Journal of labelled compounds & radiopharmaceuticals最新文献

Recently, the folate receptor (FR) has become an exciting target for the diagnosis of FR-positive malignancies. Nevertheless, suboptimal in vivo pharmacokinetic properties, particularly high uptake in the renal and hepatobiliary systems, are important limiting factors for the clinical translation of most FR-based radiotracers. In this study, we developed a novel ¹⁸F-labeled FR-targeted positron emission tomography (PET) tracer [¹⁸F]AlF-NOTA-Asp₂-PEG₂-Folate modified with a hydrophilic linker (−Asp₂-PEG₂) to optimize its pharmacokinetic properties and conducted a comprehensive preclinical assessment. The [¹⁸F]AlF-NOTA-Asp₂-PEG₂-Folate was manually synthesized within 30 min with a non-decay-corrected radiochemical yield of 16.3 ± 2.0% (n = 5). Among KB cells, [¹⁸F]AlF-NOTA-Asp₂-PEG₂-Folate exhibited high specificity and affinity for FR. PET/CT imaging and biodistribution experiments in KB tumor-bearing mice showed decent tumor uptake (1.7 ± 0.3% ID/g) and significantly decreased uptake in kidneys and liver (22.2 ± 2.1 and 0.3 ± 0.1% ID/g at 60 min p.i., respectively) of [¹⁸F]AlF-NOTA-Asp₂-PEG₂-Folate, compared to the known tracer [¹⁸F]AlF-NOTA-Folate (78.6 ± 5.1 and 5.3 ± 0.5 % ID/g at 90 min p.i., respectively). The favorable properties of [¹⁸F]AlF-NOTA-Asp₂-PEG₂-Folate, including its efficient synthesis, decent tumor uptake, relatively low renal uptake, and rapid clearance from most normal organs, portray it as a promising PET tracer for FR-positive tumors.

Herein, we demonstrate an efficient method for multi-deuterium labelling of pirtobrutinib—a Bruton's tyrosine kinase inhibitor recently approved by the FDA—using a straightforward hydrogen isotope exchange (HIE) reaction. A remarkably high level of deuterium incorporation was achieved using an excess of a Kerr-type iridium catalyst. The key factor in the significant deuterium labelling was the decision to employ a deuterium uniformly labelled solvent, chlorobenzene-d₅, at an elevated temperature. Virtually, no d₀–d₃ species were detected, with only traces of d₄–d₅ isotopomers (< 5%) observable in the mass spectrum of pirtobrutinib-d₈, fulfilling requirements for stable isotope-labelled internal standard. The labelled compound—mainly consisting of isotopomers d₆–d₉ at 82.4% of the total abundance—was isolated in a high yield (73%) and purity (99%). Noteworthy, fluorine group acting as a directing group was observed for the first time. Significant incorporation of deuterium in ortho-positions, exceeding 87%, was observed. Interestingly, chlorinated solvent used in the HIE reactions was non-specifically deuterated yielding up to 0.42 deuterium per chlorobenzene molecule even at an exceptionally low iridium catalyst loading of 4.17 × 10^–2 mol%.

Due to the continuous rise in global incidence and severity of invasive fungal infections (IFIs), particularly among immunocompromised and immunodeficient patients, there is an urgent demand for swift and accurate fungal pathogen diagnosis. Therefore, the need for fungal-specific positron emission tomography (PET) imaging agents that can detect the infection in the early stages is increasing. Cellobiose, a disaccharide, is readily metabolized by fungal pathogens such as Aspergillus species. Recently, our group reported fluorine-18 labeled cellobiose, 2-deoxy-2-[¹⁸F]fluorocellobiose ([¹⁸F]FCB), for specific imaging of Aspergillus infection. The positive imaging findings with very low background signal on delayed imaging make this ligand a promising fungal-specific imaging ligand. Inspired by this result, the decision was made to automate the radiolabeling procedure for better reproducibility and to facilitate clinical translation. A Trasis AllInOne (Trasis AIO) automated module was used for this purpose. The reagent vials contain commercially available 2-deoxy-2-[¹⁸F]fluoroglucose ([¹⁸F]FDG), glucose-1-phosphate, and enzyme (cellobiose phosphorylase). A Sep-Pak cartridge was used to purify the tracer. The overall radiochemical yield was 50%–70% (n = 6, decay corrected) in 75-min synthesis time with a radiochemical purity of > 98%. This is a highly reliable protocol to produce current good manufacturing practice (cGMP)–compliant [¹⁸F]FCB for clinical PET imaging.

