The CD40 agonist HERA-CD40L results in enhanced activation of antigen presenting cells, promoting an anti-tumor effect alone and in combination with radiotherapy

Introduction

The ability to modulate and enhance the anti-tumor immune responses is critical in developing novel therapies in cancer. The Tumor Necrosis Factor (TNF) Receptor Super Family (TNFRSF) are potentially excellent targets for modulation which result in specific anti-tumor immune responses. CD40 is a member of the TNFRSF and several clinical therapies are under development. CD40 signaling plays a pivotal role in regulating the immune system from B cell responses to myeloid cell driven activation of T cells. The CD40 signaling axis is well characterized and here we compare next generation HERA-Ligands to conventional monoclonal antibody based immune modulation for the treatment of cancer.

Methods & results

HERA-CD40L is a novel molecule that targets CD40 mediated signal transduction and demonstrates a clear mode of action in generating an activated receptor complex via recruitment of TRAFs, cIAP1, and HOIP, leading to TRAF2 phosphorylation and ultimately resulting in the enhanced activation of key inflammatory/survival pathway and transcription factors such asNFkB, AKT, p38, ERK1/2, JNK, and STAT1 in dendritic cells. Furthermore, HERA-CD40L demonstrated a strong modulation of the tumor microenvironment (TME) via the increase in intratumoral CD8+ T cells and the functional switch from pro-tumor macrophages (TAMs) to anti-tumor macrophages that together results in a significant reduction of tumor growth in a CT26 mouse model. Furthermore, radiotherapy which may have an immunosuppressive modulation of the TME, was shown to have an immunostimulatory effect in combination with HERA-CD40L. Radiotherapy in combination with HERA-CD40L treatment resulted in an increase in detected intratumoral CD4+/8+ T cells compared to RT alone and, additionally, the repolarization of TAMs was also observed, resulting in an inhibition of tumor growth in a TRAMP-C1 mouse model.

Discussion

Taken together, HERA-CD40L resulted in activating signal transduction mechanisms in dendritic cells, resulting in an increase in intratumoral T cells and manipulation of the TME to be pro-inflammatory, repolarizing M2 macrophages to M1, enhancing tumor control.

Abstract 1587: Generation and characterization of novel bispecific molecules combining single-chain-CD40L with anti-CEA, anti-CD95L or anti-PD-L1 targeting moieties

CD40 ligand is a member of the TNF superfamily (TNF-SF) and a key regulator of the immune system. Its cognate receptor CD40 is expressed on antigen-presenting cells and on many tumor types, and has emerged as an attractive target for immunological cancer treatment. We developed HERA-CD40L, a construct composed of a trivalent single-chain CD40L-receptor-binding-domain (scCD40L-RBD) linked to a silenced human IgG1-Fc-domain thereby generating a hexavalent molecule. We showed previously that HERA-CD40L mimics the natural ligand, thereby inducing potent agonistic activity which is independent of FcγR mediated crosslinking and superior to anti-CD40 benchmark antibodies. For combinatorial cancer immunotherapy we have created bispecific molecules by combining the HERA-CD40L scaffold with antibody derived domains targeting different classes of tumor associated antigens. These bispecific fusion proteins combine the potent co-stimulatory CD40-agonist with either direct tumor-cell targeting and/or additional immunomodulatory activities in the tumor microenvironment. To evaluate the different fusion protein formats, the tumor associated antigens CEA, PD-L1 and CD95L were chosen as model-targets. In addition to the hexavalent targeted HERA-CD40L, trivalent targeted fusion proteins, employing the scCD40L-RBD as building block, were created as well. All engineering prototypes were produced in CHO-S cells and purified, resulting in highly pure non-aggregating protein lots as demonstrated by SDS-PAGE and HPLC-SEC. Functional binding to their respective targets was shown by ELISA and to proof biological in vitro activity luciferase reporter gene assays were employed. The basic underlying immunological processes have been investigated in vitro. The trivalent CD40L, the trivalent CD40L-bispecifics anti-CD95L-scCD40L-RBD and anti-CEA-scCD40L-RBD as well as anti-CD40, anti-PD-L1 or anti-CD95L antibodies did not activate human monocytes, even if the antibodies were co-administered with trivalent CD40L. In contrast, the hexavalent HERA-CD40L, the hexavalent bifunctional CD40L-constructs and the trivalent anti-PD-L1-scCD40L-RBD-construct induced strong activation/maturation of the monocytes as indicated by CD83, CD86, HLA-DR upregulation which was accompanied by increased chemokine receptor (CD54, CCR7) and PD-L1 expression. When co-cultured with CD3 positive T cells, these pre-activated monocytes led to subsequent activation of CD4 as well as CD8 positive T cells, indicated by increased expression of CD25, CD69 and CD54. This clearly shows that the close proximity of anti-PD-L1 and trivalent CD40L within one molecule makes a huge difference for biological activity. Hence, these novel bispecific constructs are a promising therapeutic approach to promote anti-tumor immune responses.

Citation Format: Matthias Schroeder, Katharina Billian-Frey, Jaromir Sykora, Mauricio Redondo-Mueller, Karl Heinonen, Jamie Frankish, Christian Gieffers, Meinolf Thiemann, Oliver Hill. Generation and characterization of novel bispecific molecules combining single-chain-CD40L with anti-CEA, anti-CD95L or anti-PD-L1 targeting moieties [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1587.

CD95L and Anti-Tumor Immune Response: Current Understanding and New Evidence

The ability of FasL/CD95L to induce apoptosis in various Fas/CD95-expressing cells has been described in the context of hematopoiesis or thymic elimination of self-reactive T cells and resolution of an acute immune response under physiological conditions. At the same time, non-apoptotic CD95 activation is widely described in cancer and shown to stimulate invasiveness of cancer cells, promote cancer progression as well as stemness of cancer cells. This paper puts emphasis on the evolving understanding of expression and the non-apoptotic activities of the CD95/CD95L signaling pathway on the function of tumor cells, tumor microenvironment and immune cells. The emerging evidence to support the role of CD95/CD95L signaling in the anti-tumor immune response will be presented in the context of various malignancies and the modalities of potential therapeutic interventions via selective CD95L inhibition in combination with traditional interventions such as RT, chemotherapy and immune checkpoint inhibitors.

Abstract 4460: Novel bispecific molecules combining HERA-CD40L with anti-CEA or with anti-PD-L1 for targeting

CD40 ligand is a member of the TNF superfamily and a key regulator of the immune system. Its cognate receptor CD40 is expressed on antigen-presenting cells and on many tumor types, and has emerged as an attractive target for immunological cancer treatment. We have shown previously, that hexavalent HERA-CD40L is a potent CD40 agonist which is clearly superior over anti-CD40 benchmark antibodies and able to establish single agent anti-tumor immune responses both in vitro and in vivo. Since this compound qualifies as an ideal candidate for combinatorial cancer treatments we have created bispecific molecules by adding antibody derived targeting domains to the HERA-CD40L scaffold. These bispecific fusion proteins combine the potent co-stimulatory CD40-agonist with additional functionalities to enable tumor targeting and/or additional immuno-modulatory activities. To evaluate the different fusion protein formats in principle, the tumor associated antigens CEA and PD-L1 were chosen as targets. In addition to the hexavalent targeted HERA-CD40L, trivalent targeted fusion proteins employing the single-chain CD40L (scCD40L) as building block were created. Anti-CEA-HERA-CD40L, anti-CEA-trivalent scCD40L, anti-PD-L1-HERA-CD40L and anti-PD-L1-trivalent scCD40L were produced in CHO-S cells and purified resulting in highly pure non-aggregating protein lots as demonstrated by SDS-PAGE and HPLC-SEC. ELISA assays confirmed the specific binding to their targets - CD40 and CEA or CD40 and PD-L1, respectively. Employing a CD40 Luciferase reporter gene assay, hexavalent anti-CEA-HERA-CD40L showed a strong agonistic activity which was clearly superior to the anti-CEA-trivalent scCD40L- construct. Similarly, hexavalent anti-PD-L1-HERA-CD40L showed a strong agonistic activity in this assay which also was clearly superior to the anti-PD-L1-trivalent scCD40L construct. A PD-1/PD-L1 Luciferase reporter gene assay assessing the cellular activity of compounds interfering with PD-1/PD-L1 binding showed a clear activity for anti-PD-L1-HERA-CD40L. As expected for an assay assessing antagonistic activities, the activity of hexavalent anti-PD-L1-HERA-CD40L was in the same range as a reference anti-PD-L1 antibody and the anti-PD-L1-trimeric scCD40L- construct. Based on the in vitro data presented, the bispecific molecules combining HERA-CD40L with tumor targeting (anti-CEA) or with a checkpoint-blockade inhibitor (anti-PD-L1) are promising therapeutic approaches to promote anti-tumor immune responses.

Citation Format: Meinolf Thiemann, Katharina Billian-Frey, Matthias Schröder, Christian Merz, Jaromir Sykora, David M. Richards, Mauricio Redondo Müller, Julian P. Sefrin, Karl Heinonen, Christian Gieffers, Oliver Hill. Novel bispecific molecules combining HERA-CD40L with anti-CEA or with anti-PD-L1 for targeting [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4460.

Abstract 4529: Neutralization of pro-apoptotic CD95L by Asunercept/APG101 does not impair anti-tumor immune responses

The CD95 ligand (CD95L) is frequently overexpressed in cancers and tumor-associated endothelia, but also other immune cells like MDSCs and Tregs. Binding of CD95L expressed on tumors or regulatory immune cells to activated CD95-expressing effector cells triggers activation-induced apoptosis (AICD) or impairs their proliferation. In contrast, most tumors do also express CD95, but are intrinsically resistant to CD95-induced apoptosis. Thus, CD95L in the tumor microenvironment greatly contributes to the observed immunosuppression and escape from tumor surveillance by the immune system, making CD95 a potential immune checkpoint. Asunercept (APG101) is a fully human fusion protein consisting of the extracellular domain of CD95 and the Fc-domain of human IgG1, which efficiently inhibits CD95/CD95L signaling. Clinical efficacy has been demonstrated in a controlled randomized phase 2 study in patients with recurrent glioblastoma. Here we examined the effects of APG101 on innate and adaptive immune cells and subsequent effects on tumor cell killing. Subtypes of in vitro differentiated macrophages generated with and without exposure to APG101 were functionally and phenotypically analyzed by ELISA and multi-color flow cytometry following various stimuli. APG101 did not alter differentiation patterns and response of M1- and M2-like macrophages in vitro. Direct co-culture of monocytes with tumor cells resulted in an M2/TAM-like phenotype which was not influenced by APG101, but re-programming to an M1-like state was achieved by addition of a CD40 agonist. Effects of APG101 on the proliferation and activation of CD8+ T cells in the presence of autologous CD4+ T(reg) cells and allogeneic APC was assessed by CFSE-dilution and multi-color flow cytometry, respectively. The proliferation rate of CD8 T cells in co-cultures with CD4 T(reg) cells in response to stimulation with APCs was increased in the presence of APG101. Real-time cell analysis was performed employing direct co-cultures of activated T cells and tumor cell lines. Tumor killing assays using direct co-cultures of in vitro activated T cells with and without APG101 demonstrate that tumor killing was not impaired by APG101.

