Background: The efficacy of P2X3 antagonists in refractory/unexplained chronic cough (RUCC) implicates a role for extracellular ATP (eATP), which in the airways is tightly regulated by ectonucleotidases (ENTPDs). The role of ENTPDs in RUCC have not been investigated.
Aim: We aimed to compare levels of CD39L1 ?an ENTPD which preferentially hydrolyses ATP? in RUCC and healthy volunteers (HV), and correlate these with objective and subjective cough measures.

Methods: Adult RUCC/HV had 24h-hour cough monitoring, cough measures (LCQ/VAS), blood and bronchoalveolar lavage (BAL) sampling. CD39L1 was assessed by ELISA (Assay Genie, Ireland).

Results: RUCC (n=22) median (IQR) age was higher vs HV (n=14) [59(55?65) vs 33(25?44)yrs], but sex, BMI, lung function and blood eosinophils were comparable. In RUCC, CD39L1 levels were higher in BAL but there was a trend to be lower in plasma compared with HV. BAL CD39L1 levels tended to correlate with worse objective and subjective cough measures (Fig1).

Conclusions: These data suggest eATP breakdown in RUCC is dysregulated and are consistent with our measurements of airway and plasma eATP. Enhanced CD39L1 in the airway may be a response to increased ATP release in RUCC patients but this requires further investigation.