Population pharmacokinetics of ravidasvir in adults with chronic hepatitis C virus infection and impact of antiretroviral treatment.

Ravidasvir (RDV) is a novel NS5A inhibitor that exhibits potent pan-genotypic inhibition of hepatitis C virus (HCV) replication. Sofosbuvir (SOF) plus RDV was demonstrated to be efficacious and safe in adults with active HCV infection, including those living with HIV (LWHIV), in the STORM-C-1 trial. We assessed the population pharmacokinetics (PK) of RDV in a sub-study nested within STORM-C-1 conducted in Thailand and Malaysia. SOF (400 mg) plus RDV (200 mg) was administered orally once daily for 12 weeks to adults with chronic HCV infection, but without cirrhosis and for 24 weeks to those with compensated cirrhosis. Intensive and sparse PK samples were collected at 4, 8, and 12 weeks after treatment initiation. Population PK parameters of RDV and the impact of covariates were evaluated using nonlinear mixed-effects modeling. Five hundred ninety-four participants were included, 235 (40%) had compensated cirrhosis, and 189 (32%) were LWHIV. RDV plasma concentrations were best described by a two-compartment model with first-order elimination. Oral clearance (CL/F) and volume of distribution (Vd/F) parameters were allometrically scaled on fat-free mass. Concomitant antiretroviral treatment (ART) increased RDV CL/F by 30%-60%, with efavirenz-based ART having the largest impact. Females had 16% lower RDV CL/F than males, and higher albumin levels reduced RDV central volume of distribution. While several covariates impact RDV CL/F and Vd/F, the effect on RDV exposures was not clinically relevant based on the efficacy data reported in this diverse Asian adult population. There were no meaningful drug-drug interactions in adults LWHIV on ART.

A phase 1 dose-escalation and dose-expansion study to assess the safety and efficacy of CKD-516, a novel vascular disrupting agent, in combination with Irinotecan in patients with previously treated metastatic colorectal cancer.

Introduction The combination of an anti-angiogenic agent with cytotoxic chemotherapy is a standard treatment strategy for metastatic colorectal cancer. CKD-516 is an oral vascular disrupting agent that was preliminarily shown to be safe and efficacious as a monotherapy in refractory solid cancers. We evaluated the recommended phase 2 dose, safety, and preliminary efficacy of CKD-516 in combination with irinotecan in treatment-refractory metastatic colorectal cancer. Methods This phase 1 dose-escalation and dose-expansion study included patients with treatment-refractory metastatic colorectal cancer. CKD-516 tablets were administered for five consecutive days followed by two days off in combination with intravenous irinotecan (120 mg/m2) administered on day one of each treatment cycle every two weeks. A traditional 3 + 3 dose-escalation design was used. Results In total, 16 and 23 patients were enrolled in the dose-escalation and dose-expansion cohorts, respectively. The most common adverse events included diarrhea (79%), nausea (74%), vomiting (67%), and neutropenia (62%). No dose-limiting toxicity occurred, and the recommended phase 2 dose was determined at CKD-516/irinotecan doses of 11/120 mg/m2. No cases of cardiac ischemia, cardiac dysfunction, or thromboembolism were reported. Among the 34 patients with available tumor response assessments, one patient achieved partial response (3%) and 26 patients achieved stable disease (76%). The median progression-free survival and overall survival were 4.1 and 11.6 months, respectively. Conclusion This phase 1 study showed that the combination of oral CKD-516 and irinotecan is safe and tolerable in metastatic, treatment-refractory colorectal patients and showed favorable efficacy outcomes. Further studies to confirm these preliminary findings are warranted. Trial registration number NCT03076957 (Registered at March 10, 2017).

A rapid ultra high performance liquid chromatography-tandem mass spectrometry method for the quantification of daidzein, its valine carbamate prodrug, and glucuronide in rat plasma samples: Comparison of the pharmacokinetic behavior of daidzine valine carbamate prodrugs.

