Abstract 4599: Preclinical evaluation, and clinical translation of 68Ga/177Lu-JH04, a novel FAP-targeting radiolabeled agent

Abstract Introduction: Fibroblast activation protein (FAP) is an ideal target for tumor imaging and therapy. To enhance tumor uptake and prolong the retention of FAP-targeting agents, we developed JH04, a novel cyclic peptide composed of a FAP-targeting ligand. The objective of this study is to evaluate the specificity, biodistribution, pharmacokinetics, and dosimetry of 68Ga/177Lu-JH04 through preclinical and preliminary clinical investigations, and to compare these findings with those of 68Ga/177Lu-FAP-2286. Methods: The FAP-positive cell line HT1080-FAP was employed in in vitro and in vivo studies. The affinity of JH04 precursor to recombinant FAP protein was measured using surface plasmon resonance (SPR) and radioligand binding assays. PET imaging with 68Ga-JH04 was performed in xenograft mouse models to evaluate its in vivo specificity and preclinical pharmacokinetics. The tumor uptake and retention of 177Lu-JH04 were assessed in xenograft mice model and compared with those of 177Lu-FAP-2286. Furthermore, the biodistribution and radiation dosimetry of 68Ga-JH04 were evaluated using data from five cancer patients, with head-to-head comparisons of imaging results against those of 68Ga-FAP-2286. Lastly, the therapeutic efficacy of 177Lu-JH04 was investigated in three patients with tumor. Results: The dissociation equilibrium constant (KD) of JH04 precursor to human FAP protein was 0.428 nM. The IC50 of JH04 for human FAP protein was 3.96 nM, which was superior to that of FAP-2286 (12.2 nM). 68Ga-JH04 exhibited excellent stability both in vitro and in vivo. In cell binding studies, the uptake of 68Ga-JH04 in HT1080 cells was approximately 2.83 times higher than that of 68Ga-FAP-2286 after 30 min incubation. Small-animal PET imaging revealed that the tumor uptake of 68Ga-JH04 was approximately twice as high as that of 68Ga-FAP-2286. SPECT imaging demonstrated high tumor uptake and prolonged retention of 177Lu-JH04, the area under the curve (AUC) for tumor uptake over 168 hours was 1.94 times higher for 177Lu-JH04 compared to 177Lu-FAP-2286. In a head-to-head clinical comparison with 68Ga-FAP-2286, PET/CT imaging results revealed significantly higher tumor radiotracer uptake for 68Ga-JH04 (SUVmax: 60 minutes, 14.58 ± 6.26 vs. 11.98 ± 6.43, P = 0.025; 150 minutes, 17.46 ± 9.07 vs. 12.00 ± 7.65, P = 0.006). Additionally, the retention of 68Ga-JH04 in the kidneys and liver was 3.02 times and 3.80 times lower than that of 68Ga-FAP-2286. In a preliminary clinical evaluation of 177Lu-JH04 therapy, all three patients tolerated well. The mean effective whole-body dose of 177Lu-JH04 was determined to be 6.18E-02 ± 6.85E-03 mGy/MBq. Conclusion: 68Ga/177Lu-JH04, novel FAP-targeting agent with excellent binding affinity, high tumor uptake, prolonged retention, and robust tumor-suppressive effects. These promising results encourage us to conduct further clinical research. Citation Format: Yun Yang, Hongfei Cheng, Yuxin Lai, Xiuting Lin, Yaoming Yu, Jian Zhan, Yueguan Sun, Eric Wang, Haihua Yu, Kevin Wang, Jinqiu He, Guochang Wang, Weibing Miao. Preclinical evaluation, and clinical translation of 68Ga/177Lu-JH04, a novel FAP-targeting radiolabeled agent [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4599.