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Background and Aims: Progressive multifocal leukoencephalopathy [PML], a brain infection associated with anti-integrin drugs that inhibit lymphocyte translocation from bloodstream to tissue, can be fatal. Decreased central nervous system [CNS] immune surveillance leading to this infection has been reported in patients with multiple sclerosis or Crohn's disease treated with antiintegrin antibody natalizumab. PF-00547659 is an investigational human monoclonal antibody for inflammatory bowel disease, targeted against α4β7-mucosal addressin cell-adhesion molecule-1 [the integrin ligand selectively expressed in the gut]. We hypothesised that this selective agent would not affect central nervous system immune surveillance. Methods: Cerebrospinal fluid from five healthy volunteers, and from 10 patients with Crohn's disease previously treated with immunosuppressants, was evaluated to assess the feasibility of the study. Subsequently, 39 patients with active Crohn's disease and previous immunosuppression were evaluated over 12 weeks of PF-00547659-induction therapy. We measured total lymphocytes, T cell subsets in cerebrospinal fluid, and circulating β7+ memory cells. Disease activity was assessed using the Harvey-Bradshaw Index. Results: Patients treated with PF-00547659 had no reduction of cerebrospinal fluid lymphocytes, T-lymphocyte subsets, or CD4:CD8 ratio, whereas circulating β7+ memory cells increased significantly. A total of 28/35 [80%] patients had a clinical response and 27/34 [79%] had disease remission. Treatment-related adverse events, none serious, were reported in 23/49 [47%] patients. Conclusions: In patients with active Crohn's disease, natalizumab therapy increases the risk for PML, and the increased risk is thought to be associated with iatrogenic leukopenia within the CNS. PML under PF-00547659 may be a lesser concern, as this agent did not reduce lymphocytes or T cell subsets in the cerebrospinal fluid., SCOPUS: ar.j, info:eu-repo/semantics/published

Nicotinamide (2) is a potent and selective inhibitor of the PDE4D isozyme and as a chemical tool selectively blocks eosinophil mediator release and chemotaxis thus linking the role of PDE4D to eosinophil function.

The ability of various C-C chemokines to elicit tissue eosinophil infiltration following intradermal injection or peripheral blood eosinophilia following intravenous injection were compared in the Brown-Norway rat. Eotaxin (0.1–3 μg site−1) of human and murine origin produced equivalent, dose-dependent increases in eosinophil peroxidase activity in rat dermis 4 h post-injection. Human eotaxin-2 was equipotent with human eotaxin in terms of dermal eosinophil recruitment. Other human CCR3 agonists, such as MCP-3, RANTES and MCP-4 failed to increase dermal eosinophil peroxidase activity at doses up to 1 μg site−1 whereas the latter did produce a small effect at 3 μg site−1. Consistent with observations in vivo, human eotaxin displaced [125I]-eotaxin from rat spleen membranes more potently (IC50=2 nM) than did MCP-4 (IC50=500 nM). RANTES did not compete with the radiolabelled chemokine at concentrations up to 1 μM. Human eotaxin (5 μg) administered intravenously increased circulating eosinophils ∼3 fold whereas MCP-4 (5 μg, i.v.) increased circulating monocytes ∼3 fold without affecting eosinophil numbers. Dexamethasone pretreatment inhibited eotaxin-induced dermal eosinophil influx only at a steroid dose (0.1 mg kg−1, s.c.) which significantly reduced circulating eosinophil numbers. The steroid also reduced eosinophilia in peripheral blood resulting from systemic eotaxin administration (5 μg, i.v.). These data suggest differences in rat CCR3 relative to other species as surmised from a distinctive rank order of chemokine potency. In addition to its chemotactic effects eotaxin, but not MCP-4, promotes eosinophil recruitment into the circulation. One of the mechanisms by which glucocorticoids, such as dexamethasone, acutely inhibits eotaxin-induced dermal eosinophil influx is to diminish the circulating numbers of these cells available for tissue recruitment. British Journal of Pharmacology (1999) 128, 788–794; doi:10.1038/sj.bjp.0702835

Increased cyclic AMP-phosphodiesterase activity in peripheral blood leukocytes is associated with the immune and inflammatory hyperreactivity that characterizes atopic dermatitis. Atopic phosphodiesterase has high sensitivity to a variety of enzyme inhibitors, suggesting an increased therapeutic advantage. The objective of this study was to use in vitro assays to identify a potent phosphodiesterase inhibitor and then to investigate its effectiveness in treating atopic dermatitis. Leukocyte enzyme activity was measured by radioenzyme assay, whereas prostaglandin E 2 and interleukins 10 (IL-10) and 4 (IL-4) were measured in 24-h culture supernatants of mononuclear leukocytes by immunoassays. The effect of a topical phosphodiesterase Inhibitor on atopic dermatitis lesional skin was assessed by double-blind, paired comparisons of active drug and placebo ointments applied to symmetrically involved sites over a 28-d period. Using in vitro assays, we demonstrated the ability of selective high-potency phosphodiesterase inhibitors to reduce prostaglandin E 2 , IL-10, and IL-4 production in atopic mononuclear leukocyte cultures. We selected the Type 4 phosphodiesterase inhibitor, CP80,633, based on its inhibitory potency, for clinical testing by topical, bilateral paired comparisons in 20 patients with atopic dermatitis and demonstrated significant reductions of all inflammatory parameters. Phosphodiesterase inhibitors modulate several pathways contributing to the exaggerated immune and inflammatory responses, which characterize atopic dermatitis. This in vivo demonstration of anti-inflammatory efficacy may provide a useful alternative to the over-reliance on corticosteroid therapy in atopic disease.

