title: Biopharmaceutical approaches for developing and assessing oral peptide delivery strategies and systems: in vitro permeability and in vivo oral absorption of salmon calcitonin (sCT).
abstract: OBJECTIVE
  To evaluate a biopharmaceutical approach for selecting formulation additives and establishing the performance specifications of an oral peptide delivery system using sCT as a model peptide.
  
  
  METHODS
  The effect of formulation additives on sCT effective permeability and transepithelial electrical resistance (TEER) was evaluated in side-by-side diffusion chambers using rat intestinal segments. Baseline regional oral absorption of sCT was evaluated in an Intestinal and Vascular Access Port (IVAP) dog model by administration directly into the duodenum, ileum, and colon by means of surgically implanted, chronic catheters. The effect of varying the input rate and volume of the administered solution on the extent of sCT absorption was also evaluated. Citric acid (CA) was utilized in all studies to cause a transient reduction in local pH. In vitro samples and plasma samples were analyzed by radioimmunoassay (RIA). Two oral delivery systems were prepared based on the results of the in vitro and IVAP studies, and evaluated in normal dogs.
  
  
  RESULTS
  Maximal permeability enhancement of sCT was observed using taurodeoxycholate (TDC) or lauroyl carnitine (LC) in vitro. Ileal absorption of sCT was higher than in other regions of the intestine. Low volume and bolus input of solution formulations was selected as the optimal condition for the IVAP studies since larger volumes or slower input rates resulted in significantly lower sCT bioavailability (BA). Much lower BA of sCT was observed when CA was not used in the formulation. The absolute oral bioavailability (mean+/-SD) in dogs for the control (sCT + CA) and two proprietary sCT delivery systems was 0.30%+/-0.05%, 1.10+/-0.18%, and 1.31+/-0.56%, respectively.
  
  
  CONCLUSIONS
  These studies demonstrate the utility of in vitro evaluation and controlled in vivo studies for developing oral peptide delivery strategies. Formulation additives were selected, the optimal intestinal region for delivery identified, and the optimal release kinetics of additives and actives from the delivery system were characterized. These methods were successfully used for devising delivery strategies and fabricating and evaluating oral sCT delivery systems in animals. Based on these studies, sCT delivery systems have been fabricated and tested in humans with favorable results.
authors.affiliation: Department of Pharmaceutics, College of Pharmacy, Rutgers-The State University of New Jersey, Piscataway 08854, USA. sinko@rci.rutgers.edu
authors.forename: P J
authors.initials: PJ
authors.lastname: Sinko
authors.forename: Y H
authors.initials: YH
authors.lastname: Lee
authors.forename: V
authors.initials: V
authors.lastname: Makhey
authors.forename: G D
authors.initials: GD
authors.lastname: Leesman
authors.forename: J P
authors.initials: JP
authors.lastname: Sutyak
authors.forename: H
authors.initials: H
authors.lastname: Yu
authors.forename: B
authors.initials: B
authors.lastname: Perry
authors.forename: C L
authors.initials: CL
authors.lastname: Smith
authors.forename: P
authors.initials: P
authors.lastname: Hu
authors.forename: E J
authors.initials: EJ
authors.lastname: Wagner
authors.forename: L M
authors.initials: LM
authors.lastname: Falzone
authors.forename: L T
authors.initials: LT
authors.lastname: McWhorter
authors.forename: J P
authors.initials: JP
authors.lastname: Gilligan
authors.forename: W
authors.initials: W
authors.lastname: Stern
mesh_terms: D000284:Administration, Oral; D000818:Animals; D002116:Calcitonin / Q000008:administration & dosage / Q000493:pharmacokinetics*; D004285:Dogs; D016503:Drug Delivery Systems; D066298:In Vitro Techniques; D007408:Intestinal Absorption / Q000187:drug effects*; D008297:Male; D010455:Peptides / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D010539:Permeability; D010592:Pharmaceutic Aids / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012474:Salmon
chemical_list: D010455:Peptides; D010592:Pharmaceutic Aids; D002116:Calcitonin