Two valine carbamate prodrugs of daidzein were designed to improve its bioavailability. To compare the pharmacokinetic behavior of these prodrugs with different protected phenolic hydroxyl groups of daidzein, a rapid and sensitive method for simultaneous quantification of daidzein, its valine carbamate prodrug, and daidzein-7-O-glucuronide in rat plasma was developed and validated in this study. The samples were processed using a fast one-step protein precipitation method with methanol added to 50 µL of plasma and were analyzed by ultra-high performance liquid chromatography with tandem mass spectrometry. To improve the selectivity, peak shape, and peak elution, several key factors, especially stationary phase and the composition of the mobile phase, were tested, and the analysis was performed using the Kinetex® C18 column (100 × 2.1 mm, 2.6 µm) within only 2.6 min under optimal conditions. The established method exhibited good linearity over the concentration range of 2.0-1000 ng/mL for daidzein, and 8.0-4000 ng/mL for the prodrug and daidzein-7-O-glucuronide. The accuracy of the quality control samples was between 95.5 and 110.2% with satisfactory intra- and interday precision (relative standard deviation values < 10.85%), respectively. This sensitive, rapid, low-cost, and high-throughput method was successfully applied to compare the pharmacokinetic behavior of different daidzein carbamate prodrugs.

Development and optimization of a high-throughput HPLC-MS/MS method for the simultaneous determination of naringenin and its valine carbamate prodrug in rat plasma.

A valine carbamate prodrug of naringenin (NAR) called 4'V was synthesized to enhance its oral bioavailability because of low water solubility and poor membrane permeability of NAR. This study developed and fully validated a sensitive, rapid, and robust HPLC-MS/MS method for the simultaneous determination of NAR and 4'V in plasma. The analytes were treated using liquid-liquid extraction, separated on a Phenomenex Kinetex XB-C18 column, and detected using a triple-quadrupole tandem mass spectrometer equipped with an electrospray ionization interface. The analytes were eluted within only 4 min by gradient procedure. The excellent linear correlations were validated over the range of 4-400 ng/mL (r = 0.9990) for NAR and 2-2000 ng/mL (r = 0.9951) for 4'V, with lower limits of quantification of 4 and 2 ng/mL, respectively. For all quality control samples, the intra-day and inter-day precision and accuracy were within ±15%. The validated method was economical, high throughput, and reliable and was first successfully applied to a pharmacokinetic study of NAR and 4'V after oral administration to Sprague-Dawley rats. The results of the pharmacokinetic study demonstrated that the idea of amino acid carbamate prodrug is a promising strategy to improve the bioavailability of NAR.

Determination and structural characterization of ravidasvir metabolites by LC coupled to triple quadrupole linear ion trap MS: Application to pharmacokinetics and phase I metabolism in rats.

Hepatitis C virus (HCV) is an infectious disease that has become a global clinical issue because of its significant morbidity and mortality. Novel anti-hepatitis C drugs are continuously developed to decrease the pervasiveness of the infection globally. A synthetic ravidasvir, benzimidazole-naphthylene-imidazole derivatives, has been used as an anti-HCV drug. This study determined the metabolites of ravidasvir and its pharmacokinetics in rats using information-dependent acquisition and multiple reaction monitoring scanning modes in linear ion trap LC-MS/MS instrument, respectively. Two time-programming linear-gradient chromatographic methods were employed using a Kinetex C18 column (50 × 3 mm, 2.6 µm) and a Luna HILIC column (100 × 4.6 mm, 3 µm) for the qualitative and quantitative determination of ravidasvir and its metabolites, respectively. In silico prediction where sites in a molecule are susceptible to metabolism by cytochrome P450 was implemented, which helped in proposing the metabolic pathway of ravidasvir. The most dominant metabolite in rat liver microsomal samples was oxidative ravidasvir, where one O-demethylated metabolite and eight isomers of the oxidative ravidasvir metabolites were identified. The study provides essential data for proposing the metabolic pathway and successfully applied it to determine the pharmacokinetics of ravidasvir in rat plasma.

A Systematic Study of the In Vitro Pharmacokinetics and Estimated Human In Vivo Clearance of Indole and Indazole-3-Carboxamide Synthetic Cannabinoid Receptor Agonists Detected on the Illicit Drug Market.

