FF has a highly specific, fast association and slow dissociation from the glucocorticoid receptor, with a 24 hr duration of action. This, combined with a slow transport out of respiratory cells, creates a long tissue retention period. Vilanterol trifenate (VI) is a new inhaled, selective, long - acting β2 adrenergic agonist, also with a rapid onset of action with a maximal effect within 6 mins and prolonged lung retention with effects on lung function over 24 hours. Expert commentary: Multiple Phase I-III efficacy studies performed on FF and VI have shown an improvement in spirometry as well as symptom control in asthma. The development of once daily ICS/LABA combinations may potentially improve adherence to asthma therapy, but this has yet to be demonstrated.