Prediction of Kidney Drug Clearance: A Comparison of Tubular Secretory Clearance and Glomerular Filtration Rate.

BACKGROUND: Although proximal tubular secretion is the primary mechanism of kidney drug elimination, current kidney drug dosing strategies are on the basis of eGFR. METHODS: In a dedicated pharmacokinetic study to compare GFR with tubular secretory clearance for predicting kidney drug elimination, we evaluated stable outpatients with eGFRs ranging from 21 to 140 ml/min per 1.73 m2. After administering single doses of furosemide and famciclovir (metabolized to penciclovir), we calculated their kidney clearances on the basis of sequential plasma and timed urine measurements. Concomitantly, we quantified eight endogenous secretory solutes in plasma and urine using liquid chromatography-tandem mass spectrometry and measured GFR by iohexol clearance (iGFR). We computed a summary secretion score as the scaled average of the secretory solute clearances. RESULTS: Median iGFR of the 54 participants was 73 ml/min per 1.73 m2. The kidney furosemide clearance correlated with iGFR (r=0.84) and the summary secretion score (r=0.86). The mean proportionate error (MPE) between iGFR-predicted and measured furosemide clearance was 30.0%. The lowest MPE was observed for the summary secretion score (24.1%); MPEs for individual secretory solutes ranged from 27.3% to 48.0%. These predictive errors were statistically indistinguishable. Penciclovir kidney clearance was correlated with iGFR (r=0.83) and with the summary secretion score (r=0.91), with similar predictive accuracy of iGFR and secretory clearances. Combining iGFR with the summary secretion score yielded only modest improvements in the prediction of the kidney clearance of furosemide and penciclovir. CONCLUSIONS: Secretory solute clearance measurements can predict kidney drug clearances. However, tight linkage between GFR and proximal tubular secretory clearance in stable outpatients provides some reassurance that GFR, even when estimated, is a useful surrogate for predicting secretory drug clearances in such patients.

Relationship of Phosphatidylethanol Biomarker to Self-Reported Alcohol Drinking Patterns in Older and Middle-Age Adults.

BACKGROUND: Risky alcohol consumption is on the rise among older adults. Biomarkers such as phosphatidylethanol (PEth) have been used to evaluate the correspondence between an objective, laboratory-based biomarker and self-report of alcohol consumption. This study examined the relationship between PEth, self-report of alcohol consumption, and health indices in a sample of community-dwelling older to middle-age adults (aged 35 to 89) with healthy and risky levels of alcohol consumption. METHODS: Self-reports of alcohol consumption were collected using the Alcohol Use Disorders Identification Test (AUDIT) and Form 30. In addition, indices of health along with a blood sample to determine PEth values were collected (N = 183). RESULTS: PEth was correlated with age, AUDIT-C, AUDIT total, alcohol consumption, mood, and liver function measures but not with medical comorbidity or body mass index (J Gerontol B Psychol Sci Soc Sci 73, 2018, 633). Alcohol consumption over the past 30 days measured with Form 30 was the strongest predictor of PEth levels for both middle-age and older adults, with age a small contributing predictor. General alcohol consumption patterns for amount of alcohol consumed over a 30-day period revealed middle-age adults consumed larger amounts of alcohol compared with older adults, but older adults consumed alcohol on more days than middle-age adults. Middle-age participants evidenced higher PEth levels than older adults at comparable drinking rates. CONCLUSIONS: Overall, findings suggest a strong relationship between alcohol consumption and PEth levels with age a small but contributing factor to predicting PEth levels.

Disposition of Methamphetamine and Major Metabolites in Mice: Role of Organic Cation Transporter 3 in Tissue-Selective Accumulation of Para-Hydroxymethamphetamine.

