In the context of asthma and COPD treatment, pressurized metered dose inhaler (pMDI) products are being developed using hydrofluoroalkane (HFA)-152a, a new propellant with a significantly lower carbon footprint compared to the currently marketed HFA-134a. To replace HFA-134a with HFA-152a, equivalence in safety must be demonstrated. 

This single-dose, double-blind, randomized, 2-way crossover study was conducted to compare the bronchoconstriction potential and safety profile of single supratherapeutic doses of HFA-152a and HFA-134a in 25 mild asthmatic patients. The primary variable was the relative change from baseline (%) in forced expiratory volume in 1 second (FEV1) at 15 min post-dose, with equivalence between HFA-152a and HFA-134a demonstrated if the 95% confidence interval (CI) of the adjusted mean difference between treatments was within pre-specified limits [-10%; +10%]. As secondary variables, the relative and absolute changes from baseline in FEV1 at post-dose timepoints up to 3 hours, adverse events and vital signs were assessed.

The study met its primary endpoint; equivalence in FEV1 at 15 min post-dose was demonstrated. The 95% CI of the adjusted mean difference between treatments was within equivalence limits: 1.86% (95% CI -0.48; 4.20). Equivalence was demonstrated for all other post-dose timepoints. No bronchoconstriction and serious adverse events were reported.

HFA-152a has a reassuring and comparable safety profile to the marketed HFA-134a. This supports the seamless transition of pMDI propellants, minimizing environmental impact.