Synthesis of Stable Isotope, Tritiated, and Carbon-14 Labeled Balcinrenone.

As part of a medicinal chemistry program aimed at discovering a mineralocorticoid receptor modulator for treatment of kidney and cardiovascular indications, multiple labeled versions of the lead compound, balcinrenone (AZD9977), were prepared. Four stable isotope labeled versions of the compound were prepared for clinical bioanalysis and biological investigations. Three of these stable isotope labeled compounds were tritiated as well as the parent for biology applications and DMPK investigations. They were prepared using a standard iodination-tritiodehalogentation approach. Finally, AZD9977 was prepared in carbon-14 labeled form for preclinical and clinical applications.

Poly(2-Hydroxyethyl Methacrylate) Hydrogel-Based Microneedles for Metformin Release.

The release of metformin, a drug used in the treatment of cancer and diabetes, from poly(2-hydroxyethyl methacrylate), pHEMA, hydrogel-based microneedle patches is demonstrated in vitro. Tuning the composition of the pHEMA hydrogels enables preparation of robust microneedle patches with mechanical properties such that they would penetrate skin (insertion force of a single microneedle to be ≈40 N). Swelling experiments conducted at 20, 35, and 60 °C show temperature-dependent degrees of swelling and diffusion kinetics. Drug release from the pHEMA hydrogel-based microneedles is fitted to various models (e.g., zero order, first order, second order). Such pHEMA microneedles have potential application for transdermal delivery of metformin for the treatment of aging, cancer, diabetes, etc.

Mass Balance and Absorption, Distribution, Metabolism, and Excretion Properties of Balcinrenone following Oral Administration in Combination with Intravenous Microtracer in Healthy Subjects.

An absorption, distribution, metabolism, and excretion study was performed to determine the basic pharmacokinetic parameters, mass balance, and metabolite profiles of balcinrenone, a mineralocorticoid receptor modulator, in humans. This open-label, single-center, nonrandomized study had a two-period design. In period 1, eight healthy male subjects were dosed with a microtracer intravenous infusion of [14C]balcinrenone shortly after receiving an oral dose of unlabeled balcinrenone in a capsule. Following a 7-day washout, the same group of subjects subsequently received an oral dose of [14C]balcinrenone as a suspension in period 2. Clearance and absolute bioavailability of balcinrenone were determined to be 14.2 l/h and 52%, respectively. Renal clearance was determined to be 5.4 l/h (>fu • glomerular filtration rate), indicating elimination via active tubular secretion, which was potentially mediated by P-glycoprotein 1 and/or organic anion transporter 3, according to in vitro transporter data. In total, 94.1% of the oral dose was recovered: 45.2% in the urine and 48.9% in the feces. Balcinrenone was primarily metabolized via oxidation, and in vitro data suggest that cytochrome P450 3A4 was the main enzyme responsible. Intact [14C]balcinrenone accounted for 55% of drug-related material in the plasma; four metabolites were identified, each representing <6% of the total plasma radioactivity. In conclusion, this two-period study has determined the basic pharmacokinetic parameters of balcinrenone in humans, including absolute bioavailability and disposition. No metabolites warranted further evaluation on account of their low representation, and any contribution to the pharmacodynamic response or potential drug-drug interactions was deemed negligible. SIGNIFICANCE STATEMENT: This study provides a detailed understanding of the pharmacokinetics, disposition, and metabolism of balcinrenone following oral and microtracer intravenous administration in humans. In vitro phenotyping and transporter data granted mechanistic insights into the absorption, distribution, metabolism, and excretion properties of balcinrenone. This knowledge will guide future nonclinical and clinical studies evaluating drug-drug interactions, organ dysfunction, and safety of metabolites.

Application of Accelerator Mass Spectrometry to Characterize the Mass Balance Recovery and Disposition of AZD4831, a Novel Myeloperoxidase Inhibitor, following Administration of an Oral Radiolabeled Microtracer Dose in Humans.

