An Improved HPLC Separation Method for TSPO Radioligand [11C]ER176 Clinical Production.

Mitochondrial membrane translocator protein 18 kDa (TSPO) expression is increased in activated microglia, established as a plausible target of neuroinflammation imaging. [11C]ER176, specifically binding to TSPO, has been developed as the third generation of radioligand for PET imaging of TSPO, which showed the potential in better quantifying neuroinflammation than its predecessors. In the current study, we developed an automated radiosynthesis with an improved HPLC purification method for [11C]ER176 clinical production. The improved HPLC separation was integrated into the automated production of [11C]ER176 using a reverse phase semi-preparative HPLC column with an isocratic pump and the mixture of methanol and 50 mM ammonium acetate as the mobile phase. The fraction corresponding to [11C]ER176 was collected around 8.5-9.0 min without the risk of getting contaminations from nearby impurities. The automated production process took about 30 min after end of bombardment (EOB) and the quality of the final product [11C]ER176 met all specifications for clinical use based on current US Pharmacopeia and FDA CGMP requirements.

Radiosynthesis and Preliminary Evaluation of [11C]SSI-4 for the Positron Emission Tomography Imaging of Stearoyl CoA Desaturase 1.

Stearoyl CoA desaturase 1 (SCD1) is the rate-limiting enzyme for converting saturated fatty acids (SFAs) into monounsaturated fatty acids (MUFAs) and plays a key role in endogenous (de novo) fatty acid metabolism. Given that this pathway is broadly upregulated across many tumor types with an aggressive phenotype, SCD1 has emerged as a compelling target for cancer imaging and therapy. The ligand 2-(4-(2-chlorophenoxy)piperidine-1-carboxamido)-N-methylisonicotinamide (SSI-4) was identified as a potent and highly specific SCD1 inhibitor with a strong binding affinity for SCD1 at our laboratory. We herein report the radiosynthesis of [11C]SSI-4 and the preliminary biological evaluation including in vivo PET imaging of SCD1 in a human tumor xenograft model. Radiotracer [11C]SSI-4 was labeled at the carbamide position via the direct [11C]CO2 fixation on the Synthra MeIplus module in high molar activity and good radiochemical yield. In vitro cell uptake assays were performed with three hepatocellular carcinoma (HCC) cell lines and three renal cell carcinoma (RCC) cell lines. Additionally, in vivo small animal PET/CT imaging with [11C]SSI-4 and the biodistribution were carried out in a mouse model bearing HCC xenografts. Radiotracer [11C]SSI-4 afforded a 4.14 ± 0.44% (decay uncorrected, n = 10) radiochemical yield based on starting [11]CO2 radioactivity. The [11C]SSI-4 radiosynthesis time including HPLC purification and SPE formulation was 25 min from the end of bombardment to the end of synthesis (EOS). The radiochemical purity of [11C]SSI-4 was 98.45 ± 1.43% (n = 10) with a molar activity of 225.82 ± 33.54 GBq/µmol (6.10 ± 0.91 Ci/µmol) at the EOS. In vitro cell uptake study indicated all SSI-4 responsive HCC and RCC cell line uptakes demonstrate specific uptake and are blocked by standard compound SSI-4. Preliminary small animal PET/CT imaging study showed high specific uptake and block of [11C]SSI-4 uptake with co-injection of cold SSI-4 in high SCD1-expressing organs including lacrimal gland, brown fat, liver, and tumor. In summary, novel radiotracer [11C]SSI-4 was rapidly and automatedly radiosynthesized by direct [11C]CO2 fixation. Our preliminary biological evaluation results suggest [11C]SSI-4 could be a promising radiotracer for PET imaging of SCD1 overexpressing tumor tissues.

Palladium (II), platinum (II) and silver (I) complexes with oxazolines: Their synthesis, characterization, DFT calculation, molecular docking and antitumour effects.

