CCX559 is a potent, orally-administered small molecule PD-L1 inhibitor that induces anti-tumor immunity

The interaction of PD-L1 with PD-1 is a major immune checkpoint that limits effector T cell function against cancer cells; monoclonal antibodies that block this pathway have been approved in multiple tumor indications. As a next generation therapy, small molecule inhibitors of PD-L1 have inherent drug properties that may be advantageous for certain patient populations compared to antibody therapies. In this report we present the pharmacology of the orally-available, small molecule PD-L1 inhibitor CCX559 for cancer immunotherapy. CCX559 potently and selectively inhibited PD-L1 binding to PD-1 and CD80 in vitro, and increased activation of primary human T cells in a T cell receptor-dependent fashion. Oral administration of CCX559 demonstrated anti-tumor activity similar to an anti-human PD-L1 antibody in two murine tumor models. Treatment of cells with CCX559 induced PD-L1 dimer formation and internalization, which prevented interaction with PD-1. Cell surface PD-L1 expression recovered in MC38 tumors upon CCX559 clearance post dosing. In a cynomolgus monkey pharmacodynamic study, CCX559 increased plasma levels of soluble PD-L1. These results support the clinical development of CCX559 for solid tumors; CCX559 is currently in a Phase 1, first in patient, multicenter, open-label, dose-escalation study (ACTRN12621001342808).

Chromatin Remodeling Drives Immune-Fibroblast Crosstalk in Heart Failure Pathogenesis

Chronic inflammation and tissue fibrosis are common stress responses that worsen organ function, yet the molecular mechanisms governing their crosstalk are poorly understood. In diseased organs, stress-induced changes in gene expression fuel maladaptive cell state transitions and pathological interaction between diverse cellular compartments. Although chronic fibroblast activation worsens dysfunction of lung, liver, kidney, and heart, and exacerbates many cancers, the stress-sensing mechanisms initiating the transcriptional activation of fibroblasts are not well understood. Here, we show that conditional deletion of the transcription co-activator Brd4 in Cx3cr1-positive myeloid cells ameliorates heart failure and is associated with a dramatic reduction in fibroblast activation. Analysis of single-cell chromatin accessibility and BRD4 occupancy in vivo in Cx3cr1-positive cells identified a large enhancer proximal to Interleukin-1 beta (Il1b), and a series of CRISPR deletions revealed the precise stress-dependent regulatory element that controlled expression of Il1b in disease. Secreted IL1B functioned non-cell autonomously to activate a p65/RELA-dependent enhancer near the transcription factor MEOX1, resulting in a profibrotic response in human cardiac fibroblasts. In vivo, antibody-mediated IL1B neutralization prevented stress-induced expression of MEOX1, inhibited fibroblast activation, and improved cardiac function in heart failure. The elucidation of BRD4-dependent crosstalk between a specific immune cell subset and fibroblasts through IL1B provides new therapeutic strategies for heart disease and other disorders of chronic inflammation and maladaptive tissue remodeling.

CCR2 deficiency alters activation of microglia subsets in traumatic brain injury

In traumatic brain injury (TBI), a diversity of brain resident and peripherally derived myeloid cells have the potential to worsen damage and/or to assist in healing. We define the heterogeneity of microglia and macrophage phenotypes during TBI in wild-type (WT) mice and Ccr2^−/− mice, which lack macrophage influx following TBI and are resistant to brain damage. We use unbiased single-cell RNA sequencing methods to uncover 25 microglia, monocyte/macrophage, and dendritic cell subsets in acute TBI and normal brains. We find alterations in transcriptional profiles of microglia subsets in Ccr2^−/− TBI mice compared to WT TBI mice indicating that infiltrating monocytes/macrophages influence microglia activation to promote a type I IFN response. Preclinical pharmacological blockade of hCCR2 after injury reduces expression of IFN-responsive gene, Irf7, and improves outcomes. These data extend our understanding of myeloid cell diversity and crosstalk in brain trauma and identify therapeutic targets in myeloid subsets.

By single-cell RNA sequencing of traumatically injured and normal brains from wild-type and Ccr2^−/− mice, Somebang et al. define microglia, macrophage, and dendritic cell phenotypes in TBI. Targeting mouse and/or human CCR2 reduces specific TBI brain CNS myeloid compartments, dampens type I interferon responses, and improves cognition after TBI.

Abstract 1274: CCX559 is a potent orally-administered small molecule PD-L1 inhibitor that induces anti-tumor immunity

Introduction: Cancer cells can escape tumor-specific T cell responses via engagement of inhibitory immune checkpoints. PD-L1/PD-1 interaction is one of the major checkpoints that limit effector T cell function against cancer cells, and monoclonal antibodies that block this interaction have been approved as therapies in multiple tumor indications. As a next generation therapy, small molecule inhibitors of PD-L1 potentially have advantageous properties compared to approved monoclonal antibodies, such as better penetration into solid tumors, reduced immunogenicity, lack of Fc-mediated side effects, convenience of oral administration, and lower cost of goods. We therefore embarked on an effort to identify and develop an orally available small molecule capable of targeting PD-L1/PD-1 interactions.

Methods: Inhibition of the PD-L1/PD-1 interaction was measured using a binding assay, followed by a cell culture system assessing PD-1 inhibition of T cell receptor (TCR) activation. Human T cell responses were assessed in vitro using the mixed lymphocyte reaction (MLR) assay, and a human peripheral blood mononuclear cell (PBMC)-mediated tumor cell killing assay. For in vivo studies CCX559 was dosed orally in a syngeneic tumor model and in a human tumor cell/PBMC co-implantation model in immune deficient mice.

Results: Using structural information and focused medicinal chemistry, we identified CCX559 as a potent inhibitor of PD-L1 interaction with PD-1. CCX559 prevented PD-L1/PD-1 inhibition of TCR signaling in a cell-based reporter assay, increased IFNγ secretion in allogeneic MLR assays, and increased tumor cell killing by human PBMCs. We demonstrated that CCX559 potentially employs multiple mechanisms to inhibit PD-L1, which are distinct from those published for human anti-PD-L1 antibodies. In murine tumor models, orally administered CCX559 reduced tumor growth similarly to a clinically-approved anti-human PD-L1 antibody.

Summary: CCX559 is a highly potent, small molecule PD-L1 inhibitor that can be orally administered. CCX559 enhanced primary human T cell activity in vitro and demonstrated anti-tumor efficacy in two murine tumor models. Based on its unique mechanism of PD-L1 inhibition, strong anti-tumor activity, desirable drug properties, and good safety profile, we plan to advance CCX559 into clinical development in the first half of 2021.

