New treatment offers hope for people suffering with chronic cough

Henrietta Strickland
February 28, 2020

Millions suffering from a chronic cough could have their debilitating symptoms relieved by a new treatment, according to a study.

The treatment promises to be a godsend to the 10 per cent of the British population who suffer from chronic coughs.

Gefapixant, a P2X3 agonist that blocks a receptor involved in the cough reflex, has been found in previous studies that reduces the frequency of cough when given at a high dose (600 mg, twice daily) for two weeks. Non-smokers with a chronic cough are likely to have an underlying condition such as asthma, or to have been exposed to dust or fumes in the workplace.

Long-lasting coughs can indicate a number of health problems, including chronic obstructive pulmonary disease, which affects millions of people in the United Kingdom, or even cancer.

Gefapixant is able to target P2X3receptors in the nerves which control coughing and the team monitored the impact of the drug using a special cough monitoring device they developed which counts coughs. Because large placebo effects have been seen in other randomized, placebo-controlled cough treatment studies, the authors took this into account by analyzing cough frequency relative to placebo.

In this 12-week trial, a new drug Gefapixant was tested at 50 mg dose, explained Jacky Smith, Professor of Respiratory Medicine at The University of Manchester.

The trial was funded by the research arm of the NHS and drug maker Afferent Pharmaceuticals - which is owned by pharmaceutical giant Merck. All had suffered from an unexplained or untreatable cough that had lasted for an average of nearly 15 years.

The most common side effect was the change in the sense of taste of the patients, which was observed in previous trials with the drug. During the 12 week trial, the team of researchers looked at 253 patients, and results showed that there was significant efficacy of the drug at 50 mg dose. Almost two-thirds of the patients showed a clinically significant response in cases of chronic cough.

Patients treated with the two lower doses of the drug experienced more profound cough reduction at 12 weeks than placebo-treated patients, but the difference was not statistically significant at 18.2 coughs/hour with placebo, 14.5 coughs/hour with 7.5 mg, and 12.0 coughs/hour with 20 mg. Around a quarter did not respond to the drug.

The current trial recruited adult patients with refractory chronic cough, or unexplained chronic cough, from 44 primary outpatient pulmonologist or allergist sites in the United Kingdom and U.S. All patients had chronic coughs lasting a year or longer (mean duration 14.5 years), without evidence of chest abnormality, and a score of 40 mm or more on a 100-mm cough severity visual analogue scale.

Throughout the study, patients kept a cough severity diary, including reporting how many times they coughed per hour.

This was a 16 day trial with the drug Gefapixant. Dysgeusia and other taste-related adverse experiences led to 10 patients in the 50mg group discontinuing with the study, but most patients who continued to receive treatment said they would be happy to continue for at least a year. The results revealed that even this low dose seemed to be effective in reducing the symptoms of cough among the participants.

According to Professor Smith, "This drug has exciting prospects for patients who suffer from the often distressing condition of chronic cough". They added that chronic cough could contribute to several other conditions as well, including hernias, urinary incontinence, abdominal pain, insomnia, depression, and anxiety. This was also a randomized and double-blind study.

The drug is now in two larger global phase 3 trials, meaning it could be potentially widely available within within two or three years, subject to regulatory approval.

Some unlicensed drugs have also been shown to improve chronic cough, but their use is limited by unpleasant side effects.

Dr Gabrielle Macaulay, a GP who treats hundreds of patients with coughs every year, told the BBC the new treatment could help transform the lives of those suffering.

'Billions of pounds are spent annually on over-the-counter cough and cold medicines despite a lack of evidence to support their efficacy, concerns about the potential for abuse and risk of harm in overdose'.

Before treatment started, patients coughed around 24-29 times per hour.

Professor Smith added: "We can't yet say when or if this drug will be available on prescription, however, if the phase 3 trial is successful then it would certainly be a major step towards everyday use".

Other reports by Click Lancashire

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