GSK2793660 inhibited CTSC activity but not the activity of downstream neutrophil serine proteases. The palmar-plantar epidermal desquamation suggests a previously unidentified role for CTSC or one of its target proteins in the maintenance and integrity of the epidermis at these sites, with some similarities to the phenotype of CTSC-deficient humans.

BackgroundExcessive neutrophil presence and activation is important in a number of acute and chronic inflammatory diseases. The CXCR2 chemokine receptor is important in controlling the extravasation and activation of neutrophils. Selective antagonism of the CXCR2 receptor is a potential approach to reducing neutrophil migration and activation. Danirixin, is a small molecule, CXCR2 antagonist being evaluated as a potential anti-inflammatory medicine.Methods(1) First time in human (FTIH) double-blind, placebo-controlled study to evaluate the safety, pharmacokinetics, and pharmacodynamics of single ascending and repeat oral doses of danirixin in healthy male subjects; (2) single-dose study of age, gender, food, and proton-pump inhibitor effects on the pharmacokinetics of danirixin in healthy adult subjects; and placebo-controlled study of the pharmacokinetics of danirixin in healthy elderly subjects.ResultsThere were no serious adverse events and no adverse events considered to be of clinical relevance. There were no withdrawals due to adverse events. Systemic exposure following single doses of danirixin 10 mg, 25 mg, 50 mg, 100 mg, and 200 mg increased with increasing dose. Engagement of pharmacology was demonstrated as inhibition of ex-vivo CXCL1-induced CD11b expression on peripheral blood neutrophils when compared to placebo (approximately 50 % for 50 mg and 100 mg danirixin, and 72 % at 200 mg). There was a 37 % decrease in Cmax and a 16 % decrease in AUC (0-∞) following administration of danirixin in the presence of food. Cmax also decreased by 65 % when danirixin 100 mg was administered following omeprazole 40 mg once daily for 5 days. The AUC (0-∞) and Cmax were 50 % lower in elderly subjects compared with younger subjects.ConclusionThe dose-dependent inhibition of agonist-induced neutrophil activation following single and repeated once daily oral administration of danirixin suggests that this CXCR2 antagonist may have benefit in neutrophil-predominant inflammatory diseases. Co-administration with food, gastric acid reducing agents, and variable exposure in the elderly have important clinical implications that need to be taken into consideration in subsequent clinical evaluations.Trial registrationClinicalTrials.gov identifiers: NCT01209052 and NCT01209104

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CXC chemokine receptor 2 (CXCR2) is a key receptor in the chemotaxis of neutrophils to sites of inflammation. The studies reported here describe the pharmacological characterization of danirixin, a CXCR2 antagonist in the diaryl urea chemical class. Danirixin has high affinity for CXCR2, with a negative log of the 50% inhibitory concentration (pIC) of 7.9 for binding to Chinese hamster ovary cell (CHO)-expressed human CXCR2, and 78-fold selectivity over binding to CHO-expressed CXCR1. Danirixin is a competitive antagonist against CXCL8 in Ca-mobilization assays, with a K (the concentration of antagonist that binds 50% of the receptor population) of 6.5 nM and antagonist potency (pA) of 8.44, and is fully reversible in washout experiments over 180 minutes. In rat and human whole-blood studies assessing neutrophil activation by surface CD11b expression following CXCL2 (rat) or CXCL1 (human) challenge, danirixin blocks the CD11b upregulation with pICs of 6.05 and 6.3, respectively. Danirixin dosed orally also blocked the influx of neutrophils into the lung in vivo in rats following aerosol lipopolysaccharide or ozone challenge, with median effective doses (EDs) of 1.4 and 16 mg/kg respectively. Thus, danirixin would be expected to block chemotaxis in disease states in which neutrophils are increased in response to inflammation, such as pulmonary diseases. In comparison with navarixin, a CXCR2 antagonist from a different chemical class, the binding characterization of danirixin is distinct. These observations may offer insight into the previously observed clinical differences in induction of neutropenia between these compounds.

The role of T cells in chronic obstructive pulmonary disease (COPD) is not well understood. We have previously demonstrated that chronic cigarette smoke exposure can lead to the accumulation of CD4(+) and CD8(+) T cells in the alveolar airspaces in a mouse model of COPD, implicating these cells in disease pathogenesis. However, whether specific inhibition of T cell responses represents a therapeutic strategy has not been fully investigated. In this study inhibition of T cell responses through specific depleting antibodies, or the T cell immunosuppressant drug cyclosporin A, prevented airspace enlargement and neutrophil infiltration in a mouse model of chronic cigarette smoke exposure. Furthermore, individual inhibition of either CD4(+) T helper or CD8(+) T cytotoxic cells prevented airspace enlargement to a similar degree, implicating both T cell subsets as critical mediators of the adaptive immune response induced by cigarette smoke exposure. Importantly, T cell depletion resulted in significantly decreased levels of the Th17-associated cytokine IL-17A, and of caspase 3 and caspase 7 gene expression and activity, induced by cigarette smoke exposure. Finally, inhibition of T cell responses in a therapeutic manner also inhibited cigarette smoke-induced airspace enlargement, IL-17A expression, and neutrophil influx in mice. Together these data demonstrate for the first time that therapeutic inhibition of T cell responses may be efficacious in the treatment of COPD. Given that broad immunosuppression may be undesirable in COPD patients, this study provides proof-of-concept for more targeted approaches to inhibiting the role of T cells in emphysema development.