cells and to assess the effects of CD38-specific antibodies on these activities. We monitored the enzymatic activity of CD38-expressing MM and other tumor cell lines, using fluorometric and HPLC assays. Our results showed that daratumumab and hcAb MU1067 inhibit the ADPR cyclase but not the NAD⁺ hydrolase activity of CD38-expressing MM cells. We conclude that neither clinically approved daratumumab nor recently developed nanobody-derived hcAbs provide a second mode of action against MM cells. Thus, there remains a quest for “double action” CD38-inhibitory antibodies.

Crystal structure of CD38 in complex with daratumumab, a first-in-class anti-CD38 antibody drug for treating multiple myeloma

Multiple myeloma is a blood cancer characterized by the plasma cell malignancy in the bone marrow, resulting in the destruction of bone tissue. Recently, the US FDA approved two antibody drugs for the treatment of multiple myeloma, daratumumab and isatuximab, targeting CD38, a type II transmembrane glycoprotein highly expressed in plasma cells and multiple myeloma cells. Here, we report the crystal structure of CD38 in complex with the Fab fragment of daratumumab, providing its exact epitope on CD38 and the structural insights into the mechanism of action of the antibody drug. Daratumumab binds to a specific discontinuous region on CD38 that includes residues located opposite to the active site of CD38. All the six complementarity determining regions of daratumumab are involved in the CD38 interaction. The epitopes of daratumumab and isatuximab do not overlap at all and their bindings to CD38 induce different structural changes within the CD38 protein. This structural study can facilitate the design of improved biologics or effective combination therapies for the treatment of multiple myeloma.

A newly devised flow cytometric antibody binding assay helps evaluation of dithiothreitol treatment for the inactivation of CD38 on red blood cells

BACKGROUND AND OBJECTIVES

Anti-CD38 monoclonal antibodies, including daratumumab and isatuximab, often interfere with pretransfusion testing. Dithiothreitol (DTT) treatment of red blood cells (RBCs) negates this interference. However, the optimum DTT concentration and treatment time have not been well defined. Here, we quantified CD38 on RBCs before and after DTT treatment using a flow cytometric antibody binding assay (FABA) to specify the optimum conditions for CD38 inactivation.

MATERIALS AND METHODS

For FABA, untreated or DTT-treated RBCs were incubated with fluorescein isothiocyanate-labelled anti-CD38 antibody, in the presence or absence of 100-fold or more excess of unlabelled anti-CD38 antibody, and then analysed by flow cytometry (FCM). Dissociation of CD38-positive and control histograms was determined from the D-value using the Kolmogorov-Smirnov test. The results from FABA were compared with those from conventional FCM, indirect antiglobulin test (IAT) and Western blotting.

RESULTS

The results from FABA were more consistent than those from conventional FCM. The D-value was found to be reliable in the analysis of difference between CD38 before and after DTT treatment. Our data showed that 0·0075 mol/l DTT for 30 min is sufficient to inactivate CD38 on RBCs. These results were stable and consistent with the findings from IAT.

CONCLUSION

Flow cytometric antibody binding assay is an objective way of evaluating the efficacy of DTT treatment for CD38 on RBCs. This approach allows the detection of a small number of cell surface antigens and will be useful for assessing the various chemical treatments to denature RBC antigens.

CD38 in cancer-associated fibroblasts promotes pro-tumoral activity

Primary and metastatic melanoma progression are supported by a local microenvironment comprising, inter alia, of cancer-associated fibroblasts (CAFs). We previously reported in orthotropic/syngeneic mouse models that the stromal ectoenzyme CD38 participates in melanoma growth and metastasis. The results presented here suggest that CD38 is a novel regulator of CAFs' pro-tumorigenic functions. Orthotopic co-implantation of CD38 deficient fibroblasts and B16F10 melanoma cells limited tumor size, compared with CD38-expressing fibroblasts. Intrinsically, CAF-CD38 promoted migration of primary fibroblasts toward melanoma cells. Further, in vitro paracrine effects of CAF-CD38 fostered tumor cell migration and invasion as well as endothelial cell tube formation. Mechanistically, we report that CAF-CD38 drives the protein expression of an angiogenic/pro-metastatic signature, which includes VEGF-A, FGF-2, CXCL-12, MMP-9, and HGF. Data suggest that CAF-CD38 fosters tumorigenesis by enabling the production of pro-tumoral factors that promote cell invasion, migration, and angiogenesis.

CD38: An Immunomodulatory Molecule in Inflammation and Autoimmunity

CD38 is a molecule that can act as an enzyme, with NAD-depleting and intracellular signaling activity, or as a receptor with adhesive functions. CD38 can be found expressed either on the cell surface, where it may face the extracellular milieu or the cytosol, or in intracellular compartments, such as endoplasmic reticulum, nuclear membrane, and mitochondria. The main expression of CD38 is observed in hematopoietic cells, with some cell-type specific differences between mouse and human. The role of CD38 in immune cells ranges from modulating cell differentiation to effector functions during inflammation, where CD38 may regulate cell recruitment, cytokine release, and NAD availability. In line with a role in inflammation, CD38 appears to also play a critical role in inflammatory processes during autoimmunity, although whether CD38 has pathogenic or regulatory effects varies depending on the disease, immune cell, or animal model analyzed. Given the complexity of the physiology of CD38 it has been difficult to completely understand the biology of this molecule during autoimmune inflammation. In this review, we analyze current knowledge and controversies regarding the role of CD38 during inflammation and autoimmunity and novel molecular tools that may clarify current gaps in the field.

Selection of new immunotherapy targets for NK/T cell lymphoma

Extranodal NK/T cell lymphoma, nasal type, is a rare type of non-Hodgkin's lymphoma (NHL), and the aetiology is not fully understood. Although the clinical outcome of anthracycline-based chemotherapy was dismal because of multidrug resistance (MDR). Novel therapeutic strategies including L-asparaginase-containing regimens, radiotherapy, sequential chemotherapy and radiotherapy, and concurrent chemoradiotherapy (CCRT) have remarkably improved outcomes. However, the overall survival (OS) rate of advanced stage patients is not satisfactory compared with patients with non-advanced-stage disease. Immunotherapy is a promising treatment for ENKTCL. Indeed, it has been proven that targeted therapies such as anti-CD30 antibodies and naked anti-CD38 antibodies are effective. In addition to these therapies that target cell surface antigens, therapies targeting intracellular signalling pathways and the microenvironment are considerably beneficial. EBV-driven overexpression of latent membrane proteins [LMP1 and LMP2] activates the pro-proliferation NF-κB/MAPK signalling pathway and leads to high PD-L1 expression. Binding of PD-L1 to PD-1 expressing cytotoxic T cells causes apoptosis and inactivation of T lymphocytes, achieving immune escape. On the basis of this mechanism, a variety of small molecular inhibitors, such as anti-PD-1 antibodies, NF-κB inhibitors, EBV antigens, and LMP1 and LMP2 antigens, can be applied. Via another signalling pathway the JAK/STAT pathway, upregulation and activation and mutation of genes promotes proliferation and ENKTCL lymphomagenesis, and JAK inhibitors have thus been applied. This article reviews recent advances in ENKTCL immunotherapy as a promising treatment for this fatal disease.

