Butyrylcholinesterase (BChE) is recognized as a promising therapeutic target for the late stages of Alzheimer's disease (AD) due to its role in the hydrolysis of acetylcholine (ACh), while acetylcholinesterase (AChE) activity declines during disease progression. Here, we have reported an efficient chemistry procedure for the naturally occurring Amaryllidaceae alkaloid carltonine B, along with the design and synthesis of 36 novel carltonine-based analogues to determine structure-activity relationship (SAR). Most of the synthesized compounds exhibited potent and selective human BChE (hBChE) inhibition, with IC50 values ranging from low micromolar to nanomolar concentrations. The drug-like properties of the molecules were assessed by in silico tools, using the blood-brain barrier (BBB) score algorithm, and subsequently validated by in vitro permeability assessment via parallel artificial membrane permeability assay (PAMPA). The derivatives exhibited potent hBChE inhibition in the low micromolar to submicromolar range, while their cytotoxicity against human neuroblastoma (SH-SY5Y) cells was observed only at higher micromolar concentrations, indicating a favorable safety profile. The synthesized alkaloid carltonine B (37) and its N-ethyl derivative (38) emerged as the most potent and selective hBChE inhibitors, with IC50 values of 0.014 ± 0.002 μM and 0.013 ± 0.001 μM, respectively. Enzyme kinetic studies were conducted to elucidate the inhibition mechanism toward hBChE enzyme. Compound 37 demonstrated competitive inhibition with Ki value of 0.055 μM. In contrast, compound 38 showed a noncompetitive inhibition profile, with a Ki value of 0.067 μM. Molecular modeling suggested that the superior potency of compounds 37 and 38 arises from their more optimal engagement of the BChE active-site gorge compared to compound 33. For the additional safety assessment, CYP inhibition assay revealed that compounds 37 and 38 may pose a risk of CYP3A4-mediated drug-drug interactions during chronic administration.

The synthesis of both aza- and diaza-cyclotribenzylidene (CTB-1NH and CTB-2NH, respectively), cyclotribenzylidenes functionalized with one or two nitrogen atoms replacing methylene bridges, is reported, as well as the alkylation and the acylation of these compounds. The conformations adopted by these compounds have been studied in solution by 1H NMR analysis and in the solid state.

The development of new boron reagents continues to play a crucial role in advancing modern organic synthesis, particularly in C–H functionalization and cross‐coupling reactions. Herein, we report a metal‐free, robust, and scalable multigram protocol for the synthesis of stable BF 2 boracycles that require no column chromatography, providing a practical and efficient route to access this valuable boron species. The BF 2 boracycles exhibit enhanced stability and reactivity, making them highly versatile intermediates for late‐stage diversification. They undergo ipso ‐substitution to afford a wide array of derivatives, including halogenated (e.g., radioiodinated), hydroxylated, and azidated products. Furthermore, they display excellent reactivity in Suzuki–Miyaura cross‐coupling reactions, enabling both C(sp 2 )─C(sp 2 ) and C(sp 2 )─C(sp 3 ) bond formation. These results underscore the utility of BF 2 boracycles as powerful tools for selective functionalization in pharmaceutical synthesis and beyond. Our work represents a significant advancement in organoboron chemistry, offering both a streamlined synthetic approach and broad applicability for complex molecule construction.

Self-immolative systems first emerged in prodrug chemistry in the 1980s. Since then, several types of self-immolative systems have been developed. Despite their structural differences, all self-immolative systems operate on the same principle: an intramolecular reaction cascade triggered by a specific stimulus, ultimately leading to the release of a molecule of interest. Self-immolative systems offer the possibility of delivering molecules safely, ensuring their specific, residue-free release at a defined location. Consequently, they have been applied in various fields, including targeted drug delivery, detection of protein biomarkers and small endogenous molecules, signal amplification, and the engineering of nanomedicines. Self-immolative systems therefore represent a versatile platform for chemical engineering in biomedical sciences.

