Purpose: To develop a prostate-specific membrane antigen (PSMA)-targeted radiotherapeutic for metastatic castration-resistant prostate cancer (mCRPC) with optimized efficacy and minimized toxicity employing the β-particle radiation of 177Lu. Methods: We synthesized 14 new PSMA-targeted, 177Lu-labeled radioligands (177Lu-L1–177Lu-L14) using different chelating agents and linkers. We evaluated them in vitro using human prostate cancer PSMA(+) PC3 PIP and PSMA(−) PC3 flu cells and in corresponding flank tumor models. Efficacy and toxicity after 8 weeks were evaluated at a single administration of 111 MBq for 177Lu-L1, 177Lu-L3, 177Lu-L5 and 177Lu-PSMA-617. Efficacy of 177Lu-L1 was further investigated using different doses, and long-term toxicity was determined in healthy immunocompetent mice. Results: Radioligands were produced in high radiochemical yield and purity. Cell uptake and internalization indicated specific uptake only in PSMA(+) PC3 cells. 177Lu-L1, 177Lu-L3 and 177Lu-L5 demonstrated comparable uptake to 177Lu-PSMA-617 and 177Lu-PSMA-I&T in PSMA-expressing tumors up to 72 h post-injection. 177Lu-L1, 177Lu-L3 and 177Lu-L5 also demonstrated efficient tumor regression at 8 weeks. 177Lu-L1 enabled the highest survival rate. Necropsy studies of the treated group at 8 weeks revealed subacute damage to lacrimal glands and testes. No radiation nephropathy was observed 1 year post-treatment in healthy mice receiving 111 MBq of 177Lu-L1, most likely related to the fast renal clearance of this agent. Conclusions: 177Lu-L1 is a viable clinical candidate for radionuclide therapy of PSMA-expressing malignancies because of its high tumor-targeting ability and low off-target radiotoxic effects.
|Original language||English (US)|
|Journal||European Journal of Nuclear Medicine and Molecular Imaging|
|State||Accepted/In press - Jan 1 2019|
- Prostate cancer
- Prostate-specific membrane antigen
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging