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Supplementary Fig. S1. Heatmap of mRNA expression for individual melanosomal differentiation antigens and a MITF transcriptional signature using a published dataset of melanoma samples (2). Supplementary Fig. S2. GPNMB expression is induced in multiple BRAF-mutant cells in response to MAPK pathway inhibition. Supplementary Fig. S3. Gene expression of MITF and GPNMB in melanoma cells following MAPK pathway inhibition. Supplementary Fig. S4. Dabrafenib and Trametinib stimulate MITF nuclear localization. Supplementary Fig. S5. Correlation of MITF and GPNMB mRNA expression in melanoma samples from patients that were on-treatment or that progressed on therapy with MAPK pathway 7 inhibitors. RT-qPCR data for MITF and GPNMB was expressed as the ratio relative to pretreatment levels. Supplementary Fig. S6. Correlation between the expression of individual melanosomal genes with MITF mRNA expression in melanoma samples from patients that were on-treatment or that progressed on therapy with MAPK pathway inhibitors. RT-qPCR data for each gene and MITF was normalized to GAPDH and expressed as the ratio relative to pre-treatment levels. Supplementary Fig. S7. MAPK pathway inhibition results in elevated levels of soluble GPNMB released from melanoma cells. Table S1: Clinical characteristics of patients biopsied for evaluation of MITF and GPNMB mRNA expression Table S2: Correlation coefficients between individual gene expression and MITF or a MITF Signature Table S3: Complete Responses Following Trametinib Treatment in Cohorts Injected with A375 or WM-2664 Melanoma Cells. Table S4: List of Primers for RT-qPCR Analyses

Contains supplementary methods, references and figure legends.

Purpose: To determine if BRAF and/or MEK inhibitor–induced GPNMB expression renders melanomas sensitive to CDX-011, an antibody-drug conjugate targeting GPNMB.Experimental Design: The Cancer Genome Atlas melanoma dataset was interrogated for a panel of MITF-regulated melanosomal differentiation antigens, including GPNMB. BRAF-mutant melanoma cell lines treated with BRAF or MEK inhibitors were assessed for GPNMB expression by RT-qPCR, immunoblot, and FACS analyses. Transient siRNA-mediated knockdown approaches were used to determine if MITF is requirement for treatment-induced GPNMB upregulation. GPNMB expression was analyzed in serial biopsies and serum samples from patients with melanoma taken before, during, and after disease progression on MAPK inhibitor treatment. Subcutaneous injections were performed to test the efficacy of MAPK inhibitors alone, CDX-011 alone, or their combination in suppressing melanoma growth.Results: A MITF-dependent melanosomal differentiation signature is associated with poor prognosis in patients with this disease. MITF is increased following BRAF and MEK inhibitor treatment and induces the expression of melanosomal differentiation genes, including GPNMB. GPNMB is expressed at the cell surface in MAPK inhibitor–treated melanoma cells and is also elevated in on-treatment versus pretreatment biopsies from melanoma patients receiving MAPK pathway inhibitors. Combining BRAF and/or MEK inhibitors with CDX-011, an antibody-drug conjugate targeting GPNMB, is effective in causing melanoma regression in preclinical animal models and delays the recurrent melanoma growth observed with MEK or BRAF/MEK inhibitor treatment alone.Conclusions: The combination of MAPK pathway inhibitors with an antibody-drug conjugate targeting GPNMB is an effective therapeutic option for patients with melanoma. Clin Cancer Res; 22(24); 6088–98. ©2016 AACR.

Purpose:ErbB3 and its ligand neuregulin-1 (NRG1) are widely expressed in head and neck squamous cell carcinoma (HNSCC) and associated with tumor progression. A “window-of-opportunity” study (NCT02473731) was conducted to evaluate the pharmacodynamic effects of CDX-3379, an anti-ErbB3 mAb, in patients with HNSCC.Patients and Methods:Twelve patients with newly diagnosed, operable HNSCC received two infusions of CDX-3379 (1,000 mg) at a 2-week interval prior to tumor resection. The primary study objective was to achieve ≥50% reduction in tumor ErbB3 signaling (phosphorylation of ErbB3; pErbB3) in ≥30% of patients. Other potential tumor biomarkers, pharmacokinetics, safety, and tumor measurements were also assessed.Results:pErbB3 was detectable in all tumors prior to treatment and decreased for 10 of 12 (83%) patients following CDX-3379 dosing, with ≥50% reduction in 7 of 12 (58%; P = 0.04; 95% confidence interval, 27.7%–84.8%). Target trough CDX-3379 serum levels were achieved in all patients. CDX-3379 treatment–related toxicity was grade 1–2 and included diarrhea, fatigue, and acneiform dermatitis. Five of 12 (42%) patients had shrinkage in tumor burden, including a marked clinical response in a patient with human papillomavirus–negative oral cavity HNSCC. All patients with tumor shrinkage had tumors that expressed both NRG1 and ErbB3 and demonstrated reduced pErbB3 with CDX-3379 treatment.Conclusions:This study demonstrates that CDX-3379 can inhibit tumor ErbB3 phosphorylation in HNSCC. CDX-3379 was well tolerated and associated with measurable tumor regression. A phase II study (NCT03254927) has been initiated to evaluate CDX-3379 in combination with cetuximab for patients with advanced HNSCC.