Drug-Disease Interaction and Time-Dependent Population Pharmacokinetics of Isatuximab in Relapsed/Refractory Multiple Myeloma Patients

Isatuximab, a monoclonal antibody (mAb) of immunoglobulin G (IgG) isotype, specifically targets the cluster of differentiation 38 antigen overexpressed in malignant plasma cells. Isatuximab is used to treat multiple myeloma (MM), characterized by the excessive production of abnormal "myeloma proteins" (M-proteins) that may interact with therapeutic IgG mAb on the neonatal Fc receptor (FcRn)-mediated recycling pathway. The clinical pharmacology profile of isatuximab was investigated by population pharmacokinetics (PKs) modeling in 476 patients with MM who received 1-20 mg/kg isatuximab either as single agent or in combination with pomalidomide-dexamethasone in 4 clinical trials. Isatuximab PKs were characterized by a two-compartment model with parallel time-varying linear clearance (CL) and nonlinear elimination. Due to a mechanism-based drug-disease interaction, patients secreting IgG M-protein exhibited a twofold lower drug exposure compared with patients with non-IgG MM. No dose adjustment was required based on MM immunoglobulin type because efficacy and safety profiles were comparable between IgG and non-IgG MM subpopulations. β2-microglobulin, body weight, sex, drug material, and race have a limited effect on drug exposure and do not require any dose adjustment. A typical 50% decrease in linear CL from initial treatment to steady-state was predicted, and this decrease correlated with the best overall response rate and was slower for patients with IgG MM. These findings suggest that the time-dependent effect of isatuximab is likely mediated by a combined factor of both disease state evolution and the perturbation of the FcRn-mediated recycling pathway.

How Does Complement Affect Hematological Malignancies: From Basic Mechanisms to Clinical Application

Complement, as a central immune surveillance system, can be activated within seconds upon stimulation, thereby displaying multiple immune effector functions. However, in pathologic scenarios (like in tumor progression), activated complement can both display protective effects to control tumor development and passively promotes the tumor growth. Clinical investigations show that patients with several hematological malignancies often display abnormal level of specific complement components, which in turn modulates complement activation or deregulated cascade. In the past decades, complement-dependent cytotoxicity and complement-dependent cell-mediated phagocytosis were fully approved to display vital roles in monoclonal antibody-based immunotherapies, especially in therapies against hematological malignancies. However, tumor-mediated complement evasion presents a big challenge for such a therapy. This review aims to provide an integrative overview on the roles of the complement in tumor promotion, highlights complement mediated effects on antibody-based immunotherapy against distinct hematological tumors, hopefully provides a theoretical basis for the development of complement-based cancer targeted therapies.

Monoclonal antibodies as an addition to current myeloma therapy strategies

INTRODUCTION

Immunotherapy has emerged as a major class in the therapeutic arsenal of multiple myeloma. Cell-based immunotherapy (CAR T-cells) and monoclonal antibody-based immunotherapy (naked monoclonal antibodies, antibody-drug conjugates, and bispecific T-cell engagers) are the two cornerstones of this novel approach for myeloma patients. Among numerous targets evaluated in the previous decade; CD38, SLAMF7, and, more recently, BCMA stand as the most promising.

AREAS COVERED

This review presents and discusses the currently available data regarding monoclonal antibodies in the treatment of multiple myeloma.

EXPERT OPINION

Anti-CD38-naked monoclonal antibodies have become a standard-of-care in multiple myeloma, greatly improving the depth and duration of response when combined with conventional therapy. Elotuzumab is approved in the relapse setting in combination with pomalidomide and maybe an interesting option in patients whose disease became refractory to anti-CD38 monoclonal antibodies. Anti-BCMA drug conjugates and bispecific T-cell engager antibodies are promising new molecules in the multiple myeloma armamentarium.

Complement System: a Neglected Pathway in Immunotherapy

Approved for the treatment of autoimmune diseases, hematological malignancies, and solid cancers, several monoclonal antibodies (mAb) make use of complement in their mechanism of action. Such an assessment is based on comprehensive investigations that used mouse models, in vitro studies, and analyses from patients at initiation (basal level to highlight deficiencies) and after treatment initiation (mAb impact on complement), which have further provided key insights into the importance of the complement activation and/or complement deficiencies in mAb activity. Accordingly, new approaches can now be developed with the final objective of increasing the clinical efficacy of mAb. These improvements include (i) the concurrent administration of fresh frozen plasma during mAb therapy; (ii) mAb modifications such as immunoglobulin G subclass switching, Fc mutation, or IgG hexamerization to improve the fixation and activation of C1q; (iii) optimization of the target recognition to induce a higher complement-dependent cytotoxicity (CDC) and/or complement-dependant cellular cytotoxicity (CDCC); and (iv) the control of soluble and cellular complement inhibitors.

Complement System: Promoter or Suppressor of Cancer Progression?

Constituent of innate immunity, complement is present in the tumor microenvironment. The functions of complement include clearance of pathogens and maintenance of homeostasis, and as such could contribute to an anti-tumoral role in the context of certain cancers. However, multiple lines of evidence show that in many cancers, complement has pro-tumoral actions. The large number of complement molecules (over 30), the diversity of their functions (related or not to the complement cascade), and the variety of cancer types make the complement-cancer topic a very complex matter that has just started to be unraveled. With this review we highlight the context-dependent role of complement in cancer. Recent studies revealed that depending of the cancer type, complement can be pro or anti-tumoral and, even for the same type of cancer, different models presented opposite effects. We aim to clarify the current knowledge of the role of complement in human cancers and the insights from mouse models. Using our classification of human cancers based on the prognostic impact of the overexpression of complement genes, we emphasize the strong potential for therapeutic targeting the complement system in selected subgroups of cancer patients.

Preclinical Development of Near-Infrared-Labeled CD38-Targeted Daratumumab for Optical Imaging of CD38 in Multiple Myeloma

PURPOSE

Cluster of differentiation 38 (CD38) is a promising therapeutic target in multiple myeloma (MM) patients and has resulted in the development of several CD38 immunotherapies. Current methods to evaluate CD38 expression in the preclinical setting include ex vivo flow cytometry and immunohistochemistry, which can be cumbersome and do not give whole-body information. In vivo imaging technologies such as positron emission tomography rely on decay of radioisotopes, limiting the number of molecular interactions observed at any given time point. Here, we demonstrate the use of near-infrared (NIR) fluorescence imaging for spatiotemporal monitoring of CD38 expression in preclinical MM using the anti-CD38 daratumumab (DARA) conjugated to the NIR fluorophore IRDye800CW (DARA-IRDye800).