Methamphetamine is one of the most widely abused illicit drugs. Although human intoxication and multiple tissue toxicities frequently occur in abusers, little is known about the distribution of methamphetamine or its primary metabolites, amphetamine and para-hydroxymethamphetamine (p-OHMA), to their sites of toxicity. This study determined the pharmacokinetics, tissue exposure, and partition ratios of methamphetamine and major metabolites in various mouse tissues and investigated the impact of organic cation transporter 3 (Oct3) following i.v. injection of methamphetamine to male Oct3+/+ and Oct3-/- mice. Methamphetamine, amphetamine, and p-OHMA were readily detectable in plasma with Oct3+/+ and Oct3-/- mice displaying similar plasma pharmacokinetic profiles for all three analytes. In addition to kidney and liver, salivary glands highly accumulated methamphetamine, amphetamine, and p-OHMA with total exposure 3.3- to 9.4-fold higher than plasma area under the concentration-time curve (AUC). Consistent with being an Oct3 substrate, p-OHMA AUC in salivary glands is reduced by 50% in Oct3-/- mice. p-OHMA AUC in skeletal muscle is also significantly reduced in Oct3-/- mice. Our data identified salivary glands as a novel site of high accumulation of methamphetamine and metabolites, which may underlie methamphetamine toxicity in this tissue. Furthermore, our study identified Oct3 as an important determinant of tissue uptake and exposure to p-OHMA in salivary glands and skeletal muscle. Our findings suggest that local tissue accumulation of methamphetamine and/or its metabolites may play a role in several of the reported peripheral toxicities of methamphetamine, and Oct3 can significantly impact tissue exposure to its substrates without affecting systemic elimination.

Pharmacodynamics of Ceftaroline plus Ampicillin against Enterococcus faecalis in an In Vitro Pharmacokinetic/Pharmacodynamic Model of Simulated Endocardial Vegetations.

The combination of ampicillin plus ceftaroline has been suggested to be more reliably synergistic against Enterococcus faecalis than ampicillin plus ceftriaxone using time-kill methods. The purpose of this study was to determine if this trend persists in a two-compartment model of simulated endocardial vegetations (SEV) using clinically relevant pharmacokinetic exposures of these antimicrobials. Three clinically derived E. faecalis strains were included in the study. The MICs of study antimicrobials were determined by broth microdilution. Simulations of ampicillin (2 g every 4 h [q4h]; maximum concentration of drug in serum [Cmax], 72.4 mg/liter; half-life [t1/2], 1.9 h), ceftaroline-fosamil (600 mg q8h; Cmax, 21.3 mg/liter; t1/2, 2.66 h), ceftriaxone (Cmax, 257 mg/liter; t1/2, 8 h), and ampicillin plus ceftaroline and ampicillin plus ceftriaxone were evaluated against 3 strains of E. faecalis isolated from patients with endocarditis in an in vitro PK/PD SEV model over 72 h, with a starting inoculum of ∼9 log10 CFU/g. All strains were susceptible to ampicillin (MIC, ≤2 mg/liter). Ceftaroline MICs varied from 2 to 16 mg/liter. All strains had ceftriaxone MICs of 256 mg/liter. W04 and W151 exhibited high-level aminoglycoside resistance but W07 did not. Ampicillin plus ceftaroline resulted in significantly greater reductions in CFU per gram by 72 h than ampicillin for all strains (P ≤ 0.025) than ampicillin plus ceftriaxone for W04 (P = 0.019) but not W07 or W151 (P ≥ 0.15). A 4-fold increase in ampicillin MIC was observed for W07 at 72 h, but this was prevented by the addition of ceftaroline or ceftriaxone. The combination of ampicillin plus ceftaroline appears to be at least as efficacious as ampicillin plus ceftriaxone and may lead to improved activity against some strains of E. faecalis, but these differences may be small and the clinical significance should not be overestimated.

P-gp/ABCB1 exerts differential impacts on brain and fetal exposure to norbuprenorphine.

