Abstract
The beginning of the 21st century saw numerous protein and peptide therapeuticals both on the market and entering the final stages of clinical studies. They represent a new category of biologically originated drugs termed biologics or biologicals. Their main advantages over conventional drugs can be summarized by their high selectivity and potent therapeutic efficacy coupled with limited side effects. In addition, they exhibit more predictable behavior under in vivo conditions. However, up to now most of the formulations of biologics are designed and destined for the parenteral route of administration. As a consequence, many suffer from short plasma half-lives, resulting in their frequent administration and ultimately poor patient compliance. This review represents an attempt to address some of the challenges and promises in the product development of biologics both for parenteral and noninvasive administration. Some of the products currently in the pipeline of pharmaceutical development and corresponding perspectives are discussed in more detail.