Efficient chloride/iodide exchange on chloro-NHC-metal complexes was achieved under mild conditions using stable or radioactive iodide. The protocol enables simultaneous synthesis of radiolabeled compounds and their non-radioactive references, facilitating the development of chemically matched theranostic pairs.

Alzheimer′s disease (AD), the most common cause of dementia, represents one of the main clinical challenges of the century as the number of patients is predicted to triple by 2050. Despite the recent approval of three monoclonal antibodies targeting Amyloid β (Aβ) aggregates by the Food and Drug Administration (FDA), immunotherapies still face challenges due to the difficulty of antibodies crossing the blood-brain barrier (BBB). This necessitates administering large doses of drugs to achieve their therapeutic effects, which is associated with significant side effects. In this context, low-intensity focused ultrasound (LiFUS) appears as an innovative and non-invasive method which, in association with intravenous injection of microbubbles (MB), leads to a transient BBB opening. This innovative strategy has been extensively studied in different preclinical models and more recently in human clinical trials, particularly in the context of AD. LiFUS+MB seems to increase the inflammatory response at short term, but the time course of this response is not consistent between studies, certainly due to the discrepancy between LiFUS protocols used. Moreover, the impact at longer term is understudied and the mechanisms underlying this effect are still not well understood. In our study, we therefore used the TgF344-AD rat model of AD, to investigate the effect of a single or multiple exposures to LiFUS+MB in the entire brain, on inflammatory response and amyloid load. The ultrasound attenuation through the skull was corrected to apply a peak negative acoustic pressure of 450 kHz in all treated animals. Single LiFUS+MB exposure induces a slight astrocyte and microglial response 24 hours post-treatment whereas repeated LiFUS treatment seems to induce microglial reprogramming, leading to the adaptation of gene expression related to key functions such as inflammatory response, mitochondrial and energetic metabolism. In our rat model and LiFUS+MB protocol conditions, multiple exposures did not modulate soluble/poorly aggregated forms nor the highly aggregated forms of Aβ40 and Aβ42. For therapeutic AD management, LiFUS+MB could be combined with drugs such as immunotherapies. In a proof-of-concept experiment, we validated that LiFUS was also efficient to improve the brain entry of the anti-Aβ antibody, Aducanumab. ### Competing Interest Statement The authors have declared no competing interest.

The small-molecule iododiflunisal (IDIF) is a transthyretin (TTR) tetramer stabilizer and acts as a chaperone of the TTR-Amyloid beta interaction. Oral administration of IDIF improves Alzheimer’s Disease (AD)-like pathology in mice, although the mechanism of action and pharmacokinetics remain unknown. Radiolabeling IDIF with positron or gamma emitters may aid in the in vivo evaluation of IDIF using non-invasive nuclear imaging techniques. In this work, we report an isotopic exchange reaction to obtain IDIF radiolabeled with 18F. [19F/18F]exchange reaction over IDIF in dimethyl sulfoxide at 160 °C resulted in the formation of [18F]IDIF in 7 ± 3% radiochemical yield in a 20 min reaction time, with a final radiochemical purity of >99%. Biodistribution studies after intravenous administration of [18F]IDIF in wild-type mice using positron emission tomography (PET) imaging showed capacity to cross the blood-brain barrier (ca. 1% of injected dose per gram of tissue in the brain at t > 10 min post administration), rapid accumulation in the liver, long circulation time, and progressive elimination via urine. Our results open opportunities for future studies in larger animal species or human subjects.

