Particle engineering technologies for improving the delivery of peptide and protein drugs

Proteins and peptides are excellent therapeutic compounds which have highly specific and potent biological functions. However, the efficacious and safe delivery of peptide and protein drugs remains a major challenge due to a number of factors such as i) their intrinsic physicochemical instability, ii) their poor permeability through biological membranes, iii) their short plasma half-lives, and iv) problems with induction of immunogenicity upon repeated administration. Enabling formulation technologies are highly in demand for the successful development of various dosage forms for the effective delivery of peptide and protein drugs. Particulate delivery systems have been recognized as one of the most effective ways to improve the delivery of peptide and protein drugs. In particular, dry particle forms are very attractive because peptide and protein drugs are more stable in the solid state than in the liquid state. This review summarizes the current state of the art in particle engineering technologies enabling the formulation of peptide and protein drugs into dry particulate forms. Emphasis on the applications of spraying based technologies due to the possibility for controlling the physicochemical characteristics of the engineered particles and the potential for scaling-up for commercial scale manufacturing.