Low Plasma Exposure Research Articles

Exploring the Impact of Pharmacological Target-Mediated Low Plasma Exposure in Lead Compound Selection in Drug Discovery – A Modeling Approach

Exploring the Impact of Pharmacological Target-Mediated Low Plasma Exposure in Lead Compound Selection in Drug Discovery – A Modeling Approach

Brain Exposure to the Macrocyclic ALK Inhibitor Zotizalkib is Restricted by ABCB1, and Its Plasma Disposition is Affected by Mouse Carboxylesterase 1c.

Zotizalkib (TPX-0131), a fourth-generation macrocyclic anaplastic lymphoma kinase (ALK) inhibitor, is designed to overcome resistance due to secondary ALK mutations in non-small cell lung cancer (NSCLC). We here evaluated the pharmacokinetic roles of the ABCB1 (P-gp/MDR1) and ABCG2 (BCRP) efflux transporters, OATP1 influx transporters and the metabolizing enzymes CES1 and CYP3A in plasma and tissue disposition of zotizalkib after oral administration in relevant mouse models. Zotizalkib was efficiently transported by hABCB1 in vitro. In vivo, a significant ∼9-fold higher brain-to-plasma ratio was observed in Abcb1a/b-/- and Abcb1a/b;Abcg2-/- compared to wild-type mice. No change in brain disposition was observed in Abcg2-/- mice, suggesting that mAbcb1a/b markedly restricts the brain accumulation of zotizalkib. ABCB1-mediated efflux of zotizalkib was completely inhibited by elacridar, a dual ABCB1/ABCG2 inhibitor, increasing brain exposure without any signs of acute CNS-related toxicities. In Oatp1a/b-/- mice, no marked changes in plasma exposure or tissue-to-plasma ratios were observed, indicating that zotizalkib is not a substantial in vivo substrate for mOatp1a/b. Zotizalkib may further be metabolized by CYP3A4 but only noticeably at low plasma concentrations. In Ces1-/- mice, a 2.5-fold lower plasma exposure was seen compared to wild-type, without alterations in tissue distribution. This suggests increased plasma retention of zotizalkib by binding to the abundant mouse plasma Ces1c. Notably, the hepatic expression of human CES1 did not affect zotizalkib plasma exposure or tissue distribution. The obtained pharmacokinetic insights may be useful for the further development and optimization of therapeutic efficacy and safety of zotizalkib and related compact macrocyclic ALK inhibitors.

Formation of orientation-dependent surface morphologies on tungsten after low energy helium plasma exposure: multiscale characterization and new insights

In ITER, the helium (He) impurity produced by the deuterium-tritium reaction will bombard the tungsten (W) divertor armor at the strike points. Consequently, strong interaction occurs therein that both impact the performance of the plasmas and the lifetime of the divertor. Despite an ever-increasing understanding of this interaction, some experimental phenomena remain mysterious, especially the formation of orientation-dependent surface morphologies. Here, we combine multiscale experimental characterization and theoretical models to shed new light on this problem. After low-energy He plasma exposure in a linear plasma generator, the polycrystalline W surface developed various morphologies. Through electron backscatter diffraction analysis, we found that the {111} grains developed cube-corner structures, the {110} grains developed ripple structures, whereas the {100} grains remained smooth. Then, electron-transparent lamellae were extracted from such grains to observe the subsurface He bubbles by transmission electron microscopy. The volume density, size distribution, and depth range of the He bubbles weakly depend on the crystallographic orientation, suggesting that the migration of W atoms causes the morphology variety. Accordingly, we proposed a two-stage formation mechanism. First, W atoms generated by over-pressurized He bubbles glide on the slip plane and in the slip direction to reach the surface, forming characteristic patterns that are enclosed by the slip traces. Second, morphological instability drives the evolution of the surface patterns, in which the initial surface structure and surface self-diffusion kinetics mediate. The proposed mechanism has been incorporated into a topographical instability model to enable asemi-quantitative analysis. The obtained new insights are valuable to the impurity control of the core plasmas and the lifetime analysis of the divertor for ITER.