Conclusion: Asunercept (APG101) is a potent inhibitor of pro-apoptotic/anti-proliferative CD95/CD95L signaling in immune cells and protects activated immune cells from activation induced cell death (AICD). Our results suggest that APG101 does not impair CD8 T cell activation, but rather supports their proliferation by disrupting CD95/CD95L interaction with regulatory T cells. Importantly, the primary anti-tumor killing mechanisms is most likely CD95L-independent and remains unaffected by the presence of APG101. The inhibition of CD95 signaling as an immune checkpoint represents an attractive and novel concept for immunologic treatment of tumors and the combination of Asunercept/APG101 with co-stimulatory TNFR-SF agonists is currently being investigated.

Citation Format: Christian Merz, Jaromir Sykora, Rebecca Hussong, Meinolf Thiemann, Oliver Hill, Christian Gieffers. Neutralization of pro-apoptotic CD95L by Asunercept/APG101 does not impair anti-tumor immune responses [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4529.

Abstract 1076: Hexavalent HERA-CD40L induces a productive T cell-mediated anti-tumor immune response and shows superior activity in comparison to benchmark CD40 agonistic antibodies

TNF Receptor Superfamily members (TNF-R-SF), including CD40, are key regulators of the immune system and have been immunotherapeutic targets for over 20 years. CD40 signaling serves as an important co-stimulatory signal for antigen-presenting cells (APC). For the induction of a CD40 driven anti-tumor immune response multiple approaches, - most of them antibody based - are currently under investigation. However, the structural necessity of trimerization within the TNF-R-SF, defines bivalent antibodies generally as unfeasible inducers of signaling events within this protein family. To overcome the known inadequacies of antibodies, we developed HERA-CD40L, composed of two trivalent CD40L-receptor-binding domains, fused to a silenced human IgG1 Fc-domain. This hexavalent CD40 agonist mimics the natural ligand and enables efficient receptor clustering and superior signaling. HERA-CD40L treatment increased the pro-inflammatory state of all CD40-expressing cells examined. It promoted the licensing of dendritic cells (DC), macrophages, B cells and other APC. Comparison to benchmark antibodies revealed that HERA-CD40L elicited a stronger and more rapid activation of NFκB signaling in primary B cells. HERA-CD40L treatment, but not clinical benchmark antibodies triggered immediate NFκB, MAPK, PI3K and STAT-1 signaling in primary monocyte-derived immature DC. As a result, HERA-CD40L induced upregulation of activation markers and co-stimulatory molecules in B cells and DC. Using SEC fractionation followed by a CD40 reporter assay, we could furthermore demonstrate that the activity of a clinical benchmark antibody derived exclusively from antibody aggregates. In vitro HERA-CD40L treatment converted immature phagocytic macrophages into mature/professional APC and induced repolarization of M2- to M1-like macrophages. These findings were confirmed in vivo using a mouse surrogate (mmHERA-CD40L). Upon treatment of MC38-CEA and CT26wt syngeneic mouse models, we observed single agent anti-tumor efficacy. In the CT26wt model, mmHERA-CD40L treatment converted cold into hot tumors by increasing T cell infiltration. Furthermore, mmHERA-CD40L induced a strong dose dependent decrease of tumor associated pro-tumorigenic M2-macrophages indicating a profound reorganization of the tumor microenvironment. Both in vitro (human) and in vivo (mouse), HERA-CD40L increased antigen-specific immune system activation without affecting the non-specific immune cells. These data, together with pilot PD/safety results, demonstrate that the activity of HERA-CD40L is both potent and safe. In conclusion, HERA-CD40L is a potent agonist able to show single agent anti-tumor activity. The biological activity is distinct from and superior to clinical benchmark “agonistic” antibodies. HERA-CD40L has a well-defined mechanism of action, does not depend on Fc gamma receptor-mediated crosslinking and hence functions as a true agonist.

Citation Format: Christian Gieffers, David M. Richards, Jaromir Sykora, Christian Merz, Julian P. Sefrin, Katharina Billian-Frey, Karl Heinonen, Mauricio Redondo Müller, Matthias Schröder, Meinolf Thiemann, Oliver Hill. Hexavalent HERA-CD40L induces a productive T cell-mediated anti-tumor immune response and shows superior activity in comparison to benchmark CD40 agonistic antibodies [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1076.

Correction: CD95 maintains stem cell-like and non-classical EMT programs in primary human glioblastoma cells

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

P14.52 Differential methylation of a single CpG site in the CD95 ligand promoter affects gene activity and correlates with invasiveness of glioma cells

BACKGROUND

CD95 ligand (TNFSF6/APO-1L/FASLG) is a member of the Tumour Necrosis Factor Super Family (TNF-SF). Binding of the CD95 ligand (CD95L) to CD95 expressed on intrinsically apoptosis-resistant cancer cells like glioblastoma, triggers intracellular signal transduction resulting in increased tumour growth and invasiveness. A phase II clinical trial in patients with recurrent glioblastoma (NCT01071837) treated by Asunercept (a recombinant glycosylated fusion protein, which selectively binds and inhibits CD95L activity) was followed by a genome-wide assessment of DNA methylation. Here, a CpG-site (designated CpG2) within the CD95L-promotor was identified, exhibiting differential methylation between Asunercept responders (PFS>5 months) and non-responders (PFS < 2 months) with a significant survival benefit achieved in Asunercept treated patients with low CpG2 methylation (HR 0.34, p = 0.025).

METHODS AND RESULTS

We have performed in vitro studies to establish a link between the CpG2 methylation status and cellular characteristics of glioblastoma cell lines. A 3-dimensional spheroid invasion assay showed that highly methylated glioma cells like T98G did not grow and invade the surrounding matrix as aggressively compared to spheroids formed from low methylated glioma cells, e.g. U87-MG. Invasive growth of U87-MG spheroids in these assays was suppressed in the presence of Asunercept. A 1 kb fragment of the T98G CD95L promoter was subsequently cloned into a CpG-free reporter gene plasmid. Luciferase-based reporter gene assays of in vitro methylated and unmethylated plasmids in transfected HEK cells indicate that the CD95L promoter, despite the observed sparseness of CpG sites, is at least partially regulated by its methylation level. Furthermore, mutational disruption of the CpG2 site completely silenced reporter gene activity in vitro, which insinuates that both methylation level and gene promoter sequence are involved in regulation of the CD95L gene.

CONCLUSION

In essence, the level of CpG2 methylation correlates to aggressiveness of glioma derived cancer spheroids in vitro, and methylation of the CD95L promoter in glioblastoma tissue from patients might warrant use as a potential biomarker predicting response to therapy with Asunercept. We are currently developing a specific and sensitive assay to quantify CpG2 methylation considered as a companion diagnostic for further clinical studies.

Concepts for agonistic targeting of CD40 in immuno-oncology

TNF Receptor Superfamily (TNF-R-SF) signaling is a structurally well-defined event that requires proper receptor clustering and trimerization. While the TNF-SF ligands naturally exist as trivalent functional units, the receptors are usually separated on the cell surface. Critically, receptor assembly into functional trimeric signaling complexes occurs through binding of the natural ligand unit. TNF-R-SF members, including CD40, have been key immunotherapeutic targets for over 20 years. CD40, expressed by antigen-presenting cells, endothelial cells, and many tumors, plays a fundamental role in connecting innate and adaptive immunity. The multiple investigated strategies to induce CD40 signaling can be broadly grouped into antibody-based or CD40L-based approaches. Currently, seven different antibodies and one CD40L-based hexavalent fusion protein are in active clinical trials. In this review, we describe the biology and structural properties of CD40, requirements for agonistic signal transduction through CD40 and summarize current attempts to exploit the CD40 signaling pathway for the treatment of cancer.

Asunercept as an innovative therapeutic approach for recurrent glioblastoma and other malignancies

Glioblastoma is the most common and aggressive malignant tumor of the central nervous system. Despite the existing high unmet medical needs, the past few decades have seen no notable improvement in overall survival for glioblastoma patients. One active area of research to develop new therapeutic options for this disease is focusing on the CD95/Fas receptor and its ligand CD95L/FasL. It is now recognized that in addition to its role in programmed cell death, CD95/CD95L signaling is involved in a wide range of other apoptotic and non-apoptotic pathways directed toward T-effector cells and cells in the tumor microenvironment involved in tumor progression and invasiveness. Asunercept is a first-in-class recombinant glycosylated fusion protein, which has been designed to selectively bind to CD95L and therefore disrupt CD95/CD95L signaling. The current report provides a brief overview of the role of the CD95/CD95L signaling pathway in cancer pathogenesis and discusses how asunercept was designed to bind and neutralize CD95L and disrupt signaling thereby potentially improving outcomes in glioblastoma and other malignancies.

HERA-GITRL activates T cells and promotes anti-tumor efficacy independent of FcγR-binding functionality

Background

Glucocorticoid-induced TNFR-related protein (TNFRSF18, GITR, CD357), expressed by T cells, and its ligand (TNFSF18, GITRL), expressed by myeloid populations, provide co-stimulatory signals that boost T cell activity. Due to the important role that GITR plays in regulating immune functions, agonistic stimulation of GITR is a promising therapeutic concept. Multiple strategies to induce GITR signaling have been investigated. The limited clinical efficacy of antibody-based GITR agonists results from structural and functional characteristics of antibodies that are unsuitable for stimulating the well-defined trimeric members of the TNFRSF.

Methods

To overcome limitations of antibody-based TNFRSF agonists, we have developed HERA-GITRL, a fully human hexavalent TNF receptor agonist (HERA) targeting GITR and mimicking the natural signaling concept. HERA-GITRL is composed of a trivalent but single-chain GITRL-receptor-binding-domain (scGITRL-RBD) unit fused to an IgG1 derived silenced Fc-domain serving as dimerization scaffold. A specific mouse surrogate, mmHERA-GITRL, was also generated to examine in vivo activity in respective mouse tumor models.

Results

For functional characterization of HERA-GITRL in vitro, human immune cells were isolated from healthy-donor blood and stimulated with anti-CD3 antibody in the presence of HERA-GITRL. Consistently, HERA-GITRL increased the activity of T cells, including proliferation and differentiation, even in the presence of regulatory T cells.

In line with these findings, mmHERA-GITRL enhanced antigen-specific clonal expansion of both CD4+ (OT-II) and CD8+ (OT-I) T cells in vivo while having no effect on non-specific T cells. In addition, mmHERA-GITRL showed single-agent anti-tumor activity in two subcutaneous syngeneic colon cancer models (CT26wt and MC38-CEA). Importantly, this activity is independent of its FcγR-binding functionality, as both mmHERA-GITRL with a functional Fc- and a silenced Fc-domain showed similar tumor growth inhibition.

Finally, in a direct in vitro comparison to a bivalent clinical benchmark anti-GITR antibody and a trivalent GITRL, only the hexavalent HERA-GITRL showed full biological activity independent of additional crosslinking.