Poly(adenosine diphosphate ribose) polymerase (PARP) has emerged as an effective therapeutic strategy against cancer that targets the DNA damage repair enzyme. PARP-targeting compounds radiolabeled with an Auger electron-emitting radionuclide can be trapped close to dam-aged DNA in tumor tissue, where high ionizing potential and short range lead Auger electrons to kill cancer cells through the creation of complex DNA damage, with minimal damage to surrounding normal tissue. Here, we report on [123I]CC1, an 123I-labeled PARP inhibitor for radioli-gand therapy of cancer. Methods: Copper-mediated 123I iododeboro-nation of a boronic pinacol ester precursor afforded [123I]CC1. The level and specificity of cell uptake and the therapeutic efficacy of [123I]CC1 were determined in human breast carcinoma, pancreatic adenocarci-noma, and glioblastoma cells. Tumor uptake and tumor growth inhibi-tion of [123I]CC1 were assessed in mice bearing human cancer xenografts (MDA-MB-231, PSN1, and U87MG). Results: In vitro and in vivo studies showed selective uptake of [123I]CC1 in all models. Sig-nificantly reduced clonogenicity, a proxy for tumor growth inhibition by ionizing radiation in vivo, was observed in vitro after treatment with as little as 10 Bq [123I]CC1. Biodistribution at 1 h after intravenous adminis-tration showed PSN1 tumor xenograft uptake of 0.9 6 0.06 percentage injected dose per gram of tissue. Intravenous administration of a rela-tively low amount of [123I]CC1 (3 MBq) was able to significantly inhibit PSN1 xenograft tumor growth but was less effective in xenografts that expressed less PARP. [123I]CC1 did not cause significant toxicity to normal tissues. Conclusion: Taken together, these results show the potential of [123I]CC1 as a radioligand therapy for PARP-expressing cancers.

Objectives Technetium-99m mercapto-acetyl-triglycine ([99mTc]Tc-MAG3) is a radiopharmaceutical diagnostic agent used in nuclear medicine intended for the exploration of nephrological and urological disorders. Patient safety and reliability of this imaging procedure especially depend on the radiochemical purity (RCP) of the [99mTc]Tc-MAG3 preparation. Recently, the Summary of Product Characteristics (SPC) of NephroMAG, a kit dedicated to [99mTc]Tc-MAG3 preparation, proposed a two-strip thin layer chromatography (TLC) based quality control (QC) method. Also, Straub et al recently proposed another TLC based QC method. We sought to evaluate the transferability of these QC methods in our hospital radiopharmacy and compared them to our currently employed TLC method and radio-HPLC (high-pressure liquid chromatography) to select the most appropriate in the context of hospital radiopharmacy. Methods Ten consecutive [99mTc]Tc-MAG3 preparations were controlled using: HPLC combined with a radiodetector (radio-HPLC), a single strip TLC method (method 1) in current use in our centre, a two-strip TLC method described in the SPC (method SPC) and a two-strip TLC method (method 2) described by Straub et al. Quantitative results for the four tested QC methods were measured and compared in terms of RCP (%), sodium pertechnetate ([99mTc]TcO4−) (%) and duration of analysis (min). Results RCP was significantly different between method SPC and radio-HPLC (p<0.001) and method 2 (p<0.001). Also, the percentage of [99mTc]TcO4− was statistically different between the radio-HPLC and the method SPC (p<0.001), but not with the method 1 and method 2 group (p>0.05). The duration of analysis (min) was significantly different between the four QC procedures (p<0.001) with method 2 and method SPC being the quickest. Conclusions Our study showed it is possible to transfer and select a quick and reliable QC method for the preparation of NephroMAG kits in our centre. We therefore advise the widespread use of the method from Straub et al in hospital radiopharmacies.

The radio-iodination of arenes is investigated from organosilane and organogermane precursors using ipso-electrophilic halogenation (IEH). Discovery of a mild base mediated process allows radio-iodination in HFIP (1,1,1,3,3,3-hexafluoro-2-propanol) of either aryl silane or germane, with germanes being more reactive. Clinical potential of arylgermanes as radio-iodination precursors is demonstrated through the labelling of [125 I]IMTO (iodometomidate) and [125 I]MIBG (meta-iodobenzylguanidine) thus offering an alternative to radio-iododestannylation processes using non-toxic precursors.