The synergistic effect of Huangqi Gegen decoction on thrombosis relates to the astragalus polysaccharide-improved oral delivery of puerarin

Ethno-pharmacological relevanceHuangqi Gegen decoction (HGD), which comprises Astragali Radix (AR) and Puerariae Radix (PR), is widely used to treat thrombosis in China. However, the mechanism underlying its synergistic effect in thrombosis treatment remains unclear. Aim of the studyFollowing PR administration, low plasma exposure was reported for its primary ingredients. In this regard, this study examined the effect of AR on PR's antithrombotic efficacy with respect to the impact of Astragalus Polysaccharide (APS) on the oral delivery of Puerarin (PUE). Materials and methodsTo evaluate the synergistic effect of HGD, a thrombus mice model was established via intraperitoneal injection of carrageenan. After treatment, histopathological observations were made, and the proportion of thrombus length in the tail, as well as the plasma APTT, PT, INR, and FIB levels, were detected. Molecular docking was employed to assess the PR ingredients that could inhibit the HMGB1/NF-κB/NLRP3 pathway. The Pharmacokinetics of PR ingredients in rats were also compared between the PR and HGD groups. Moreover, the effect of APS on the solubility, intestinal absorption, and pharmacokinetics of PUE was evaluated. Furthermore, the impact of APS on the antithrombotic efficacy of PUE was assessed. ResultsIn mice, AR enhanced the antithrombotic effect of PR. This improved PR effect was associated with isoflavones-induced downregulation of the HMGB1/NF-κB/NLRP3 pathway. The synergistic effect resulting from the compatibility of HGD components was primarily achieved by improving the plasma exposure of PR isoflavones. Specifically, APS enhanced PUE's water solubility through the formation of self-assembly Nanoparticles, increasing its intestinal absorption and oral bioavailability, which, in turn, suppressed the HMGB1/NF-κB/NLRP3 pathway, thus improving its antithrombotic effect. ConclusionsOur findings revealed that APS improved PUE's plasma exposure, enhancing its inhibitory effect on the HMGB1/NF-κB/NLRP3 pathway. This mechanism presents a key aspect of the synergistic effect of HGD compatibility in thrombosis treatment.

Evolution of irradiation damage in tungsten matrix and Y2O3 phase after low energy helium plasma exposure

Tungsten is the preferred material for the first wall. In this paper, W-0.5 %wt Y2O3 was selected for the exposure test of helium plasma, so that fuzz tendrils of considerable thickness were formed on its surface. By using ultrasonic dispersion, the tendril dispersion was obtained and observed through TEM. The fuzz tendrils on the W matrix surface were seen to have a complete tungsten crystal structure, along with bubbles of different sizes. The outer layer of the tendril is composed of an amorphous material, which is visible on the surface of the fuzz tendril. This is likely due to the subsequent of helium plasma exposure damage. Fuzz tendrils only appeared on the W matrix, whereas Y2O3 particles created nano-protrusions and samll cracks on the surface. The nano-protrusion morphology and EDS analysis, including the lack of Y in fuzz tendrils, indicate that Y2O3 particles were unable to form a fuzzy structure. It is evident that the defects distribution of W matrix and Y2O3 particles is altered due to helium plasma exposure. Near the surface of Y2O3 particles, fewer but larger bubbles were observed, whereas further away, smaller but denser bubbles were seen. In W matrix, bubbles were formed at a deeper level and were larger than the deepest bubbles in Y2O3 particles, likely caused by the lower migration energy. The different responses of W matrix and Y2O3 particles to helium plasma exposure have combined to further reveal the potential of increasing the plasma exposure resistance of plasma-oriented tungsten based materials.

Modulation of Extravascular Binding of Recombinant Factor IX Impacts duration of Efficacy in Mouse Models.

There is an emerging concept that in addition to circulating coagulation factor IX (FIX), extravascular FIX contributes to hemostasis. Evaluate efficacy of extravascular FIX using animal models of tail clip bleeding and ferric chloride induced thrombosis. Mutant rFIX proteins with described enhanced (rFIXK5R) or reduced (rFIXK5A) binding to extracellular matrix were generated and characterized using in vitro aPTT, one stage clotting and modified FX assays. Using hemophilia B mice, pharmacokinetic parameters and in vivo efficacy of these proteins was compared against rFIX wild type protein (rFIXWT) in a tail clip bleeding and FeCl3-induced thrombosis model. Respective tissue disposition of FIX was evaluated using immunofluorescence. In vitro characterization demonstrated comparable clotting activity of rFIX proteins. Pharmacokinetic profile showed that rFIXK5A displayed highest plasma exposure compared to rFIXWT and rFIXK5R. Immunofluorescence evaluation of liver tissue showed that rFIXK5R was detectable up to 24h, where as rFIXWT and rFIXK5A were detectable only at 15 minutes. In the tail clip bleeding model, rFIXK5R displayed significant hemostatic protection against bleeding incidence for up to 72h post intravenous administration of 50 IU/kg, whereas the efficacy of rFIXK5A was already reduced at 24h. Similarly, in the mesenteric artery thrombus model, rFIXK5R and rFIXWT demonstrated prolonged efficacy compared to rFIXK5A. Using two different in vivo models of hemostasis and thrombosis, we demonstrate that mutated rFIX protein with enhanced binding (rFIXK5R) to extravascular space confers prolonged hemostatic efficacy in vivo despite lower plasma exposure, while rFIXK5A rapidly lost its efficacy despite higher plasma exposure.

