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

Touching a Nerve: Neuroimmune Interactions in Asthma

Asthma is an inflammatory airway disease characterized by excessive bronchoconstriction and airway hyperresponsiveness. Airway nerves play a crucial role in regulating these processes. In asthma, interactions between inflammatory cells and nerves result in nerve dysfunction, which worsens airway function. This review discusses new insights regarding the role of airway nerves in healthy lungs and examines how communication between nerves and leukocytes, including eosinophils, mast cells, dendritic cells, and innate lymphoid cells, contributes to nerve dysfunction and the worsening of airway disease. Clinical implications and therapeutic opportunities presented by neuroimmune interactions are also addressed.

Activation of Adenosine Triphosphate-Gated Purinergic 2 Receptor Channels by Transient Receptor Potential Vanilloid Subtype 4 in Cough Hypersensitivity

BACKGROUND

Transient receptor potential vanilloid subtype 4 (TRPV4) is a Ca2+-permeable non-selective cation channel that is involved in the development of cough hypersensitivity. Purinergic 2 receptors (P2X) belong to a class of adenosine triphosphate (ATP)-gated non-selective cation channels that also play an important role in cough hypersensitivity. Nevertheless, little is known about the interaction between them for cough hypersensitivity. The present study was designed to clarify the roles of TRPV4 and ATP-P2X receptors in cough hypersensitivity, and to explore the possible involvement of ATP-P2X receptors in the development of cough hypersensitivity mediated by TRPV4.

DESIGN AND METHOD

This study aims to establish a guinea pig model of citric acid-induced enhanced cough to confirm the effects of the TRPV4-mediated purinergic signaling pathway on cough sensitivity by testing the number of coughs, the release of ATP, and the expressions of P2X and TRPV4 receptors in the tracheal carina and vagal ganglion; recording the activity of cellular currents with the whole-cell patch clamp technique; and detecting changes in intracellular calcium flow in the vagus nerve cells.

RESULTS

The number of coughs in the TRPV4 agonist GSK1016790A-treated control group was elevated compared with that in the control group, whereas the number of coughs in the TRPV4 antagonist HC067047-treated model group was significantly reduced compared with that in the chronic cough group. When the individuals in the chronic cough group were treated with A317491, PSB12062, and A804598 (P2X3,4,7 antagonists), the number of coughs was significantly decreased. This suggests that TRPV4 and P2X3, P2X4, and P2X7 receptors have an effect on cough hyper-responsiveness in guinea pigs with chronic cough. Enzyme-linked immunosorbent assay results suggested that TRPV4 antagonist and P2X3,4,7 antagonist could differentially reduce the levels of inflammatory factor SP and CGRP in alveolar lavage fluid, and TRPV4 antagonist could reduce the ATP content in the alveolar lavage fluid of guinea pigs in the model. Western blot and immunohistochemistry results showed that, in the tracheal carina and vagal ganglion, the TRPV4 and P2X3,4,7 expression was elevated in the chronic cough group compared with the control group, and could be significantly inhibited by TRPV4 antagonist. Vagus ganglion neurons were isolated, cultured, identified, and subjected to whole-cell membrane clamp assay. When ATP was given extracellularly, a significant inward current was recorded in the examined cells of individuals in the chronic cough and control groups, and the inward current induced by ATP was higher in the chronic cough group relative to the control group. This inward current (IATP) was differentially blocked by P2X3, P2X4, and P2X7 antagonists. Further studies revealed that TRPV4 agonists potentiated ATP-activated currents, and the potentiated currents could still be inhibited by P2X3, P2X4, and P2X7 receptor antagonists, whereas TRPV4 inhibitors partially blocked ATP-activated currents. It is suggested that TRPV4 affects P2X3, P2X4, and P2X7 receptor-mediated ATP-activated currents. Calcium imaging also showed that TRPV4 agonists induced different degrees of calcium inward currents in the vagal neurons of the chronic cough and the control group, and the calcium inward currents were more significant in the model group.

