Therapeutic peptides

Delivery of peptides and proteins via the gastrointestinal tract has not been successful because of poor penetration through the intestinal epithelium and high levels of proteolytic activity in the gastrointestinal tract. Liposomal encapsulation of proteins and peptides will not improve the efficiency and capacity of this absorption pathway considerably (e.g., Ryman et al., 1982 Machy and Leserman, 1987 Weiner and Chia-Ming Chiang, 1988). These difficulties in delivery via the oral route caused the parenteral route to remain the preferred route for the administration of therapeutic peptides... 

Fig. 13 Left. ELP carrier N-terminally fused to a cell-penetrating peptide and C-terminally fused to a therapeutic peptide. Right Amino acid sequences for several cell-penetrating peptides (see text for details). Reprinted from [83] with permission from Elsevier, cop)mght 2010...

A. L. Adjei and P. K. Gupta, Inhalation Delivery of Therapeutic Peptides and Proteins, Marcel Dekker, New York, 1997. 

Bioavailability and bioequivalence are also usually assessed in animals. Such studies are undertaken as part of pharmacokinetic and/or pharmacodynamic studies. Bioavailability relates to the proportion of a drug that actually reaches its site of action after administration. As most biopharmaceuticals are delivered parenterally (e.g. by injection), their bioavailability is virtually 100 per cent. On the other hand, administration of biopharmaceuticals by mouth would, in most instances, yield a bioavailability at or near 0 per cent. Bioavailability studies would be rendered more complex if, for example, a therapeutic peptide was being administered intranasally. 

Agu RU, Vu Dang H, Jorissen M, Willems T, Kinget R, Verbeke N (2002) Nasal absorption enhancement strategies for therapeutic peptides an in vitro study using cultured human nasal epithelium. Int J Pharm 237 179-191. 

The 3-(2-hydroxy-4,6-dimethylphenyl)-3-methylbutanoic acid shown in Fig. 8.23, as well as another phenylpropanoic derivative presented below, have been used as pro-moieties to prepare a number of prodrugs of therapeutic peptides [169] [238], Of interest here is that the pro-moiety is linked to the peptide by both amide and ester bonds to form a cyclic, double prodrug, the two-step activation of which is schematized in Fig. 8.24. Briefly, enzymatic hydrolysis of the ester bond unmasks a nucleophile (in this case, a phenol) that carries out an intramolecular attack on the amide bond, resulting in cy-clization of the pro-moiety and elimination of the peptide. [Leu5]enkephalin was one of the therapeutic peptides used to validate the concept, as illustrated in Fig. 8.25 [241],... 

Janssen EM. van Oosterhout AJ, van Rensen AJ. van Eden W. Nijkamp FP. Wauben MH Modulation of Th2 responses by peptide analogues in a murine model of allergic asthma amelioration or deterioration of the disease process depends on the Thl or Th2 skewing characteristics of the therapeutic peptide. J Immunol 2000 164 580-588. 

Sanz-Nebot, V., Benavente, R., Balaguer, E., and Barbosa, J. (2003). Capillary electrophoresis coupled to time of flight-mass spectrometry of therapeutic peptide hormones. Electrophoresis 24, 883-891. 

The order of elution of peptides (charged compounds) is governed by a combination of electrophoresis and partitioning, with hydrophobic as well as electrostatic contributions. In this study it was demonstrated that sulfonic acid functionalities in the methacrylate monolith provide high stability and maintain a constant EOF over a wide range of pH (2—12). It was also demonstrated that a better separation of a mixture of therapeutic peptides was obtained at high pH values (Figure 16) due to the suppression of electrostatic attraction. 

Stephanie Mouhat is an engineer and has a Ph.D. in biology. She is affiliated to the ERT 62 laboratory and holds a position as a researcher in a biopharmaceutical company. She works in the field of therapeutic peptides derived from venomous animal toxins, and has contributed to more than 10 scientific articles, above 20 communications, and 2 patents in the field. She won the prize for the best Ph.D. thesis at the Universite de la Mediterranee in 2006. 

Ludovic Mouhat is an engineer in bioinformatics. He is affiliated to the ERT 62 laboratory and holds a position as a researcher in a biopharmaceutical company. He is involved in the design and chemical production of candidate therapeutic peptide drugs. 

Jean-Marc Sabatier has a Ph.D. and HDR in biochemistry. He is the director of research at the French Centre National de la Recherche Scientifique (CNRS). He heads a research laboratory (ERT 62) entided Engineering of Therapeutic Peptides at the Universite de la Mediterranee, in Marseilles, France. He also holds the position of a senior director (discovery research — peptides) for a public company in Canada. Dr. Sabatier works in the field of animal toxins, and leads the venom peptide group of the International Neuropeptide Society. He also designs immunomodulatory and antiviral drugs, as well as contributes to the field of peptide and protein engineering. He has contributed more than 100 scientific articles, 180 communications, and 43 patents. He is a member of several scientific advisory boards of journals (e.g.. Peptides, Biochemical Journal), and has reviewed articles submitted for publication in more than 30 specialized international journals. 

Muranishi, S., and Takada, K., Biopharmaceutieal aspeets on enhanced transmembrane delivery of peptides and proteins. In Therapeutic Peptides and Proteins Formulation, Delivery, and Targeting (D. Marshak and D. Liu, eds.), Cold Spring Harbor Laboratory, New York, 1989, pp. 47-50. 

Bernkop-Schnurch, A., The use of inhibitory agents to overcome the enzymatic barrier to perorally administered therapeutic peptides and proteins, J. Control. Rel., 52 1-16 (1998). 

Biological activity is the most important concern with the delivery of therapeutic peptides and proteins. Suseeptibility of these molecules to denaturation by various manufaeturing processes may seriously limit the methods that can be employed in the fabrieation of delivery systems. Important process variables such as temperature, pressure, exposure to organie solvents, etc., during manufacturing need to be considered. 

Recent years have witnessed an explosive growth in the imderstanding of the mechanisms associated with the absorption of drugs, especially therapeutic peptides and proteins. Scientists from a variety of disciplines continue to elucidate the variables associated with the optimal formulation and delivery of drugs via the oral mucosa. A greater rmderstanding of the para- and transcellular route of drug absorption, pro-... 

Dry powder inhalers have initially found their application in inhalation therapy as a CFC-free alternative for the older MDIs. However, nowadays they seem to have a much larger potential [14,53], because of the high lung deposition that can be attained and also because they are suitable for the pulmonary delivery of therapeutic peptides and proteins [2,10,16]. 

These adsorbants are based on immobilised ligands, which have a high affinity for a particular analyte (Fig. 15.13). There are examples where antibodies have been raised to an analyte and then bound to the surface of a SPE matrix. Various types of chemistry permit this type of immobilisation and affinity chromatography is well established in biochemistry. With the proliferation with biotechnological products such as therapeutic peptides, the use of these types of columns for extraction may increase since they can be designed to be highly selective for such compounds. 

Banga, A.K. (1995). Therapeutic Peptides and Proteins Formulation, Processing and Delivery Systems. Technomic, Lancaster, PA. 

Irngartinger, M., Camuglia, V., Damm, M., Goede, J., and Frijlink, H. W. (2004) Pulmonary delivery of therapeutic peptides via dry powder inhalation Effects of micronisation and manufacturing). 

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