Fluticasone propionate uptake in the presence of a proprietary cell-penetrating peptide (human stimulus factor, [HSF]) based on the N-terminal domain of lactoferrin was studied, alone and in combination with salmeterol, using an air interface Calu-3 epithelial model. The HSF enhanced uptake and transport of fluticasone propionate across the epithelial barrier when alone and in presence of salmeterol. This was attributed to transcellular-mediated uptake. This HSF is a promising peptide for delivery of therapeutics where enhanced epithelial penetrating is required.