Raymond Rothstein

Targeting CD73 in the tumor microenvironment with MEDI9447

ABSTRACT MEDI9447 is a human monoclonal antibody that is specific for the ectoenzyme CD73 and currently undergoing Phase I clinical trials. Here we show that MEDI9447 is a potent inhibitor of CD73 ectonucleotidase activity, with wide ranging immune regulatory consequences. MEDI9447 results in relief from adenosine monophosphate (AMP)-mediated lymphocyte suppression in vitro and inhibition of mouse syngeneic tumor growth in vivo. In contrast with other cancer immunotherapy agents such as checkpoint inhibitors or T-cell agonists, MEDI9447 drives changes in both myeloid and lymphoid infiltrating leukocyte populations within the tumor microenvironment of mouse models. Changes include significant alterations in a number of tumor micro-environmental subpopulations including increases in CD8+ effector cells and activated macrophages. Furthermore, these changes correlate directly with responder and non-responder subpopulations within animal studies using syngeneic tumors. Combination data showing additive activity between MEDI9447 and anti-PD-1 antibodies using human cells in vitro and mouse tumor models further demonstrate the potential value of relieving adenosine-mediated immunosuppression. Based on these data, a Phase I study to test the safety, tolerability, and clinical activity of MEDI9447 in cancer patients was initiated (NCT02503774).

Doxil Synergizes with Cancer Immunotherapies to Enhance Antitumor Responses in Syngeneic Mouse Models

Based on the previously described roles of doxorubicin in immunogenic cell death, both doxorubicin and liposomal doxorubicin (Doxil) were evaluated for their ability to boost the antitumor response of different cancer immunotherapies including checkpoint blockers (anti–PD-L1, PD-1, and CTLA-4 mAbs) and TNF receptor agonists (OX40 and GITR ligand fusion proteins) in syngeneic mouse models. In a preventative CT26 mouse tumor model, both doxorubicin and Doxil synergized with anti–PD-1 and CTLA-4 mAbs. Doxil was active when CT26 tumors were grown in immunocompetent mice but not immunocompromised mice, demonstrating that Doxil activity is increased in the presence of a functional immune system. Using established tumors and maximally efficacious doses of Doxil and cancer immunotherapies in either CT26 or MCA205 tumor models, combination groups produced strong synergistic antitumor effects, a larger percentage of complete responders, and increased survival. In vivo pharmacodynamic studies showed that Doxil treatment decreased the percentage of tumor-infiltrating regulatory T cells and, in combination with anti–PD-L1, increased the percentage of tumor-infiltrating CD8+ T cells. In the tumor, Doxil administration increased CD80 expression on mature dendritic cells. CD80 expression was also increased on both monocytic and granulocytic myeloid cells, suggesting that Doxil may induce these tumor-infiltrating cells to elicit a costimulatory phenotype capable of activating an antitumor T-cell response. These results uncover a novel role for Doxil in immunomodulation and support the use of Doxil in combination with checkpoint blockade or TNFR agonists to increase response rates and antitumor activity.

Abstract 285: MEDI9447: enhancing anti-tumor immunity by targeting CD73 In the tumor microenvironment

MEDI9447 is a monoclonal antibody specific for the ectoenzyme, CD73. Data is presented in support of the hypothesis that targeting the extracellular production of adenosine by CD73 reduces the immunosuppressive effects of adenosine. We report a range of activities for this antibody, including inhibition of both recombinant and cellular CD73 ectonucleotidase activity, relief from AMP-mediated lymphocyte suppression in vitro, and inhibition of syngeneic tumor growth. In contrast with many other cancer immunotherapy agents such as checkpoint inhibitors or T cell agonists, MEDI9447 drives changes in both myeloid and lymphoid infiltrating leukocyte populations within the tumor microenvironment. Changes include significant increases in CD8 effector cells and activated macrophages, as well as a reduction in the proportions of myeloid-derived suppressor cells (MDSC) and regulatory T lymphocytes. Furthermore, these changes correlate directly with responder and non-responder subpopulations within the arms of animal studies using syngeneic tumors. Data showing additive activity between MEDI9447 and other immune-mediated therapy antibodies demonstrates the importance of relieving adenosine-mediated immunosuppression within tumors. Citation Format: Carl Hay, Erin Sult, Qihui Huang, Scott Hammond, Kathy Mulgrew, Kelly McGlinchey, Stacy Fuhrmann, Raymond Rothstein, Edmund Poon, Ross Stewart, Robert Hollingsworth, Kris Sachsenmeier. MEDI9447: enhancing anti-tumor immunity by targeting CD73 In the tumor microenvironment. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 285. doi:10.1158/1538-7445.AM2015-285

Antibody-drug conjugates bearing pyrrolobenzodiazepine or tubulysin payloads are immunomodulatory and synergize with multiple immunotherapies

