TRPA1 and asthma: However, as clinical trials in the last 20 years with NK1/NK2 receptor antagonists have shown little efficacy in asthma [23], [24], and, with no reported therapeutic role so far reported by the use of NK1/NK2 receptor antagonists in COPD, it seems unlikely that SP/NKA released from sensory nerves are the sole and the major contributors of TRPA1-mediated inflammation in the airways.