Norbuprenorphine is the major active metabolite of buprenorphine which is commonly used to treat opiate addiction during pregnancy. Norbuprenorphine produces marked respiratory depression and was 10 times more potent than buprenorphine. Therefore, it is important to understand the mechanism that controls fetal exposure to norbuprenorphine, as exposure to this compound may pose a significant risk to the developing fetus. P-gp/ABCB1 and BCRP/ABCG2 are two major efflux transporters regulating tissue distribution of drugs. Previous studies have shown that norbuprenorphine, but not buprenorphine, is a P-gp substrate. In this study, we systematically examined and compared the roles of P-gp and BCRP in determining maternal brain and fetal distribution of norbuprenorphine using transporter knockout mouse models. We administered 1mg/kg norbuprenorphine by retro-orbital injection to pregnant FVB wild-type, Abcb1a-/-/1b-/-, and Abcb1a-/-/1b-/-/Abcg2-/- mice on gestation day 15. The fetal AUC of norbuprenorphine was ∼64% of the maternal plasma AUC in wild-type mice, suggesting substantial fetal exposure to norbuprenorphine. The maternal plasma AUCs of norbuprenorphine in Abcb1a-/-/1b-/- and Abcb1a-/-/1b-/-/Abcg2-/- mice were ∼2 times greater than that in wild-type mice. Fetal AUCs in Abcb1a-/-/1b-/- and Abcb1a-/-/1b-/-/Abcg2-/- mice were also increased compared to wild-type mice; however, the fetal-to-maternal plasma AUC ratio remained relatively unchanged by the knockout of Abcb1a/1b or Abcb1a/1b/Abcg2. In contrast, the maternal brain-to-maternal plasma AUC ratio in Abcb1a-/-/1b-/- or Abcb1a-/-/1b-/-/Abcg2-/- mice was increased ∼30-fold compared to wild-type mice. Protein quantification by LC-MS/MS proteomics revealed significantly higher amounts of P-gp protein in the wild-type mice brain than that in the placenta. These results indicate that fetal exposure to norbuprenorphine is substantial and that P-gp has a minor impact on fetal exposure to norbuprenorphine, but plays a significant role in restricting its brain distribution. The differential impacts of P-gp on norbuprenorphine distribution into the brain and fetus are likely, at least in part, due to the differences in amounts of P-gp protein expressed in the blood-brain and blood-placental barriers. BCRP is not as important as P-gp in determining both the systemic and tissue exposure to norbuprenorphine. Finally, fetal AUCs of the metabolite norbuprenorphine-ß-d-glucuronide were 3-7 times greater than maternal plasma AUCs, while the maternal brain AUCs were <50% of maternal plasma AUCs, suggesting that a reversible pool of conjugated metabolite in the fetus may contribute to the high fetal exposure to norbuprenorphine.

Pharmacometabonomic Prediction of Busulfan Clearance in Hematopoetic Cell Transplant Recipients.

Intravenous (IV) busulfan doses are often personalized to a concentration at steady state (Css) using the patient's clearance, which is estimated with therapeutic drug monitoring. We sought to identify biomarkers of IV busulfan clearance using a targeted pharmacometabonomics approach. A total of 200 metabolites were quantitated in 106 plasma samples, each obtained before IV busulfan administration in hematopoietic cell transplant (HCT) recipients. Both univariate linear regression with false discovery rate (FDR) and pathway enrichment analyses using the Global test were performed. In the univariate analysis, glycine, N-acetylglycine, 2-hydroxyisovaleric acid, creatine, serine, and tyrosine were statistically significantly associated with IV busulfan clearance at P < 0.05, with the first three satisfying the FDR of q < 0.1. Using pathway enrichment analysis, the glycine, serine, and threonine metabolism pathway was statistically significantly associated with IV busulfan clearance at P < 0.05 and q < 0.1, and a pathway impact >0.1. Glycine is a component of glutathione, which is conjugated with busulfan via glutathione transferase enzymes. These results demonstrate the potential utility of pharmacometabonomics to inform IV busulfan dosing. Future studies are required to validate these findings.

Interindividual Variability in Cytochrome P450-Mediated Drug Metabolism.

