Patrick Mayes

The BRAF and MEK Inhibitors Dabrafenib and Trametinib: Effects on Immune Function and in Combination with Immunomodulatory Antibodies Targeting PD-1, PD-L1, and CTLA-4

Purpose: To assess the immunologic effects of dabrafenib and trametinib in vitro and to test whether trametinib potentiates or antagonizes the activity of immunomodulatory antibodies in vivo. Experimental Design: Immune effects of dabrafenib and trametinib were evaluated in human CD4+ and CD8+ T cells from healthy volunteers, a panel of human tumor cell lines, and in vivo using a CT26 mouse model. Results: Dabrafenib enhanced pERK expression levels and did not suppress human CD4+ or CD8+ T-cell function. Trametinib reduced pERK levels, and resulted in partial/transient inhibition of T-cell proliferation/expression of a cytokine and immunomodulatory gene subset, which is context dependent. Trametinib effects were partially offset by adding dabrafenib. Dabrafenib and trametinib in BRAF V600E/K, and trametinib in BRAF wild-type tumor cells induced apoptosis markers, upregulated HLA molecule expression, and downregulated certain immunosuppressive factors such as PD-L1, IL1, IL8, NT5E, and VEGFA. PD-L1 expression in tumor cells was upregulated after acquiring resistance to BRAF inhibition in vitro. Combinations of trametinib with immunomodulators targeting PD-1, PD-L1, or CTLA-4 in a CT26 model were more efficacious than any single agent. The combination of trametinib with anti–PD-1 increased tumor-infiltrating CD8+ T cells in CT26 tumors. Concurrent or phased sequential treatment, defined as trametinib lead-in followed by trametinib plus anti–PD-1 antibody, demonstrated superior efficacy compared with anti–PD-1 antibody followed by anti–PD-1 plus trametinib. Conclusion: These findings support the potential for synergy between targeted therapies dabrafenib and trametinib and immunomodulatory antibodies. Clinical exploration of such combination regimens is under way. Clin Cancer Res; 21(7); 1639–51. ©2015 AACR.

Novel anti-B-cell maturation antigen antibody-drug conjugate (GSK2857916) selectively induces killing of multiple myeloma

B-cell maturation antigen (BCMA), highly expressed on malignant plasma cells in human multiple myeloma (MM), has not been effectively targeted with therapeutic monoclonal antibodies. We here show that BCMA is universally expressed on the MM cell surface and determine specific anti-MM activity of J6M0-mcMMAF (GSK2857916), a novel humanized and afucosylated antagonistic anti-BCMA antibody-drug conjugate via a noncleavable linker. J6M0-mcMMAF specifically blocks cell growth via G2/M arrest and induces caspase 3-dependent apoptosis in MM cells, alone and in coculture with bone marrow stromal cells or various effector cells. It strongly inhibits colony formation by MM cells while sparing surrounding BCMA-negative normal cells. J6M0-mcMMAF significantly induces effector cell-mediated lysis against allogeneic or autologous patient MM cells, with increased potency and efficacy compared with the wild-type J6M0 without Fc enhancement. The antibody-dependent cell-mediated cytotoxicity and apoptotic activity of J6M0-mcMMAF is further enhanced by lenalidomide. Importantly, J6M0-mcMMAF rapidly eliminates myeloma cells in subcutaneous and disseminated mouse models, and mice remain tumor-free up to 3.5 months. Furthermore, J6M0-mcMMAF recruits macrophages and mediates antibody-dependent cellular phagocytosis of MM cells. Together, these results demonstrate that GSK2857916 has potent and selective anti-MM activities via multiple cytotoxic mechanisms, providing a promising next-generation immunotherapeutic in this cancer.

Evaluation of B cell maturation antigen as a target for antibody drug conjugate mediated cytotoxicity in multiple myeloma.

