ABSTRACT
The rapid growth of recombinant biotechnology over the last 20 years has resulted in about 75 protein-and peptide-based drugs available on the market for treatment and more than a 100 in late-phase clinical trials (1). The market for these therapeutic proteins was estimated in 2001 to be $27 billion (2). Global sales of genetically engineered protein drugs were $10.7 billion in 1995 (3) and are forecast to be around $59 billion in 2010 (2). Further, the antibody therapeutics market is expected to reach $7 billion in 2004 (4). In spite of the high demand for protein-based drugs, their processing and delivery remains a challenge. Proteins are easily denatured by the low pH and enzymes present in the gastric environment and, hence, cannot be administered using traditional oral delivery systems. Presently, protein-based drugs are almost exclusively delivered via injectable systems, which suffer from poor delivery efficiencies and low patient compliance. Hence, there is a strong market-driven push toward the development of alternative drug delivery techniques for proteins, including inhaled and controlled or sustained release systems. Further, as increasing applications are found for DNA, RNA, and nucleic acid fragments in gene therapy (5, 6) and as vaccines (7), development of novel efficient methods to deliver them are becoming critical.
