Cell membrane-specific epitopes on CD30: Potentially superior targets for immunotherapy

Novel OX40 and 4-1BB derived spacers enhance CD30 CAR activity and safety in CD30 positive lymphoma models

The chimeric antigen receptor (CAR) derived from the CD30 specific murine antibody, HRS-3, has produced promising clinical efficacy with a favorable safety profile in the treatment of relapsed or refractory CD30-positive lymphomas. However, persistence of the autologous CAR-T cells was brief, and many patients relapsed a year after treatment. The lack of persistence may be attributed to the use of a wild-type immunoglobulin (Ig)G1 spacer that can associate with Fc receptors. We first identified the cysteine-rich domain (CRD) 5 of CD30 as the primary binding epitope of HRS-3 and armed with this insight, attempted to improve the HRS-3 CAR functionality with a panel of novel spacer designs. We demonstrate that HRS-3 CARs with OX40 and 4-1BB derived spacers exhibited similar anti-tumor efficacy, circumvented interactions with Fc receptors, and secreted lower levels of cytokines in vitro than a CAR employing the IgG1 spacer. Humanization of the HRS-3 scFv coupled with the 4-1BB spacer preserved potent on-target, on-tumor efficacy, and on-target, off-tumor safety. In a lymphoma mouse model of high tumor burden, T cells expressing humanized HRS-3 CD30.CARs with the 4-1BB spacer potently killed tumors with low levels of circulating inflammatory cytokines, providing a promising candidate for future clinical development in the treatment of CD30-positive malignancies.

The Opposite Functions of CD30 Ligand Isoforms

TNFSF8/CD30 ligand is a TNF superfamily member expressed on several major immune cell types, including activated monocytes, B, and T cells. The signaling of CD30 ligand through its cognate CD30 receptor has been shown to have effects on cell differentiation, cell death/survival, and cytokine production. The signaling pair has been implicated in hematopoietic malignancies and inflammatory disease, and a chemotherapy-CD30 antibody combination for the treatment of Hodgkin and other lymphomas has been developed. There are two recorded isoforms of CD30 ligand. All hitherto studies of CD30 ligand are of the first, canonical isoform, while the second isoform has never been described. This study aims to elucidate the properties and signaling functions of the second CD30 ligand isoform. We have found mRNA expression of both isoforms in the PBMCs of all six healthy donors tested. Through methods in cell biology and biochemistry, we were able to discover that the second CD30 ligand isoform has no discernable pro-inflammatory function and, in fact, isoform 2 can restrict the capacity of the canonical isoform to signal through the CD30 receptor by preventing their interaction. This discovery has implications for the future development of therapeutics targeting the CD30/CD30 ligand signaling pair in cancer and inflammatory disease.

Enhancing aortic valve drug delivery with PAR2-targeting magnetic nano-cargoes for calcification alleviation

Calcific aortic valve disease is a prevalent cardiovascular disease with no available drugs capable of effectively preventing its progression. Hence, an efficient drug delivery system could serve as a valuable tool in drug screening and potentially enhance therapeutic efficacy. However, due to the rapid blood flow rate associated with aortic valve stenosis and the lack of specific markers, achieving targeted drug delivery for calcific aortic valve disease has proved to be challenging. Here we find that protease-activated-receptor 2 (PAR2) expression is up-regulated on the plasma membrane of osteogenically differentiated valvular interstitial cells. Accordingly, we develop a magnetic nanocarrier functionalized with PAR2-targeting hexapeptide for dual-active targeting drug delivery. We show that the nanocarriers effectively deliver XCT790-an anti-calcification drug-to the calcified aortic valve under extra magnetic field navigation. We demonstrate that the nano-cargoes consequently inhibit the osteogenic differentiation of valvular interstitial cells, and alleviate aortic valve calcification and stenosis in a high-fat diet-fed low-density lipoprotein receptor-deficient (Ldlr-/-) mouse model. This work combining PAR2- and magnetic-targeting presents an effective targeted drug delivery system for treating calcific aortic valve disease in a murine model, promising future clinical translation.

High CAR intensity of expression confers enhanced antitumor effect against lymphoma without functional exhaustion

Identifying factors that ameliorates clinical outcomes following CART therapy represents an unmet need. We hypothesized that CAR expression level would have a significant impact on CART efficacy and tested this with CAR30⁺ T_SCM-LIKE enriched cells. By sorting T-cells according to CAR mean fluorescence intensity in two markedly different populations (CAR^HI and CAR^LO), we showed that a high CAR expression enhances antitumor efficacy in vitro, that is sustained after sequential re-exposures to tumor cells and is not associated with T-cell exhaustion or differentiation. Furthermore, we found a correlation between high surface CAR expression and antitumor effect with CAR19⁺ T-cells, thus validating our findings with CAR30. Definitive proof of CAR^HI T-cells improved antitumor efficacy was demonstrated in a human Hodgkin's lymphoma xenograft mouse model, where CAR30-T_SCM-LIKE enriched products with high intensity of CAR expression achieved superior tumor control in vivo and longer survival than those with a low intensity of CAR expression. Our data suggest that modulation of CAR intensity of expression represents an additional strategy to increase CART therapy clinical efficacy.

Bispecific Antibody-Based Immune-Cell Engagers and Their Emerging Therapeutic Targets in Cancer Immunotherapy

Cancer is the second leading cause of death worldwide after cardiovascular diseases. Harnessing the power of immune cells is a promising strategy to improve the antitumor effect of cancer immunotherapy. Recent progress in recombinant DNA technology and antibody engineering has ushered in a new era of bispecific antibody (bsAb)-based immune-cell engagers (ICEs), including T- and natural-killer-cell engagers. Since the first approval of blinatumomab by the United States Food and Drug Administration (US FDA), various bsAb-based ICEs have been developed for the effective treatment of patients with cancer. Simultaneously, several potential therapeutic targets of bsAb-based ICEs have been identified in various cancers. Therefore, this review focused on not only highlighting the action mechanism, design and structure, and status of bsAb-based ICEs in clinical development and their approval by the US FDA for human malignancy treatment, but also on summarizing the currently known and emerging therapeutic targets in cancer. This review provides insights into practical considerations for developing next-generation ICEs.

Memory stem T cells modified with a redesigned CD30-chimeric antigen receptor show an enhanced antitumor effect in Hodgkin lymphoma

Objectives

Adoptive cell therapy (ACT) with mature T cells modified with a chimeric antigen receptor has demonstrated improved outcome for B‐cell malignancies. However, its application for others such as Hodgkin lymphoma remains a clinical challenge. CD30 antigen, expressed in Hodgkin lymphoma cells, is absent in most healthy tissues, representing an ideal target of ACT for this disease. Despite that, efficacy of CD30‐chimeric antigen receptor (CAR) T cells for Hodgkin lymphoma remains modest. Here, we have developed and tested a novel CD30‐CAR T to improve efficacy of CD30‐CAR therapy, using a targeting epitope within the non‐cleavable part of CD30 receptor, and memory stem T cells (T_SCM) to improve engraftment, persistence and antitumor activity.

Methods

T_SCM‐like cultures were generated and expanded ex vivo and transduced at day 1 or 2 with a lentiviral vector encoding the CD30‐CAR. Therapeutic in vivo experiments were performed using NSG mice injected with L540 (sc) or L428 (iv) and treated with CD30‐CAR T cells when the tumor was established.

Results

CD30‐CAR T_SCM‐like cells generated and expanded ex vivo, despite CD30 expression and fratricide killing of CD30⁺ CAR T cells, were not impaired by soluble CD30 and completely eradicated Hodgkin lymphoma in vivo, showing high persistence and long‐lasting immunity. In addition, highly enriched CD30‐CAR T_SCM‐like products confer a survival advantage in vivo, in contrast to more differentiated CAR T cells, with higher tumor infiltration and enhanced antitumor effect.

Conclusion

This study supports the use of a refined CD30‐CAR T cells with highly enriched T_SCM‐like products to improve clinical efficacy of CAR T for Hodgkin lymphoma.

The potential of brentuximab vedotin, alone or in combination with current clinical therapies, in the treatment of testicular germ cell tumors

Testicular germ cell tumors (TGCTs) are the commonest tumors in young men. With the advancement of chemotherapies, most TGCTs are successfully cured, even when diagnosed at an advanced and metastatic stage. However, a proportion of often young patients, median age 35-40, with advanced disease are not cured and will inevitably die. Therefore, there is an unmet need in this small population of young patients who are candidates for experimental approaches. We investigated a new therapeutic option for this group of patients, aiming to significantly improve their outcome. In recent years, many targeted therapies have been developed which demonstrated high efficacy and low toxicity. Brentuximab vedotin, a monomethyl auristatin E conjugated CD30 antibody, targets CD30 to kill cancer cells. As a large proportion of TGCTs express CD30, in particular embryonal carcinomas, we investigated in vitro the efficacy of brentuximab vedotin in treating TGCTs as a single therapy and in combination with commonly used chemotherapy drugs. We determined CD30 expression levels in 12 TGCT cell lines, including three cisplatin resistant sublines. In general, the efficiency of cancer cell inhibition by brentuximab vedotin correlates with CD30 expression, but there were some exceptions. We also determined the efficacy of brentuximab vedotin in combination with commonly used chemotherapy drugs and found synergistic/additive effects with etoposide, paclitaxel and SN-38. However, cisplatin, the most commonly used chemotherapy drug in TGCT treatment, exhibited antagonism and we showed that cisplatin selectively kills CD30 positive cells. We also found that certain agents, which have been reported to induce CD30 expression in other human malignant diseases, including DNA demethylation drugs, methotrexate and CD30 ligands, were unable to enhance CD30 expression or brentuximab vedotin efficacy in TGCT cells. This study will help to design clinical trials using brentuximab vedotin for the treatment of TGCTs, either as a single agent or in combination with current clinical therapies.

