An engineered immunomodulatory IgG1 Fc suppresses autoimmune inflammation through pathways shared with i.v. immunoglobulin.

Immunoglobulin G (IgG) antibodies in the form of high-dose intravenous immunoglobulin (IVIG) exert immunomodulatory activity and are used in this capacity to treat inflammatory and autoimmune diseases. Reductionist approaches have revealed that terminal sialylation of the single asparagine-linked (N-linked) glycan at position 297 of the IgG1 Fc bestows antiinflammatory activity, which can be recapitulated by introduction of an F241A point mutation in the IgG1 Fc (FcF241A). Here, we examined the antiinflammatory activity of CHO-K1 cell-produced FcF241A in vivo in models of autoimmune inflammation and found it to be independent of sialylation. Intriguingly, sialylation markedly improved the half-life and bioavailability of FcF241A via impaired interaction with the asialoglycoprotein receptor ASGPR. Further, FcF241A suppressed inflammation through the same molecular pathways as IVIG and sialylated IgG1 Fc and required the C-type lectin SIGN-R1 in vivo. This contrasted with FcAbdeg (efgartigimod), an engineered IgG1 Fc with enhanced neonatal Fc receptor (FcRn) binding, which reduced total serum IgG concentrations, independent of SIGN-R1. When coadministered, FcF241A and FcAbdeg exhibited combinatorial antiinflammatory activity. Together, these results demonstrated that the antiinflammatory activity of FcF241A requires SIGN-R1, similarly to that of high-dose IVIG and sialylated IgG1, and can be used in combination with other antiinflammatory therapeutics that rely on divergent pathways, including FcAbdeg.

Engagement of CD81 induces ezrin tyrosine phosphorylation and its cellular redistribution with filamentous actin.

CD81 is a tetraspanin family member involved in diverse cellular interactions in the immune and nervous systems and in cell fusion events. However, the mechanism of action of CD81 and of other tetraspanins has not been defined. We reasoned that identifying signaling molecules downstream of CD81 would provide mechanistic clues. We engaged CD81 on the surface of B-lymphocytes and identified the induced tyrosine-phosphorylated proteins by mass spectrometry. This analysis showed that the most prominent tyrosine phosphorylated protein was ezrin, an actin-binding protein and a member of the ezrin-radixin-moesin family. We also found that CD81 engagement induces spleen tyrosine kinase (Syk) and that Syk was involved in tyrosine phosphorylation of ezrin. After engagement of CD81, it colocalized with ezrin and F-actin, and this association was disrupted when Syk activation was blocked. Taken together, these studies suggest a model in which CD81 interfaces between the plasma membrane and the cytoskeleton by activating Syk, mobilizing ezrin, and recruiting F-actin to facilitate cytoskeletal reorganization and cell signaling. This mechanism might explain the pleiotropic effects induced in response to stimulation of cells by anti-CD81 antibodies or by the hepatitis C virus, which uses this molecule as its key receptor.

Cutting edge: The transmembrane E3 ligase GRAIL ubiquitinates the costimulatory molecule CD40 ligand during the induction of T cell anergy.

Activation of naive T lymphocytes is regulated through a series of discrete checkpoints that maintain unresponsiveness to self. During this multistep process, costimulatory interactions act as inducible signals that allow APCs to selectively mobilize T cells against foreign Ags. In this study, we provide evidence that the anergy-associated E3 ubiquitin ligase GRAIL (gene related to anergy in lymphocytes) regulates expression of the costimulatory molecule CD40L on CD4 T cells. Using its luminal protease-associated domain, GRAIL binds to the luminal/extracellular portion of CD40L and facilitates transfer of ubiquitin molecules from the intracellular GRAIL RING (really interesting new gene) finger to the small cytosolic portion of CD40L. Down-regulation of CD40L occurred following ectopic expression of GRAIL in naive T cells from CD40(-/-) mice, and expression of GRAIL in bone marrow chimeric mice was associated with diminished lymphoid follicle formation. These data provide a model for intrinsic T cell regulation of costimulatory molecules and a molecular framework for the initiation of clonal T cell anergy.

Cerdulatinib Pharmacodynamics and Relationships to Tumor Response Following Oral Dosing in Patients with Relapsed/Refractory B-cell Malignancies.

PURPOSE: Preclinical studies suggest SYK and JAK contribute to tumor-intrinsic and microenvironment-derived survival signals. The pharmacodynamics of cerdulatinib, a dual SYK/JAK inhibitor, and associations with tumor response were investigated. PATIENTS AND METHODS: In a phase I dose-escalation study in adults with relapsed/refractory B-cell malignancies, cerdulatinib was administered orally to sequential dose-escalation cohorts using once-daily or twice-daily schedules. The study enrolled 8 patients with chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL), 13 with follicular lymphoma, 16 with diffuse large B-cell lymphoma (DLBCL), and 6 with mantle cell lymphoma. Correlation of tumor response with pharmacodynamic markers was determined in patients with meaningful clinical responses. RESULTS: Following cerdulatinib administration, complete SYK and JAK pathway inhibition was achieved in whole blood of patients at tolerated exposures. Target inhibition correlated with serum cerdulatinib concentration, and IC50 values against B-cell antigen receptor (BCR), IL2, IL4, and IL6 signaling pathways were 0.27 to 1.11 µmol/L, depending on the phosphorylation event. Significant correlations were observed between SYK and JAK pathway inhibition and tumor response. Serum inflammation markers were reduced by cerdulatinib, and several significantly correlated with tumor response. Diminished expression of CD69 and CD86 (B-cell activation markers), CD5 (negative regulator of BCR signaling), and enhanced expression of CXCR4 were observed in 2 patients with CLL, consistent with BCR and IL4 suppression and loss of proliferative capacity. CONCLUSIONS: Cerdulatinib potently and selectively inhibited SYK/JAK signaling at tolerated exposures in patients with relapsed/refractory B-cell malignancies. The extent of target inhibition in whole-blood assays and suppression of inflammation correlated with tumor response. (ClinicalTrials.gov ID:NCT01994382).

