A pair of studies have shown that chronic cough and its distressing symptoms could be eased with the help of a new drug. Also, the drug does not have side effects that can restrict its use, explain the researchers. The results of the two studies are published in The Lancet Respiratory Medicine, and the European Respiratory Journal, respectively.
The first study was titled, "Gefapixant, a P2X3 receptor antagonist, for the treatment of refractory or unexplained chronic cough in a phase 2b randomized controlled trial". The second study was titled "Gefapixant in two randomized dose-escalation studies in chronic cough".
The new drug, Gefapixant, works by targeting a receptor called the P2X3receptors in the nerves. These receptors are responsible for the cough, and when suppressed dry chronic cough with no underlying cause could be effectively treated. For these trials, the team used a cough monitoring device to see if their drug worked. Gefapixant was initially developed to be a pain killer but was later found to have a significant effect on cough.
Trials show new drug can ease symptoms of chronic cough. Image Credit: Kzenon / Shutterstock
Trial 1 in Lancet Respiratory Medicine
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. Smith, who led the study, said that this drug was developed by the pharmaceutical company MSD who had also funded this trial. The trial was a randomized, double-blinded study meaning the participants, as well as the investigators, were unaware of the drug and its dose used.
This new drug Gefapixant, Smith explained, could have a significant effect on the quality of life of thousands of sufferers of chronic cough. 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. Nearly two-thirds of the patients showed a clinically significant response in cases of chronic cough.
The team tried three different doses of the new drug Gefapixant among the participants – the first was 7.5 mg, the second 20 mg, and the third was 50 mg. The efficacy of the three doses respectively, was 52 percent, 52 percent, and 67 percent wrote the researchers. A quarter of participants in the study did not respond adequately to the drug.
Trial 2 in European Respiratory Journal
This was a 16 day trial with the drug Gefapixant. In this trial, 57 patients of chronic cough were recruited. A dose of 30 mg was tried on the patients. The results revealed that even this low dose seemed to be effective in reducing the symptoms of cough among the participants. This was also a randomized and double-blind study.
The researchers said that chronic cough affects 4 to 10 percent of the general population and could be quite distressing. These patients often cough over a thousand times in a day, and their cough may persist for years. At present, there are no definitive treatments for this form of dry and chronic cough, and most drugs available to suppress such cough are usually restricted in their use because of the side effects. Experts say the underlying causes such as asthma, chronic obstructive pulmonary disease, nasal diseases, gastroesophageal reflux disease (GERD) could contribute to chronic cough, and these problems need to be diagnosed, investigated and treated adequately. They added that chronic cough could contribute to several other conditions as well, including hernias, urinary incontinence, abdominal pain, insomnia, depression, and anxiety.
After the initial success in the two trials, the drug Gefapixant is now being further tested in two significant phase 3 trials that are to be conducted in more than one center in different countries.
Implications of the results
According to Professor Smith, "This drug has exciting prospects for patients who suffer from the often distressing condition of chronic cough. Effective treatments for cough are a significant unmet clinical need and no new therapies approved in over 50 years. 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."
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. Though it's fair to say the drug is not a cure for chronic cough, it can and often does reduce the frequency of coughing substantially. That could make a big difference to patients who often struggle with this condition, which can make such a big impact on their lives."
- Gefapixant, a P2X3 receptor antagonist, for the treatment of refractory or unexplained chronic cough: a randomised, double-blind, controlled, parallel-group, phase 2b trial Smith, Jaclyn ASmith, Jaclyn et al. The Lancet Respiratory Medicine, https://www.thelancet.com/journals/lanres/article/PIIS2213-2600(19)30471-0/fulltext
- Gefapixant in two randomised dose-escalation studies in chronic cough Jaclyn A. Smith, Michael M. Kitt, Peter Butera, Steven A. Smith, Yuping Li, Zhi Jin Xu, Kimberley Holt, Shilpi Sen, Mandel R. Sher, Anthony P. Ford European Respiratory Journal Jan 2020, 1901615; DOI: 10.1183/13993003.01615-2019, https://erj.ersjournals.com/content/early/2020/01/03/13993003.01615-2019