Purpose: To determine if BRAF and/or MEK inhibitor–induced GPNMB expression renders melanomas sensitive to CDX-011, an antibody-drug conjugate targeting GPNMB. Experimental Design: The Cancer Genome Atlas melanoma dataset was interrogated for a panel of MITF-regulated melanosomal differentiation antigens, including GPNMB. BRAF-mutant melanoma cell lines treated with BRAF or MEK inhibitors were assessed for GPNMB expression by RT-qPCR, immunoblot, and FACS analyses. Transient siRNA-mediated knockdown approaches were used to determine if MITF is requirement for treatment-induced GPNMB upregulation. GPNMB expression was analyzed in serial biopsies and serum samples from patients with melanoma taken before, during, and after disease progression on MAPK inhibitor treatment. Subcutaneous injections were performed to test the efficacy of MAPK inhibitors alone, CDX-011 alone, or their combination in suppressing melanoma growth. Results: A MITF-dependent melanosomal differentiation signature is associated with poor prognosis in patients with this disease. MITF is increased following BRAF and MEK inhibitor treatment and induces the expression of melanosomal differentiation genes, including GPNMB. GPNMB is expressed at the cell surface in MAPK inhibitor–treated melanoma cells and is also elevated in on-treatment versus pretreatment biopsies from melanoma patients receiving MAPK pathway inhibitors. Combining BRAF and/or MEK inhibitors with CDX-011, an antibody-drug conjugate targeting GPNMB, is effective in causing melanoma regression in preclinical animal models and delays the recurrent melanoma growth observed with MEK or BRAF/MEK inhibitor treatment alone. Conclusions: The combination of MAPK pathway inhibitors with an antibody-drug conjugate targeting GPNMB is an effective therapeutic option for patients with melanoma. Clin Cancer Res; 22(24); 6088–98. ©2016 AACR.

CDX-1140 is an agonist CD40 mAb intended to promote priming of CD8+ effector T cells through activation of dendritic cells (DC), enhance macrophage tumoricidal activity, and mediate direct killing of CD40-expressing tumor cells. CDX-1140 is a human IgG2 mAb with Fc receptor independent activity and is synergistic with sCD40L, suggesting a potential to enhance CD40L-mediated immune activation. CDX-1140 has a broad dose-dependent activity that may achieve maximal agonist activity at doses that provide significant tumor penetration with minimal toxicities from systemic CD40 activation. CDX-301 (rhFLT3L) is a DC growth factor that markedly increases CD141+ DCs, including in the tumor microenvironment (TME). CD141+ DCs are critical for initiating anti-tumor immune responses and are often depleted within the TME. Preclinical studies have shown that treatment with CDX-301 synergizes with CD40 signaling to enhance anti-tumor immune responses, suggesting that combining CDX-1140 and CDX-301 could result in enhanced clinical benefit. CDX1140-01(NCT03329950) is a Phase I dose-escalation study of CDX-1140 as monotherapy or in combination with CDX-301 evaluating safety, PK, PD, and preliminary clinical activity in patients (pts) with refractory solid tumors and non-Hodgkin lymphoma. CDX-1140 is given iv q 4 weeks at doses from 0.01 to 3 mg/kg utilizing a 3+3 design (first 2 cohorts are single-pts). In combination cohorts (solid tumors only), CDX-301 at 75 μg/kg daily x 5 is administered sc prior to cycles 1 and 2 of escalating doses of CDX-1140 starting at 0.09 mg/kg. Tumor-specific expansion cohorts are planned to further explore the activity of monotherapy or combination treatment. To date, 18 pts across 10 tumor types have been dosed in CDX-1140 monotherapy cohorts with doses ranging from 0.01 to 0.72 mg/kg and without identification of an MTD. There has been one DLT (0.18 mg/kg): grade 3 pneumonitis and hypoxia. One pt (0.72 mg/kg) experienced grade 3 fatigue requiring hospitalization 48 hrs after the first infusion. There have been 3 additional grade 3 treatment-related adverse events: dyspnea (0.18 mg/kg), nausea (0.36 mg/kg), and vomiting (0.36 mg/kg). The first combination cohort (n=5) has been completed. In monotherapy and combination cohorts there have been no significant drug-related changes in liver function tests to date. CDX-1140 PK is quantifiable at doses ≥ 0.09 mg/kg and exposure appears dose proportional. Expected dose-dependent PD effects have shown activation of peripheral blood lymphocytes and increases in pro-inflammatory cytokines and chemokines. Combination with CDX-301 has shown enhanced cytokine responses. The data suggest that CDX-1140 has the expected biologic and safety profile predicted from preclinical studies and may achieve dose levels optimal for systemic exposure. The addition of CDX-301 may enhance the activity of CDX-1140. Citation Format: Rachel E. Sanborn, Nashat Y. Gabrail, Nina Bhardwaj, Michael S. Gordon, Mark O'Hara, Danny Khalil, Thomas Hawthorne, Richard Gedrich, Laura Vitale, Mark Rogalski, Tianshu Li, Tracey Rawls, Tibor Keler, Michael Yellin. First-in-human Phase I study of the CD40 agonist mAb CDX-1140 and in combination with CDX-301 (rhFLT3L) in patients with advanced cancers: Interim results [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 LB-194.

