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Published on: April 29, 2017
124I-Labeled Specific Antibody Targeting LAG-3 for ImmunoPET
Lixin Ding1,2, Feng Wang2, Yongxiang Pan2
1National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, Beijing, 100088, China.
Insights
This study developed a novel PET imaging agent, 124I-HuL13, for noninvasively detecting Lymphocyte-activation gene 3 (LAG-3) expression. The agent demonstrated high stability and specificity, showing promise for optimizing LAG-3-targeted immunotherapy.
Area of Science:
- Nuclear medicine
- Molecular imaging
- Immunotherapy
Background:
- Lymphocyte-activation gene 3 (LAG-3) is a key immune checkpoint and a promising therapeutic target.
- Noninvasive methods for assessing LAG-3 expression are currently limited, hindering treatment optimization.
Purpose of the Study:
- To develop and evaluate an antibody-dependent molecular imaging strategy for noninvasive LAG-3 detection using a LAG-3-specific antibody, HuL13.
- To assess the feasibility of using radiolabeled HuL13 for Positron Emission Tomography (PET) imaging of LAG-3 expression.
Main Methods:
- The anti-LAG-3 antibody HuL13 was radiolabeled with Iodine-124 (124I).
- Specificity and affinity of 124I-HuL13 were confirmed using cell-based assays.
- Micro-PET/CT imaging was performed in mice bearing LAG-3-expressing tumors, followed by immunohistochemistry (IHC) for validation.
Main Results:
- 124I-HuL13 showed high radiochemical yield (>95%), purity (>99%), and stability.
- The radiotracer exhibited specific binding to LAG-3-expressing cells with a dissociation constant (Kd) of 23.02 nM.
- In vivo imaging revealed significant accumulation of 124I-HuL13 in tumors, with uptake correlating to LAG-3 expression.
Conclusions:
- 124I-HuL13 is a stable and effective PET imaging radiotracer for noninvasive LAG-3 detection.
- This molecular imaging approach holds potential for guiding and optimizing LAG-3-targeted immunotherapies in clinical settings.
Purpose:
Lymphocyte-activation gene 3 (LAG-3), a next-generation immune checkpoint, has emerged as a promising therapeutic target, but noninvasive tools for evaluating LAG-3 expression remain limited. Herein, we explored an antibody-dependent molecular imaging strategy for noninvasive detection based on a LAG-3-specific antibody, HuL13.
Procedures:
The anti-LAG-3 antibody HuL13 was radiolabeled with 124I via electrophilic substitution. LAG-3-expressing A549 cells were constructed by infection with the lentivirus. The specificity and affinity of 124I-HuL13 to LAG-3 receptor were evaluated by cell uptake assay and saturation binding assay. Micro-PET/CT imaging studies were conducted in BALB/c nude mice bearing LAG-3+ A549 tumors. Immunohistochemistry (IHC) validated LAG-3 expression in tumors.
Results:
The 124I-HuL13 exhibited a good radiochemical yield of 95.59 ± 1.27%, high radiochemical purity (RCP, > 99%), and excellent stability. Cell binding assays demonstrated that 124I-HuL13 had a higher binding ability to LAG-3+ A549 cells compared to control cells. The equilibrium dissociation constant (Kd) of 124I-HuL13 was 23.02 nM for LAG-3+ A549 cells. In vivo pharmacokinetics revealed favorable metabolic stability (t1/2β = 12.07 h). Micro-PET/CT images showed that 124I-HuL13 significantly accumulated in LAG-3+ A549 tumor from 24 h after injection (SUVmax = 0.34 ± 0.03 at 24 h), and high contrast tumor to background imaging was clearly observed. IHC confirmed LAG-3 expression correlated with probe uptake.
Conclusions:
124I-HuL13 is a novel LAG-3-targeted PET imaging radiotracer with excellent stability. This study highlights 124I-HuL13 as a robust tool for noninvasive LAG-3 imaging, offering potential for optimizing LAG-3-targeted immunotherapy in clinical settings.
