Nuclear Factor κB is Required for Tumor Growth Inhibition Mediated by Enavatuzumab (PDL192), a Humanized Monoclonal Antibody to TweakR

Antibody-based soluble and membrane-bound TWEAK mimicking agonists with FcγR-independent activity

Fibroblast growth factor (FGF)-inducible 14 (Fn14) activates the classical and alternative NFκB (nuclear factor 'kappa-light-chain-enhancer' of activated B-cells) signaling pathway but also enhances tumor necrosis factor (TNF)-induced cell death. Fn14 expression is upregulated in non-hematopoietic cells during tissue injury and is also often highly expressed in solid cancers. In view of the latter, there were and are considerable preclinical efforts to target Fn14 for tumor therapy, either by exploiting Fn14 as a target for antibodies with cytotoxic activity (e.g. antibody-dependent cellular cytotoxicity (ADCC)-inducing IgG variants, antibody drug conjugates) or by blocking antibodies with the aim to interfere with protumoral Fn14 activities. Noteworthy, there are yet no attempts to target Fn14 with agonistic Fc effector function silenced antibodies to unleash the proinflammatory and cell death-enhancing activities of this receptor for tumor therapy. This is certainly not at least due to the fact that anti-Fn14 antibodies only act as effective agonists when they are presented bound to Fcγ receptors (FcγR). Thus, there are so far no antibodies that robustly and selectively engage Fn14 signaling without triggering unwanted FcγR-mediated activities. In this study, we investigated a panel of variants of the anti-Fn14 antibody 18D1 of different valencies and domain architectures with respect to their inherent FcγR-independent ability to trigger Fn14-associated signaling pathways. In contrast to conventional 18D1, the majority of 18D1 antibody variants with four or more Fn14 binding sites displayed a strong ability to trigger the alternative NFκB pathway and to enhance TNF-induced cell death and therefore resemble in their activity soluble (TNF)-like weak inducer of apoptosis (TWEAK), one form of the natural occurring ligand of Fn14. Noteworthy, activation of the classical NFκB pathway, which naturally is predominately triggered by membrane-bound TWEAK but not soluble TWEAK, was preferentially observed with a subset of constructs containing Fn14 binding sites at opposing sites of the IgG scaffold, e.g. IgG1-scFv fusion proteins. A superior ability of IgG1-scFv fusion proteins to trigger classical NFκB signaling was also observed with the anti-Fn14 antibody PDL192 suggesting that we identified generic structures for Fn14 antibody variants mimicking soluble and membrane-bound TWEAK.

Targeting fibroblast growth factor (FGF)-inducible 14 (Fn14) for tumor therapy

Fibroblast growth factor-inducible 14 (Fn14) is a member of the tumor necrosis factor (TNF) receptor superfamily (TNFRSF) and is activated by its ligand TNF-like weak inducer of apoptosis (TWEAK). The latter occurs as a homotrimeric molecule in a soluble and a membrane-bound form. Soluble TWEAK (sTWEAK) activates the weakly inflammatory alternative NF-κB pathway and sensitizes for TNF-induced cell death while membrane TWEAK (memTWEAK) triggers additionally robust activation of the classical NF-κB pathway and various MAP kinase cascades. Fn14 expression is limited in adult organisms but becomes strongly induced in non-hematopoietic cells by a variety of growth factors, cytokines and physical stressors (e.g., hypoxia, irradiation). Since all these Fn14-inducing factors are frequently also present in the tumor microenvironment, Fn14 is regularly found to be expressed by non-hematopoietic cells of the tumor microenvironment and most solid tumor cells. In general, there are three possibilities how the tumor-Fn14 linkage could be taken into consideration for tumor therapy. First, by exploitation of the cancer associated expression of Fn14 to direct cytotoxic activities (antibody-dependent cell-mediated cytotoxicity (ADCC), cytotoxic payloads, CAR T-cells) to the tumor, second by blockade of potential protumoral activities of the TWEAK/Fn14 system, and third, by stimulation of Fn14 which not only triggers proinflammtory activities but also sensitizes cells for apoptotic and necroptotic cell death. Based on a brief description of the biology of the TWEAK/Fn14 system and Fn14 signaling, we discuss the features of the most relevant Fn14-targeting biologicals and review the preclinical data obtained with these reagents. In particular, we address problems and limitations which became evident in the preclinical studies with Fn14-targeting biologicals and debate possibilities how they could be overcome.