CONCLUSIONS

The TRPV4-mediated purinergic signaling pathway was identified to be involved in the development of cough hypersensitivity in guinea pigs with chronic cough; i.e., TRPV4 can lead to the release of airway epithelial ATP, which can stimulate P2X receptors on the cough receptor, and further activate the sensory afferent nerves in the peripheral airway, leading to increased cough sensitivity.

The McMaster Cough Severity Questionnaire (MCSQ): a cough severity instrument for patients with refractory chronic cough

BACKGROUND

Cough severity represents an important end-point to assess the impact of therapies for patients with refractory chronic cough (RCC). Our objective was to develop a new patient-reported outcome measure addressing cough severity in patients with RCC.

METHODS

Phase 1 (item generation): a systematic survey, focus groups and expert consultation generated 51 items. Phase 2 (item reduction): from a list of 51 items, 100 patients identified those they had experienced in the previous year and rated their importance on a 5-point scale. The McMaster Cough Severity Questionnaire (MCSQ) included items reported to occur most frequently and that had the highest importance scores. Patient feedback on the MCSQ led to elimination of redundant items. Another 100 patients completed the MCSQ, from which we performed an exploratory factor analysis and a Rasch analysis to further refine items on the MCSQ.

RESULTS

Previous publications report on the details of Phase 1. Phase 2 led to selection of 15 items from the initial 51. Patient feedback on the 15 items led to elimination of five redundant items. An exploratory factor analysis of the 10-item MCSQ led to the selection of two domains, and the elimination of one item that demonstrated cross-loading and another that had high inter-item correlations. A Rasch analysis of the 8-item MCSQ confirmed that the response options functioned in a logically progressive manner and that no items exhibited differential item functioning. The final 8-item MCSQ has a 1-week recall period and includes two domains (intensity and frequency). The 8-item MCSQ had high internal consistency (Cronbach's α=0.89), proved able to distinguish different levels of cough severity (person separation index 0.89) and demonstrated high cross-sectional convergent validity (Pearson's correlation 0.76, 95% CI 0.66-0.83) with the 100-mm cough severity visual analogue scale.

CONCLUSIONS

Initial evidence supports the validity of the MCSQ, an 8-item instrument measuring cough severity in patients with RCC. Future studies should evaluate its properties in measuring change over time.

Challenges of symptom management in interstitial lung disease: dyspnea, cough, and fatigue

INTRODUCTION

Interstitial lung disease (ILD) is a broad group of conditions characterized by fibrosis of the lung parenchyma. Idiopathic pulmonary fibrosis (IPF) is the most common subvariant. IPF is marked by considerable symptom burden of dyspnea, cough and fatigue that is often refractory to optimal disease-directed treatment.

AREAS COVERED

In this narrative review, we searched MEDLINE for articles related to the current evidence regarding management of chronic dyspnea, cough, and fatigue as three of the most prevalent and distressing symptoms associated with IPF and other ILDs. Each symptom shares common features of multi-factorial etiology and a lack of safe and effective pharmacological therapies. Both corticosteroids and opioids have been utilized in this context, yet there is insufficient evidence of therapeutic benefit and considerable risk of harms. Whilst some may benefit from symptom-directed pharmacological management, usage must be carefully monitored. Use of non-pharmacological strategies, such as breathing techniques and speech therapy represent low risk and low-cost option, yet broader validation of these therapies' effectiveness is needed.

EXPERT OPINION

Symptom management in IPF and other ILDs requires an iterative and individualized approach. Leveraging the expertise of multidisciplinary teams within an integrated care setting is an important opportunity to maximize health outcomes.