Citation Format: Chris Li, Marta Vilalta, Linda S. Ertl, Yu Wang, Yibin Zeng, Pingchen Fan, Christopher Lange, Darren McMurtrie, Ju Yang, Rebecca Lui, Ryan Scamp, Vicky Chhina, Alice Kumamoto, Ryan Ong, Ton Dang, Ashton Easterday, Niky Zhao, Shirley Liu, Rajinder Singh, Israel Charo, Kathleen Sullivan, Thomas J. Schall, Penglie Zhang. CCX559 is a potent orally-administered small molecule PD-L1 inhibitor that induces anti-tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1274.

Abstract 5693: Anti-tumor effect of orally available small molecule PD-L1 inhibitors in a murine model of colon adenocarcinoma

Introduction: Antibody-based therapies targeting the Programmed cell Death-1/ Programmed Death-Ligand 1 (PD-1/PD-L1) immune checkpoint axis have achieved great success in cancer immunotherapy in recent years. As a next generation therapy, small molecule inhibitors of PD-1/PD-L1 offer the potential for increased tumor penetration, shorter half-life (to better manage immune related adverse events), and lower cost. We therefore embarked on an effort to identify and develop orally available small molecules capable of targeting PD-L1.

Methods: We designed and optimized a number of small molecule PD-L1 inhibitors which potently disrupted the interaction of PD-1 with PD-L1. Active compounds were first profiled by an ELISA assay measuring inhibition of the PD-1/PD-L1 interaction, followed by a functional cell-based reporter assay, mixed lymphocyte reaction (MLR) assay, and human peripheral blood mononuclear cell (PBMC)-mediated tumor cell killing assay. Targeted medicinal chemistry efforts were employed to improve potency and oral bioavailability, and candidate compounds were then evaluated in murine tumor models. Due to the specific reactivity of these compounds to human PD-L1 (but not murine PD-L1), a syngeneic tumor model with murine MC-38 colon tumor cells expressing human PD-L1 (MC38-hPD-L1 tumor model) was used.

Results: The optimized PD-L1 inhibitors were highly potent in cell-based reporter assay, the MLR assay and PBMC-mediated tumor cell killing assays. These compounds also possess high oral bioavailability and desirable safety profiles. In the MC38-hPD-L1 tumor model, Lead compounds potently reduced tumor growth similarly to an anti-human PD-L1 antibody, which was used as a positive control for the experiments. The tumor microenvironment analysis by flow cytometry demonstrated that these compounds almost completely occupied human PD-L1 on the tumor cells in vivo, and thus could potently block the interaction of PD-1/PD-L1 and enhance the immune responses against tumor.

Summary: We have identified and advanced unique small molecule inhibitors of human PD-L1 by rational design and optimization. Molecules resulting from these efforts exhibited marked inhibition of the PD-1/PD-L1 interaction and signaling in vitro, and potent anti-tumor effects in an animal model.

Citation Format: Shijie "Chris" Li, Marta Vilalta, Linda S. Ertl, Yu Wang, Yibin Zeng, Pingchen Fan, Christopher Lange, Darren McMurtrie, Ju Yang, Rebecca Lui, Ryan Ong, Vicky Chhina, Alice Kumamoto, Simon Yau, Ton Dang, Ashton Easterday, Shirley Liu, Rajinder Singh, Israel Charo, Thomas J. Schall, Penglie Zhang. Anti-tumor effect of orally available small molecule PD-L1 inhibitors in a murine model of colon adenocarcinoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5693.

IMMU-05. DISRUPTION OF THE CCR2 CHEMOKINE RECEPTOR PATHWAY OVERCOMES THERAPEUTIC RESISTANCE TO PD-1 BLOCKADE IN MALIGNANT GLIOMA

INTRODUCTION

Large scale clinical trials have failed to determine efficacy of adjuvant PD-1 blockade in recurrent glioblastoma (GBM). However, recent phase 2 clinical trial results demonstrating the potential of neo-adjuvant anti-PD-1 treatment have renewed enthusiasm for the use of immune checkpoint inhibitors (ICIs) in GBM. Additional benefit of ICIs in GBM will likely derive from development of novel therapies directed against immunosuppressive resistance mechanisms. Chemokine receptor 2 (CCR2) expressing tumor infiltrative immune suppressive myeloid cells represent a targetable axis within ICI resistant gliomas. We have established that CCR2 disruption unmasks an effect of anti-PD-1 therapy in ICI resistant murine glioma models. However, the mechanism(s) by which combined inhibition of PD-1 and CCR2 achieves efficacy is unknown.

OBJECTIVE

Determine the impact of combination anti-PD-1 and CCR2 antagonism on immune cells within anti-PD-1 resistant gliomas.

METHODS

Immune cell characteristics were determined in CCR2 antagonist (CCX872)/anti-PD-1 treated KR158 or 005 GSC glioma-bearing wild type or CCR2+/rfp/CX3CR1+/gfp reporter mice.

RESULTS

CCX872 increased median survival (32 vs. 50 days, P=.002) in KR158 tumor-bearing animals and in combination with anti-PD-1 significantly increased durable survival (P=.0005). In 005 GSC glioma-bearing mice, combination therapy also enhanced median survival (30 vs. 49 days, P=.005). CCX872 decreased CD45+/CD11bhi/Ly6Chi MDSCs (40%, P=.038) within gliomas, and increased these cells within bone marrow in both models (74%, P=.020). Three distinct intra-tumoral populations of CCR2+ and CX3CR1+ cells were identified in both glioma models including CCR2+/CX3CR1-/CD45hi/CD11blo, CCR2+/CX3CR1+/CD45hi/CD11bhi/Ly6Chi, and CX3CR1+/CD45lo/CD11bhi/F4/80+/MHCII+, with both CCR2+ populations being reduced by CCX872 treatment. Examination of tumor infiltrating lymphocytes revealed both increased presence and decreased exhaustion (PD-1+/Tim3+) of CD4+ (P=.029) and CD8+ (P=.011) T-cells following CCX872/anti-PD-1 treatment.

CONCLUSION

CCX872/anti-PD-1 combination therapy is effective in clinically relevant murine glioma models, providing a basis to progress this novel combinatorial treatment to human clinical trials.

