Eliapixant (BAY 1817080), a P2X3 receptor antagonist, in refractory chronic cough: a randomised, placebo-controlled, crossover phase 2a study

Development of an Italian version of the Leicester cough questionnaire and its relationship with other symptom-specific measures for patients with chronic cough

OBJECTIVE

To implement subjective methods for measuring the impact of chronic cough on patients' daily life, including an Italian version of the symptom-specific, health status measure for patients with chronic cough, i.e. the Leicester Cough Questionnaire (LCQ).

METHODS

Sixty-five chronic cough patients attended a tertiary cough clinic on two separate occasions 8 weeks apart. The visual analogue scale for cough severity (VAS), the LCQ and the cough disturbance score (CDS) were administered on both occasions. The LCQ was adapted for Italian conditions following a forward-backward translation procedure. Concurrent validation, internal consistency, repeatability and responsiveness were determined.

RESULTS

The CDS, VAS and LCQ were correlated (r coefficients ranging from 0.69 to 0.94, p < 0.01). The internal consistency for each LCQ domain was high (alpha coefficient range 0.87-0.93), as was the 8-week repeatability of the LCQ in the patients (n = 36, 60 %) who displayed no change in CDS and VAS (intra-class correlation coefficient = 0.86, p < 001) over the same period. Patients who reported an improvement in CDS and VAS after 8 weeks (n = 29) also demonstrated significant improvements in each LCQ domain. The mean difference in LCQ total score before and after improvements was 2.26 (95 % CI: 1.58-4.47).

CONCLUSIONS

The Italian version of the LCQ appears to be just as valid as the other language versions of the questionnaire. In addition, the CDS appears to be a clinically useful, symptom-specific measure of the overall disturbance provoked by cough.

The bumpy road of purinergic inhibitors to clinical application in immune-mediated diseases

ABSTRACT

Purinergic signaling plays important roles throughout the body in the regulation of organ functions during and following the disruption of homeostasis. This is also reflected by the widespread expression of two families of purinergic receptors (P1 and P2) with numerous subtypes. In the last few decades, there has been increasing evidence that purinergic signaling plays an important role in the regulation of immune functions. Mainly, signals mediated by P2 receptors have been shown to contribute to immune system-mediated pathologies. Thus, interference with P2 receptors may be a promising strategy for the modulation of immune responses. Although only a few clinical studies have been conducted in isolated entities with limited success, preclinical work suggests that the use of P2 receptor inhibitors may bear some promise in various autoimmune diseases. Despite the association of P2 receptors with several disorders from this field, the use of P2 receptor antagonists in clinical therapy is still very scarce. In this narrative review, we briefly review the involvement of the purinergic system in immunological responses and clinical studies on the effect of purinergic inhibition on autoimmune processes. We then open the aperture a bit and show some preclinical studies demonstrating a potential effect of purinergic blockade on autoimmune events. Using suramin, a non-specific purinergic inhibitor, as an example, we further show that off-target effects could be responsible for observed effects in immunological settings, which may have interesting implications. Overall, we believe that it is worthwhile to further investigate this hitherto underexplored area.

Novel pharmacotherapeutic avenues for bladder storage dysfunction in men

INTRODUCTION

Bladder storage dysfunction is associated with low quality of life in men and remains a challenging field in pharmacotherapy because of low persistence followed by patient-perceived lack of efficacy and adverse effects. The persistent desire for the development of novel pharmacotherapy is evident, leading to numerous research efforts based on its pathophysiology.

AREAS COVERED

This review describes the pathophysiology, current pharmacotherapeutic strategies, and emerging novel drugs for male bladder storage dysfunction. The section on emerging pharmacotherapy provides an overview of current research, focusing on high-potential target molecules, particularly those being evaluated in ongoing clinical trials.

EXPERT OPINION

As pharmacotherapies targeting alpha-adrenergic, beta-adrenergic, and muscarinic receptors - the current primary targets for treating male bladder storage dysfunction - have demonstrated insufficient efficacy and side effects, researchers are exploring various alternative molecular targets. Numerous targets have been identified as central to regulating bladder afferent nerve activity, and their pharmacological effects and potential have been evaluated in animal-based experiments. However, there is a limited number of clinical trials for these new pharmacotherapies, and they have not demonstrated clear superiority over current treatments. Further research is needed to develop new effective pharmacotherapies for bladder storage dysfunction in men.

Druggable site near the upper vestibule determines the high affinity and P2X3 homotrimer selectivity of sivopixant/S-600918 and its analogue DDTPA

BACKGROUND AND PURPOSE

The P2X3 receptor, a trimeric ionotropic purinergic receptor, has emerged as a potential therapeutic target for refractory chronic cough (RCC). Nevertheless, gefapixant/AF-219, the only marketed P2X3 receptor antagonist, might lead taste disorders by modulating the human P2X2/3 (hP2X2/3) heterotrimer. Hence, in RCC drug development, compounds exhibiting strong affinity for the hP2X3 homotrimer and a weak affinity for the hP2X2/3 heterotrimer hold promise. An example of such a molecule is sivopixant/S-600918, a clinical Phase II RCC candidate with a reduced incidence of taste disturbance compared to gefapixant. Sivopixant and its analogue, (3-(4-([3-chloro-4-isopropoxyphenyl]amino)-3-(4-methylbenzyl)-2,6-dioxo-3,6-dihydro-1,3,5-triazin-1(2H)-yl)propanoic acid (DDTPA), exhibit both high affinity and high selectivity for hP2X3 homotrimers, compared with hP2X2/3 heterotrimers. The mechanism underlying the druggable site and its high selectivity remains unclear.

EXPERIMENTAL APPROACH

To analyse mechanisms that distinguish this drug candidate from other inhibitors of the P2X3 receptors we used a combination of chimera construction, site covalent occupation, metadynamics, mutagenesis and whole-cell recording.

KEY RESULTS

The high affinity and selectivity of sivopixant/DDTPA for hP2X3 receptors was determined by the tri-symmetric site located close to the upper vestibule. Substitution of only four amino acids inside the upper body domain of hP2X2 with those of hP2X3, enabled the hP2X2/3 heterotrimer to exhibit a similar level of apparent affinity for sivopixant/DDTPA as the hP2X3 homotrimer.

CONCLUSION AND IMPLICATIONS

From the receptor-ligand recognition perspective, we have elucidated the molecular basis of novel RCC clinical candidates' cough-suppressing properties and reduced side effects, offering a promising approach to the discovery of novel drugs that specifically target P2X3 receptors.

Efficacy and safety of eliapixant in diabetic neuropathic pain and prediction of placebo responders with an exploratory novel algorithm: results from the randomized controlled phase 2a PUCCINI study

ABSTRACT

Phase 2a of the PUCCINI study was a placebo-controlled, double-blind, parallel-group, multicenter, proof-of-concept study evaluating the efficacy and safety of the selective P2X3 antagonist eliapixant in patients with diabetic neuropathic pain (DNP) ( ClinicalTrials.gov NCT04641273). Adults with type 1 or type 2 diabetes mellitus with painful distal symmetric sensorimotor neuropathy of >6 months' duration and neuropathic pain were enrolled and randomized 1:1 to 150 mg oral eliapixant twice daily or placebo for 8 weeks. The primary endpoint was change from baseline in weekly mean 24-hour average pain intensity score at week 8. In total, 135 participants completed treatment, 67 in the eliapixant group and 68 in the placebo group. At week 8, the change from baseline in posterior mean 24-hour average pain intensity score (90% credible interval) in the eliapixant group was -1.56 (-1.95, -1.18) compared with -2.17 (-2.54, -1.80) for the placebo group. The mean treatment difference was 0.60 (0.06, 1.14) in favor of placebo. The use of a model-based framework suggests that various factors may contribute to the placebo-responder profile. Adverse events were mostly mild or moderate in severity and occurred in 51% of the eliapixant group and 48% of the placebo group. As the primary endpoint was not met, the PUCCINI study was terminated after completion of phase 2a and did not proceed to phase 2b. In conclusion, selective P2X3 antagonism in patients with DNP did not translate to any relevant improvement in different pain intensity outcomes compared with placebo. Funding: Bayer AG.

Comprehensive insights into potential roles of purinergic P2 receptors on diseases: Signaling pathways involved and potential therapeutics

BACKGROUND

Purinergic P2 receptors, which can be divided into ionotropic P2X receptors and metabotropic P2Y receptors, mediate cellular signal transduction of purine or pyrimidine nucleoside triphosphates and diphosphate. Based on the wide expression of purinergic P2 receptors in tissues and organs, their significance in homeostatic maintenance, metabolism, nociceptive transmission, and other physiological processes is becoming increasingly evident, suggesting that targeting purinergic P2 receptors to regulate biological functions and signal transmission holds significant promise for disease treatment.

AIM OF REVIEW

This review highlights the detailed mechanisms by which purinergic P2 receptors engage in physiological and pathological progress, as well as providing prospective strategies for discovering clinical drug candidates.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The purinergic P2 receptors regulate complex signaling and molecular mechanisms in nervous system, digestive system, immune system and as a result, controlling physical health states and disease progression. There has been a significant rise in research and development focused on purinergic P2 receptors, contributing to an increased number of drug candidates in clinical trials. A few influential pioneers have laid the foundation for advancements in the evaluation, development, and of novel purinergic P2 receptors modulators, including agonists, antagonists, pharmaceutical compositions and combination strategies, despite the different scaffolds of these drug candidates. These advancements hold great potential for improving therapeutic outcomes by specifically targeting purinergic P2 receptors.

The Therapeutic Landscape in Chronic Cough

In recent years, there has been a substantial increase in the development of antitussive therapies and the first new therapy, gefapixant has been licenced in Europe. This review describes current unlicenced treatments for chronic cough and details treatments currently in development for refractory chronic cough and cough in idiopathic pulmonary fibrosis, as well as compounds previously explored.

