2. Academic Validation
  3. Squaric-acid-engineered FAP2286: A next-generation 68Ga/177Lu theranostic ligand with synergistically enhanced affinity, hydrophilicity, and tumor retention

Squaric-acid-engineered FAP2286: A next-generation 68Ga/177Lu theranostic ligand with synergistically enhanced affinity, hydrophilicity, and tumor retention

  • Bioorg Chem. 2025 Nov:166:109185. doi: 10.1016/j.bioorg.2025.109185.
Yuxiao Xia 1,  Jianpeng Cao 2,  Xue Jiang 1,  Wenling Tu 2,  Qian Liu 1,  Yin Huang 2,  Lina Liu 1,  Dongkun Xu 1,  Quanyu Zhou 3,  Yue Chen 4,  Yuhong Shi 5
Affiliations

Affiliations

  • 1 Department of Nuclear Medicine, The Second Affiliated Hospital of Chengdu Medical College, Chengdu, Sichuan, China; Department of Nuclear Medicine, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
  • 2 Department of Nuclear Medicine, The Second Affiliated Hospital of Chengdu Medical College, Chengdu, Sichuan, China.
  • 3 Department of Hepatobiliary and Pancreatic Surgery, Chengdu 363 Hospital Affiliated to Southwest Medical University, Chengdu, Sichuan, China.
  • 4 Department of Nuclear Medicine, Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, China. Electronic address: [email protected].
  • 5 Department of Nuclear Medicine, The Second Affiliated Hospital of Chengdu Medical College, Chengdu, Sichuan, China. Electronic address: [email protected].
PMID: 41177127 DOI: 10.1016/j.bioorg.2025.109185
Abstract

Objective: To systematically enhance the theranostic performance of the FAP-targeted ligand FAP2286 by rational chemical modification-introducing methoxy (MeO) and squaric acid (SA) substituents-followed by comparative 68Ga/177Lu radiolabeling and pre-clinical validation.

Methods: An integrated workflow combined in-silico (molecular docking, 100-ns GROMACS MD), in-vitro (IC₅₀, LogP, plasma-protein binding, radiochemical stability, cell uptake/release), and in-vivo (U87MG and HEK-293-FAP xenografts; micro-PET/CT, micro-SPECT/CT; biodistribution; single-dose 177Lu-radiotherapy) evaluations.

Results: SA conjugation conferred the highest FAP affinity (docking score - 9.475 kcal mol-1; IC₅₀ 2.94 ± 0.41 nM), greatest hydrophilicity (LogP -5.27 ± 0.06), and > 95 % radiochemical integrity after 48 h in serum. 68Ga-FAP2286-SA achieved rapid tumor uptake (23.4 ± 2.1 %ID g-1 at 4 h) with T/B = 78.0; 177Lu-FAP2286-SA displayed sustained accumulation (23.5 ± 2.1 %ID g-1 at 48 h) and T/B = 33.6. A single 37 MBq dose of 177Lu-FAP2286-SA produced 186.0 % TGI (day 33) without overt hepatorenal or hematologic toxicity. MeO substitution modestly reduced hepatic background yet significantly compromised tumor retention and therapeutic efficacy.

Conclusions: Squaric acid derivatization synergistically elevates affinity, hydrophilicity, and intratumoral residence while preserving safety, establishing 68Ga/177Lu-FAP2286-SA as a clinically translatable, next-generation theranostic pair for FAP-positive malignancies.

Keywords

(68)Ga/(177)Lu theranostics; FAP2286; Fibroblast activation protein (FAP); Squaric acid pharmacophore; Tumor retention.

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