Background: ErbB3 (HER3) and its ligand, neuregulin-1 (NRG1), are widely expressed in head and neck squamous cell carcinoma (HNSCC) and associated with tumor progression. Preclinically, treatment of primary tumor and cell line tumor models of HNSCC with CDX-3379, an anti-ErbB3 monoclonal antibody, results in significant tumor reduction and reduced tumor ErbB3 signaling (phosphorylation of ErbB3; pErbB3), and antitumor activity is enhanced when combined with cetuximab. In a Phase 1 clinical study, a patient (pt) with cetuximab- refractory HNSCC experienced a durable complete response to CDX-3379 and cetuximab. A “window-of-opportunity” study was conducted to evaluate the effect of CDX-3379 on pErbB3 and other potential tumor biomarkers in pts with HNSCC. Methods: Pts with newly diagnosed, operable HNSCC received CDX-3379 (1000 mg IV) at a 2-week interval prior to tumor resection. Pre- and post-treatment tumor samples were evaluated for expression of pErbB3 (VeraTag®); ErbB3 and NRG (quantitative in situ hybridization); and Ki67 and phosphatase and tensin homolog (PTEN) (quantitative immuno-fluorescence). Primary study objective was to demonstrate ≥ 50% reduction in pErbB3 in ≥ 30% of pts. Toxicity, pharmacokinetics, and tumor measurements were also assessed. Results: 12 pts with HNSCC (5 oral cavity, 4 oropharynx, 3 larynx; 3 HPV+, 9 HPV-; 10 stage IVA) received 2 CDX-3379 doses. Radiographic assessments and tumor resection were performed at a median (range) of 20.5 (15-26) and 27.5 (18-35) days from first CDX-3379 dose. CDX-3379 reduced pErbB3 levels in 10/12 (83%) pt samples, with ≥ 50% decreases in 7/12 (58%, P=0.04). Ki67 decreased in 5/12 (42%). In this small sample, NRG, ErbB3 or PTEN expression did not clearly correlate with changes in pErbB3, Ki67 or tumor measurements. Target trough CDX-3379 serum levels (50 µg/ml based on mouse xenograft models) were achieved in all pts. Treatment-related toxicity included diarrhea (n=6), fatigue (n=2), and acneiform dermatitis (n=2). 11/12 (92%) pts had RECIST stable disease prior to resection. A pt with HPV- HNSCC experienced significant tumor shrinkage (26% decrease in nodal metastasis radiographically; 92% in primary tumor by physical exam) on day 16, as well as marked improvement in pain and ability to eat. Tumor pErbB3 reduced from 0.45 to Conclusions: CDX-3379 is associated with molecular and clinical activity in HNSCC. CDX-3379 administration was well-tolerated and induced a significant decrease in pErbB3. In this small study of 2 CDX-3379 doses over 14 days, one pt experienced a marked clinical effect including reduced tumor size and symptomatology and 92% had RECIST stable disease pre-resection. A Phase 2 study has been initiated to evaluate the combination of CDX-3379 and cetuximab for pts with progressive HNSCC after prior cetuximab and checkpoint inhibition. Citation Format: Umamaheswar Duvvuri, Jonathan George, Seungwon Kim, Diego Alvarado, Veronique Neumeister, Ahmed Chenna, Thomas Hawthorne, Theresa LaVallee, Jennifer R. Grandis, Julie E. Bauman. Molecular and clinical activity of CDX-3379, an anti-ErbB3 monoclonal antibody, in head and neck squamous cell carcinoma: A preoperative "window of opportunity" study [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 CT058.

