Michael Yeadon

Inhalation by Design: Novel Ultra-Long-Acting β2-Adrenoreceptor Agonists for Inhaled Once-Daily Treatment of Asthma and Chronic Obstructive Pulmonary Disease That Utilize a Sulfonamide Agonist Headgroup

A novel series of potent and selective sulfonamide derived β(2)-adrenoreceptor agonists are described that exhibit potential as inhaled ultra-long-acting bronchodilators for the treatment of asthma and chronic obstructive pulmonary disease. Analogues from this series mediate very long-lasting smooth muscle relaxation in guinea pig tracheal strips. The sulfonamide agonist headgroup confers high levels of intrinsic crystallinity that could relate to the acidic sulfonamide motif supporting a zwitterionic form in the solid state. Optimization of pharmacokinetic properties was achieved through targeted introduction of a phenolic moiety to support rapid phase II clearance, thereby minimizing systemic exposure following inhalation and reducing systemically mediated adverse events. Compound 38 (PF-610355) is identified as a clinical candidate from this series, with in vivo duration of action studies confirming its potential for once-daily use in humans. Compound 38 is currently in advanced phase II clinical studies.

Uptake, Efficacy, and Systemic Distribution of Naked, Inhaled Short Interfering RNA (siRNA) and Locked Nucleic Acid (LNA) Antisense

Antisense oligonucleotides (ASOs) and small interfering RNA (siRNA) promise specific correction of disease-causing gene expression. Therapeutic implementation, however, has been forestalled by poor delivery to the appropriate tissue, cell type, and subcellular compartment. Topical administration is considered to circumvent these issues. The availability of inhalation devices and unmet medical need in lung disease has focused efforts in this tissue. We report the development of a novel cell sorting method for quantitative, cell type-specific analysis of siRNA, and locked nucleic acid (LNA) ASO uptake and efficacy after intratracheal (i.t.) administration in mice. Through fluorescent dye labeling, we compare the utility of this approach to whole animal and whole tissue analysis, and examine the extent of tissue distribution. We detail rapid systemic access and renal clearance for both therapeutic classes and lack of efficacy at the protein level in lung macrophages, epithelia, or other cell types. We nevertheless observe efficient redirection of i.t. administered phosphorothioate (PS) LNA ASO to the liver and kidney leading to targeted gene knockdown. These data suggest delivery remains a key obstacle to topically administered, naked oligonucleotide efficacy in the lung and introduce inhalation as a potentially viable alternative to injection for antisense administration to the liver and kidneys.

Effect of a 5-lipoxygenase inhibitor and leukotriene antagonist (PF 5901) on antigen-induced airway responses in neonatally immunized rabbits

1 The effect of a single intratracheal dose (10 mg) of PF 5901 (2‐[3(1‐hydroxyhexyl) phenoxymethyl] quinoline hydrochloride, a specific inhibitor of the 5‐lipoxygenase pathway of arachidonic acid metabolism and a leukotriene D4 antagonist) on airway changes induced in response to Alternaria tenuis aerosol challenge was assessed in adult rabbits neonatally immunized. Leukotriene generation was determined in vivo by measuring leukotriene B4 (LTB4) levels in bronchoalveolar lavage (BAL) fluid and ex vivo by measuring calcium ionophore‐stimulated production of LTB4 in whole blood. 2 While PF 5901 (10 mg) had no significant effect on the acute bronchoconstriction induced by antigen, this dose was sufficient to inhibit significantly the increase in airway responsiveness to inhaled histamine 24 h following antigen challenge (P < 0.05). 3 Total leucocyte infiltration into the airways induced by antigen, as assessed by bronchoalveolar lavage, was significantly inhibited by pretreatment with PF 5901 (10 mg). However, the pulmonary infiltration of neutrophils and eosinophils induced by antigen was unaltered by prior treatment with PF 5901 (10 mg). 4 PF 5901 (10 mg) had no effect on ex vivo LTB4 synthesis in whole blood. However, the antigen‐induced increase in LTB4 levels in BAL 24 h following challenge was significantly inhibited (P < 0.05). 5 We suggest from the results of the present study that the antigen‐induced airway hyperresponsiveness to inhaled histamine in immunized rabbits is mediated, at least in part, by products of the 5‐lipoxygenase metabolic pathway, and is not dependent on the extent of eosinophil or neutrophil influx into the airway lumen.

Anti-inflammatory modulation of chronic airway inflammation in the murine house dust mite model.

Asthma affects 300 million people worldwide and continues to be a major cause of morbidity and mortality. Disease relevant animal models of asthma are required for benchmarking of novel therapeutic mechanisms in comparison to established clinical approaches. We demonstrate that chronic exposure of mice to house dust mite (HDM) extract results in allergic airway inflammation, that can be significantly attenuated by therapeutic intervention with phosphodiesterase 4 inhibition and corticosteroid treatment. Female BALB/c mice were administered intranasally with HDM (Dermatophagoides pteronyssinus) extract daily for five weeks, and therapeutic intervention with anti-inflammatory treatment (dexamethasone 1 mg/kg subcutaneous once daily, prednisolone 10mg/kg orally twice daily, fluticasone 3, 10 and 30 microg intranasally twice daily, roflumilast 10 mg/kg orally twice daily and intranasally 10 and 30 microg twice daily) was initiated after three weeks of exposure. Chronic HDM extract exposure resulted in significant airway inflammation, demonstrated by bronchoalveolar lavage cell infiltration and lung tissue inflammatory gene expression by TaqMan low density array. Chronic steroid treatment significantly inhibited these parameters. In addition, roflumilast caused a significant reduction in airway inflammatory cell infiltration. We have demonstrated that chronic HDM-induced allergic inflammation can be significantly ameliorated by steroid treatment, and that phosphodiesterase 4 inhibition modulates inflammatory cell infiltration. Therefore, the murine HDM model may be a useful tool for evaluating new targets for the treatment of asthma.