Abiraterone decanoate (PRL-02): Pharmacology of a single intramuscular (IM) depot injection compared to oral abiraterone acetate (AA) in intact male rats.

160 Background: Oral AA is a standard of care for metastatic prostate cancer. The recommended daily AA 1000 mg dose produces high peak and low trough plasma concentrations that are associated with safety issues (e.g., hepatotoxicity) and inadequate efficacy, respectively. PRL-02 is a novel abiraterone prodrug undergoing evaluation in patients with advanced prostate cancer (NCT04729114). In chemically-castrate monkeys, single doses of PRL-02 suppressed androgens for 14 weeks at much lower plasma exposures than AA (Moore et al, ASCO GU 2021). The present study in intact male rats evaluated the systemic exposures and activity of PRL-02 compared to daily oral AA at 7 and/or 14 days post-treatment start. Methods: Sexually mature male rats (n=4 per timepoint) were administered a single IM dose of PRL-02 (90 mg/kg), daily AA (90 mg/kg) or IM/oral vehicle (VEH). Biological samples were collected on Day 7 (PRL-02/VEH; 0h) or Day 14 (PRL-02/AA/VEH; 2, 6 and 24h) post-dosing. Drug and androgen concentrations were determined by LC-MS/MS. Testicular CYP17 hydroxylase activity was measured ex vivo on Day 14. Results: The Day 14 plasma exposure from abiraterone was greater from AA (5.6 - 210 ng/mL) than from PRL-02 (1.15 – 1.37 ng/mL). However, for Day 14 tissue exposures (AUC0-24) from ‘total abiraterone equivalents’ (TAE; concentration of free abiraterone plus abiraterone from prodrug) were greater from PRL-02 in adrenal, testes, lymph node and bone target tissues than from oral AA; exposures from AA were only greater in non-target tissues such as liver and brain (Table). There was no measurable Day 14 CYP17 hydroxylase activity in testes following PRL-02 or AA dosing; inhibition appeared irreversible from PRL-02 and AA. Compared to VEH, a single IM dose of PRL-02 resulted in 81% and 75% reductions in plasma testosterone (T) on Days 7 and 14 post-dose, and an 80% reduction in testicular T on Day 14. Daily AA resulted in a 98% reduction in plasma T after 14 days. Conclusions: Single-dose IM PRL-02 blocked testicular CYP17 enzyme activity as effectively as daily AA in intact male rats and produced a durable large reduction in plasma T. The pharmacological activity, tissue and plasma distribution of TAE from IM PRL-02 in the rat model, along with results from prior monkey model studies, suggest the potential for a greater therapeutic index than from daily oral AA and support the ongoing evaluation of IM PRL-02 in patients with advanced prostate cancer.[Table: see text]

Defect evolution in tungsten exposed to helium plasma and deuterium plasmas studied by slow positron beam

• W samples have been exposed to He plasma and D plasmas. • DBS-PA technique has been used to characterize the defects in W. • Low energy plasma exposure could create defects in W. • D plasmas exposure could reduce the detectable defects in He plasma exposed W. Comparison of defect formation in tungsten samples exposed only to a helium plasma and those exposed to both helium plasma and subsequent deuterium plasmas is performed via Doppler broadening spectroscopy in the positron annihilation technique (DBS-PA). The S parameters of tungsten samples after helium plasma exposure increased with the increase of the incident fluence, which indicates that low energy helium plasma could induce the formation of defects such as nano-sized helium bubbles and dislocations in tungsten. The S parameters of samples exposed to helium incident fluence of 7.9 × 10 21 He/m 2 enhanced after deuterium plasmas exposure, indicating that low energy deuterium plasmas could form defects in tungsten too. Unexpectedly, deuterium plasmas exposure did not significantly influence the S parameters of the tungsten sample with helium incident fluence of 3.9 × 10 22 He/m 2 , and reduced the S parameters of the tungsten sample with helium incident fluence of 7.9 × 10 22 He/m 2 . These variations of S parameters could be associated with the occupation of nano-sized helium bubbles by deuterium atoms. This indicates possible competition between the increased density of vacancy-type defects by deuterium plasmas exposure and the filling of nano-sized helium bubbles by deuterium atoms, reducing detectability of these defects.

