Debra T. Chao

Elotuzumab enhances natural killer cell activation and myeloma cell killing through interleukin-2 and TNF-α pathways

Abstract Elotuzumab is a humanized monoclonal antibody specific for signaling lymphocytic activation molecule-F7 (SLAMF7, also known as CS1, CD319, or CRACC) that enhances natural killer (NK) cell-mediated antibody-dependent cellular cytotoxicity (ADCC) of SLAMF7-expressing myeloma cells. This study explored the mechanisms underlying enhanced myeloma cell killing with elotuzumab as a single agent and in combination with lenalidomide, to support ongoing phase III trials in patients with relapsed/refractory or newly-diagnosed multiple myeloma (MM). An in vitro peripheral blood lymphocyte (PBL)/myeloma cell co-culture model was developed to evaluate the combination of elotuzumab and lenalidomide. Expression of activation markers and adhesion receptors was evaluated by flow cytometry, cytokine expression by Luminex and ELISPOT assays, and cytotoxicity by myeloma cell counts. Elotuzumab activated NK cells and promoted myeloma cell death in PBL/myeloma cell co-cultures. The combination of elotuzumab plus lenalidomide demonstrated superior anti-myeloma activity on established MM xenografts in vivo and in PBL/myeloma cell co-cultures in vitro than either agent alone. The combination enhanced myeloma cell killing by modulating NK cell function that coincided with the upregulation of adhesion and activation markers, including interleukin (IL)-2Rα expression, IL-2 production by CD3+CD56+ lymphocytes, and tumor necrosis factor (TNF)-α production. In co-culture assays, TNF-α directly increased NK cell activation and myeloma cell death with elotuzumab or elotuzumab plus lenalidomide, and neutralizing TNF-α decreased NK cell activation and myeloma cell death with elotuzumab. These results demonstrate that elotuzumab activates NK cells and induces myeloma cell death via NK cell-mediated ADCC, which is further enhanced when combined with lenalidomide.

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

BackgroundThe 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.MethodsExpression 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.ResultsOverexpression 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.ConclusionsTweakR 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.

PDL241, a novel humanized monoclonal antibody, reveals CD319 as a therapeutic target for rheumatoid arthritis

IntroductionTargeting the CD20 antigen has been a successful therapeutic intervention in the treatment of rheumatoid arthritis (RA). However, in some patients with an inadequate response to anti-CD20 therapy, a persistence of CD20- plasmablasts is noted. The strong expression of CD319 on CD20- plasmablast and plasma cell populations in RA synovium led to the investigation of the potential of CD319 as a therapeutic target.MethodsPDL241, a novel humanized IgG1 monoclonal antibody (mAb) to CD319, was generated and examined for its ability to inhibit immunoglobulin production from plasmablasts and plasma cells generated from peripheral blood mononuclear cells (PBMC) in the presence and absence of RA synovial fibroblasts (RA-SF). The in vivo activity of PDL241 was determined in a human PBMC transfer into NOD scid IL-2 gamma chain knockout (NSG) mouse model. Finally, the ability of PDL241 to ameliorate experimental arthritis was evaluated in a collagen-induced arthritis (CIA) model in rhesus monkeys.ResultsPDL241 bound to plasmablasts and plasma cells but not naïve B cells. Consistent with the binding profile, PDL241 inhibited the production of IgM from in vitro PBMC cultures by the depletion of CD319+ plasmablasts and plasma cells but not B cells. The activity of PDL241 was dependent on an intact Fc portion of the IgG1 and mediated predominantly by natural killer cells. Inhibition of IgM production was also observed in the human PBMC transfer to NSG mouse model. Treatment of rhesus monkeys in a CIA model with PDL241 led to a significant inhibition of anti-collagen IgG and IgM antibodies. A beneficial effect on joint related parameters, including bone remodeling, histopathology, and joint swelling was also observed.ConclusionsThe activity of PDL241 in both in vitro and in vivo models highlights the potential of CD319 as a therapeutic target in RA.

LRRC15 is a novel mesenchymal protein and stromal target for antibody-drug conjugates.

Progress in understanding tumor stromal biology has been constrained in part because cancer-associated fibroblasts (CAF) are a heterogeneous population with limited cell-type-specific protein markers. Using RNA expression profiling, we identified the membrane protein leucine-rich repeat containing 15 (LRRC15) as highly expressed in multiple solid tumor indications with limited normal tissue expression. LRRC15 was expressed on stromal fibroblasts in many solid tumors (e.g., breast, head and neck, lung, pancreatic) as well as directly on a subset of cancer cells of mesenchymal origin (e.g., sarcoma, melanoma, glioblastoma). LRRC15 expression was induced by TGFβ on activated fibroblasts (αSMA+) and on mesenchymal stem cells. These collective findings suggested LRRC15 as a novel CAF and mesenchymal marker with utility as a therapeutic target for the treatment of cancers with LRRC15-positive stromal desmoplasia or cancers of mesenchymal origin. ABBV-085 is a monomethyl auristatin E (MMAE)-containing antibody-drug conjugate (ADC) directed against LRRC15, and it demonstrated robust preclinical efficacy against LRRC15 stromal-positive/cancer-negative, and LRRC15 cancer-positive models as a monotherapy, or in combination with standard-of-care therapies. ABBV-085s unique mechanism of action relied upon the cell-permeable properties of MMAE to preferentially kill cancer cells over LRRC15-positive CAF while also increasing immune infiltrate (e.g., F4/80+ macrophages) in the tumor microenvironment. In summary, these findings validate LRRC15 as a novel therapeutic target in multiple solid tumor indications and support the ongoing clinical development of the LRRC15-targeted ADC ABBV-085.Significance: These findings identify LRRC15 as a new marker of cancer-associated fibroblasts and cancers of mesenchymal origin and provide preclinical evidence for the efficacy of an antibody-drug conjugate targeting the tumor stroma. Cancer Res; 78(14); 4059-72. ©2018 AACR.

