A Newly Developed HPLC-UV/Vis Method Using Chemical Derivatization with 2-Naphthalenethiol for Quantitation of Sulforaphane in Rat Plasma.

Sulforaphane (SFN), a naturally occurring isothiocyanate, has received significant attention because of its ability to modulate multiple biological functions, including anti-carcinogenic properties. However, currently available analytical methods based on high-performance liquid chromatography (HPLC)-UV/Vis for the quantification of SFN have a number of limitations, e.g., low UV absorbance, sensitivity, or accuracy, due to the lack of a chromophore for spectrometric detection. Therefore, we here employed the analytical derivatization procedure using 2-naphthalenethiol (2-NT) to improve the detectability of SFN, followed by HPLC separation and quantification with UV/Vis detection. The optimal derivatization conditions were carried out with 0.3 M of 2-NT in acetonitrile with phosphate buffer (pH 7.4) by incubation at 37 °C for 60 min. Separation was performed in reverse phase mode using a Kinetex C18 column (150 mm × 4.6 mm, 5 µm) at a flow rate of 1 mL/min, with 0.1% formic acid as a mobile phase A, and acetonitrile/0.1% formic acid solution as a mobile phase B with a gradient elution, with a detection wavelength of 234 nm. The method was validated over a linear range of 10-2000 ng/mL with a correlation of determination (R2) > 0.999 using weighted linear regression analysis. The intra- and inter-assay accuracy (% of nominal value) and precision (% of relative standard deviation) were within ±10 and <15%, respectively. Moreover, the specificity, recovery, matrix effect, process efficiency, and short-term and long-term stabilities of this method were within acceptable limits. Finally, we applied this method for studying in vivo pharmacokinetics (PK) following oral administration of SFN at doses of 10 or 20 mg/kg. The Cmax (µg/mL), Tmax (hour), and AUC0-12h (µg·h/mL) of each oral dose were 0.92, 1.99, and 4.88 and 1.67, 1.00, and 9.85, respectively. Overall, the proposed analytical method proved to be reliable and applicable for quantification of SFN in biological samples.

Sulforaphane Bioavailability and Effects on Blood Pressure in Women with Pregnancy Hypertension.

Sulforaphane, an isothiocyanate found in cruciferous vegetables such as broccoli, shows promise as an adjuvant therapy for preeclampsia. To inform future clinical trials, we set out to determine the bioavailability of sulforaphane in non-pregnant and preeclamptic women. In six healthy female volunteers, we performed a crossover trial to compare the bioavailability of sulforaphane and metabolites afforded by an activated and non-activated broccoli extract preparation. We then undertook a dose escalation study of the activated broccoli extract in 12 women with pregnancy hypertension. In non-pregnant women, an equivalent dose of activated broccoli extract gave higher levels of sulforaphane and metabolites than a non-activated extract (p < 0.0001) and greater area under the curve (AUC) (3559 nM vs. 2172 nM, p = 0.03). Compared to non-pregnant women, in women with preeclampsia, the same dose of activated extract gave lower levels of total metabolites (p < 0.000) and AUC (3559 nM vs. 1653 nM, p = 0.007). Doubling the dose of the activated extract in women with preeclampsia doubled levels of sulforaphane and metabolites (p = 0.02) and AUC (1653 nM vs. 3333 nM, p = 0.02). In women with preeclampsia, activated broccoli extract was associated with modest decreases in diastolic blood pressure (p = 0.05) and circulating levels of sFlt-1 (p = 0.0002). A myrosinase-activated sulforaphane formulation affords better sulforaphane bioavailability than a non-activated formulation. Higher doses of sulforaphane are required to achieve likely effective doses in pregnant women than in non-pregnant women. Sulforaphane may improve endothelial function and blood pressure in women with pregnancy hypertension.

Application of sulfoximines in medicinal chemistry from 2013 to 2020.

In recent years, interest in sulfoximine chemistry has been greatly increased. For example, at least three sulfoximine containing drugs BAY 1143572, BAY 1251152 and AZD6738 have entered the clinic. Despite the increasing interest in sulfoximines and their chemistry, the routine application of this structure in drug discovery is still hampered due to limited experience in physicochemical and in vitro parameters of sulfoximines. Therefore, we reviewed all relevant articles from 2013 to the present in terms of potency and pharmacokinetic properties in order to support the addition of the sulfoximine component to the toolbox of medicinal chemists.