NF-κB signaling and crosstalk during carcinogenesis

Transcription factors (TFs) are proteins that control the transcription of genetic information from DNA to mRNA by binding to specific DNA sequences either on their own or with other proteins as a complex. TFs thus support or suppress the recruitment of the corresponding RNA polymerase. In general, TFs are classified by structure or function. The TF, Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), is expressed in all cell types and tissues. NF-κB signaling and crosstalk are involved in several steps of carcinogenesis including in sequences involving pathogenic stimulus, chronic inflammation, fibrosis, establishment of its remodeling to the precancerous niche (PCN) and transition of a normal cell to a cancer cell. Triggered by various inflammatory cytokines, NF-κB is activated along with other TFs with subsequent stimulation of cell proliferation and inhibition of apoptosis. The involvement of NF-κB in carcinogenesis provides an opportunity to develop anti-NF-κB therapies. The complexity of these interactions requires that we elucidate those aspects of NF-κB interactions that play a role in carcinogenesis, the sequence of events leading to cancer.

Phase I Study of Enavatuzumab, a First-in-Class Humanized Monoclonal Antibody Targeting the TWEAK Receptor, in Patients with Advanced Solid Tumors

This phase I study evaluates the safety, MTD, pharmacokinetics (PK), pharmacodynamics, and preliminary anticancer activity of enavatuzumab, a humanized IgG1 antibody to the TWEAK receptor, in patients with advanced solid malignancies. Patients received escalating doses of enavatuzumab given intravenously over 60 minutes every 2 weeks. Blood was obtained for PK and biomarker assessment. Three patients were enrolled per dose level in a standard 3+3 design with response assessment by RECIST version 1.0, every 8 weeks. Thirty patients were enrolled at 6 dose levels ranging from 0.1 to 1.5 mg/kg. Dose-limiting toxicities included grade 4 (G4) lipase, G3 bilirubin, and G4 amylase elevations. There was no apparent correlation of liver or pancreatic enzyme elevation with drug exposure or the presence of liver metastases. Enavatuzumab exhibited a two-compartment linear PK model. Estimated systemic clearance was 23 to 33 mL/h with an elimination half-life of 7 to 18 days. The predicted target efficacious peak and trough concentrations occurred at 1.0 mg/kg following the second dose. There were no objective responses; 4 patients had stable disease. The MTD of enavatuzumab is 1.0 mg/kg i.v. every 2 weeks. Higher doses were not tolerated due to hepatopancreatic lab abnormalities. Further evaluation of the mechanisms of the liver and pancreatic enzyme toxicities is needed before embarking on further single-agent or combination strategies. Mol Cancer Ther; 17(1); 215-21. ©2017 AACR.

Enavatuzumab, a Humanized Anti-TWEAK Receptor Monoclonal Antibody, Exerts Antitumor Activity through Attracting and Activating Innate Immune Effector Cells

Enavatuzumab is a humanized IgG1 anti-TWEAK receptor monoclonal antibody that was evaluated in a phase I clinical study for the treatment of solid malignancies. The current study was to determine whether and how myeloid effector cells were involved in postulated mechanisms for its potent antitumor activity in xenograft models. The initial evidence for a role of effector cells was obtained in a subset of tumor xenograft mouse models whose response to enavatuzumab relied on the binding of Fc of the antibody to Fcγ receptor. The involvement of effector cells was further confirmed by immunohistochemistry, which revealed strong infiltration of CD45⁺ effector cells into tumor xenografts in responding models, but minimal infiltration in nonresponders. Consistent with the xenograft studies, human effector cells preferentially migrated toward in vivo-responsive tumor cells treated by enavatuzumab in vitro, with the majority of migratory cells being monocytes. Conditioned media from enavatuzumab-treated tumor cells contained elevated levels of chemokines, which might be responsible for enavatuzumab-triggered effector cell migration. These preclinical studies demonstrate that enavatuzumab can exert its potent antitumor activity by actively recruiting and activating myeloid effectors to kill tumor cells. Enavatuzumab-induced chemokines warrant further evaluation in clinical studies as potential biomarkers for such activity.