Six new Pd(II), Pt(II) and Ag(I) complexes, (1);{Pd (L1)]2C6H4}2Cl4} (2); Pt(L2)(DMSO)Cl; 3; {PtL5]2C6H4}2·PhCOO-⋅11NO3-; 4; {[Pt(L4)]2C6H4}; the binuclear cyclometalated complex the polymer chain (5); {[PtL5]C6H4}·NO3-}; and the polymeric silver species (6); Zn(L6)2·AgNO3·CHCl3 were synthesized and thoroughly characterized using X-ray diffraction and spectroscopic techniques (L1=(S,S)-1,4-i-PrOx]2C6H4}2Cl4, L2=Di(2,2-bis(4R-isopropyl-4,5-dihydro-oxazol-2-yl)acetonitrile) zinc (II) (BR1);L3= 1,4-bis(4R-benzyl-4,5-dihydro-oxazol-2-yl)benzene (AR2); L4= 1,4-bis(4R-benzyl-4,5-dihydro-oxazol-2-yl)benzene，L5=1,4-bis(4R-benzyl-4,5-dihydro-oxazol-2-yl)-benzene，L6=Di(2,2-bis(4S-isopropyl-4,5-dihydrooxazol-2-yl)acetonitrile) zinc (II). Complexes 1-6 showed cytotoxic effects against human tumour cell lines, including a multidrug-resistant subline. Oxazoline and Pd complex 1 induced apoptosis in A549 cells. DFT calculations were also performed to exhibit the excellent bioactivity of complex 1 against A549, MDA-MB-231, and KB cells. Complex 1, with the best docking score and a stable interaction network within the binding site of the G-quadruplex, could stably interact with the G-quadruplex. Additionally, complex 1 was further used in the animal experiment of human lung adenocarcinoma cells in nude mice. By comparing with the model control group, the tumour volume, relative tumour volume and relative tumour proliferation rate T/C decreased significantly in the cisplatin group and compound 1 (complex 1) group.

Direct C-H Radiocyanation of Arenes via Organic Photoredox Catalysis.

Innovative labeling methods to incorporate the short-lived positron emitter carbon-11(11C) into bioactive molecules are attractive for positron emission tomography (PET) tracer discovery. Herein, we report a direct C-H radiocyanation method that incorporates [11C]cyanide (11CN-) to a series of functional electron-rich arenes via photoredox catalysis. This photoredox-mediated radiocyanation can proceed in an aerobic environment and is not moisture sensitive, which allows for ease of reaction setup and for scalable synthesis of 11C-aryl nitriles from readily available precursors.

Arene radiofluorination enabled by photoredox-mediated halide interconversion.

Positron emission tomography (PET) is a powerful imaging technology that can visualize and measure metabolic processes in vivo and/or obtain unique information about drug candidates. The identification of new and improved molecular probes plays a critical role in PET, but its progress is somewhat limited due to the lack of efficient and simple labelling methods to modify biologically active small molecules and/or drugs. Current methods to radiofluorinate unactivated arenes are still relatively limited, especially in a simple and site-selective way. Here we disclose a method for constructing C-18F bonds through direct halide/18F conversion in electron-rich halo(hetero)arenes. [18F]F- is introduced into a broad spectrum of readily available aryl halide precursors in a site-selective manner under mild photoredox conditions. Notably, our direct 19F/18F exchange method enables rapid PET probe diversification through the preparation and evaluation of an [18F]-labelled O-methyl tyrosine library. This strategy also results in the high-yielding synthesis of the widely used PET agent L-[18F]FDOPA from a readily available L-FDOPA analogue.

Scaffold Hopping-Driven Optimization of 4-(Quinazolin-4-yl)-3,4-dihydroquinoxalin-2(1H)-ones as Novel Tubulin Inhibitors.

