Cough and its importance in COPD

Patients with COPD most frequently complain of breathlessness and cough and these are both increased during exacerbations. Studies have generally focused on quality of life during end-stage disease, where breathlessness becomes dominant and cough less important. There are very little data on the frequency and severity of cough in COPD or its impact on quality of life at different stages of disease. Little is known about the factors that influence objective cough counts in COPD. Cough may be a marker for progressive disease in milder COPD patients who continue to smoke, and it may be useful in case-finding for milder disease in the community. The cough reflex sensitivity is heightened in COPD compared with healthy volunteers and similar to that in subjects with asthma. The degree of airflow obstruction does not predict cough reflex sensitivity or objective cough counts, implying an independent process. Effective treatments for cough in COPD have not yet been identified. Improved outcome measures of cough, a better understanding of cough in the natural history of COPD, and its importance to patients are needed

Expression of transforming growth factor-β (TGF-β) in chronic idiopathic cough

In patients with chronic idiopathic cough, there is a chronic inflammatory response together with evidence of airway wall remodelling and an increase in airway epithelial nerves expressing TRPV-1. We hypothesised that these changes could result from an increase in growth factors such as TGFβ and neurotrophins

XEN-D0501, a Novel TRPV1 Antagonist, Does Not Reduce Cough in Refractory Cough Patients

RATIONALE: Heightened cough responses to inhaled capsaicin, a TRPV1 agonist, are characteristic of patients with chronic cough. However, previously a TRPV1 antagonist (SB-705498) failed to improve spontaneous cough frequency in these patients despite small reductions in capsaicin-evoked cough. OBJECTIVES: XEN-D0501 (potent TRPV1 antagonist) was compared with SB-705498 in pre-clinical studies to establish whether an improved efficacy profile would support a further clinical trial of XEN-D0501 in refractory chronic cough. METHODS: XEN-D0501 and SB-705498 were profiled against capsaicin in a sensory nerve activation assay and in vivo potency established against capsaicin-induced cough in the guinea pig. Twenty patients with refractory chronic cough participated in a double-blind, randomised, placebo-controlled, crossover study evaluating the effect of 14 days XEN-D0501 (oral, 4mg bd) versus placebo on awake cough frequency (primary outcome), capsaicin-evoked cough and patient reported outcomes. MEASUREMENTS AND MAIN RESULTS: XEN-D0501 was more efficacious and 1000-fold more potent than SB-705498 at inhibiting capsaicin-induced depolarization of guinea pig and human isolated vagus. In vivo, XEN-D0501 completely inhibited capsaicin-induced cough whereas 100-times more SB-705498 was required to achieve the same effect. In patients, XEN-D0501 substantially reduced maximal cough responses to capsaicin (mean change from baseline XEN-D0501 -19.3(±16.4) coughs vs. placebo -1.8(±5.8), p<0.0001), but not spontaneous awake cough frequency (mean change from baseline XEN-D0501 6.7c/h(±16.9) vs. placebo 0.4c/h(±13.7), p =0.41). CONCLUSIONS: XEN-D0501 demonstrated superior efficacy and potency in pre-clinical and clinical capsaicin challenge studies; despite this improved pharmacodynamic profile, spontaneous cough frequency did not improve, ruling out TRPV1 as an effective therapeutic target for refractory cough. Clinical trial registration available www.clinicaltrialsregister.eu, ID 2014-000306-36