CC chemokine receptor 2 promotes recruitment of myeloid cells associated with insulin resistance in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a common disease, closely associated with obesity and insulin resistance. We investigated the presence of a subset of myeloid cells associated with metabolic disturbance in the liver of patients with NAFLD and a murine model of obesity-induced liver disease. Gene and protein expression in liver and serum was investigated with RT-PCR or ELISA and correlated to clinical disease. Liver-infiltrating immune cells were isolated from normal or diseased human liver for flow cytometric analysis. In animal experiments, mice were fed a high-fat diet (60% of calories from fat) for 16 wk, or high-fat diet with 30% fructose for 32 wk to induce steatohepatitis and fibrosis. A small molecule inhibitor of CC chemokine receptor 2 (CCR2), CCX872, was administered to some mice. A subset of CD11c⁺CD206⁺ immune cells was enriched in human liver tissue, and greater infiltration was observed in NAFLD. The presence of CD11c⁺CD206⁺ myeloid cells correlated with systemic insulin resistance. CD11c⁺CD206⁺ cells expressed high levels of CCR2, and liver CC chemokine ligand 2 (CCL2) expression was increased in nonalcoholic steatohepatitis and correlated with disease activity. In mice, CCR2 inhibition reduced infiltration of liver CD11b⁺CD11c⁺F4/80⁺ monocytes, which are functional homologs of human CD11c⁺CD206⁺ cells, and improved liver injury and glycemic control. A role for CCR2/CCL2 in human NAFLD has long been postulated. These data confirm a role for this chemokine/receptor axis, through mediating adipose and hepatic infiltration of myeloid cells. Inhibition of CCR2 improved hepatic inflammation and fibrosis in murine models of NAFLD. These data confirm the rationale for targeting CCR2 to treat NAFLD. NEW & NOTEWORTHY These data show for the first time that CD11c⁺CD206⁺ myeloid cells, previously associated with human adipose tissue inflammation, infiltrate into liver tissue in nonalcoholic fatty liver disease. These cells express CCR2. Inhibition of CCR2 in mice inhibits hepatic inflammation caused by a murine homolog of these myeloid cells and improves experimental liver disease.

Abstract 5655: Inhibition of CCR2 potentiates checkpoint inhibitor immunotherapy in murine model of pancreatic cancer

Pancreatic cancer is an aggressive malignancy with a 5 year survival rate of less than five percent. The predominant immune cells infiltrating the tumor microenvironment are monocytes/macrophages, which are reported to support tumor growth by suppressing host immune responses to the tumor. Recruitment of monocytes to various tissues, including tumors, is dependent upon activation of the chemokine receptor CCR2 by one or more of the chemokines CCL2, CCL8 and CCL13. In preclinical and clinical studies, inhibition of CCR2 in pancreatic cancer has shown to decrease tumor progression by blocking recruitment and accumulation of monocytes/macrophages in the tumor microenvironment. Analysis of human pancreatic tumors revealed elevation of both CCL2 and CSF1, which recruit monocytes, as well as the monocyte marker CD14, in advanced pancreatic cancers. Current immunotherapy using checkpoint inhibitors are effective in some tumors, but lack efficacy in immune insensitive cancers, including pancreatic cancer. Here, we report that the inhibition of CCR2 using a small molecule antagonist potentiates anti-PD-1 immunotherapy in a syngeneic, orthotropic mouse model of pancreatic cancer. Our data reveal that blocking CCR2 decreases tumor burden by blocking monocyte infiltration and creating a microenvironment more favorable for CD8 T cells activity, and provide a mechanistic rationale for investigating the combination of a CCR2 antagonist and an immune checkpoint inhibitor in pancreatic cancer.

Citation Format: Christine Janson, Heiyoun Jung, Linda Ertl, Shirley Liu, Ton Dang, Yibin Zeng, Antoni Krasinski, Jeff McMahon, Penglie Zhang, Israel Charo, Rajinder Singh, Thomas J. Schall. Inhibition of CCR2 potentiates checkpoint inhibitor immunotherapy in murine model of pancreatic cancer [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 5655. doi:10.1158/1538-7445.AM2017-5655

Orally administered CCR2 selective inhibitor CCX872-b clinical trial in pancreatic cancer

276

Background: CCR2 inhibition decreases tumor-associated macrophages and Treg cells, and increases CD8+ and CD4+ T cells in pancreatic tumors. Single oral doses of 150 mg CCX872-B were well tolerated in patients with pancreatic cancer. The first stage results of the multiple dose part of this study are presented. Methods: Patients with locally advanced or metastatic pancreatic cancer, ECOG score ≤ 2 were studied. Patients received FOLFIRINOX (fluorouracil [5-FU], leucovorin, irinotecan, oxaliplatin) q2weeks for up to 24 wks plus 150 mg CCX872-B once or twice daily until disease progression or intolerance to CCX872-B. The primary efficacy endpoint is progression-free survival (PFS) at 24 wks. Tumor control rate (TCR) and the objective response rate (ORR), a secondary endpoint, are presented. Results: Fifty patients were enrolled. Baseline: Mean ± SD age: 60 ± 8.6 years, male 52%; primary tumor location: head 57%, body/tail 41%, local recurrence 2%; metastatic disease 78%, ECOG score 0: 62%, ECOG score 1: 38%. Thirty five of 50 patients completed week 12. Most common reasons for early withdrawal were subject request (5 pts) and adverse events typically associated with FOLFIRINOX (4 pts). In the pre-specified analysis population, i.e., those with ≥ 1 post baseline CT scan, tumor control at wk 12 was achieved in 32 of 41 (78%) patients, with 15 of 41 (37%) partial responders, and 17 of 41 (41%) with stable disease. The ORR was 37% (all partial responders) in the primary analysis population (30% when all enrolled patients were included). Thirteen of 21 patients with available CT scan results at week 24 were progression-free. Mean trough CCX872 plasma level was ~8 μg/mL. CCR2 was covered 88% on average by CCX872-B based on receptor occupancy assays. CCX872-B appeared to be well tolerated and the incidence of ≥ Gr 3 AEs was not increased with CCX872-B plus FOLFIRINOX vs historical data with FOLFIRINOX alone. The complete set of PFS data will be available by the end of 2016. Conclusions: CCX872-B plus FOLFIRINOX resulted in a TCR of 78% and an ORR of 30 to 37% with no safety issues ascribed to CCX872-B use. Clinical trial information: NCT02345408.