The cytochrome P450 (P450) enzymes are the predominant enzyme system involved in human drug metabolism. Alterations in the expression and/or activity of these enzymes result in changes in pharmacokinetics (and consequently the pharmacodynamics) of drugs that are metabolized by this set of enzymes. Apart from changes in activity as a result of drug-drug interactions (by P450 induction or inhibition), the P450 enzymes can exhibit substantial interindividual variation in basal expression and/or activity, leading to differences in the rates of drug elimination and response. This interindividual variation can result from a myriad of factors, including genetic variation in the promoter or coding regions, variation in transcriptional regulators, alterations in microRNA that affect P450 expression, and ontogenic changes due to exposure to xenobiotics during the developmental and early postnatal periods. Other than administering a probe drug or cocktail of drugs to obtain the phenotype or conducting a genetic analysis to determine genotype, methods to determine interindividual variation are limited. Phenotyping via a probe drug requires exposure to a xenobiotic, and genotyping is not always well correlated with phenotype, making both methodologies less than ideal. This article describes recent work evaluating the effect of some of these factors on interindividual variation in human P450-mediated metabolism and the potential utility of endogenous probe compounds to assess rates of drug metabolism among individuals.

Reversibility and Low Commitment to Forward Catalysis in the Conjugation of Lipid Alkenals by Glutathione Transferase A4-4.

High concentrations of electrophilic lipid alkenals formed during oxidative stress are implicated in cytotoxicity and disease. However, low concentrations of alkenals are required to induce antioxidative stress responses. An established clearance pathway for lipid alkenals includes conjugation to glutathione (GSH) via Michael addition, which is catalyzed mainly by glutathione transferase isoform A4 (GSTA4-4). Based on the ability of GSTs to catalyze hydrolysis or retro-Michael addition of GSH conjugates, and the antioxidant function of low concentrations of lipid alkenals, we hypothesize that GSTA4-4 contributes a homeostatic role in lipid metabolism. Enzymatic kinetic parameters for retro-Michael addition with trans-2-Nonenal (NE) reveal the chemical competence of GSTA4-4 in this putative role. The forward GSTA4-4-catalyzed Michael addition occurs with the rapid exchange of the C2 proton of NE in D2O as observed by NMR. The isotope exchange was completely dependent on the presence of GSH. The overall commitment to catalysis, or the ratio of first order kcat,f for 'forward' Michael addition to the first order kcat,ex for H/D exchange is remarkably low, approximately 3:1. This behavior is consistent with the possibility that GSTA4-4 is a regulatory enzyme that contributes to steady-state levels of lipid alkenals, rather than a strict 'one way' detoxication enzyme.

Physiologically Based Pharmacokinetic Modeling of 3 HIV Drugs in Combination and the Role of Lymphatic System after Subcutaneous Dosing. Part 1: Model for the Free-Drug Mixture.

Drug-combination nanoparticles (DcNP) allow the formulation of multiple HIV drugs in one injectable. In nonhuman primates (NHP), all drugs in DcNP have demonstrated long-acting pharmacokinetics (PK) in the blood and lymph nodes, rendering it suitable for a Targeted Long-acting Antiretroviral Therapy (TLC-ART). To support the translation of TLC-ART into the clinic, the objective is to present a physiologically based PK (PBPK) model tool to control mechanisms affecting the rather complex DcNP-drug PK. Two species contribute simultaneously to the drug PK: drugs that dissociate from DcNP (Part 1) and drugs retained in DcNP (Part 2, presented separately). Here, we describe the PBPK modeling of the nanoparticle-free drugs. The free-drug model was built on subcutaneous injections of suspended lopinavir, ritonavir, and tenofovir in NHP, and validated by external experiments. A novelty was the design of a lymphatic network as part of a whole-body PBPK system which included major lymphatic regions: the cervical, axillary, hilar, mesenteric, and inguinal nodes. This detailed/regionalized description of the lymphatic system and mononuclear cells represents an unprecedented level of prediction that renders the free-drug model extendible to other small-drug molecules targeting the lymphatic system at both the regional and cellular levels.

Safety and Tolerability of Nicotinamide Riboside in Heart Failure With Reduced Ejection Fraction.