B‐cell maturation antigen (BCMA, also termed TNFRSF17) is an attractive therapeutic target due to its restricted expression on normal and malignant plasma cells (PC). GSK2857916 (or J6M0‐MMAF) is a BCMA‐specific antibody conjugated to the microtubule‐disrupting agent monomethyl auristatin F (MMAF) via a protease‐resistant linker. To evaluate the clinical potential of this agent, tumour cells from seventy multiple myeloma (MM) patients were assessed for BCMA expression by immunohistochemistry and flow cytometry. All patients tested expressed BCMA, at varying levels, and both surface and intracellular expression were observed. BCMA expression is maintained through relapse, extramedullary spread and in residual disease post therapy. BCMA levels may also be prognostically useful as higher levels of BCMA were associated with poorer outcomes, even taking into account genetic risk. We observed rapid internalization of surface BCMA and newly expressed protein by 1 h, suggesting a mechanism for J6M0‐MMAF activity even with low surface antigen. J6M0‐MMAF mediated cytotoxicity of MM cells varied with dose and antigen levels, with clonogenic progenitors killed at lower doses than mature cells. In comparison, J6M0‐MMAF killing of primary CD138+ myeloma cells occurred with slower kinetics. Our observations support BCMA to be a promising therapeutic target in MM for novel therapies such as J6M0‐MMAF.

Abstract CT039: INDUCE-1: a phase I open-label study of GSK3359609, an ICOS agonist antibody, administered alone and in combination with pembrolizumab in patients with selected, advanced solid tumors

Background Inducible T cell Co-Stimulator (ICOS), a member of the CD28/B7/CTLA immunoglobulin receptor superfamily, is expressed on T cells after engagement with cognate antigen and activation. ICOS provides a co-stimulatory signal augmenting T cell proliferation, cytokine production, cytotoxic function and survival. GSK3359609 is a humanized IgG4 antibody selected for its potent binding agonist activity against human ICOS. Rationale for targeting ICOS with GSK33359609 as a monotherapy and in combination with other cancer immunotherapies such as pembrolizumab is supported by preclinical evidence. Methods INDUCE-1 is a first in human study evaluating safety, tolerability, pharmacokinetics, pharmacodynamics, immunogenicity, and preliminary antitumor activity of GSK3359609 administered as an intravenous (IV) infusion once every three weeks (Q3W) alone (Part 1) and in combination with 200 mg pembrolizumab (Q3W IV infusion) or other immunotherapy (Part 2) in approximately 304 adult patients. In the dose escalation phase, eligible patients are required to have selected, relapsed/refractory solid tumors. Accelerated titration design is planned for the first 3 dose levels in Part 1, with 1 patient enrolled at each dose level; modified toxicity probability interval method will inform on subsequent dose escalation decisions (minimum 3 patients per dose level), and maximum tolerated dose or maximum administered dose determination. In the expansion phase, cohorts may be defined by factors such as tumor histology, biomarker features, or prior treatment. More than one GSK3359609 dose level may be evaluated in a single expansion cohort by patient random assignment. Tumor biopsies (before and on-treatment) are optional in escalation and required in expansion to provide biomarker data that may inform on optimal dose selection as well as mechanistic understanding of GSK3359609 activity. Immune-related Response Evaluation Criteria in Solid Tumors will be the primary measure of clinical activity. As of 12 January 2017, no dose limiting toxicities (DLT) were observed in the first 2 dose levels of GSK3359609 monotherapy; dose level 3 cohort enrollment is completed and under observation for DLTs. ClinicalTrials.gov identifier: NCT02723955 Study is funded by GlaxoSmithKline and is in collaboration with Merck & Co, Inc Citation Format: Eric Angevin, Todd M. Bauer, Catherine E. Ellis, Hui Gan, Rigel Hall, Aaron Hansen, Axel Hoos, Roxanne C. Jewell, Jessica Katz, Juan Martin-Liberal, Michele Maio, Patrick A. Mayes, Jolly Mazumdar, Michael Millward, Danny Rischin, Jan H. Schellens, Sapna Yadavilli, Helen Zhou. INDUCE-1: a phase I open-label study of GSK3359609, an ICOS agonist antibody, administered alone and in combination with pembrolizumab in patients with selected, advanced solid tumors [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 CT039. doi:10.1158/1538-7445.AM2017-CT039

Abstract IA22: Targeting inducible T cell co-stimulator (ICOS) promotes effector T cell function and antitumor response