The Dual Syk/JAK Inhibitor Cerdulatinib Antagonizes B-cell Receptor and Microenvironmental Signaling in Chronic Lymphocytic Leukemia.

Purpose: B-cell receptor (BCR)-associated kinase inhibitors, such as ibrutinib, have revolutionized the treatment of chronic lymphocytic leukemia (CLL). However, these agents are not curative, and resistance is already emerging in a proportion of patients. IL4, expressed in CLL lymph nodes, can augment BCR signaling and reduce the effectiveness of BCR kinase inhibitors. Therefore, simultaneous targeting of the IL4- and BCR signaling pathways by cerdulatinib, a novel dual Syk/JAK inhibitor currently in clinical trials (NCT01994382), may improve treatment responses in patients.Experimental Design: PBMCs from patients with CLL were treated in vitro with cerdulatinib alone or in combination with venetoclax. Cell death, chemokine, and cell signaling assay were performed and analyzed by flow cytometry, immunoblotting, q-PCR, and ELISA as indicated.Results: At concentrations achievable in patients, cerdulatinib inhibited BCR- and IL4-induced downstream signaling in CLL cells using multiple readouts and prevented anti-IgM- and nurse-like cell (NLC)-mediated CCL3/CCL4 production. Cerdulatinib induced apoptosis of CLL cells, in a time- and concentration-dependent manner, and particularly in IGHV-unmutated samples with greater BCR signaling capacity and response to IL4, or samples expressing higher levels of sIgM, CD49d+, or ZAP70+ Cerdulatinib overcame anti-IgM, IL4/CD40L, or NLC-mediated protection by preventing upregulation of MCL-1 and BCL-XL; however, BCL-2 expression was unaffected. Furthermore, in samples treated with IL4/CD40L, cerdulatinib synergized with venetoclax in vitro to induce greater apoptosis than either drug alone.Conclusions: Cerdulatinib is a promising therapeutic for the treatment of CLL either alone or in combination with venetoclax, with the potential to target critical survival pathways in this currently incurable disease. Clin Cancer Res; 23(9); 2313-24. ©2016 AACR.

Increases in dopamine D3 receptor binding in rats receiving a cocaine challenge at various time points after cocaine self-administration: implications for cocaine-seeking behavior.

Previous research suggests that cocaine dysregulates dopamine D3 receptors. The present study examined the time course of changes in dopamine D3 receptor binding after terminating a cocaine self-administration regimen. [125I]-7-hydroxy-2-[N-propyl-N-(3'-iodo-2'-propenyl)-amino]-tetralin was used to label dopamine D3 receptors in rats that had undergone testing for cocaine-seeking behavior reinstated by a cocaine priming injection (15 mg/kg, i.p.; the behavior results have been previously published), and were killed 24 h after the test at time points that were either 2, 8, or 31-32 days after their last cocaine self-administration session. The results indicated a time-dependent increase in D3 receptor binding relative to controls that received saline yoked to the delivery of cocaine in an experimental animal. Specifically, there was no significant change in D3 receptor binding in cocaine-experienced rats killed at the 2- or 8-day time points relative to controls, but there was an increase in D3 receptor binding in the nucleus accumbens core and ventral caudate-putamen in rats killed at the 31- to 32-day time point. In a subsequent experiment, we replicated the increase in D3 receptor binding in rats that underwent a less extensive self-administration regimen, then were tested for cocaine-primed reinstatement of cocaine-seeking behavior, and then were killed 24 h later at a time point of 22 days after their last self-administration session. Furthermore, the increase in binding was attenuated by repeated 7-hydroxy-N,N-di-n-propyl-2-aminotetralin administration (1 mg/kg/day, s.c. for 14 days), a regimen that also reduces cocaine-seeking behavior in animals when tested in a nondrug state. Collectively, the findings suggest that regulatory responses of D3 receptors may be functionally related to changes in propensity for cocaine-seeking behavior.

Tissue distribution and receptor-mediated clearance of anti-CD11a antibody in mice.

Efalizumab (Raptiva) is a humanized monoclonal antibody specific for CD11a, the alpha-chain component of the lymphocyte function-associated antigen 1. In humans, the rate of efalizumab elimination from serum was related to the level of CD11a cell surface expression. These data suggested a role for the CD11a receptor, itself, in efalizumab clearance. Recently, we conducted a series of in vitro studies that suggested a role for CD11a-expressing T cells in efalizumab clearance as mediated by cellular internalization and lysosome-mediated degradation (Coffey et al., 2004). To further study the mechanism of anti-CD11a clearance in vivo, we assessed the tissue distribution, cellular internalization, and subcellular localization of a rat anti-mouse CD11a monoclonal antibody in various tissues in mice. Anti-CD11a antibody primarily distributed to leukocytes and macrophages in the peripheral blood, spleen, and liver, with uptake in the lymph nodes and bone marrow after 72 h. At least a portion of the antibody was internalized and cleared by peripheral blood mononuclear cells, lymphocytes, and splenocytes in a time-dependent manner in vivo. Internalized antibody costained with LysoTracker Red, suggesting that it was transported to lysosomes for degradation. Together, these data suggest that one clearance mechanism for anti-CD11a antibody in vivo is via receptor-mediated internalization and lysosomal degradation by CD11a-expressing cells and tissues.