Immunogenic cell death (ICD) is the process by which certain cytotoxic drugs induce apoptosis of tumor cells in a manner that stimulates the immune system. In this study, we investigated whether antibody-drug conjugates (ADCS) conjugated with pyrrolobenzodiazepine dimer (PBD) or tubulysin payloads induce ICD, modulate the immune microenvironment, and could combine with immuno-oncology drugs to enhance antitumor activity. We show that these payloads on their own induced an immune response that prevented the growth of tumors following subsequent tumor cell challenge. ADCs had greater antitumor activity in immunocompetent versus immunodeficient mice, demonstrating a contribution of the immune system to the antitumor activity of these ADCs. ADCs also induced immunologic memory. In the CT26 model, depletion of CD8+ T cells abrogated the activity of ADCs when used alone or in combination with a PD-L1 antibody, confirming a role for T cells in antitumor activity. Combinations of ADCs with immuno-oncology drugs, including PD-1 or PD-L1 antibodies, OX40 ligand, or GITR ligand fusion proteins, produced synergistic antitumor responses. Importantly, synergy was observed in some cases with suboptimal doses of ADCs, potentially providing an approach to achieve potent antitumor responses while minimizing ADC-induced toxicity. Immunophenotyping studies in different tumor models revealed broad immunomodulation of lymphoid and myeloid cells by ADC and ADC/immuno-oncology combinations. These results suggest that it may be possible to develop novel combinatorial therapies with PBD- and tubulysin-based ADC and immuno-oncology drugs that may increase clinical responses. Cancer Res; 77(10); 2686-98. ©2017 AACR.

Abstract 30: Medi3622, a monoclonal antibody to ADAM17, inhibits tumor growth by inhibiting EGFR- and non-EGFR-mediated pathways

ADAM17 is the primary sheddase for HER pathway ligands. We report the discovery of a potent and specific ADAM17 inhibitory antibody, MEDI3622, which induces tumor regression or stasis in many EGFR-dependent tumor models. The inhibitory activity of MEDI3622 correlated with EGFR activity both in a series of tumor models across several indications as well as in a focused set of head and neck patient derived xenograft models. Cynomolgus monkey and rat PK/PD assays showed MEDI3622 inhibited TNFα shedding. Toxicity observed in cynomolgus monkey and rat was similar to EGFR inhibitor-induced rash. However, the antitumor activity of MEDI3622 was superior to that of EGFR/HER pathway inhibitors in OE21 head and neck and COLO205 colorectal xenograft models suggesting additional activity outside of the EGFR pathway. Combination of MEDI3622 and cetuximab in the OE21 model was additive and eradicated tumors. Proteomics analysis revealed novel ADAM17 substrates which function outside of the HER pathways and may contribute towards the antitumor activity of the monoclonal antibody. Citation Format: Darrin Sabol, Jonathan RiosDoria, Jon Chesebrough, David Stewart, Kevin Schifferli, Raymond Rothstein, Ching Ching Leow, Jenny Heidbrink-Thompson, Li Cheng, Qun Du, Linda Xu, Xiaofang Jin, Ravinder Tammali, Chanshou Gao, Jay Friedman, Brandy Wilkinson, Melissa Damschroder, Andrew Pierce, MunMun Patnaik, Rong Zeng, Yuling Wu, Susan Spitz, Gabriel Robbie, Lorin Roskos, Robert Hollingsworth, David Tice, Emil Michelotti. Medi3622, a monoclonal antibody to ADAM17, inhibits tumor growth by inhibiting EGFR- and non-EGFR-mediated pathways. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 30. doi:10.1158/1538-7445.AM2015-30

Abstract A112: Combined targeting of HER2 and HER3 inhibits tumor growth in both trastuzumab-sensitive and trastuzumab-resistant breast cancer models.

HER3 (ERBB3) is a tumor driver in divergent cancer types with high HRG levels or heightened EGFR or HER2 kinase activity via growth signal coupling to the PI3K-AKT pathway. HER3 lacks intrinsic tyrosine kinase activity but is capable of signaling after heterodimerizing with tyrosine kinase ERBB family members EGFR or HER2. Heterodimer formation is driven either by the binding of heregulin (NRG1/HRG) to HER3 (ligand dependent - LD), or alternatively, by overexpression of EGFR or HER2 (ligand-independent - LI). Preclinical evaluation of MEDI3379, a human IgG1 modified monoclonal anti-HER3 antibody that antagonizes both LD and LI signaling, demonstrated tumor growth inhibition in the HER2-expressing MDA-MB-361 breast cancer xenograft model. Anti-tumor activity of MEDI3379 in this model was increased in combination with the HER2-targeting drug trastuzumab to a greater extent than MEDI3379 when combined with either lapatinib or pertuzumab. Combined inhibition of HER2 and HER3 led to strong reduction in pHER3. Unexpectedly, co-administration of MEDI3379 together with trastuzumab in MDA-MB-361 tumor-bearing mice but not in naive mice resulted in reduced serum levels of trastuzumab. A control antibody combined with trastuzumab in MDA-MB-361 tumor bearing mice did not have this effect. Furthermore, in the trastuzumab-resistant JIMT-1 breast cancer xenograft model which has high HRG and pHER3 levels MEDI3379 but not pertuzumab resensitized JIMT-1 tumors to trastuzumab resulting in synergistic anti-tumor activity and a reduction of pHER3. In vivo resistance to this regimen appeared with prolonged treatment of JIMT-1 tumors and was accompanied by a decrease in homogenous expression of HER2. In conclusion, the use of MEDI3379 in combination with trastuzumab in HER2-amplifed breast cancer cell lines has demonstrated additional tumor growth inhibition over single agent trastuzumab and overcoming trastuzumab-resistance mechanisms. This combination warrants further evaluation in preclinical and clinical studies. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A112. Citation Format: Philipp Steiner, Leslie Wetzel, Kevin Schifferli, Raymond Rothstein, Ravinder Tammali, Marlon Rebelatto, Zhan Xiao, Andrew Pierce, Robert Hollingsworth. Combined targeting of HER2 and HER3 inhibits tumor growth in both trastuzumab-sensitive and trastuzumab-resistant breast cancer models. [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 A112.

