Synthesis and preclinical evaluation of a novel probe [18F]AlF-NOTA-IPB-GPC3P for PET imaging of GPC3 positive tumor.

Glypican-3 (GPC3) is markedly overexpressed in hepatocellular carcinoma (HCC) and not expressed in normal liver tissues. In this study, a novel peptide PET imaging agent ([18F]AlF-NOTA-IPB-GPC3P) was developed to target GPC3 expressed in tumors. The overall radiochemical yield of [18F]AlF-NOTA-IPB-GPC3P was 10-15 %, and its lipophilicity, expressed as the logD value at a pH of 7.4, was -1.18 ± 0.06 (n = 3). Compared to the previously reported tracer [18F]AlF-GP2633, [18F]AlF-NOTA-IPB-GPC3P exhibited higher cellular uptake (15.13 vs 5.96) and internalized rate (80.63 % vs 35.93 %) in Huh7 cells at 120 min. Micro-PET/CT and biodistribution studies further demonstrated that [18F]AlF-NOTA-IPB-GPC3P exhibited significantly increased tumor uptake and prolonged tumor residence in Huh7 tumors compared to [18F]AlF-GP2633 (4.66 ± 0.22 % ID/g vs 0.72 ± 0.09 % ID/g at 60 min, p < 0.001; 5.05 ± 0.23 % ID/g vs 0.35 ± 0.08 % ID/g at 120 min, p < 0.001, respectively). Furthermore, the tumor-to-organ ratios of [18F]AlF-NOTA-IPB-GPC3P surpassed those of [18F]AlF-GP2633. Our results support the utilization of [18F]AlF-NOTA-IPB-GPC3P as a PET imaging agent targeting the GPC3 receptor for tumor detection.

A Comparison of Evans Blue and 4-(p-Iodophenyl)butyryl Albumin Binding Moieties on an Integrin αvß6 Binding Peptide.

Serum albumin binding moieties (ABMs) such as the Evans blue (EB) dye fragment and the 4-(p-iodophenyl)butyryl (IP) have been used to improve the pharmacokinetic profile of many radiopharmaceuticals. The goal of this work was to directly compare these two ABMs when conjugated to an integrin αvß6 binding peptide (αvß6-BP); a peptide that is currently being used for positron emission tomography (PET) imaging in patients with metastatic cancer. The ABM-modified αvß6-BP peptides were synthesized with a 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetracetic acid (DOTA) chelator for radiolabeling with copper-64 to yield [64Cu]Cu DOTA-EB-αvß6-BP ([64Cu]1) and [64Cu]Cu DOTA-IP-αvß6-BP ([64Cu]2). Both peptides were evaluated in vitro for serum albumin binding, serum stability, and cell binding and internalization in the paired engineered melanoma cells DX3puroß6 (αvß6 +) and DX3puro (αvß6 −), and pancreatic BxPC-3 (αvß6 +) cells and in vivo in a BxPC-3 xenograft mouse model. Serum albumin binding for [64Cu]1 and [64Cu]2 was 53−63% and 42−44%, respectively, with good human serum stability (24 h: [64Cu]1 76%, [64Cu]2 90%). Selective αvß6 cell binding was observed for both [64Cu]1 and [64Cu]2 (αvß6 (+) cells: 30.3−55.8% and 48.5−60.2%, respectively, vs. αvß6 (−) cells <3.1% for both). In vivo BxPC-3 tumor uptake for both peptides at 4 h was 5.29 ± 0.59 and 7.60 ± 0.43% ID/g ([64Cu]1 and [64Cu]2, respectively), and remained at 3.32 ± 0.46 and 4.91 ± 1.19% ID/g, respectively, at 72 h, representing a >3-fold improvement over the non-ABM parent peptide and thereby providing improved PET images. Comparing [64Cu]1 and [64Cu]2, the IP-ABM-αvß6-BP [64Cu]2 displayed higher serum stability, higher tumor accumulation, and lower kidney and liver accumulation, resulting in better tumor-to-organ ratios for high contrast visualization of the αvß6 (+) tumor by PET imaging.

Synthesis and biological evaluation of Al[18F]-NOTA-IPB-PDL1P as a molecular probe for PET imaging of PD-L1 positive tumors.

PD-L1 is widely expressed in a variety of tumors, including NSCLC, melanoma, renal cell carcinoma, gastric cancer, hepatocellular as well as cutaneous and various leukemias, multiple myeloma and so on. Herein, we designed a novel peptide imaging agent (Al[18F]-NOTA-IPB-PDL1P) that specifically targets PD-L1 expressed in tumors. The overall radiochemical yield of Al[18F]-NOTA-IPB-PDL1P from 18F- was 10-15% (corrected radiochemical yield) within 20 min and the radiochemical purity of Al[18F]-NOTA-IPB-PDL1P was > 95% with a molar activity of 44.4-64.8 GBq/µmol. The lipophilicity logP value of Al[18F]-NOTA-IPB-PDL1P at pH 7.4 was -1.768 ±â€¯0.007 (n = 3). In the cellular uptake experiment, both HCT116 and PC3 cells dispalyed high uptake to Al[18F]-NOTA-IPB-PDL1P. The results of biodistribution showed that the uptake of Al[18F]-NOTA-IPB-PDL1P was high in kidneys, gall bladder and lung, and low in muscle and brain. In vivo micro PET studies, both HCT116 and PC3 tumors displayed high uptake for Al[18F]-NOTA-IPB-PDL1P, the tumor/muscle (T/M) radio was 2.93 and 3.57 respectively at 120 min. All the results indicate that Al[18F]-NOTA-IPB-PDL1P may have potential to be a PET imaging agent of tumors with high PD-L1 expression.