Influence of osmolality on gastrointestinal fluid volume and drug absorption: potential impact on oral salt supplementation

BackgroundThe syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is the most frequent cause of hyponatremia in patients with cerebrovascular disease, and is often treated with oral salt tablets. However, we have shown that osmolality-dependent variations in gastrointestinal (GI) fluid volume can alter the concentration of a poorly permeable drug in the GI tract, potentially affecting its absorption. Here, we examined the effect of ingestion of hyperosmotic solution (10% NaCl) on drug concentration and absorption in the GI tract.MethodsThe effects of osmolality on luminal fluid volume and drug absorption in rat intestine (jejunum, ileum and colon) were examined by means of an in situ closed loop method using fluorescein isothiocyanate-dextran 4000 (FD-4) and atenolol. In vivo absorption in rats was determined by measuring the plasma concentration after oral administration of the test compounds dissolved in purified water or hyperosmotic solution (10% NaCl).ResultsAdministration of hyperosmotic solution directly into the GI tract significantly increased the GI fluid volume, owing to secretion of water into the lumen. After administration in hyperosmotic solution, the luminal concentration of non-permeable FD-4 was significantly lower than the initial dosing concentration, whereas after administration in purified water, the luminal concentration exceeded the initial concentration. The fraction absorbed of atenolol was markedly lower after administration in hyperosmotic solution than after administration in purified water. An in vivo pharmacokinetic study in rats was consistent with these findings.ConclusionsAdministration of hyperosmotic NaCl solution increased GI fluid volume and reduced the plasma level of orally administered atenolol. This may imply that oral salt tablets used to treat hyponatremia in SIADH patients could decrease the intestinal absorption of concomitantly administered drugs, resulting in lower plasma exposure.

A Target-Mediated Drug Disposition Model to Explain Nonlinear Pharmacokinetics of the 11β-Hydroxysteroid Dehydrogenase Type 1 Inhibitor SPI-62 in Healthy Adults.

SPI‐62 is a selective and potent small‐molecule inhibitor of 11β‐hydroxysteroid dehydrogenase type 1 (HSD‐1). SPI‐62 has demonstrated substantial and complex nonlinear pharmacokinetics (PK) in humans that is characterized by unusually low plasma exposure at low doses, dose‐dependent volume of distribution, nonlinear PK following the first dose, and dose‐proportional PK at steady state, as well as unusually high accumulation ratios at low doses. The most likely explanation for the observed nonlinearity of SPI‐62 is the saturable binding of SPI‐62 to its pharmacological target HSD‐1, a phenomenon known as target‐mediated drug disposition (TMDD). Because of the nonlinear and complex PK of SPI‐62, the relationship among SPI‐62 dose, exposure, and response is no longer intuitive and consequently dose selection can be challenging. To facilitate dose selection and clinical trial design, in the current study population PK analysis was performed to characterize SPI‐62 dose‐exposure relationship in humans quantitatively. SPI‐62 PK was best characterized by a 2‐compartment TMDD model with 3 transit absorption compartments. The model was successfully established to explain the substantial and unusual nonlinear PK of SPI‐62 in humans, and it provided adequate fitting for both single‐ and multiple‐dose data. Our modeling work has provided a strong foundation for dose selection in future SPI‐62 clinical trials.

Removal of GaN film over AlGaN with inductively coupled BCl3/Ar atomic layer etch

Atomic layer etching (ALE) of thin film GaN (0001) is reported in detail using sequential surface modification by BCl3 adsorption and removal of the modified surface layer by low energy Ar plasma exposure in a reactive ion etching system. The estimated etching rate of GaN is ∼ 0.74 nm/cycle. The GaN is removed from the surface of AlGaN after 135 cycles. To study the mechanism of the etching, the detailed characterization and analyses are carried out, including scanning electron microscope (SEM), x-ray photoelectron spectroscopy (XPS), and atomic force microscope (AFM). It is found that in the presence of GaCl x after surface modification by BCl3, the GaCl x disappears after having exposed to low energy Ar plasma, which effectively exhibits the mechanism of atomic layer etch. This technique enables a uniform and reproducible fabrication process for enhancement-mode high electron mobility transistors with a p-GaN gate.