The mitochondrial dysfunction characteristic of heart failure (HF) is associated with changes in intracellular nicotinamide adenine dinucleotide (NAD+) and NADH levels. Raising NAD+ levels with the NAD+ precursor, nicotinamide riboside (NR), may represent a novel HF treatment. In this 30-participant trial of patients with clinically stable HF with reduced ejection fraction, NR, at a dose of 1,000 mg twice daily, appeared to be safe and well tolerated, and approximately doubled whole blood NAD+ levels. Intraindividual NAD+ increases in response to NR correlated with increases in peripheral blood mononuclear cell basal (R 2 = 0.413, P = 0.003) and maximal (R 2 = 0.434, P = 0.002) respiration, and with decreased NLRP3 expression (R 2 = 0.330, P = 0.020). (Nicotinamide Riboside in Systolic Heart Failure; NCT03423342).

Development and validation of a LC-MS/MS method for in vivo quantification of meta-iodobenzylguanidine (mIBG).

meta-iodobenzylguanidine (mIBG) is a radiopharmaceutical used for the diagnosis and treatment of neuroendocrine cancers. Previous quantification of mIBG in biodistribution and pharmacokinetic studies mainly relied on the use of radiolabeled mIBG, which involves the handling of highly radioactive materials. The goal of this study was to develop a nonradioactive analytical method for quantifying mIBG in mouse plasma and tissue homogenates using high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). Samples were prepared for analysis using a protein precipitation method. Mass spectrometry analysis was performed using 4-hydroxyphenformin as the internal standard, and the mass-to-charge transitions were 276.1 → 217.0 for mIBG and 222.1 → 121.0 for 4-hydroxyphenformin. The quantification limit of mIBG was 0.98 ng/mL, and the method was linear up to 500 ng/mL. The accuracy, inter-day and intra-day precision were 96-112%, 5.5-14.4%, and 3.7-14.1%, respectively, suggesting that the method was accurate and precise in quantifying mIBG at multiple concentrations in mouse plasma and liver homogenates. The extraction recovery was 96-106% and the matrix effect was 95-110%, indicating that the method was reproducible in quantifying mIBG with minimal impact from the biological matrices. In summary, we have developed and validated a fast, high-throughput quantification method of non-radiolabeled mIBG using LC-MS/MS. This method is reproducible, accurate, and precise, and can be used to quantify mIBG in plasma and tissue matrices to determine the pharmacokinetics and biodistribution of mIBG in preclinical animal models.

Nicotine metabolism and its association with CYP2A6 genotype among Indigenous people in Alaska who smoke.

Prevalence of smoking is higher in Alaska Native and American Indian (ANAI) populations living in Alaska than the general US population. Genetic factors contribute to smoking and cessation rates. The objective of this study was to compare CYP2A6 genetic variation and CYP2A6 enzyme activity toward nicotine in an ANAI population. ANAI (N = 151) people trying to quit smoking were recruited. DNA samples were genotyped for CYP2A6 variants *1X2A, *1B, *2, *4, *9, *10, *12, and *35. Multiple nicotine metabolites were measured in plasma and urine samples, including cotinine and 3'-hydroxycotinine used to determine CYP2A6 activity (e.g., nicotine metabolite ratio [NMR]). We calculated summary statistics for all of the genotypes and metabolites and assigned CYP2A6 activity scores based on known information. We studied the association of CYP2A6 variants with the NMR and smoking histories. The overall frequency of the CYP2A6*1B gain of function allele was high in the ANAI versus non-ANAI populations in other studies. Both *4 null and *9 decrease of function alleles had frequencies similar to previous studies of ANAI populations. In a multivariate analysis, the genotype-inferred CYP2A6 activity score was associated with both plasma and urine NMR (p value = 8.56E-08 and 4.08E-13, respectively). Plasma NMR was also associated with duration of smoking (p value < 0.01) but not urinary total nicotine equivalents uncorrected for creatinine (TNE9uc ) or biological sex. Urine NMR was significantly associated (p value < 0.01) with TNE9uc . Variation in NMR in this ANAI population is explained in part by CYP2A6 genetic variation.

Assessing Transporter-Mediated Natural Product-Drug Interactions Via In vitro-In Vivo Extrapolation: Clinical Evaluation With a Probe Cocktail.

