Mucociliary Clearance Following a Next-Generation Propellant Versus Hydrofluoroalkane-134a via Pressurized Metered-Dose Inhaler: A Randomized, Double-Blind, Two-Way Crossover Study in Healthy Adults

Background: Pressurized metered-dose inhalers (pMDIs) are commonly used for respiratory disease treatment but contain propellants, such as hydrofluoroalkane-134a (HFA-134a), with global warming potential (GWP) that contribute to the climate emergency. To safeguard essential medicine access, it is crucial to transition to lower-GWP propellants, such as hydrofluoroolefin-1234ze (HFO-1234ze), which has 99% lower GWP than HFA-134a. In accordance with global regulatory requirements, this study was conducted to support the registration of pMDIs with HFO-1234ze. Methods: This randomized, double-blind, multicenter, two-way crossover study assessed the effects of HFO-1234ze versus HFA-134a on mucociliary clearance (MCC) in healthy participants aged 18–60 years. Participants received six inhalations twice daily of HFO-1234ze and HFA-134a in two 7-day (+3) intervention periods separated by a 7- to 14-day washout. The primary and secondary endpoints were change from period-specific baseline in average whole lung MCC (%) through 60 minutes (MCC60) and at 3 hours (MCC3h), respectively, measured via inhalation of 99m Tc-labeled colloid and gamma camera imaging. Given significant baseline variability, a post hoc analysis of the primary endpoint assessed change from average baseline instead of period-specific baseline MCC60. Additional safety and tolerability measures were assessed. Results: Forty-five participants were screened; the Primary Analysis Set included 34 participants who completed both intervention periods. For the primary endpoint, change from period-specific baseline in MCC60 was negligible, with an estimated change (95% confidence interval [CI]) of −0.6% (−3.2%, 1.9%) for HFO-1234ze and 0.8% (−1.7%, 3.3%) for HFA-134a. The estimated least-squares mean difference (95% CI) between HFO-1234ze and HFA-134a was −1.4% (−5.8%, 2.9%). For the secondary endpoint, the estimated least-squares mean difference for change from period-specific baseline in MCC3h between HFO-1234ze and HFA-134a was −5.7% (−10.9%, −0.5%). There were no unexpected safety findings. Conclusion: There was no clinically relevant impact of HFO-1234ze versus HFA-134a on MCC in healthy participants. Clinical trial registration number: NCT05755932.