Kinetic approach to pathway attenuation using XOMA 052, a regulatory therapeutic antibody that modulates interleukin-1beta activity.

Many therapeutic antibodies act as antagonists to competitively block cellular signaling pathways. We describe here an approach for the therapeutic use of monoclonal antibodies based on context-dependent attenuation to reduce pathologically high activity while allowing homeostatic signaling in biologically important pathways. Such attenuation is achieved by modulating the kinetics of a ligand binding to its various receptors and regulatory proteins rather than by complete blockade of signaling pathways. The anti-interleukin-1beta (IL-1beta) antibody XOMA 052 is a potent inhibitor of IL-1beta activity that reduces the affinity of IL-1beta for its signaling receptor and co-receptor but not for its decoy and soluble inhibitory receptors. This mechanism shifts the effective dose response of the cytokine so that the potency of IL-1beta bound by XOMA 052 is 20-100-fold lower than that of IL-1beta in the absence of antibody in a variety of in vitro cell-based assays. We propose that by decreasing potency of IL-1beta while allowing binding to its clearance and inhibitory receptors, XOMA 052 treatment will attenuate IL-1beta activity in concert with endogenous regulatory mechanisms. Furthermore, the ability to bind the decoy receptor may reduce the potential for accumulation of antibody.target complexes. Regulatory antibodies like XOMA 052, which selectively modulate signaling pathways, may represent a new mechanistic class of therapeutic antibodies.

Localization of human TACC3 to mitotic spindles is mediated by phosphorylation on Ser558 by Aurora A: a novel pharmacodynamic method for measuring Aurora A activity.

Aurora A is a serine/threonine protein kinase essential for normal mitotic progression. Aberrant increased expression of Aurora A, which occurs frequently in human cancers, results in abnormal mitoses leading to chromosome instability and possibly tumorigenesis. Consequently, Aurora A has received considerable attention as a potential target for anticancer therapeutic intervention. Aurora A coordinates several essential mitotic activities through phosphorylation of a variety of proteins, including TACC3, which modulates microtubule stabilization of the mitotic spindle. Recent studies identified a conserved serine in Xenopus (Ser(626)) and Drosophila (Ser(863)) TACC3 orthologues that is phosphorylated by Aurora A. We show that this conserved serine on human TACC3 (Ser(558)) is also phosphorylated by Aurora A. Moreover, phosphorylation of TACC3 by Aurora A in human cells is essential for its proper localization to centrosomes and proximal mitotic spindles. Inhibition of Aurora A with the selective small molecule inhibitor MLN8054 in cultured human tumor cells resulted in mislocalization of TACC3 away from mitotic spindles in a concentration-dependent manner. Furthermore, oral administration of MLN8054 to nude mice bearing HCT-116 human tumor xenografts caused a dose-dependent mislocalization of TACC3 away from spindle poles that correlated with tumor growth inhibition. As TACC3 localization to mitotic spindles depends on Aurora A-mediated phosphorylation, quantifying TACC3 mislocalization represents a novel pharmacodynamic approach for measuring Aurora A activity in cancer patients treated with inhibitors of Aurora A kinase.

Human melastatin 1 (TRPM1) is regulated by MITF and produces multiple polypeptide isoforms in melanocytes and melanoma.

Melastatin 1 (MLSN1), originally identified as melanoma metastasis suppressor, represents a TRPM subfamily of transient receptor potential (TRP) proteins which serve diverse biological roles in a wide variety of cell types. Down-regulation of MLSN1 expression in human cutaneous melanoma, as indicated by in situ hybridization, appears to be a prognostic marker for melanoma metastasis. However, the exact physiological function(s) of MLSN1, the mechanism(s) involved in the regulation of its expression and its role in melanoma tumour progression are not yet clear. In this study, we identified a 654 bp upstream sequence of MLSN1, containing four E boxes (E1-E4), including an 11 bp M box (E4), that is sufficient for melanocyte-specific transcription and activation by the melanocyte transcription factor MITF (a bHLH-zip factor). Deletion analysis showed that the two distal E boxes (E3 and E4) in the MLSN1 promoter are required for both its activation by MITF and its constitutive activity in melanoma cells. Western blot analysis using polyclonal rabbit anti-human MLSN1 antibodies identified several polypeptides, presumably generated by both alternative splicing of MLSN1 messenger RNA (mRNA) and proteolytic cleavage, in both melanocytes and metastatic melanoma cells. Thus, multiple mechanisms appear to regulate MLSN1 expression in melanocytes and melanoma cells.

Monoclonal antibodies targeting IL-1 beta reduce biomarkers of atherosclerosis in vitro and inhibit atherosclerotic plaque formation in Apolipoprotein E-deficient mice.

OBJECTIVE: Atherosclerosis is a condition that is increasingly contributing to worldwide mortality through complications such as stroke and myocardial infarction. IL-1ß plays multiple direct, local roles in the formation and stability of the atheroma by eliciting the production of additional cytokines and proteolytic enzymes from macrophages, endothelial cells (EC) and smooth muscle cells (SMC). We therefore tested whether an anti-IL-1ß antibody, XOMA 052, might inhibit the secretion of pro-atherogenic cytokines from macrophages in vitro and affect a positive outcome in the Apolipoprotein E-deficient mouse (ApoE(-/-)) model of atherosclerosis in vivo. METHODS AND RESULTS: In an in vitro co-culture model, XOMA 052 inhibited macrophage-induced secretion of key atherogenic cytokines from EC and SMC, including IL-6, IL-8, MCP-1 and TNFα. The release of degradative enzymes, such as the matrix metalloproteinases MMP-3 and MMP-9, was also decreased by XOMA 052. In addition, XOMA 052 inhibited the secretion of IL-7 from EC and IL-4 from SMC, cytokines not previously reported to be driven by IL-1ß in this context. In vivo, XMA052 MG1K, a chimeric murine version of XOMA 052, inhibited the formation of atherosclerotic lesions in the ApoE(-/-) model at all three doses tested. This effect was comparable to that reported for complete genetic ablation of IL-1ß or IL-1R1 on an ApoE(-/-) background and was associated with decreases in plasma non-HDL/HDL cholesterol ratio and plaque lipid content and macrophage infiltration. CONCLUSIONS: These results demonstrate for the first time that an antibody targeting IL-1ß can inhibit the progression of atherosclerosis in vivo, highlighting the importance of this key cytokine in cardiovascular disease.