PROCEDURES

Stability studies with human serum and binding assays with human myeloma cells were performed with DARA-IRDye800. Immunocompromised mice with intra- and extramedullary tumors (n = 5/group) were administered with DARA-IRDye800 for in vivo imaging up to 7 days after injection. Ex vivo biodistribution and flow cytometry studies were performed to validate in vivo imaging results. A separate therapy study was performed in mice with intramedullary tumors that were treated and not treated with DARA at a therapeutic dose (n = 7/group). DARA-IRDye800 was administered for subsequent in vivo and ex vivo imaging in both cohorts of mice.

RESULTS

DARA-IRDye800 maintained stability and had high affinity for CD38 (K_D = 3.5 ± 0.05 nM). DARA-IRDye800 demonstrated a 5- and 18-fold increase in contrast in tumor-bearing regions of mice with extra- and intramedullary MM. Finally, mice treated with therapeutic doses of DARA and imaged with DARA-IRDye800 showed an 11-fold decrease in fluorescence intensities in vivo compared with untreated controls.

CONCLUSIONS

Our studies establish DARA-IRDye800 as a promising contrast agent for preclinical evaluation of CD38 expression and for further investigating myeloma engraftment and kinetics in relation to anti-CD38 therapies.

CD38: targeted therapy in multiple myeloma and therapeutic potential for solid cancers

INTRODUCTION

CD38 is expressed by some cells of hematological malignancies and tumor-related immunosuppressive cells, including regulatory T cells, regulatory B cells, and myeloid-derived suppressor cells. CD38 is an effective target in some hematological malignancies such as multiple myeloma (MM). Daratumumab (Dara), a CD38-targeting antibody, can eliminate CD38^high immune suppressor cells and is regarded as a standard therapy for MM because of its outstanding clinical efficacy. Other CD38 monospecific antibodies, such as isatuximab, MOR202, and TAK079, showed promising effects in clinical trials.

AREA COVERED

This review examines the expression, function, and targeting of CD38 in MM and its potential to deplete immunosuppressive cells in solid cancers. We summarize the distribution and biological function of CD38 and discuss the application of anti-CD38 drugs in hematological malignancies. We also analyz the role of CD38⁺ immune cells in the tumor microenvironment to encourage additional investigations that target CD38 in solid cancers. PubMed and ClinicalTrials were searched to identify relevant literature from the database inception to 30 April 2020.

EXPERT OPINION

There is convincing evidence that CD38-targeted immunotherapeutics reduce CD38⁺ immune suppressor cells. This result suggests that CD38 can be exploited to treat solid tumors by regulating the immunosuppressive microenvironment.

Therapeutic applications of the selective high affinity ligand drug SH7139 extend beyond non-Hodgkin's lymphoma to many other types of solid cancers

SH7139, the first of a series of selective high affinity ligand (SHAL) oncology drug candidates designed to target and bind to the HLA-DR proteins overexpressed by B-cell lymphomas, has demonstrated exceptional efficacy in the treatment of Burkitt lymphoma xenografts in mice and a safety profile that may prove to be unprecedented for an oncology drug. The aim of this study was to determine how frequently the HLA-DRs targeted by SH7139 are expressed by different subtypes of non-Hodgkin’s lymphoma and by other solid cancers that have been reported to express HLA-DR. Binding studies conducted with SH7129, a biotinylated analog of SH7139, reveal that more than half of the biopsy sections obtained from patients with different types of non-Hodgkin’s lymphoma express the HLA-DRs targeted by SH7139. Similar analyses of tumor biopsy tissue obtained from patients diagnosed with eighteen other solid cancers show the majority of these tumors also express the HLA-DRs targeted by SH7139. Cervical, ovarian, colorectal and prostate cancers expressed the most HLA-DR. Only a few esophageal and head and neck tumors bound the diagnostic. Within an individual’s tumor, cell to cell differences in HLA-DR target expression varied by only 2 to 3-fold while the expression levels in tumors obtained from different patients varied as much as 10 to 100-fold. The high frequency with which SH7129 was observed to bind to these cancers suggests that many patients diagnosed with B-cell lymphomas, myelomas, and other non-hematological cancers should be considered potential candidates for new therapies such as SH7139 that target HLA-DR-expressing tumors.

CD38 as an immunomodulator in cancer

CD38 is a transmembrane glycoprotein that is widely expressed in a variety of human tissues and cells, especially those in the immune system. CD38 protein was previously considered as a cell activation marker, and today monoclonal antibodies targeting CD38 have witnessed great achievements in multiple myeloma and promoted researchers to conduct research on other tumors. In this review, we provide a wide-ranging review of the biology and function of the human molecule outside the field of myeloma. We focus mainly on current research findings to summarize and update the findings gathered from diverse areas of study. Based on these findings, we attempt to extend the role of CD38 in the context of therapy of solid tumors and expand the role of the molecule from a simple marker to an immunomodulator.

Glycosylation-dependent opsonophagocytic activity of staphylococcal protein A antibodies

All currently licensed antibodies against bacteria target exotoxins. For most pathogens, neutralization of toxin(s) is not sufficient to prevent bacterial replication. Antibodies against surface determinants represent better candidates to enhance opsonophagocytic killing, but the mechanisms of action of such antibodies have not been systematically studied. Staphylococcal protein A is a conserved surface protein of Staphylococcus aureus and a crucial virulence determinant that manipulates B-cell responses and blocks deposition of opsonin. Monoclonal antibodies directed against SpA represent potential therapeutic agents as well as a formidable tool to identify and optimize effector functions of antibodies that can promote bacterial clearance.

Antibodies may bind to bacterial pathogens or their toxins to control infections, and their effector activity is mediated through the recruitment of complement component C1q or the engagement with Fcγ receptors (FcγRs). For bacterial pathogens that rely on a single toxin to cause disease, immunity correlates with toxin neutralization. Most other bacterial pathogens, including Staphylococcus aureus, secrete numerous toxins and evolved multiple mechanisms to escape opsonization and complement killing. Several vaccine candidates targeting defined surface antigens of S. aureus have failed to meet clinical endpoints. It is unclear that such failures can be solely attributed to the poor selection of antibody targets. Thus far, studies to delineate antibody-mediated uptake and killing of Gram-positive pathogens remain extremely limited. Here, we exploit 3F6-hIgG1, a human monoclonal antibody that binds and neutralizes the abundant surface-exposed Staphylococcal protein A (SpA). We find that galactosylation of 3F6-hIgG1 that favors C1q recruitment is indispensable for opsonophagocytic killing of staphylococci and for protection against bloodstream infection in animals. However, the simple removal of fucosyl residues, which results in reduced C1q binding and increased engagement with FcγR, maintains the opsonophagocytic killing and protective attributes of the antibody. We confirm these results by engineering 3F6-hIgG1 variants with biased binding toward C1q or FcγRs. While the therapeutic benefit of monoclonal antibodies against infectious disease agents may be debatable, the functional characterization of such antibodies represents a powerful tool for the development of correlates of protection that may guide future vaccine trials.

