Where the periphery matters: Protective excipients investigated in dry powder formulations of inhaled biomacromolecules

This article provides an overview of the considerations for the formulation development of inhaled biologics and the various excipients that are routinely investigated for use in dry powder formulations of biologics intended for oral inhalation, with particular emphasis on protein stabilization. Carbohydrates, including simple sugars, complex sugars and sugar alcohols; amino acids and surfactants are discussed.

For sensitive biologics, the choice of protein stabilizer and drying method are crucial factors affecting stability of the dehydrated biomacromolecules. Lack of toxicity data may account for the scarce options in approved inactive ingredients for the inhalation route, a gap further widened by the rigmarole of securing a marketing authorization for the excipient. Viable candidates are confined to substances biocompatible with and readily cleared from the respiratory system. With such a limited number of approved inhaled biologic products available in the market and no mAbs on this list, there is a pressing need to contemplate patient-oriented research to garner beneficial clinical and commercial outcomes.