The botanical natural product goldenseal can precipitate clinical drug interactions by inhibiting cytochrome P450 (CYP) 3A and CYP2D6. Besides P-glycoprotein, effects of goldenseal on other clinically relevant transporters remain unknown. Established transporter-expressing cell systems were used to determine the inhibitory effects of a goldenseal extract, standardized to the major alkaloid berberine, on transporter activity. Using recommended basic models, the extract was predicted to inhibit the efflux transporter BCRP and uptake transporters OATP1B1/3. Using a cocktail approach, effects of the goldenseal product on BCRP, OATP1B1/3, OATs, OCTs, MATEs, and CYP3A were next evaluated in 16 healthy volunteers. As expected, goldenseal increased the area under the plasma concentration-time curve (AUC0-inf ) of midazolam (CYP3A; positive control), with a geometric mean ratio (GMR) (90% confidence interval (CI)) of 1.43 (1.35-1.53). However, goldenseal had no effects on the pharmacokinetics of rosuvastatin (BCRP and OATP1B1/3) and furosemide (OAT1/3); decreased metformin (OCT1/2, MATE1/2-K) AUC0-inf (GMR, 0.77 (0.71-0.83)); and had no effect on metformin half-life and renal clearance. Results indicated that goldenseal altered intestinal permeability, transport, and/or other processes involved in metformin absorption, which may have unfavorable effects on glucose control. Inconsistencies between model predictions and pharmacokinetic outcomes prompt further refinement of current basic models to include differential transporter expression in relevant organs and intestinal degradation/metabolism of the precipitant(s). Such refinement should improve in vitro-in vivo prediction accuracy, contributing to a standard approach for studying transporter-mediated natural product-drug interactions.

Substrate specificity combined with stereopromiscuity in glutathione transferase A4-4-dependent metabolism of 4-hydroxynonenal.

Conjugation to glutathione (GSH) by glutathione transferase A4-4 (GSTA4-4) is a major route of elimination for the lipid peroxidation product 4-hydroxynonenal (HNE), a toxic compound that contributes to numerous diseases. Both enantiomers of HNE are presumed to be toxic, and GSTA4-4 has negligible stereoselectivity toward them, despite its high catalytic chemospecificity for alkenals. In contrast to the highly flexible, and substrate promiscuous, GSTA1-1 isoform that has poor catalytic efficiency with HNE, GSTA4-4 has been postulated to be a rigid template that is preorganized for HNE metabolism. However, the combination of high substrate chemoselectivity and low substrate stereoselectivity is intriguing. The mechanism by which GSTA4-4 achieves this combination is important, because it must metabolize both enantiomers of HNE to efficiently detoxify the biologically formed mixture. The crystal structures of GSTA4-4 and an engineered variant of GSTA1-1 with high catalytic efficiency toward HNE, cocrystallized with a GSH-HNE conjugate analogue, demonstrate that GSTA4-4 undergoes no enantiospecific induced fit; instead, the active site residue Arg15 is ideally located to interact with the 4-hydroxyl group of either HNE enantiomer. The results reveal an evolutionary strategy for achieving biologically useful stereopromiscuity toward a toxic racemate, concomitant with high catalytic efficiency and substrate specificity toward an endogenously formed toxin.

Glutathione transferase A4-4 resists adduction by 4-hydroxynonenal.

4-Hydroxy-2-trans-nonenal (HNE) is a lipid peroxidation product that contributes to the pathophysiology of several diseases with components of oxidative stress. The electrophilic nature of HNE results in covalent adduct formation with proteins, fatty acids and DNA. However, it remains unclear whether enzymes that metabolize HNE avoid inactivation by it. Glutathione transferase A4-4 (GST A4-4) plays a significant role in the elimination of HNE by conjugating it with glutathione (GSH), with catalytic activity toward HNE that is dramatically higher than the homologous GST A1-1 or distantly related GSTs. To determine whether enzymes that metabolize HNE resist its covalent adduction, the rates of adduction of these GST isoforms were compared and the functional effects of adduction on catalytic properties were determined. Although GST A4-4 and GST A1-1 have striking structural similarity, GST A4-4 was insensitive to adduction by HNE under conditions that yield modest adduction of GST A1-1 and extensive adduction of GST P1-1. Furthermore, adduction of GST P1-1 by HNE eliminated its activity toward the substrates 1-chloro-2,4-dinitrobenzene (CDNB) and toward HNE itself. HNE effects on GST A4-4 and A1-1 were less significant. The results indicate that enzymes that metabolize HNE may have evolved structurally to resist covalent adduction by it.