Isatuximab Acts Through Fc-Dependent, Independent, and Direct Pathways to Kill Multiple Myeloma Cells

Isatuximab is a monoclonal antibody targeting the transmembrane receptor and ectoenzyme CD38, a protein highly expressed on hematological malignant cells, including those in multiple myeloma (MM). Upon binding to CD38-expressing MM cells, isatuximab is thought to induce tumor cell killing via fragment crystallizable (Fc)-dependent mechanisms, including antibody-dependent cellular cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), and complement-dependent cytotoxicity (CDC), as well as via direct Fc-independent mechanisms. Here, these mechanisms of action were investigated in MM and diffuse large B-cell lymphoma (DLBCL) cell lines, as well as in peripheral blood mononuclear cells derived from healthy donors, and in MM patient-derived samples. Our findings show that isatuximab-mediated cytotoxicity occurred primarily via ADCC and ADCP in MM cell lines and via ADCC and apoptosis in DLBCL cell lines expressing high levels of CD38. We identified the programmed cell death-1/programmed cell death-ligand 1 (PD-1/PD-L1) pathway and MM cell-secreted transforming growth factor-beta (TGF-β) as tumor cell-related features that could suppress CD38-mediated ADCC. Furthermore, we established that isatuximab can directly activate natural killer (NK) cells and promote NK cell-mediated cytotoxicity via crosslinking of CD38 and CD16. Finally, isatuximab-induced CDC was observed in cell lines with high CD38 receptor density (>250,000 molecules/cell) and limited expression of inhibitory complement regulatory proteins (CD46, CD55, and CD59; <50,000 molecules/cell). Taken together, our findings highlight mechanistic insights for isatuximab and provide support for a range of combination therapy approaches that could be tested for isatuximab in the future.

Advancements in nanotechnology for the diagnosis and treatment of multiple myeloma

Multiple myeloma (MM), known as a tumor of plasma cells, is not only refractory but also has a high relapse rate, and is the second-most common hematologic tumor after lymphoma. It is often accompanied by multiple osteolytic damage, hypercalcemia, anemia, and renal insufficiency. In terms of diagnosis, conventional detection methods have many limitations, such as it is invasive and time-consuming and has low accuracy. Measures to change these limitations are urgently needed. At the therapeutic level, although the survival of MM continues to prolong with the advent of new drugs, MM remains incurable and has a high recurrence rate. With the development of nanotechnology, nanomedicine has become a powerful way to improve the current diagnosis and treatment of MM. In this review, the research progress and breakthroughs of nanomedicine in MM will be presented. Meanwhile, both superiorities and challenges of nanomedicine were discussed. As a new idea for the diagnosis and treatments of MM, nanomedicine will play a very important role in the research field of MM.

High CD38 expression in childhood T-cell acute lymphoblastic leukemia is not associated with prognosis

BACKGROUND

Prognostic factors are not well exploited in childhood T-cell acute lymphoblastic leukemia (T-ALL).

OBJECTIVE

The aim of this study was to analyze the prognostic role of CD38 as well as minimal residual disease (MRD) and other biological factors in T-ALL.

METHODS

Immunophenotyping of bone marrow (BM) at diagnosis and MRD levels were determined using a standard panel of antibodies by 4-colour flow cytometry. A total of 96 children with T-ALL were enrolled.

RESULTS

The results showed that 97.9% of T-ALL patients were positive for CD38 with a median level of 85.3%. CD38-high group had a worse early treatment response than the CD38-low group. However, CD38 levels were not associated with prognosis, albeit CD38-high group had a worse 5-year event free survival rate (55.1% vs. 66.6%, P> 0.05) and a higher 5-year cumulative incidence of relapse (35.6% vs. 19.8%, P> 0.05). Very high MRD levels (> 10%) were related to the worse survival. Neither flow cytometry based minimal residual disease (MRD) levels nor CD38 expression levels showed significant relation to the hazard of relapse (P> 0.05).

CONCLUSIONS

We conclude that T-ALL has a high level of CD38 expression which is not associated with prognosis. Very high MRD level (> 10%) is related to the worse survival, however, FCM based MRD detection does not convey a significant prognostic value.

Early M-Protein Dynamics Predicts Progression-Free Survival in Patients With Relapsed/Refractory Multiple Myeloma

This study aimed to predict long‐term progression‐free survival (PFS) using early M‐protein dynamic measurements in patients with relapsed/refractory multiple myeloma (MM). The PFS was modeled based on dynamic M‐protein data from two phase III studies, POLLUX and CASTOR, which included 569 and 498 patients with relapsed/refractory MM, respectively. Both studies compared active controls (lenalidomide and dexamethasone, and bortezomib and dexamethasone, respectively) alone vs. in combination with daratumumab. Three M‐protein dynamic features from the longitudinal M‐protein data were evaluated up to different time cutoffs (1, 2, 3, and 6 months). The abilities of early M‐protein dynamic measurements to predict the PFS were evaluated using Cox proportional hazards survival models. Both univariate and multivariable analyses suggest that maximum reduction of M‐protein (i.e., depth of response) was the most predictive of PFS. Despite the statistical significance, the baseline covariates provided very limited predictive value regarding the treatment effect of daratumumab. However, M‐protein dynamic features obtained within the first 2 months reasonably predicted PFS and the associated treatment effect of daratumumab. Specifically, the areas under the time‐varying receiver operating characteristic curves for the model with the first 2 months of M‐protein dynamic data were ~ 0.8 and 0.85 for POLLUX and CASTOR, respectively. Early M‐protein data within the first 2 months can provide a prospective and reasonable prediction of future long‐term clinical benefit for patients with MM.

Daudi cell stroma: An alternative to dithiothreitol to resolve daratumumab interference in pretransfusion testing

Treatment of red blood cells with dithiothreitol (DTT) or trypsin effectively denatures CD38; however, this treatment damages other antigens, some of which are of clinical importance. Thus, other avenues to deplete daratumumab (DARA) from plasma samples should be explored.

STUDY DESIGN AND METHODS

The Daudi B-cell line was found to express high levels of CD38 and was sonicated in a sonication buffer to achieve complete cell lysis. The resulting stroma preparation was centrifuged at 20 000g for 20 minutes and then mixed with 250 μL of DARA-plasma and incubated for 10 minutes at 37°C. The stroma-DARA-plasma mixture was centrifuged again, and the supernatant was collected and subjected to four additional rounds of adsorption with fresh stroma. DARA-depleted plasma was tested by gel indirect antiglobulin test (IAT).

RESULTS

CD38 expression on Daudi cells was confirmed by flow cytometry. Gel IAT analysis showed that the incubation of plasma from DARA-treated patients with Daudi cells stroma resulted in a significant depletion of DARA but allowing detection of other alloantibodies of interest such as anti-K, anti-Yt^a , and anti-Gy^a .

CONCLUSIONS

Daudi cell stroma is inexpensive, easy to prepare in large batches, and can be used as an off-the-shelf reagent. Incubation of plasma from DARA-treated patients with Daudi cell stroma can efficiently overcome DARA interference in serologic testing without affecting DTT- or trypsin-sensitive antigens.

