Synthesis and evaluation of a series of 99mTc-labelled zoledronic acid derivatives as potential bone seeking agents

Developing novel superior bone-seeking radiopharmaceuticals for the detection of malignant bone lesions could further improve the diagnostic value of routine bone scanning. A series of radiolabeled diphosphonates (^99mTc-EIPrDP, ^99mTc-EIBDP and ^99mTc-EIPeDP) have been designed and synthesized successfully in high chemical yields and radiochemical purity. The in vitro and in vivo biological properties were systematically investigated and compared. The biodistribution in mice shows that ^99mTc-EIPrDP has higher bone uptake (13.3 ± 1.23) than those of ^99mTc-EIBDP and ^99mTc-EIPeDP (11.7 ± 0.28 and 8.69 ± 0.04 %ID/g) at 1–2 h post injection. It also has the highest uptake ratio of bone to muscle, spleen and heart, respectively, and faster blood clearance in early times. The present study indicates that ^99mTc-EIPrDP holds great promise as a bone imaging agent.