Abstract A107: Inhibition of CCR2 potentiates the checkpoint inhibitor immunotherapy in pancreatic cancer

Pancreatic cancer is an aggressive malignancy with 5 year survival rate of less than 5 percent. The predominant immune cells infiltrating the tumor microenvironment are monocytes/macrophages, which are reported to support tumor growth by suppressing host immune responses to the tumor. Recruitment of monocytes to various tissues, including tumors, is dependent upon activation of the chemokine receptor CCR2 by one or more of the chemokines CCL2, CCL8 and CCL13. In preclinical and clinical studies, inhibition of CCR2 in pancreatic cancer has shown to decrease tumor progression by blocking recruitment and accumulation of monocytes/macrophages in the tumor microenvironment. Analysis of the TCGA genomic database of human pancreatic tumors revealed elevation of both CCL2 and CSF1, which recruit monocytes, as well as the monocyte marker CD14, in advanced pancreatic cancers. Current immunotherapy using checkpoint inhibitors are effective in some tumors, but lack efficacy in immune insensitive cancers, including pancreatic cancer. Here, we report that the inhibition of CCR2 using small molecule antagonist potentiates anti-PD-1/PD-L1 immunotherapy in a syngeneic, orthotopic mouse model of pancreatic cancer. The KCKO pancreatic cancer cell line, which harbors a K-ras mutation, was implanted into the tail of the pancreas, and a small molecule CCR2 antagonist was administered after a stable tumor mass had formed. Tumor weight correlated well with the per cent of circulating monocytes in the peripheral blood, and the CCR2 antagonist significantly decreased the blood monocyte count. Similar to the human tumor stroma, the KCKO mouse tumors were infiltrated with monocytes and macrophages, and CCR2 antagonist treatment decreased the infiltration of monocyte/ macrophage. PD-L1 expressions are found in the human pancreatic tumor microenvironment, but treatment of patients with anti-PD-1 has not been found to have efficacy. Similarly, anti-PD-1 treatment alone was not effective in the murine KCKO model, but combination treatment with a CCR2 antagonist resulted in significantly smaller tumors. Moreover, this effect was completely reversed by depleting CD8 T cells, suggesting that by blocking monocyte/macrophage recruitment, the CCR2 antagonist relieved suppression of the CD8 T cells. We confirmed this hypothesis by demonstrating that cells from the KCKO tumor microenvironment inhibited CD3/CD28-induced proliferation of CD8 T cells in culture, but that this inhibition was not present when the mice had received the CCR2 antagonist. Taken together, these data reveal that blocking CCR2 decreases tumor burden by blocking monocyte infiltration and creating a microenvironment more favorable for CD8 T cells activity, and provide a mechanistic rationale for investigating the combination of a CCR2 antagonist and an immune checkpoint inhibitor in pancreatic cancer.

Citation Format: Heiyoun Jung, Linda Ertl, Christine Janson, Thomas Schall, Israel Charo. Inhibition of CCR2 potentiates the checkpoint inhibitor immunotherapy in pancreatic cancer [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 A107.

Characterization of Pharmacologic and Pharmacokinetic Properties of CCX168, a Potent and Selective Orally Administered Complement 5a Receptor Inhibitor, Based on Preclinical Evaluation and Randomized Phase 1 Clinical Study

The complement 5a receptor has been an attractive therapeutic target for many autoimmune and inflammatory disorders. However, development of a selective and potent C5aR antagonist has been challenging. Here we describe the characterization of CCX168 (avacopan), an orally administered selective and potent C5aR inhibitor. CCX168 blocked the C5a binding, C5a-mediated migration, calcium mobilization, and CD11b upregulation in U937 cells as well as in freshly isolated human neutrophils. CCX168 retains high potency when present in human blood. A transgenic human C5aR knock-in mouse model allowed comparison of the in vitro and in vivo efficacy of the molecule. CCX168 effectively blocked migration in in vitro and ex vivo chemotaxis assays, and it blocked the C5a-mediated neutrophil vascular endothelial margination. CCX168 was effective in migration and neutrophil margination assays in cynomolgus monkeys. This thorough in vitro and preclinical characterization enabled progression of CCX168 into the clinic and testing of its safety, tolerability, pharmacokinetic, and pharmacodynamic profiles in a Phase 1 clinical trial in 48 healthy volunteers. CCX168 was shown to be well tolerated across a broad dose range (1 to 100 mg) and it showed dose-dependent pharmacokinetics. An oral dose of 30 mg CCX168 given twice daily blocked the C5a-induced upregulation of CD11b in circulating neutrophils by 94% or greater throughout the entire day, demonstrating essentially complete target coverage. This dose regimen is being tested in clinical trials in patients with anti-neutrophil cytoplasmic antibody-associated vasculitis.

Trial Registration ISRCTN registry with trial ID ISRCTN13564773.

Abstract 564: Combination therapy of chemokine receptor inhibition plus PD-L1 blockade potentiates antitumor effects in a murine model of breast cancer

Trafficking and expansion of myeloid derived suppressor cells (MDSCs) plays a major role in the immune suppression of tumors. MDSCs express chemokine receptors which likely mediate their recruitment to the tumor microenvironment. Suppression of T cells is also mediated by the interaction of programmed death-1 (PD-1) and its ligands which are abundantly expressed in cancer cells and immune infiltrates, including MDSCs. Here, we show that targeting both pathways through administration of a small molecule chemokine receptor antagonist (CCX9588, which blocks CCR1) and a PD-L1 monoclonal antibody (mAb) significantly reduced tumor burden in mice who received orthotopic transplants of 4T1 cells, a cell line used to model triple negative breast cancer. Primary tumor growth was modestly reduced by either agent (PD-L1 mAb or CCR1 inhibitor) alone, but the combination of CCR1 inhibitor plus PD-L1 mAb resulted in significantly reduced tumor progression as compared to either of the single agents. Furthermore, lung metastasis was also significantly reduced by CCR1 antagonist and combination treatment. Orthotropic 4T1 cell engraftment induced robust expansion of CD11b+Ly6Ghi Ly6Chi MDSCs, a subpopulation of which express CCR1. Analysis of the tumor infiltrating cells revealed that CCX9588 significantly reduced the number of MDSCs and increased CD8 T cells infiltration in primary tumors, suggesting that CCR1 blockade of MDSC trafficking in combination with PD-L1 mAb translates into reduced tumor burden, possibly through increased CD8 T cell response against the tumor. Analysis of human breast cancer patient samples from The Cancer Genome Atlas (TCGA) database revealed that the CCR1 ligands, MCP-7 (CCL7) and RANTES (CCL5) are present at significantly higher levels in breast cancers as compared to normal breast tissue. Interestingly, ligands for CCR1 and PD-1 are significantly higher in triple negative breast cancer samples than in the other breast cancer subtypes. These data are the first to show that CCR1 chemokine receptor antagonists can act synergistically with PDL-1 inhibitors, and suggest a novel approach for potentiating the activity of immune cell checkpoint inhibitors in one of the most aggressive forms of breast cancer.

Citation Format: Heiyoun Jung, Linda Ertl, Karen Ebsworth, Christine Janson, Penglie Zhang, Punna Sreenivas, Thomas Schall, Israel Charo. Combination therapy of chemokine receptor inhibition plus PD-L1 blockade potentiates antitumor effects in a murine model of 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 564.