The 18 kDa translocator protein (TSPO) is a classical marker of neuroinflammation targeted for in vivo molecular imaging. Microglial cells were originally thought to be the only source of TSPO overexpression but astrocytes, neurons and endothelial cells can also up-regulate TSPO depending on the pathological context. This study aims to determine the cellular origin of TSPO overexpression in a simplified model of neuroinflammation and to identify the molecular pathways involved. This is essential to better interpret TSPO molecular imaging in preclinical and clinical settings. We used lentiviral vectors (LV) to overexpress the ciliary neurotrophic factor (CNTF) in the right striatum of 2-month-old Sprague Dawley rats. A LV encoding for β-Galactosidase (LV-LacZ) was used as control. One month later, TSPO expression was measured by single-photon emission computed tomography (SPECT) imaging using [ 125 I]CLINDE. The fluorescence-activated cell sorting to radioligand-treated tissue (FACS-RTT) method was used to quantify TSPO levels in acutely sorted astrocytes, microglia, neurons and endothelial cells. A second cohort was injected with LV-CNTF and a LV encoding suppressor of cytokine signaling 3 (SOCS3), to inhibit the JAK-STAT3 pathway specifically in astrocytes. GFAP and TSPO expressions were quantified by immunofluorescence. We measured a significant increase in TSPO signal in response to CNTF by SPECT imaging. Using FACS-RTT, we observed TSPO overexpression in reactive astrocytes (+ 153 ± 62%) but also in microglia (+ 2088 ± 500%) and neurons (+ 369 ± 117%), accompanied by an increase in TSPO binding sites per cell in those three cell populations. Endothelial cells did not contribute to TSPO signal increase. Importantly, LV-SOCS3 reduced CNTF-induced astrocyte reactivity and decreased global TSPO immunoreactivity (-71% ± 30%), suggesting that TSPO overexpression is primarily mediated by reactive astrocytes. Overall, this study reveals that CNTF induces TSPO in multiple cell types in the rat striatum, through the JAK2-STAT3 pathway in astrocytes, identifying this cell type as the primary mediator of CNTF effects neuroinflammatory processes. Our results highlight the difficulty to interpret TSPO imaging in term of cellular origin without addition cellular analysis by FACS-RTT or quantitative immunostainings. Consequently, TSPO should only be used as a global marker of neuroinflammation.

A novel radioiodination method is developed using carboxylic acids as radiolabeling precursors. This method involves decarboxylation and organogold(I) intermediate formation, enabling efficient radioiodination of (hetero)arenes and cinnamic and phenylpropiolic acids. Additionally, we demonstrated the prolonged stability of crude gold(I) organometallic compounds, showcasing their enduring radiolabeling capabilities.

Purpose Radiopharmaceuticals targeting poly(ADP-ribose) polymerase (PARP) have emerged as promising agents for cancer diagnosis and therapy. PARP enzymes are expressed in both cancerous and normal tissue. Hence, the injected mass, molar activity and potential pharmacological effects are important considerations for the use of radiolabelled PARP inhibitors for diagnostic and radionuclide therapeutic applications. Here, we performed a systematic evaluation by varying the molar activity of [ 18 F]olaparib and the injected mass of [ Total F]olaparib to investigate the effects on tumour and normal tissue uptake in two subcutaneous human glioblastoma xenograft models. Methods [ 18 F]Olaparib uptake was evaluated in the human glioblastoma models: in vitro on U251MG and U87MG cell lines, and in vivo on tumour xenograft-bearing mice, after administration of [ Total F]olaparib (varying injected mass: 0.04–8.0 µg, and molar activity: 1–320 GBq/μmol). Results Selective uptake of [ 18 F]olaparib was demonstrated in both models. Tumour uptake was found to be dependent on the injected mass of [ Total F]olaparib (µg) but not the molar activity. An injected mass of 1 μg resulted in the highest tumour uptake (up to 6.9 ± 1.3%ID/g), independent of the molar activity. In comparison, both the lower and higher injected masses of [ Total F]olaparib resulted in lower relative tumour uptake (%ID/g; P < 0.05). Ex vivo analysis of U87MG xenograft sections showed that the heterogeneity in [ 18 F]olaparib intratumoural uptake correlated with PARP1 expression. Substantial upregulation of PARP1-3 expression was observed after administration of [ Total F]olaparib (> 0.5 µg). Conclusion Our findings show that the injected mass of [ Total F]olaparib has significant effects on tumour uptake. Moderate injected masses of PARP inhibitor-derived radiopharmaceuticals may lead to improved relative tumour uptake and tumour-to-background ratio for cancer diagnosis and radionuclide therapy.