Molecular insights into P2X signalling cascades in acute kidney injury

Acute kidney injury (AKI) is a critical health issue with high mortality and morbidity rates in hospitalized individuals. The complex pathophysiology and underlying health conditions further complicate AKI management. Growing evidence suggests the pivotal role of ion channels in AKI progression, through promoting tubular cell death and altering immune cell functions. Among these channels, P2X purinergic receptors emerge as key players in AKI pathophysiology. P2X receptors gated by adenosine triphosphate (ATP), exhibit increased extracellular levels of ATP during AKI episodes. More importantly, certain P2X receptor subtypes upon activation exacerbate the situation by promoting the release of extracellular ATP. While therapeutic investigations have primarily focused on P2X4 and P2X7 subtypes in the context of AKI, while understanding about other subtypes still remains limited. Whilst some P2X antagonists show promising results against different types of kidney diseases, their role in managing AKI remains unexplored. Henceforth, understanding the intricate interplay between P2X receptors and AKI is crucial for developing targeted interventions. This review elucidates the functional alterations of all P2X receptors during normal kidney function and AKI, offering insights into their involvement in AKI. Notably, we have highlighted the current knowledge of P2X receptor antagonists and the possibilities to use them against AKI in the future. Furthermore, the review delves into the pathways influenced by activated P2X receptors during AKI, presenting potential targets for future therapeutic interventions against this critical condition.

Efficacy and Safety of Eliapixant in Overactive Bladder: The 12-Week, Randomised, Placebo-controlled Phase 2a OVADER Study

BACKGROUND

Effective, well-tolerated novel treatments for overactive bladder (OAB) are lacking. The P2X3 receptor antagonist eliapixant demonstrated potential to reduce OAB symptoms in preclinical studies.

OBJECTIVE

To evaluate the safety, tolerability, and efficacy of eliapixant in patients with OAB with urgency urinary incontinence (UUI).

DESIGN, SETTING AND PARTICIPANTS

OVADER was a 12-wk, randomised, placebo-controlled, double-blind, parallel-group, multicentre, phase 2a study (NCT04545580) conducted between 2020 and 2022 in private and institutional clinical practices. Eligible patients were aged ≥18 yr with wet OAB symptoms (urgency, urinary frequency, and urinary incontinence) for ≥3 mo before screening.

INTERVENTION

Randomisation (1:1 ratio) to oral eliapixant 125 mg or placebo twice daily.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary endpoint was the mean change from baseline in the mean number of UUI episodes/24 h over weeks 4, 8, and 12 according to an electronic bladder diary, evaluated using a repeated-measurement model in a Bayesian framework.

RESULTS AND LIMITATIONS

Of 202 patients enrolled, 85 were valid for per-protocol analysis. The primary efficacy endpoint was not met. The posterior probability for eliapixant superiority over placebo was 40% (point estimate 0.05, 95% credible interval -∞ to 0.38), which did not meet the predefined criterion of ≥90% probability. Secondary and exploratory endpoints were not met. The incidence of adverse events was similar in the eliapixant (n = 32, 63%) and placebo (n = 27, 56%) groups; most were mild and five led to discontinuation of eliapixant.

CONCLUSIONS

OVADER did not meet its clinical efficacy endpoints. Potential reasons include the nonspecific OAB symptom complex, the poorly understood pathophysiology, and the coinciding COVID-19 pandemic.

PATIENT SUMMARY

We tested whether a new drug called eliapixant would reduce symptoms of overactive bladder in comparison to placebo. We found that the drug did not work. More knowledge on how overactive bladder occurs is needed to find new drugs to treat this condition.

Mass Balance and Metabolic Pathways of Eliapixant, a P2X3 Receptor Antagonist, in Healthy Male Volunteers

BACKGROUND

Overactive adenosine triphosphate signaling via P2X3 homotrimeric receptors is implicated in multiple conditions. To fully understand the metabolism and elimination pathways of eliapixant, a study was conducted to assess the pharmacokinetics, mass balance, and routes of excretion of a single oral dose of the selective P2X3 receptor antagonist eliapixant, in addition to an in vitro characterization.

METHODS

In this single-center open-label non-randomized non-placebo-controlled phase I study, healthy male subjects (n = 6) received a single dose of 50 mg eliapixant blended with 3.7 MBq [14C]eliapixant as a PEG 400-based oral solution. Total radioactivity and metabolites excreted in urine and feces, and pharmacokinetics of total radioactivity, eliapixant, and metabolites in plasma were assessed via liquid scintillation counting and high-performance liquid chromatography-based methods coupled to radiometric and mass spectrometric detection. Metabolite profiles of eliapixant in human in vitro systems and metabolizing enzymes were also investigated.

RESULTS

After administration as an oral solution, eliapixant was rapidly absorbed, reaching maximum plasma concentrations within 2 h. Eliapixant was eliminated from plasma with a mean terminal half-life of 48.3 h. Unchanged eliapixant was the predominant component in plasma (72.6% of total radioactivity area under the curve). The remaining percentage of drug-related components in plasma probably represented the sum of many metabolites, detected in trace amounts. Mean recovery of total radioactivity was 97.9% of the administered dose (94.3-99.4%) within 14 days, with 86.3% (84.8-88.1%) excreted via feces and 11.6% (9.5-13.1%) via urine. Excretion of parent drug was minimal in feces (0.7% of dose) and urine (≈ 0.5%). In feces, metabolites formed by oxidation represented > 90% of excreted total radioactivity. The metabolites detected in the in vitro experiments were similar to those identified in vivo.

CONCLUSION

Complete recovery of administered eliapixant-related radioactivity was observed in healthy male subjects with predominant excretion via feces. Eliapixant was almost exclusively cleared by oxidative biotransformation (> 90% of dose), with major involvement of cytochrome P450 3A4. Excretion of parent drug was of minor importance (~ 1% of dose).

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov: NCT04487431 (registered 27 July 2020)/EudraCT number: 2020-000519-54 (registered 3 February 2020), NCT02817100 (registered 26 June 2016), NCT03310645 (registered 16 October 2017).

Cough medicines for children- time for a reality check

Cough medicines have been in use for over a century to treat the common and troublesome, but often helpful, symptoms of cough in children. They contain various combinations of "anti-tussive" drugs including opioids, antihistamines, herbal preparations, mucolytics, decongestants and expectorants. Whilst theoretically attractive for symptom relief when children are suffering, as time has passed these popular over the counter medicines have been shown to lack efficacy, delay more serious underlying diagnoses, and can cause complications and sometimes death. This has resulted in clinician concerns, a citizen petition to the American Food and Drug Association in 2007, some self-regulation from manufacturers and escalating restrictions on their use from regulatory agencies across the world over the last twenty years. This article will review the protective role of cough, juxtapose the conflicting treatment goals of suppressing a dry cough and promoting expectoration for a wet cough, consider the evidence basis for prescribing cough medicines in comparison to other more specific treatments such as for asthma [beta agonists] or infection [antibiotics], regulatory interventions, and conclude with the view that over counter cough medicines should not be used in children, especially young children.

Safety and efficacy of P2X3 receptor antagonist for the treatment of refractory or unexplained chronic cough: A systematic review and meta-analysis of 11 randomized controlled trials

BACKGROUND AND OBJECTIVES

Chronic refractory cough is a challenging condition that requires a thorough evaluation and management approach. P2X3 receptors that are ATP-dependent play an important part in nerve fiber sensitization and pathological pain pathways. We conducted this systematic review and meta-analysis to determine the long-term safety and efficacy of P2X3 receptor antagonist drugs in chronic cough.

METHODS

We systematically searched PubMed, Scopus, Web of Science, and Embase to identify all relevant published studies through January 15, 2023 that assessed P2X3 antagonists in chronic cough. The protocol was registered in the PROSPERO database with ID: CRD42023422408. Efficacy outcomes were awake (daytime) cough frequency, night cough frequency, 24-h cough frequency, Cough Severity Diary, and total Leicester Cough Questionnaire score. We used the random-effect model to pool the data using RStudio and CMA software.

RESULTS

A total of 11 randomized controlled trials comprising 1350 patients receiving a p2x3 antagonist compared to the placebo group were included in this meta-analysis. A significant decrease in 24-h cough frequency (MD = -4.99, 95% CI [-7.15 to -2.82], P < 0.01), awake (daytime) cough frequency (MD = -7.18, 95% CI [-9.98 to 4.37], P < 0.01), and total Leicester Cough Questionnaire score (MD = 1.74, 95% CI [1.02 to 2.46], P < 0.01) exhibited between the P2X3 antagonist and placebo groups. The frequency of the night cough showed an insignificant difference between the two groups. According to the safety, drug-related adverse events, dysgeusia, hypogeusia, and ageusia significantly increased between the P2X3 antagonist and placebo groups.

CONCLUSION

P2X3 receptor antagonists are promising drugs for treating chronic cough by significantly reducing the frequency, severity, and quality. Some potential side effects may include drug-related adverse events such as hypogeusia, ageusia, and dysgeusia.

Illuminating Airway Nerve Structure and Function in Chronic Cough

Airway nerves regulate vital airway functions including bronchoconstriction, cough, and control of respiration. Dysregulation of airway nerves underlies the development and manifestations of airway diseases such as chronic cough, where sensitization of neural pathways leads to excessive cough triggering. Nerves are heterogeneous in both expression and function. Recent advances in confocal imaging and in targeted genetic manipulation of airway nerves have expanded our ability to visualize neural organization, study neuro-immune interactions, and selectively modulate nerve activation. As a result, we have an unprecedented ability to quantitatively assess neural remodeling and its role in the development of airway disease. This review highlights our existing understanding of neural heterogeneity and how advances in methodology have illuminated airway nerve morphology and function in health and disease.

Burden of chronic cough on social participation, healthcare resource utilisation and activities of daily living in the Canadian Longitudinal Study on Aging (CLSA)

BACKGROUND

Chronic cough is a common troublesome condition, but it is unclear whether dry or productive chronic cough and sex, impacts the burden of cough differently.