Conclusion

In this manuscript, we describe the development of HERA-GITRL, a true GITR agonist with a clearly defined mechanism of action. By clustering six receptor chains in a spatially well-defined manner, HERA-GITRL induces potent agonistic activity without being dependent on additional FcγR-mediated crosslinking.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0671-4) contains supplementary material, which is available to authorized users.

Abstract 5015: HERA-CD40L a hexavalent CD40 agonist induces T cell mediated anti-tumor immune response and shows superior activity in direct comparison to benchmark agonistic antibodies

CD40 ligand is a member of the TNF superfamily (TNF-SF) and a key regulator of the immune system. Its cognate receptor CD40 is expressed on antigen-presenting cells and on many tumor types, and has emerged as an attractive target for immunological cancer treatment.

Effective signaling for CD40/CD40L depends on the formation of a defined ligand/receptor complex triggered by interaction of a trimeric CD40L with three CD40 receptor chains allowing correct assembly of intracellular signaling complexes and respective signal transduction. Trimerization is a hallmark of the TNF-SF and has pivotal implications for the generation of respective TNFR-SF agonists in particular. However, ignoring the underlying trimeric structural concept bivalent antibodies are still the main agonistic biotherapeutic development candidates to address TNFR-SF members including CD40. Such bivalent antibodies are inherently associated with limited agonistic activity that requires Fc/FcγR interactions or potentially show increased toxicity caused by super-clustering of endogenous ligand receptor pairs.

To overcome the inadequacies of antibodies, we have developed HERA-CD40L composed of three receptor binding domains in a single chain arrangement, linked to an Fc-silenced human IgG1 thereby generating a hexavalent molecule. HERA-CD40L mimics the natural ligand, induces potent agonistic activity and, importantly, does not require FcγR mediated crosslinking. Comparison of HERA-CD40L to anti-CD40 benchmark antibodies (including CP-870,893) revealed superiority for HERA-CD40L in all assays tested. (i) In contrast to antibodies, HERA-CD40L showed strong activation of NFkB signaling upon treatment of B cells. (ii) HERA-CD40L treatment, but not clinical benchmark antibodies, converts immature phagocytic macrophages into mature/professional APCs and promoted differentiation towards the M1 spectrum macrophages. (iii) Furthermore, HERA-CD40L treated PBMCs stimulate potent allogeneic anti-tumor T cell response that was not detectable for CD40-antibodies.

In vivo, a murine surrogate of HERA-CD40L stimulated clonal expansion of OT-I specific murine CD8+ T cells without affecting non-specific immune cells. In the syngeneic CT26wt mouse model mHERA-CD40L treatment converts cold into hot tumors by increasing infiltration of CD8+ and CD4+ T cells. In addition mHERA-CD40L showed single agent anti-tumor activity in the CD40-negative syngeneic MC38-CEA mouse model, suggesting an involvement of the immune system in controlling tumor growth.

In summary HERA-CD40L is a potent agonist able to establish single agent anti-tumor immune responses. Comparison to bivalent benchmark antibodies showed superior biological activity of HERA-CD40L and qualifies this molecule as an ideal candidate for combinatorial cancer treatments.

Citation Format: Christian Gieffers, Jaromir Sykora, Christian Merz, Mauricio Redondo Müller, David M. Richards, Julian Sefrin, Katharina Billian-Frey, Karl Heinonen, Viola Marschall, Matthias Schröder, Harald Fricke, Meinolf Thiemann, Hill Oliver. HERA-CD40L a hexavalent CD40 agonist induces T cell mediated anti-tumor immune response and shows superior activity in direct comparison to benchmark agonistic antibodies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5015.

Abstract 4845: HERA-CD27L, a true CD27 agonist, is a hexavalent CD27 ligand that enhances T cell activation and induces potent anti-tumor immunity

Agonistic stimulation of TNFRSF members like CD27 is a promising strategy to boost anti-tumor responses. Although antibodies are effective inhibitors of signaling, they have shown minimal agonistic activity due to their limited binding domains, flexibility and the toxicity mediated by Fc/FcγR interactions. TNFRSF signaling is a structurally well-defined event that takes place during cell contact. The trimeric-trivalent TNFSF-receptor binding domain (TNFSF-RBD) on the conducting cell and the resulting multi-trimer-based receptor clustering on the receiving cell are essential for signaling. In contrast to antibodies, HERA-CD27L mimics the natural ligand and induces potent activity. In order to understand the activity of HERA-CD27L, human T cells were stimulated in the presence of HERA-CD27L, the trimeric CD27L or a clinical benchmark anti-CD27 antibody. In all assays, treatment with the hexavalent HERA-CD27L significantly boosted T cell activation, proliferation and differentiation. Furthermore, the hexavalent molecule was always superior to the trimeric CD27L and bivalent antibody. In fact, treatment with the anti-CD27 antibody resulted in significantly weaker proliferation compared to anti-CD3 antibody alone. To understand early events, we tested CD27 signaling using a reporter cell assay. Treatment with HERA-CD27L and CD27L resulted in high and intermediate, respectively, reporter activity. In contrast, the anti-CD27 antibody failed to show any signaling activity across a wide range of concentrations. Since most T cells express CD27, there is potential for non-specific T cell activation. This was examined by comparing OVA-specific and non-specific T cells in the same environment using the CD8+ “OT-I” T cell adoptive transfer mouse model. Following a single dose of HERA-CD27L, serial blood samples showed a significant and HERA-CD27L dose-dependent clonal expansion of OT-I T cells. OT-I T cells expressed high levels of activation markers, while the endogenous T cells failed to show any response. The potent single-agent anti-tumor efficacy of the hexavalent HERA-CD27L was demonstrated in two different mouse models. With CT26wt, HERA-CD27L also showed superior activity compared to anti-PD-1 antibody. Furthermore, combination of HERA-CD27L and anti-PD-1 antibody showed additive effects. Finally, early treatment with HERA-CD27L significantly increased overall survival, from 19 to 41 days, and tumor-free animals still alive at the end of the study were protected from tumor re-challenge. Various strategies have been proposed for targeting CD27 for cancer therapy. As we have shown here, the hexavalent HERA-CD27L has superior activity compared to bivalent antibodies. Altogether, HERA-CD27L shows single-agent anti-tumor efficacy, is well tolerated by multiple relevant species and the lead candidate is currently ready for GMP cell line development.

Citation Format: Julian P. Sefrin, David M. Richards, Katharina Billian-Frey, Karl Heinonen, Viola Marschall, Christian Merz, Mauricio Redondo Müller, Matthias Schröder, Jaromir Sykora, Meinolf Thiemann, Harald Fricke, Christian Gieffers, Oliver Hill. HERA-CD27L, a true CD27 agonist, is a hexavalent CD27 ligand that enhances T cell activation and induces potent anti-tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4845.

A Single-Chain-Based Hexavalent CD27 Agonist Enhances T Cell Activation and Induces Anti-Tumor Immunity

Tumor necrosis factor receptor superfamily member 7 (TNFRSF7, CD27), expressed primarily by T cells, and its ligand CD27L (TNFSF7, CD70) provide co-stimulatory signals that boost T cell activation, differentiation, and survival. Agonistic stimulation of CD27 is therefore a promising therapeutic concept in immuno-oncology intended to boost and sustain T cell driven anti-tumor responses. Endogenous TNFSF/TNFRSF-based signal transmission is a structurally well-defined event that takes place during cell-to-cell-based contacts. It is well-established that the trimeric-trivalent TNFSF-receptor binding domain (TNFSF-RBD) exposed by the conducting cell and the resulting multi-trimer-based receptor clustering on the receiving cell are essential for agonistic signaling. Therefore, we have developed HERA-CD27L, a novel hexavalent TNF receptor agonist (HERA) targeting CD27 and mimicking the natural signaling concept. HERA-CD27L is composed of a trivalent but single-chain CD27L-receptor-binding-domain (scCD27L-RBD) fused to an IgG1 derived silenced Fc-domain serving as dimerization scaffold. The hexavalent agonist significantly boosted antigen-specific T cell responses while having no effect on non-specific T cells and was superior over stabilized recombinant trivalent CD27L. In addition, HERA-CD27L demonstrated potent single-agent anti-tumor efficacy in two different syngeneic tumor models, MC38-CEA and CT26wt. Furthermore, the combination of HERA-CD27L and an anti-PD-1 antibody showed additive anti-tumor effects highlighting the importance of both T cell activation and checkpoint inhibition in anti-tumor immunity. In this manuscript, we describe the development of HERA-CD27L, a true CD27 agonist with a clearly defined forward-signaling mechanism of action.

Abstract 1760: The hexavalent CD40 agonist HERA-CD40L augments multi-level crosstalk between T cells and antigen-presenting cells

Introduction: HERA-CD40L is a novel hexavalent CD40 agonist engineered with the HERA-Technology developed by Apogenix. We have previously shown that the natural binding mode via the receptor/ligand binding domains and the high clustering capacity for the cognate receptor clearly distinguish HERA-CD40L from other, e.g. antibody-based, CD40-targeting compounds. Here, we report on the effects of HERA-CD40L on crosstalk between T cells and antigen presenting cells (APC) and the functional consequences in vitro. Materials & Methods: Biological activity of CD40 agonists was analyzed using co-cultures of primary T cells with B cells or monocytes/macrophages. All primary cells were isolated by negative selection using magnetic sorting from healthy donor buffy coats. Expression of CD markers upon CD40 ligation on B cells and monocytes was analyzed by flow cytometry (FC). Monitoring of T cell-induced killing of tumor cells primed in direct co-cultures with APC was done on a real-time cell analysis system (xCELLigence). For analysis of phagocytosis, we developed an FC-based assay employing primary monocytes/macrophages and Jurkat A3 cells. Results: Treatment of primary B cells and monocytes with HERA-CD40L induced expression of co-stimulatory molecules, like CD86, and promotes M1 maturation of naïve (M0) monocytes. In vitro, treatment of alternatively activated M2 macrophages with HERA-CD40L induced an M2 to M1 phenotype switch (re-programming) which concurs with CD16 downregulation and a dose-dependent decrease of phagocytic activity of re-programmed macrophages compared to M0 or M2 macrophages. Primary B cells and M1 macrophages enhanced the proliferation and cytotoxic activity of naïve T cells in direct co-cultures in the presence of HERA-CD40L. The activating effect on T cells required direct cell-cell contact with APC and was not observed in indirect co-cultures. Functionally, neutralization of either MHC-I or CD80/CD86 in direct co-cultures inhibited full activation of the T cells in vitro as shown by kill assays with various tumor cell lines. Conclusion: The hexavalent CD40 agonist HERA-CD40L produced by the Apogenix HERA-Technology is a potent immune-regulator acting on B cells and myeloid cells. HERA-CD40L promotes activation of B cells, maturation of APC and induces an M2 to M1 phenotype switch which inhibits tolerance-inducing phagocytic activity of the repolarized macrophages in vitro. In response to CD40 ligation on APC, an efficient anti-tumor response is conferred to primary T cells through cell-cell interactions via MHC-I and CD80/CD86.