Discovery of Sulforaphane as a Potent BACE1 Inhibitor Based on Kinetics and Computational Studies.

BACE1 is the rate-limiting enzyme involved in the production and deposition of ß-amyloid (Aß). Since neurotoxic Aß plays a critical role in Alzheimer's disease (AD) pathogenesis, BACE1 has emerged as a key target for preventing AD. In the present study, the potential of sulforaphane, an isothiocyanate found in cruciferous vegetables, as a BACE1 inhibitor has been investigated. Sulforaphane exhibited six times more potent activity against BACE1 compared to well-known positive controls including resveratrol and quercetin. Sulforaphane presented selective and non-competitive BACE1 inhibitory activity with low off-target inhibition of BACE2 and other aspartic and serine proteases. In addition, sulforaphane presented negative binding energy, suggesting that the compound had a high affinity for BACE1. It interacted with locations other than the active binding sites of BACE1 through van der Waals forces. Overall, sulforaphane appeared to be a promising candidate with potent and selective BACE1 inhibitory properties that play an important role in AD prevention.

Development and validation of a high throughput bioanalytical UPLC-MS/MS method for simultaneous determination of tamoxifen and sulphoraphane in rat plasma: Application to an oral pharmacokinetic study.

Tamoxifen (TAM) is the choice of a drug approved by the Food and Drug Administration (FDA) for the treatment of estrogen-positive receptor (ER+) breast cancer. Sulphoraphane (SFN), a natural plant antioxidant compound, also acts on estrogen-positive breast cancer receptor. Thus, a combination of TAM with SFN is preferred as it helps to minimize the drug-related toxicity and increases the therapeutic efficacy by providing synergistic anticancer effects of both drugs. In the present study, a new simple, sensitive, precise, and selective UPLC-MS/MS method was developed for the simultaneous quantification of tamoxifen and sulphoraphane using propranolol as an internal standard (IS) in rat plasma. Chromatographic separation was achieved on reverse phase Acquity UPLC BEH C18 column (50 mm × 2.1 mm, i.d., 1.7 µm) with an isocratic mobile phase composed of solvent A (0.1% formic acid in acetonitrile) and B (0.1% formic acid in water) (80:20, v/v) at a flow-rate of 0.4 mL/min. The detection and quantification of analytes was performed on Waters ZsprayTM Xevo TQD using selected-ion monitoring operated under a positive electrospray ionization mode. The transitions were m/z = 372.0 [M+H]+ → 71.92 for tamoxifen, m/z = 177.9 [M+H]+ → 113.9 for sulphoraphane and m/z = 260.3 [M+H]+ → 116.1 for propranolol. The method was linear over the concentration range of 8-500 ng/mL (r2 = 0.9996) for tamoxifen, 30-2000 ng/mL (r2 = 0.9998) for sulphoraphane with insignificant matrix effect and high extraction recovery on spiked quality control (QC) samples. The intra- and inter-batch precisions and accuracy were within the acceptable limits, and both the analytes were found to be stable throughout the short term, long term and freeze thaw stability studies. The validated method was successfully applied for the simultaneous estimation of TAM and SFN in an oral pharmacokinetic study in female Wistar rats. This developed UPLC-MS/MS method could be a valuable tool for future pharmacokinetic interaction, therapeutic drug monitoring and pharmacokinetic characterization of novel formulations.

In vivo pharmacokinetic study and oral glucose tolerance test of sulfoxide analogs of GPR40 agonist TAK-875.

