4-[18F]-Fluorophenylglyoxal ([18F]-FPG) is a novel arginine selective bioconjugation reagent for native protein 18F-labeling. Here, we report the automated radiosynthesis of [18F]-FPG on a Scintomics GRP module. The radiochemical preparation was performed in a one-pot, two-step process using a DMSO-resistant cassette system. A cartridge-based purification method was developed to purify [18F]-FPG without HPLC. The [18F]-FPG was prepared in nondecay corrected (n.d.c.) radiochemical yields (RCYs) of 27 ± 2% (n = 5) in 56 min from the end of the bombardment until formulation. The molar activities of [18F]-FPG were 147 ± 70 GBq/μmol (n = 5). The 4-[18F]-FPG was then conjugated with interleukin-4 (IL-4) in n.d.c. 26 ± 2% RCYs (n = 3) from [18F]-FPG with molar activities of 24 ± 4 GBq/μmol (n = 3). [18F]-FPG-IL4 exhibited >95% stability in either PBS (4 h) or human serum (2 h) in vitro. [18F]-FPG-IL4 showed specific uptake by the PHA-activated Jurkat cells. The in vivo biodistribution and pharmacokinetics of [18F]-FPG-IL4 were evaluated in healthy Balb/c mice with PET imaging.

Prostate-specific membrane antigen (PSMA) radioligand therapy (PRLT) has become a promising option for treating metastatic castration-resistant prostate cancer (mCRPC). Radioligands labelled with the 68Ga/177Lu theranostic pair have been most widely used in the clinic for diagnosis and therapy, respectively. This study aims to develop a novel PSMA-targeted radioligand, LNC1011, radiolabeled with alpha-emitter 225Ac, to optimise pharmacokinetic properties and assess its potential for targeted alpha therapy (TAT) in prostate cancer treatment. LNC1011 (Dan-PSMA) was synthesised based on a PSMA-binding ligand with the addition of a dansylated amino acid. Systematic radiochemical analyses were conducted to confirm the successful synthesis and radiolabelling of [225Ac]Ac-LNC1011. Cell uptake and competition binding assays were performed in PSMA-positive PC3-PIP tumour cells to evaluate the binding affinity and PSMA targeting specificity. The pharmacokinetics properties and tumour uptake were characterised by biodistribution studies using healthy mice and a PC3-PIP xenograft mouse model injected with [225Ac]Ac-LNC1011. Radioligand therapy studies and maximum tolerated dose (MTD) assays were conducted to systematically evaluate the therapeutic efficacy and the safety of [225Ac]Ac-LNC1011. [225Ac]Ac-LNC1011 was successfully radiolabelled with high radiochemical purity (> 97

18F-interleukin-2 based PET imaging of activated T cells serves as a potential tool for non-invasive response prediction, treatment evaluation, and patient stratification in cancer immune checkpoint therapy. Herein, we report the radiolabelling of interleukin-2 (IL-2) with a novel arginine selective bioconjugation reagent, 4-[18F]fluorophenylglyoxal ([18F]FPG). Good non-decay corrected bioconjugation efficiencies of 29 ± 4 % (n = 5) were obtained for the [18F]FPG-IL-2. [18F]FPG-IL-2 uptake by the phytohemagglutinin-activated Jurkat cells (50.5 ± 1.2 %, n = 3) was significantly higher compared to the non-activated Jurkat cells (12.9 ± 1.1 %, n = 3). The [18F]FPG-IL-2 uptake was blocked by the pre-treatment of activated Jurkat cells with excess native IL-2 (22.3 ± 2.2 %, n = 3). Dynamic PET imaging and ex vivo biodistribution study of [18F]FPG-IL-2 in healthy and CT26 tumour bearing mice demonstrated hepatobiliary and renal clearance with minimal uptake in other organs and CT26 tumours. [18F]FPG-IL-2 PET imaging was applied to non-invasively monitor immune checkpoint therapy in CT26 tumour bearing mice, treated with IgG (control), ⍺PD-1 (monotherapy), and ⍺PD-1+⍺CTLA-4 (combination therapy). Significant uptake was observed in the spleens and tumours of the mice in the combination therapy group, which was associated with increased cytotoxic CD8+ T-cell infiltration and reduced tumour volumes. [18F]FPG-IL-2 based PET imaging has the potential to monitor immune checkpoint therapy.

Protein-based F-18-PET tracers offer new possibilities in early disease detection and personalized medicine. Their development relies heavily on the availability and effectiveness of F-18-prosthetic groups. We prepared and evaluated a novel arginine-selective prosthetic group, 4-[F-18]fluorophenylglyoxal ([F-18]FPG). [F-18]FPG was radiosynthesized by a one-pot, two-step procedure with a non-decay-corrected (n.d.c.) isolated radiochemical yield (RCY) of 41 +/- 8% (n = 10). [F-18]FPG constitutes a generic tool for F-18-labeling of various proteins, including human serum albumin (HSA), ubiquitin, interleukin-2, and interleukin-4 in similar to 30-60% n.d.c. isolated RCYs. [F-18]FPG conjugation with arginine residues is highly selective, even in the presence of a large excess of lysine, cysteine, and histidine. [F-18]FPG protein conjugates are able to preserve the binding affinity of the native proteins while also demonstrating excellent in vivo stability. The [F-18]FPG-HSA conjugate has prolonged blood retention, which can be applied as a potential blood pool PET imaging agent. Thus, [F-18]FPG is an arginine-selective bioconjugation reagent that can be effectively used for the development of F-18-labeled protein radiopharmaceuticals.