Placing nebulizers within a HFT circuit upstream from the humidification chamber may enable to deliver clinically relevant masses of aerosol at the cannula outlet, but more importantly downstream of the nose and pharynx, even in case of high patients' inspiratory flow. This method of aerosol therapy is expected to produce a bronchodilatatory effect to be evaluated in the clinical settings.

Overall, the inhalation of mAbs for therapeutic purposes is both appropriate and feasible. The size and structure of the biotherapeutic molecule are important properties to be taken into account when trying to achieve long-term retention. Mesh nebulizers currently appear to be the most appropriate devices for the safe delivery of large amounts of active mAb into the lungs. mAbs should be formulated so as to prevent their degradation and possible immunogenicity. General guidelines can be given for mAb aerosolization, but the formulation and device combination should be adapted for each therapeutic and clinical application.

Drug delivery in the airways by inhalation can be used for local and/or systemic action, depending on the ability of the aerosolized drug to cross the air-blood barrier. For proteins, this is partly conditioned by the drug's molecular weight, as well as aerosol characteristics. This editorial focuses on protein inhalation for topical delivery purposes. Even though systemic applications (such as insulin inhalation) are not considered herein, it is worth noting that systemic diffusion following topical delivery may happen in some cases, and provide therapeutic benefit (as is the case for granulocyte-macrophage colony-stimulating factor (GM-CSF)).