Abstract 2585: First in human study with a novel peptide binder to glypican-3, demonstrates high specificity as a PET imaging agent in patients with hepatocellular carcinoma
Authors: Bal Chandresakhar , Ballal Sanjana , Kallur Kumar , Karmann Anna , Yuan Ye , Rearden Jessica , Shah Kathryn , Lorenz Charlotte , Moran Susan , Song Ken , Sen Ishita 
Published: March 2024

Introduction: Hepatocellular carcinoma (HCC) is the most common primary liver malignancy. The American Association for the Study of Liver Disease recommends surveillance for high-risk individuals with abdominal ultrasound, triple phase contrast CT or MRI. However, these imaging techniques have limited sensitivity in classifying lesions smaller than 2 centimeters. The use of [18F]FDG Positron Emission Tomography (PET) is constrained due to insufficient uptake by HCC lesions over background liver uptake. Hence, there is an urgent need for more precise radiotracers for HCC. This study introduces the development of a novel radiotracer that binds to glypican-3 (GPC3), a cell membrane-anchored oncofetal protein overexpressed in HCC with minimal normal tissue expression.

Methods: [68Ga]Ga-RYZ-GPC3 is composed of a small macrocyclic peptide binder with high affinity to GPC3 linked with a tetraxetan moiety capable of chelating a variety of radioisotopes including positron-emitting 68Ga and other radiometals. The unlabeled binder to GPC3 was synthesized by the sponsor and provided to three imaging centers in India as part of investigator-initiated trials reviewed and approved by each site’s institutional review board and ethics committee. Labeling with 68Ga and quality checks of the product was performed locally at each center. Patients with high clinical suspicion or with confirmed HCC who gave informed consent received injections of 1.5-5.5 mCi of [68Ga]Ga-RYZ-GPC3 and underwent PET-CT scanning at predetermined intervals. Some patients underwent companion [18F]FDG PET-CT scans in accordance with local guidelines.

Results: A total of 64 patients underwent [68Ga]Ga-RYZ-GPC3 PET-CT scans. The median age within the cohort was 61 (41-83), 22% were female. Liver cirrhosis was present in 72% of patients, attributed to hepatitis B, hepatitis C or NASH in 17%, 13% and 20% of cases. Notably, 92% of patients exhibited at least one positive lesion on [68Ga]Ga-RYZ-GPC3 scans. The median SUVmax of GPC3-avid liver lesions was 15.5 (range 1.1 to 137.0) while the median liver SUVmean was 1.6 (0.3-7.9). Physiologic uptake was predominantly observed in the kidneys, the primary route of clearance, with a median SUVmean of 10.9 (2.2-20.7). Additionally, 20 patients underwent [18F]FDG PET-CT scan for comparison. The median SUVmax of lesions on 68Ga-RYZ-GPC3 vs [18F]FDG PET was 11.0 (1.1-137.0) vs 3.8 (1.2-12.2).

Conclusion: Early human imaging results in patients with HCC indicate that [68Ga]Ga-RYZ-GPC3 has high tumor lesion specificity compared to normal liverand demonstrates the potential of [68Ga]Ga-RYZ-GPC3 to improve detection of HCC over conventional [18F]FDG PET-CT. In addition, the binder could be complexed with a therapeutic radioisotope as a novel targeted therapeutic option for HCC. Further investigation of this first-in-class binder to HCC is warranted.

Citation Format: Chandresakhar Bal, Sanjana Ballal, Kumar Kallur, Anna Karmann, Ye Yuan, Jessica Rearden, Kathryn Shah, Charlotte Lorenz, Susan Moran, Ken Song, Ishita Sen. First in human study with a novel peptide binder to glypican-3, demonstrates high specificity as a PET imaging agent in patients with hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2585.