Synthesis and Enantioselective Pharmacokinetic/Pharmacodynamic Analysis of New CNS-Active Sulfamoylphenyl Carbamate Derivatives.

We recently reported a new class of carbamate derivatives as anticonvulsants. Among these, 3-methylpentyl(4-sulfamoylphenyl)carbamate (MSPC) stood out as the most potent compound with ED50 values of 13 mg/kg (i.p.) and 28 mg/kg (p.o.) in the rat maximal electroshock test (MES). 3-Methylpropyl(4-sulfamoylphenyl)carbamate (MBPC), reported and characterized here, is an MSPC analogous compound with two less aliphatic carbon atoms in its structure. As both MSPC and MBPC are chiral compounds, here, we studied the carbonic anhydrase inhibitory and anticonvulsant action of both MBPC enantiomers in comparison to those of MSPC as well as their pharmacokinetic properties. Racemic-MBPC and its enantiomers showed anticonvulsant activity in the rat maximal electroshock (MES) test with ED50 values in the range of 19–39 mg/kg. (R)-MBPC had a 65% higher clearance than its enantiomer and, consequently, a lower plasma exposure (AUC) than (S)-MSBC and racemic-MSBC. Nevertheless, (S)-MBPC had a slightly better brain permeability than (R)-MBPC with a brain-to-plasma (AUC) ratio of 1.32 (S-enantiomer), 1.49 (racemate), and 1.27 (R-enantiomer). This may contribute to its better anticonvulsant-ED50 value. The clearance of MBPC enantiomers was more enantioselective than the brain permeability and MES-ED50 values, suggesting that their anticonvulsant activity might be due to multiple mechanisms of action.

Low Doses of Psilocybin and Ketamine Enhance Motivation and Attention in Poor Performing Rats: Evidence for an Antidepressant Property.

Long term benefits following short-term administration of high psychedelic doses of serotonergic and dissociative hallucinogens, typified by psilocybin and ketamine respectively, support their potential as treatments for psychiatric conditions such as major depressive disorder. The high psychedelic doses induce perceptual experiences which are associated with therapeutic benefit. There have also been anecdotal reports of these drugs being used at what are colloquially referred to as “micro” doses to improve mood and cognitive function, although currently there are recognized limitations to their clinical and preclinical investigation. In the present studies we have defined a low dose and plasma exposure range in rats for both ketamine (0.3–3 mg/kg [10–73 ng/ml]) and psilocybin/psilocin (0.05–0.1 mg/kg [7–12 ng/ml]), based on studies which identified these as sub-threshold for the induction of behavioral stereotypies. Tests of efficacy were focused on depression-related endophenotypes of anhedonia, amotivation and cognitive dysfunction using low performing male Long Evans rats trained in two food motivated tasks: a progressive ratio (PR) and serial 5-choice (5-CSRT) task. Both acute doses of ketamine (1–3 mg/kg IP) and psilocybin (0.05–0.1 mg/kg SC) pretreatment increased break point for food (PR task), and improved attentional accuracy and a measure of impulsive action (5-CSRT task). In each case, effect size was modest and largely restricted to test subjects characterized as “low performing”. Furthermore, both drugs showed a similar pattern of effect across both tests. The present studies provide a framework for the future study of ketamine and psilocybin at low doses and plasma exposures, and help to establish the use of these lower concentrations of serotonergic and dissociative hallucinogens both as a valid scientific construct, and as having a therapeutic utility.

Recrystallization behaviour of high-flux hydrogen plasma exposed tungsten

Knowledge of a material’s thermal stability under extreme synergistic particle and heat loads is crucial for developing high performance reactor materials. In this work, the recrystallization behaviour of tungsten under the influence of hydrogen is investigated by low energy high flux hydrogen plasma exposure for various lengths of time. The microstructural changes following exposure are probed by micro-indentation, electron back-scatter diffraction measurements and the characteristic time for recrystallization is assessed using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) model. A recrystallization activation energy in the range of 425 to 440 kJ.mol-1 is determined, identical to that of oven annealed samples, thereby indicating an insignificant influence of hydrogen plasma on the recrystallization kinetics of tungsten.

