Synthesis and pharmacological evaluation of 99mTc-labeled imidazolyl-containing diphosphonic acid as a novel bone imaging agent.

In order to develop a superior bone imaging agent, a new radiotracer (99m)Tc-1-hydroxy-5-(2-butyl-1H-imidazol-1-yl)pentane-1,1-diyldiphosphonic acid (BIPeDP) was designed and prepared with good radiochemical yield and stability. The biodistribution in mice shows that (99m)Tc-BIPeDP has high specificity in the skeleton with the maximum uptake of 17.30 ± 0.14 injected dose per gram at 60 min. Kinetics of blood clearance shows that the distribution half-life (T1/2α) and elimination half-life (T1/2β) of (99m)Tc-BIPeDP are 3.7 and 49.7 min, respectively. An excellent image can be obtained at 1-h post-injection with the single photon emission computed tomography bone scanning, which is clearer and quicker than (99m)Tc-zoledronic acid, (99m)Tc-1-hydroxy-5-(1H-imidazol-1-yl)pentane-1,1-diyldiphosphonic acid, and (99m)Tc-methylenediphosphonic acid All results indicate that (99m)Tc-BIPeDP holds great potential as a novel promising bone imaging agent.