In vitro pharmacokinetic studies were conducted on enantiomer pairs of twelve valinate or tert-leucinate indole and indazole-3-carboxamide synthetic cannabinoid receptor agonists (SCRAs) detected on the illicit drug market to investigate their physicochemical parameters and structure-metabolism relationships (SMRs). Experimentally derived Log D7.4 ranged from 2.81 (AB-FUBINACA) to 4.95 (MDMB-4en-PINACA) and all SCRAs tested were highly protein bound, ranging from 88.9 ± 0.49% ((R)-4F-MDMB-BINACA) to 99.5 ± 0.08% ((S)-MDMB-FUBINACA). Most tested SCRAs were cleared rapidly in vitro in pooled human liver microsomes (pHLM) and pooled cryopreserved human hepatocytes (pHHeps). Intrinsic clearance (CLint) ranged from 13.7 ± 4.06 ((R)-AB-FUBINACA) to 2944 ± 95.9 mL min-1 kg-1 ((S)-AMB-FUBINACA) in pHLM, and from 110 ± 34.5 ((S)-AB-FUBINACA) to 3216 ± 607 mL min-1 kg-1 ((S)-AMB-FUBINACA) in pHHeps. Predicted Human in vivo hepatic clearance (CLH) ranged from 0.34 ± 0.09 ((S)-AB-FUBINACA) to 17.79 ± 0.20 mL min-1 kg-1 ((S)-5F-AMB-PINACA) in pHLM and 1.39 ± 0.27 ((S)-MDMB-FUBINACA) to 18.25 ± 0.12 mL min-1 kg-1 ((S)-5F-AMB-PINACA) in pHHeps. Valinate and tert-leucinate indole and indazole-3-carboxamide SCRAs are often rapidly metabolised in vitro but are highly protein bound in vivo and therefore predicted in vivo CLH is much slower than CLint. This is likely to give rise to longer detection windows of these substances and their metabolites in urine, possibly as a result of accumulation of parent drug in lipid-rich tissues, with redistribution into the circulatory system and subsequent metabolism.

Effect of Hemodialysis on Efficacy and Pharmacokinetics of Sofosbuvir Coformulated with Either Daclatasvir or Ledipasvir in Patients with End-Stage Renal Disease.

BACKGROUND/AIMS: Direct-acting antivirals (DAAs) play a key role in the eradication of hepatitis C virus (HCV) infection. However, limited data are available on DAA for treating HCV infection in hemodialysis (HD) patients. This study was to evaluate the pharmacokinetic characteristics and effectiveness of daclatasvir/sofosbuvir (DAC/SOF) and ledipasvir/SOF (LDV/SOF) in HD patients. METHODS: Seven patients were given SOF coadministered with DAC or LDV once daily for 12 weeks. The plasma concentrations of SOF007, DAC, and LDV were determined by high-performance liquid chromatography-electrospray ionization tandem mass spectrometry. RESULTS: A sustained virologic response in week 12 (SVR12) was achieved in 6 (100%) patients, except for 1 patient dying due to severe cerebral hemorrhage not related to antiviral therapy. The extraction ratio of SOF007 was 66.67%, and the estimated HD clearance of SOF007 was 5.65 L/h. CONCLUSION: The combination of SOF with either DAC or LDV is well tolerated and offers high SVR12 in HD patients.

Comparing pharmacologic mechanism of action for the vesicular monoamine transporter 2 (VMAT2) inhibitors valbenazine and deutetrabenazine in treating tardive dyskinesia: does one have advantages over the other?

The two approved treatments for tardive dyskinesia both inhibit the vesicular monoamine transporter type 2 (VMAT2) yet have pharmacologic properties that distinguish one from the other. Knowing these differences may help optimize which treatment to select for individual patients.

Transport of valine across the small intestinal epithelium in pigs fed different valine levels and Bacillus subtilis.

Mutants of Bacillus subtilis overproducing valine (B. subtilis VAL) could be an approach to supply pigs dietary valine (Val). In the study, 18 gilts were fed: (i) negative diet with a standardized ileal digestible (SID) Val:Lys of 0.63:1 (Neg); (ii) Neg added B. subtilis VAL (1.28 × 1011  cfu/kg as-fed) or; (iii) Neg added L-Val to a Val:Lys of 0.69:1. Using the Ussing chamber method, the study aimed to investigate whether (i) the diets affect intestinal transport of additions of 0, 5, 10 or 20 mmol Val/L from the mucosal to the serosal side and (ii) the B. subtilis VAL contributes to a net transport of Val produced in situ. The results showed that the Isc (ΔIscVal ) and release of Val to the serosal side solution (Srel ; µmol cm-2  min-1 ) increased with Val addition (linear and quadratic, p < .0001) but was similar for 5, 10 or 20 mmol Val/L and not affected by diet. No net transport of in situ produced Val by B. subtilis VAL was detected. In conclusion, feeding a Val-deficient diet with or without B. subtilis VAL or a Val sufficient diet did not affect the Val transport across intestinal epithelia. No in situ Val production by B. subtilis VAL was observed in the Ussing chambers.