Citation Format: Christian Merz, Jaromir Sykora, Viola Marschall, David M. Richards, Meinolf Thiemann, Harald Fricke, Oliver Hill, Christian Gieffers. The hexavalent CD40 agonist HERA-CD40L augments multi-level crosstalk between T cells and antigen-presenting cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1760.

Abstract 3754: The novel hexavalent human CD137/4-1BB agonist HERA-CD137L promotes anti-cancer immunity by activating CD8 T cells while regulatory T cells are not affected

CD137/4-1BB is an inducible costimulatory receptor mainly expressed on immune cells following activation. Binding of the cognate ligand CD137L/4-1BBL leads to receptor trimerization and activation of signaling cascades involved in expansion and survival of T cells and myeloid cells as well as memory formation and protection against autoimmunity. Apogenix´ HERA technology is based on trivalent single-chain molecular mimics of the TNF-SF receptor binding domains fused to a silenced human IgG1-Fc-domain which serves exclusively as a dimerization scaffold. This results in hexavalent agonists replicating the natural receptor binding mode. Due to their inherent high receptor clustering capacity, HERA compounds are true agonists and their biological activity is, in contrast to bivalent anti-TNFR-SF antibodies, independent of FcR-mediated crosslinking events. HERA-CD137L was produced in CHO-S cells and purified resulting in highly pure non-aggregating protein lots. PK studies in mice demonstrated a terminal half-life of 75 hours indicating excellent in vivo stability. To study the effects on immune cells in vitro, T cells were isolated from healthy-donor buffy coats and stimulated with anti-CD3 antibody alone or in combination with HERA-CD137L. Using multicolor flow cytometry, we confirmed that expression of CD137 increased on CD8+ T cells following stimulation with anti-CD3 antibody. In accord with upregulation of the activation markers CD25 and CD69 and the memory marker CD45RO, treatment with HERA-CD137L enhanced proliferation of both CD4+ and CD8+ T cells, as determined by CFSE analysis. Intracellular accumulation of IFN-γ, TNF-α, Granzyme B and Perforin upon CD137 ligation was observed in CD8+ but not CD4+ T cells. HERA-CD137L treatment of THP-1 monocytes co-cultured with primary T cells also increased their cytotoxic activity against multiple tumor cell lines, including colorectal and mammary, as shown in a real-time live cell analysis (RTCA) assay. Primary human monocytes express low levels of CD137 and differentiation to macrophages in vitro did not increase expression. However, pro-inflammatory cytokines such as TNF-α and the chemokine CCL4 were secreted after stimulation with HERA-CD137L. RTCA assays further demonstrated enhanced antigen-specific killing of MDA-MB231 tumor cells by HERA-CD137L treated T cells. HERA-CD137L conveys its activity through effector T cell proliferation while regulatory T (Treg) cell proliferation or production of anti-inflammatory cytokines are not altered in Treg cell cultures. In contrast, HERA-CD137L prevented Treg-mediated suppression of effector T cells. Based on the in vitro data presented, HERA-CD137L is a promising candidate to promote anti-tumor immune responses either as single agent or in combination with other IO-compounds.

Citation Format: Meinolf Thiemann, Jaromir Sykora, David M. Richards, Christian Merz, Viola Marschall, Mauricio Redondo Mueller, Julian P. Sefrin, Karl Heinonen, Harald Fricke, Christian Gieffers, Oliver Hill. The novel hexavalent human CD137/4-1BB agonist HERA-CD137L promotes anti-cancer immunity by activating CD8 T cells while regulatory T cells are not affected [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3754.

Abstract 630: Novel hexavalent HVEM agonist HERA-LIGHT promotes T cell activation and expansion

The tumor necrosis factor superfamily (TNFSF) member LIGHT (TNFSF14) plays an important role in regulating the activity of immune cells, especially T cells. Several studies have shown that engagement of HVEM (herpesvirus entry mediator), one of the known receptors of LIGHT, can deliver a co-stimulatory signal to support T cell activation and expansion and promote tumor clearance. The HERA technology platform developed by Apogenix generates fully human hexavalent TNFSF fusion proteins that mimic the natural receptor binding mode in order to co-stimulate T cells. HERA ligands are pure agonists whose signaling capacity does not rely on secondary Fcγ-receptor crosslinking. Here we report the in vitro and in vivo properties of a novel HERA-LIGHT construct. Similar to all HERA fusion proteins, HERA-LIGHT has been engineered as a perfect molecular mimic of the natural ligand with high clustering capacity for the cognate receptor. The core unit consists of a single chain polypeptide comprising the three minimal LIGHT-subsequences necessary for folding into a functional trivalent receptor binding domain (RBD). By fusing a silenced IgG1 Fc-domain as a dimerization scaffold to the C-terminus of the RBD we generated HERA-LIGHT, a hexavalent fusion protein. HERA-LIGHT was expressed in CHO suspension cells followed by a lab-scale purification process including AFC- and SEC-based polishing, resulting in homogenous, aggregate-free protein lots. HERA-LIGHT was proven to bind both the human and murine HVEM receptor, as determined by ELISA. Qualitative analytics revealed excellent stability following heat- and pH-stress as well as freeze-thaw cycles. Analyzing serum samples from a PK study in CD1-mice, the terminal half-life of the compound was 36.5 hours. This short half-life, relative to antibodies, allows for fast-in/fast-out dynamics essential for improving combination therapy and reducing serious side effects associated with immune system overstimulation. In order to test biological activity, T cells were isolated by magnetic sorting from human PBMCs and treated with HERA-LIGHT in vitro. Flow cytometric analysis revealed that HERA-LIGHT enhanced activation and proliferation of naïve effector T cells (Teff) following stimulation with anti-CD3 antibody, as determined by CFSE dilution. Importantly, co-stimulation with HERA-LIGHT prevented regulatory T cell (Treg)-mediated suppression of Teff proliferation. In vivo, treatment with a murine surrogate of HERA-LIGHT resulted in significant tumor growth inhibition in a pilot study using the syngeneic CT-26 colorectal cancer model.In summary, the unique hexavalent design of HERA-LIGHT mediates efficient co-stimulation of Teff even in the presence of Treg cells and independent of secondary crosslinking events. Being true agonists, all HERA molecules are unique from current antibody-based concepts rendering them attractive candidates for cancer immunotherapy.

Citation Format: Julian P. Sefrin, David M. Richards, Jaromir Sykora, Meinolf Thiemann, Christian Merz, Viola Marschall, Mauricio Redondo Müller, Karl Heinonen, Harald Fricke, Christian Gieffers, Oliver Hill. Novel hexavalent HVEM agonist HERA-LIGHT promotes T cell activation and expansion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 630.

The novel TRAIL-receptor agonist APG350 exerts superior therapeutic activity in pancreatic cancer cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has raised attention as a novel anticancer therapeutic as it induces apoptosis preferentially in tumor cells. However, first-generation TRAIL-receptor agonists (TRAs), comprising recombinant TRAIL and agonistic receptor-specific antibodies, have not demonstrated anticancer activity in clinical studies. In fact, cancer cells are often resistant to conventional TRAs. Therefore, in addition to TRAIL-sensitizing strategies, next-generation TRAs with superior apoptotic activity are warranted. APG350 is a novel, highly potent TRAIL-receptor agonist with a hexavalent binding mode allowing the clustering of six TRAIL-receptors per drug molecule. Here we report on preclinical in vitro and in vivo studies testing the activity of APG350 on pancreatic ductal adenocarcinoma (PDAC) cells. We found that APG350 potently induced apoptosis of Colo357, PancTuI and Panc89 cells in vitro. In addition, APG350 treatment activated non-canonical TRAIL signaling pathways (MAPK, p38, JNK, ERK1/ERK2 and NF-κB) and induced the secretion of IL-8. Stable overexpression of Bcl-xL inhibited APG350-induced cell death and augmented activation of non-canonical pathways. Intriguingly, pre-treatment of Bcl-xL-overexpressing cells with the BH3-mimic Navitoclax restored their sensitivity to APG350. To study the effects of APG350 on PDAC cells in vivo, we applied two different orthotopic xenotransplantation mouse models, with and without primary tumor resection, representing adjuvant and palliative treatment regimes, respectively. APG350 treatment of established tumors (palliative treatment) significantly reduced tumor burden. These effects, however, were not seen in tumors with enforced overexpression of Bcl-xL. Upon primary tumor resection and subsequent APG350 treatment (adjuvant therapy), APG350 limited recurrent tumor growth and metastases. Importantly, therapeutic efficacy of APG350 treatment was more effective compared with treatment with soluble TRAIL in both models. In conclusion, APG350 represents a promising next-generation TRA for the treatment of PDAC. Moreover, our results suggest that combining APG350 with Navitoclax might be a succesfull strategy for cancers harboring mitochondrial apoptosis resistance.

Abstract 4963: Novel hexavalent GITR agonists stimulate T cells and enhance memory formation

Introduction: The co-stimulatory receptor GITR plays an important role in initiating the immune response in the lymph nodes and in maintaining the immune response in the tumor tissue. Binding of GITR to its natural ligand directly leads to increased anti-tumor T cell activation and their survival. It also reduces the suppressive abilities of Treg cells, further increasing the anti-tumor immune response. The HERA-technology developed by Apogenix targets the TNF-receptor superfamily and generates fully human hexavalent fusion proteins with high clustering capacity for the cognate receptor. Hexavalent HERA-ligands are pure agonists whose signaling capacity is independent of secondary Fcγ-receptor crosslinking. Here we report in vitro and in vivo properties of novel hexavalent HERA-GITRL constructs.

Experimental procedures: For the assessment of in vivo stability, serum samples from a PK study with three HERA-GITRL constructs in CD1-mice were analyzed with respect to their drug levels employing a specific ELISA assay. For functional characterization of HERA-GITRL in vitro, immune cells were isolated from healthy-donor blood samples and profiled by multicolor flow cytometry (MC-FC). Subsequently, immune cells were cultured in growth media containing different HERA-GITRL constructs and anti-CD3. Changes in activation and memory markers on T cells (e.g. CD25, CD69, CD45RA, CD45RO), their proliferation rate (CFSE assay) and the intracellular staining of cytokines (e.g. TNF-α and IFN-γ) was assessed by MC-FC.

Results: Minor modifications led to three HERA-GITRL drug candidates with unique pharmacokinetic properties / in vivo stability as explored in mice. Terminal half-life was between 61.7 and 200.6 hours. Stimulation of pan T cells as well as naïve CD4+ T-lymphocytes by anti-CD3 was further augmented by HERA-GITRL as demonstrated by CD69 and CD25 expression. This effect was accompanied by an increased proliferation and an increased memory formation. Furthermore, we observed an increased level of intracellular TNF-α and IFN-γ in naïve CD4+ T-lymphocytes incubated with anti-CD3 that could be further raised by the addition of HERA-GITRL.

Conclusion: HERA-GITRL demonstrate excellent in vivo stability. Their ability to enhance proliferation and activation of naïve CD4+ T cells and to induce memory formation render them as attractive candidates for immunotherapeutic treatments of cancer.