Guinea pigs were sensitized by daily intraperitoneal injections of 100 mg of egg albumin for 3 consecutive days and sacrificed at 30–35 days after the last injection. The in vitro sensitivity and response of the sensitized tracheal muscle to methacholine and histamine were significantly less than those of littermate controls. However, there was no difference between the dissociation constants and concentrations of pulmonary muscarinic receptor binding sites of the control and sensitized guinea pigs. We conclude that subsensitivity and hyporesponsiveness to methacholine and histamine occur in the airway muscle of this guinea pig model of experimental asthma and suggest that the decreased reactivity to methacholine might be due to defects beyond the receptor.

The relaxation of thoracic and abdominal aortae of the spontaneously hypertensive rat (SHR) during prehypertensive (3--5 week old) and hypertensive (12--16 and 22--25 week old) stages was compared to that of matched normotensive Wistar rats (NWRs). In the thoracic aorta, the relaxation response to isoproterenol, acetylcholine, Mg2+, Mn2+, Co2+, and La3+ was less in both prehypertensive and hypertensive SHRs than in the matched NWRs; however, such difference was not evident in the abdominal aorta. Similarly, the relaxing effect of nitroglycerin and papaverine was not different in the aorta preparations of the SHR and NWR. After chronic reserpine treatment of the prehypertensive and hypertensive SHRs, the thoracic aorta still showed less relaxation in response to the aforementioned agents. Isoproterenol, but not other agents tested, produced less relaxation in the thoracic aorta from the renal hypertensive rat than from the control. Our results suggest that the decreased relaxation of the SHR thoracic aorta is not a consequence of hypertension and that the defect in the SHR thoracic aorta cannot be generalized to other vascular beds.

Serotonin (5-HT), histamine, norepinephrine, methoxamine and isoproterenol caused dose-dependent contraction of human cerebral arteries. The potency of 5-HT was greater among test agents in the basilar arteries, whereas it was equivalent to that of norepinephrine in human anterior, middle and posterior cerebral arteries. Acetylcholine and carbachol (10–9–10–5 M) caused a negligible response in human cerebral arteries. Contractile response to 5-HT was greater in the distal rather than middle portion of the human basilar arteries while this order was reversed in the response to norepinephrine. Tyramine (10–4 M) caused tonic contraction and nicotine (10–4 M) and electrical transmural stimulation produced phasic contraction of arteries which were antagonized by adrenergic blocking agents. Adenine nucleotides failed to cause relaxation and only high concentration of adenosine caused a minute relaxation. However, papaverine and nitroglycerin caused marked relaxation. These results suggest that adrenergic mechanism may play a role in the regulation of vascular tone in human cerebral arteries.

Background IL-21 has been shown to play an important role in autoimmune diseases. ATR-107 is an antibody which directly targets the IL-21 receptor (IL-21R). To aid the clinical development of ATR-107, there is a need for understanding the mechanism of action (MOA) of this antibody when assessing target engagement in human subjects. Methods To determine ATR-107 biological activity and potency in human blood, its inhibitory function against IL-21 induced STAT3 phosphorylation in human peripheral T and B cells was measured. Results The data show that IL-21 induces STAT3 phosphorylation in a concentration-dependent manner, consistent with its migration to the nuclear. Using a flow cytometry based functional whole blood assay, ATR-107 is demonstrated to be a potent IL-21 pathway inhibitor. It competes with IL-21 for receptor binding in a competitive manner, but once it binds to the receptor it behaves like a non-competitive inhibitor, most probably due to the long observed koff. The concentration-dependent inhibition observed with ATR-107 correlates inversely with the levels of receptor occupancy, both in ex vivo whole blood assays and directly in human blood when ATR-107 was given to healthy volunteers. Conclusions IL-21 induced phosphorylation of STAT3 in T and B cells can be used as a biomarker to evaluate the target engagement of ATR-107 in human whole blood. The antibody behaves like a potent non-competitive inhibitor blocking IL-21 induced STAT3 phosphorylation for a long period of time. These results may help with the translation of preclinical information and dose selection towards ATR-107 clinical efficacy.