In Silico Absorption Analysis of Valacyclovir in Wildtype and Pept1 Knockout Mice Following Oral Dose Escalation.

PURPOSE: We developed simulation and modeling methods to predict the in vivo pharmacokinetic profiles of acyclovir, following escalating oral doses of valacyclovir, in wildtype and Pept1 knockout mice. We also quantitated the contribution of specific intestinal segments in the absorption of valacyclovir in these mice. METHODS: Simulations were conducted using a mechanistic advanced compartmental absorption and transit (ACAT) model implemented in GastroPlus™. Simulations were performed for 3 h post-dose in wildtype and Pept1 knockout mice following single oral doses of 10, 25, 50 and 100 nmol/g valacyclovir, and compared to experimentally observed plasma concentration-time profiles of acyclovir. RESULTS: Good fits were obtained in wildtype and Pept1 knockout mice. Valacyclovir was primarily absorbed from duodenum (42%) and jejunum (24%) of wildtype mice, with reduced uptake from ileum (3%) and caecum/colon (1%), for a total of 70% absorption. In contrast, the absorption of valacyclovir in Pept1 knockout mice was slow and sustained throughout the entire intestinal tract in which duodenum (4%), jejunum (14%), ileum (10%) and caecum/colon (12%) accounted for a total of 40% absorption. CONCLUSION: The ACAT model bridged the gap between in situ and in vivo experimental findings, and facilitated our understanding of the complicated intestinal absorption processes of valacyclovir.

Efficacy, safety and pharmacokinetics of simeprevir and TMC647055/ritonavir with or without ribavirin and JNJ-56914845 in HCV genotype 1 infection.

BACKGROUND: A Phase 2a, open-label study (NCT01724086) was conducted to assess the efficacy and safety of a once-daily, 2-direct-acting-antiviral-agent (2-DAA) combination of simeprevir + TMC647055/ritonavir ± ribavirin and of the 3-DAA combination of simeprevir + TMC647055/ritonavir + JNJ-56914845 in chronic hepatitis C virus genotype (GT)1-infected treatment-naïve and prior-relapse patients. METHODS: The study comprised four 12-week treatment panels: Panel 1 (n = 10; GT1a) and Panel 2-Arm 1 (n = 12; GT1b): simeprevir 75 mg once daily + TMC647055 450 mg once daily/ritonavir 30 mg once daily + ribavirin 1000-1200 mg/day; Panel 2-Arm 2 (n = 9; GT1b): simeprevir 75 mg + TMC647055 450 mg/ritonavir 30 mg without ribavirin; Panel 3: simeprevir 75 mg + TMC647055 600 mg/ritonavir 50 mg with (Arm 1: GT1a; n = 7) or without (Arm 2: GT1b; n = 8) ribavirin; Panel 4: simeprevir 75 mg + TMC647055 450 mg/ritonavir 30 mg + JNJ-56914845 30 mg once daily (Arm 1: n = 22; GT1a/GT1b) or 60 mg once daily (Arm 2: n = 22; GT1a/GT1b). Primary endpoint was sustained virologic response 12 weeks after end of treatment (12 weeks of combination treatment; SVR12). RESULTS: In Panel 1 and Panel 2-Arm 1, 5/10 and 6/12 (50%) GT1a/GT1b + ribavirin patients achieved SVR12, versus 3/9 (33%) GT1b without ribavirin patients in Panel 2-Arm 2. In Panel 3-Arm 1 and Panel 3-Arm 2, 6/7 (86%) GT1a + ribavirin and 4/8 (50%) GT1b without ribavirin patients, respectively, achieved SVR12. In Panel 4, 10/14 (71%) and 14/15 (93%) GT1a patients in Arms 1 and 2 achieved SVR12 compared with 8/8 and 7/7 (100%) GT1b patients in each arm, respectively. No deaths, serious adverse events (AEs), Grade 4 AEs or AEs leading to treatment discontinuation occurred. CONCLUSIONS: The 2- and 3-DAA combinations were well tolerated. High SVR rates of 93% and 100% in GT1a- and GT1b-infected patients, respectively, were achieved in this study by combining simeprevir with JNJ-56914845 60 mg and TMC647055/ritonavir. TRIAL REGISTRATION: NCT01724086 (date of registration: September 26, 2012).

