DOTA Conjugate with an Albumin-Binding Entity Enables the First Folic Acid–Targeted 177Lu-Radionuclide Tumor Therapy in Mice

Journal of Nuclear Medicine

Christian Winiger¹  Konstantin Zhernosekov¹  Harriet Struthers¹  Roger Schibli¹  Cristina Müller¹ 

关键词: albumin binder;    ¹⁷⁷Lu-cm09;    radionuclide therapy;    folate receptor;    SPECT;   

DOI  :  10.2967/jnumed.112.107235

学科分类：医学（综合）

来源: Society of Nuclear Medicine

【 摘 要 】

The folate receptor (FR) has proven a valuable target for nuclear imaging using folic acid radioconjugates. However, using folate-based radiopharmaceuticals for therapy has long been regarded as an unattainable goal because of their considerable renal accumulation. Herein, we present a novel strategy in which a DOTA–folate conjugate with an albumin-binding entity (cm09) was designed with the aim of prolonging circulation in the blood and therewith potentially improving tumor-to-kidney ratios. Methods: The folate conjugate cm09 was radiolabeled with 177LuCl3, and stability experiments were performed in plasma. Cell uptake studies were performed on FR-positive KB tumor cells, and an ultrafiltration assay was used to determine the plasma protein–binding properties of 177Lu-cm09. In vivo, 177Lu-cm09 was tested in KB tumor–bearing mice using SPECT/CT. The therapeutic anticancer effect of 177Lu-cm09 (20 MBq) applied as a single injection or as fractionated injections was investigated in different groups of mice (n = 5) by monitoring tumor size and the survival time of treated mice, compared with untreated controls. Results: Compound cm09 was radiolabeled at a specific activity of 40 MBq/nmol, a radiochemical yield of more than 98%, and a stability of more than 99% over 5 d in plasma. Ultrafiltration revealed significant binding of 177Lu-cm09 to serum proteins (∼91%) in plasma, compared with folate radioconjugate without an albumin-binding entity. Cell uptake and internalization of 177Lu-cm09 was FR-specific and comparable to other folate radioconjugates. In vivo studies resulted in high tumor uptake (17.56 percentage injected dose per gram [%ID/g] at 4 h after injection), which was almost completely retained for at least 72 h. Renal accumulation was significantly reduced (28 %ID/g at 4 h after injection), compared with folate conjugates that lack an albumin-binding entity (∼70 %ID/g at 4 h after injection). These circumstances enabled SPECT imaging of excellent quality. Radionuclide therapy (1 × 20 MBq) revealed complete remission of tumors in 4 of 5 cases and a significantly prolonged survival time, compared with untreated controls. Conclusion: The modification of a folate radioconjugate with an albumin-binding entity resulted in a significant increase of the tumor-to-kidney ratio of radioactivity, enabling for the first time, to our knowledge, the preclinical application of folic acid–targeted radionuclide therapy in mice.

【 授权许可】

Unknown