RESULTS: 416 patients were randomized into RESPIRE 1. Both primary endpoints were met in the 14d on/off arm: Ciprofloxacin DPI significantly prolonged time to 1st exacerbation vs pooled placebo (>336d vs 186d; adjusted hazard ratio [HR] 0.53; 97.5%CI 0.36-0.80; p=0.0005) and significantly reduced exacerbation frequency vs matched placebo (mean incidence rate over 48 weeks 0.78 vs 1.42; adjusted incidence rate ratio [IRR] 0.61, 97.5%CI 0.40-0.91; p=0.0061). A non-significant trend in favor of Ciprofloxacin DPI was seen for both primary endpoints in the 28d on/off regimen (time to 1st exacerbation: HR 0.73; 97.5%CI 0.50-1.07; p=0.065; frequency of exacerbations: IRR 0.98, 97.5%CI 0.64-1.48; p=0.89). Treatment-emergent (TE) AEs, serious AE (SAEs), and AEs leading to discontinuation were similar across groups. TE-AE rates (n[%]) for Ciprofloxacin DPI 14d on/off, 28d on/off, and pooled placebo respectively were 112[82.4], 110[78.0], and 114[83.2]; TE-SAE rates were 23[16.9], 28[19.9], and 32[23.4]. Occurrence of TE bronchospasm, n[%], was low and similar across groups occurring in 7[5.1], 7[5.0], and 10[7.3] patients treated with Ciprofloxacin DPI 14d on/off, 28d on/off, and placebo respectively.