Citation Format: Meinolf Thiemann, Christian Gieffers, David M. Richards, Christian Merz, Karl Heinonen, Mauricio Redondo Mueller, Viola Marschall, Jaromir Sykora, Harald Fricke, Oliver Hill. Novel hexavalent GITR agonists stimulate T cells and enhance memory formation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4963. doi:10.1158/1538-7445.AM2017-4963

Abstract 1688: HERA-CD40L: A novel hexavalent CD40 agonist with superior biological activity

Introduction: Targeted therapeutics for cancer treatment are mostly developed as antibodies, however, the natural signaling complexes of the members of the TNF superfamily and their receptors consist of clusters of trimers. Consequently, most of these bivalent agonistic antibodies depend on Fc receptor mediated crosslinking for biological activity. The HERA-Technology developed by Apogenix generates hexavalent fusion proteins targeting the TNF-receptor superfamily with high clustering capacity for the cognate receptor, which overcomes this disadvantage of antibody-based drugs. Here we compared the efficacy of different CD40 agonist formats, including the novel HERA-CD40L and the functional consequences of differential receptor clustering.

Materials & Methods: Biological activity of CD40 agonists was compared using an engineered reporter cell line and by flow cytometric analysis of CD40-induced IκBα degradation in Ramos B cells. T lymphocytes and monocytes were isolated from buffy coats and expression of CD markers upon CD40 ligation was analysed by multicolor flow cytometry (MC-FC). Secretion of cytokines in response to CD40 ligation was determined by ELISA. Monitoring of T cell-induced killing of tumor cells in direct co-cultures employed a real-time cell analysis system (xCELLigence).

Results: Direct comparison of bivalent CD40 antibodies with trivalent CD40L and the hexavalent HERA-CD40L in two independent bioactivity assay formats demonstrated that only the hexavalent agonist was fully active without additional crosslinking. In contrast to HERA-CD40L, neither the bivalent agonistic CD40 antibody nor the trivalent CD40L were able to upregulate expression of activation markers on B cells or to induce secretion of proinflammatory cytokines such as IL-12 and TNFα by PBMCs. In vitro generated M2-macrophages acquired an M1 phenotype and enhanced proliferation of naïve CD4+ T cells in direct co-culture. Similarly, direct co-culture of CD4+ T cells with Ramos B cells in the presence of HERA-CD40L induced cytotoxic activity of CD4+ cells against tumor cells. The activating effect was dependent on cell-cell contacts and was not observed in indirect co-cultures. Importantly, only the hexavalent HERA-CD40L showed full biological activity without additional crosslinking.

Conclusion: The hexavalent CD40 agonist HERA-CD40L produced by Apogenix HERA-Technology platform triggers CD40 signaling on B cells and cells of the monocytic lineage, leads to direct cytolytic activation and proliferation of CD4+ T cells and shifts the M1/M2 balance towards proinflammatory conditions. Unlike bivalent CD40 antibodies or trivalent CD40L_ based agonists, the hexavalent HERA-CD40L forms highly clustered signaling complexes and thus exhibits superior biological activity over other agonistic formats without the need for Fc receptor mediated crosslinking.

Citation Format: Christian Merz, Jaromir Sykora, Meinolf Thiemann, Viola Marschall, Karl H. Heinonen, Harald Fricke, Christian Gieffers, Oliver Hill. HERA-CD40L: A novel hexavalent CD40 agonist with superior biological activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1688. doi:10.1158/1538-7445.AM2017-1688

Abstract 4690: Hexavalent CD27 agonists show single agent anti-tumor activity and enhanced memory formation in mouse syngeneic tumor models

Tumor necrosis factor receptor superfamily (TNFRSF) proteins are widely expressed by immune and tumor cells highlighting their importance in multiple locations and phases of the anti-tumor immune response. Apogenix has developed a proprietary technology platform for the construction of novel hexavalent TNFRSF agonists (HERA) for the treatment of cancer. HERA fusion proteins comprise a perfect molecular mimic of the TNFSF cytokine structure and are based on dimerization of trivalent single-chain TNFSF receptor-binding domains (scTNFSF-RBD) via a Fc-γ receptor (FcγR) binding deficient immunoglobulin Fc domain. As a result of this molecular design, HERA proteins are capable of clustering six receptors in a spatially well-defined manner. Signaling following treatment with the Apogenix HERA “scTNFSF-RBD-Fc fusion proteins” is entirely independent of secondary crosslinking through FcγRs that is required for many agonistic anti-TNFRSF antibodies. The HERA engineering concept has been successfully translated to TRAIL, GITRL, CD40L, LIGHT and CD27L resulting in agonists that are currently in development. CD27L is a potent co-stimulatory molecule that drives T cell activation and survival through interaction with its receptor (CD27). HERA-CD27L is expressed in CHO suspension cells followed by a lab-scale purification process that results in homogenous aggregate-free protein lots. The purified protein binds its respective target-receptor with high affinity. In vitro, HERA-CD27L was able to bind CD27 expressed on primary human CD4+ and CD8+ T cells. Binding significantly increased T cell expansion following αCD3/αCD28 stimulation and leads to increased expression of OX40 on CD4+ T cells and 4-1BB on CD8+ T cells, respectively. In vivo, a single dose of 10mg/kg HERA-CD27L increases clonal expansion of antigen-specific CD8+ T cells upon immunization with Ovalbumin (Ova) in the mouse OT-1 model with a kinetics leading to peak levels of &gt;25% Ova-specific CD8+ T cells at day 6 after treatment. Anti-tumor efficacy of HERA-CD27 was evaluated in MC38-CEA and CT26 colorectal syngeneic murine tumor models. In both models treatment with HERA-CD27L resulted in a dose dependent inhibition of tumor growth. CT26 tumor bearing mice treated with 1mg/kg HERA-CD27L, twice weekly showed an 85% tumor-growth inhibition (TGI) compared to the control group. A significant TGI of 48% could be observed in the MC38-CEA model upon treatment with 10mg/kg, twice weekly. Analysis of peripheral lymphoid tissues in the MC38-CEA bearing mice could furthermore show that HERA-CD27L treatment is accompanied with enhanced memory formation in both CD4+ & CD8+ T cells. In summary, the data on the hexavalent HERA-CD27L indicate a potent immune cell driven anti tumor efficacy. Therefore, HERA-CD27 agonists could be applied for the treatment of cancer as a single agent or in combination with check-point Inhibitors.

Citation Format: Christian Gieffers, David Richards, Jaromir Sykora, Mauricio Redondo-Müller, Meinolf Thiemann, Christian Merz, Karl Heinonen Heinonen, Viola Marschall, Harald Fricke, Oliver Hill. Hexavalent CD27 agonists show single agent anti-tumor activity and enhanced memory formation in mouse syngeneic tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4690. doi:10.1158/1538-7445.AM2017-4690

Abstract A83: Hexavalent agonists targeting co-stimulatory receptors of the tumor necrosis factor superfamily

Tumor necrosis factor receptor superfamily (TNFRSF) proteins are widely expressed by immune and tumor cells highlighting their importance in multiple locations and phases of the anti-tumor immune response. Whereas agonistic stimulation of TRAIL-Receptor-1 or -2 can directly induce apoptosis in tumor cells, signaling through many TNFRSF members, such as CD40, CD27, OX40, HVEM, GITR and 4-1BB, results in co-stimulation of immune cells. Therefore, agonistic stimulation of certain members of the TNFRSF is considered to have a positive impact on immune-based therapeutic concepts in clinical oncology. Apogenix has developed a proprietary technology platform for the construction of novel hexavalent TNFRSF agonists (HERA) for the treatment of cancer. HERA fusion proteins are based on a perfect molecular mimic of the TNFSF cytokine structure. The HERA core unit consists of one single polypeptide chain comprising the three receptor-binding domain-forming subsequences (TNFSF-protomers). These single-chain TNFSF receptor-binding domains (scTNFSF-RBD) preserve the structural organization of the trimeric natural TNFSF cytokine and can be utilized to engineer fully human fusion-proteins in a modular manner. Fusing an IgG1 Fc-domain as a dimerization scaffold to the C-terminus of a scTNFSF-RBD creates a hexavalent agonist from two trivalent scTNFSF-RBDs. As a result of this molecular design, each molecule is capable of clustering six receptors in a spatially well-defined manner in close proximity to each other. Therefore, signaling following treatment with the Apogenix HERA scTNFSF-RBD-Fc fusion proteins in vivo is independent of secondary clustering through Fc-γ receptors that is required for many agonistic anti-TNFRSF antibodies (e.g., anti-TRAIL-R2 or anti-CD40). The described HERA engineering concept has been successfully translated to TRAIL, CD40L, LIGHT and CD27L resulting in hexavalent agonists suitable for further development. CD27-Ligand is a potent co-stimulatory molecule that drives T-cell activation and survival through interaction with its receptor (CD27). Here we show in vitro and in vivo data for APG1293 (scCD27L-RBD-Fc), a hexavalent CD27 agonist. APG1293 was expressed in CHO suspension cells followed by a lab-scale purification process including affinity chromatography and SEC-based polishing, resulting in homogenous aggregate-free protein lots. The purified protein binds its respective target-receptor with high affinity. In vivo stability/PK studies have been performed in addition to in vitro experiments with primary human and mouse lymphoid and myeloid cell populations. Specifically, APG1293 was able to bind CD27 expressed on primary human CD4+ and CD8+ T cells and importantly, binding significantly increased T-cell expansion following activation. In vivo the efficacy of APG1293 was evaluated in the colorectal syngeneic murine tumor models MC38-CEA and CT26. In both models APG1293 treatment resulted in a dose dependent tumor growth inhibition. In summary, the data on the hexavalent APG1293 indicate a potent immune cell driven anti tumor efficacy. Therefore, APG1293 could be applied as a single agent or in combination with check-point inhibitors.

Citation Format: Christian Gieffers, Christian Merz, David Richards, Mauricio Redondo, Viola Marschall, Jaromir Sykora, Meinolf Thiemann, Harald Fricke, Oliver Hill. Hexavalent agonists targeting co-stimulatory receptors of the tumor necrosis factor superfamily. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2016 Oct 20-23; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2017;5(3 Suppl):Abstract nr A83.

Abstract B48: Structure to function: comparison of CD40 agonist formats reveals superior immune-modulating properties of hexavalent scCD40L-RBD-Fc fusion protein APG1233

Introduction: Initiation and perpetuation of anti-tumor responses of the immune system are in the focus of current approaches to fight cancer. Manipulation of the tumor microenvironment, e.g. shifting the M1/M2 ratio towards M1 is one goal to support immunologic cancer treatment. Here we examined and compared the functional effects of bivalent agonistic anti-CD40 antibodies, homo-trimeric trivalent CD40-Ligand and the novel hexavalent CD40-agonist APG1233 on the maturation and differentiation of primary monocytes, B cells and T cell mediated tumor cell killing.