Scaffold hopping-driven lead optimizations were performed based on our prior lead 7-methoxy-4-(2-methylquinazolin-4-yl)-3,4-dihydroquinoxalin-2(1H)-one (2a) by C-ring expansion and isometric replacement of the A/B-ring, successively, aimed at finding new potential alternative drug candidates with different scaffold(s), high antitumor activity, and other improved properties to replace prior, once promising drug candidates that failed in further studies. Two series of new compounds 7 (a-d) and 13 (a-j) were synthesized and evaluated for antitumor activity, leading to the discovery of three highly potent compounds 13c, 13d, and 13e with different scaffolds. They exhibited similar high antitumor activity with single digital low nanomolar GI50 values (4.6-9.6 nM) in cellular assays, comparable to lead 2a, clinical drug candidate CA-4, and paclitaxel in the same assays. Further biological evaluations identified new active compounds as tubulin polymerization inhibitors targeting the colchicine binding site. Moreover, 13d showed better aqueous solubility than 2a and a similar log P value.

Structure-activity relationships and evaluation of esterified diterpenoid alkaloid derivatives as antiproliferative agents.

Diterpenoid alkaloids with remarkable chemical properties and biological activities are frequently found in plants of the genera Aconitum, Delphinium, and Garrya. However, little information has been reported on the antiproliferative effects of the diterpenoid alkaloid constituents of Aconitum and Delphinium plants. C-1 and 14 esterifications of delcosine (1) were carried out to provide 39 new diterpenoid alkaloid derivatives (3-14, 16-29, 3a-7a, 9a, 13a, 13b, 14a, 14b, 16a, 17a, 24a, 35a). Selected compounds (3-14, 16-29, 3a-7a, 9a, 13a, 13b, 14a, 14b, 16a, 17a, 24a, 35a) were evaluated for antiproliferative activity against three to five human tumor cell lines including triple-negative breast cancer (TNBC) and P-glycoprotein (P-gp) overexpressing multidrug-resistant (MDR) subline. Several newly synthesized delcosine derivatives (6, 7, 13, 13a, 13b) showed substantial suppressive effects against all human tumor cell lines tested. In contrast, the natural alkaloids (1, 31, 33) showed no effect. Most of the active compounds were delcosine derivatives with two specific substitution patterns-C-1 and C-1,14. In particular, 1-acyldelcosine derivative (5-7) displayed more potency than 1,14-diacyldelcosine derivatives (5a-7a). These acylated alkaloid derivatives caused accumulation of TNBC cells at sub-G1 within 24 h. 1-Acylation of 1 appears to be critical for producing antiproliferative activity in this alkaloid class and a means to provide promising new leads for further development into antitumor agents.

Design, synthesis and evaluation of antiproliferative activity of fluorinated betulinic acid.

Betulinic acid (BA), a pentacyclic triterpenoid, exhibits broad spectrum antiproliferative activity, but generally with only modest potency. To improve BA's pharmacological properties, fluorine was introduced as a single atom at C-2, creating two diastereomers, or in a trifluoromethyl group at C-3. We evaluated the impact of these groups on antiproliferative activity against five human tumor cell lines. A racemic 2-F-BA (compound 6) showed significantly improved antiproliferative activity, while each diastereomer exhibited similar effects. We also demonstrated that 2-F-BA is a topoisomerase (Topo) I and IIα dual inhibitor in cell-based and cell-free assays. A hypothetical mode of binding to the Topo I-DNA suggested a difference between the hydrogen bonding of BA and 2-F-BA to DNA, which may account for the difference in bioactivity against Topo I.

Improved and optimized one-pot method for N-succinimidyl-4-[(18)F]fluorobenzoate ([(18)F]SFB) synthesis using microwaves.

N-Succinimidyl-4-[(18)F]fluorobenzoate ([(18)F]SFB) is a potential prosthetic agent for novel tracer development in positron emission tomography (PET). Previously, we reported a microwave-assisted one-pot synthesis of [(18)F]SFB with high efficacy. Herein, we reveal an improved and optimized approach based on this former model for producing [(18)F]SFB. With optimized approaches, the entire protocol can be completed within 25min, and [(18)F]SFB is generated in satisfactory quality for direct use without further purification via high-performance liquid chromatography.