Abstract B24: Pharmacokinetic and pharmacodynamic profile of the novel, oral and selective CCR2 inhibitor CCX872-B in a Phase 1B pancreatic cancer trial

Introduction: The monocyte chemoattractant protein-1/ chemokine receptor 2 (CCR2) axis regulates the recruitment of inflammatory monocytes to sites of inflammation and cancer. CCR2 inhibition in preclinical models has resulted in diminished numbers of tumor-infiltrating immuno-suppressive macrophages and decreased pancreatic tumor size. Recently, a clinical trial with a different CCR2 inhibitor, PF-4136309, reported increased response rate from 28% historically (FOLFIRINOX alone, fluorouracil [5-FU], leucovorin, irinotecan, oxaliplatin) to 48% (FOLFIRINOX plus CCR2 inhibitor) at 12 weeks. CCX872-B is a potent, oral CCR2 inhibitor with a favorable PK profile compared to PF-4136309. In a Phase 1 healthy volunteer study, single and multiple doses of CCX872-B ranging from 3 to 300 mg were explored. CCX872-B was well-tolerated, with a dose-linear pharmacokinetic (PK) profile and dose-dependent blockade of CCR2 on circulating monocytes in receptor occupancy (RO) and internalization (RI) assays.

Experimental Procedures: This ongoing clinical trial consists of a single-dose CCX872-B regimen in Part A which has been completed in 4 patients with pancreatic adenocarcinoma, followed by a multiple dose Part B regimen in up to 50 additional patients, in combination with FOLFIRINOX therapy for up to 12 cycles. Each patient in Part A received one dose of 150 mg CCX872-B. PK, pharmacodynamics (PD), and safety were evaluated on Days 1, 4, and 8. PD was assessed via blockade of CCR2 by CCX872-B. Patient plasma obtained pre-dose, 2 hr, and 12 hr post dose was mixed with human CD14+ monocytes, and was used to measure monocyte migration at EC50 and EC90 of MCP-1, the principal ligand for CCR2, in a chemotaxis assay. Patient plasma obtained as above and mixed with human monocytes was used to measure Alexa Fluor ®-labeled MCP-1 in RO (4°C) and RI (37 °C) assays via flow cytometry.

Results: CCX872-B was well tolerated by all subjects. Mean Cmax was 8580 ng/mL, AUClast was 164,000 hr*ng/mL, and terminal t1/2 was 35h. Mean% CCR2 coverage, based on migration, RO, and RI assays, respectively, was 95%, 98%, and 95% at 2h post dose, and 86%, 84%, and 73% at 12h post dose. With an expected 4-5 fold accumulation at steady state dosing, CCR2 coverage of ≥90% is anticipated with a twice daily (BID) dosing regimen.

Conclusions: The safety, PK, and PD data of CCX872-B in pancreatic cancer patients, consistent with healthy volunteer data, support BID dosing of 150 mg CCX872-B to provide excellent CCR2 blockade in Part B of this ongoing trial. Currently, 4 patients with non-resectable pancreatic cancer have been enrolled in Part B. All patients will receive either 150 mg CCX872-B once daily or BID for at least 12 weeks combined with FOLFIRINOX for up to 12 cycles. Patients with stable disease may continue treatment beyond 12 weeks. The primary endpoint of this study is the progression free survival at week 24, aiming to improve this rate from 50% with FOLFIRINOX alone historically to at least 60%.

Citation Format: Aram Hezel, Ferry Eskens, Stefan Sleijfer, Marcus Noel, Andrea Wang-Gillam, Sabrina Cheng, Antonia Potarca, Bin Zhao, Lisa Lohr, Shichang Miao, Israel Charo, Pirow Bekker, Thomas J. Schall. Pharmacokinetic and pharmacodynamic profile of the novel, oral and selective CCR2 inhibitor CCX872-B in a Phase 1B pancreatic cancer trial. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B24.

Abstract CT223: CCX872: Pharmacodynamic study of a potent and selective CCR2 antagonist in human volunteers and plans for phase Ib trial in patients with pancreatic cancer

Recent clinical results have highlighted the importance of myeloid-derived suppressor cells in enhancing the ability of the host immune system to limit the growth of tumors. Chemokine receptors control the directed trafficking and persistence of peripheral blood mononuclear cells, including effector and suppressor cells, to the tumor microenvironment. Myeloid derived suppressor cells in particular express high levels of the chemokine receptor CCR2, and pre-clinical data suggests that CCR2 plays an important role in the recruitment of these suppressor cells to tumors. Here we report pharmacodynamic details of a potent and selective small molecule antagonist of CCR2, CCX872, and our plans for a phase Ib trial in patients with pancreatic cancer.

CCX872 has been successfully evaluated in a phase I single and multiple ascending dose study (3 to 300 mg) in 40 healthy volunteers. All dose levels were well tolerated and safe. CCX872-B showed a dose-linear PK profile. Ex vivo CCR2 occupancy and internalization assays revealed that blood monocytes from CCX872, but not placebo-treated subjects, were impaired in their ability to bind to or internalize exogenously added CCL2, indicating that CCX872 blocked CCR2 in the treated subjects. The 300 mg daily dose of CCX872 exhibited 104 ± 3% blockade at 2 hours and 93 ± 7% blockade at 24 hours. We calculated that 150 mg twice a day would provide over 90% CCR2 inhibition at all times.

Analysis of data from the Tumor Cancer Genome Atlas revealed high levels of expression of CCL2 in pancreatic tumors, and co-expression of CCR2 with monocyte/macrophage markers such as CD68 and CSF1R. In pre-clinical studies, we found that a CCR2 antagonist reduced the growth of the pancreatic tumor cell line, PancO2, in rodent xenograft models. Based in part on these data we have initiated a phase Ib single arm, open label, multicenter study of CCX872 in patients with un-resectable pancreatic cancer. In Part A, subjects will receive a single dose of CCX872 for pharmacokinetic and pharmacodynamics analyses. In Part B, up to 50 subjects will be treated for at least 12 weeks with CCX872 in addition to FOLFIRINOX (5-fluorouracil, leucovorin, irinotecan, and oxaliplatin). Responders and those with stable disease after 12 weeks will continue treatment until disease progression, unacceptable toxicity or death. The primary endpoints are safety/tolerability and efficacy (progression-free rate at 6 months based on RECIST criteria). Other endpoints include overall survival, and effect on the tumor microenvironment and immunological biomarkers in the blood. This trial will test the hypothesis that CCR2 plays an important role in enabling the myeloid suppressor cell response to pancreatic cancer, and will determine if addition of a CCR2 antagonist can enhance the standard of care for these patients

Citation Format: Anne-Marie Duliege, Stefan Sleijfer, Ashley Bischof, Joanne Tan, Penglie Zhang, Lisa Seitz, Daniel Dairaghi, Pirow Bekker, Israel Charo, Thomas Schall. CCX872: Pharmacodynamic study of a potent and selective CCR2 antagonist in human volunteers and plans for phase Ib trial in patients with pancreatic cancer. [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 CT223. doi:10.1158/1538-7445.AM2015-CT223