METHODS

The Canadian Longitudinal Study on Aging is a nationally generalizable, stratified random sample of adults aged 45-85 years. Chronic cough was identified based on a self-reported daily cough in the last 12 months assessed at baseline (2011-2015) and follow-up (2015-2018). Odds ratios (95 % CI) for cough status and change in social participation activities (SPA), healthcare resource utilisation (HCRU), basic activities of daily living (ADLs) and instrumental activities of daily living (IADLs) were estimated using a weighted generalised estimating equation (WGEE). Results were stratified by sex, and adjusted for age, sex, smoking, body mass index, education, respiratory diseases and retirement status.

RESULTS

Overall, chronic cough was associated with less SPA, greater HCRU and impaired ADL/IADLs. Productive chronic cough in males was associated with SPA limited by health, ED visits and hospitalisation. Females with productive chronic cough was associated with reduced frequency of SPA and ED visit. Dry chronic cough in females was associated with SPA limited by health and ED visits. Both types of cough was associated with at least 1 impaired basic ADL, but only in females with productive chronic cough was there an association with any impairment in IADLs.

CONCLUSION

Chronic cough is associated with a greater burden on social participation, healthcare use and personal care.

Pharmacological interaction and immune response of purinergic receptors in therapeutic modulation

Nucleosides and purine nucleotides serve as transmitter and modulator agents that extend their functions beyond the cell. In this context, purinergic signaling plays a crucial role in regulating energy homeostasis and modulating metabolic alterations in tumor cells. Therefore, it is essential to consider the pharmacological targeting of purinergic receptors (PUR), which encompass the expression and inhibition of P1 receptors (metabotropic adenosine receptors) as well as P2 receptors (extracellular ATP/ADP) comprising P2X and P2Y receptors. Thus, the pharmacological interaction between inhibitors (such as RNA, monoclonal antibodies, and small molecules) and PUR represents a key aspect in facilitating the development of therapeutic interventions. Moreover, this review explores recent advancements in pharmacological inhibitors and the regulation of innate and adaptive immunity of PUR, specifically in relation to immunological and inflammatory responses. These responses encompass the release of pro-inflammatory cytokines (PIC), the production of reactive oxygen and nitrogen species (ROS and RNS), the regulation of T cells, and the activation of inflammasomes in all human leukocytes.

Efficacy and Tolerability of Gefapixant for Treatment of Refractory or Unexplained Chronic Cough: A Systematic Review and Dose-Response Meta-Analysis

Importance

Gefapixant represents an emerging therapy for patients with refractory or unexplained chronic cough.

Objective

To evaluate the efficacy and tolerability of gefapixant for the treatment of adults with refractory or unexplained chronic cough.

Data Sources

MEDLINE, Embase, Cochrane Central Register of Controlled Trials, and Web of Science from November 2014 to July 2023.

Study Selection

Two reviewers independently screened for parallel and crossover randomized clinical trials (RCTs) that compared, in patients with refractory or unexplained chronic cough, either gefapixant with placebo, or 2 or more doses of gefapixant with or without placebo.

Data Extraction and Synthesis

Two reviewers independently extracted data. A frequentist random-effects dose-response meta-analysis or pairwise meta-analysis was used for each outcome. The GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) approach was used to rate the certainty in whether patients would perceive the effects as important (greater than the minimal important difference [MID]) or small (less than the MID).

Main Outcomes and Measures

Cough frequency (measured using the VitaloJAK cough monitor; MID, 20%), cough severity (measured using the 100-mm visual analog scale [VAS]; higher score is worse; MID, 30 mm), cough-specific quality of life (measured using the Leicester Cough Questionnaire [LCQ]; score range, 3 [maximal impairment] to 21 [no impairment]; MID, 1.3 points), treatment-related adverse events, adverse events leading to discontinuation, and taste-related adverse events.

Results

Nine RCTs including 2980 patients were included in the primary analysis. Compared with placebo, gefapixant (45 mg twice daily) had small effects on awake cough frequency (17.6% reduction [95% CI, 10.6%-24.0%], moderate certainty), cough severity on the 100-mm VAS (mean difference, -6.2 mm [95% CI, -4.1 to -8.4]; high certainty), and cough-specific quality of life on the LCQ (mean difference, 1.0 points [95% CI, 0.7-1.4]; moderate certainty). Compared with placebo, gefapixant (45 mg twice daily) probably caused an important increase in treatment-related adverse events (32 more per 100 patients [95% CI, 13-64 more], moderate certainty) and taste-related adverse events (32 more per 100 patients [95% CI, 22-46 more], high certainty). High-certainty evidence suggests that gefapixant (15 mg twice daily) had small effects on taste-related adverse events (6 more per 100 patients [95% CI, 5-8 more]).

Conclusions and Relevance

Compared with placebo, gefapixant (45 mg orally twice daily) led to modest improvements in cough frequency, cough severity, and cough-specific quality of life but increased taste-related adverse events.

Potential applications of P2X3 receptor antagonists in the treatment of refractory cough

Refractory chronic cough is defined as a clinical condition in which the cause of the cough remains unclear after comprehensive examination and treatment, or the cause is clear but symptomatic treatment is ineffective. Patients with refractory chronic cough experience a variety of physiological and psychological issues that significantly lower their quality of life and place a significant socio-economic burden on society. As a result, research both domestically and internationally has turned heavily toward these patients. Recently, several studies have identified P2X3 receptor antagonists for the treatment of refractory chronic cough, and this paper reviews the background, mechanism of action, evidence-based proof and application prospects of this class of drugs. KEY MESSAGE: There were plenty of studies about P2X3 receptor antagonists in the past, and in recent years this series of drugs are effective in refractory chronic cough. Although review articles summarizing have been published previously, most have focused on their chemical properties rather than their clinical aspects, with some omitting drugs that have been in clinical studies for nearly two years such as Eliapixant and Sivopixant. Focusing on four P2X3 receptor antagonists with proven efficacy in clinical studies, we analyzed the characteristics and disadvantages of each drug by comparing their clinical results of them and theoretically explained the common side effects of these drugs, as well as their potential for treating refractory chronic cough. This article can be used as a reference for the follow-up studies of P2X3 receptor antagonists in chronic cough. Additionally, it also has implications for the clinical focus of the drug and the approaches to relieve some side effects.

Benzonatate Safety and Effectiveness: A Systematic Review of the Literature

OBJECTIVE

To review the available literature regarding the treatment effects and efficacy of benzonatate needed to better inform patients, providers, and regulators evaluating its role in modern medical therapies.

DATA SOURCES

Comprehensive literature searches were conducted in PubMed, Embase (Elsevier), Cochrane Library, and Scopus for original research articles evaluating the effectiveness, tolerability, and safety profile of benzonatate from January 1956 through August 2022.

STUDY SELECTION AND DATA EXTRACTION

The identified studies were screened for relevance and then assessed for inclusion through a full-text review, data extraction, and quality assessment by multiple reviewers using the online software Covidence.

DATA SYNTHESIS

The selection process resulted in 37 articles consisting of 21 cohort studies, 5 experimental studies, and 11 case studies and series. Initial clinical studies exploring potential therapeutic benefits collected data from very small populations and limited clinical settings. Safety is primarily assessed in terms of toxicity due to overdose or inappropriate use. Quality assessment raised concerns for high degrees of biases primarily related to the limited sample size, data collection, generalizability, and study design.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

This review reveals substantial limitations within existing evidence pertaining to the safety and clinical effectiveness of benzonatate and thus, a need for large observational studies or randomized trials to better characterize its role and value in modern medical practice.

CONCLUSIONS

Rising safety concerns should bring closer scrutiny upon the prescription of benzonatate whose approval is founded upon evidence that would not stand up to current regulatory review.

Chronic cough relief by allosteric modulation of P2X3 without taste disturbance

P2X receptors are cation channels that sense extracellular ATP. Many therapeutic candidates targeting P2X receptors have begun clinical trials or acquired approval for the treatment of refractory chronic cough (RCC) and other disorders. However, the present negative allosteric modulation of P2X receptors is primarily limited to the central pocket or the site below the left flipper domain. Here, we uncover a mechanism of allosteric regulation of P2X3 in the inner pocket of the head domain (IP-HD), and show that the antitussive effects of quercetin and PSFL2915 (our nM-affinity P2X3 inhibitor optimized based on quercetin) on male mice and guinea pigs were achieved by preventing allosteric changes of IP-HD in P2X3. While being therapeutically comparable to the newly licensed P2X3 RCC drug gefapixant, quercetin and PSFL2915 do not have an adverse effect on taste as gefapixant does. Thus, allosteric modulation of P2X3 via IP-HD may be a druggable strategy to alleviate RCC.

DT-0111: a novel P2X3 receptor antagonist

Extracellular adenosine 5'-triphosphate (ATP) acts as an autocrine and paracrine agent, the actions of which on affected cells are mediated by P2 receptors (P2R), which include trans cell-membrane cationic channels (P2XRs), and G protein coupled receptors (P2YRs). The mammalian P2X receptors form homotrimeric or heterotrimeric cationic channels, each of which contains three ATP-binding sites. There are seven homotrimeric P2X receptors (P2X1-7) and three heteromeric (P2X2/P2X3, P2X4/P2X6, P2X1/P2X5). In the lungs and airways, ATP activates P2X3 and P2X2/3 receptors (P2X3R, P2X2/3R, respectively) localized on vagal sensory nerve terminals resulting in bronchoconstriction, and cough, and probably also localized release of pro-inflammatory neuropeptides via the axon reflex. Currently, several P2X3R and P2X2/3R antagonists are being developed as drug-candidates for the treatment of chronic cough. This report presents the receptor affinity data of a novel water-soluble small molecule, DT-0111, that acts as a selective P2X3R antagonist.

Efficacy and safety of pharmacotherapy for refractory or unexplained chronic cough: a systematic review and network meta-analysis

Background

Refractory chronic cough (RCC) has a significant impact on patient's health-related quality of life and represents a challenge in clinical management. However, the optimal treatment for RCC remains controversial. This study aimed to investigate and compare the efficacy and safety of the current pharmacological therapeutic options for RCC.