Integration of Computational and Experimental Approaches to Elucidate Mechanisms of First-Pass Lymphatic Drug Sequestration and Long-Acting Pharmacokinetics of the Injectable Triple-HIV Drug Combination TLC-ART 101.

TLC-ART101 is a long-acting triple-HIV drug combination of lopinavir-ritonavir-tenofovir in one nanosuspension intended for subcutaneous injection. After a single TLC-ART 101 administration in nonhuman primates, drug concentrations in both plasma and HIV-target lymph node mononuclear cells were sustained for 2 weeks. Nevertheless, the mechanisms leading to the targeted long-acting pharmacokinetics remain elusive. Therefore, an intravenous study of TLC-ART 101 in nonhuman primates was conducted to elucidate the degree of association of drugs in vivo, estimate subcutaneous bioavailability, and refine a mechanism-based pharmacokinetic (MBPK2) model. The MBPK2 model considers TLC-ART 101 systemic drug clearances, nanoparticle-associated/dissociated species, more detailed mechanisms of lymphatic first-pass retention of associated-drugs after subcutaneous administrations, and the prediction of drug concentration time-courses in lymph node mononuclear cells. For all 3 drugs, we found a high association with the nanoparticles in plasma (>87% lopinavir-ritonavir, 97% tenofovir), and an incomplete subcutaneous bioavailability (<29% lopinavir-ritonavir, 85% tenofovir). As hypothesized by the MBPK2 model, the incomplete SC bioavailability observed is due to sequestration into a lymphatic node depot after subcutaneous absorption (unlike most intramuscular nanodrug products having near-to-injection depots), which contributes to long-acting profiles detected in plasma and target cells. This combined experimental and modeling approach may be applicable for the clinical development of other long-acting drug-combination injectables.

Pharmacodynamics of Glyburide, Metformin, and Glyburide/Metformin Combination Therapy in the Treatment of Gestational Diabetes Mellitus.

In gestational diabetes mellitus (GDM), women are unable to compensate for the increased insulin resistance during pregnancy. Data are limited regarding the pharmacodynamic effects of metformin and glyburide during pregnancy. This study characterized insulin sensitivity (SI), ß-cell responsivity, and disposition index (DI) in women with GDM utilizing a mixed-meal tolerance test (MMTT) before and during treatment with glyburide monotherapy (GLY, n = 38), metformin monotherapy (MET, n = 34), or GLY and MET combination therapy (COMBO; n = 36). GLY significantly decreased dynamic ß-cell responsivity (31%). MET and COMBO significantly increased SI (121% and 83%, respectively). Whereas GLY, MET, and COMBO improved DI, metformin (MET and COMBO) demonstrated a larger increase in DI (P = 0.05) and a larger decrease in MMTT peak glucose concentrations (P = 0.03) than subjects taking only GLY. Maximizing SI with MET followed by increasing ß-cell responsivity with GLY or supplementing with insulin might be a more optimal strategy for GDM management than monotherapy.

Pharmacodynamics of Metformin in Pregnant Women With Gestational Diabetes Mellitus and Nonpregnant Women With Type 2 Diabetes Mellitus.