This study evaluated the mass balance and disposition of AZD4831, a novel myeloperoxidase inhibitor, in six healthy participants using a 14C-labeled microtracer coupled with analysis by accelerator mass spectrometry (AMS). A single oral dose of 10 mg 14C-AZD4831 (14.8 kBq) was administered as a solution, and 14C levels were quantified by AMS in blood, urine, and feces over 336 hours postdose. AZD4831 was rapidly absorbed, and AZD4831 plasma concentrations declined in a biphasic manner, with a long half-life of 52 hours. AZD4831 was eliminated via metabolism and renal excretion. An N-carbamoyl glucuronide metabolite of AZD4831 (M7), formed primarily via UGT1A1, was the predominant circulating metabolite. Presumably, M7 contributed to the long half-life of AZD4831 via biliary elimination and hydrolysis/enterohepatic recirculation of AZD4831. On average, ∼84% of administered 14C-AZD4831 was recovered by 336 hours postdose (urine, 51.2%; feces, 32.4%). Between 32%-44% of the dose was excreted as unchanged AZD4831 in urine, indicating renal elimination as the major excretory route. Only 9.7% of overall fecal recovery was recorded in the first 48 hours, with the remainder excreted over 48%-336 hours, suggesting that most fecal recovery was due to biliary elimination. Furthermore, only 6% of unchanged AZD4831 was recovered in feces. Overall, the fraction of the administered AZD4831 dose absorbed was high. 14C-AZD4831 was well tolerated. These findings contribute to increasing evidence that human absorption, distribution, metabolism, and excretion studies can be performed with acceptable mass balance recovery at therapeutically relevant doses and low radiolabel-specific activity using an AMS-14C microtracer approach. SIGNIFICANCE STATEMENT: In this study, the human absorption, distribution, metabolism, and excretion (hADME) of the novel myeloperoxidase inhibitor AZD4831 was assessed following oral administration. This included investigation of the disposition of M7, the N-carbamoyl glucuronide metabolite. Resolution of challenges highlighted in this study contributes to increasing evidence that hADME objectives can be achieved in a single study for compounds with therapeutically relevant doses and low radiolabel-specific activity by using an AMS-14C microtracer approach, thus reducing the need for preclinical radiolabeled studies.

Apolipoprotein E Binding Drives Structural and Compositional Rearrangement of mRNA-Containing Lipid Nanoparticles.

Emerging therapeutic treatments based on the production of proteins by delivering mRNA have become increasingly important in recent times. While lipid nanoparticles (LNPs) are approved vehicles for small interfering RNA delivery, there are still challenges to use this formulation for mRNA delivery. LNPs are typically a mixture of a cationic lipid, distearoylphosphatidylcholine (DSPC), cholesterol, and a PEG-lipid. The structural characterization of mRNA-containing LNPs (mRNA-LNPs) is crucial for a full understanding of the way in which they function, but this information alone is not enough to predict their fate upon entering the bloodstream. The biodistribution and cellular uptake of LNPs are affected by their surface composition as well as by the extracellular proteins present at the site of LNP administration, e.g., apolipoproteinE (ApoE). ApoE, being responsible for fat transport in the body, plays a key role in the LNP's plasma circulation time. In this work, we use small-angle neutron scattering, together with selective lipid, cholesterol, and solvent deuteration, to elucidate the structure of the LNP and the distribution of the lipid components in the absence and the presence of ApoE. While DSPC and cholesterol are found to be enriched at the surface of the LNPs in buffer, binding of ApoE induces a redistribution of the lipids at the shell and the core, which also impacts the LNP internal structure, causing release of mRNA. The rearrangement of LNP components upon ApoE incubation is discussed in terms of potential relevance to LNP endosomal escape.

Computationally-Guided Development of a Chelated NHC-P Iridium(I) Complex for the Directed Hydrogen Isotope Exchange of Aryl Sulfones.

Herein, we report the rational, computationally-guided design of an iridium(I) catalyst system capable of enabling directed hydrogen isotope exchange (HIE) with the challenging sulfone directing group. Substrate binding energy was used as a parameter to guide rational ligand design via an in silico catalyst screen, resulting in a lead series of chelated iridium(I) NHC-phosphine complexes. Subsequent preparative studies show that the optimal catalyst system displays high levels of activity in HIE, and we demonstrate the labeling of a broad scope of substituted aryl sulfones. We also show that the activity of the catalyst is maintained at low pressures of deuterium gas and apply these conditions to tritium radiolabeling, including the expedient synthesis of a tritium-labeled drug molecule.

Microbiome-derived carnitine mimics as previously unknown mediators of gut-brain axis communication.