Methods

A systematic review was performed by searching PubMed, Web of Science, Embase, and Ovid databases from January 1, 2008 to March 1, 2023. All randomised control trials (RCTs) reporting outcomes of efficacy or/and safety were included in the Bayesian network meta-analysis. Here, we compared the effects on Leicester Cough Questionnaire (LCQ), Visual Analogue Scale (VAS), and objective cough frequency of patients with RCC. Besides, we also compared the incidence of adverse events (AEs) for analysis of safety. PROSPERO registration: CRD42022345940.

Findings

19 eligible RCTs included 3326 patients and 7 medication categories: P2X3 antagonist, GABA modulator, Transient Receptor Potential (TRP) modulator, NK-1 agonist, opioid analgesic, macrolide, and sodium cromoglicate. Compared with placebo, mean difference (MD) of LCQ and 24 h cough frequency for P2X3 antagonist relief were 1.637 (95% CI: 0.887-2.387) and -11.042 (P = 0.035). Compared with placebo, effect sizes (MD for LCQ and cough severity VAS) for GABA modulator were 1.347 (P = 0.003) and -7.843 (P = 0.003). In the network meta-analysis, gefapixant is the most effective treatment for patients with RCC (The Surface Under the Cumulative Ranking Curves (SUCRA) is 0.711 in LCQ, 0.983 in 24 h cough frequency, and 0.786 in cough severity VAS). Lesogaberan had better efficacy than placebo (SUCRA: 0.632 vs. 0.472) in 24 h cough frequency. Eliapixant and lesogaberan had better efficacy than placebo in cough severity VAS. However, TRP modulator had worse efficacy than placebo. In the meta-analysis of AEs, the present study found P2X3 antagonist had a significant correlation to AEs (RR: 1.129, 95% CI: 1.012-1.259), especially taste-related AEs (RR: 6.216, P < 0.05).

Interpretation

In this network meta-analysis, P2X3 antagonist showing advantages in terms of efficacy is currently the most promising medication for treatment of RCC. GABA modulator also showed potential efficacy for RCC but with AEs of the central system. Nevertheless, the role of TRP modulator needed to be revisited. Further research is needed to determine the potential beneficiary population for optimizing the pharmacological management of chronic cough.

Funding

National Natural Science Foundation of China (81870079), Guangdong Science and Technology Project (2021A050520012), Incubation Program of National Science Foundation for Distinguished Young Scholars (GMU2020-207).

From bench to bedside: The role of cough hypersensitivity in chronic cough

BACKGROUND

Chronic cough is a burdensome condition characterized by persistent cough lasting longer than 8 weeks. Chronic cough can significantly affect quality of life, physical function and productivity, with many people troubled with a cough that lasts for months or even years. People with chronic cough commonly report a persistent urge to cough with frequent bouts of coughing triggered by innocuous stimuli, which has led to the concept of cough hypersensitivity.

MAIN BODY

Both central and peripheral neural pathways regulate cough, and although mechanisms driving development of cough hypersensitivity are not fully known, sensitization of these neural pathways contributes to excessive cough triggering in cough hypersensitivity. Effective therapies that control chronic cough are currently lacking. Recent therapeutic development has focused on several ion channels and receptors involved in peripheral activation of cough (e.g., transient receptor potential channels, P2 × 3 receptors and voltage-gated sodium channels) or central cough processing (e.g., neurokinin-1 [NK-1] receptors and nicotinic acetylcholine receptors).

CONCLUSION

These targeted therapies provide novel insights into mechanisms underlying cough hypersensitivity and may offer new treatment options for people with chronic cough. In this review, we explore preclinical and clinical studies that have improved our understanding of the mechanisms responsible for chronic cough and discuss the most promising targeted approaches to date, including trials of P2 × 3-receptor antagonists and NK-1-receptor antagonists.

A smartphone-based application for cough counting in patients with acute asthma exacerbation

BACKGROUND

While tools exist for objective cough counting in clinical studies, there is no available tool for objective cough measurement in clinical practice. An artificial intelligence (AI)-based cough count system was recently developed that quantifies cough sounds collected through a smartphone application. In this prospective study, this AI-based cough algorithm was applied among real-world patients with an acute exacerbation of asthma.

METHODS

Patients with an acute asthma exacerbation recorded their cough sounds for 7 days (2 consecutive hours during awake time and 5 consecutive hours during sleep) using CoughyTM smartphone application. During the study period, subjects received systemic corticosteroids and bronchodilator to control asthma. Coughs collected by application were counted by both the AI algorithm and two human experts. Subjects also provided self-measured peak expiratory flow rate (PEFR) and completed other outcome assessments [e.g., cough symptom visual analogue scale (CS-VAS), awake frequency, salbutamol use] to investigate the correlation between cough and other parameters.

RESULTS

A total of 1,417.6 h of cough recordings were obtained from 24 asthmatics (median age =39 years). Cough counts by AI were strongly correlated with manual cough counts during sleep time (rho =0.908, P<0.001) and awake time (rho =0.847, P<0.001). Sleep time cough counts were moderately to strongly correlated with CS-VAS (rho =0.339, P<0.001), the frequency of waking up (rho =0.462, P<0.001), and salbutamol use at night (rho =0.243, P<0.001). Weak-to-moderate correlations were found between awake time cough counts and CS-VAS (rho =0.313, P<0.001), the degree of activity limitation (rho =0.169, P=0.005), and salbutamol use at awake time (rho =0.276, P<0.001). Neither awake time nor sleep time cough counts were significantly correlated with PEFR.

CONCLUSIONS

The strong correlation between cough counts using the AI-based algorithm and human experts, and other indicators of patient health status provides evidence of the validity of this AI algorithm for use in asthma patients experiencing an acute exacerbation. Study findings suggest that CoughyTM could be a novel solution for objectively monitoring cough in a clinical setting.

The Severity of Chronic Cough Diary (SCCD): development and content validation of a novel patient-reported outcome instrument for evaluating the symptom experience of chronic cough

BACKGROUND

Refractory chronic cough (RCC), a cough lasting longer than 8 weeks with an unexplained underlying etiology and unresponsive to conventional treatment, can have substantial effects on patients' quality of life. For assessment of the efficacy of antitussive medication in clinical trials in RCC, patient-reported outcome (PRO) instruments should be fit for purpose with appropriate content validity. Here we describe the qualitative testing of a newly developed PRO instrument: the Severity of Chronic Cough Diary (SCCD).

METHODS

The SCCD was developed to assess patients' symptom experience of cough in patients with RCC. A preliminary version was tested and refined based on an iterative process in a qualitative study. In total, three rounds of interviews were conducted with adult participants diagnosed with RCC in the USA (n = 19) and UK (n = 10). Rounds 1-3 consisted of hybrid concept elicitation (CE) interviews and cognitive interviews (CIs), with Round 3 also including interviews in a subset of participants (n = 5) about the usability of the SCCD as administered on an electronic handheld device.

RESULTS

The CE interviews identified concepts important to patients' experiences related to RCC that were broadly in line with the concepts in the preliminary version of the SCCD. Participants provided positive feedback on the draft SCCD across all CI rounds, reporting the instrument to be relevant and straightforward to complete, and containing a comprehensive set of concepts to evaluate their symptom experience of RCC. Participants demonstrated a good understanding of proposed item wording, response options, and the 24-hour recall period, and thought completion of the SCCD on the electronic device was easy. Following revisions based on results from each interview round, the SCCD at the end of this qualitative research study had 14 items assessing the concepts of: cough symptoms (five items), symptoms related to cough (four items), disruption to activities due to cough (three items), and disruption to sleep due to cough (two items).

CONCLUSIONS

The results of this study provide qualitative evidence supporting the content validity of the SCCD as a PRO instrument for evaluating outcomes of therapies for RCC in clinical trials.

Efficacy and safety of gefapixant for chronic cough: a meta-analysis of randomised controlled trials

BACKGROUND

The efficacy and safety of gefapixant in adults with chronic cough remain unclear. Our objective was to assess the efficacy and safety of gefapixant using updated evidence.

METHODS

MEDLINE, Cochrane Central Register of Controlled Trials (CENTRAL) and Embase databases were searched from inception through September 2022. Subgroup analysis based on dose of gefapixant (i.e. ≤20, 45-50 and ≥100 mg twice daily for low, moderate and high doses, respectively) was performed to explore a potential dose-dependent effect.

RESULTS

Five studies involving seven trials showed the efficacy of moderate- or high-dose gefapixant for reducing objective 24-h cough frequency (estimated relative reduction 30.9% and 58.5%, respectively) (i.e. primary outcome) and awake cough frequency (estimated relative reduction 47.3% and 62.8%, respectively). Night-time cough frequency was only reduced with high-dose gefapixant. Consistently, the use of moderate- or high-dose gefapixant significantly alleviated cough severity and improved cough-related quality of life, but increased the risk of all-cause adverse events (AEs), treatment-related AEs and ageusia/dysgeusia/hypogeusia. Subgroup analysis showed dose dependency in both efficacy and AEs with a cut-off dose being ≥45 mg twice daily.

CONCLUSIONS

This meta-analysis revealed dose-dependent efficacy and adverse effects of gefapixant against chronic cough. Further studies are required to investigate the feasibility of moderate-dose (i.e. 45-50 mg twice daily) gefapixant in clinical practice.

Efficacy and Safety of Eliapixant in Refractory Chronic Cough: The Randomized, Placebo-Controlled Phase 2b PAGANINI Study

INTRODUCTION

The PAGANINI study evaluated the efficacy and safety of the selective P2X3 antagonist eliapixant in patients with refractory chronic cough (RCC).

METHODS

PAGANINI was a randomized, double-blind, parallel-group, placebo-controlled, multicenter, dose-finding, phase 2b study. Adults with RCC lasting ≥ 12 months and cough severity ≥ 40 mm on a visual analog scale at screening were enrolled. Participants were randomized 1:1:1:1 to twice-daily 25 mg, 75 mg, or 150 mg oral eliapixant or placebo for 12 weeks. The primary endpoint was change from baseline in 24-h cough count after 12 weeks of intervention.

