A32-42 Patient Insights on Experience With Metered-dose Inhalers Using Novel Low-carbon Propellant HFA-152a Compared With the Current Propellant HFA-134a

Rationale

Salbutamol metered-dose inhalers (MDIs) are currently formulated with the propellant hydrofluoroalkane (HFA)-134a. HFA-134a has a global warming potential (GWP) 1530 times that of CO2 and is being phased down under the Kigali Amendment,1 with accelerated implementation under European F-gas legislation. A new salbutamol MDI with next-generation propellant HFA-152a, in clinical development, is expected to reduce carbon emissions by > 90%.2 When MDIs transitioned from chlorofluorocarbon to HFA propellants in the early 2000s, differences in taste and feel hampered a seamless patient transition.3 This study assessed patients’ experience comparing HFA-152a and HFA-134a MDI formulations using sensory discrimination and subjective experience tests.

Methods

This study was a randomized, participant-blinded, two-part crossover study in participants with asthma, aged 18-79 years. After inhaler technique training, the first part (three-way crossover) triangle discrimination test (ISO 4120:2021) involved participants self-administering inhalations from three placebo MDIs in randomized order; two contained one propellant and one contained the alternative. Participants were asked to identify the unique inhaler and rate confidence in their decision on a 7-point Likert scale (1=“not at all confident”-7=“very confident”). The second part (two-way crossover) subjective experience assessment involved participants self-administering inhalations from two placebo MDIs containing either HFA-152a or HFA-134a, and completing 7-point Likert ratings for sensory attributes including taste aspects (1=“not at all”-7=“extremely”) and general inhalation experiences/acceptability (1=“strongly disagree”-7=“strongly agree”).

Results

Of the 42 participants included, 19 (45.2%) correctly and 23 (54.8%) incorrectly identified the unique inhaler. 95% confidence intervals for the observed correct identification proportion (30.2-60.3%) included the proportion expected by chance (33.3%), indicating no significant discrimination between propellants (Figure). Most participants (84% correct; 74% incorrect) reported high confidence in their identification (confidence ratings 5-7; overall mean scores: 5.6 and 5.3, respectively). For both inhalers, sensory ratings were generally positive for taste (76% [HFA-152a] and 48% [HFA-134a] rated “not at all bad”) and acceptability (86% and 67% rated willingness to use as “agree/strongly agree”, respectively).

Conclusions

This study demonstrated that participants were unable to identify differences between HFA-152a and HFA-134a reliably. Positive sensory and inhalation experiences were reported for both propellants. Findings support efforts to facilitate a seamless patient transition to the low-GWP MDI with propellant HFA-152a in clinical development, following approval.

References:

1. Greenhouse Gas Protocol. IPCC Global Warming Potential Values 2024. Available from: https://ghgprotocol.org/sites/default/files/2024-08/Global-Warming-Potential-Values%20%28August%202024%29.pdf [accessed January 2026]

2. King J, et al. Allergy. 2025:1-9

3. Hendeles L, et al. N Engl J Med. 2007;356:1344-51

This abstract is funded by: GSK (ID: 223737)