Peptide and Protein-based Approaches

The exact mechanism of protein transduction remains unclear. In the case of the Tat peptide, the sequence can be scrambled or the D-isomers of the amino acids used, which argues against a specific ligand/receptor-mediated mechanism. As yet, an elusive physical interaction of the peptide with the cell membrane is thought to permit cellular entry. However, whether the process involves endocytosis or not is also arguable, and in some experiments the cargo is spread throughout the cytoplasm, whereas in others it is concentrated 

Humanized antibodies have shown great promise, and are currently in use as successful biopharmaceuticals. Further details on the development of antibodies and their present and future success as drugs are described elsewhere in this book (see Part I, Chapter 5 Part IV, Chapter 16 Part V, Chapters 1, 2, and 6). 

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