Glycoprotein non-metastatic melanoma B (GPNMB) is a transmembrane protein overexpressed in 30 - 40% of triple negative breast cancer (TNBC) and has shown to be associated with metastasis and disease recurrence. An anti-GPNMB antibody drug conjugate, Glembatumumab Vedotin (CDX-011), is currently in Phase II clinical trials for the treatment of metastatic TNBC patients, with promising outcomes. Positron Emission Tomography using radiolabeled antibodies could be advantageous in stratifying patients who may benefit from CDX-011, tracking the biodistribution of CDX-011, and assessing GPNMB expression in vivo. To this end, we radiolabeled the naked antibody, Glembatumumab (CR011), with the positron-emitting 89Zr (half life = 3.3 days). We characterized the stability, affinity, rate of cellular internalization, and specificity of 89Zr-CR011 using various cell-binding assays in human TNBC cell lines. We determined that 89Zr-CR011 is stable in serum solution for up to 5 days, binds specifically to GPNMB+ TNBC cells with high affinity (KD = 16 nM), and internalizes rapidly (50% within 30 - 60 min). We conducted a biodistribution study from 1 - 12 days post administration via tail vein in GPNMB+ MDA-MB-468 xenografts to determine the time point at which we achieve the optimal tumor-to-nontarget ratios. A subset of mice was administered a blocking dose of unlabeled CR011 (100-fold excess, 1 mg/mouse), where we observed a 2.5-fold reduction in 89Zr-CR011 tumor uptake, confirming the specificity of 89Zr-CR011 for GPNMB+ TNBC tumors. PET imaging studies and dosimetry calculations are currently in progress. This preliminary study demonstrates that 89Zr-CR011 may be an excellent companion diagnostic agent for CDX-011 therapy and an essential tool to assess the function of GPNMB in vivo. Citation Format: Bernadette V. Marquez, Supum Lee, Tibor Keler, Thomas Hawthorne, Jeremy Hoog, Shunqiang Li, Cynthia Ma, Suzanne E. Lapi. Targeting GPNMB with 89Zr-CR011 for PET imaging of triple negative breast cancer. [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 4209.

Background: The duration of survival benefit from MAPKi in B-raf mutant melanoma (MEL) is limited by the near universal development of resistance (RES). Recently, MiTF, a transcription factor and master regulator of melanocyte differentiation - was identified as a hub of MAPKi RES. Given its dual role as both a tumor promoter and inducer of MEL senescence, MiTF is a problematic therapeutic target. Pigmentation is a MiTF-dependent feature of MELs correlates with poor survival. We have interrogated the MAPKi/MiTF-dependent regulation of a panel of MITF-regulated melanosomal differentiation antigens (MDAs) for their potential as therapeutic targets to overcome MAPKi RES. Methods: The TCGA MEL gene expression data set was interrogated. B-raf mutant MEL cells were exposed to dabrafenib (D), or trametinib (T). qRT-PCR, Immunoblot or FACS were used to assess MiTF and MDA expression. Serial biopsy tissue and serum samples from MEL patients taken before treatment, during treatment, and at progression with MAPKi therapy were obtained, and analyzed by IHC and qRT-PCR, RNAseq, and ELISA. Transient siRNA-mediated knockdown was used to assess the requirement for MiTF, in MAPKi-mediated induction of MDAs, including GPNMB. To assess the interaction between MAPKi and CDX011 (C), a GPNMB- targeted antibody drug conjugate, mice bearing A375 and WM2664 xenografts were treated with T or DT + C in combination. Results: MiTF is strongly correlated with MDAs, including GPNMB in gene-expression datasets derived from human MEL tumors. A MiTF driven MDA-gene-signature correlates with poor survival among 291 melanoma patients. MAPKi treatment increased MiTF and MDAs in MEL cells, and induced pigmentation in vivo. This phenotype was reversible as MEL acquired RES to MAPKi. Knockdown of MiTF leads to abrogation of MAPKi-mediated GPNMB induction. GPNMB promotes MEL invasion in vitro. MiTF and MDA were elevated in tumors and serum from patients receiving MAPKi treatment and returned to baseline in tumors that acquired RES. The addition of C to either T or DT led to, decreased pigmentation, prolonged tumor regression and inhibited the development RES to T or DT treatment in vivo. Tumors that acquired RES to DT displayed increased c-Met expression and MAPK activation; tumors treated with DT+C failed to develop this phenotype. Conclusions: MAPKi induce MDA in a MiTF-dependent manner in MEL. This process leads to melanocytic differentiation and increased pigmentation, which is subsequently reversed as a tumor acquires RES to MAPKi. This demonstrates the plasticity of MEL in response to MAPKi. The pigmented phenotype is less proliferative but more invasive which is in part mediated by GPNMB. This transient phenotype may allow tumors to acquire characteristics (ie. c-Met upregulation and MAPK re-activation) which contribute to MAPKi RES. Targeting a pro-invasive MDA, GPNMB with CDX-011 subverts this plasticity and impairs the development of MAPKi RES. Citation Format: April A.N. Rose, Matthew G. Annis, Dennie T. Frederick, Zhifeng Dong, Lawrence Kwong, Tibor Keller, Thomas Hawthorne, Ian R. Watson, Keith T. Flaherty, Peter M. Siegel. Targeting the melanosome: overcoming MAPK-inhibitor resistance in melanoma. [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 296.