RESULTS

Overall, 310 participants were randomized to twice-daily eliapixant 25 mg (n = 75), 75 mg (n = 78), 150 mg (n = 80), or placebo (n = 77). A statistically significant dose-response signal with eliapixant was detected for the primary endpoint (all dose-response models, adjusted p < 0.1; one-sided). Adverse events (AEs) were reported in 39 (51%) participants with placebo and 43-51 (57-65%) participants receiving eliapixant. The most common AE was dysgeusia, occurring in 1% (n = 1) of the placebo group and 1-16% (n = 1-13) of the eliapixant groups in a dose-related manner. One case of a moderate drug-induced liver injury occurred in a participant receiving 150 mg twice-daily eliapixant.

CONCLUSION

Eliapixant demonstrated efficacy and a favorable taste tolerability profile in RCC. However, a drug-induced liver injury contributed to intensified liver monitoring in clinical trials with eliapixant and discontinuation of the entire development program in all indications by Bayer AG.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT04562155; registered September 18, 2020.

Cough desensitization treatment for patients with refractory chronic cough: results of a second pilot randomized control trial

OBJECTIVE

The purpose of this study was to collect pilot efficacy data on a novel treatment for refractory chronic cough (RCC), which we call cough desensitization treatment (CDT).

DESIGN AND METHODS

In this parallel cohort, sham-controlled, randomized controlled trial, 21 adults with RCC were randomly assigned to 12 sessions of either CDT (progressive doses of aerosolized capsaicin while behaviorally suppressing cough; n = 11) or a sham treatment (repeated exposure to aerosolized saline; n = 9). The Leicester Cough Questionnaire (LCQ) was the primary outcome measure. Perceived cough severity with a visual analogue scale and cough challenge testing (for measuring cough-reflex sensitivity) were secondary outcome measures. Data were analyzed with mixed effects linear regression and follow-up contrasts.

RESULTS

Results on all measures favored CDT. Excluding one sham participant, whose baseline LCQ scores were deemed unreliable, mean change in LCQ at 3-weeks post treatment was 6.35 and 2.17 in the CDT and sham groups, respectively. There was moderate to strong evidence of a greater improvement in the CDT group in total LCQ score (p = .058) and LCQ Psychological domain (p = .026) and Physical domain (p = .045) scores. Strong evidence was found for a greater reduction in urge-to-cough during CCT in the CDT group (p = .037) and marginal for a reduction in the capsaicin cough-reflex sensitivity (p = .094). There was weak evidence of a greater reduction in cough severity in the CDT group (p = .103).

DISCUSSION

Although the study is limited due to the small sample size, the data provide additional evidence supporting further research on CDT. CDT resulted in a greater change in the primary efficacy measure (LCQ) than both pharmaceutical and behavioral treatments currently found in the literature.

TRIAL REGISTRATION

This trial (NCT05226299) was registered on Clinicaltrials.gov on 07/02/2022.

The P2X3 receptor antagonist filapixant in patients with refractory chronic cough: a randomized controlled trial

BACKGROUND

P2X3 receptor antagonists seem to have a promising potential for treating patients with refractory chronic cough. In this double-blind, randomized, placebo-controlled study, we investigated the efficacy, safety, and tolerability of the novel selective P2X3 receptor antagonist filapixant (BAY1902607) in patients with refractory chronic cough.

METHODS

Following a crossover design, 23 patients with refractory chronic cough (age: 60.4 ± 9.1 years) received ascending doses of filapixant in one period (20, 80, 150, and 250 mg, twice daily, 4-days-on/3-days-off) and placebo in the other. The primary efficacy endpoint was the 24-h cough frequency on Day 4 of each dosing step. Further, subjective cough severity and health-related quality of life were assessed.

RESULTS

Filapixant at doses ≥ 80 mg significantly reduced cough frequency and severity and improved cough health-related quality of life. Reductions in 24-h cough frequency over placebo ranged from 17% (80 mg dose) to 37% (250 mg dose), reductions over baseline from 23% (80 mg) to 41% (250 mg) (placebo: 6%). Reductions in cough severity ratings on a 100-mm visual analog scale ranged from 8 mm (80 mg) to 21 mm (250 mg). No serious or severe adverse events or adverse events leading to discontinuation of treatment were reported. Taste-related adverse events occurred in 4%, 13%, 43%, and 57% of patients treated with filapixant 20, 80, 150, and 250 mg, respectively, and in 12% treated with placebo.

CONCLUSIONS

Filapixant proved to be efficacious, safe, and-apart from the occurrence of taste disturbances, especially at higher dosages-well tolerated during the short therapeutic intervention. Clinical trial registration EudraCT, eudract.ema.europa.eu, 2018-000129-29; ClinicalTrials.gov, NCT03535168.

A systematic review and meta-analysis of neuromodulators to treat chronic airway hypersensitivity

OBJECTIVES

Chronic laryngitis can present with numerous symptoms, including chronic cough. Patients who do not respond to standard treatment are sometimes diagnosed with chronic airway hypersensitivity (CAH). In many centers, neuromodulators are prescribed off-label despite limited evidence of efficacy. A previous meta-analysis suggested neuromodulator therapy improved cough-related quality-of-life (QoL). This current updated and expanded meta-analysis examined whether neuromodulators reduced cough frequency, reduced cough severity, and/or improved QoL in CAH patients.

DATA SOURCES

PubMed, Embase, Medline, Cochrane Review, and publication bibliographies were searched from 01/01/2000 to 07/31/2021 using MESH terms.

REVIEW METHODS

PRISMA guidelines were followed. 999 abstracts were identified/screened, 28 studies were fully reviewed, and 3 met inclusion criteria. Only randomized controlled trials (RCT) investigating CAH patients with comparable cough-related outcomes were included. Three authors reviewed potentially eligible papers. Fixed-effect models and calculated pooled estimates using the Inverse-Variance method were used.

RESULTS

The estimated difference in change in log coughs per hour (from baseline to intervention end) between treatment and control groups was -0.46, 95%CI [-0.97; 0.05]. Estimated change-from-baseline in VAS scores was -12.24, 95 % CI [-17.84; -6.65] lower for patients who received treatment vs placebo. Estimated change-from-baseline for LCQ scores was 2.15, 95 % CI [1.49-2.80] higher for patients who receive treatment vs placebo. Only change in LCQ score was clinically significant.

CONCLUSIONS

This study tentatively suggests that neuromodulators have the potential to reduce cough symptoms associated with CAH. However, high-quality evidence is lacking. This could be due to limited treatment effect or significant limitations in the design and comparability of existing trials. A well-designed and properly powered RCT is needed to authoritatively test the efficacy of neuromodulators for the treatment of CAH.

LEVEL OF EVIDENCE

Level I, evidence from a systematic review or meta-analysis of all relevant RCTs (randomized controlled trial) or evidence-based clinical practice guidelines based on systematic reviews of RCTs or three or more RCTs of good quality that have similar results.

P2X receptors: Insights from the study of the domestic dog

Fifty years ago, the late Geoffrey Burnstock described the concept of purinergic nerves and transmission bringing into existence the broader concepts of purinergic signaling including P2X receptors. These receptors are trimeric ligand-gated cation channels activated by extracellular adenosine 5'-triphosphate (ATP). P2X receptors have important roles in health and disease and continue to gain interest as potential therapeutic targets in inflammatory, neurological, cardiovascular and many other disorders including cancer. Current understanding of P2X receptors has largely arisen from the study of these receptors in humans and rodents, but additional insights have been obtained from the study of P2X receptors in the domestic dog, Canis familiaris. This review article will briefly introduce purinergic signaling and P2X receptors, before detailing the pharmacological profiles of the two recombinant canine P2X receptors studied to date, P2X7 and P2X4. The article will then describe the current state of knowledge concerning the distribution and function of the P2X receptor family in dogs. The article will also discuss the characterization of single nucleotide polymorphisms in the canine P2RX7 gene, and contrast this variation to the canine P2RX4 gene, which is largely conserved between dogs. Finally, this article will outline published examples of the use of dogs to study the pharmacokinetics of P2X7 and P2X3 antagonists, and how they have contributed to the preclinical testing of antagonists to human P2X7, CE-224,535, and human P2X3, Gefapixant (AF-219, MK-7264) and Eliapixant (BAY, 1817080), with Gefapixant gaining recent approval for use in the treatment of refractory chronic cough in humans. This article is part of the Special Issue on 'Purinergic Signaling: 50 years'.

P2X3-P2X7 SNPs and gene-gene and gene-environment interactions on pediatric asthma

BACKGROUND

To investigate the relationship between polymorphisms of P2X3, P2X7 genes and environment interaction with susceptibility of childhood asthma.

METHODS

We conducted a matched case-control study with 170 cases and 175 healthy controls. The rs10896611, rs2276038, rs3781899 in P2X3 and rs1718119, rs3751143 in P2X7 polymorphisms were genotyped using the technique of an improved multiplex ligation detection reaction. Gene-gene, gene-environment and haplotype-environment interactions were tested using the generalized multi-factor dimensionality reduction method.

RESULTS

There were no differences between cases and controls in allele or genotype frequencies of P2X3 and P2X7. The C/C, G/C genotypes of rs10896611, and C/C, C/T genotypes of rs2276038 and G/G, G/A genotypes of rs3781899 were associated with asthmatic cough (p > 0.05). The haplotype GCT of P2X3 reduced the risk of asthma (OR = 0.48, p = 0.048), and the haplotypes AGT (OR = 0.45, p = 0.001) and GCC (OR = 2.16, p = 0.002) were associated with asthmatic cough. The haplotype AA of P2X7 increased risk of asthma severity (p < 0.05). The three-locus model indicated a potential haplotype-environment interaction in GCT, ETS, and pet (p = 0.001).

CONCLUSIONS

The rs10896611, rs2276038 and rs3781899 of P2X3 minor alleles increased the risk of asthmatic cough. Haplotype GCT of P2X3 was a protective factor for asthma, the haplotype AGT was a protective factor and GCC was a risk factor for asthma with cough. In addition, the interactions of haplotype GCT of P2X3, ETS and pet may increase an individual's susceptibility to asthma.

Canadian Health Care Professionals' Familiarity with Chronic Cough Guidelines and Experiences with Diagnosis and Management: A Cross-Sectional Survey

INTRODUCTION

Educational programs on chronic cough may improve patient care, but little is known about how Canadian physicians manage this common debilitating condition. We aimed to investigate Canadian physicians' perceptions, attitudes, and knowledge of chronic cough.