TAK-875 (compound 1) was the only GPR40 agonist with promising oral glucose-lowering effect, which entered phase III clinical trials. In previous studies, we successfully synthesized the TAK-875 sulfoxide analog 2, which was further separated to optically pure compounds 3 (S, S, 100.0% de) and 4 (R, S, 100.0% de). In vitro biological evaluation revealed that the sulfoxide analogs 3 and 4 possessed comparable GPR40 agonist activity to TAK-875. Herein, in order to further evaluate the druglikeness of TAK-875 sulfoxide analogs, the pharmacokinetic properties of compounds 2, 3, and 4 in rats were investigated and compared with that of TAK-875. The results showed that sulfoxide (2, 3, and 4) and sulfone (TAK-875) could be converted into each other in different degrees in vivo. Interestingly, compound 3 showed higher drug exposure calculated by the AUC sum of sulfoxide and sulfone in plasma than TAK-875, 2 and 4. In order to further investigate the in vivo glucose-lowering potency of sulfoxide analogs, asymmetric synthesis was carried out and led to two sulfoxides with moderate de values, 5 (S, S, 66.4% de) and 6 (R, S, 71.0% de). The following oral glucose tolerance test (OGTT) in rats showed that 5 (S, S, 66.4% de) had stronger glucose-lowering effect in vivo than 6 (R, S, 71.0% de) and TAK-875, which could be partly rationalized by the superior pharmacokinetic property of sulfoxide 3 (the main component of 5) relative to sulfoxide 4 (the main component of 6) and TAK-875.

Development of a liquid chromatography/tandem-mass spectrometry assay for the simultaneous determination of teneligliptin and its active metabolite teneligliptin sulfoxide in human plasma.

Teneligliptin is a recently developed dipeptidyl peptidase-4 (DPP-4) inhibitor for the treatment of type 2 diabetes mellitus. To study simultaneous pharmacokinetics of teneligliptin and its major active metabolite, teneligliptin sulfoxide in human plasma, we developed and validated a LC-MS/MS method. The analytes were detected in the positive mode using multiple reaction monitoring (teneligliptin: m/z 427.2→243.1; teneligliptin-d8 : m/z 435.2→251.3; teneligliptin sulfoxide: m/z 443.2→68.2). The method demonstrated accuracy, precision, and linearity over the concentration range of 5 to 1000 ng/mL for teneligliptin and 2.5 to 500 ng/mL for teneligliptin sulfoxide. The developed method is the first fully validated method capable of simultaneous determination of teneligliptin and its active metabolite, teneligliptin sulfoxide in plasma. The suitability of the method was successfully demonstrated in terms of quantification of teneligliptin and teneligliptin sulfoxide pharmacokinetics in plasma samples collected from healthy volunteers. The measurement of plasma metabolite/parent ratio of teneligliptin was feasible by this method.

Total determination of triclabendazole and its metabolites in bovine tissues using liquid chromatography-tandem mass spectrometry.

A reliable LC-MS/MS analytical method for the determination of residual triclabendazole and its principal metabolites (triclabendazole sulfoxide, triclabendazole sulfone and keto-triclabendazole) in bovine tissues was developed, in which triclabendazole and its metabolites are oxidized to keto-triclabendazole as a marker residue. The method involves sample digestion with hot sodium hydroxide, thus releasing the bound residues of various triclabendazole metabolites in bovine tissues. The target compounds are extracted from the digest mixture with ethyl acetate, defatted by liquid-liquid partitioning using n-hexane and acetonitrile, then oxidized with hydrogen peroxide in a mixture of ethanol and acetic acid. The reaction mixture is cleaned up using a strong cation exchange cartridge (Oasis MCX) and the analytes are quantified using LC-MS/MS. The optimal conditions for the complete oxidation of triclabendazole and its metabolites to keto-triclabendazole are an incubation time of 16 h and a temperature of 90 °C. The developed method was evaluated using three bovine samples: muscle, fat, and liver. Samples were spiked with triclabendazole and its principal metabolites at 0.01 mg/kg and at the Japanese Maximum Residue Limits (MRLs) established for each sample. The validation results show excellent recoveries (81-102%) and precision (<10%) for all target compounds. The limit of quantification (S/N ≥ 10) of the developed method is 0.01 mg/kg. These results suggest the developed method is applicable to quantifying residual triclabendazole in bovine tissues in compliance with the MRLs established by the Codex Alimentarius and EU and Japanese regulations, and thus the proposed method will be a useful tool for the regulatory monitoring of residual triclabendazole and its metabolites.

Enantioseparation, Stereochemical Assignment and Chiral Recognition Mechanism of Sulfoxide-Containing Drugs.