Positron emission tomography (PET) is an important non-invasive tool to help guide the drug discovery and development process. Positron-emitting–radiolabeled drug candidates represent an important tool for drug hunters to gain insight into a drug's biodistribution and target engagement of exploratory biologic targets of interest. Recently, there have been several drug candidates that incorporate an acryloyl functional group due to their ability to form a covalent bond within the biological target of interest through Michael addition. Methods to incorporate a carbon-11 radionuclide into acrylamide derivatives remain challenging given the reactive nature of this moiety. Herein, we report the improved radiosynthesis of carbon-11–containing acrylamide drug candidates, [11C]ibrutinib, [11C]tolebrutinib, and [11C]evobrutinib, using [11C]CO and a novel “in-loop” 11C-carbonylation reaction. [11C]Ibrutinib, [11C]tolebrutinib, and [11C]evobrutinib were reliably synthesized, generating 2.2-7.1 GBq of these radiopharmaceuticals in radiochemical yields ranging from 3.3 to 12.8% (non-decay corrected; relative to starting [11C]CO2) and molar activities of 281-500 GBq/μmol (7.5-13.5 Ci/μmol), respectively. This study highlights an improved method for incorporating carbon-11 into acrylamide drug candidates using [11C]CO within an HPLC loop suitable for clinical translation using simple modifications of standard automated synthesis modules used for cGMP manufacture of PET radioligands.

Abstract Preclinical studies have recently evaluated the impact of low-dose brain radiation therapy (LD-RT) in animal models of Alzheimer’s disease (AD) showing anti-amyloid and anti-inflammatory effects of this treatment. Its effectiveness varied, however, depending on the LD-RT protocol used and the stage when the treatment was applied. In this study, we aimed to evaluate the therapeutic potential of 10 Gy delivered in five daily fractions of 2 Gy (a protocol previously shown to induce an improvement of cognitive performances) in 9-month-old TgF344-AD rats, modeling at a pre-symptomatic stage of the disease. We showed that at an early stage, LD-RT was able to lower levels of the 18-kDa translocator protein (TSPO)-mediated neuroinflammation to normal ranges in addition to the secreted CLUSTERIN, another inflammatory protein also involved in Aβ aggregation. In addition, we demonstrated that LD-RT reduces all amyloid forms (~ − 60 to − 80%, P < 0.01; soluble and aggregated forms of Aβ40, Aβ42, and Aβoligomers). Interestingly, we showed for the first time that sAPPα levels were improved by the treatment, showing a higher activation of the non-amyloidogenic pathway, that could favor neuronal survival. The current evidence confirms the capacity of LD-RT to successfully modulate two pathological hallmarks of AD, namely amyloid and neuroinflammation, when applied before symptoms onset.

This review lists the most important radiotracers described so far for imaging the central serotoninergic system. Single-photon emission computed tomography and positron emission tomography radiotracers are reviewed and critically discussed for each receptor.

The first example of a cryptophazane, a cryptophane functionalized with a nitrogen atom replacing one of the methylene bridges, is obtained with a 28 % overall yield over 8 steps, through the preparation of a C1 -symmetrical aza-cyclotriveratrylene (aza-CTV). Herein, we demonstrate that the introduction of a nitrogen atom on this part of the cryptophane core enhances the solubility in organic media of both the cryptophane and the synthetic intermediates, while presenting the same conformation as known cryptophanes. Cryptophazane was prepared on a multigram scale and easily functionalized. We also investigated its ability to encapsulate xenon atoms using hyperpolarized 129 Xe (HP 129 Xe) NMR spectroscopy. We found that both its affinity and exchange kinetics were in the appropriate range for applications in 129 Xe magnetic resonance imaging (MRI). Combined with the wide range of possible functionalization, this makes cryptophazane an excellent candidate for targeted HP 129 Xe MRI.