Introduction: Glembatumumab vedotin is an antibody-auristatin conjugate that targets cells expressing the transmembrane glycoprotein NMB (GPNMB, also known as osteoactivin, dc-HIL, and HGFIN). Because of the restrictive expression of GPNMB, testing was limited to the PPTP osteosarcoma (OS) xenograft panel as well as two non-GPNMB expressing rhabdomyosarcoma (RMS) xenografts. Methods: Glembatumumab vedotin was administered intravenously in 0.9% saline at a dose of 2.5 mg/kg using a weekly x 3 schedule. GPNMB was assessed at the RNA level (Agilent SurePrint3) and by IHC. Results: All of the six OS xenografts against which glembatumumab vedotin was tested expressed GPNMB at the RNA level as evaluated using Agilent gene expression arrays. By contrast, none of the RMS xenografts expressed GPNMB at the RNA level. Most OS xenografts showed GPNMB expression detectable by IHC (6/7), while none of the RMS xenografts showed tumor staining for GPNMB (0/6). Glembatumumab vedotin was well tolerated, and all 8 tested xenograft models were considered evaluable for efficacy. For the OS xenografts, glembatumumab vedotin induced significant differences in EFS distribution compared to control in each of the 6 models studied. Three of 6 OS xenografts showed maintained complete responses (MCR) to glembatumumab vedotin. Two other xenografts showed progressive disease with growth delay (PD2), with one of these showing near stable disease during the 6 weeks of treatment and observation. The final OS xenograft showed progressive disease with no growth delay (PD1). As expected, the two RMS xenografts showed limited responses to glembatumumab vedotin (PD1 and PD2), although one did show significant tumor growth inhibition with an EFS T/C value of 2.6. Two of the OS xenografts with MCR showed the highest GPNMB expression at the RNA level. Conversely, the xenograft with the lowest GPNMB gene expression had the poorest response to glembatumumab vedotin. For GPNMB protein expression assessed by IHC, 2 of the xenografts with MCR showed the highest expression level and highest percent tumor expression, but the other responding line showed GPNMB expression on only 5% of tumor cells, despite exhibiting one of the highest expression levels of GPNMB by mRNA. The two OS xenograft lines least responsive to glembatumumab vedotin were also the least responsive OS xenografts to vincristine and eribulin. Conclusions: Glembatumumab vedotin showed high-level activity against 3 of 6 OS xenografts. Response of OS xenografts to glembatumumab vedotin may be related to both GPNMB expression and to the intrinsic susceptibility of xenografts to tubulin inhibitors. RMS xenografts showed PD1 or PD2 responses to glembatumumab vedotin despite having known sensitivity to tubulin-binding agents such as eribulin. Glembatumumab vedotin is the first antibody-drug conjugate with documented in vivo activity against OS. (Supported by NO1-CM-42216) Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C207. Citation Format: Richard Gorlick, Anders Kolb, Jainrong Wu, Raushan Kurmasheva, Thomas Hawthorne, Peter Houghton, Malcolm Smith. Pediatric Preclinical Testing Program (PPTP) stage 1 evaluation of Glembatumumab Vedotin. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C207.