There are an estimated 24 million people in the United States who suffer from chronic refractory cough (CRC), lasting longer than six weeks.¹  According to the 2010 National Ambulatory Medical Care Survey published by the Center for Disease Control, cough is the most frequent illness-related reason for visiting a physician in the United States accounting for approximately 31 million office visits per year. CRC is a disabling condition in which affected patients cough hundreds or even thousands of times per day, while persisting for months or years.²  Patients who develop CRC exhibit hypersensitivity of the cough response. They also have increased levels of substance P (SP) in their nasal epithelial cells and blood plasma.³  Two important mediators of the urge to scratch and the urge to cough are SP and its receptor, the neurokinin-1 receptor (NK₁-R).⁴  While pruritus and cough appear to be very different indications, their biological underpinnings are actually quite similar.

Currently available cough suppressants or antitussive agents are typically not adequate to treat CRC. There are currently no approved treatments for CRC and the evidence supporting the diagnosis and management of CRC is limited.⁵  A phase 2 clinical study is planned to evaluate the safety and efficacy of serlopitant to reduce cough frequency in patients with CRC.

1 W. J. Song et al., “The Global Epidemiology of Chronic Cough in Adults: A Systematic Review and Meta-Analysis,” Eur Respir J 45, no. 5 (2015). 

2 J. A. Smith and A. Woodcock, “Chronic Cough,” N Engl J Med 375, no. 16 (2016). 

3 R. Escamilla and N. Roche, “Cough Hypersensitivity Syndrome: Towards a New Approach to Chronic Cough,” Eur Respir J 44, no. 5 (2014). 

4 P. C. Lavinka and X. Dong, “Molecular Signaling and Targets from Itch: Lessons for Cough,” Cough 9, no. 1 (2013). 

5 P. Gibson et al., “Treatment of Unexplained Chronic Cough: Chest Guideline and Expert Panel Report,” Chest 149, no. 1 (2016).