Low Tenofovir Plasma Exposure in HIV Oral Pre-exposure Prophylaxis Recipients with Gastrointestinal Disorders.

Four pre-exposure prophylaxis (PrEP) users with gastro-intestinal disorders (sleeve gastrectomy, terminal ileitis, celiac disease or chronic diarrhea) and receiving oral tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) were included. Despite a self-reported high adherence, trough plasma tenofovir concentrations (after a supervised intake) were significantly lower than those observed in PrEP recipients without gastrointestinal disorders [21 (±9.1) vs. 138 (±85) ng/mL]. PrEP users with gastrointestinal disorders may need increased TDF doses or alternative prophylactic measures.

Effects of a monocarboxylate transport 1 inhibitor, AZD3965, on retinal and visual function in the rat.

Inhibition of monocarboxylate transport 1 (MCT1) is of interest in targeting highly glycolytic tumours. However, MCT1 is expressed in retina, and so inhibition of MCT1 could affect retinal function. AZD3965, an MCT1 inhibitor selected for clinical development, and two additional MCT1 inhibitors were evaluated for effects on visual acuity in albino (Han Wistar) rats. The effects of AZD3965 on visual acuity and electroretinography (ERG) were further investigated in pigmented (Long-Evans) rats, with dosing for up to 7 days. All three MCT1 inhibitors reduced visual acuity within 2 h of dosing, suggesting a class effect. The deficit caused by AZD3965 (1,000 mg·kg-1 p.o. per day for 4 days) in Long Evans rats recovered to pre-dose levels 7 days after cessation of dosing. AZD3965 (50 to 1,000 mg·kg-1 p.o.) reduced the amplitude of scotopic a- and b-waves, and photopic b-wave of the ERG in a dose-related fashion, within 2 h of dosing. The effects on the scotopic ERG had diminished by Day 7 of dosing, demonstrating partial restoration of function despite continued treatment. Seven days after cessation of dosing at the highest dose tested (1,000 mg·kg-1 ), there was recovery of both scotopic a- and b- waves and, to a lesser extent, photopic b-wave. ERG was affected at lower plasma exposures than was visual function. This study clarifies the role of the MCT1 transporter in retinal function. The monitorability of the functional effects on the retina enabled safe clinical use of AZD3965.

Further Analytical, Pharmacokinetic, and Clinical Observations on Low-Dose Ponatinib in Patients with Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia

Introduction: Ponatinib (PNT) is a tyrosine kinase inhibitor approved for treating patients with Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph + ALL), or chronic myeloid leukemia, resistant or intolerant to other tyrosine kinase inhibitor or showing T315I mutation of BCR-ABL. Unfortunately, the clinical use of PNT is limited by the possible occurrence of vascular occlusive events. The incidence of vascular events seems to correlate with PNT dose intensity and plasma exposure. Dose reductions from 45 mg to 30 or 15 mg/day are increasingly considered to improve PNT safety but a plasma threshold of ∼40 nM must be achieved to ensure that antileukemic activity is preserved. Therapeutic drug monitoring (TDM) would be appropriate for patients treated by PNT. We, therefore, developed and validated a liquid chromatography tandem mass spectrometry (HPLC-MS/MS) assay to measure PNT plasma levels. Methods: PNT and its deuterated internal standard were extracted from human plasma by one-step protein precipitation. PNT was separated and quantified by HPLC-MS/MS operating in the multiple reaction monitoring acquisition mode. Results: The method was linear from 9.4 to 940 nM PNT. Limits of detection and lower limits of quantification (LLOQ) were, respectively, 1 and 9.4 nM. Selectivity, sensitivity, matrix effect, short-, and long-term stability met criteria of international guidelines for bioanalytical method validation. Intra- and inter-day accuracy and precision were calculated on 4 different concentrations (QCLow, QCMedium, QCHigh, and LLOQ), with all values being <15%. The method was successfully probed in leukemia Ph + ALL patients to show that PNT doses <45 mg/day caused lower plasma exposure but still achieved PNT levels at or above the 40 nM threshold. Conclusions: We developed a highly sensitive and selective HPLC-MS/MS method to quantify PNT in human plasma. This method might be used for TDM and to guide dose reductions if unnecessary high PNT levels are detected in a patient.

Clofazimine pharmacokinetics in patients with TB: dosing implications.