Platform model describing pharmacokinetic properties of vc-MMAE antibody-drug conjugates.

Antibody-drug conjugates (ADCs) developed using the valine-citrulline-MMAE (vc-MMAE) platform, consist of a monoclonal antibody (mAb) covalently bound with a potent anti-mitotic toxin (MMAE) through a protease-labile vc linker. Recently, clinical data for a variety of vc-MMAE ADCs has become available. The goal of this analysis was to develop a platform model that simultaneously described antibody-conjugated MMAE (acMMAE) pharmacokinetic (PK) data from eight vc-MMAE ADCs, against different targets and tumor indications; and to assess differences and similarities of model parameters and model predictions, between different compounds. Clinical PK data of eight vc-MMAE ADCs from eight Phase I studies were pooled. A population PK platform model for the eight ADCs was developed, where the inter-compound variability (ICV) was described explicitly, using the third random effect level (ICV), and implemented using LEVEL option of NONMEM 7.3. The PK was described by a two-compartment model with time dependent clearance. Clearance and volume of distribution increased with body weight; volume was higher for males, and clearance mildly decreased with the nominal dose. Michaelis-Menten elimination had only minor effect on PK and was not included in the model. Time-dependence of clearance had no effect beyond the first dosing cycle. Clearance and central volume were similar among ADCs, with ICV of 15 and 5%, respectively. Thus, PK of acMMAE was largely comparable across different vc-MMAE ADCs. The model may be applied to predict PK-profiles of vc-MMAE ADCs under development, estimate individual exposure for the subsequent PK-pharmacodynamics (PD) analysis, and project optimal dose regimens and PK sampling times.

Evaluation of [18 F]BR420 and [18 F]BR351 as radiotracers for MMP-9 imaging in colorectal cancer.

MMP-9 is a zinc-dependent endopeptidase that is involved in the proteolytic degradation of the extracellular matrix and plays an important role in cancer migration, invasion, and metastasis. The aim of this study was to evaluate the potential of MMP-tracers [18 F]BR420 and [18 F]BR351 for MMP-9 imaging in a colorectal cancer xenograft model. [18 F]BR420 and [18 F]BR351 were synthesized using an automated synthesis module. For [18 F]BR420, a novel and improved radiosynthesis was developed. Plasma stability and MMP-9-targeting capacity of both radiotracers was compared in the Colo205 colorectal cancer model. MMP-9 and MMP-2 expression levels in the tumors were evaluated by immunohistochemistry and in situ zymography. µPET imaging as well as ex vivo biodistribution revealed a higher tumor uptake for [18 F]BR420 (3.15% ± 0.03% ID/g vs 0.94% ± 0.18% ID/g for [18 F]BR351 at 2 hours pi) but slower blood clearance compared with [18 F]BR351. [18 F]BR351 was quickly metabolized in plasma with 20.28% ± 5.41% of intact tracer remaining at 15 minutes postinjection (PI). By contrast, [18 F]BR420 displayed a higher metabolic stability with >86% intact tracer remaining at 2 hours PI. Immunohistochemistry revealed the presence of MMP-9 and MMP-2 in the tumor tissue, which was confirmed by in situ zymography. However, an autoradiography analysis of tracer distribution in the tumors did not correlate with MMP-9 expression. [18 F]BR420 displayed a higher tumor uptake and higher stability compared with [18 F]BR351 but a low tumor-to-blood ratio and discrepancy between tracer distribution and MMP-9 immunohistochemistry. Therefore, both tracers will not be usefulness for MMP-9 imaging in colorectal cancer.

Discovery of ravidasvir (PPI-668) as a potent pan-genotypic HCV NS5A inhibitor.