METHODS

We administered a 10-min anonymous, online, cross-sectional survey to 3321 Canadian physicians in the Leger Opinion Panel who managed adult patients with chronic cough and had been in practice for > 2 years.

RESULTS

Between July 30 and September 22, 2021, 179 physicians (101 general practitioners [GPs] and 78 specialists [25 allergists, 28 respirologists, and 25 ear/nose/throat specialists]) completed the survey (response rate: 5.4%). In a month, GPs saw a mean of 27 patients with chronic cough, whereas specialists saw 46. About one-third of physicians appropriately identified a duration of > 8 weeks as the definition for chronic cough. Many physicians reported not using international chronic cough management guidelines. Patient referrals and care pathways varied considerably, and patients frequently experienced lost to follow-up. While physicians endorsed nasal and inhaled corticosteroids as common treatments for chronic cough, they rarely used other guideline-recommended treatments. Both GPs and specialists expressed high interest in education on chronic cough.

CONCLUSION

This survey of Canadian physicians demonstrates low uptake of recent advances in chronic cough diagnosis, disease categorization, and pharmacologic management. Canadian physicians also report unfamiliarity with guideline-recommended therapies, including centrally acting neuromodulators for refractory or unexplained chronic cough. This data highlights the need for educational programs and collaborative care models on chronic cough in primary and specialist care.

A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Phase 2b Trial of P2X3 Receptor Antagonist Sivopixant for Refractory or Unexplained Chronic Cough

INTRODUCTION

To determine the optimal dose of sivopixant, a highly selective P2X3 receptor antagonist, for refractory or unexplained chronic cough (RCC/UCC).

METHODS

In this phase 2b, randomized, double-blind, placebo-controlled, parallel-group, multicenter trial, patients received sivopixant 50, 150, or 300 mg or placebo once daily for 4 weeks. The primary endpoint was a change from baseline in 24-h cough frequency (coughs/h) with sivopixant vs placebo.

RESULTS

Overall, 390/406 randomized patients completed the study. Placebo-adjusted changes in hourly cough count over 24 h were 13.17% (P = 0.3532), - 1.77% (P = 0.8935), and - 12.47% (P = 0.3241) and in cough severity (visual analog scale) were 1.75 mm (P = 0.5854), - 1.21 mm (P = 0.7056), and - 6.55 mm (P = 0.0433) with sivopixant 50, 150, and 300 mg, respectively. Placebo-adjusted changes from baseline in Leicester Cough Questionnaire total scores were - 0.37 (P = 0.4207), - 0.07 (P = 0.8806), and 0.69 (P = 0.1473) with sivopixant 50, 150, and 300 mg, respectively. Additionally, 61.3%, 78.3%, 86.8%, and 71.4% of patients receiving sivopixant 50, 150, and 300 mg and placebo, respectively, reported any improvements in Patient Global Impression of Change. The incidence of treatment-emergent adverse events (TEAEs) was 25.7%, 32.0%, 49.0%, and 20.6% in sivopixant 50, 150, and 300 mg and placebo groups, respectively; all TEAEs in the sivopixant group were mild-to-moderate.

CONCLUSION

Sivopixant did not demonstrate a statistically significant difference vs placebo in change from baseline in 24-h cough frequency. The dose of 300 mg has potential for RCC/UCC, showing the greatest improvements in cough frequency and patient-reported outcomes and dose-related mild to moderate reversible taste disturbance, although further trials are needed.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT04110054; registered September 26, 2019.

Gefapixant, a Novel P2X3 Antagonist, Protects against Post Myocardial Infarction Cardiac Dysfunction and Remodeling Via Suppressing NLRP3 Inflammasome

OBJECTIVE

The ATP responsive P2 purinergic receptors can be subdivided into metabotropic P2X family and ionotropic P2Y family. Among these, P2X3 is a type of P2X receptor which is specifically expressed on nerves, especially on pre-ganglionic sensory fibers. This study investigates whether gefapixant possesses the potential of inhibiting cardiac sympathetic hypersensitivity to protect against cardiac remodeling in the context of myocardial infarction.

METHODS

The Sprague-Dawley rats were divided randomly into three groups: sham group-myocardial infarction group, and myocardial infarction with gefapixant treatment group. Myocardial infarction was induced by left anterior descending branch ligation. The gefapixant solution was intraperitoneally injected each time per day for 7 days and the appropriate dosage of gefapixant was determined according to the results of hematoxylin-eosin (HE) staining and myocardial injury biomarkers. Conditions of cardiac function were assessed by echocardiograph and cardiac fibrosis was evaluated by Western blotting and immunofluorescence staining of collagen I and collagen III. The sympathetic innervation was detected by norepinephrine concentration (pg/mL), in-vivo electrophysiology, and typical sympathetic biomarkers. Inflammatory cell infiltration was shown from immunofluorescence staining and pro-inflammatory signaling pathway activation was checked by immunohistology, quantitative realtime PCR (qPCR) and Western blotting.

RESULTS

It was found that gefapixant injection of 10 mg/kg per day had the highest dosage-efficacy ratio. Furthermore, gefapixant treatment improved cardiac pump function as shown by increased LVEF and LVFS, and decreased LVIDd and LVIDs. The expression levels of collagen I and collagen III, and TNF-α were all decreased by P2X3 inhibition. Mechanistically, the decreased activation of nucleotide-binding and oligomerization domain-like receptors family pyrin-domain-containing 3 (NLRP3) inflammasome and subsequent cleavage of caspase-1 which modulated interleukin-1β (IL-1β) and IL-18 level in heart after gefapixant treatment were associated with the suppressed cardiac inflammation.

CONCLUSION

It is suggested that P2X3 inhibition by gefapixant ameliorates post-infarct autonomic nervous imbalance, cardiac dysfunction, and remodeling possibly via inactivating NLRP3 inflammasome.

Role of ATP in migraine mechanisms: focus on P2X3 receptors

Migraine is a major health burden worldwide with complex pathophysiology and multifarious underlying mechanisms. One poorly understood issue concerns the early steps in the generation of migraine pain. To elucidate the basic process of migraine pain further, it seems useful to consider key molecular players that may operate synergistically to evoke headache. While the neuropeptide CGRP is an important contributor, we propose that extracellular ATP (that generally plays a powerful nociceptive role) is also a major component of migraine headache, acting in concert with CGRP to stimulate trigeminal nociceptive neurons. The aim of the present focused review is to highlight the role of ATP activating its P2X3 membrane receptors selectively expressed by sensory neurons including their nerve fiber terminals in the meninges. Specifically, we present data on the homeostasis of ATP and related purines in the trigeminovascular system and in the CNS; the basic properties of ATP signalling at peripheral and central nerve terminals; the characteristics of P2X3 and related receptors in trigeminal neurons; the critical speed and persistence of P2X3 receptor activity; their cohabitation at the so-called meningeal neuro-immune synapse; the identity of certain endogenous agents cooperating with ATP to induce neuronal sensitization in the trigeminal sensory system; the role of P2X3 receptors in familial type migraine; the current state of P2X3 receptor antagonists and their pharmacological perspectives in migraine. It is proposed that the unique kinetic properties of P2X3 receptors activated by ATP offer an interesting translational value to stimulate future studies for innovative treatments of migraine pain.

Preclinical and Clinical Pharmacokinetics and Bioavailability in Healthy Volunteers of a Novel Formulation of the Selective P2X3 Receptor Antagonist Eliapixant

BACKGROUND AND OBJECTIVES

The potent, selective P2X3 receptor antagonist eliapixant (BAY 1817080) is under development for conditions characterized by neuronal hypersensitization. As prominent food effects and limited bioavailability in the fasted state were observed with immediate-release eliapixant tablets, a novel formulation was needed. Accordingly, several novel eliapixant formulations were assessed by in vitro and animal studies in a structured way. The most promising of the formulations was then investigated in a phase I study designed to assess its pharmacokinetics, food effect, and bioavailability in healthy volunteers.

METHODS

In vitro non-sink dissolution tests were performed with two amorphous solid dispersion (ASD) granule prototypes compared with pure crystalline eliapixant as a surrogate for the immediate-release formulation. Subsequently, the drug exposure of novel eliapixant formulations under fed and fasted conditions in rats and dogs was assessed to confirm improvements in bioavailability versus the suspension-based formulation. A novel Kollidon VA64®-based eliapixant formulation was identified from the preclinical studies and compared with the original tablet formulation in an open-label, partially randomized, threefold, crossover phase I study, in which healthy males received single oral doses (25-400 mg, fasted/fed). Pharmacokinetic parameters, absolute bioavailability (using an intravenous [¹³C₇¹⁵N]-eliapixant microdose), relative bioavailability (novel versus original formulation), effect of food, and adverse events (AEs) were evaluated.

RESULTS

The non-sink dissolution test demonstrated that the two ASD formulations had an improved dissolution rate compared with pure crystalline eliapixant, with a Kollidon VA64-based prototype having the highest dissolution rate. Further testing of this prototype in animal studies confirmed an approximately twofold higher bioavailability compared with the suspension-based formulation. In the phase I study, 30 subjects were randomized. With the novel Kollidon VA64® formulation (400 mg; fasted), area under the concentration-time curve (AUC) and maximum plasma concentration (C_max) were up to 3.1-fold and 1.7-fold higher, respectively, than with the original formulation (fed). AUC increased dose proportionally between 25 and 100 mg, and less than dose proportionally from 100 to 400 mg. Food had no clinically relevant effect on the novel formulation, with AUC increasing 1.3-fold and C_max 2.1-2.4-fold (time to maximum concentration was delayed by 1.5-2.25 h). Absolute bioavailability with the novel formulation (100 mg) was 50%. AEs occurred in 57% of patients; most were mild in severity.

CONCLUSIONS

The novel eliapixant formulation substantially improved bioavailability compared with immediate-release eliapixant and may be administered with/without food.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.gov: NCT03773068 (initial registration: 12 December 2018).