Daratumumab monotherapy for patients with intermediate-risk or high-risk smoldering multiple myeloma: a randomized, open-label, multicenter, phase 2 study (CENTAURUS)

Current guidelines for smoldering multiple myeloma (SMM) recommend active monitoring until the onset of multiple myeloma (MM) before initiating treatment or enrollment in a clinical trial. Earlier intervention may delay progression to MM. In CENTAURUS, 123 patients with intermediate-risk or high-risk SMM were randomly assigned to daratumumab 16 mg/kg intravenously on extended intense (intense), extended intermediate (intermediate), or short dosing schedules. At the prespecified primary analysis (15.8-month median follow-up), the complete response (CR) rates (co-primary endpoint) were 2.4%, 4.9%, and 0% for intense, intermediate, and short dosing, respectively; the co-primary endpoint of CR rate >15% was not met. Progressive disease (PD)/death rates (number of patients who progressed or died divided by total duration of progression-free survival [PFS] in patient-years; co-primary endpoint) for intense, intermediate, and short dosing were 0.055 (80% confidence interval [CI], 0.014-0.096), 0.102 (80% CI, 0.044-0.160), and 0.206 (80% CI, 0.118-0.295), respectively, translating to a median PFS ≥24 months in all arms (P < 0.0001, <0.0001, and =0.0213, respectively). With longer follow-up (median follow-up, 25.9 months), CR rates were 4.9%, 9.8%, and 0% for intense, intermediate, and short dosing, respectively. PD/death rates for intense, intermediate, and short dosing were 0.059 (80% CI, 0.025-0.092), 0.107 (80% CI, 0.058-0.155), and 0.150 (80% CI, 0.089-0.211), respectively, again translating to a median PFS ≥ 24 months in all arms (P < 0.0001 for all arms). Twenty-four-month PFS rates were 89.9% (90% CI, 78.5-95.4%), 82.0% (90% CI, 69.0-89.9%), and 75.3% (90% CI, 61.1-85.0%) for intense, intermediate, and short dosing, respectively. Pharmacokinetic analyses indicated that intense dosing maintained target-saturating trough concentrations in most patients throughout weekly, every-2-week, and every-4-week dosing periods. No new safety signals were observed. These data provide the basis for an ongoing phase 3 study of daratumumab in SMM.

Role of the Bone Marrow Milieu in Multiple Myeloma Progression and Therapeutic Resistance

Multiple myeloma (MM) is a cancer of the plasma cells within the bone marrow (BM). Studies have shown that the cellular and noncellular components of the BM milieu, such as cytokines and exosomes, play an integral role in MM pathogenesis and progression by mediating drug resistance and inducing MM proliferation. Moreover, the BM microenvironment of patients with MM facilitates cancer tolerance and immune evasion through the expansion of regulatory immune cells, inhibition of antitumor effector cells, and disruption of the antigen presentation machinery. These are of special relevance, especially in the current era of cancer immunotherapy. An improved understanding of the supportive role of the MM BM microenvironment will allow for the development of future therapies targeting MM in the context of the BM milieu to elicit deeper and more durable responses. In the present review, we have discussed our current understanding of the role of the BM microenvironment in MM progression and resistance to therapy and discuss novel potential approaches to alter its pro-MM function.

Results of an Early Access Treatment Protocol of Daratumumab Monotherapy in Spanish Patients With Relapsed or Refractory Multiple Myeloma

Daratumumab is a human CD38-targeted monoclonal antibody approved as monotherapy for heavily pretreated relapsed and refractory multiple myeloma. We report findings for the Spanish cohort of an open-label treatment protocol that provided early access to daratumumab monotherapy and collected safety and patient-reported outcomes data for patients with relapsed or refractory multiple myeloma. At 15 centers across Spain, intravenous daratumumab (16 mg/kg) was administered to 73 patients who had ≥3 prior lines of therapy, including a proteasome inhibitor and an immunomodulatory drug, or who were double refractory to both. The median duration of daratumumab treatment was 3.3 (range: 0.03-13.17) months, with a median number of 12 (range: 1-25) infusions. Grade 3/4 treatment-emergent adverse events were reported in 74% of patients and included lymphopenia (28.8%), thrombocytopenia (27.4%), neutropenia (21.9%), leukopenia (19.2%), and anemia (15.1%). Common (>5%) serious treatment-emergent adverse events included respiratory tract infection (9.6%), general physical health deterioration (6.8%), and back pain (5.5%). Infusion-related reactions occurred in 45% of patients. The median change from baseline in all domains of the EQ-5D-5L and EORTC QLQ-C30 was mostly 0. A total of 18 (24.7%) patients achieved a partial response or better, with 10 (13.7%) patients achieving a very good partial response or better. Median progression-free survival was 3.98 months. The results of this early access treatment protocol are consistent with previously reported trials of daratumumab monotherapy and confirm its safety and antitumoral efficacy in Spanish patients with heavily treated relapsed or refractory multiple myeloma. European Clinical Trials Database number: 2015-002993-19.

Upregulation of CD38 expression on multiple myeloma cells by novel HDAC6 inhibitors is a class effect and augments the efficacy of daratumumab

Multiple myeloma (MM) is incurable, so there is a significant unmet need for effective therapy for patients with relapsed or refractory disease. This situation has not changed despite the recent approval of the anti-CD38 antibody daratumumab, one of the most potent agents in MM treatment. The efficiency of daratumumab might be improved by combining it with synergistic anti-MM agents. We therefore investigated the potential of the histone deacetylase (HDAC) inhibitor ricolinostat to up-regulate CD38 on MM cells, thereby enhancing the performance of CD38-specific therapies. Using quantitative reverse transcription polymerase chain reaction and flow cytometry, we observed that ricolinostat significantly increases CD38 RNA levels and CD38 surface expression on MM cells. Super-resolution microscopy imaging of MM cells by direct stochastic optical reconstruction microscopy confirmed this rise with molecular resolution and revealed homogeneous distribution of CD38 molecules on the cell membrane. Particularly important is that combining ricolinostat with daratumumab induced enhanced lysis of MM cells. We also evaluated next-generation HDAC6 inhibitors (ACY-241, WT-161) and observed similar increase of CD38 levels suggesting that the upregulation of CD38 expression on MM cells by HDAC6 inhibitors is a class effect. This proof-of-concept illustrates the potential benefit of combining HDAC6 inhibitors and CD38-directed immunotherapy for MM treatment.

