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Updated: Aug 6, 2026
![Automated Preparation of [68Ga]Ga-3BP-3940 on a Synthesis Module for PET Imaging of the Tumor Microenvironment](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F68356.jpg&w=3840&q=50)
Automated Preparation of [68Ga]Ga-3BP-3940 on a Synthesis Module for PET Imaging of the Tumor Microenvironment
Published on: April 25, 2025
Design, Synthesis, Molecular Docking, and Preclinical Evaluation of a New Radiolabeled PEG3-Linked FAPI Derivative
Mahshid Kiani1, Mehdi Akhlaghi2, Safura Jokar1
1Department of Nuclear Pharmacy, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran.
Background:
Fibroblast activation protein (FAP) is a promising molecular target for cancer theranostic applications. However, current fibroblast activation protein inhibitors (FAPIs) have limitations, including rapid clearance and limited tumor retention.
Objectives:
This study aimed to develop a novel PEG3-linked FAPI derivative, [68Ga]Ga-FAPI-MKG, with enhanced tumor accumulation and retention. FAPI-MKG was prepared by incorporating a PEG3 linker into the FAPI-04 structure to optimize its pharmacokinetic profile.
Methods:
The compound was synthesized via an 11-step route starting from quinine sulfate and radiolabeled with gallium-68. In vitro studies included determination of lipophilicity (Log P) and stability assays in saline and human serum albumin. Preclinical evaluation in BALB/c mice bearing CT-26 tumors included biodistribution, blocking studies, and PET/CT imaging. Molecular docking and molecular dynamics simulations were performed to provide mechanistic insights into binding interactions.
Results:
[68Ga]Ga-FAPI-MKG was successfully synthesized with high radiochemical purity (> 98%) and a molar activity of 414.79 mCi/μmol. It demonstrated moderate hydrophilicity (Log P = -3.26 ± 0.18) compared with the reference radiotracer, [68Ga]Ga-FAPI-46 (-3.58 ± 0.29), and high stability (RCP > 90% after 120 minutes). In vivo studies showed significantly higher tumor uptake (7.18 ± 0.56% ID/g at 60 minutes; 3.20 ± 0.11% ID/g at 120 minutes) and prolonged retention compared with the reference radiotracer, along with dual hepatobiliary and renal excretion pathways. Blocking studies confirmed FAP-specific uptake. Computational analyses indicated strong binding energy (-9.8 kcal/mol) and optimized electrostatic interactions with FAP. The strategic incorporation of a PEG3 linker into [68Ga]Ga-FAPI-MKG significantly improved tumor accumulation, extended tumor retention, and increased the tumor-to-background ratio.
Conclusions:
These findings suggest that [68Ga]Ga-FAPI-MKG may be a promising candidate for clinical translation for imaging and theranostics of FAP-expressing cancers.
Insights
A novel Gallium-68 fibroblast activation protein inhibitor, [68Ga]Ga-FAPI-MKG, demonstrates improved tumor targeting and retention for cancer theranostics. This PEG3-linked derivative shows promise for enhanced imaging and treatment of FAP-expressing cancers.
Area of Science:
- Radiochemistry and Molecular Imaging
- Cancer Theranostics
- Preclinical Cancer Research
Background:
- Fibroblast Activation Protein (FAP) is a key target for cancer theranostics.
- Current FAP inhibitors (FAPIs) face challenges with rapid clearance and limited tumor retention.
Purpose of the Study:
- Develop a novel PEG3-linked FAPI derivative, [68Ga]Ga-FAPI-MKG.
- Enhance tumor accumulation and retention for improved theranostic applications.
Main Methods:
- Synthesized and radiolabeled FAPI-MKG with Gallium-68.
- Conducted in vitro (lipophilicity, stability) and in vivo (biodistribution, PET/CT) preclinical studies.
- Utilized molecular docking and dynamics simulations for mechanistic insights.
Main Results:
- Achieved high radiochemical purity (>98%) and stability for [68Ga]Ga-FAPI-MKG.
- Demonstrated significantly higher tumor uptake and prolonged retention compared to a reference tracer.
- Confirmed FAP-specific uptake and favorable tumor-to-background ratios.
Conclusions:
- [68Ga]Ga-FAPI-MKG exhibits superior pharmacokinetic properties and tumor targeting.
- The PEG3 linker effectively enhances FAPI performance for theranostic applications.
- This novel agent holds potential for clinical translation in FAP-expressing cancers.
![An Automated Radiosynthesis of [68Ga]Ga-FAPI-46 for Routine Clinical Use](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F66708.jpg&w=3840&q=50)
