Synthesis, characterization and in vivo activity of salmon calcitonin coconjugated with lipid and polyethylene glycol

✍ Scribed by Weiqiang Cheng; Lee-Yong Lim

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 471 KB
• Volume: 98
• Category: Article
• ISSN: 0022-3549
• DOI: 10.1002/jps.21524

✦ Synopsis

An irreversible lipidized salmon calcitonin (sCT) analog, Mal-sCT, was previously shown to have comparable hypocalcemic activity to sCT in vivo. This study reports on the synthesis, characterization and pharmacological activity of novel PEGylated Mal-sCT analogs. Mal-sCT, prepared by conjugating sCT via thio-ether bonds with aqueous-soluble palmitic acid derivative at Cys 1 and Cys 7, was reacted with mPEGsuccinimide (mPEG-Suc, 5 kDa). The products were purified and then identified by MALDI-TOF MS and HPLC. Mal-sCT was conjugated with 1 (1PEG-Mal-sCT) or 2 (2PEG-Mal-sCT) PEG chains at Lys 11 and Lys 18, the former being the preferred site of conjugation at higher mPEG-Suc/Mal-sCT ratio. Circular dichroism analysis showed the PEGylated Mal-sCT analogs to possess a robust helical conformation, while size measurement by dynamic light scattering indicated a propensity of the peptides to self-aggregate in aqueous solutions. Both 1PEG-Mal-sCT and 2PEG-Mal-sCT were more stable in rodent intestinal fluids than sCT or Mal-sCT. However, 1PEG-Mal-sCT had comparable hypocalcemic activity to Mal-sCT when injected subcutaneously in the rat, while 2PEG-Mal-sCT was inactive. 1PEG-Mal-sCT was inactive when administered orally in the rat. This study suggested PEGylation of Mal-sCT increased the stability of the lipidized peptide to enzyme degradation, but did not enhance its hypocalcemic activity.