Understanding CD30 biology and therapeutic targeting: a historical perspective providing insight into future directions

CD30 is a member of the tumor necrosis factor receptor superfamily. It is characteristically expressed in certain hematopoietic malignancies, including anaplastic large cell lymphoma and Hodgkin lymphoma, among others. The variable expression of CD30 on both normal and malignant lymphoid cells has focused research efforts on understanding the pathogenesis of CD30 upregulation, its contribution to lymphomagenesis through anti-apoptotic mechanisms, and its effect on cell survival. Given the restriction of CD30 to certain tumor types, the logical extension of this has been to attempt to exploit it as a therapeutic target. The efficacy of naked anti-CD30 antibodies in practice was, however, modest. Moreover, combinations with bacterial toxins and radioimmunoconjugates have also had limited success. The development of the antibody-drug compound brentuximab vedotin (BV), however, has rejuvenated interest in CD30 as a tumor target. Phase I and II clinical trials in Hodgkin lymphoma, peripheral T-cell lymphoma, cutaneous T cell lymphoma, and even CD30-expressing B-cell lymphomas, have shown the compound is well tolerated, but more importantly, able to deliver meaningful disease control even in patients with multiply relapsed or refractory disease. FDA approval has been granted for its use in relapsed Hodgkin lymphoma and systemic anaplastic large cell lymphoma. A recent phase III trial of BV in cutaneous T-cell lymphoma has confirmed its superiority to standard of care therapies. In this manuscript, we explore the history of CD30 as a tumor marker and as a therapeutic target, both in the laboratory and in the clinic, with a view to understanding future avenues for further study.

Vorinostat downregulates CD30 and decreases brentuximab vedotin efficacy in human lymphocytes

With an increasing number of clinical trials looking at combination therapies in cancer, potential drug-drug interactions require particular attention. One such instance is the treatment of CD30(+) tumors after previous vorinostat (SAHA; suberoylanilide hydroxyamic acid) failure with the anti-CD30 antibody-drug conjugate brentuximab vedotin. Using B-, T-, and natural killer (NK)-cell lines in vitro, we demonstrate that SAHA downregulates the expression of CD30 and lowers the efficacy of subsequent brentuximab vedotin treatment if baseline CD30 levels are reduced by 50% or more. Interestingly, low-dose SAHA treatment that maintained 50% or more of basal CD30 expression followed by subsequent treatment with brentuximab vedotin led to enhanced antitumor activity. The downregulation of CD30 was short lived upon SAHA removal, suggesting that allowing SAHA washout may circumvent any interactions with subsequent drug therapies. Our findings confirm the requirement of CD30 for brentuximab vedotin efficacy and suggest that combination treatment with SAHA in CD30(dim) tumors may decrease efficacy. Combination treatment in highly CD30(+) tumors, however, increases efficacy and warrants further consideration as a new treatment paradigm.

Anti-CD30 antibody conjugated liposomal doxorubicin with significantly improved therapeutic efficacy against anaplastic large cell lymphoma

The use of nano-carriers has been shown to improve the delivery and efficacy of chemotherapeutic agents in cancer patients. Recent studies suggest that decoration of the surface of nano-carriers with various targeting moieties may further improve the overall therapeutic efficacy. In this study, we compared the therapeutic efficacy of Doxil(®) (commercial doxorubicin-loaded liposomes) and that of Doxil(®) conjugated with anti-CD30 antibodies (CD30-targeted Doxil(®)) in treating anaplastic large cell lymphoma (ALCL), a type of T-cell lymphoma characterized by a high CD30 expression. Compared to Doxil(®), the CD30-targeted Doxil(®) showed a significantly higher binding affinity to ALCL cells (5.3% versus 27%, p = 0.005) and a lower inhibitory concentration at 50% (IC50) in-vitro (32.6 μg/mL versus 12.6 μg/mL, p = 0.006). In a SCID mouse xenograft model, CD30-targeted Doxil(®) inhibited tumor growth more significantly than the unconjugated formulation; specifically, tumors in mice treated with CD30-targeted Doxil(®) were significantly smaller than those in mice treated with Doxil(®) (average, 117 mm(3) versus 270 mm(3), p = 0.001) at 18 days after the tumors were inoculated. Our findings have provided the proof-of-principle of using CD30-targeted nano-carriers to treat cancers that are characterized by a high level of CD30 expression, such as ALCL.