Resistance Mechanisms Towards CD38-Directed Antibody Therapy in Multiple Myeloma

Antibodies targeting CD38 are rapidly changing the treatment landscape of multiple myeloma (MM). CD38-directed antibodies have several mechanisms of action. Fc-dependent immune effector mechanisms include complement-dependent cytotoxicity (CDC), antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP) and apoptosis. In addition, direct effects and immunomodulatory effects contribute to the efficacy of CD38-directed antibodies. Daratumumab, the first-in-class anti-CD38 monoclonal antibody, is now part of standard treatment regimens of both newly diagnosed as well as relapsed/refractory MM patients. The FDA has recently approved isatuximab in combination with pomalidomide and dexamethasone for relapsed/refractory MM patients after at least two prior therapies. Further, the other CD38-targeting antibodies (i.e., MOR202 and TAK-079) are increasingly used in clinical trials. The shift to front-line treatment of daratumumab will lead to an increase in patients refractory to CD38 antibody therapy already after first-line treatment. Therefore, it is important to gain insight into the mechanisms of resistance to CD38-targeting antibodies in MM, and to develop strategies to overcome this resistance. In the current review, we will briefly describe the most important clinical data and mechanisms of action and will focus in depth on the current knowledge on mechanisms of resistance to CD38-targeting antibodies and potential strategies to overcome this.

ImmunoPET: Concept, Design, and Applications

Immuno-positron emission tomography (immunoPET) is a paradigm-shifting molecular imaging modality combining the superior targeting specificity of monoclonal antibody (mAb) and the inherent sensitivity of PET technique. A variety of radionuclides and mAbs have been exploited to develop immunoPET probes, which has been driven by the development and optimization of radiochemistry and conjugation strategies. In addition, tumor-targeting vectors with a short circulation time (e.g., Nanobody) or with an enhanced binding affinity (e.g., bispecific antibody) are being used to design novel immunoPET probes. Accordingly, several immunoPET probes, such as 89Zr-Df-pertuzumab and 89Zr-atezolizumab, have been successfully translated for clinical use. By noninvasively and dynamically revealing the expression of heterogeneous tumor antigens, immunoPET imaging is gradually changing the theranostic landscape of several types of malignancies. ImmunoPET is the method of choice for imaging specific tumor markers, immune cells, immune checkpoints, and inflammatory processes. Furthermore, the integration of immunoPET imaging in antibody drug development is of substantial significance because it provides pivotal information regarding antibody targeting abilities and distribution profiles. Herein, we present the latest immunoPET imaging strategies and their preclinical and clinical applications. We also emphasize current conjugation strategies that can be leveraged to develop next-generation immunoPET probes. Lastly, we discuss practical considerations to tune the development and translation of immunoPET imaging strategies.

Split First Dose Administration of Intravenous Daratumumab for the Treatment of Multiple Myeloma (MM): Clinical and Population Pharmacokinetic Analyses

Introduction

Daratumumab, a human immunoglobulin Gκ monoclonal antibody targeting CD38, is approved as monotherapy and in combination with standard-of-care regimens for multiple myeloma. In clinical studies, the median durations of the first, second, and subsequent intravenous infusions of daratumumab were 7.0, 4.3, and 3.4 h, respectively. Splitting the first intravenous infusion of daratumumab over 2 days is an approved alternative dosing regimen to reduce the duration of the first infusion and provide flexibility for patients and healthcare providers.

Methods

The feasibility of splitting the first 16-mg/kg infusion into two separate infusions of 8 mg/kg on Days 1 and 2 of the first treatment cycle was investigated in two cohorts [daratumumab, carfilzomib, and dexamethasone (D-Kd) and daratumumab, carfilzomib, lenalidomide, and dexamethasone (D-KRd)] of the phase 1b MMY1001 study. Additionally, a population pharmacokinetic (PK) analysis and simulations were used to compare the PK profiles of the split first dose regimen with the recommended single first dose regimens of daratumumab in previously approved indications.

Results

In MMY1001, following administration of the second half of a split first dose on Cycle 1 Day 2, postinfusion median (range) daratumumab concentrations were similar between split first dose [D-Kd, 254.9 (125.8–435.5) µg/ml; D-KRd, 277.2 (164.0–341.8) µg/ml; combined, 256.8 (125.8–435.5) µg/ml] and single first dose [D-Kd, 319.2 (237.5–394.7) µg/ml]. At the end of weekly dosing, median (range) Cycle 3 Day 1 preinfusion daratumumab concentrations were similar between split first dose [D-Kd, 663.9 (57.7–1110.7) µg/ml; D-KRd, 575.1 (237.9–825.5) µg/ml; combined, 639.2 (57.7–1110.7) µg/ml] and single first dose [D-Kd, 463.2 (355.9–792.9) µg/ml]. The population PK simulations demonstrated virtually identical PK profiles after the first day of treatment for all approved indications and recommended dosing schedules of daratumumab.

Conclusion

These data support the use of an alternative split first dose regimen of intravenous daratumumab for the treatment of MM.

Trial Registration

ClinicalTrials.gov number, NCT01998971.

Electronic Supplementary Material

The online version of this article (10.1007/s12325-020-01247-8) contains supplementary material, which is available to authorized users.

Monoclonal antibodies in the treatment of AL amyloidosis: co-targetting the plasma cell clone and amyloid deposits

Immunoglobulin light-chain amyloidosis (AL amyloidosis) is a rare disease in which a small plasma cell clone produces toxic misfolded proteins that deposit in organs and impair their function. Currently, the only available treatment approach is the elimination of clonal plasma cells. However, a rapid strike that halts and possibly reverses organ damage is crucial. The development of agents that facilitate the clearance of pathological fibrillar deposits, therefore reducing the frailty of patients, is the needed supplement to plasma cell-directed therapy. Monoclonal antibodies provide therapy against malignant plasma cells (daratumumab, isatuximab, elotuzumab) but they are also able to target and eliminate the amyloid from organs (NEOD001, CAEL-101, dezamizumab). From the plasma cell-directed group, daratumumab in monotherapy has proved to be extremely efficient in relapsed AL amyloidosis, exceeding its results in multiple myeloma. Compared to other agents, monoclonal antibodies possess the advantage of high selectivity and low toxicity and could potentially become future game-changers in this field. Co-targetting of the plasma cell clone and amyloid deposits shall together be translated in the revolutionary improved outcome of potentially curable AL amyloidosis.

Tumor immune microenvironment in head and neck cancers

Head and neck cancers are a heterogeneous group of tumors that are highly aggressive and collectively represent the sixth most common cancer worldwide. Ninety percent of head and neck cancers are squamous cell carcinomas (HNSCCs). The tumor microenvironment (TME) of HNSCCs consists of many different subsets of cells that infiltrate the tumors and interact with the tumor cells or with each other through various networks. Both innate and adaptive immune cells play a crucial role in mediating immune surveillance and controlling tumor growth. Here, we discuss the different subsets of immune cells and how they contribute to an immunosuppressive TME of HNSCCs. We also briefly summarize recent advances in immunotherapeutic approaches for HNSCC treatment. A better understanding of the multiple factors that play pivotal roles in HNSCC tumorigenesis and tumor progression may help define novel targets to develop more effective immunotherapies for patients with HNSCC.