Materials and Methods: Following treatment with various CD40 agonists, cytokine secretion by monocytes, PBMCs and T cells from blood samples was assessed by ELISA. Monocytes isolated from healthy-donor blood samples were differentiated in vitro into either M1- or M2-type macrophages, or dendritic cells (DC) which was confirmed by multicolor flow-cytometry (MC-FC). Subsequently, we analyzed the respective M1- and M2-type macrophages and DCs regarding their ability to induce proliferation in a direct allogenic co-culture system with naïve CD4-positive T cells by a flow cytometry-based CFSE-assay. Macrophage plasticity, e.g. re-polarisation of M2-like to M1-like macrophages upon exposure to CD40 agonists was assessed by MC-FC. A real-time cell analysis system (Roche xCelligence RTCA DP) was used to attest T cell activation by CD40 stimulated B cells, resulting in killing of tumor cells in direct co-cultures.

Results: Stimulation of CD40 on PBMCs, T cells and monocytes increased secretion of cytokines (e.g. IL-12, TNFαa, CCL4) dependent on the agonist format and moreover was strictly dependent on Fc-crosslinking when using agonistic anti-CD40 mAb. In vitro, when the hexavalent APG1233 was added to the cytokine cocktail during the in vitro differentiation process, the appearance of M1-type macrophages was substantially increased. Moreover, M2-macrophages underwent conversion and acquired M1-type surface markers after exposure to APG1233. Finally, in direct co-culture of the in vitro differentiated cell populations with naïve CD4+ T cells, M1-macrophages induced strong lymphocyte proliferation, while the induction by monocytes and M2-macrophages was low. On a functional level, T lymphocytes co-cultured with M1 or DC acquired direct cytotoxic activity against tumor cells in a real-time cell analysis assay. Similarly, induction of cytolytic activity of purified T cells in vitro required the presence of both CD40 expressing B cells and APG1233.

Conclusion: Stimulation of CD40 on immune cells triggers development of anti-tumor responses, but efficacy of various agonist formats dramatically varies. Compared to trimeric CD40L formats and agonistic anti-CD40 mAbs, the novel hexavalent CD40 agonist APG1233 emerging from Apogenix HERA Technology platform excels as a strong inducer of B cell activation, M1-type macrophage differentiation and M2-&gt;M1 conversion. M1-macrophages generated in vitro are functional and enhance proliferation of naïve CD4+ T cells. CD40 stimulation on a CD40 expressing B cell line enhances its ability to activate T cells and trigger an anti-tumor response.

Citation Format: Christian Merz, Jaromir Sykora, Thamara Beyer, Stefanie Knorn, Harald Fricke, Christian Gieffers, Oliver Hill, David M. Richards. Structure to function: comparison of CD40 agonist formats reveals superior immune-modulating properties of hexavalent scCD40L-RBD-Fc fusion protein APG1233. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2016 Oct 20-23; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2017;5(3 Suppl):Abstract nr B48.

Abstract B066: The hexavalent CD40 agonist APG1233 is a superior inducer of immune cell activation compared to trimeric formats or agonistic anti-CD40 antibodies

Introduction: The co-stimulatory receptor CD40 is strongly expressed on B cells, monocytes and antigen-presenting cells (APC). By promoting their maturation, activation and survival, CD40 signaling greatly contributes to anti-tumor responses of the immune system. The HERA-Technology developed by Apogenix is a powerful engineering platform for the production of modular fusion proteins targeting the TNF-receptor superfamily. Structurally, these novel ligands comprise a single-chain arrangement of three TNFSF protomers forming one TNFSF-receptor binding domain (RBD) with specific linkers and the Fc-part of human IgG as dimerization scaffold. The result is a stable and defined hexavalent receptor agonist with high clustering capacity for the cognate receptor. Here we compared the efficacy of different CD40 agonist formats, including the novel hexavalent scCD40L-RBD-Fc (APG1233), and the functional consequences of differential receptor clustering. In addition, the in vivo pharmacokinetics of the fully human APG1233 is compared with a chimeric mouse/human surrogate molecule APG1274.

Materials and Methods: Immune cells were isolated from healthy-donor blood samples and profiled by multicolor flow cytometry (MC-FC). Subsequently, immune cells were cultured in growth media containing various forms of CD40 agonists. Upregulation of activation markers on B cells and monocytes (e.g. CD69, CD86, HLA-DR) and T cell-induced killing of tumor cells in direct co-culture was assessed by MC-FC and employing a real-time cell analysis system (xCELLigence), respectively. Secretion of cytokines in response to CD40 ligation and the pharmacokinetic properties of the fully human APG1233 and the chimeric murine/human APG1274 were determined by ELISA.

Results: In vivo stability of APG1233 was demonstrated in a single dose mouse PK study revealing a terminal half-life of 84 hours. The human CD40L, however, does not bind murine CD40. Therefore, we used APG1274, a chimeric protein comprising the murine CD40L fused to human IgG and binding to mouse CD40, to determine serum pharmacokinetics. As a result of functional binding of APG1274 to murine CD40, the surrogate molecule is eliminated much quicker (t1/2 of 4 hours) demonstrating the specificity of both compounds. In vitro only the hexavalent APG1233 displayed activity in terms of stimulation of B cells, monocytes and PBMCs. In contrast, neither trimeric CD40L nor an agonistic antibody against CD40 were able to upregulate expression of activation markers. Similarly, the secretion of proinflammatory cytokines such as IL-12, CD95L and IFNγ by PBMCs was only stimulated after exposure to APG1233 and not in the presence of other CD40 agonists. In functional co-culture assays, after exposure to APG1233, in vitro generated M2-macrophages underwent conversion and acquired M1-type surface markers which strongly enhanced proliferation of naïve CD4+ T cells. Induction by M2-macrophages in this setup was much lower. Consistent with these data, only the hexavalent CD40 agonist APG1233 efficiently increased direct cytotoxic activity of immune cells against tumor cells measured by a real-time cell analysis assay.

Conclusion: The CD40 agonist APG1233 is a member of a novel class of hexavalent TNFRSF agonists which binds its target with high specificity, exhibits excellent in vivo stability and superior biological activity over other agonistic formats (e.g. agonistic antibodies).

Citation Format: Christian Merz, Jaromir Sykora, Meinolf Thiemann, David M. Richards, Thamara Beyer, Stefanie Kühn, Harald Fricke, Christian Gieffers, Oliver Hill. The hexavalent CD40 agonist APG1233 is a superior inducer of immune cell activation compared to trimeric formats or agonistic anti-CD40 antibodies [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr B066.

Abstract 1204: A construction platform for hexavalent agonists targeting receptors of the tumor necrosis factor superfamily: Where death meets co-stimulation

Tumor necrosis factor receptor superfamily (TNFRSF) proteins are widely expressed by immune and tumor cells. Their importance in many locations and phases of the anti-tumor immune response is now broadly appreciated and several TNFR agonists are currently in preclinical and clinical development. Importantly, signaling through many TNFRSF members, such as CD40, CD27, OX40, 4-1BB, HVEM and GITR, is potentially associated with an enhanced anti tumor response via co-stimulation of immune cells.

Apogenix has established a development platform for a novel class of TNFRSF-agonists for the treatment of cancer. Unlike their natural homotrimeric counterparts, the Apogenix recombinant TNFSF proteins consist of one single polypeptide chain composed of three receptor-binding domain-forming protomers. These single-chain TNFSF receptor-binding domains (scTNFSF-RBD) are mimics of the three-dimensional organization of the natural TNFSF-cytokine and can be used to engineer fully human fusion-proteins from a modular toolbox. For example, fusing an IgG1 Fc-domain to the C-terminus of a scTNFSF-RBD creates a hexavalent agonist as the Fc-domain acts as a dimerization scaffold for two trivalent scTNFSF-RBDs. As a result of this molecular design, each drug molecule is capable of clustering six receptors in a spatially well-defined manner. Consequently, TNFSF receptor signaling following treatment with the Apogenix scTNFSF-RBD-Fc in vivo is independent of secondary clustering through Fc-γ receptors that is required for many anti-TNFRSF agonistic antibodies (e.g., anti-TRAILR2 or -CD40).

Following up the scTRAIL-RBD-Fc prototype, this engineering concept has now been successfully translated to CD40L and CD27L resulting in hexavalent agonists suitable for further development. Expression of the drug candidates in CHO suspension cells followed by an AFC and SEC-based lab-scale purification process resulted in homogenous aggregate-free protein lots. The purified proteins bind their respective target-receptors with high affinity. In vivo stability/PK studies have been performed in addition to in vitro experiments with primary human and mouse lymphoid and myeloid cell populations. Specifically, it was shown that scCD27L-RBD-Fc was able to bind CD27 expressed on primary human CD4+ and CD8+ T cells. Importantly, binding significantly increased T cell expansion following activation. Treatment with scCD40L-RBD-Fc induced differentiation of B cells and enhanced primary human monocyte differentiation into DCs or M1 macrophages.

Encouraged by the promising results obtained with TRAIL, CD40L, and CD27L, Apogenix is currently expanding the TNFRSF-agonist pipeline to target additional cell populations, locations and phases of the immune response in order to develop novel therapies to treat cancer and other conditions.

Citation Format: Christian Merz, Christian Gieffers, Michael Kluge, David M. Richards, Tim Schnyder, Jaromir Sykora, Meinolf Thiemann, Harald Fricke, Oliver Hill. A construction platform for hexavalent agonists targeting receptors of the tumor necrosis factor superfamily: Where death meets co-stimulation. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1204.

CD95 promotes metastatic spread via Sck in pancreatic ductal adenocarcinoma

Cancer stem cells (CSCs) have been implicated in the initiation and maintenance of tumour growth as well as metastasis. Recent reports link stemness to epithelial–mesenchymal transition (EMT) in cancer. However, there is still little knowledge about the molecular markers of those events. In silico analysis of RNA profiles of 36 pancreatic ductal adenocarcinomas (PDAC) reveals an association of the expression of CD95 with EMT and stemness that was validated in CSCs isolated from PDAC surgical specimens. CD95 expression was also higher in metastatic pancreatic cells than in primary PDAC. Pharmacological inhibition of CD95 activity reduced PDAC growth and metastasis in CSC-derived xenografts and in a murine syngeneic model. On the mechanistic level, Sck was identified as a novel molecule indispensable for CD95's induction of cell cycle progression. This study uncovers CD95 as a marker of EMT and stemness in PDAC. It also addresses the molecular mechanism by which CD95 drives tumour growth and opens tantalizing therapeutic possibilities in PDAC.