Laryngeal Vibrotactile Stimulation Is Feasible, Acceptable To People With Unexplained Chronic Cough

OBJECTIVES

Unexplained chronic cough (UCC) is common and has significant impacts on quality of life. Ongoing cough can sensitize the larynx, increasing the urge to cough and perpetuating the cycle of chronic cough. Vibrotactile stimulation (VTS) of the larynx is a noninvasive stimulation technique that can modulate laryngeal somatosensory and motor activity. Study objectives were to assess feasibility and acceptability of VTS use by people with UCC. Secondarily, changes in cough-related quality of life measures were assessed.

METHODS

Adults with UCC recorded cough measures at baseline and after completing 2 weeks of daily VTS. Feasibility and acceptability were assessed through participant-reported device use and structured feedback. Cough-related quality of life measures were the Leicester Cough Questionnaire (LCQ) and the Newcastle Laryngeal Hypersensitivity Questionnaire (NLHQ).

RESULTS

Nineteen adults participated, with mean age 67 years and cough duration 130 months. Notably, 93% of planned VTS sessions were logged, 94% of participants found the device comfortable to wear, 89% found it easy to operate and 79% would recommend it to others. Pre-post LCQ change achieved a minimal important difference (MID) (mean 1.3 [SD 2.4, p = 0.015]). NLHQ scores improved, but did not reach an MID.

CONCLUSIONS

Laryngeal VTS use was feasible and acceptable for use by patients with UCC and was associated with a meaningful improvement in cough-related quality of life. Future studies will include VTS dose refinement and the inclusion of a comparison arm to further assess the potential for laryngeal VTS as a novel treatment modality for UCC.

LEVEL OF EVIDENCE

4 Laryngoscope, 134:5010-5014, 2024.

Benefit-Risk Profile of P2X3 Receptor Antagonists for Treatment of Chronic Cough: Dose-Response Model-Based Network Meta-Analysis

BACKGROUND

Refractory or unexplained chronic cough disrupts quality of life and burdens health care systems around the world. The P2X3 receptor antagonist gefapixant is approved in many countries for its antitussive effects, but taste disturbances are a common adverse effect. Four newer, more selective P2X3 receptor antagonists have been developed to address this problem.

RESEARCH QUESTION

How does the benefit-risk profile vary across the five available P2X3 receptor antagonists?

STUDY DESIGN AND METHODS

A systematic review and network meta-analysis was conducted to evaluate the efficacy of P2X3 receptor antagonists, including gefapixant, sivopixant, eliapixant, camlipixant, and filapixant. Primary outcomes were a reduction rate in 24-hour cough frequency and incidence of taste disturbance. Dose-response curves and median effective dose (ED50) were calculated. Effect size at ED50 was ranked according to the surface under the cumulative ranking curve. The confidence was evaluated by Confidence In Network Meta-Analysis.

RESULTS

Sixteen randomized controlled trials involving 4,904 participants were analyzed. The gefapixant regimen demonstrated an ED50 of 90.7 mg/d for cough frequency reduction. Gefapixant showed the highest antitussive effectiveness at ED50 (reduction rate in 24-hour cough frequency: median, 28.1%; 95% credible interval [CrI], 21.0%-35.6%; ranked 1 of 5; moderate certainty) but the highest prevalence of taste disturbance (absolute risk difference per 100 patients: median, 38; 95% CrI, 27-51; ranked 5 of 5; high certainty) and the highest prevalence of discontinuation. Camlipixant had a well-balanced profile (reduction rate in 24-hour cough frequency: median, 14.7%; 95% CrI, 5.4%-26.0%; ranked 3 of 5; low certainty; and taste disturbance; absolute risk difference per 100 patients; median, 2; 95% CrI, 1-6; ranked 2 of 5; low certainty). Placebo had a mean of 33.1% reduction in 24-hour cough frequency.

INTERPRETATION

When used at safe doses, gefapixant had a favorable risk-benefit profile compared with the other four agents. Camlipixant showed initial promise, which may be further investigated by phase III trials currently underway.

CLINICAL TRIAL REGISTRATION

University Hospital Medical Information Network Center (UMIN-CTR); No. UMIN000050622; URL: https://center6.umin.ac.jp.