Malignant germ cell-like tumors, expressing Ki-1 antigen (CD30), are revealed during in vivo differentiation of partially reprogrammed human-induced pluripotent stem cells

Because many of the genes used to produce induced pluripotent stem cells (iPSCs) from somatic cells are either outright established oncogenes, such as c-myc and Klf4, or potentially related to tumorigenesis in various cancers, both the safety and the risks of tumorigenesis linked to iPSC generation require evaluation. In this work, we generated, by lentivirus-mediated gene transfer of Oct4, Sox2, Nanog, and Lin28, two types of iPSCs from human mesenchymal stem cells and human amniotic fluid-derived cells: fully reprogrammed iPSCs with silencing of the four transgenes and partially reprogrammed iPSCs that still express one or several transgenes. We assessed the behavior of these cells during both their differentiation and proliferation using in vivo teratoma assays in nonobese diabetic mice with severe combined immunodeficiency. In contrast to fully reprogrammed iPSCs, 43% of partially reprogrammed iPSC cases (6 of 14 teratomas) generated major dysplasia and malignant tumors, with yolk sac tumors and embryonal carcinomas positive for α-fetoprotein, cytokeratin AE1/AE3, and CD30. This correlated with the expression of one or several transgenes used for the reprogramming, down-regulation of CDK 1A mRNA (p21/CDKN1A), and up-regulation of antiapoptotic Bcl-2 mRNA. Therefore, the oncogenicity of therapeutically valuable patient-specific iPSC-derived cells should be scrupulously evaluated before they are used for any clinical applications.

Removal of B cell epitopes as a practical approach for reducing the immunogenicity of foreign protein-based therapeutics

Immunogenicity of non-human proteins with useful therapeutic properties has prevented their development for use in the therapy of disease. However, this class of proteins could be very useful, if their immunogenicity could be markedly reduced so that many treatment cycles could be administered. One approach to reduce the immunogenicity of foreign proteins is to identify B cell epitopes on the protein and eliminate them by mutagenesis. In this article, theoretical aspects and experimental evidence for the feasibility of B cell epitope removal is reviewed. A special focus is given to our results with deimmunization of recombinant immunotoxins in which Fvs are fused to a 38kDa portion of the bacterial protein, Pseudomonas exotoxin A (PE38). Immunotoxins targeting CD22 and CD25 have produced complete remissions in many patients with drug resistant Hairy Cell Leukemia and are being evaluated in other malignancies. Experimental data summarized in this review indicates that removal of B cell epitopes is a practical approach for making less immunogenic protein therapeutics from non-human functional proteins. This approach requires grouping of the epitopes to identify targets for deimmunization followed by quantitative analysis of the decrease in affinity produced by the mutations in B cell epitopes.

Fc receptor-like 3 protein expressed on IL-2 nonresponsive subset of human regulatory T cells

Fc receptor-like 3 (FCRL3) is a cell surface protein homologous to Fc receptors. The FCRL3 gene is present in humans but not in mice. We found that FCRL3 protein is expressed on 40% of human naturally occurring CD4(+) regulatory T (nTreg) cells (CD4(+)CD25(+)CD127(low)). Sorted nTreg cells with the surface phenotype FCRL3(+) and FCRL3(-) were both hypoproliferative to TCR stimulation and both suppressive on proliferation of conventional T cells (CD4(+)CD25(-)) in vitro. They both expressed forkhead box p3 (Foxp3) protein, the intracellular regulatory T cell marker. However, in contrast to FCRL3(-) nTreg cells, FCRL3(+) nTreg cells were not stimulated to proliferate by the addition of exogenous IL-2. In addition, Foxp3(+) cells induced from conventional T cells by TGF-beta treatment did not exhibit FCRL3 expression. These results suggest that the FCRL3(+) subset of human nTreg cells identified in this study arise in vivo and Foxp3 expression alone is not sufficient to induce FCRL3 expression. FCRL3 may be involved in human-specific mechanisms to control the generation of nTreg cells.

