The Phase 2 RELIEF (A Randomized, Double-Blind, Placebo-Controlled, Crossover, Dose Escalation Study of BLU-5937 in Subjects with Unexplained or Refractory Chronic Cough) trial assessed the efficacy, safety, and tolerability of BLU-5937 in patients with refractory chronic cough. As the largest crossover design trial in refractory chronic cough, RELIEF enrolled a total of 68 patients from 16 sites in the United Kingdom and United States, with 52 completing both treatment periods. BLU-5937 did not achieve statistical significance for the primary endpoint of reduction in placebo-adjusted awake cough frequency at any dose tested. However, pre-specified subgroup analyses of patients with ≥20 c/hr and ≥32 c/hr demonstrated statistically significant and clinically meaningful reductions in placebo-adjusted awake cough frequency. BLU-5937 was safe and well tolerated, and taste effects were uncommon at all dose levels (6.5%, 9.8%, 10% and 8.6% at 25mg BID, 50mg BID, 100mg BID and 200mg BID, respectively, versus 4.9% on placebo).