The discovery and development of gefapixant as a novel antitussive therapy

INTRODUCTION

Gefapixant, a P2X 3 receptor antagonist, shows considerable potential in managing refractory or unexplained chronic cough. Clinical trials have consistently demonstrated its efficacy in significantly reducing cough frequency and alleviating associated symptoms. However, its adverse effect profile, particularly taste disturbances such as dysgeusia and hypogeusia, the incidence of which is dose-dependent, poses a significant challenge to patient compliance and overall treatment satisfaction.

AREAS COVERED

The authors review the mechanism of action of gefapixant, the dose-dependent nature of its adverse effects and the findings from various clinical trials, including Phase 1, Phase 2, and Phase 3 studies. The authors also cover its regulatory status, post-marketing data, and its main competitors.

EXPERT OPINION

Gefapixant represents a significant advancement in treating chronic cough. However, balancing efficacy and tolerability is crucial. Lower effective doses and potential combination therapies may mitigate taste disturbances. Patient education and close monitoring during treatment are also important for optimal outcomes. Further research is needed to refine dosing strategies to minimize side effects while maintaining therapeutic efficacy. This research and personalized treatment approaches are key to optimizing gefapixant therapy, ensuring improved management of chronic cough while reducing adverse effects. However, pharmaceutical trials and proposals must be adapted to align with each regulatory body's specific requirements and concerns.

Reporting quality of meta-analyses in acupuncture: Investigating adherence to the PRISMA statement

Although Systematic Reviews and Meta-Analyses (PRISMA) and Preferred Reporting Items for Systematic Reviews and Meta-Analyses for Acupuncture (PRISMA-A) checklists had been in use for several years, compliance rate was still not optimistic. We investigated the quality of reporting for meta-analyses of acupuncture published in PubMed. We compared the compliance rate for the quality of reporting following the publication of both the PRISMA and PRISMA-A recommendations. We searched PubMed for articles published between January 1st, 2020 and December 31st, 2022, after Endnote X9 document management software and manual screening, 180 meta-analyses of acupuncture were selected as samples. The PRISMA, and PRISMA-A checklists were used to evaluate the quality of the literature. Data were collected using a standard form. Pearson χ2 test and/or Fisher exact test were used to assess differences in reporting among groups. Logistic regression is used to calculate OR and its 95% CI. The total reported compliance rate of all items in the PRISMA list was 61.3%, and the reported compliance rate of the items with a compliance rate of <50% accounted for 35.71% of the total items. The total reported coincidence rate of all items in the PRISMA-A was 56.9%, and the reported coincidence rate of the items with a reported coincidence rate of <50% accounted for 31.25% of all the items. The compliance rate of the published research to PRISMA or PRISMA-A has no statistical difference between the Journal Citation Reports partition (Quarter1-Quarter2) and Journal Citation Reports partition (Quarter3-Qurater4) (P > .05). Regardless of the level of journals published, have obvious deficiencies in the details of the study, the reference basis for the design of the study, the analysis method, the degree of strictness, the scientific nature, and other aspects. We must strengthen education on the standardization of research reports.

Patient satisfaction with the management of refractory and unexplained chronic cough in Canada: Results from a national survey

BACKGROUND

Chronic cough (persisting for ≥8 weeks) is a common disorder affecting approximately 5 to 10% of adults worldwide that is sometimes refractory to treatment (refractory chronic cough [RCC]) or has no identifiable cause (unexplained chronic cough [UCC]). There is minimal information on the patient's experience of RCC/UCC in Canada. The aim of this study was to evaluate the patient journey and perceptions related to RCC/UCC management in Canada.