TWEAK activation of the non-canonical NF-κB signaling pathway differentially regulates melanoma and prostate cancer cell invasion

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) is a multifunctional cytokine that binds with high affinity to a plasma membrane-anchored receptor named Fn14. Both TWEAK and Fn14 expression has been detected in human cancer tissue, and studies have shown that TWEAK/Fn14 signaling can promote either "pro-cancer" or "anti-cancer" cellular effects in vitro, depending on the cancer cell line under investigation. In this study, we engineered murine B16 melanoma cells to secrete high levels of soluble TWEAK and examined their properties. TWEAK production by B16 cells preferentially activated the non-canonical NF-κB signaling pathway and increased the expression of several previously described TWEAK-inducible genes, including Fn14. TWEAK overexpression in B16 cells inhibited both cell growth and invasion in vitro. The TWEAK-mediated reduction in B16 cell invasive capacity was dependent on activation of the non-canonical NF-κB signaling pathway. Finally, we found that this same signaling pathway was also important for TWEAK-stimulated human DU145 prostate cancer cell invasion. Therefore, even though TWEAK:Fn14 binding activates non-canonical NF-κB signaling in both melanoma and prostate cancer cells, this shared cellular response can trigger a very different downstream outcome (inhibition or stimulation of cell invasiveness, respectively).

Principles of antibody-mediated TNF receptor activation

From the beginning of research on receptors of the tumor necrosis factor (TNF) receptor superfamily (TNFRSF), agonistic antibodies have been used to stimulate TNFRSF receptors in vitro and in vivo. Indeed, CD95, one of the first cloned TNFRSF receptors, was solely identified as the target of cell death-inducing antibodies. Early on, it became evident from in vitro studies that valency and Fcγ receptor (FcγR) binding of antibodies targeting TNFRSF receptors can be of crucial relevance for agonistic activity. TNFRSF receptor-specific antibodies of the IgM subclass and secondary cross-linked or aggregation prone dimeric antibodies typically display superior agonistic activity compared with dimeric antibodies. Likewise, anchoring of antibodies to cell surface-expressed FcγRs potentiate their ability to trigger TNFRSF receptor signaling. However, only recently has the relevance of oligomerization and FcγR binding for the in vivo activity of antibody-induced TNFRSF receptor activation been straightforwardly demonstrated in vivo. This review discusses the crucial role of oligomerization and/or FcγR binding for antibody-mediated TNFRSF receptor stimulation in light of current models of TNFRSF receptor activation and especially the overwhelming relevance of these issues for the rational development of therapeutic TNFRSF receptor-targeting antibodies.

Expression of TweakR in breast cancer and preclinical activity of enavatuzumab, a humanized anti-TweakR mAb

Background

The receptor for the cytokine TWEAK (TweakR) is a cell surface member of the tumor necrosis factor receptor superfamily with diverse biological roles. TNFRSF family members are appealing therapeutic targets in oncology due to their aberrant expression and function in tumor cells. The goal of the current study was to examine the potential of TweakR as a therapeutic target in breast cancer.

Methods

Expression of TweakR in primary breast cancer tissues and metastases was characterized using immunohistochemistry. To determine the functional relevance of TweakR, breast cancer cell lines were treated in vitro and in vivo with enavatuzumab, a humanized mAb against TweakR.

Results

Overexpression of TweakR was observed in infiltrating tumors compared to normal adjacent breast tissues, and strong staining of TweakR was observed in all subtypes of invasive ductal breast cancer. In addition, a positive correlation of TweakR and HER2 expression and co-localization were observed, irrespective of ER status. TweakR expression was also observed in bone metastasis samples from primary breast cancer but rarely in benign tumors. Enavatuzumab inhibited the in vitro growth of TweakR-expressing breast cancer cell lines, and this activity was augmented by cross-linking the mAb. In addition, enavatuzumab significantly inhibited the in vivo growth of multiple breast cancer xenograft models including a model of metastasis.

Conclusions

TweakR is highly expressed in all subtypes of invasive ductal breast cancer, and enavatuzumab administration exhibited a dose-dependent inhibition of primary tumor growth and lung metastasis and enhanced the antitumor activity of several chemotherapy agents currently used to treat breast cancer. These data provide the rationale to evaluate enavatuzumab as a potential therapy for the treatment of breast cancer.

Electronic supplementary material

The online version of this article (doi:10.1007/s00432-012-1332-x) contains supplementary material, which is available to authorized users.