The distinct pharmacodynamic and pharmacokinetic properties of enantiopure sulfoxide drugs have stimulated us to systematically investigate their chiral separation, stereochemical assignment, and chiral recognition mechanism. Herein, four clinically widely-used sulfoxide drugs were chosen and optically resolved on various chiral stationary phases (CSPs). Theoretical simulations including electronic circular dichroism (ECD) calculation and molecular docking were adopted to assign the stereochemistry and reveal the underlying chiral recognition mechanism. Our results showed that the sequence of calculated mean binding energies between each pair of enantiomers and CSP matched exactly with experimentally observed enantiomeric elution order (EEO). It was also found that the length of hydrogen bond might contribute dominantly the interaction between two enantiomers and CSP. We hope our study could provide a fresh perspective to explore the stereochemistry and chiral recognition mechanism of chiral drugs.

Discovery and Characterization of AZD6738, a Potent Inhibitor of Ataxia Telangiectasia Mutated and Rad3 Related (ATR) Kinase with Application as an Anticancer Agent.

The kinase ataxia telangiectasia mutated and rad3 related (ATR) is a key regulator of the DNA-damage response and the apical kinase which orchestrates the cellular processes that repair stalled replication forks (replication stress) and associated DNA double-strand breaks. Inhibition of repair pathways mediated by ATR in a context where alternative pathways are less active is expected to aid clinical response by increasing replication stress. Here we describe the development of the clinical candidate 2 (AZD6738), a potent and selective sulfoximine morpholinopyrimidine ATR inhibitor with excellent preclinical physicochemical and pharmacokinetic (PK) characteristics. Compound 2 was developed improving aqueous solubility and eliminating CYP3A4 time-dependent inhibition starting from the earlier described inhibitor 1 (AZ20). The clinical candidate 2 has favorable human PK suitable for once or twice daily dosing and achieves biologically effective exposure at moderate doses. Compound 2 is currently being tested in multiple phase I/II trials as an anticancer agent.

Investigating Sulfoxide-to-Sulfone Conversion as a Prodrug Strategy for a Phosphatidylinositol 4-Kinase Inhibitor in a Humanized Mouse Model of Malaria.

The in vivo antimalarial efficacies of two phosphatidylinositol 4-kinase (PI4K) inhibitors, a 3,5-diaryl-2-aminopyrazine sulfoxide and its corresponding sulfone metabolite, were evaluated in the NOD-scid IL2Rγnull (NSG) murine malaria disease model of Plasmodium falciparum infection. We hypothesized that the sulfoxide would serve as a more soluble prodrug for the sulfone, which would lead to improved drug exposure with oral dosing. Both compounds had similar efficacy (90% effective dose [ED90], 0.1 mg kg-1 of body weight) across a quadruple-dose regimen. Pharmacokinetic profiling revealed rapid sulfoxide clearance via conversion to sulfone, with sulfone identified as the major active metabolite. When the sulfoxide was dosed, the exposure of the sulfone achieved was as much as 2.9-fold higher than when the sulfone was directly dosed, thereby demonstrating that the sulfoxide served as an effective prodrug for the treatment of malaria.

Phase Ib/II study of the pan-cyclin-dependent kinase inhibitor roniciclib in combination with chemotherapy in patients with extensive-disease small-cell lung cancer.

OBJECTIVES: This phase Ib/II study evaluated safety, pharmacokinetics, maximum tolerated dose (MTD), and efficacy of the pan-cyclin-dependent kinase inhibitor roniciclib with cisplatin-etoposide (CIS-ETOP) or carboplatin-etoposide (CARBO-ETOP) in patients with extensive-disease small-cell lung cancer (ED-SCLC). PATIENTS AND METHODS: In this open-label, non-randomized study, patients with previously untreated ED-SCLC received roniciclib twice daily (BID) in a 3 days on/4 days off schedule. Cisplatin 75 mg/m2 or carboplatin (AUC5) dose was administered on day 1, and etoposide 100 mg/m2 on days 1-3, of 21-day cycles. Phase Ib used a dose-escalation design to define the MTD for phase II. Pharmacokinetics were assessed. RESULTS: Forty-three patients received treatment (roniciclib 2.5 mg BID [+ CARBO-ETOP, n = 4; + CIS-ETOP, n = 3] and roniciclib 5 mg BID [+ CARBO-ETOP, n = 24; + CIS-ETOP, n = 12]). The MTD of roniciclib was 5 mg BID with CARBO-ETOP or CIS-ETOP. Common adverse events were nausea (90.7%) and vomiting (69.8%). Roniciclib was readily absorbed following oral administration at the MTD (median tmax 0.5-1 h), with a 30-40% reduction in exposure when co-administered with CARBO-ETOP or CIS-ETOP; administration of roniciclib had no effect on etoposide or platinum pharmacokinetics. The response rate was 81.4% (35/43) overall and 86.1% (31/36) in the pooled roniciclib 5 mg BID population (all partial responses). CONCLUSION: Roniciclib co-administered with chemotherapy in patients with ED-SCLC demonstrated tolerability, acceptable pharmacokinetics, and promising efficacy. An observed safety signal in a related phase II study resulted in discontinuation of the present study and termination of further roniciclib development.