Cathepsin B (CTSB) is a lysosomal protease that is overexpressed in tumor cells. Radioimmunoconjugates (RICs) composed of CTSB-recognizing chelating agents are expected to increase the molecular weights of their radiometabolites by forming conjugates with CTSB in cells, resulting in their improved retention in tumor cells. We designed a novel CTSB-recognizing trifunctional chelating agent, azide-[¹¹¹In]In-DOTA-CTSB-substrate ([¹¹¹In]In-ADCS), to synthesize a RIC, trastuzumab-[¹¹¹In]In-ADCS ([¹¹¹In]In-TADCS), and evaluated its utility to improve tumor retention of the RIC. [¹¹¹In]In-ADCS and [¹¹¹In]In-TADCS were synthesized with satisfactory yield and purity. [¹¹¹In]In-ADCS was markedly stable in murine plasma until 96 h postincubation. [¹¹¹In]In-ADCS showed binding to CTSB in vitro, and the conjugation was blocked by the addition of CTSB inhibitor. In the internalization assay, [¹¹¹In]In-TADCS exhibited high-level retention in SK-OV-3 cells, indicating the in vitro utility of the CTSB-recognizing unit. In the biodistribution assay, [¹¹¹In]In-TADCS showed high-level tumor accumulation, but the retention was hardly improved. In the first attempt to combine a CTSB-recognizing unit and RIC, these findings show the fundamental properties of the CTSB-recognizing trifunctional chelating agent to improve tumor retention of RICs.

Carbon-14 labeling synthesis of RORγt inhibitor JNJ-61803534 (1) was accomplished in four steps with the C14 label located at the thiazole-2-carboxamide carbon. The synthesis featured a highly efficient conversion of nitrile [¹⁴C]-12 to ester [¹⁴C]-17 under mild conditions via an imidate intermediate, overcoming the unsuccessful direct hydrolysis of nitrile 12 under either acidic or basic conditions. Since carbon-14 labeling via [¹⁴C]-nitrile installation and subsequent conversion to [¹⁴C]-carboxylic acid derivatives is a common labeling strategy, an efficient conversion of a nitrile to an ester under mild conditions could be of use for the future C14 labeling syntheses.

Rimsulfuron is a sulfonylurea herbicide that controls grass and broadleaf weeds in maize, potatoes, fruits, nuts, and other crops. It can also be used as a burndown herbicide to clear invasive weed species along roadsides and other nonagricultural land. Rimsulfuron acts as an acetolactase synthase (ALS) inhibitor, blocking the synthesis of essential amino acids required for plant growth. As is common practice, rimsulfuron has been subject to periodic reviews by regulatory agencies for reregistration since its introduction into the market in the early 1990s. The goal of these reviews is to ensure that the herbicide carries out its intended use without creating adverse side effects to humans and the environment. Since scientific methods are continually evolving and being developed, global regulatory agencies can require additional studies to address data gaps for pesticide renewals. During this reregistration process for rimsulfuron, a new confined rotational crop study was required to address a data gap requested by the European Food Safety Authority (EFSA). Consequently, the corresponding pyridine and pyrimidine radiolabeled [¹⁴C]rimsulfuron and [M + 3] stable isotopes of rimsulfuron were synthesized for this study to support the reregistration process.

Reductive N-¹¹C-methylation using [¹¹C]formaldehyde and amines has been used to prepare N-¹¹C-methylated compounds. However, the yields of the N-¹¹C-methylated compounds are often insufficient. In this study, we developed an efficient method for base-free reductive N-¹¹C-methylation that is applicable to a wide variety of substrates, including arylamines bearing electron-withdrawing and electron-donating substituents. A 2-picoline borane complex, which is a stable and mild reductant, was used. Dimethyl sulfoxide was used as the primary reaction solvent, and glacial acetic acid or aqueous acetic acid was used as a cosolvent. While reductive N-¹¹C-methylation efficiently proceeded under anhydrous conditions in most cases, the addition of water to the reductive N-¹¹C-methylation generally increased the yield of the N-¹¹C-methylated compounds. Substrates with hydroxy, carboxyl, nitrile, nitro, ester, amide, and phenone moieties and amine salts were applicable to the reaction. This proposed method for reductive N-¹¹C-methylation should be applicable to a wide variety of substrates, including thermo-labile and base-sensitive compounds because the reaction was performed under relatively mild conditions (70°C) without the need for a base.