METHODS

Our exploratory study included Canadians in the Leger Opinion Panel and focused on individuals with RCC or UCC. Key entry criteria were: age ≥18 years, cough on most days for ≥8 weeks, no smoking within 1 year, no serious respiratory disease or lung cancer, and not taking angiotensin-converting enzyme inhibitors. Individuals who met entry criteria were invited to complete an approximately 30-minute online survey with questions on demographic characteristics, healthcare professional (HCP) interactions, diagnosis of underlying conditions, current treatments, and satisfaction with HCPs and chronic cough therapies.

RESULTS

A total of 49,076 individuals completed the chronic cough screening questionnaire (July 30, 2021 to September 1, 2021): 1,620 (3.3%) met entry criteria for RCC or UCC, and 1,046 (2.1%) completed the online survey (mean age of 45 years, 61% female). Most respondents (58%) reported their chronic cough was managed by a general practitioner (GP). Forty-four percent of respondents did not have a diagnosis of an underlying condition for their cough. Breathing tests (39%) and chest imaging (34%) were the most common diagnostic tests. Cough suppressants (18%) were the most frequent current treatment. Respondents were moderately satisfied with their HCPs, but more than half considered their treatment ineffective and 34% had considered no longer seeking medical attention because of a lack of treatment success.

CONCLUSIONS

Individuals with RCC/UCC in Canada are largely unsatisfied with the effectiveness of treatment. Additional HCP education and new treatment options are needed to improve patient satisfaction.

Prevalence and causes of chronic cough in Japan

BACKGROUND

Chronic cough is one of the most common symptoms of respiratory diseases and can adversely affect patients' quality of life and interfere with social activities, resulting in a significant social burden. A survey is required to elucidate the frequency and treatment effect of chronic cough. However, clinical studies that cover all of Japan have not yet been conducted.

METHODS

Patients who presented with a cough that lasted longer than 8 weeks and visited the respiratory clinics or hospitals affiliated with the Japan Cough Society during the 2-year study period were registered.

RESULTS

A total of 379 patients were enrolled, and those who did not meet the definition of chronic cough were excluded. A total of 334 patients were analyzed: 201 patients had a single cause, and 113 patients had two or more causes. The main causative diseases were cough variant asthma in 92 patients, sinobronchial syndrome (SBS) in 36 patients, atopic cough in 31 patients, and gastroesophageal reflux (GER)-associated cough in 10 patients. The time required to treat undiagnosed patients and those with SBS was significantly longer and the treatment success rate for GER-associated cough was considerably poor.

CONCLUSIONS

We confirmed that the main causes of chronic cough were cough variant asthma, SBS, atopic cough, and their complications. We also showed that complicated GER-associated cough was more likely to become refractory. This is the first nationwide study in Japan of the causes and treatment effects of chronic cough.

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.

Importance of well-designed meta-analyses in assessing medical and surgical treatments

When evaluating the efficacy of medical or surgical treatments, the most robust study design is often considered to be the high-quality randomized clinical trial (RCT). However, the true answer lies in the meta-analysis of high-quality RCTs. While RCTs have their merits, meta-analyses possess two crucial qualities that make them superior: Generalizability and the ability to verify replicability across different trials. A well-designed meta-analysis, defined here as a systematic review that pools data, holds significant advantages over individual RCTs. Retrospective and observational surgical research is prone to biases that are not mutually offsetting; instead, they accumulate. Selection bias, transfer bias, and assessment bias all taint retrospective studies more than randomized trials, making the novel treatment appear more effective than it truly is. Pooling studies suffering from these limitations in a meta-analysis amplifies these biases, causing an overestimation of treatment benefits. This becomes particularly concerning when the treatment itself carries substantial risks, as is often the case in surgical journals. The consequences can result in harm or even death for patients. While a well-designed meta-analysis is the best tool for assessing medical and surgical treatments, a weak meta-analysis amplifies biases and promotes flawed data. Thoughtful readers must become proficient in honing their methodological toolkits, delving deeper into topics like heterogeneity and publication bias. It is essential to avoid wasting time on meta-analyses drawing data from retrospective or observational research regarding surgical treatments.

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.