目的:成纤维细胞活化蛋白是肿瘤诊断和治疗中最有吸引力的靶点之一。有许多成功的临床翻译与小分子和肽,然而,只有少数抗FAP抗体诊断或治疗药物被报道.抗体通常具有良好的肿瘤选择性和长期的肿瘤滞留,这可能与治疗性放射性核素更好地匹配(例如,177Lu,225Ac)用于癌症治疗。在这里,我们报告了177Lu标记的抗FAP抗体,PKU525,作为FAP靶向放射治疗的治疗性放射性药物。
方法:抗FAP抗体作为西布妥珠单抗的衍生物产生。用89Zr标记的抗体通过PET成像进行药代动力学和阻断研究。已经通过177Lu标记用SPECT成像筛选和测试了缀合策略。在携带HT-1080-FAP肿瘤的NU/NU小鼠中对177Lu标记的抗FAP抗体进行生物分布和放射疗法研究。
结果:多时间点PET成像研究表明,[89Zr]Zr-DFO-PKU525的肿瘤积聚强烈,选择性,相对较快。时间活动曲线表明肿瘤摄取持续增加,直到192h时达到最高摄取(SUVmax=18.4±2.3,n=4),然后逐渐下降。放射性从血液中迅速清除,肝脏,和其他主要器官,导致高肿瘤背景比。体内阻断实验表明[89Zr]Zr-DFO-PKU525是FAP特异性的,并且在FAP阴性肿瘤中的摄取几乎可以忽略不计。离体生物分布研究表明,[177Lu]Lu-DOTA-NCS-PKU525的肿瘤摄取为23.04±5.11%ID/g,33.2±6.36%内径/g,24h时,内径19.87±6.84%/g,内径19.02±5.90%/g,96小时,168小时,注射后240小时(n=5),PET成像证实了这一点。在治疗分析中,[177Lu]Lu-DOTA-NCS-PKU525的多剂量已在荷瘤小鼠中进行了测试,并且数据表明3.7MBq可能足以完全抑制小鼠的肿瘤生长而不显示可观察到的副作用。
结论:开发了FAP靶向抗体-放射性核素缀合物,并在体外和体内进行了评估。它的肿瘤积累是快速和高与干净的背景。它显著抑制了小鼠的肿瘤,而副作用几乎可以忽略不计,表明它有希望进一步的临床转化研究。
Fibroblast activation protein is one of the most attractive targets for tumor diagnosis and therapy. There have been many successful clinical translations with small molecules and peptides, yet only a few anti-FAP antibody diagnostic or therapeutic agents have been reported. Antibodies often feature good tumor selectivity and long tumor retention, which may be a better-match with therapeutic radionuclides (e.g.,177Lu, 225Ac) for cancer therapy. Here we report a 177Lu-labeled anti-FAP antibody, PKU525, as a therapeutic radiopharmaceutical for FAP-targeted radiotherapy.
The anti-FAP antibody is produced as a derivative of sibrotuzumab. The pharmacokinetics and blocking study are performed with 89Zr-labeled antibody by PET imaging. The conjugation strategies have been screened and tested with SPECT imaging through 177Lu-labeling. The biodistribution and radiotherapy studies are performed on 177Lu-labeled anti-FAP antibody in NU/NU mice-bearing HT-1080-FAP tumors.
A multiple time-point PET imaging study shows that the tumor accumulation of [89Zr]Zr-DFO-PKU525 is intense, selective, and relatively rapid. The time activity curve indicates that the tumor uptake continually increases until reaches the highest uptake (SUVmax = 18.4 ± 2.3, n = 4) at 192 h, then gradually declines. Radioactivity rapidly cleared from the blood, liver, and other major organs, resulting in high tumor-to-background ratios. An in vivo blocking experiment suggests that [89Zr]Zr-DFO-PKU525 is FAP-specific and the uptake in FAP-negative tumors is almost negligible. Ex vivo biodistribution study shows that the tumor uptake of [177Lu]Lu-DOTA-NCS-PKU525 is 23.04 ± 5.11% ID/g, 33.2 ± 6.36% ID/g, 19.87 ± 6.84% ID/g and 19.02 ± 5.90% ID/g at 24 h, 96 h, 168 h, and 240 h after injection (n = 5), which is corroborated with the PET imaging. In therapeutic assays, multiple doses of [177Lu]Lu-DOTA-NCS-PKU525 have been tested in tumor-bearing mice, and the data suggests that 3.7 MBq may be sufficient to completely suppress the tumor growth in mice without showing observable side effects.
A FAP-targeted antibody-radionuclide conjugate was developed and evaluated in vitro and in vivo. Its tumor accumulation is rapid and high with a clean background. It remarkably suppresses the tumors in mice while the side effect is almost negligible, showing that it is promising for further clinical translational studies.