This Letter describes the synthesis, representative structure activity relationship (SAR), activity and PK profiles of a series of functionalized benzimidazole-naphthylene-imidazole derivatives as HCV NS5A inhibitors. This effort successfully led to the discovery of ravidasvir (PPI-668), which has been well tolerated and shown high sustained viral response rates as a key component in all-oral combination regimens in multiple human clinical trials.

Development of a paediatric population pharmacokinetic model for valacyclovir from literature non-compartmental values originating from sparse studies and Bayesian priors: a simulation study.

A preliminary population pharmacokinetic (PopPK) model of valacyclovir in children was developed from non-compartmental analysis (NCA) parameter values from literature, including several age groups, combined with Bayesian priors from a PopPK model of acyclovir, the active metabolite of valacyclovir, from literature too. Also a simulation study was carried out to evaluate the performance of various modelling choices related to the estimation of model parameters from NCA parameters originating from sparse PK studies. Assuming a one-compartment model with first order absorption, a mixed effects, meta-analysis approach was utilized which allows accounting the random intergroup variability, the detection of covariates and the application of informative Bayesian priors on the parameters. The conclusions from the simulation study calculating bias and precision for various cases, were that a model which takes explicitly into account the sampling schedule, performs better than a model using the theoretical expressions of calculating the NCA parameters. Also by using the geometric rather than the arithmetic means of NCA parameters, less biased results are obtained. These findings guided the choices for the valacyclovir model, for which informative priors from a PopPK model of acyclovir were applied for some of the parameters, in order to include a richer covariate model for clearance, not supported by the NCA dataset and a value for bioavailability. This preliminary valacyclovir model can be used in simulations to provide dosage recommendations for children of various ages and to help design more efficiently prospective clinical trials.

[Injectable hospital preparation of valine labeled with the carbon 13 and nitrogen 15 (5 mg/mL) for a clinical trial on the brain tumor metabolism: Pharmaceutical control of active pharmaceutical ingredient and stability study of the finished product]. / Préparation hospitalière injectable de valine marquée au carbone 13 et à l'azote 15 (5mg/mL) pour un essai clinique sur le métabolisme tumoral cérébral : contrôle pharmaceutique de la substance active et étude de stabilité du produit fini.

INTRODUCTION: The L-Valine labeled (L-[U-(13)C,(15)N] Val) is a stable isotopic tracer administered by parenteral route within the framework of a new clinical research program concerning the brain tumor metabolism. To meet regulatory requirements and have ready to use solution with an expiration date, a pharmaceutical control of active pharmaceutical ingredient followed by stability study of hospital preparation were realised. MATERIALS AND METHODS: After the pharmaceutical control of the L-[U-(13)C,(15)N] Val, the hospital preparation was prepared according to the good manufacturing preparation. Prepared bottles were stored at 5°C±3°C and 25°C±2°C for six months. The stability of the preparation was determined by physico-chemical controls (pH, osmolality, sub-visible particles, L-[U-(13)C,(15)N] Val concentration, sodium concentration, isotopic enrichment) and microbiological (bacterial endotoxin and sterility). RESULTS: Concentrations of L-[U-(13)C, (15)N] Val and sodium does not significantly decrease during the stability study. In parallel, no change in pH and osmolality were highlighted. Isotopic enrichment higher than 99.9% reflected the stability of labeling of L-valine molecule. The sub-visible particles, the bacterial endotoxin and sterility were in accordance with the European Pharmacopoeia attesting limpidity, apyrogenicity and sterility of this injectable preparation. DISCUSSION AND CONCLUSION: The stability of this hospital preparation of L-[U-(13)C, (15)N] Val has been demonstrated for six months at 5°C±3°C and 25°C±2°C, ensuring a parenteral administration as part of the clinical trial.

Pharmacokinetics of a CCR5 inhibitor in rhesus macaques following vaginal, rectal and oral application.