Alterations to the gut microbiome are associated with various neurological diseases, yet evidence of causality and identity of microbiome-derived compounds that mediate gut-brain axis interaction remain elusive. Here, we identify two previously unknown bacterial metabolites 3-methyl-4-(trimethylammonio)butanoate and 4-(trimethylammonio)pentanoate, structural analogs of carnitine that are present in both gut and brain of specific pathogen-free mice but absent in germ-free mice. We demonstrate that these compounds are produced by anaerobic commensal bacteria from the family Lachnospiraceae (Clostridiales) family, colocalize with carnitine in brain white matter, and inhibit carnitine-mediated fatty acid oxidation in a murine cell culture model of central nervous system white matter. This is the first description of direct molecular inter-kingdom exchange between gut prokaryotes and mammalian brain cells, leading to inhibition of brain cell function.

New trends and applications in carboxylation for isotope chemistry.

Carboxylations are an important method for the incorporation of isotopically labeled 14 CO2 into molecules. This manuscript will review labeled carboxylations since 2010 and will present a perspective on the potential of recent unlabeled methodology for labeled carboxylations. The perspective portion of the manuscript is broken into 3 major sections based on product type, arylcarboxylic acids, benzylcarboxylic acids, and alkyl carboxylic acids, and each of those sections is further subdivided by substrate.

Isotope labelling by reduction of nitriles: Application to the synthesis of isotopologues of tolmetin and celecoxib.

The aryl methyl group is found in many drug-like compounds, but there are limited ways of preparing compounds with an isotope label in this methyl position. The process of cyanation of an aryl halide followed by complete reduction of the nitrile to a methyl group was investigated as a route for preparing stable and radiolabelled isotopologues of drug-like compounds. Using this methodology, carbon-13, deuterium, carbon-14, and tritium labelled isotopologues of the nonsteroidal anti-inflammatory drug tolmetin were produced, as well as carbon-13, deuterium, and carbon-14 labelled isotopologues of another nonsteroidal anti-inflammatory drug, celecoxib. The radiolabelled compounds were produced at high specific activity and the stable isotope labelled compounds with high incorporation making them suitable for use as internal standards in mass spectrometry assays. This approach provides a common synthetic route to multiple isotopologues of compounds using inexpensive and readily available labelled starting materials.

The synthesis of a tritium, carbon-14, and stable isotope-labeled cathepsin C inhibitors.

As part of a medicinal chemistry program aimed at developing a highly potent and selective cathepsin C inhibitor, tritium, carbon-14, and stable isotope-labeled materials were required. The synthesis of tritium-labeled methanesulfonate 5 was achieved via catalytic tritiolysis of a chloro precursor, albeit at a low radiochemical purity of 67%. Tritium-labeled AZD5248 was prepared via a 3-stage synthesis, utilizing amide-directed hydrogen isotope exchange. Carbon-14 and stable isotope-labeled AZD5248 were successfully prepared through modifications of the medicinal chemistry synthetic route, enabling the use of available labeled intermediates.

Comparison of cytokine responses between dogs with sepsis and dogs with immune-mediated hemolytic anemia.

Cytokine abnormalities have been described previously in dogs with varied immune mediated and inflammatory conditions such as IMHA and sepsis. The purpose of this study was to establish references ranges for cytokine levels in dogs and to compare cytokine levels in normal dogs and dogs with two common inflammatory diseases (sepsis and IMHA). We hypothesized that cytokine response profiles in dogs with sepsis would be significantly different from those in dogs with IMHA due to the very different etiologies of the two diseases. Concentrations of 14 different cytokines in serum were measured and values grouped according to cytokine function. Serum from clinically normal dogs was used to establish cytokine concentration reference ranges. Rank values for each of the 4 cytokine groups were then compared statistically between healthy control, septic and IMHA dogs. This analysis revealed differences in cytokine groups between dogs with sepsis and IMHA when compared to healthy control dogs but no difference between dogs with either of these conditions. In conclustion, dogs in the early stage of sepsis and IMHA have similar circulating cytokines despite different etiologies suggesting activation of common immunologic pathways. This may have implications for immunotherapy of immune mediated diseases in dogs of varying etiology.

The synthesis of tritium, carbon-14 and stable isotope labelled selective estrogen receptor degraders.

As part of a Medicinal Chemistry program aimed at developing an orally bioavailable selective estrogen receptor degrader, a number of tritium, carbon-14, and stable isotope labelled (E)-3-[4-(2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indol-1-yl)phenyl]prop-2-enoic acids were required. This paper discusses 5 synthetic approaches to this compound class.