Gestational diabetes mellitus is a condition similar to type 2 diabetes mellitus (T2DM) in that patients are unable to compensate for the degree of insulin resistance, and both conditions are often treated with metformin. The comparative pharmacodynamic response to metformin in these 2 populations has not been studied. This study characterized insulin sensitivity, ß-cell responsivity, and disposition index following a mixed-meal tolerance test utilizing a minimal model of glucose, insulin, and C-peptide kinetics before and during treatment with metformin. The study included women with gestational diabetes mellitus (n = 34), T2DM (n = 14), and healthy pregnant women (n = 30). Before treatment, the gestational diabetes mellitus group had significantly higher baseline (45%), dynamic (68%), static (71%), and total ß-cell responsivity (71%) than the T2DM group. Metformin significantly increased insulin sensitivity (51%) as well as disposition index (97%) and decreased mixed-meal tolerance test peak glucose concentrations (8%) in women with gestational diabetes mellitus after adjustment for gestational age-dependent effects; however, in women with T2DM metformin only significantly affected peak glucose concentrations (22%) and had no significant effect on any other parameters. Metformin had a greater effect on the change in disposition index (Δ disposition index) in women with gestational diabetes mellitus than in those with T2DM (P = .01). In conclusion, response to metformin in women with gestational diabetes mellitus is significantly different from that in women with T2DM, which is likely related to the differences in disease severity.

The reproducibility of urinary ions in manganese exposed workers.

PURPOSE: Manganese (Mn) is found in environmental and occupational settings, and can cause cognitive and motor impairment. Existing Mn exposure studies have not reached consensus on a valid and reproducible biomarker for Mn exposure. METHODS: Previously, global metabolomics data was generated from urine collected in October 2014 using mass spectrometry (MS). Nine ions were found to be different between persons exposed and unexposed to Mn occupationally, though their identity was not able to be determined. Here, we investigated these nine ions in a follow-up set of urine samples taken from the same cohort in January 2015, and in urine samples from a separate Mn-exposed cohort from Wisconsin. We fit an elastic net model fit using the nine ions found in the October 2014 data. RESULTS: The elastic net correctly predicted exposure status in 72% of the follow-up samples collected in January 2015, and the area under the curve of the receiver operating characteristic (ROC) curve was 0.8. In the Wisconsin samples, the elastic net performed no better than chance in predicting exposure, possibly due to differences in Mn exposure levels, or unmeasured occupational or environmental co-exposures. CONCLUSIONS: This work underscores the importance of taking repeat samples for replication studies when investigating the human urine metabolome, as both within- and between-person variances were observed. Validating and identifying promising results remains a challenge in harnessing global metabolomics for biomarker discovery in occupational cohorts.

Three HIV Drugs, Atazanavir, Ritonavir, and Tenofovir, Coformulated in Drug-Combination Nanoparticles Exhibit Long-Acting and Lymphocyte-Targeting Properties in Nonhuman Primates.

Drug-combination nanoparticles (DcNPs) administered subcutaneously represent a potential long-acting lymphatic-targeting treatment for HIV infection. The DcNP containing lopinavir (LPV)-ritonavir (RTV)-tenofovir (TFV), Targeted-Long-Acting-Antiretroviral-Therapy product candidate 101 (TLC-ART 101), has shown to provide long-acting lymphocyte-targeting performance in nonhuman primates. To extend the TLC-ART platform, we replaced TLC-ART 101 LPV with second-generation protease inhibitor, atazanavir (ATV). Pharmacokinetics of the ATV-RTV-TFV DcNP was assessed in macaques, in comparison to the equivalent free drug formulation and to the TLC-ART 101. After single subcutaneous administration of the DcNP formulation, ATV, RTV, and TFV concentrations were sustained in plasma for up to 14 days, and in peripheral blood mononuclear cells for 8 to 14 days, compared with 1 to 2 days in those macaques treated with free drug combination. By 1 week, lymph node mononuclear cells showed significant levels for all 3 drugs from DcNPs, whereas the free controls were undetectable. Compared with TLC-ART 101, the ATV-RTV-TFV DcNP exhibited similar lymphocyte-targeted long-acting features for all 3 drugs and similar pharmacokinetics for RTV and TFV, whereas some pharmacokinetic differences were observed for ATV versus LPV. The present study demonstrated the flexibility of the TLC-ART's DcNP platform to include different antiretroviral combinations that produce targeted long-acting effects on both plasma and cells.