title: Improved intrapulmonary delivery of site-specific PEGylated salmon calcitonin: optimization by PEG size selection.
abstract: The purpose of this study was to demonstrate the biological potentials of PEGylated salmon calcitonin (PEG-sCT) derivatives administered intratracheally and their dependences on PEG Mw (1, 2, 5 kDa). Initially, three different PEG-sCT derivatives were site-specifically synthesized by attaching PEG to the Lys(18)-amine. In an attempt to examine the pulmonary feasibilities of these derivatives, the following evaluations were undertaken to determine their; (i) proteolytic resistances to pulmonary enzymes, (ii) bioactivities, and (iii) pulmonary pharmacokinetic and pharmacologic profiles. The results obtained showed that the pulmonary stabilities and pharmacokinetic properties of these derivatives were greatly improved by increasing PEG Mw. PEG-sCTs had 10.5-, 40.1-, and 1066.0-fold greater stabilities than that of sCT in rat lung homogenates. Moreover, all pharmacokinetic parameters (AUC(inf), C(max), t(1/2), and others) of these derivatives in endotracheally cannulated rats were significantly improved by PEGylation. Specifically, C(max) values increased on increasing PEG Mw, i.e., 78.1+/-21.1, 102.9+/-9.1, and 115.2+/-5.7 for 1, 2, 5 kDa, respectively, vs. 54.8+/-3.9 ng/mL for sCT. Their circulating t(1/2) values also increased to 53.9+/-6.0, 100.7+/-21.7, and 119.4+/-13.7 min, respectively, vs. 34.6+/-7.6 min for sCT. Despite having the best properties, Lys(18)-PEG(5k)-sCT was found to have significantly lower hypocalcemic efficacy than other PEG-sCTs, probably due to its reduced intrinsic bioactivity ( approximately 30% vs. sCT). Rather, Lys(18)-PEG(2k)-sCT showed the most promising pulmonary potential because of its well-preserved bioactivity (>80% of sCT). Taken together, our findings suggest that the site-specific substitution to peptides like sCT with a PEG of an appropriate size offers optimized therapeutic potential by dual advantages, i.e., (i) increased proteolytic stability and (ii) extended circulating half-life in terms of intrapulmonary delivery.
authors.affiliation: College of Pharmacy, Pusan National University, Jangjun-dong, Geumjeong-gu, Busan 609-735, Korea.
authors.forename: Yu Seok
authors.initials: YS
authors.lastname: Youn
authors.forename: Min Jung
authors.initials: MJ
authors.lastname: Kwon
authors.forename: Dong Hee
authors.initials: DH
authors.lastname: Na
authors.forename: Su Young
authors.initials: SY
authors.lastname: Chae
authors.forename: Seulki
authors.initials: S
authors.lastname: Lee
authors.forename: Kang Choon
authors.initials: KC
authors.lastname: Lee
mesh_terms: D000280:Administration, Inhalation; D000818:Animals; D001682:Biological Availability; D050071:Bone Density Conservation Agents / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics; D002116:Calcitonin / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics; D002118:Calcium / Q000097:blood; D045744:Cell Line, Tumor; D000242:Cyclic AMP / Q000378:metabolism; D004337:Drug Carriers / Q000737:chemistry*; D004355:Drug Stability; D006801:Humans; D008168:Lung / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D015394:Molecular Structure; D008970:Molecular Weight; D011092:Polyethylene Glycols / Q000737:chemistry*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D050071:Bone Density Conservation Agents; D004337:Drug Carriers; D011092:Polyethylene Glycols; C028815:salmon calcitonin; D002116:Calcitonin; D000242:Cyclic AMP; D002118:Calcium