Evaluation of PaO2 /FiO2 and SaO2 /FiO2 ratios in postoperative dogs recovering on room air or nasal oxygen insufflation.

OBJECTIVE: To evaluate partial pressure of oxygen in arterial blood/fractional percentage of inspired oxygen (PaO2 /FiO2 ) and SaO2 /FiO2 ratios (where SaO2 is percentage of oxyhemoglobin saturation in arterial blood), and the correlation between PaO2 /FiO2 and SaO2 /FiO2 , in healthy dogs recovering postoperatively on room air versus nasal oxygen insufflation. DESIGN: Retrospective study. SETTING: University veterinary teaching hospital. ANIMALS: Nineteen dogs. MEASUREMENTS AND MAIN RESULTS: Medical records were retrospectively evaluated for data from a previous prospective study of dogs undergoing ovariohysterectomy, subsequently randomized to receive 100 mL/kg/min of nasal oxygen insufflation (estimated 37% FiO2 , n = 9) or room air (estimated 21% FiO2 , n = 10) for 2 hours postoperatively. Baseline information was obtained 1 hour intraoperatively, followed by three postoperative time points (10, 60, and 120 min). Data recorded for each time point included FiO2 , PaO2 , SaO2 , PaO2 /FiO2 , SaO2 /FiO2 , partial pressure of carbon dioxide in arterial blood (PaCO2 ), rectal temperature, and arterial blood pH. The PaO2 /FiO2 in dogs recovering on supplemental oxygen was significantly higher compared to dogs recovering on room air (516 ± 28 vs. 359 ± 10, P < 0.0001), whereas the SaO2 /FiO2 ratio in dogs recovering on supplemental oxygen was significantly lower compared to dogs recovering on room air (268 ± 0.5 versus 448 ± 1.4, P < 0.0001). The PaO2 /FiO2 and SaO2 /FiO2 ratios demonstrated excellent correlation for both groups at each postoperative time point. In dogs breathing room air, PaO2 /FiO2 and SaO2 /FiO2 correlation coefficients were 0.90, 0.95, and 0.93 (P < 0.001). In dogs receiving supplemental oxygen, PaO2 /FiO2 and SaO2 /FiO2 correlation coefficients were 0.94, 0.93, and 0.90 (P < 0.001). CONCLUSIONS: In this population of postoperative dogs breathing either room air or with nasal oxygen insufflation, PaO2 /FiO2 and SaO2 /FiO2 had excellent correlation. Further evaluation into the correlation between SaO2 /FiO2 or pulse oximeter oxygen saturation (SpO2 )/FiO2 with PaO2 /FiO2 in both healthy dogs, and dogs with pulmonary dysfunction is warranted.

Aortic Binding of AZD5248: Mechanistic Insight and Reactivity Assays To Support Lead Optimzation.

The oral dipeptidyl peptidase 1 (DPP1) inhibitor AZD5248 showed aortic binding in a rat quantitative whole-body autoradiography (QWBA) study, and its development was terminated prior to human dosing. A mechanistic hypothesis for this finding was established invoking reactivity with aldehydes involved in the cross-linking of elastin, a major component of aortic tissue. This was tested by developing a simple aldehyde chemical reactivity assay and a novel in vitro competitive covalent binding assay. Results obtained with AZD5248, literature compounds, and close analogues of AZD5248 support the mechanistic hypothesis and provide validation for the use of these assays in a two tier screening approach to support lead optimization. The strengths and limitations of these assays are discussed.

Evaluation of the effects of hospital visit stress on physiologic variables in dogs.

OBJECTIVE: To evaluate differences in pulse rate, rectal temperature, respiratory rate, and systolic arterial blood pressure in dogs between the home and veterinary hospital environments. DESIGN: Prospective observational study. ANIMALS: 30 client-owned healthy dogs. PROCEDURES: Study dogs had respiratory rate, pulse rate, rectal temperature, and systolic arterial blood pressure measured in their home environment. Dogs were then transported to the veterinary hospital, and measurements were repeated. RESULTS: Significant differences in blood pressure, rectal temperature, and pulse rate were observed between measurements obtained in the home and hospital environments. Mean blood pressure increased by 16% (95% confidence interval [CI], 8.8% to 24%), rectal temperature increased by < 1% (95% CI, 0.1% to 0.6%), and pulse rate increased by 11% (95% CI, 5.3% to 17.6%). The number of dogs panting in the hospital environment (19/30 [63%]) was significantly higher than the number of dogs panting in the home environment (5/30 [17%]) CONCLUSIONS AND CLINICAL RELEVANCE: Results of the present study suggested that practitioners should consider stress from transportation and environmental change when canine patients have abnormalities of vital signs on initial examination, and the variables in question should be rechecked before a definitive diagnosis of medical illness is reached or extensive further workup is pursued.