Novel treatment strategies for patients with relapsed classical Hodgkin lymphoma

Although classical Hodgkin lymphoma (HL) is considered one of the most curable human cancers, the treatment of patients with relapsed and refractory disease, especially those who relapse after autologous stem cell transplantation, remains challenging. Furthermore, because the median age of the patients is in the mid-30s, the impact of early mortality on the number of years lost from productive life is remarkable. Patients with HL whose disease relapses after stem cell transplantation are rarely cured with current treatment modalities. New drugs and novel treatment strategies that are based on our understanding of the disease biology and signaling pathways are needed to improve treatment outcome for these patients. This review will focus on emerging new treatment modalities that are currently under investigation for patients with relapsed classical HL.

The CD30 gene promoter microsatellite binds transcription factor Yin Yang 1 (YY1) and shows genetic instability in anaplastic large cell lymphoma

CD30 is a member of the TNF receptor family. Our interest lies in understanding the control of CD30 expression, particularly as its over-expression provides a diagnostic marker for a subset of non-Hodgkin's lymphomas, particularly anaplastic large cell lymphoma (ALCL), and because anti-CD30 treatment has been shown to be efficacious. We have identified a number of regulatory regions, including an Sp1 element in the minimal promoter, and a downstream promoter element that is required for start site selection. The discovery of both an activating AP1 site and an upstream microsatellite that represses transcriptional activity of CD30 suggests that this region is involved in dysregulation of CD30 expression. We have now identified the major microsatellite binding activity as transcription factor Yin Yang 1 by both one-hybrid cDNA library screening and peptide mass fingerprinting. Due to the strong repressive effect of the microsatellite, we also investigated whether microsatellite instability may induce changes in CD30 expression and hence explain the over-expression of CD30 in ALCL. Laser capture microdissection of ALCL biopsies and CD30 microsatellite typing indicated that the neoplastic cells show a high degree of variation, but this does not correlate with high CD30 expression seen in ALCL.

Hodgkin's lymphoma: molecular targets and novel treatment strategies

The WHO classification of Hodgkin's lymphoma (HL) distinguishes between two major subtypes, classical and nodular lymphocyte predominant HL. Approximately 95% of patients with HL will have the classical HL histology, which is characterized by the presence of rare malignant Hodgkin's and Reed-Sternberg cells among an overwhelming number of benign reactive cells. In recent years, new studies have shed more light on the biological and molecular features of Hodgkin's and Reed-Sternberg cells, providing hope that new targeted therapy may be developed to enhance the cure rate and to reduce treatment-related toxicity. In this review, the current understanding of the pathology and biology of HL will be discussed, as well as the current treatment approaches for patients with classical HL. Future treatment strategies will also be discussed based on our understanding of HL biology.

Elevation of soluble CD307 (IRTA2/FcRH5) protein in the blood and expression on malignant cells of patients with multiple myeloma, chronic lymphocytic leukemia, and mantle cell lymphoma

CD307 is a differentiation antigen expressed in B-lineage cells. One soluble and two membrane-bound forms have been predicted and an enzyme-linked immunosorbent assay (ELISA) for soluble CD307 established. Our goal was to determine if CD307 is expressed on the surface of cells from patients with multiple myeloma (MM), chronic lymphocytic leukemia (CLL), mantle cell lymphoma (MCL) and other B-cell malignancies and if soluble CD307 levels are elevated in the blood of patients with these B-cell malignancies. Cells and blood were collected from patients. Expression of CD307 was measured by flow cytometry and blood levels of soluble CD307 by ELISA. High soluble CD307 levels were detected in 21/43 (49%) of patients with MM, 36/46 (78%) with CLL and 9/24 (38%) with MCL. Soluble CD307 levels correlated with plasma cell percentages in bone marrow aspirates in MM and total white blood cells in CLL. CD307 on the cell membrane was detected by flow cytometry in 8/8 MM, 23/29 CLL and 4/5 MCL samples. Because CD307 is present on malignant cells from patients with MM, CLL and MCL, CD307 may be a useful therapeutic target for the treatment of these diseases.

Targeting Lymphoma Cells and Their Microenvironment with Novel Antibodies

Novel monoclonal antibodies are currently being evaluated and have been shown to have significantly influenced the treatment of Hodgkin's and non-Hodgkin's lymphoma. It is of the utmost importance to reduce treatment-related toxicity and, hopefully, improve the cure rate of lymphoma. This is possible by using novel therapies such as monoclonal antibodies, which target tumor cells while sparing normal cells. Investigational antibody therapies include those targeting malignant cells as well as those targeting the microenvironment. Continued investigation is encouraged to combine monoclonal antibodies with other targeted therapies and incorporate their use into standards of care in the treatment of lymphoma.