Determining What Represents Value in the Treatment of Refractory or Unexplained Chronic Cough from the Perspective of Key Stakeholders in Spain Using Multi-Criteria Decision Analysis

BACKGROUND AND OBJECTIVE

Chronic cough is defined as cough lasting for more than 8 weeks. It can be described as refractory when persisting despite thorough clinical assessment and treatment of any cough-related underlying condition, or unexplained when no underlying cough-related condition can be identified. Refractory or unexplained chronic cough (RCC|UCC) greatly affects patient health-related quality of life (HRQoL). Although around 10% of the population suffer from chronic cough (with 40-60% of these patients suffering from RCC|UCC), there is limited information available in the literature about the condition and the assessment of treatment success. This study aimed to determine what represents value in the treatment of RCC|UCC from the perspective of key stakeholders in Spain using Multi-Criteria Decision Analysis (MCDA) methodology.

METHODS

A literature review was conducted to adapt the MCDA framework to the specific context of RCC|UCC. A total of 24 participants were involved, representing three key stakeholder groups (7 patients, 9 physicians and 8 hospital pharmacists). The study was structured in two phases. In Phase 1, participants validated the adapted MCDA framework and assigned relative weights (100-point allocation) to the framework's value criteria/sub-criteria during three individual stakeholder meetings, one per each stakeholder group. In Phase 2, participants were brought together in a multi-stakeholder meeting to review findings of each stakeholder group, after which stakeholders repeated the weighting exercise as a collective group. All meetings included reflective discussion by participants of each value criteria/sub-criteria included within the adapted MCDA framework, where stakeholders shared their perspectives and opinions on what represents value in RCC|UCC.

RESULTS

Refractory or unexplained chronic cough is regarded as a chronic medical condition, with variable severity across patients and the potential to heavily impact their HRQoL (including physical, psychological and social/work productivity domains). Current treatments used by healthcare professionals, which have not been specifically developed and are not approved for RCC|UCC, show limited clinical effectiveness and associated safety and tolerability issues, which result in frequent treatment discontinuations. The reduction of the average cough frequency over a 24-h period is regarded as the primary goal of treatment by stakeholders, with the aim of improving HRQoL. Improvement of other cough symptoms, such as intensity, is also considered important. Minor adverse events and a slower onset of treatment effect would be acceptable to stakeholders if accompanied by strong efficacy and improvement in HRQoL. Given the inability to measure cough frequency in clinical practice, Patient-Reported Outcomes (PROs) could be considered a proxy of treatment effectiveness. A multidisciplinary approach to the condition is regarded as key for treatment success.

CONCLUSIONS

Refractory or unexplained chronic cough is a medical condition that seriously impacts patients' HRQoL. The primary goal of treatment is to improve patients' HRQoL by reducing the frequency and intensity of cough.

Mini-review: Hypertussivity and allotussivity in chronic cough endotypes

In recent years our understanding of the neurophysiological basis of cough has increased substantially. In conjunction, concepts around the drivers of chronic coughing in patients have also significantly evolved. Increasingly it is recognised that dysregulation of the neuronal pathways mediating cough play an important role in certain phenotypes of chronic cough and therefore pathological processes affecting the nervous system are likely to represent key endotypes in patients. Taking inspiration from the study of neuropathic pain, the term hypertussia has been employed to describe the phenomenon of abnormal excessive coughing in response to airway irritation and allotussia to describe coughing in response to stimuli not normally provoking cough. This review aims to summarise current clinical evidence supporting a role for the hyperexcitability of neuronal pathways contributing to chronic coughing and suggest how these might align with the clinical features observed in patients.

Chronic cough-the limitation and advances in assessment techniques

Accurate and consistent assessments of cough are essential to advance the understanding of the mechanisms of cough and individualised the management of patients. Considerable progress has been made in this work. Here we reviewed the currently available tools for subjectively and objectively measuring both cough sensitivity and severity. We also provided some opinions on the new techniques and future directions. The simple and practical Visual Analogue Scale (VAS), the Leicester Cough Questionnaire (LCQ), and the Cough Specific Quality of Life Questionnaire (CQLQ) are the most widely used self-reported questionnaires for evaluating and quantifying cough severity. The Hull Airway Reflux Questionnaire (HARQ) is a tool to elucidate the constellation of symptoms underlying the diagnosis of chronic cough. Chemical excitation tests are widely used to explore the pathophysiological mechanisms of the cough reflex, such as capsaicin, citric acid and adenosine triphosphate (ATP) challenge test. Cough frequency is an ideal primary endpoint for clinical research, but the application of cough counters has been limited in clinical practice by the high cost and reliance on aural validation. The ongoing development of cough detection technology for smartphone apps and wearable devices will hopefully simplify cough counting, thus transitioning it from niche research to a widely available clinical application.

Emerging drugs for the treatment of bladder storage dysfunction

INTRODUCTION

Current drug treatment of lower urinary tract disorders, for example, overactive bladder syndrome and lower urinary tract symptoms associated with benign prostatic hyperplasia, is moderately effective, has a low treatment persistence and some short- and long-term adverse events. Even if combination therapy with approved drugs may offer advantages in some patients, there is still a need for new agents.

AREAS COVERED

New b₃-adrenoceptor agonists, antimuscarinics, the naked Maxi-K channel gene, a novel 5HT/NA reuptake inhibitor and soluble guanylate cyclase activators are discussed. Focus is given to P2X3 receptor antagonists, small molecule blockers of TRP channels, the roles of cannabis on incontinence in patients with multiple sclerosis, and of drugs acting directly on CB1 and CB2 receptor or indirectly via endocannabinoids by inhibition of fatty acid aminohydrolase.

EXPERT OPINION

New potential alternatives to currently used drugs/drug principles are emerging, but further clinical testing is required before they can be evaluated as therapeutic alternatives. It seems that for the near future individualized treatment with approved drugs and their combinations will be the prevailing therapeutic approach.

ATP, an attractive target for the treatment of refractory chronic cough

Chronic cough is the most common complaint in respiratory clinics. Most of them have identifiable causes and some may respond to common disease-modifying therapies. However, there are many patients whose cough lacks effective aetiologically targeted treatments or remains unexplained after thorough assessments, which have been described as refractory chronic cough. Current treatments for refractory chronic cough are limited and often accompanied by intolerable side effects such as sedation. In recent years, various in-depth researches into the pathogenesis of chronic cough have led to an explosion in the development of drugs for the treatment of refractory chronic cough. There has been considerable progress in the underlying mechanisms of chronic cough targeting ATP, and ongoing or completed clinical studies have confirmed the promising antitussive efficacy of P2X3 antagonists for refractory cough. Herein, we review the foundation on which ATP target was developed as potential antitussive medications and provide an update on current clinical progresses.

Platelets and the Role of P2X Receptors in Nociception, Pain, Neuronal Toxicity and Thromboinflammation

P2X receptors belong to a family of cation channel proteins, which respond to extracellular adenosine 5'-triphosphate (ATP). These receptors have gained increasing attention in basic and translational research, as they are central to a variety of important pathophysiological processes such as the modulation of cardiovascular physiology, mediation of nociception, platelet and macrophage activation, or neuronal-glial integration. While P2X1 receptor activation is long known to drive platelet aggregation, P2X7 receptor antagonists have recently been reported to inhibit platelet activation. Considering the role of both P2X receptors and platelet-mediated inflammation in neuronal diseases such as multiple sclerosis, Alzheimer's disease, Parkinson's disease, and stroke, targeting purinergic receptors may provide a valuable novel therapeutic approach in these diseases. Therefore, the present review illuminates the role of platelets and purinergic signaling in these neurological conditions to evaluate potential translational implications.

Risk Factors for Persistent Chronic Cough During Consecutive Years: A Retrospective Database Analysis

BACKGROUND

The identification of patients at high risk for diseases provides clinicians essential information to better manage such patients. Persistent chronic cough (PCC) is a condition with high clinical burden and limited knowledge of the risk factors that drive the persistent symptoms.

OBJECTIVE

To understand the risk factors of PCC in patients with CC diagnosed by specialists.

METHODS

In this retrospective study, adults aged 18 to 85 years diagnosed with CC by a pulmonologist, allergist, otolaryngologist, or gastroenterologist in the period 2011 to 2016 were identified. PCC was defined by another CC code or at least 2 cough events at least 8 weeks but no more than 4 months apart in each of the 2 consecutive years beginning 1 year after the original CC diagnosis. Unadjusted and adjusted risk ratios with 95% CI for patient characteristics at baseline in relationship to PCC were estimated by Poisson regression models with robust error variance.

RESULTS

Of the adults with CC, 3270 (27.4%) had PCC and 5302 (44.5%) did not have CC during follow-up; 3341 (28.1%) had CC in only 1 follow-up year and were excluded from the analysis. Compared with patients without PCC, patients with PCC were noted to have significantly increased adjusted risk ratios for the following baseline features: (1) demographic characteristics (elderly, females, and less educated); (2) comorbidities (chronic obstructive pulmonary disease, chronic sinusitis, bronchiectasis, pulmonary fibrosis, hypertension, depression, and cough complications); (3) medication dispensed (inhaled corticosteroids/long-acting beta-agonists, leukotriene modifiers, nasal corticosteroids, nasal short-acting muscarinic antagonists, proton pump inhibitors, antitussives with narcotics, and neuromodulators); and (4) specialist care, particularly with pulmonologists.

CONCLUSIONS

Knowledge of the independent risk factors associated with PCC should aid clinicians in identifying such patients and improve their management.

Safety, Pharmacodynamics, and Pharmacokinetics of P2X3 Receptor Antagonist Eliapixant (BAY 1817080) in Healthy Subjects: Double-Blind Randomized Study

Background and Objective

There is no licensed treatment for refractory chronic cough; off-label therapies have limited efficacy and can produce adverse effects. Excessive adenosine triphosphate signaling via P2X3 receptors is implicated in refractory chronic cough, and selective P2X3 receptor antagonists such as eliapixant (BAY 1817080) are under investigation. The objective of the study was to investigate the safety and tolerability of ascending repeated oral doses of eliapixant in healthy volunteers.