Abstract 558: MEDI3379, a human monoclonal antibody against HER3, suppresses HER3 activity and cell proliferation in both ligand-dependent and independent cancers.

HER3 (ErbB3) is a member of the EGFR/HER family of receptor tyrosine kinases (RTK), consisting of EGFR, HER2, HER3 and HER4. Due to its unique kinase-deficient nature, HER3 needs to form heterodimers with EGFR, HER2 or other RTKs to be functionally active. Dimerization is induced by either HER3 ligand (Heregulin, HRG) binding, or overexpression of partner RTKs in a ligand-independent (LI) manner. In both settings, HER3 acts as a critical scaffold coupling the upstream RTKs to efficient PI3K/AKT pathway induction to drive tumor growth and survival. We have developed a potent antagonistic human monoclonal antibody against HER3, termed MEDI3379, and tested it in multiple cancer models with either ligand-dependent or ligand-independent HER3 activities. For ligand-dependent models, we have chosen MDA-MB-175VII, a breast cancer cell-line with known γ-HRG expression, and HMCB, a melanoma cell-line with β-HRG expression. Efficient suppression of cell proliferation by MEDI3379 or 2C2, a precursor of MEDI3379, was observed in both models. This anti-tumor effect is directly due to the abrogation of HER3 activation (as determined by pHER3 formation) and its downstream effector pAKT. Her2-amplified breast cancer models such as BT474 are known to display high ligand-independent HER3 activity that is due to constitutive dimerization of HER2 and HER3. Treatment of BT474 with MEDI3379 led to effective suppression of pHER3, pAKT, and cell-proliferation in vitro. We extended this observation in vivo by exploring the antitumor activity of MEDI3379 in several orthotopic HER2-amplified breast cancer xenografts in nude mice. Consistent with in vitro observations, the BT474 xenograft model responded to MEDI3379 treatment with 65% tumor growth inhibition. In contrast, two published HER3 mAbs (Ab #6 and U1-15) failed to display activity in this ligand-independent model. In conclusion, our findings demonstrated that MEDI3379 is a HER3 antagonist that is effective in models of human cancers driven by both ligand-dependent as well as ligand-independent HER3 activities. Citation Format: Carrasco A. Rosa, Leslie Wetzel, Krista Kinner, Hong Chen, Raymond Rothstein, David Tice, Robert Hollingsworth, Philipp Steiner, Zhan Xiao. MEDI3379, a human monoclonal antibody against HER3, suppresses HER3 activity and cell proliferation in both ligand-dependent and independent cancers. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 558. doi:10.1158/1538-7445.AM2013-558

Abstract P4-07-05: MEDI3379, an antibody against HER3, is active in HER2-driven human breast tumor models

HER3 (ERBB3) is a member of the EGFR/HER family of receptor tyrosine kinases (RTK), consisting of EGFR, HER2, HER3 and HER4. Unlike the other HER family members, HER3 lacks intrinsic tyrosine kinase activity and therefore needs to form heterodimers with EGFR, HER2 or other kinase-proficient RTKs to be functionally active. Dimerization is induced by overexpression of EGFR or HER2 in a ligand-independent (LI) manner. In this process HER3 acts as a driver in divergent cancer types including HER2-positive breast cancer (BC) via induction of the PI3K-AKT pathway. Alternatively, heregulin (NRG1/HRG), the major HER3 ligand, induces a conformational shift in HER3 which leads to dimer formation with a partner RTK in a ligand-dependent (LD) manner. We have developed an antagonistic human monoclonal antibody against HER3, termed MEDI3379, and tested it in multiple breast cancer cell lines. We observed effective suppression of constitutive pHER3 and pAKT with MEDI3379, leading to anti-proliferation effects in cell culture models. Preclinical evaluation of MEDI3379 demonstrated antitumor activity in several orthotopic BC xenografts in nude mice which did not express HRG. For example, the BC xenograft model BT474 with amplified HER2 responded to MEDI3379 (65% dTGI). In conclusion, our findings with targeting of HER3 in mouse models support continued development of MEDI3379 for cancer. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-07-05.