ATR kinase inhibitor AZD6738 potentiates CD8+ T cell-dependent antitumor activity following radiation.

DNA-damaging chemotherapy and radiation therapy are integrated into the treatment paradigm of the majority of cancer patients. Recently, immunotherapy that targets the immunosuppressive interaction between programmed death 1 (PD-1) and its ligand PD-L1 has been approved for malignancies including non-small cell lung cancer, melanoma, and head and neck squamous cell carcinoma. ATR is a DNA damage-signaling kinase activated at damaged replication forks, and ATR kinase inhibitors potentiate the cytotoxicity of DNA-damaging chemotherapies. We show here that the ATR kinase inhibitor AZD6738 combines with conformal radiation therapy to attenuate radiation-induced CD8+ T cell exhaustion and potentiate CD8+ T cell activity in mouse models of Kras-mutant cancer. Mechanistically, AZD6738 blocks radiation-induced PD-L1 upregulation on tumor cells and dramatically decreases the number of tumor-infiltrating Tregs. Remarkably, AZD6738 combines with conformal radiation therapy to generate immunologic memory in complete responder mice. Our work raises the possibility that a single pharmacologic agent may enhance the cytotoxic effects of radiation while concurrently potentiating radiation-induced antitumor immune responses.

Pharmacologic ATM but not ATR kinase inhibition abrogates p21-dependent G1 arrest and promotes gastrointestinal syndrome after total body irradiation.

We show that ATM kinase inhibition using AZ31 prior to 9 or 9.25 Gy total body irradiation (TBI) reduced median time to moribund in mice to 8 days. ATR kinase inhibition using AZD6738 prior to TBI did not reduce median time to moribund. The striking finding associated with ATM inhibition prior to TBI was increased crypt loss within the intestine epithelium. ATM inhibition reduced upregulation of p21, an inhibitor of cyclin-dependent kinases, and blocked G1 arrest after TBI thereby increasing the number of S phase cells in crypts in wild-type but not Cdkn1a(p21CIP/WAF1)-/- mice. In contrast, ATR inhibition increased upregulation of p21 after TBI. Thus, ATM activity is essential for p21-dependent arrest while ATR inhibition may potentiate arrest in crypt cells after TBI. Nevertheless, ATM inhibition reduced median time to moribund in Cdkn1a(p21CIP/WAF1)-/- mice after TBI. ATM inhibition also increased cell death in crypts at 4 h in Cdkn1a(p21CIP/WAF1)-/-, earlier than at 24 h in wild-type mice after TBI. In contrast, ATR inhibition decreased cell death in crypts in Cdkn1a(p21CIP/WAF1)-/- mice at 4 h after TBI. We conclude that ATM activity is essential for p21-dependent and p21-independent mechanisms that radioprotect intestinal crypts and that ATM inhibition promotes GI syndrome after TBI.

Simultaneous determination of sulfur mustard and related oxidation products by isotope-dilution LC-MS/MS method coupled with a chemical conversion.