Cancer immunity is regulated by co-stimulatory mechanisms that when triggered may mount effective anticancer responses. Robust antitumor responses, including complete cures, have been achieved by modulating patients9 immune systems. Antibodies targeting the immune checkpoint receptors cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1 (PD-1)/PD ligand-1 (PD-L1) have demonstrated impressive activity in select patients; however, most cancers remain non-responsive to this class of agents. Inducible T cell co-stimulator (ICOS) is a T cell restricted co-stimulatory receptor belonging to the CD28/CTLA immunoglobulin super family whose expression is highly induced on CD4+ and CD8+ T cells upon T cell receptor (TCR) activation. Here we describe the development of a humanized monoclonal antibody (H2L5 IgG4PE) with specific, high-affinity binding to human ICOS capable of delivering agonistic activity and stimulating effector CD4+ and cytotoxic CD8+ T cell activation, expansion, and function. We show that the antibody isotype and FcγR-mediated crosslinking are critical features required for optimal activity of the H2L5 antibody. In mouse tumor models antibody-induced ICOS agonism elicited potent T cell activation and antitumor responses alone and synergistically in combination with other agents, including an anti-PD1 antibody. The first-in-class ICOS agonist antibody described here offers a promising next-generation immunotherapy agent to enhance the magnitude and duration of antitumor responses in patients whose tumors are already sensitive to current immunotherapy approaches as well as potentially expanding the population of patients and range of tumor types that respond to immunotherapy. A phase I clinical trial has been initiated to test H2L5 IgG4PE (GSK3359609) alone and in combination with anti-PD1 and other anticancer agents in patients with solid tumors (www.clinicaltrials.gov;NCT02723955). Citation Format: Patrick A. Mayes, Sapna Yadavilli, Yao-Bin Liu, Meixia Bi, Tianqian Zhang, Kelhia Sendeyo, Jane Willoughby, Laura Seestaller-Wehr, Ashleigh Hahn, Sabyasachi Bhattacharya, M. Phillip DeYoung, Christina Blackwell, Hong Shi, David Killian, Michael Adam, Shu-Yun Zhang, Junping Jing, Chris Hopson, Gilles Marodon, Mark S. Cragg, Axel Hoos. Targeting inducible T cell co-stimulator (ICOS) promotes effector T cell function and antitumor response [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 IA22.

Abstract 525: Higher mutation rate is associated with more frequent expression of cancer/testis antigens in human tumors

Tumors with high mutation rate such as those of melanoma and non-small cell lung cancers (NSCLC) have shown greatest response to the emerging immune therapies. These tumors harbor a large number of somatic mutations, some of which could be translated into neoantigens, potentially evoking host immune response. To what degree self antigens, many of which are cancer testis (CT) antigens, contribute to enhanced immune response in these tumors has never been systematically studied. Here we show that cancers with higher mutation rate frequently express a larger number of CT antigens than cancers with fewer mutations. In NSCLC, tumors with more than 300 non-synonymous mutations (75th percentile, n = 158) express more than 3 times as many CT antigens as those tumors with fewer than 100 mutations (25th percentile, n = 162), with a P-value of 1.6e-13. In head and neck cancers, tumors with more than 140 non-synonymous mutations (75th percentile, n = 79) express nearly twice as many CT antigens as those tumors with fewer than 60 mutations (25th percentile, n = 80), with a P-value of 0.004. Additionally, in NSCLC, tumors with high mutation rate are associated with higher expression of CD8B and granzyme B, markers representing cytotoxic lymphocytes. Tumors with more expressed CT antigens are also associated with higher expression of these markers. These data suggest that CT antigens, along with neoantigens, may contribute to a stronger host immune response in these hypermutative tumors. Citation Format: Junping Jing, Patrick Mayes, Yan Degenhardt, James R. Brown, Philippe Sanseau. Higher mutation rate is associated with more frequent expression of cancer/testis antigens in human tumors. [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 525.

