Integrin-Mediated Targeted Cancer Therapy Using c(RGDyK)-Based Conjugates of Gemcitabine.

c(RGDyK)-based conjugates of gemcitabine (GEM) with the carbonate and carbamate linkages in the 6-OH group of GEM were synthesized for the targeted delivery of GEM to integrin αvβ3, overexpressing cancer cells to increase the stability as well as the tumor delivery of GEM and minimize common side effects associated with GEM treatment. Competitive cell uptake experiments demonstrated that conjugate TC113 could be internalized by A549 cells through integrin αvβ3. Among the synthesized conjugates, TC113 bearing the carbamate linker was stable in human plasma and was further assessed in an in vivo pharmacokinetic study. TC113 appeared to be relatively stable, releasing GEM slowly into blood, while it showed potent antiproliferative properties against WM266.4 and A549 cells. The encouraging data presented in this study with respect to TC113 provide a promising keystone for further investigation of this GEM conjugate with potential future clinical applications.