Isotope chemistry; a useful tool in the drug discovery arsenal.

As Medicinal Chemists are responsible for the synthesis and optimization of compounds, they often provide intermediates for use by isotope chemistry. Nevertheless, there is generally an incomplete understanding of the critical factors involved in the labeling of compounds. The remit of an Isotope Chemistry group varies from company to company, but often includes the synthesis of compounds labeled with radioisotopes, especially H-3 and C-14 and occasionally I-125, and stable isotopes, especially H-2, C-13, and N-15. Often the remit will also include the synthesis of drug metabolites. The methods used to prepare radiolabeled compounds by Isotope Chemists have been reviewed relatively recently. However, the organization and utilization of Isotope Chemistry has not been discussed recently and will be reviewed herein.

Clinical evaluation of a single dose of immune plasma for treatment of canine parvovirus infection.

OBJECTIVE: To evaluate the efficacy of administration of a single 12-mL dose of canine parvovirus (CPV)-immune plasma for treatment of CPV enteritis. DESIGN: Prospective, randomized, double-blinded, placebo-controlled clinical trial. ANIMALS: 14 dogs with naturally occurring CPV enteritis. PROCEDURES: Dogs were assigned to treatment groups on the basis of randomization tables and were administered a single i.v. dose of CPV-immune plasma (treatment group) or an equivalent volume of saline (0.9% NaCl) solution (placebo group) within 18 hours after admission to the hospital. Treatment and outcome variables evaluated included neutrophil, monocyte, and CPV counts; number of days of hospitalization; changes in body weight; and cost of treatment. RESULTS: When dogs treated with CPV-immune plasma were compared with dogs treated with saline solution, there were no significant differences detected among neutrophil or monocyte counts, magnitude of viremia, weight change, number of days of hospitalization, or cost of treatment. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of a single 12-mL dose of immune plasma soon after the onset of CPV enteritis in dogs was not effective in ameliorating clinical signs, reducing viremia, or hastening hematologic recovery.

Isothiourea-mediated asymmetric O- to C-carboxyl transfer of oxazolyl carbonates: structure-selectivity profiles and mechanistic studies.

The structural motif within a series of tetrahydropyrimidine-based isothioureas necessary for generating high asymmetric induction in the asymmetric Steglich rearrangement of oxazolyl carbonates is fully explored, with crossover and dynamic (19)F NMR experiments used to develop a mechanistic understanding of this transformation.

Isothiourea-catalysed asymmetric C-acylation of silyl ketene acetals.

Screening of a range of chiral isothioureas and acyl donors to promote the asymmetric C-acylation of silyl ketene acetals indicates that C(2)-aryl-dihydropyrimidobenzothiazole-derived isothioureas and propionic anhydride give optimal reactivity and enantioselectivity in this process. Under optimised conditions 3-acyl-3-aryl or 3-acyl-3-alkylfuranones are prepared in good yields and moderate to excellent enantioselectivities (up to 98% ee; ee=enantiomeric excess).

Structure-enantioselectivity effects in 3,4-dihydropyrimido[2,1-b]benzothiazole-based isothioureas as enantioselective acylation catalysts.

The catalytic activity and enantioselectivity in the kinetic resolution of (±)-1-naphthylethanol with a range of structurally related 3,4-dihydropyrimido[2,1-b]benzothiazole-based catalysts is examined. Of the isothiourea catalysts screened, (2S,3R)-2-phenyl-3-isopropyl substitution proved optimal, giving good levels of selectivity in the kinetic resolution of a number of secondary alcohols (S values up to >100 at ~50% conversion). Low catalyst loadings (0.10-0.25 mol%) of the optimal isothiourea can be used to generate enantiopure alcohols (>99% ee) in good yields.