Abstract 2722: Active recruitment of immune effector cells mediates in vivo tumor growth inhibition by enavatuzumab, an antibody to human TWEAK receptor

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Enavatuzumab (PDL192) is a humanized anti-TWEAK receptor antibody currently under clinical evaluation for the treatment of solid malignancies. Enavatuzumab is postulated to exert its potent anti-tumor activity in xenograft models through two distinct mechanisms of action: direct inhibition of tumor cell growth and Fc-mediated function. The goal of this study was to elucidate the role of immune effector cells in Fc-mediated function. The initial evidence for a role of effector cells was obtained in a subset of tumor xenograft mouse models which responded to enavatuzumab but did not respond to a version of enavatuzumab containing a mutation in the FcαRIII binding region. Subsequent analysis of circulating effector cells showed increased expression of activation markers DX5 and CD27 on monocyte-like cells (CD45+CD11bHigh) and DX5 on NK-like cells (CD45+CD11bLow) after enavatuzumab treatment in xenograft models dependent on Fc-FcR interactions for enavatuzumab efficacy. 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 non-responders. Consistent with the in vivo xenograft studies, human effector cells migrated towards enavatuzumab-treated tumor cells in vitro. Effector cells preferentially migrated toward in vivo responsive tumor cells, and the majority of migratory cells were monocytes and NK cells. Conditioned media from enavatuzumab-treated tumor cells also induced migration, and contained elevated levels of cytokines/chemokines, including IL8 and MCP-1. The presence of an anti-MCP-1 neutralizing antibody in enavatuzumab-treated tumor cell conditioned medium significantly blocked effector cell migration, suggesting that MCP-1 might be responsible for effector cell migration triggered by enavatuzumab. We also observed elevated levels of human MCP-1 in the serum of both enavatuzumab-treated xenograft mouse models and in a subset of patients from the enavatuzumab Phase I clinical study. In summary, in vivo and in vitro studies suggest that enavatuzumab exerts its potent anti-tumor activity, in part, by actively recruiting effector cells and activating effectors to kill tumor cells. In addition, enavatuzumab-induced chemokines may be potential pharmacodynamic biomarkers and warrant further evaluation in clinical studies. 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 2722. doi:1538-7445.AM2012-2722

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.

Abstract 1772: PDL192, a humanized anti-Tweak receptor monoclonal antibody, mediates antitumor effects in primary human breast carcinoma xenografts

Background: PDL192 is a humanized IgG1 monoclonal antibody that binds the human TWEAK receptor (TweakR). TweakR, a member of the TNFR (Tumor Necrosis Factor Receptor) superfamily, is overexpressed in several human cancers including breast cancer (BC). In BC, it may also play a role in the invasive and metastatic potential of the disease (Willis et al, Mol Cancer Res 2008). In TweakR-expressing cancer cell lines or mouse xenograft models, PDL192 has a potent antitumor effect (Culp et al., CCR 2010). All these data therefore suggest that anti-TweakR targeting could be a promising new therapeutic approach for human BC patients. Material and methods: TweakR expression was assessed by IHC (immunohistochemistry) on 3 Tissue-Micro-Array (TMA) banks of BC samples (basal-like, ERBB2, and luminal A/B), and 25 primary human BC xenografts (HBCx). The cut-off of positivity was defined as at least 25% cells with membraneous or cytoplasmic staining or by a combined score of percentage of positive staining cells x intensity > 50. The in vivo antitumor effect of PDL192 was then assessed on 7 TweakR-positive models (10 mg/kg thrice a week for 3 weeks by intraperitoneal route) in which one in combination with chemotherapy as maintenance therapy, as previsouly reported (Marangoni et al., BJC 2009). Results: TMA analyses showed that TweakR was expressed in 16/37 basal like BC (43%), 23/37 ERBB2-positive BC (62%), and 38/71 luminal BC (54%). A high TweakR expression was correlated with double estrogen receptor- and Her2-positive tumors. Moreover, 13/25 xenografts have been found to be TweakR-positive (52%). Nine human BC models have been treated with PDL192, with 4 models (44%) showing a tumor growth inhibition (TGI) ranging between 59% and 91%. No correlation has been observed between TweakR expression and in vivo TGI. Moreover, when PDL192 was administered in complete remission after chemotherapy (doxorubicin + cyclophosphamide), we observed a highly significant delay of relapse greater than 2 months. Conclusions: TweakR is expressed in 77/145 human BC samples (53%). In in vivo experiments, PDL192 showed potent TGI in 4/9 models, and significantly delayed tumor relapses after chemotherapy-induced complete remission. All these data therefore support the use of anti-TWEAK receptor monoclonal antibodies in the treatment of TweakR-positive BC patients. 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 1772. doi:10.1158/1538-7445.AM2011-1772