Nanobody-based CD38-specific heavy chain antibodies induce killing of multiple myeloma and other hematological malignancies

Rationale: CD38 is a target for the therapy of multiple myeloma (MM) with monoclonal antibodies such as daratumumab and isatuximab. Since MM patients exhibit a high rate of relapse, the development of new biologics targeting alternative CD38 epitopes is desirable. The discovery of single-domain antibodies (nanobodies) has opened the way for a new generation of antitumor therapeutics. We report the generation of nanobody-based humanized IgG1 heavy chain antibodies (hcAbs) with a high specificity and affinity that recognize three different and non-overlapping epitopes of CD38 and compare their cytotoxicity against CD38-expressing hematological cancer cells in vitro, ex vivo and in vivo. Methods: We generated three humanized hcAbs (WF211-hcAb, MU1067-hcAb, JK36-hcAb) that recognize three different non-overlapping epitopes (E1, E2, E3) of CD38 by fusion of llama-derived nanobodies to the hinge- and Fc-domains of human IgG1. WF211-hcAb shares the binding epitope E1 with daratumumab. We compared the capacity of these CD38-specific hcAbs and daratumumab to induce CDC and ADCC in CD38-expressing tumor cell lines in vitro and in patient MM cells ex vivo as well as effects on xenograft tumor growth and survival in vivo. Results: CD38-specific heavy chain antibodies (WF211-hcAb, MU1067-hcAb, JK36-hcAb) potently induced antibody-dependent cellular cytotoxicity (ADCC) in CD38-expressing tumor cell lines and in primary patient MM cells, but only little if any complement-dependent cytotoxicity (CDC). In vivo, CD38-specific heavy chain antibodies significantly reduced the growth of systemic lymphomas and prolonged survival of tumor bearing SCID mice. Conclusions: CD38-specific nanobody-based humanized IgG1 heavy chain antibodies mediate cytotoxicity against CD38-expressing hematological cancer cells in vitro, ex vivo and in vivo. These promising results of our study indicate that CD38-specific hcAbs warrant further clinical development as therapeutics for multiple myeloma and other hematological malignancies.

CD38 play roles in T cell-dependent response and B cell differentiation in nile tilapia (Oreochromis niloticus)

CD38 is a multifunctional cell surface molecule that plays a crucial role in B cell activation, differentiation, and maturation in mammals with an increased expression in B cell maturation. In this study, a CD38-like molecule (OnCD38) was cloned and identified from Nile tilapia (Oreochromis niloticus), and its functional characterization was investigated. The open reading frame of OnCD38 is 828 bp of the nucleotide sequence, encoding a polypeptide of 275 amino acids. The deduced amino acid sequence of OnCD38 is highly homologous to other teleost fish and similar to mammals, containing extracellular, intracellular and transmembrane regions. Subcellular localization studies revealed that OnCD38 molecules were presented on the surface of B cells. Three healthy tilapia were used in each experimental group and control group. Following keyhole limpet hemocyanin (KLH) challenge in vivo, the mRNA expression of OnCD38 was significantly up-regulated in peripheral blood, spleen, and head kidney, with an earlier up-regulation in the second challenge than the first one. The up-regulation of OnCD38 expression was also detected in head kidney leukocytes after stimulation with LPS, recombinant HomoIL-10 ((r)HomoIL-10), (r)OnIL-10, and LPS plus (r)OnIL-10 in vitro. Furthermore, the OnCD38 expression increased with the differentiation of B cells, reaching a high level (10.1 fold higher than resting mature B cells) at the plasma-like B cells. Taken together, in this study, these results indicate that the OnCD38 is likely involved in the T cell-dependent response and plays roles in B cell differentiation in Nile tilapia.

Mechanisms of Resistance to Anti-CD38 Daratumumab in Multiple Myeloma

Daratumumab (Dara) is the first-in-class human-specific anti-CD38 mAb approved for the treatment of multiple myeloma (MM). Although recent data have demonstrated very promising results in clinical practice and trials, some patients do not achieve a partial response, and ultimately all patients undergo progression. Dara exerts anti-MM activity via antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), complement-dependent cytotoxicity (CDC), and immunomodulatory effects. Deregulation of these pleiotropic mechanisms may cause development of Dara resistance. Knowledge of this resistance may improve the therapeutic management of MM patients.

[CD38 antibodies in multiple myeloma]

The high CD38 expression by plasma cells together with the biological functions of CD38 resulted in the development of CD38 antibodies for the treatment of multiple myeloma (MM) patients. The cytolytic activity of CD38 antibodies is mediated by complement-dependent cytoxicity (CDC), antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), direct cell death effects and immunomodulatory effects. CD38 antibodies have demonstrated their clinical benefit as single agent or in combination for the treatment of multiple myeloma patients and will contribute to further improvement in the outcome of MM patients.

The Roles of CD38 and CD157 in the Solid Tumor Microenvironment and Cancer Immunotherapy

The tumor microenvironment (TME) consists of extracellular matrix proteins, immune cells, vascular cells, lymphatics and fibroblasts. Under normal physiological conditions, tissue homeostasis protects against tumor development. However, under pathological conditions, interplay between the tumor and its microenvironment can promote tumor initiation, growth and metastasis. Immune cells within the TME have an important role in the formation, growth and metastasis of tumors, and in the responsiveness of these tumors to immunotherapy. Recent breakthroughs in the field of cancer immunotherapy have further highlighted the potential of targeting TME elements, including these immune cells, to improve the efficacy of cancer prognostics and immunotherapy. CD38 and CD157 are glycoproteins that contribute to the tumorigenic properties of the TME. For example, in the hypoxic TME, the enzymatic functions of CD38 result in an immunosuppressive environment. This leads to increased immune resistance in tumor cells and allows faster growth and proliferation rates. CD157 may also aid the production of an immunosuppressive TME, and confers increased malignancy to tumor cells through the promotion of tumor invasion and metastasis. An improved understanding of CD38 and CD157 in the TME, and how these glycoproteins affect cancer progression, will be useful to develop both cancer prognosis and treatment methods. This review aims to discuss the roles of CD38 and CD157 in the TME and cancer immunotherapy of a range of solid tumor types.

212Pb α-Radioimmunotherapy Targeting CD38 in Multiple Myeloma: A Preclinical Study