Abstract 5031: Effects of BRAF and MEK inhibitors, dabrafenib and trametinib, on the immune system and in combination with immunomodulatory antibodies targeting PD1, PD-L1 and CTLA-4

The immunological effects of dabrafenib and trametinib and whether they potentiate or antagonize the activity of immunomodulatory antibodies are not well understood. We assessed the immunological effects of dabrafenib and trametinib at clinically relevant exposure concentrations on both immune and tumor cells in vitro and in vivo, and tested their anti-tumor efficacy in combination with immunomodulatory antibodies in immune-competent syngeneic mouse models. Human CD4+ and CD8+ T cells isolated from healthy volunteers were treated with trametinib and dabrafenib either alone or in combination, and with or without anti-CD3/anti-CD28 bead activation (concurrently or sequentially). Dabrafenib alone enhanced pERK expression levels with no changes of pAKT and pS6 proteins, and had no suppressive impact on human CD4+ or CD8+ T cell proliferation, apoptosis and cytokine production in response to T cell activation. Trametinib alone reduced the pERK levels with no changes in pAKT and apoptosis. However trametinib resulted in partial inhibitory effects on T cell proliferation, pS6 proteins and cytokine expression. These inhibitory effects were transient and only observed if cells were treated with trametinib prior to or simultaneously with T cell activation, while trametinib had little or no suppressive effects on activated T cells. Adding dabrafenib partially offset the transient inhibitory effects caused by trametinib alone. Similarly, gene expression profiling showed that trametinib partially decreased the expression levels of a subset of cytokines and chemokines (e.g. IL1, IL2, IL8, IL10, TNFa, CCL2) and activation/regulation markers (e.g. CD69, CD25, PD1, CTLA4) when trametinib was added prior to or simultaneously with T cell activators. Multi-color flow cytometry confirmed cell surface changes in the expression of CD69, CD25, PD1, OX40 and CTLA4. However, the expression levels of CD69 and OX40 were still well above non-activated T cells. On tumor cells, dabrafenib and trametinib up-regulated HLA molecules and melanoma antigen MART1 expression, and down regulated immune-suppressive factors such as PD-L1, VEGF and IL8 etc in BRAFV600E melanoma cells. Combinations of trametinib with immunomodulators targeting PD1, PD-L1 or CTLA4 in murine syngeneic tumor models are underway and will be presented at the meeting. These findings to date support clinical exploration of dabrafenib and/or trametinib in combination with specific immunomodulatory antibodies. Citation Format: Li Liu, Patrick Mayes, Stephen Eastman, Hong Shi, Sapna Yadavilli, Xiaoyu Pan, Jingsong Yang, Laura Seestaller-Wehr, Shu-Yun Zhang, Chris Hopson, Lyuben Tsvetkov, Junping Jing, James Smothers, Drew M. Pardoll, Axel Hoos. Effects of BRAF and MEK inhibitors, dabrafenib and trametinib, on the immune system and in combination with immunomodulatory antibodies targeting PD1, PD-L1 and CTLA-4. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5031. doi:10.1158/1538-7445.AM2014-5031

Abstract 644: Novel anti-B cell maturation antigen-monomethyl auristatin F antibody-drug conjugate (GSK2857916) induces potent and selective anti-multiple myeloma activity via enhanced effector function and direct tumor cell killing

B cell maturation antigen (BCMA), highly expressed on malignant plasma cells in human multiple myeloma (MM), has not been effectively targeted with therapeutic monoclonal antibodies (mAbs). We here investigated the anti-MM activity of J6M0-mcMMAF (GSK2857916), a humanized and afucosylated anti-BCMA antibody-drug conjugate (ADC) via uncleavable linker. This novel antagonist anti-BCMA antibody shows binding against all CD138-expressing MM cell lines and patient MM cells, confirming universal BCMA expression on the surface of myeloma cells. Real-time qRT-PCR also showed significantly upregulated BCMA mRNA in CD138+ cells purified from MM patients vs. normal donors (p Note: This abstract was not presented at the meeting. Citation Format: Yu-Tzu Tai, Chirag Acharya, Mike Y. Zhong, Michele Cea, Antonia Cagnetta, Patrick A. Mayes, Jenny Craigen, Louise Gliddon, James Smothers, Amanda L. Christie, Andrew L. Kung, Paul Richardson, Nikhil C. Munshi, Kenneth C. Anderson. Novel anti-B cell maturation antigen-monomethyl auristatin F antibody-drug conjugate (GSK2857916) induces potent and selective anti-multiple myeloma activity via enhanced effector function and direct tumor cell killing. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 644. doi:10.1158/1538-7445.AM2014-644