Sulfur mustard (SM) is a highly reactive alkylating vesicant with high toxicity and complicated metabolism, the in vivo profile of its oxidation metabolism is not still fully known and urgently needs to be clarified well. In this work, an isotope-dilution high performance liquid chromatography-tandem mass spectrometric method coupled with chemical conversion was developed for the simultaneous quantification of SM and its oxidation products, i.e., mustard sulfoxide (SMO) and mustard sulfone (SMO2). The accurate measurement of SM and its oxidation products with high reaction activity was achived via the method of chemical conversion of 2-(3,5-bis(mercaptomethyl)phenoxy) acetic acid into stable derivative products. Method validation was performed in whole blood matrix, the linear range of the method was between 0.2 and 1000µg/L with correlation coefficients (r(2))>0.99, and the lower limits of quantification for SM, SMO and SMO2 were 1, 1, 0.2µg/L, respectively. The validated method was successfully applied to a toxicokinetics research of SM and its oxidation products after SM dermal exposed rats in a single dose. All three target analytes were found in whole blood samples from poisoned rats, and significant time-dependent responses were also observed. Among them, SMO2 with relatively high toxicity was identified and quantified in vivo for the first time, while SMO was the major product in whole blood and some of them continued to be oxidized to SMO2in vivo. These results give a direct experimental evidence to support that a large amount of SM is converted into the corresponding SMO and SMO2, and these oxidation products might cause potential combined toxic effects.

Conformational Adaption May Explain the Slow Dissociation Kinetics of Roniciclib (BAY 1000394), a Type I CDK Inhibitor with Kinetic Selectivity for CDK2 and CDK9.

Roniciclib (BAY 1000394) is a type I pan-CDK (cyclin-dependent kinase) inhibitor which has revealed potent efficacy in xenograft cancer models. Here, we show that roniciclib displays prolonged residence times on CDK2 and CDK9, whereas residence times on other CDKs are transient, thus giving rise to a kinetic selectivity of roniciclib. Surprisingly, variation of the substituent at the 5-position of the pyrimidine scaffold results in changes of up to 3 orders of magnitude of the drug-target residence time. CDK2 X-ray cocrystal structures have revealed a DFG-loop adaption for the 5-(trifluoromethyl) substituent, while for hydrogen and bromo substituents the DFG loop remains in its characteristic type I inhibitor position. In tumor cells, the prolonged residence times of roniciclib on CDK2 and CDK9 are reflected in a sustained inhibitory effect on retinoblastoma protein (RB) phosphorylation, indicating that the target residence time on CDK2 may contribute to sustained target engagement and antitumor efficacy.

The orally active and bioavailable ATR kinase inhibitor AZD6738 potentiates the anti-tumor effects of cisplatin to resolve ATM-deficient non-small cell lung cancer in vivo.

ATR and ATM are DNA damage signaling kinases that phosphorylate several thousand substrates. ATR kinase activity is increased at damaged replication forks and resected DNA double-strand breaks (DSBs). ATM kinase activity is increased at DSBs. ATM has been widely studied since ataxia telangiectasia individuals who express no ATM protein are the most radiosensitive patients identified. Since ATM is not an essential protein, it is widely believed that ATM kinase inhibitors will be well-tolerated in the clinic. ATR has been widely studied, but advances have been complicated by the finding that ATR is an essential protein and it is widely believed that ATR kinase inhibitors will be toxic in the clinic. We describe AZD6738, an orally active and bioavailable ATR kinase inhibitor. AZD6738 induces cell death and senescence in non-small cell lung cancer (NSCLC) cell lines. AZD6738 potentiates the cytotoxicity of cisplatin and gemcitabine in NSCLC cell lines with intact ATM kinase signaling, and potently synergizes with cisplatin in ATM-deficient NSCLC cells. In contrast to expectations, daily administration of AZD6738 and ATR kinase inhibition for 14 consecutive days is tolerated in mice and enhances the therapeutic efficacy of cisplatin in xenograft models. Remarkably, the combination of cisplatin and AZD6738 resolves ATM-deficient lung cancer xenografts.

Radiolabelling and evaluation of a novel sulfoxide as a PET imaging agent for tumor hypoxia.