BackgroundClofazimine is in widespread use as a key component of drug-resistant TB regimens, but the recommended dose is not evidence based. Pharmacokinetic data from relevant patient populations are needed to inform dose optimization.ObjectivesTo determine clofazimine exposure, evaluate covariate effects on variability, and simulate exposures for different dosing strategies in South African TB patients.Patients and methodsClinical and pharmacokinetic data were obtained from participants with pulmonary TB enrolled in two studies with intensive and sparse sampling for up to 6 months. Plasma concentrations were measured by LC-MS/MS and interpreted with non-linear mixed-effects modelling. Body size descriptors and other potential covariates were tested on pharmacokinetic parameters. We simulated different dosing regimens to safely shorten time to average daily concentration above a putative target concentration of 0.25 mg/L.ResultsWe analysed 1570 clofazimine concentrations from 139 participants; 79 (57%) had drug-resistant TB and 54 (39%) were HIV infected. Clofazimine pharmacokinetics were well characterized by a three-compartment model. Clearance was 11.5 L/h and peripheral volume 10 500 L for a typical participant. Lower plasma exposures were observed in women during the first few months of treatment, explained by higher body fat fraction. Model-based simulations estimated that a loading dose of 200 mg daily for 2 weeks would achieve average daily concentrations above a target efficacy concentration 37 days earlier in a typical TB participant.ConclusionsClofazimine was widely distributed with a long elimination half-life. Disposition was strongly influenced by body fat content, with potential dosing implications for women with TB.

Impact of Plasma Exposure of Statins and Their Metabolites With Major Adverse Cardiovascular Events in Chinese Patients With Coronary Artery Disease.

The selection of optimum statin intensity is inconclusive, and the association of plasma exposure of statins and metabolites with major adverse cardiovascular events (MACEs) is unclear. This study sought to compare the effect of low (quartile 1), intermediate (quartiles 2 and 3), and high (quartile 4) plasma exposure of statins and metabolites on MACE, re-ischemia events and death in patients with coronary artery disease (CAD) at 5 years. A total of 1,644 patients in atorvastatin (AT) cohort and 804 patients in rosuvastatin (RST) cohort were included, and their plasma concentration of statins and metabolites was categorized as low-, mid-, or high-group. The association between the plasma levels of statins and metabolites and the incidence of primary endpoint in patients was assessed by Cox proportional hazard models. Intensive AT exposure (Q4 > 5.32 ng/ml) was significantly associated with increased risk of death compared with low (hazard ratio [HR]: 1.522; 95% confidence interval [CI]: 1.035–1.061; P = 0.0022) or moderate exposure (HR: 2.054; 95% CI: 1.348–3.130; P = 0.0008). This association was also found in AT’s five metabolites (all P < 0.01). In patients with RST treatment, moderate RST concentration (0.53–4.29 ng/ml) versus low concentration had a significantly lower risk of MACE and re-ischemia events. (HR: 0.532, 95% CI: 0.347–0.815, P = 0.0061 and HR: 0.505, 95% CI: 0.310–0.823, P = 0.0061, respectively). A higher plasma exposure of AT and metabolites has a significantly higher risk of death, and moderate RST exposure has a significantly lower risk of MACE and re-ischemia events in Chinese patients with CAD. The harms of high plasma exposure should be considered when prescribing statins to patients because it may be a risk factor for having poor prognosis in patients with CAD.

Inhibition of vascular calcification by inositol phosphates derivatized with ethylene glycol oligomers

Myo-inositol hexakisphosphate (IP6) is a natural product known to inhibit vascular calcification (VC), but with limited potency and low plasma exposure following bolus administration. Here we report the design of a series of inositol phosphate analogs as crystallization inhibitors, among which 4,6-di-O-(methoxy-diethyleneglycol)-myo-inositol-1,2,3,5-tetrakis(phosphate), (OEG2)2-IP4, displays increased in vitro activity, as well as more favorable pharmacokinetic and safety profiles than IP6 after subcutaneous injection. (OEG2)2-IP4 potently stabilizes calciprotein particle (CPP) growth, consistently demonstrates low micromolar activity in different in vitro models of VC (i.e., human serum, primary cell cultures, and tissue explants), and largely abolishes the development of VC in rodent models, while not causing toxicity related to serum calcium chelation. The data suggest a mechanism of action independent of the etiology of VC, whereby (OEG2)2-IP4 disrupts the nucleation and growth of pathological calcification.