Fraser Claudia Rose, Ajenjo Javier, Veal Mathew, Dias Gemma Marie, Chan Chung, O'Neill Edward, Destro Gianluca, Lau Doreen, Pacelli Anna, Gouverneur Veronique, Hueting Rebekka, Cornelissen Bart
Department of Oncology, MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford, OX3 7DQ, UK.
Department of Chemistry, University of Oxford, Oxford, UK.
EJNMMI Res. 2022 Aug 13;12(1):50. doi: 10.1186/s13550-022-00920-z.
Ataxia telangiectasia mutated (ATM) is a key mediator of the DNA damage response, and several ATM inhibitors (ATMi) are currently undergoing early phase clinical trials for the treatment of cancer. A radiolabelled ATMi to determine drug pharmacokinetics could assist patient selection in a move towards more personalised medicine. The aim of this study was to synthesise and investigate the first F-labelled ATM inhibitor [F]1 for non-invasive imaging of ATM protein and ATMi pharmacokinetics.
Radiofluorination of a confirmed selective ATM inhibitor (1) was achieved through substitution of a nitro-precursor with [F]fluoride. Uptake of [F]1 was assessed in vitro in H1299 lung cancer cells stably transfected with shRNA to reduce expression of ATM. Blocking studies using several non-radioactive ATM inhibitors assessed binding specificity to ATM. In vivo biodistribution studies were performed in wild-type and ATM-knockout C57BL/6 mice using PET/CT and ex vivo analysis. Uptake of [F]1 in H1299 tumour xenografts was assessed in BALB/c nu/nu mice.
Nitro-precursor 2 was synthesised with an overall yield of 12%. Radiofluorination of 2 achieved radiochemically pure [F]1 in 80 ± 13 min with a radiochemical yield of 20 ± 13% (decay-corrected) and molar activities up to 79.5 GBq/μmol (n = 11). In vitro, cell-associated activity of [F]1 increased over 1 h, and retention of [F]1 dropped to 50% over 2 h. [F]1 uptake did not correlate with ATM expression, but could be reduced significantly with an excess of known ATM inhibitors, demonstrating specific binding of [F]1 to ATM. In vivo, fast hepatobiliary clearance was observed with tumour uptake ranging 0.13-0.90%ID/g after 1 h.
Here, we report the first radiofluorination of an ATM inhibitor and its in vitro and in vivo biological evaluations, revealing the benefits but also some limitations of F-labelled ATM inhibitors.
共济失调毛细血管扩张症突变基因（ATM）是DNA损伤反应的关键介质，目前有几种ATM抑制剂（ATMi）正处于治疗癌症的早期临床试验阶段。一种用于确定药物药代动力学的放射性标记ATMi有助于朝着更个性化医疗的方向进行患者选择。本研究的目的是合成并研究首个用于ATM蛋白无创成像和ATMi药代动力学研究的F标记的ATM抑制剂[F]1。
通过用[F]氟化物取代硝基前体实现对已确认的选择性ATM抑制剂（1）进行放射性氟化。在稳定转染shRNA以降低ATM表达的H1299肺癌细胞中体外评估[F]1的摄取。使用几种非放射性ATM抑制剂进行阻断研究，评估其与ATM的结合特异性。使用PET/CT和离体分析在野生型和ATM基因敲除的C57BL/6小鼠中进行体内生物分布研究。在BALB/c裸鼠中评估[F]1在H1299肿瘤异种移植中的摄取。
合成的硝基前体2的总产率为12%。2的放射性氟化在80±13分钟内获得放射化学纯的[F]1，放射化学产率为20±13%（衰变校正），摩尔活度高达79.5 GBq/μmol（n = 11）。在体外，[F]1的细胞相关活性在1小时内增加，而[F]1的保留率在2小时内降至50%。[F]1的摄取与ATM表达无关，但用过量的已知ATM抑制剂可使其显著降低，表明[F]1与ATM特异性结合。在体内，观察到快速的肝胆清除，1小时后肿瘤摄取范围为0.13 - 0.90%ID/g。
在此，我们报告了首个ATM抑制剂的放射性氟化及其体外和体内生物学评估，揭示了F标记的ATM抑制剂的益处和一些局限性。
