Determination of the rat in vivo pharmacokinetic profile of a bone-targeting dual-action pro-drug for treatment of osteoporosis

Bioconjug Chem. 2015 Jun 17;26(6):1095-103. doi: 10.1021/acs.bioconjchem.5b00160. Epub 2015 May 15.


The in vivo hydrolytic pathway of a dual-function bone-targeting EP4 receptor agonist-bisphosphonate pro-drug was deduced from radiolabeling experiments. A (14)C labeled pro-drug was used to monitor liberation of the bisphosphonate and results were compared to parallel studies where the EP4 receptor agonist was labeled with (3)H. The bone-adsorption of the (14)C pro-drug following an IV bolus was about 10% compared to 7.8% for the tritiated pro-drug. The difference in release half-life (5.2 and 19.7 days from (3)H and (14)C experiments, respectively) indicated that, after binding to bone, the initial hydrolysis occurred at the ester moiety of the linker releasing the EP4 agonist. The conjugate was found to concentrate in more porous, high-surface-area regions of the long bones. Both (3)H and (14)C experiments indicated a short circulating half-life (1-2 h) in blood.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bone Density Conservation Agents / chemistry
  • Bone Density Conservation Agents / pharmacokinetics*
  • Bone and Bones / metabolism
  • Diphosphonates / chemistry
  • Diphosphonates / pharmacokinetics*
  • Female
  • Half-Life
  • Osteoporosis / drug therapy*
  • Prodrugs / chemistry
  • Prodrugs / pharmacokinetics*
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Prostaglandin E, EP4 Subtype / agonists*


  • Bone Density Conservation Agents
  • Diphosphonates
  • Prodrugs
  • Ptger4 protein, rat
  • Receptors, Prostaglandin E, EP4 Subtype