OBJECTIVES: This study measured and compared the pharmacokinetics of CMPD167, a small molecule antiretroviral CCR5 inhibitor with potential as an HIV microbicide, following vaginal, rectal and oral administration in rhesus macaques. METHODS: A vaginal hydroxyethylcellulose (HEC) gel, a rectal HEC gel, a silicone elastomer matrix-type vaginal ring and an oral solution, each containing CMPD167, were prepared and administered to rhesus macaques pretreated with Depo-Provera. CMPD167 concentrations in vaginal fluid, vaginal tissue (ring only), rectal fluid and blood plasma were quantified by HPLC-mass spectrometry. RESULTS: CMPD167 concentrations measured in rectal fluid, vaginal fluid and blood plasma were highly dependent on both the route of administration and the formulation type. Although rectal and vaginal fluid concentrations were highest when CMPD167 was administered locally (via either gel or ring), lower concentrations of the drug were also measured in these compartments following administration at the remote mucosal site or orally. CMPD167 levels in the vaginal and rectal fluid following oral administration were relatively low compared with local administration. CONCLUSIONS: The study provides clear evidence for vaginal-rectal and rectal-vaginal drug transfer pathways and suggests that oral pre-exposure prophylaxis with CMPD167 may be less efficacious at preventing sexual transmission of HIV-1 than topically applied products.

Characterization of glycidol-hemoglobin adducts as biomarkers of exposure and in vivo dose.

Hemoglobin adducts have been used as biomarkers of exposure to reactive chemicals. Glycidol, an animal carcinogen, has been reported to form N-(2,3-dihydroxy-propyl)valine adducts to hemoglobin (diHOPrVal). To support the use of these adducts as markers of glycidol exposure, we investigated the kinetics of diHOPrVal formation and its elimination in vitro and in vivo. Five groups of rats were orally administered a single dose of glycidol ranging from 0 to 75mg/kg bw, and diHOPrVal levels were measured 24h after administration. A dose-dependent increase in diHOPrVal levels was observed with high linearity (R(2)=0.943). Blood sampling at different time points (1, 10, 20, or 40days) from four groups administered glycidol at 12mg/kg bw suggested a linear decrease in diHOPrVal levels compatible with the normal turnover of rat erythrocytes (life span, 61days), with the calculated first-order elimination rate constant (kel) indicating that the diHOPrVal adduct was chemically stable. Then, we measured the second-order rate constant (kval) for the reaction of glycidol with N-terminal valine in rat and human hemoglobin in in vitro experiments with whole blood. The kval was 6.7±1.1 and 5.6±1.3 (pmol/g globin per µMh) in rat and human blood, respectively, indicating no species differences. In vivo doses estimated from kval and diHOPrVal levels were in agreement with the area under the (concentration-time) curve values determined in our earlier toxicokinetic study in rats. Our results indicate that diHOPrVal is a useful biomarker for quantification of glycidol exposure and for risk assessment.

Nonprotein nitrogen is absorbed from the large intestine and increases nitrogen balance in growing pigs fed a valine-limiting diet.

Nitrogen absorption from the large intestine, largely as ammonia and possibly as amino acids (AAs), is generally thought to be of little nutritional value to nonruminant animals and humans. Ammonia-nitrogen absorbed from the large intestine, however, may be recycled into the small intestine as urea and incorporated into microbial AAs, which may then be used by the host. A cecal infusion study was performed to determine the form in which nitrogen is absorbed from the large intestine and the impact of large intestine nitrogen supply on nitrogen balance in growing pigs. Eighteen cecally cannulated barrows (initial body weight: 22.4 ± 1.2 kg) were used to determine the effect of supplying nitrogen into the large intestine from either casein or urea on whole-body nitrogen retention and urea kinetics. Treatments were cecal infusions of saline (control), casein, or urea with nitrogen infused at a rate of 40% of nitrogen intake. In a subsample of 9 pigs, (15)N(15)N-urea was infused via i.v. during the nitrogen-balance period to determine urea kinetics. All pigs were fed a valine-limiting cornstarch-soybean meal-based diet. More than 80% of infused nitrogen was apparently absorbed. Urea flux and urinary nitrogen excretion increased (P ≤ 0.05) by the same amount for both nitrogen sources, but this increase did not fully account for the increase in nitrogen absorption from the large intestine. Whole-body nitrogen retention improved with nitrogen infusions (129 vs. 114 g/d; P < 0.01) and did not differ (P > 0.05) between nitrogen sources. Absorption of nitrogen from the large intestine appears to be in the form of nonprotein nitrogen, which appears to be returned to the small intestine via urea and used there for microbial AA production and should therefore be considered when determining nitrogen and AA supply and requirements.