CCR2 deficiency impairs macrophage infiltration and improves cognitive function after traumatic brain injury

Traumatic brain injury (TBI) provokes inflammatory responses, including a dramatic rise in brain macrophages in the area of injury. The pathway(s) responsible for macrophage infiltration of the traumatically injured brain and the effects of macrophages on functional outcomes are not well understood. C-C-chemokine receptor 2 (CCR2) is known for directing monocytes to inflamed tissues. To assess the role of macrophages and CCR2 in TBI, we determined outcomes in CCR2-deficient (Ccr2(-/-)) mice in a controlled cortical impact model. We quantified brain myeloid cell numbers post-TBI by flow cytometry and found that Ccr2(-/-) mice had greatly reduced macrophage numbers (∼80-90% reduction) early post-TBI, compared with wild-type mice. Motor, locomotor, and cognitive outcomes were assessed. Lack of Ccr2 improved locomotor activity with less hyperactivity in open field testing, but did not affect anxiety levels or motor coordination on the rotarod three weeks after TBI. Importantly, Ccr2(-/-) mice demonstrated greater spatial learning and memory, compared with wild-type mice eight weeks after TBI. Although there was no difference in the volume of tissue loss, Ccr2(-/-) mice had significantly increased neuronal density in the CA1-CA3 regions of the hippocampus after TBI, compared with wild-type mice. These data demonstrate that Ccr2 directs the majority of macrophage homing to the brain early after TBI and indicates that Ccr2 may facilitate harmful responses. Lack of Ccr2 improves functional recovery and neuronal survival. These results suggest that therapeutic blockade of CCR2-dependent responses may improve outcomes following TBI.

The transcriptional repressor BLIMP1 curbs host defenses by suppressing expression of the chemokine CCL8

The transcriptional repressor B lymphocyte-induced maturation protein 1 (BLIMP1) is a master regulator of B and T cell differentiation. To examine the role of BLIMP1 in innate immunity, we used a conditional knockout (CKO) of Blimp1 in myeloid cells and found that Blimp1 CKO mice were protected from lethal infection induced by Listeria monocytogenes. Transcriptome analysis of Blimp1 CKO macrophages identified the murine chemokine (C-C motif) ligand 8, CCL8, as a direct target of Blimp1-mediated transcriptional repression in these cells. BLIMP1-deficient macrophages expressed elevated levels of Ccl8, and consequently Blimp1 CKO mice had higher levels of circulating CCL8, resulting in increased neutrophils in the peripheral blood, promoting a more aggressive antibacterial response. Mice lacking the Ccl8 gene were more susceptible to L. monocytogenes infection than were wild-type mice. Although CCL8 failed to recruit neutrophils directly, it was chemotactic for γ/δ T cells, and CCL8-responsive γ/δ T cells were enriched for IL-17F. Finally, CCL8-mediated enhanced clearance of L. monocytogenes was dependent on γ/δ T cells. Collectively, these data reveal an important role for BLIMP1 in modulating host defenses by suppressing expression of the chemokine CCL8.

CCR2 antagonist CCX140-B provides renal and glycemic benefits in diabetic transgenic human CCR2 knockin mice

Chemokine (C-C motif) receptor 2 (CCR2) is central for the migration of monocytes into inflamed tissues. The novel CCR2 antagonist CCX140-B, which is currently in two separate phase 2 clinical trials in diabetic nephropathy, has recently been shown to reduce hemoglobin A1c and fasting blood glucose levels in type 2 diabetics. In this report, we describe the effects of this compound on glycemic and renal function parameters in diabetic mice. Since CCX140-B has a low affinity for mouse CCR2, transgenic human CCR2 knockin mice were generated and rendered diabetic with either a high-fat diet (diet-induced obesity) or by deletion of the leptin receptor gene (db/db). CCX140-B treatment in both models resulted in decreased albuminuria, which was associated with decreased glomerular hypertrophy and increased podocyte density. Moreover, treatment of diet-induced obese mice with CCX140-B resulted in decreased levels of fasting blood glucose and insulin, normalization of homeostatic model assessment of insulin resistance values, and decreased numbers of adipose tissue inflammatory macrophages. Unlike other CCR2 antagonists, CCX140-B had no effect on plasma levels of the CCR2 ligand CCL2 or on the numbers of blood monocytes. These results support the ongoing evaluation of this molecule in diabetic subjects with impaired renal function.

Inhibition of chemokine-glycosaminoglycan interactions in donor tissue reduces mouse allograft vasculopathy and transplant rejection

BACKGROUND

Binding of chemokines to glycosaminoglycans (GAGs) is classically described as initiating inflammatory cell migration and creating tissue chemokine gradients that direct local leukocyte chemotaxis into damaged or transplanted tissues. While chemokine-receptor binding has been extensively studied during allograft transplantation, effects of glycosaminoglycan (GAG) interactions with chemokines on transplant longevity are less well known. Here we examine the impact of interrupting chemokine-GAG interactions and chemokine-receptor interactions, both locally and systemically, on vascular disease in allografts.

METHODOLOGY/PRINCIPAL FINDINGS

Analysis of GAG or CC chemokine receptor 2 (CCR2) deficiency were coupled with the infusion of viral chemokine modulating proteins (CMPs) in mouse aortic allograft transplants (n = 239 mice). Inflammatory cell invasion and neointimal hyperplasia were significantly reduced in N-deacetylase-N-sulfotransferase-1 (Ndst1(f/f)TekCre(+)) heparan sulfate (GAG)-deficient (Ndst1(-/-), p<0.044) and CCR2-deficient (Ccr2(-/-), p<0.04) donor transplants. Donor tissue GAG or CCR2 deficiency markedly reduced inflammation and vasculopathy, whereas recipient deficiencies did not. Treatment with three CMPs was also investigated; Poxviral M-T1 blocks CC chemokine receptor binding, M-T7 blocks C, CC, and CXC GAG binding, and herpesviral M3 binds receptor and GAG binding for all classes. M-T7 reduced intimal hyperplasia in wild type (WT) (Ccr2(+/+), p< or =0.003 and Ccr2(-/-), p

CONCLUSIONS/SIGNIFICANCE

Interruption of chemokine-GAG interactions, even in the absence of chemokine-receptor blockade, is a highly effective approach to reduction of allograft rejection, reducing vascular inflammation and prolonging allograft survival. Although chemokines direct both local and systemic cell migration, interruption of inherent chemokine responses in the donor tissue unexpectedly had a greater therapeutic impact on allograft vasculopathy.