APG350 induces superior clustering of TRAIL receptors and shows therapeutic antitumor efficacy independent of cross-linking via Fcγ receptors

Cancer cells can be specifically driven into apoptosis by activating Death-receptor-4 (DR4; TRAIL-R1) and/or Death-receptor-5 (DR5; TRAIL-R2). Albeit showing promising preclinical efficacy, first-generation protein therapeutics addressing this pathway, especially agonistic anti-DR4/DR5-monoclonal antibodies, have not been clinically successful to date. Due to their bivalent binding mode, effective apoptosis induction by agonistic TRAIL-R antibodies is achieved only upon additional events leading to antibody-multimer formation. The binding of these multimers to their target subsequently leads to effective receptor-clustering on cancer cells. The research results presented here report on a new class of TRAIL-receptor agonists overcoming this intrinsic limitation observed for antibodies in general. The main feature of these agonists is a TRAIL-mimic consisting of three TRAIL-protomer subsequences combined in one polypeptide chain, termed the single-chain TRAIL-receptor-binding domain (scTRAIL-RBD). In the active compounds, two scTRAIL-RBDs with three receptor binding sites each are brought molecularly in close proximity resulting in a fusion protein with a hexavalent binding mode. In the case of APG350-the prototype of this engineering concept-this is achieved by fusing the Fc-part of a human immunoglobulin G1 (IgG1)-mutein C-terminally to the scTRAIL-RBD polypeptide, thereby creating six receptor binding sites per drug molecule. In vitro, APG350 is a potent inducer of apoptosis on human tumor cell lines and primary tumor cells. In vivo, treatment of mice bearing Colo205-xenograft tumors with APG350 showed a dose-dependent antitumor efficacy. By dedicated muteins, we confirmed that the observed in vivo efficacy of the hexavalent scTRAIL-RBD fusion proteins is-in contrast to agonistic antibodies-independent of FcγR-based cross-linking events.

Abstract 3856: Dimerized single chain TRAIL-receptor agonists do not depend on Fc-gamma-receptor cross-linking for anti-tumor efficacy in vivo

APG350 is a TRAIL-receptor (TRAIL-R) agonist comprising two single-chain TRAIL-R binding domains (scTRAIL-RBD) that are dimerized via the Fc-part of a human IgG1-mutein thereby creating six receptor binding sites per molecule. This improved ability to form clusters on target cells composed of six TRAIL-Rs each, distinguishes APG350 from current clinical development candidates. In vitro, comparison of APG350 with recombinant APO2L/TRAIL and a TRAIL-R2 specific agonistic antibody revealed superior apoptosis induction for APG350 on primary and established human tumor cell-lines. Treatment of mice bearing Colo205 xenograft tumors with APG350, APO2L/TRAIL or an agonistic TRAIL-R2 specific antibody showed superior anti-tumor efficacy for APG350. Pronounced anti tumor efficacy was also shown on colon cancer stem cell (CSC) derived xenografts and successful APG350 re-treatment of relapsed CSC derived tumors demonstrated that tumors did not develop drug resistance. For most agonistic TRAIL-R antibodies effective apoptosis induction is achieved only upon additional cross-linking. SEC-based fractionation of a TRAIL-R2 specific agonistic antibody indicates a small amount of multimerized antibody that showed efficient apoptosis induction in vitro. However, the respective monomeric antibody showed poor apoptosis induction in vitro that could be enhanced upon cross-linking. In contrast apoptosis induction by APG350 was only marginally enhanced by cross-linking. Although monomeric agonistic TRAIL-R antibodies are poor apoptosis inducers in vitro, they show efficient apoptosis induction on xenograft tumors in vivo. A likely explanation for this difference is given by a recent publication showing that anti-tumor efficacy of an agonistic TRAIL-R2 specific antibody (Drozitumab) depends on cross-linking by Fcα-receptors (FcαR) in vivo. These data suggest that FcαR cross-linking might be a common requirement for the anti-tumor efficacy of agonistic TRAIL-R antibodies. To exclude that in vivo efficacy of APG350 depends on cross-linking by FcαRs we designed APG350-muteins with strongly reduced (APG808) or lacking FcαR binding (APG780). Side by side comparison of APG808, APG780 and APG350 in mice bearing Colo205-derived xenograft tumors showed identical anti-tumor efficacy for all respective proteins. Given that APG780 cannot bind to FcαRs these results suggest that the anti-tumor efficacy of APG808, APG780 and APG350 is solely based on the unique construction principle of the dimerized scTRAIL-RBD. APG350 induces superior clustering of TRAIL-Rs that in contrast to agonistic TRAIL-R antibodies does not require cross-linking via FcαRs for its potent anti-tumor efficacy. APG350 based dimerized scTRAIL-RBD formats may therefore have the capacity to bridge the current gap seen between preclinical and clinical efficacy for agonistic TRAIL-R specific antibodies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3856. doi:1538-7445.AM2012-3856

Abstract LB-382: Inhibition of CD95 signalling by APG-101 enhances efficacy of radiotherapy (RT) and reduces RT-induced tumor satellite formation

CD95 is a prototype death receptor that regulates the induction of apoptosis, upon binding of its ligand CD95L. Therefore, activation of the CD95L/CD95 system has been regarded an excellent target for treatment of various malignancies. In contrast to the aim of promoting CD95 activation, there is compelling evidence that CD95 is able to promote tumor growth through intracellular non-apoptotic signalling mechanisms. This mechanism has recently been described for glioblastoma, in which activation of CD95 by CD95L leads to invasive growth and glioma cell migration. This is signalled through increased activity of pivotal glioblastoma invasion-related proteases, that is matrix metalloproteinases (MMP). With this shift of paradigms, blocking of the CD95L mediated invasion of tumor cells and subsequent tumor progression may therefore be a promising approach in anti-glioma therapy. APG101 is a fusion protein, consisting of the extracellular domain of human CD95 and the Fc-region of human immunoglobulin G. Hence, it acts as a soluble CD95 receptor trapping the CD95 ligand.

The presented project aims at analyzing the clinical relevance of blocking CD95 signalling, given the fact that glioma patients with upregulated CD95 expression have worse survival rates than those with intermediate expression levels. In proof-of principle experiments APG101 inhibits CD95L-mediated invasion of glioma cells. More importantly, APG101-treatment (100 mg/kg body weight) resulted in significantly prolonged survival of SMA560-tumor bearing Vm/Dk mice, less glioma cell satellites in the surrounding tissue and reduced activity of MMP. APG101 in combination with focal irradiation at 6 Gy demonstrated a remarkable reduction of tumor growth with a significantly prolonged survival compared with irradiation treatment alone and inhibition of the proinvasive properties of radiotherapy as demonstrated by magnetic resonance imaging and histology. Surprisingly, APG-101 added to the vascular endothelial growth factor receptor (VEGFR) inhibitor cediranib (AZD2171) did not increase the survival of SMA-560-tumor bearing mice as compared to cediranib alone nor did it impair the proinvasive consequences of cediranib.

Our data strongly support the potential use and clinical evaluation of APG101 in combination with radiotherapy in the treatment of malignant glioma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-382. doi:10.1158/1538-7445.AM2011-LB-382

Abstract LB-232: APG350, a dimerized single chain TRAIL receptor agonist with enhanced functional properties

TRAIL (Apo2L) is a member of the Tumor Necrosis Factor Superfamily (TNF-SF) that induces apoptosis through binding to two closely related receptors, TRAIL-R1 and TRAIL-R2. Its unique ability of selective apoptosis induction in tumor cells makes TRAIL an attractive molecule for tumor therapy.

APG350 is a newly designed TRAIL-receptor agonist comprising two single-chain TRAIL-receptor binding domains (each consisting of three covalently linked TRAIL protomers) that are dimerized via the Fc-part of human IgG1. APG350 has six receptor binding sites per molecule and binds to both death inducing TRAIL receptors. In vitro, APG350 shows potent apoptosis induction on a wide subset of human tumor cell-lines, on cancer stem cells and on primary tumor cells. Mechanistically its improved ability to form clusters on target cells composed of six TRAIL-receptors each, distinguishes APG350 from current clinical development candidates. Agonistic antibodies like Conatumumab or Apomab are capable to bind two receptor chains per molecule, while recombinant TRAIL (e.g. Dulanermin) binds three receptor chains per molecule. Direct in vitro comparison of APG350 with recombinant TRAIL (APG400) and a TRAIL-R2 specific agonistic monoclonal antibody revealed superior apoptosis induction capacity for APG350.

Analysis of the PK-parameters in mice showed a half life of 23.1h for APG350 (1.04h for APG400) indicating a significantly improved PK in comparison to APG400. The half life of APG350 in a Cynomolgus monkey was 26.7h.

Comparative treatment of mice bearing Colo205 xenograft tumors with APG350 and APG400 employing one treatment cycle with five consecutive daily intravenous injections showed a superior efficacy of APG350 with respect to tumor volume reduction and number of tumor free animals. Even mice with initially large tumors (∼600 mm3) were treated effectively with APG350. Remarkably, APG350 also showed pronounced dose dependent anti tumor efficacy on xenograft-tumors derived from colon cancer stem cells (CSC). Furthermore large CSC-derived tumors could be treated effectively and successful re-treatment of previously responding tumors demonstrated that tumors did not gain drug resistance. In a pilot experiment APG350 treatment of mice bearing a slowly growing primary rectum tumor xenograft also showed a significant tumor volume reduction. In all in vivo studies APG350 was well tolerated at doses between 0.3–100mg/kg bw in mice and doses up to 10mg/kg bw in a Cynomolgus monkey. General tolerability and potential effects on liver toxicity were assessed by co-application of APG350 together with a crosslinking antibody in mice. This treatment evoked only minor clinical signs at high doses with no relevant increase in liver enzymes. Currently two non-GLP toxicology studies, a 4-week study in mice and a dose escalation study in Cynomolgus monkeys are ongoing to confirm tolerability in vivo.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-232. doi:10.1158/1538-7445.AM2011-LB-232

Abstract LB-273: Inhibition of CD95-dependent signaling for the treatment of glioblastoma multiforme

CD95 (APO-1/FAS) is a receptor that belongs to the Tumor Necrosis Factor Super Family (TNFSF). Binding of the cognate ligand (CD95L) to CD95 triggers intracellular signaling, ultimately leading to apoptotic cell death. Recent research indicates that CD95 depending on the tissue and the conditions also mediates diverse non-apoptotic functions (e.g. liver regeneration, neuronal development, inflammation and cellular migration/invasion of tumor cells). The potential impact on multiple cellular processes classifies the CD95 pathway as an attractive target for pharmacological interference.

Apogenix developed APG101 a human fusion protein consisting of the extracellular domain of the CD95 receptor and the Fc-domain of an IgG antibody. APG101 can be used for the treatment of patho-physiological conditions showing an excess of CD95 induced apoptosis (e.g. acute Graft versus Host Disease, [GvHD]) and for malignancies that depend on CD95 regulated cell migration/invasion (e.g. cancer). Comprehensive, preclinical studies have demonstrated the therapeutic potential of APG101 in Glioblastoma Multiforme (GBM) and aGvHD.

