Novel non-invasive protein and peptide drug delivery approaches.

Protein and peptide based therapeutics are typically administered by injection due to their poor uptake when administered via enteral routes of drug administration. Unfortunately, chronic administration of these drugs through multiple injections presents certain patient related problems and it is difficult to mimic the normal physiological release patterns via this mode of drug administration. A need therefore exists to non-invasively deliver these drugs by means of alternative ways such as via the oral, pulmonary, nasal, transdermal and buccal administration routes. Although some attempts of needle free peptide and protein drug delivery have progressed to the clinical stage, relatively limited success has been achieved in terms of commercially available products. Despite the low frequency of clinical breakthroughs with noninvasive protein drug delivery this far, it remains an active research area with renewed interest not only due to its improved therapeutic potential, but also due to the attractive commercial outcomes it offers. It is the aim of this review article to reflect on the main strategies investigated to overcome the barriers against effective systemic protein drug delivery in different routes of drug administration. Approaches based on chemical modifications and pharmaceutical technologies are discussed with reference to examples of drugs and devices that have shown potential, while attempts that have failed are also briefly outlined.