Methods

We conducted a repeated-dose, double-blind, randomized, placebo-controlled study in 47 healthy male individuals. Subjects received repeated twice-daily ascending oral doses of eliapixant (10, 50, 200, and 750 mg) or placebo for 2 weeks. The primary outcome was frequency and severity of adverse events. Other outcomes included pharmacokinetics and evaluation of taste disturbances, which have occurred with the less selective P2X3 receptor antagonist gefapixant.

Results

Peak plasma concentrations of eliapixant were reached 3–4 h after administration of the first and subsequent doses. With multiple dosing, steady-state plasma concentrations were reached after ~ 6 days, and plasma concentrations predicted to achieve ≥ 80% P2X3 receptor occupancy (the level required for efficacy) were reached at 200 and 750 mg. Increases in plasma concentrations with increasing doses were less than dose proportional. After multiple dosing, mean plasma concentrations of eliapixant showed low peak–trough fluctuations and were similar for 200- and 750-mg doses. Eliapixant was well tolerated with a low incidence of taste-related adverse events.

Conclusions

Eliapixant (200 and 750 mg) produced plasma concentrations that cover the predicted therapeutic threshold over 24 h, with good safety and tolerability. These results enabled eliapixant to progress to clinical trials in patients with refractory chronic cough.

Clinical Trial Registration

Clinicaltrials.gov: NCT03310645 (initial registration: 16 October, 2017).

Supplementary Information

The online version contains supplementary material available at 10.1007/s40262-022-01126-1.

There are few effective treatments for patients with a long-term (chronic) cough. It is thought that chronic cough is caused by nerves becoming oversensitive, wrongly causing a cough when there is no need. We tested a new drug called eliapixant in 47 healthy men. Eliapixant reduces the excessive nerve signaling responsible for chronic cough. We looked for side effects of eliapixant and measured how it behaves in the body. In particular we looked for side effects relating to the sense of taste because gefapixant, a similar drug to eliapixant, can affect taste. Participants took one of four eliapixant doses or a placebo twice daily for 2 weeks. The highest levels of eliapixant in the blood were seen 3–4 h after taking the drug, and stable concentrations were seen after about 6 days. At the two highest doses, eliapixant reached concentrations in the body that should be high enough to work in patients with chronic cough. Side effects were generally similar between eliapixant and placebo. Taste-related side effects were mild and went away without needing treatment. The positive results of this study meant that eliapixant could be tested in patients with chronic cough.

Discovery of 5-methyl-1H-benzo[d]imidazole derivatives as novel P2X3 Receptor antagonists

Drug discovery programs targeting P2X3 receptors (P2X3R), an extracellular adenosine 5'-triphosphate (ATP) gated cation channel family, have been actively investigated for several CNS-related diseases. The current unmet need in the field of P2X3R targeted drugs is to avoid a side effect, the loss of taste, that could be reduced by increase of the P2X3R selectivity vs P2X2/3R. In this study, 5-methyl-1H-benzo[d]imidazole derivatives were designed and synthesized from the analysis of key pharmacophores of current antagonists. In the structure-activity relationship study, the most potent compounds 17a-b was discovered as potent P2X3R antagonists with IC₅₀ values of 145 and 206 nM, and selectivity index of 60 and 41, respectively. In addition, 17a-b showed the not-competitive antagonism, but poor binding score in the docking study at the known allosteric binding site of Gefapixant binding site, indicating that another allosteric binding site might be existing for the novel P2X3R antagonists.

Purinergic receptors modulators: An emerging pharmacological tool for disease management

Purinergic signaling is mediated through extracellular nucleotides (adenosine 5'-triphosphate, uridine-5'-triphosphate, adenosine diphosphate, uridine-5'-diphosphate, and adenosine) that serve as signaling molecules. In the early 1990s, purines and pyrimidine receptors were cloned and characterized drawing the attention of scientists toward this aspect of cellular signaling. This signaling pathway is comprised of four subtypes of adenosine receptors (P1), eight subtypes of G-coupled protein receptors (P2YRs), and seven subtypes of ligand-gated ionotropic receptors (P2XRs). In current studies, the pathophysiology and therapeutic potentials of these receptors have been focused on. Various ligands, modulating the functions of purinergic receptors, are in current clinical practices for the treatment of various neurodegenerative disorders and cardiovascular diseases. Moreover, several purinergic receptors ligands are in advanced phases of clinical trials as a remedy for depression, epilepsy, autism, osteoporosis, atherosclerosis, myocardial infarction, diabetes, irritable bowel syndrome, and cancers. In the present study, agonists and antagonists of purinergic receptors have been summarized that may serve as pharmacological tools for drug design and development.

Impact of mental health and personality traits on the incidence of chronic cough in the Canadian Longitudinal Study on Aging

Background

Chronic cough is a common troublesome condition, but risk factors for developing chronic cough are poorly understood. The aim of this study was to understand the relationship between mental health disorders, personality traits and chronic cough.

Methods

The Canadian Longitudinal Study on Aging is a prospective, nationally generalisable, random sample of adults aged 45–85 years at baseline recruited between 2011 and 2015, and followed-up 3 years later. Chronic cough was defined as a daily cough over the last 12 months. Incident chronic cough was defined as those participants who reported new-onset chronic cough between baseline and follow-up 1. Current depressive symptoms and psychological distress were assessed using the Center for Epidemiologic Study Short Depression Scale (CESD-10) and Kessler Psychological Distress Scale (K-10), respectively. The “Big Five” personality traits were assessed using the Ten-Item Personality Inventory. Relative risks are reported using a multivariate mutually adjusted model.

Results

At follow-up 1, 2506 participants (11.1%) reported new-onset chronic cough during the ∼3-year interval. Depressive symptoms (CESD-10 ≥10: relative risk 1.22 (95% CI 1.03–1.44)) and psychological distress (K-10 ≥22: relative risk 1.20 (95% CI 1.07–1.36)) at baseline were both independent predictors of a higher risk of incident chronic cough. Prevalent and incident chronic cough were also independently associated with an increased risk of developing depressive symptoms and psychological distress. Personality traits did not influence the development of chronic cough but did increase the risk of depressive symptoms and psychological distress.

Conclusions

This study shows that there is a bidirectional relationship between chronic cough, and depressive symptoms and psychological distress, and personality traits do not independently influence the development of chronic cough.

Efficacy and safety of gefapixant, a P2X3 receptor antagonist, in refractory chronic cough and unexplained chronic cough (COUGH-1 and COUGH-2): results from two double-blind, randomised, parallel-group, placebo-controlled, phase 3 trials

BACKGROUND

Gefapixant is an oral P2X₃ receptor antagonist that has previously shown efficacy and safety in refractory chronic cough and unexplained chronic cough. We therefore aim to confirm the efficacy and safety of gefapixant in participants with refractory chronic cough and unexplained chronic cough.

METHODS

COUGH-1 and COUGH-2 were both double-blind, randomised, parallel-group, placebo-controlled, phase 3 trials. COUGH-1 was done in 156 sites in 17 countries and COUGH-2 in 175 sites in 20 countries. We enrolled participants who were 18 years or older with a diagnosis of refractory chronic cough or unexplained chronic cough of 1 year duration or more. Participants were also required to have a cough severity visual analogue scale score of 40 mm or more at screening and baseline. Eligible participants were randomly allocated (1:1:1), using a computer-generated allocation schedule, to one of three treatment groups: placebo, gefapixant 15 mg twice per day, or gefapixant 45 mg twice per day. All study treatments were given orally. Participants were treated over a 12-week main study period in COUGH-1 and a 24-week main study period in COUGH-2; followed by extension periods for a total of up to 52 weeks of treatment in both trials. The primary outcome was placebo-adjusted mean change in 24-h cough frequency at 12 weeks in COUGH-1 and 24 weeks in COUGH-2. Both studies were registered with ClinicalTrials.gov, NCT03449134 (COUGH-1) and NCT03449147 (COUGH-2).

FINDINGS

From March 14, 2018, (first participant screened) to July 26, 2019, (last participant screened) 732 patients were recruited in COUGH-1 and 1317 in COUGH-2. COUGH-1 randomly assigned and treated 730 participants (243 [33×3%] with placebo, 244 [33×4%] with gefapixant 15 mg twice per day, and 243 [33×3%] with gefapixant 45 mg twice per day); COUGH-2 randomly assigned and treated 1314 participants (435 [33×1%] with placebo, 440 [33×5%] with gefapixant 15 mg twice per day, and 439 [33×4%] with gefapixant 45 mg twice per day). Participants were mostly female (542 [74×2%] of 730 in COUGH-1 and 984 [74×9%] of 1314 in COUGH-2). The mean age was 59×0 years (SD 12×6) in COUGH-1 and 58×1 years (12×1) in COUGH-2, and the mean cough duration was 11·6 years (SD 9·5) in COUGH-1 and 11·2 years (9·8) in COUGH-2. Gefapixant 45 mg twice per day showed significant reductions in 24-h cough frequency compared with placebo at week 12 in COUGH-1 (18·5% [95% CI 32·9-0·9]; p=0·041) and at week 24 in COUGH-2 (14·6% [26·1-1·4]; p=0·031). Gefapixant 15 mg twice per day did not show a significant reduction in cough frequency versus placebo in both studies. The most common adverse events were related to taste disturbance: ageusia (36 [4·9%] of 730 in COUGH-1 and 86 [6·5%] of 1314 in COUGH-2), dysgeusia (118 [16·2%] in COUGH-1 and 277 [21·1%] in COUGH-2), hypergeusia (3 [0·4%] in COUGH-1 and 6 [0×5%] in COUGH-2), hypogeusia (19 [2·6%] in COUGH-1 and 80 [6·1%] in COUGH-2), and taste disorder (28 [3·8%] in COUGH-1 and 46 [3·5%] in COUGH-2).

INTERPRETATION

Gefapixant 45 mg twice per day is the first treatment to show efficacy with an acceptable safety profile in phase 3 clinical trials for refractory chronic cough or unexplained chronic cough.

FUNDING

Merck Sharp & Dohme.