[¹8F]FMISO is the most widely validated PET radiotracer for imaging hypoxic tissue. However, as a result of the pharmacokinetics of [¹8F]FMISO a 2h wait between tracer administration and patient scanning is required for optimal image acquisition. In order to develop hypoxia imaging agents with faster kinetics, we have synthesised and evaluated several F-18 labelled anilino sulfoxides. In this manuscript we report on the synthesis, in vitro and in vivo evaluation of a novel fluoroethyltriazolyl propargyl anilino sulfoxide. The radiolabelling of the novel tracer was achieved via 2-[¹8F]fluoroethyl azide click chemistry. Radiochemical yields were 23 ± 4% based on 2-[¹8F]fluoroethyl azide and 7 ± 2% based on K[¹8F]F. The radiotracer did not undergo metabolism or defluorination in an in vitro assay using S9 liver fractions. Imaging studies using SK-RC-52 tumors in BALB/c nude mice have indicated that the tracer may have a higher pO2 threshold than [¹8F]FMISO for uptake in hypoxic tumors. Although clearance from muscle was faster than [¹8F]FMISO, uptake in hypoxic tumors was slower. The average tumor to muscle ratio at 2h post injection in large, hypoxic tumors with a volume greater than 686 mm³ was 1.7, which was similar to the observed ratio of 1.75 for [¹8F]FMISO. Although the new tracer showed improved pharmacokinetics when compared with the previously synthesised sulfoxides, further modifications to the chemical structure need to be made in order to offer significant in vivo imaging advantages over [¹8F]FMISO.

A pharmacokinetic study on a novel anti-HBV agent imidol hydrochloride in rats.

Imidol hydrochloride is a novel agent for the treatment of hepatitis B virus (HBV) infection, which is currently being evaluated in a phase II trial. This study investigated the absorption, excretion and tissue distribution of imidol after an oral dose in rats. The pharmacokinetic parameters were determined for both intravenous and oral dosing. A simple and sensitive UPLC-MS-MS method was employed to determine the imidol levels in rat biological samples. It was applied for the analysis of imidol in plasma, urine, feces, bile and various tissue samples. Imidol was found to have a moderate half-life (∼4 h), a relatively large apparent distribution volume and rapid clearance after an IV dose and oral doses up to 70 mg kg(-1). Dose-dependent linear relationships of AUC0-t and Cmax for imidol was found in the range of 10-70 mg kg(-1) after oral administration to rats. However, the oral bioavailability was low (17.6%). Most of the drug was metabolized and only 20% of the parent drug was excreted. Imidol excreted mainly in feces. The tissue distribution results show that imidol was quickly dispersed to various tissues following an oral dose. Relatively high concentration was found in liver, which is beneficial to the intended indication. Very low levels of imidol were found in brain and testes, indicating that it was difficult for imidol to cross the blood-brain barrier.

Effects of triclabendazole on secretion of danofloxacin and moxidectin into the milk of sheep: role of triclabendazole metabolites as inhibitors of the ruminant ABCG2 transporter.

ATP-binding cassette transporter G2/breast cancer resistance protein (ABCG2/BCRP) mediates drug-drug interactions that affect the secretion of drugs into milk. The aims of this study were: (1) to determine whether the major plasma metabolites of the flukicide triclabendazole (TCBZ), triclabendazole sulfoxide (TCBZSO) and triclabendazole sulfone (TCBZSO2), inhibit ovine and bovine ABCG2 and its Y581S variant in vitro, and (2) to examine whether coadministration of TCBZ with the ABCG2 substrates danofloxacin (a fluoroquinolone) and moxidectin (a milbemycin) affects the secretion of these drugs into the milk of sheep. TCBZSO and TCBZSO2 inhibited ruminant ABCG2 in vitro by reversing the reduced mitoxantrone accumulation and reducing basal to apical transport of nitrofurantoin in cells transduced with bovine variants (S581 and Y581) and the ovine variant of ABCG2. Coadministration of TCBZ with moxidectin or danofloxacin to sheep resulted in significantly reduced levels of moxidectin, but not danofloxacin, in the milk of TCBZ-treated sheep compared to sheep administered moxidectin or danofloxacin alone. The milk area under concentration time curve (AUC 0-48 h) was 2.99±1.41 µg h/mL in the group treated with TCBZ and moxidectin, and 7.75±3.58 µg h/mL in the group treated with moxidectin alone. The AUC (0-48 h) milk/plasma ratio was 37% lower in the group treated with TCBZ and moxidectin (7.34±1.51) than in the group treated with moxidectin alone (11.68±3.61). TCBZ metabolites appear to inhibit ruminant ABCG2 and affect the secretion of ABCG2 substrates into milk of sheep.