AbstractTo harness radiometals in clinical settings, a chelator forming a stable complex with the metal of interest and targets the desired pathological site is needed. Toward this goal, we previously reported a unique set of chelators that can stably bind to both large and small metal ions, via a conformational switch. Within this chelator class, py‐macrodipa is particularly promising based on its ability to stably bind several medicinally valuable radiometals including large 132/135La3+, 213Bi3+, and small 44Sc3+. Here, we report a 10‐step organic synthesis of its bifunctional analogue py‐macrodipa‐NCS, which contains an amine‐reactive −NCS group that is amenable for bioconjugation reactions to targeting vectors. The hydrolytic stability of py‐macordipa‐NCS was assessed, revealing a half‐life of 6.0 d in pH 9.0 aqueous buffer. This bifunctional chelator was then conjugated to a prostate‐specific membrane antigen (PSMA)‐binding moiety, yielding the bioconjugate py‐macrodipa‐PSMA, which was subsequently radiolabeled with large 132/135La3+ and small 47Sc3+, revealing efficient and quantitative complex formation. The resulting radiocomplexes were injected into mice bearing both PSMA‐expressing and PSMA‐non‐expressing tumor xenografts to determine their biodistribution patterns, revealing delivery of both 132/135La3+ and 47Sc3+ to PSMA+ tumor sites. However, partial radiometal dissociation was observed, suggesting that py‐macrodipa‐PSMA needs further structural optimization.
摘要为了在临床中利用放射性金属,需要一种螯合剂与相关金属形成稳定的复合物,并靶向所需的病理部位。为了实现这一目标,我们以前曾报道过一组独特的螯合剂,它们能通过构象转换与大小金属离子稳定结合。在这一螯合剂类别中,py-macrodipa 尤其有前景,因为它能稳定地结合几种有药用价值的放射性金属,包括大的 132/135La3+、213Bi3+ 和小的 44Sc3+。在此,我们报告了一种经过 10 个步骤有机合成的双功能类似物 py-macrodipa-NCS,该类似物含有一个与胺反应的 -NCS 基团,适合与靶向载体进行生物共轭反应。对 py-macordipa-NCS 的水解稳定性进行了评估,结果显示其在 pH 值为 9.0 的水缓冲液中的半衰期为 6.0 d。然后将这种双功能螯合剂与前列腺特异性膜抗原(PSMA)结合分子共轭,得到生物轭合物 py-macrodipa-PSMA,随后用大的 132/135La3+ 和小的 47Sc3+ 对其进行放射性标记,结果表明复合物的形成高效且定量。将得到的放射性复合物注射到携带表达 PSMA 和不表达 PSMA 的肿瘤异种移植物的小鼠体内,以确定它们的生物分布模式,结果显示 132/135La3+ 和 47Sc3+ 都被输送到 PSMA+ 肿瘤部位。然而,观察到部分放射性金属解离,这表明py-macrodipa-PSMA需要进一步的结构优化。