Preclinical evaluation of an inhibitor of cytosolic phospholipase A2α for the treatment of asthma

Asthma is a chronic inflammatory lung disease with considerable unmet medical needs for new and effective therapies. Cytosolic phospholipase A2α (cPLA2α) is the rate-limiting enzyme that is ultimately responsible for the production of eicosanoids implicated in the pathogenesis of asthma. We investigated a novel cPLA2α inhibitor, PF-5212372, to establish the potential of this drug as a treatment for asthma. PF-5212372 was a potent inhibitor of cPLA2α (7 nM) and was able to inhibit prostaglandin (PG)D2 and cysteinyl leukotriene release from anti-IgE-stimulated human lung mast cells (0.29 and 0.45 nM, respectively). In a mixed human lung cell population, PF-5212372 was able to inhibit ionomycin-stimulated release of leukotriene B4, thromboxane A2, and PGD2 (2.6, 2.6, and 4.0 nM, respectively) but was significantly less effective against PGE2 release (>301 nM; p < 0.05). In an in vitro cell retention assay, PF-5212372 retained its potency up to 24 h after being washed off. In a sheep model of allergic inflammation, inhalation of PF-5212372 significantly inhibited late-phase bronchoconstriction (78% inhibition; p < 0.001) and airway hyper-responsiveness (94% inhibition; p < 0.001), and isolated sheep lung mast cell assays confirmed species translation via effective inhibition of PGD2 release (0.78 nM). Finally, PF-5212372 was assessed for its ability to inhibit the contraction of human bronchi induced by AMP. PF5212372 significantly inhibited AMP-induced contraction of human bronchi (81% inhibition; p < 0.001); this finding, together with the ability of this drug to be effective in a wide range of preclinical asthma models, suggests that inhibition of cPLA2α with PF-5212372 may represent a new therapeutic option for the treatment of asthma.

SAR of a series of inhaled A(2A) agonists and comparison of inhaled pharmacokinetics in a preclinical model with clinical pharmacokinetic data.

COPD is a major cause of mortality in the western world. A(2A) agonists are postulated to reduce the lung inflammation that causes COPD. The cardiovascular effects of A(2A) agonists dictate that a compound needs to be delivered by inhalation to be therapeutically useful. The pharmacological and pharmacokinetic SAR of a series of inhaled A(2A) agonists is described leading through to human pharmacokinetic data for a clinical candidate.

Inhalation by Design: Novel Tertiary Amine Muscarinic M3 Receptor Antagonists with Slow Off-Rate Binding Kinetics for Inhaled Once-Daily Treatment of Chronic Obstructive Pulmonary Disease

A novel tertiary amine series of potent muscarinic M(3) receptor antagonists are described that exhibit potential as inhaled long-acting bronchodilators for the treatment of chronic obstructive pulmonary disease. Geminal dimethyl functionality present in this series of compounds confers very long dissociative half-life (slow off-rate) from the M(3) receptor that mediates very long-lasting smooth muscle relaxation in guinea pig tracheal strips. Optimization of pharmacokinetic properties was achieved by combining rapid oxidative clearance with targeted introduction of a phenolic moiety to secure rapid glucuronidation. Together, these attributes minimize systemic exposure following inhalation, mitigate potential drug-drug interactions, and reduce systemically mediated adverse events. Compound 47 (PF-3635659) is identified as a Phase II clinical candidate from this series with in vivo duration of action studies confirming its potential for once-daily use in humans.

Inhaled adenosine A2A receptor agonists for the treatment of chronic obstructive pulmonary disease

COPD is a major cause of mortality in the western world. A(2A) agonists are postulated to reduce the lung inflammation that causes COPD. The cardiovascular effects of A(2A) agonists dictate that a compound needs to be delivered by inhalation to be therapeutically useful. A strategy of minimizing side-effect liability by maximizing systemic clearance was followed and pharmacological and pharmacokinetic SAR of a series of inhaled A(2A) agonists described. A sevenfold improvement in potency and 150-fold reduction in side-effect liability over the lead compound CGS-21680, were obtained.

Inhaled muscarinic antagonists for COPD—does an anti-inflammatory mechanism really play a role?

The long acting inhaled muscarinic antagonist tiotropium (Spiriva) improves lung function in patients with COPD. In addition, tiotropium reduces exacerbation frequency, dyspnoea and improves exercise capacity. As the latter has been associated with airway inflammation then this suggests that, in addition to the well-known anti-bronchoconstrictor effect, tiotropium might also display anti-inflammatory properties. With our current state of knowledge, however, it is not necessary to postulate an anti-inflammatory effect for tiotropium (Spiriva), rather inhibition of smooth muscle constriction with subsequent effects on lung hyperinflation (and possibly pulmonary circulation) can explain the effects on exacerbation frequency, dyspnoea and exercise capacity. Recent reports suggest that tiotropium can inhibit viral activation of inflammation and vagal nerve stimulation, suggesting a mechanism by which tiotropium can inhibit viral induction of exacerbations in COPD.

Design and synthesis of achiral 5-lipoxygenase inhibitors employing the cyclobutyl group

Abstract The achiral cyclobutyl group is an effective replacement for the chiral linking group required in hydroxyureas for good in vivo activity against 5-Lipoxygenase. The principle is illustrated in two achiral 5-LO inhibitors: 858C, a more potent inhibitor than Zileuton and, 862C, a very poteng 5-LO inhibitor with good oral persistence.