Collapse

Key Words Collapse

MESH Headings

• Animals
• Aorta/drug effects
• Aorta/pathology
• Aorta/transplantation
• Cell Movement/drug effects
• Cell Proliferation/drug effects
• Chemokines/metabolism
• Chemokines/pharmacology
• Disease Models, Animal
• Glycosaminoglycans/metabolism
• Graft Rejection/complications
• Graft Rejection/enzymology
• Graft Rejection/immunology
• Hyperplasia
• Inflammation/complications
• Inflammation/pathology
• Kidney Transplantation
• Mice
• Mice, Inbred BALB C
• Mice, Inbred C57BL
• Receptors, CCR2/deficiency
• Receptors, CCR2/metabolism
• Sulfotransferases/deficiency
• Sulfotransferases/metabolism
• Survival Analysis
• Tissue Donors
• Transplantation, Homologous
• Tunica Intima/drug effects
• Tunica Intima/pathology
• Vascular Diseases/complications
• Vascular Diseases/enzymology
• Vascular Diseases/immunology
• Vascular Diseases/pathology
• Viral Proteins/pharmacology

Collapse

Grants

• RC1 HL100202 NHLBI NIH HHS
• 1RC1HL100202-01 NHLBI NIH HHS
• MOP 577578 CIHR

Collapse

Affiliation(s)

Erbin Dai Vascular Biology Research Group, Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada Division of Cardiovascular Medicine, University of Florida, Gainesville, Florida, United States of America Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida, United States of America
Li-Ying Liu Vascular Biology Research Group, Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada Division of Cardiovascular Medicine, University of Florida, Gainesville, Florida, United States of America Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida, United States of America
Hao Wang Departments of Medicine and Surgery, and Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada
Dana McIvor Departments of Medicine and Surgery, and Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada
Yun ming Sun Vascular Biology Research Group, Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada Viron Therapeutics, Inc., London, Ontario, Canada
Colin Macaulay Viron Therapeutics, Inc., London, Ontario, Canada
Elaine King Viron Therapeutics, Inc., London, Ontario, Canada
Ganesh Munuswamy-Ramanujam Vascular Biology Research Group, Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada Division of Cardiovascular Medicine, University of Florida, Gainesville, Florida, United States of America Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida, United States of America
Mee Yong Bartee Division of Cardiovascular Medicine, University of Florida, Gainesville, Florida, United States of America Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida, United States of America
Jennifer Williams Division of Cardiovascular Medicine, University of Florida, Gainesville, Florida, United States of America Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida, United States of America
Jennifer Davids Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida, United States of America
Israel Charo Gladstone Institute, San Francisco, California, United States of America
Grant McFadden Departments of Medicine and Surgery, and Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida, United States of America
Jeffrey D. Esko Department of Cellular and Molecular Medicine, University of California San Diego, San Diego, California, United States of America
Alexandra R. Lucas Vascular Biology Research Group, Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada Departments of Medicine and Surgery, and Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada Division of Cardiovascular Medicine, University of Florida, Gainesville, Florida, United States of America Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida, United States of America

Collapse

CX3CR1+ CD115+ CD135+ common macrophage/DC precursors and the role of CX3CR1 in their response to inflammation

CX₃CR1 expression is associated with the commitment of CSF-1R⁺ myeloid precursors to the macrophage/dendritic cell (DC) lineage. However, the relationship of the CSF-1R⁺ CX₃CR1⁺ macrophage/DC precursor (MDP) with other DC precursors and the role of CX₃CR1 in macrophage and DC development remain unclear. We show that MDPs give rise to conventional DCs (cDCs), plasmacytoid DCs (PDCs), and monocytes, including Gr1⁺ inflammatory monocytes that differentiate into TipDCs during infection. CX₃CR1 deficiency selectively impairs the recruitment of blood Gr1⁺ monocytes in the spleen after transfer and during acute Listeria monocytogenes infection but does not affect the development of monocytes, cDCs, and PDCs.

CCR2 regulates development of Theiler's murine encephalomyelitis virus-induced demyelinating disease

Theiler's murine encephalomyelitis virus (TMEV)-induced demyelinating disease, a murine model for multiple sclerosis, involves recruitment of T cells and macrophages to the CNS after infection. We hypothesized that CCR2, the only known receptor for CCL2, would be required for TMEV-induced demyelinating disease development because of its role in macrophage recruitment. TMEV-infected SJL CCR2 knockout (KO) mice showed decreased long-term clinical disease severity and less demyelination compared with controls. Flow cytometric data indicated that macrophages (CD45(high) CD11b(+) ) in the CNS of TMEV-infected CCR2 KO mice were decreased compared with control mice throughout disease. CD4(+) and CD8(+) T cell percentages in the CNS of TMEV-infected control and CCR2 KO mice were similar over the course of disease. There were no apparent differences between CCR2 KO and control peripheral immune responses. The frequency of interferon-gamma-producing T cells in response to proteolipid protein 139-151 in the CNS was also similar during the autoimmunity stage of TMEV-induced demyelinating disease. These data suggest that CCR2 is important for development of clinical disease by regulating macrophage accumulation after TMEV infection.

Chemokine regulation of the inflammatory response to a low-dose influenza infection in CCR2-/- mice

Influenza virus infections induce chemokines and cytokines, which regulate the immune response. The chemokine receptor CCR2 plays an important role in macrophage recruitment and in the development of T1 immunity. In the present study, we addressed the role of CCR2 in influenza A virus infection. CCR2 knockout (-/-) mice are protected against influenza A virus infection, despite delayed recruitment of macrophages. We show that low-dose influenza infection of CCR2-/- mice leads to increased neutrophilia between Days 5 and 10 after infection and decreased monocyte/macrophage and CD4(+) T cell recruitment to the lungs between Days 5 and 7 after infection. These changes in leukocyte recruitment did not result from or cause increased viral titers or delayed viral clearance. Neutrophilia in the lungs correlated with increased keratinocyte-derived chemokine (KC) and/or MIP-2 expression in CCR2-/- mice between Days 5 to 10 after infection, although the kinetics of neutrophil recruitment was not altered. MIP-2 mRNA and protein expression was increased three- to fivefold, and KC protein levels were increased two- to threefold in CCR2-/- compared with CCR2 wild-type mice at Day 5 after infection. This preceded the peak neutrophil influx, which occurred 7 days after infection. In vitro studies confirmed that MIP-2 and KC accounted for neutrophil chemotactic activity in the bronchoalveolar lavage. CCR2 deficiency also resulted in increased MIP-1alpha, MIP-1beta, MCP-1, and IFN-inducible protein 10 and decreased RANTES mRNA expression. Furthermore, IL-6 and TNF-alpha cytokine production were elevated after infection. These studies suggest that CCR2 plays a multifactorial role in the development of the immune response to influenza.