Multiple myeloma (MM) is a plasma cell cancer and represents the second most frequent hematologic malignancy. Despite new treatments and protocols, including high-dose chemotherapy associated with autologous stem cell transplantation, the prognosis of MM patients is still poor. α-radioimmunotherapy (α-RIT) represents an attractive treatment strategy because of the high-linear-energy transfer and short pathlength of α-radiation in tissues, resulting in high tumor cell killing and low toxicity to surrounding tissues. In this study, we investigated the potential of α-RIT with ²¹²Pb-daratumumab (anti-hCD38), in both in vitro and in vivo models, as well as an antimouse CD38 antibody using in vivo models. Methods: Inhibition of cell proliferation after incubation of the RPMI8226 cell line with an increasing activity (0.185-3.7 kBq/mL) of ²¹²Pb-isotypic control or ²¹²Pb-daratumumab was evaluated. Biodistribution was performed in vivo by SPECT/CT imaging and after death. Dose-range-finding and acute toxicity studies were conducted. Because daratumumab does not bind the murine CD38, biodistribution and dose-range finding were also determined using an antimurine CD38 antibody. To evaluate the in vivo efficacy of ²¹²Pb-daratumumab, mice were engrafted subcutaneously with 5 × 10⁶ RPMI8226 cells. Mice were treated 13 d after engraftment with an intravenous injection of ²¹²Pb-daratumumab or control solution. Therapeutic efficacy was monitored by tumor volume measurements and overall survival. Results: Significant inhibition of proliferation of the human myeloma RPMI8226 cell line was observed after 3 d of incubation with ²¹²Pb-daratumumab, compared with ²¹²Pb-isotypic control or cold antibodies. Biodistribution studies showed a specific tumoral accumulation of daratumumab. No toxicity was observed with ²¹²Pb-daratumumab up to 370 kBq because of lack of cross-reactivity. Nevertheless, acute toxicity experiments with ²¹²Pb-anti-mCD38 established a toxic activity of 277.5 kBq. To remain within realistically safe treatment activities for efficacy studies, mice were treated with 185 kBq or 277.5 kBq of ²¹²Pb-daratumumab. Marked tumor growth inhibition compared with controls was observed, with a median survival of 55 d for 277.5 kBq of ²¹²Pb-daratumumab instead of 11 d for phosphate-buffered saline. Conclusion: These results showed ²¹²Pb-daratumumab to have efficacy in xenografted mice, with significant tumor regression and increased survival. This study highlights the potency of α-RIT in MM treatment.

CD38 Expression by Myeloma Cells and Its Role in the Context of Bone Marrow Microenvironment: Modulation by Therapeutic Agents

In the last decades CD38 has emerged as an attractive target for multiple myeloma (MM). CD38 is a novel multifunctional glycoprotein that acts as a receptor, adhesion molecule interacting with CD31 and as an ectoenzyme. As an ectoenzyme, CD38 functions as a metabolic sensor catalyzing the extracellular conversion of NAD+ to the immunosuppressive factor adenosine (ADO). Other ectoenzymes, CD73 and CD203a, together with CD38, are also involved in the alternative axis of extracellular production of ADO, bypassing the canonical pathway mediated by CD39. CD38 is ubiquitously expressed in the bone marrow microenvironment; however, only MM cells display a very high surface density, which lead to the development of several anti-CD38 monoclonal antibodies (mAbs). The efficacy of anti-CD38 mAbs depends from the presence of CD38 on the surface of MM and immune-microenvironment cells. Interestingly, it has been reported that several drugs like lenalidomide, panobinostat, the all-trans retinoic acid and the DNA methyltransferase inhibitors may increase the expression of CD38. Hence, the possibility to modulate CD38 by increasing its expression on MM cells is the pre-requisite to potentiate the clinical efficacy of the anti-CD38 mAbs and to design clinical trials with the combination of anti-CD38 mAbs and these drugs.

Isatuximab plus pomalidomide and low-dose dexamethasone versus pomalidomide and low-dose dexamethasone in patients with relapsed and refractory multiple myeloma (ICARIA-MM): a randomised, multicentre, open-label, phase 3 study

BACKGROUND

Isatuximab is a monoclonal antibody that binds a specific epitope on the human CD38 receptor and has antitumour activity via multiple mechanisms of action. In a previous phase 1b study, around 65% of patients with relapsed and refractory multiple myeloma achieved an overall response with a combination of isatuximab with pomalidomide and low-dose dexamethasone. The aim of this study was to determine the progression-free survival benefit of isatuximab plus pomalidomide and dexamethasone compared with pomalidomide and dexamethasone in patients with relapsed and refractory multiple myeloma.

METHODS

We did a randomised, multicentre, open-label, phase 3 study at 102 hospitals in 24 countries in Europe, North America, and the Asia-Pacific regions. Eligible participants were adult patients with relapsed and refractory multiple myeloma who had received at least two previous lines of treatment, including lenalidomide and a proteasome inhibitor. Patients were excluded if they were refractory to previous treatment with an anti-CD38 monoclonal antibody. We randomly assigned patients (1:1) to either isatuximab 10 mg/kg plus pomalidomide 4 mg plus dexamethasone 40 mg (20 mg for patients aged ≥75 years), or pomalidomide 4 mg plus dexamethasone 40 mg. Randomisation was done using interactive response technology and stratified according to the number of previous lines of treatment (2-3 vs >3) and age (<75 years vs ≥75 years). Treatments were assigned based on a permuted blocked randomisation scheme with a block size of four. The isatuximab-pomalidomide-dexamethasone group received isatuximab intravenously on days 1, 8, 15, and 22 in the first 28-day cycle, then on days 1 and 15 in subsequent cycles. Both groups received oral pomalidomide on days 1 to 21 in each cycle, and oral or intravenous dexamethasone on days 1, 8, 15, and 22 of each cycle. Treatment continued until disease progression, unacceptable toxicity, or consent withdrawal. Dose reductions for adverse reactions were permitted for pomalidomide and dexamethasone, but not for isatuximab. The primary endpoint was progression-free survival, determined by an independent response committee and assessed in the intention-to-treat population. Safety was assessed in all participants who received at least one dose of study drug. This study is registered at ClinicalTrials.gov, number NCT02990338.

FINDINGS

Between Jan 10, 2017, and Feb 2, 2018, we randomly assigned 307 patients to treatment: 154 to isatuximab-pomalidomide-dexamethasone, and 153 to pomalidomide-dexamethasone. At a median follow-up of 11·6 months (IQR 10·1-13·9), median progression-free survival was 11·5 months (95% CI 8·9-13·9) in the isatuximab-pomalidomide-dexamethasone group versus 6·5 months (4·5-8·3) in the pomalidomide-dexamethasone group; hazard ratio 0·596, 95% CI 0·44-0·81; p=0·001 by stratified log-rank test. The most frequent treatment-emergent adverse events (any grade; isatuximab-pomalidomide-dexamethasone vs pomalidomide-dexamethasone) were infusion reactions (56 [38%] vs 0), upper respiratory tract infections (43 [28%] vs 26 [17%]), and diarrhoea (39 [26%] vs 29 [20%]). Adverse events with a fatal outcome were reported in 12 patients (8%) in the isatuximab-pomalidomide-dexamethasone group and 14 (9%) in the pomalidomide-dexamethasone group. Deaths due to treatment-related adverse events were reported for one patient (<1%) in the isatuximab-pomalidomide-dexamethasone group (sepsis) and two (1%) in the pomalidomide-dexamethasone group (pneumonia and urinary tract infection).

INTERPRETATION

The addition of isatuximab to pomalidomide-dexamethasone significantly improves progression-free survival in patients with relapsed and refractory multiple myeloma. Isatuximab is an important new treatment option for the management of relapsed and refractory myeloma, particularly for patients who become refractory to lenalidomide and a proteasome inhibitor.

FUNDING

Sanofi. VIDEO ABSTRACT.