GBM is a malignant astrocytic tumor that is highly resistant to radiation and chemotherapy induced apoptosis. A major reason for the particular poor prognosis of GBM is the diffuse invasive growth of infiltrating tumor cell into the surrounding brain. These infiltrating tumor cells evade surgery and are a major cause for tumor relapse. For this reason treatment regimens inhibiting the invasive phenotype should be beneficial for the treatment of GBM. It was shown recently that binding of CD95L to its cognate receptor is an important trigger for the invasive growth of glioblastoma cells and that inhibition of CD95 signaling with neutralizing antibodies abolished the invasion of glioblastoma in vitro and in vivo. Data presented here indicate that APG101 is capable to interfere with the invasive phenotype of glioblastoma cell lines in vitro. Furthermore APG101 effectively reduced the migration of invading tumor cells in a syngeneic mouse model of intracranial GBM (SMA-model). In a modified experimental setup the SMA-mouse model was additionally tested for the efficacy of a combinatorial treatment of APG101 and irradiation. These experiments revealed that a combination of APG101 and sub-lethal irradiation inhibits the invasive growth of GBM cells in vivo, whereas radiation alone had no effect on invasive growth. Detailed analysis of the treatment groups indicated that the combination of APG101 and sub-lethal irradiation prevents formation of satellite tumors, an effect that could not be observed in the control groups. Based on the preclinical data set presented, APG101 is currently tested in a clinical Phase II for the treatment of GBM.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-273.

Yes and PI3K bind CD95 to signal invasion of glioblastoma

Invasion of surrounding brain tissue by isolated tumor cells represents one of the main obstacles to a curative therapy of glioblastoma multiforme. Here we unravel a mechanism regulating glioma infiltration. Tumor interaction with the surrounding brain tissue induces CD95 Ligand expression. Binding of CD95 Ligand to CD95 on glioblastoma cells recruits the Src family member Yes and the p85 subunit of phosphatidylinositol 3-kinase to CD95, which signal invasion via the glycogen synthase kinase 3-beta pathway and subsequent expression of matrix metalloproteinases. In a murine syngeneic model of intracranial GBM, neutralization of CD95 activity dramatically reduced the number of invading cells. Our results uncover CD95 as an activator of PI3K and, most importantly, as a crucial trigger of basal invasion of glioblastoma in vivo.

Localization of the coactivator Cdh1 and the cullin subunit Apc2 in a cryo-electron microscopy model of vertebrate APC/C

The anaphase-promoting complex/cyclosome (APC/C) is a ubiquitin ligase with essential functions in mitosis, meiosis, and G1 phase of the cell cycle. APC/C recognizes substrates via coactivator proteins such as Cdh1, and bound substrates are ubiquitinated by E2 enzymes that interact with a hetero-dimer of the RING subunit Apc11 and the cullin Apc2. We have obtained three-dimensional (3D) models of human and Xenopus APC/C by angular reconstitution and random conical tilt (RCT) analyses of negatively stained cryo-electron microscopy (cryo-EM) preparations, have determined the masses of these particles by scanning transmission electron microscopy (STEM), and have mapped the locations of Cdh1 and Apc2. These proteins are located on the same side of the asymmetric APC/C, implying that this is where substrates are ubiquitinated. We have further identified a large flexible domain in APC/C that adopts a different orientation upon Cdh1 binding. Cdh1 may thus activate APC/C both by recruiting substrates and by inducing conformational changes.

Mitotic regulation of the human anaphase-promoting complex by phosphorylation

The anaphase-promoting complex (APC) or cyclosome is a ubiquitin ligase that initiates anaphase and mitotic exit. APC activation is thought to depend on APC phosphorylation and Cdc20 binding. We have identified 43 phospho-sites on APC of which at least 34 are mitosis specific. Of these, 32 sites are clustered in parts of Apc1 and the tetratricopeptide repeat (TPR) subunits Cdc27, Cdc16, Cdc23 and Apc7. In vitro, at least 15 of the mitotic phospho-sites can be generated by cyclin-dependent kinase 1 (Cdk1), and 3 by Polo-like kinase 1 (Plk1). APC phosphorylation by Cdk1, but not by Plk1, is sufficient for increased Cdc20 binding and APC activation. Immunofluorescence microscopy using phospho-antibodies indicates that APC phosphorylation is initiated in prophase during nuclear uptake of cyclin B1. In prometaphase phospho-APC accumulates on centrosomes where cyclin B ubiquitination is initiated, appears throughout the cytosol and disappears during mitotic exit. Plk1 depletion neither prevents APC phosphorylation nor cyclin A destruction in vivo. These observations imply that APC activation is initiated by Cdk1 already in the nuclei of late prophase cells.

TPR subunits of the anaphase-promoting complex mediate binding to the activator protein CDH1

BACKGROUND

Chromosome segregation and mitotic exit depend on activation of the anaphase-promoting complex (APC) by the substrate adaptor proteins CDC20 and CDH1. The APC is a ubiquitin ligase composed of at least 11 subunits. The interaction of APC2 and APC11 with E2 enzymes is sufficient for ubiquitination reactions, but the functions of most other subunits are unknown.

RESULTS

We have biochemically characterized subcomplexes of the human APC. One subcomplex, containing APC2/11, APC1, APC4, and APC5, can assemble multiubiquitin chains but is unable to bind CDH1 and to ubiquitinate substrates. The other subcomplex contains all known APC subunits except APC2/11. This subcomplex can recruit CDH1 but fails to support any ubiquitination reaction. In vitro, the C termini of CDC20 and CDH1 bind to the closely related TPR subunits APC3 and APC7. Homology modeling predicts that these proteins are similar in structure to the peroxisomal import receptor PEX5, which binds cargo proteins via their C termini. APC activation by CDH1 depends on a conserved C-terminal motif that is also found in CDC20 and APC10.

CONCLUSIONS

APC1, APC4, and APC5 may connect APC2/11 with TPR subunits. TPR domains in APC3 and APC7 recruit CDH1 to the APC and may thereby bring substrates into close proximity of APC2/11 and E2 enzymes. In analogy to PEX5, the different TPR subunits of the APC might function as receptors that interact with the C termini of regulatory proteins such as CDH1, CDC20, and APC10.

Crystal structure of the APC10/DOC1 subunit of the human anaphase-promoting complex

The anaphase-promoting complex (APC), or cyclosome, is a cell cycle-regulated ubiquitin ligase that controls progression through mitosis and the G1 phase of the cell cycle. The APC is composed of at least 11 subunits; no structure has been determined for any of these subunits. The subunit APC10/DOC1, a one-domain protein consisting of 185 amino acids, has a conserved core (residues 22-161) that is homologous to domains found in several other putative ubiquitin ligases and, therefore, may play a role in ubiquitination reactions. Here we report the crystal structure of human APC10 at 1.6 A resolution. The core of the protein is formed by a beta-sandwich that adopts a jellyroll fold. Unexpectedly, this structure is highly similar to ligand-binding domains of several bacterial and eukaryotic proteins, such as galactose oxidase and coagulation factor Va, raising the possibility that APC10 may function by binding a yet unidentified ligand. We further provide biochemical evidence that the C-terminus of APC10 binds to CDC27/APC3, an APC subunit that contains multiple tetratrico peptide repeats.

Anaphase-promoting complex/cyclosome-dependent proteolysis of human cyclin A starts at the beginning of mitosis and is not subject to the spindle assembly checkpoint

Cyclin A is a stable protein in S and G2 phases, but is destabilized when cells enter mitosis and is almost completely degraded before the metaphase to anaphase transition. Microinjection of antibodies against subunits of the anaphase-promoting complex/cyclosome (APC/C) or against human Cdc20 (fizzy) arrested cells at metaphase and stabilized both cyclins A and B1. Cyclin A was efficiently polyubiquitylated by Cdc20 or Cdh1-activated APC/C in vitro, but in contrast to cyclin B1, the proteolysis of cyclin A was not delayed by the spindle assembly checkpoint. The degradation of cyclin B1 was accelerated by inhibition of the spindle assembly checkpoint. These data suggest that the APC/C is activated as cells enter mitosis and immediately targets cyclin A for degradation, whereas the spindle assembly checkpoint delays the degradation of cyclin B1 until the metaphase to anaphase transition. The "destruction box" (D-box) of cyclin A is 10-20 residues longer than that of cyclin B. Overexpression of wild-type cyclin A delayed the metaphase to anaphase transition, whereas expression of cyclin A mutants lacking a D-box arrested cells in anaphase.

Three-dimensional structure of the anaphase-promoting complex

The anaphase-promoting complex (APC) is a cell cycle-regulated ubiquitin-protein ligase, composed of at least 11 subunits, that controls progression through mitosis and G1. Using cryo-electron microscopy and angular reconstitution, we have obtained a three-dimensional model of the human APC at a resolution of 24 A. The APC has a complex asymmetric structure 140 A x 140 A x 135 A in size, in which an outer protein wall surrounds a large inner cavity. We discuss the possibility that this cavity represents a reaction chamber in which ubiquitination reactions take place, analogous to the inner cavities formed by other protein machines such as the 26S proteasome and chaperone complexes. This cage hypothesis could help to explain the great subunit complexity of the APC.

Characterization of vertebrate cohesin complexes and their regulation in prophase

In eukaryotes, sister chromatids remain connected from the time of their synthesis until they are separated in anaphase. This cohesion depends on a complex of proteins called cohesins. In budding yeast, the anaphase-promoting complex (APC) pathway initiates anaphase by removing cohesins from chromosomes. In vertebrates, cohesins dissociate from chromosomes already in prophase. To study their mitotic regulation we have purified two 14S cohesin complexes from human cells. Both complexes contain SMC1, SMC3, SCC1, and either one of the yeast Scc3p orthologs SA1 and SA2. SA1 is also a subunit of 14S cohesin in Xenopus. These complexes interact with PDS5, a protein whose fungal orthologs have been implicated in chromosome cohesion, condensation, and recombination. The bulk of SA1- and SA2-containing complexes and PDS5 are chromatin-associated until they become soluble from prophase to telophase. Reconstitution of this process in mitotic Xenopus extracts shows that cohesin dissociation does neither depend on cyclin B proteolysis nor on the presence of the APC. Cohesins can also dissociate from chromatin in the absence of cyclin-dependent kinase 1 activity. These results suggest that vertebrate cohesins are regulated by a novel prophase pathway which is distinct from the APC pathway that controls cohesins in yeast.

Cell cycle- and cell growth-regulated proteolysis of mammalian CDC6 is dependent on APC-CDH1

CDC6 is conserved during evolution and is essential and limiting for the initiation of eukaryotic DNA replication. Human CDC6 activity is regulated by periodic transcription and CDK-regulated subcellular localization. Here, we show that, in addition to being absent from nonproliferating cells, CDC6 is targeted for ubiquitin-mediated proteolysis by the anaphase promoting complex (APC)/cyclosome in G(1). A combination of point mutations in the destruction box and KEN-box motifs in CDC6 stabilizes the protein in G(1) and in quiescent cells. Furthermore, APC, in association with CDH1, ubiquitinates CDC6 in vitro, and both APC and CDH1 are required and limiting for CDC6 proteolysis in vivo. Although a stable mutant of CDC6 is biologically active, overexpression of this mutant or wild-type CDC6 is not sufficient to induce multiple rounds of DNA replication in the same cell cycle. The APC-CDH1-dependent proteolysis of CDC6 in early G(1) and in quiescent cells suggests that this process is part of a mechanism that ensures the timely licensing of replication origins during G(1).