Thanks PP. Here is a little blurb on oral & time delivery of IGF-1 from:
Therapeutic Peptides and Proteins:
Formulation, Processing, and Delivery
Systems, Second Edition
by Ajay K. Banga
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Delivery of insulin-like growth factor I (IGF-I) to rat and minipig colonic mucosae under in vitro conditions has been investigated. IGF-I is a 7649-Da protein of 70 amino acids that exerts its biological actions through specific IGF-I receptors. It has been found useful to lower blood glucose levels in insulin-resistant diabetic patients in clinical studies. IGF-I was absorbed intact across rat colonic mucosa as determined by reverse-phase high-performance liquid chromatography (RP-HPLC), sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE), and Western blotting.48
A time-based drug release system for colon-specific delivery has also been developed. This system exploits the relatively constant small intestine transit time of dosage forms.49 Time-based systems can be designed to release their drug after a predetermined lag time, with the lag time independent of normal physiological conditions such as pH, digestive state of the subject, and anatomical position at the time of release.50,51
48. Quadros, E., Landzert, N. M., LeRoy, S., Gasparani, F., and Worosila, G. Colonic absorption of insulin-like growth factor I in vitro. Pharm. Res., 11: 226–230, 1994.
49. Gazzaniga, A., Iamartino, P., Maffione, G., and Sangalli, M. E. Oral delayed-release system for colonic specific delivery. Int. J. Pharm., 108: 77–83, 1994.
50. Pozzi, F., Furlani, P., Gazzaniga, A., Davis, S. S., and Wilding, I. R. The TIME CLOCK system: a new oral dosage form for fast and complete release of drug after a predetermined lag time. J. Controlled Release, 31: 99–108, 1994.
51. Wilding, I. R., Davis, S. S., Pozzi, F., Furlani, P., and Gazzaniga, A. Enteric coated timed release systems for colonic targeting. Int. J. Pharm., 111: 99–102, 1994.