CCR2 modulates inflammatory and metabolic effects of high-fat feeding

The C-C motif chemokine receptor-2 (CCR2) regulates monocyte and macrophage recruitment and is necessary for macrophage-dependent inflammatory responses and the development of atherosclerosis. Although adipose tissue expression and circulating concentrations of CCL2 (also known as MCP1), a high-affinity ligand for CCR2, are elevated in obesity, the role of CCR2 in metabolic disorders, including insulin resistance, hepatic steatosis, and inflammation associated with obesity, has not been studied. To determine what role CCR2 plays in the development of metabolic phenotypes, we studied the effects of Ccr2 genotype on the development of obesity and its associated phenotypes. Genetic deficiency in Ccr2 reduced food intake and attenuated the development of obesity in mice fed a high-fat diet. In obese mice matched for adiposity, Ccr2 deficiency reduced macrophage content and the inflammatory profile of adipose tissue, increased adiponectin expression, ameliorated hepatic steatosis, and improved systemic glucose homeostasis and insulin sensitivity. In mice with established obesity, short-term treatment with a pharmacological antagonist of CCR2 lowered macrophage content of adipose tissue and improved insulin sensitivity without significantly altering body mass or improving hepatic steatosis. These data suggest that CCR2 influences the development of obesity and associated adipose tissue inflammation and systemic insulin resistance and plays a role in the maintenance of adipose tissue macrophages and insulin resistance once obesity and its metabolic consequences are established.

Differential role of CCR2 in islet and heart allograft rejection: tissue specificity of chemokine/chemokine receptor function in vivo

Chemokines have a pivotal role in the mobilization and activation of specific leukocyte subsets in acute allograft rejection. However, the role of specific chemokines and chemokine receptors in islet allograft rejection has not been fully elucidated. We now show that islet allograft rejection is associated with a steady increase in intragraft expression of the chemokines CCL8 (monocyte chemoattractant protein-2), CCL9 (monocyte chemoattractant protein-5), CCL5 (RANTES), CXCL-10 (IFN-gamma-inducible protein-10), and CXCL9 (monokine induced by IFN-gamma) and their corresponding chemokine receptors CCR2, CCR5, CCR1, and CXCR3. Because CCR2 was found to be highly induced, we tested the specific role of CCR2 in islet allograft rejection by transplanting fully MHC mismatched islets from BALB/c mice into C57BL/6 wild-type (WT) and CCR2-deficient mice (CCR2-/-). A significant prolongation of islet allograft survival was noted in CCR2-/- recipients, with median survival time of 24 and 12 days for CCR2-/- and WT recipients, respectively (p < 0.0001). This was associated with reduction in the generation of CD8+, but not CD4+ effector alloreactive T cells (CD62L(low)CD44(high)) in CCR2-/- compared with WT recipients. In addition, CCR2-/- recipients had a reduced Th1 and increased Th2 alloresponse in the periphery (by ELISPOT analysis) as well as in the grafts (by RT-PCR). However, these changes were only transient in CCR2-/- recipients that ultimately rejected their grafts. Furthermore, in contrast to the islet transplants, CCR2 deficiency offered only marginal prolongation of heart allograft survival. This study demonstrates the important role for CCR2 in early islet allograft rejection and highlights the tissue specificity of the chemokine/chemokine receptor system in vivo in regulating allograft rejection.

Depletion of host Langerhans cells before transplantation of donor alloreactive T cells prevents skin graft-versus-host disease

Skin is the most commonly affected organ in graft-versus-host disease (GVHD). To explore the role of Langerhans cells in GVHD, the principal dendritic cells of the skin, we studied the fate of these cells in mice transplanted with allogeneic bone marrow. In contrast to other dendritic cells, host Langerhans cells were replaced by donor Langerhans cells only when donor T cells were administered along with bone marrow, and the extent of Langerhans cell chimerism correlated with the dose of donor T cells injected. Donor T cells depleted host Langerhans cells through a Fas-dependent pathway and induced the production in skin of CCL20, which was required for the recruitment of donor Langerhans cells. Administration of donor T cells to bone marrow-chimeric mice with persistent host Langerhans cells, but not to mice whose Langerhans cells had been replaced, resulted in marked skin GVHD. These findings indicate a crucial role for donor T cells in host Langerhans cell replacement, and show that host dendritic cells can persist in nonlymphoid tissue for the duration of an animal's life and can trigger GVHD despite complete blood chimerism.

Langerhans cells renew in the skin throughout life under steady-state conditions

Langerhans cells (LCs) are bone marrow (BM)-derived epidermal dendritic cells (DCs) that represent a critical immunologic barrier to the external environment, but little is known about their life cycle. Here, we show that in lethally irradiated mice that had received BM transplants, LCs of host origin remained for at least 18 months, whereas DCs in other organs were almost completely replaced by donor cells within 2 months. In parabiotic mice with separate organs, but a shared blood circulation, there was no mixing of LCs. However, in skin exposed to ultraviolet light, LCs rapidly disappeared and were replaced by circulating LC precursors within 2 weeks. The recruitment of new LCs was dependent on their expression of the CCR2 chemokine receptor and on the secretion of CCR2-binding chemokines by inflamed skin. These data indicate that under steady-state conditions, LCs are maintained locally, but inflammatory changes in the skin result in their replacement by blood-borne LC progenitors.

Domains specifying thrombin-receptor interaction

Platelet activation by the coagulation protease thrombin is central to arterial thrombosis, a major cause of morbidity and mortality. We recently isolated a complementary DNA encoding the platelet thrombin receptor. The extracellular amino-terminal extension of this seven transmembrane domain receptor contains the putative thrombin cleavage site LDPR/S which is critical for receptor activation. By replacing this cleavage site with the cleavage site for enterokinase, we have created a functional enterokinase receptor. This result demonstrates that all information necessary for receptor activation is provided by receptor proteolysis. Nanomolar enterokinase concentrations are required to activate this new receptor, in contrast to the picomolar thrombin concentrations that activate wild-type thrombin receptor. We identified a receptor domain critical for thrombin's remarkable potency at its receptor. This domain resembles the carboxyl tail of the leech anticoagulant hirudin and functions by binding to thrombin's anion-binding exosite. Our studies thus define a model for thrombin-receptor interaction. The utility of this model was demonstrated by the design of novel thrombin inhibitors based on receptor peptides.

The lumi-aggregometer: a new instrument for simultaneous measurement of secretion and aggregation by platelets

We have developed a new instrument that simultaneously monitors aggregation and secretion of ATP from the same sample of platelets. Aggregation is determined by the usual turbidimetric method; secretion of ATP is followed by measuring luminescence from the firefly luciferase system at right angles to the aggregometer light path. Data are recorded on a two-pen strip chart recorder and reveal the temporal relations between the two platelet responses.