Plasma Cmax Research Articles

Pharmacokinetics/Pharmacodynamics of Caspofungin in Plasma and Peritoneal Fluid of Liver Transplant Recipients.

The weaker diffusion of echinocandins in the peritoneal fluid (PF) could promote Candida-resistant isolates. The aim of this study was to analyze the pharmacokinetics (PK)/pharmacodynamics (PD) of caspofungin in plasma and PF samples from liver transplant recipients. Liver transplant patients received caspofungin as postoperative prophylaxis. Caspofungin concentrations were quantified in plasma and PF samples on days 1, 3, and 8. Data were analyzed using nonlinear mixed-effect modeling and Monte Carlo simulations. Area under the curve (AUC) values for plasma and PF were simulated under three dosing regimens. Probabilities of target attainment (PTAs) were calculated using area under the unbound plasma concentration-time curve from 0 to 24 h at steady state (fAUC0-24)/MIC ratios, with MICs ranging from 0.008 to 8 mg/L. All of the patients included were monitored weekly for Candida colonization and for Candida infections. Twenty patients were included. The median daily dose of caspofungin was 0.81 mg/kg. Plasma (n = 395) and PF (n = 50) concentrations at steady state were available. A two-compartment model with first-order absorption and elimination was described. Our two-compartment model with first-order absorption and elimination produced an effective PK/PD relationship in plasma, achieving a PTA of ≥90% with MICs ranging from 0.008 to 0.12 mg/L for Candida albicans and Candida glabrata. In PF, PTAs at D8 were optimal only for a MIC of 0.008 mg/L in patients weighing 60 kg under the three dosing regimens. Among the 16 patients colonized, all MIC values were below the maximal concentration (Cmax) in plasma but not in PF. PF concentrations of caspofungin were low. Simulations showed that the PTAs for Candida spp. in PF were not optimal, which might suggest a potential risk of resistance.

A Drug-Drug Interaction Study to Investigate the Effect of Nintedanib on the Pharmacokinetics of Microgynon (Ethinylestradiol and Levonorgestrel) in Female Patients with Systemic Sclerosis-Associated Interstitial Lung Disease.

Background and ObjectivesNintedanib is a tyrosine kinase inhibitor approved for the treatment of systemic sclerosis-associated interstitial lung disease (SSc-ILD), idiopathic pulmonary fibrosis, and other chronic fibrosing ILDs with a progressive phenotype. As nintedanib may cause foetal harm, patients taking nintedanib should avoid pregnancy. The objective of this study was to investigate the effect of nintedanib co-administration on the pharmacokinetics of Microgynon (ethinylestradiol and levonorgestrel) in female patients with SSc-ILD.MethodsThis was an open-label, two-period, fixed-sequence, drug–drug interaction study. Female patients with SSc and ≥ 10% extent of fibrotic ILD on a high-resolution computed tomography scan were eligible to participate. In Period 1, patients received one Microgynon tablet (ethinylestradiol 30 μg and levonorgestrel 150 μg) ≥ 3 days before the first administration of nintedanib in Period 2. In Period 2, patients received one Microgynon tablet following intake of nintedanib 150 mg twice daily for ≥ 10 consecutive days. The primary pharmacokinetic endpoints were the areas under the plasma concentration–time curve of ethinylestradiol and levonorgestrel over the time interval from 0 to the last quantifiable data point (AUC0–tz) and the maximum measured concentrations of ethinylestradiol and levonorgestrel in plasma (Cmax). The secondary pharmacokinetic endpoint was the area under the plasma concentration–time curve of ethinylestradiol and levonorgestrel over the time interval from 0 extrapolated to infinity (AUC0–∞). The relative exposures of ethinylestradiol and levonorgestrel when administered alone and in combination with nintedanib were assessed using an ANOVA model.ResultsSeventeen patients were treated. Pharmacokinetic data from 15 patients were analysed. Plasma concentration–time profiles of ethinylestradiol and levonorgestrel were similar following administration of Microgynon before and after administration of nintedanib for ≥ 10 consecutive days. Adjusted geometric mean (gMean) ratios [90% confidence intervals (CIs)] for AUC0‒tz (101.4% [92.8, 110.7]) and AUC0‒∞ (101.2% [94.0, 109.1]) indicated that there was no difference in total ethinylestradiol exposure when Microgynon was administered before or after administration of nintedanib. The adjusted gMean ratio for Cmax of ethinylestradiol (116.7% [90% CI 107.6, 126.5]) indicated an increase in peak exposure in the presence of nintedanib. Adjusted gMean ratios [90% CIs] for AUC0-tz (96.4% [91.5, 101.6]) and Cmax (100.9% [89.9, 113.2]) indicated that there was no difference in total or peak levonorgestrel exposure when Microgynon was administered before or after administration of nintedanib. The adjusted gMean ratio for AUC0‒∞ of levonorgestrel indicated a decrease in total exposure in the presence of nintedanib (88.1% [90% CI 80.0, 97.0]).ConclusionPharmacokinetic data indicate that there is no relevant effect of nintedanib on plasma exposure to ethinylestradiol and levonorgestrel in female patients with SSc-ILD.Trial RegistrationClinicaltrials.gov NCT03675581.

A new phenothiazine derivate is active against Clostridioides difficile and shows low cytotoxicity.

The rapid evolution of antibiotic resistance in Clostridioides difficile and the consequent effects on prevention and treatment of C. difficile infections (CDIs) are matters of concern for public health. Thioridazine, a compound belonging to the phenothiazine group, has previous shown antimicrobial activity against C. difficile. The purpose of this present study was to investigate the potential of a novel phenothiazine derivative, JBC 1847, as an oral antimicrobial for treatment of intestinal pathogens and CDIs. The minimal inhibition concentration and the minimum bactericidal concentration of JBC 1847 against C. difficile ATCC 43255 were determined 4 μg/mL and high tolerance after oral administration in mice was observed (up to 100 mg/kg bodyweight). Pharmacokinetic modeling was conducted in silico using GastroPlusTM, predicting low (< 10%) systemic uptake after oral exposure and corresponding low Cmax in plasma. Impact on the intestinal bacterial composition after four days of treatment was determined by 16s rRNA MiSeq sequencing and revealed only minor impact on the microbiota in non-clinically affected mice, and there was no difference between colony-forming unit (CFU)/gram fecal material between JBC 1847 and placebo treated mice. The cytotoxicity of the compound was assessed in Caco-2 cell-line assays, in which indication of toxicity was not observed in concentrations up to seven times the minimal bactericidal concentration. In conclusion, the novel phenothiazine derivative demonstrated high antimicrobial activity against C. difficile, had low predicted gastrointestinal absorption, low intestinal (in vitro) cytotoxicity, and only induced minor changes of the healthy microbiota, altogether supporting that JBC 1847 could represent a novel antimicrobial candidate. The clinical importance hereof calls for future experimental studies in CDI models.

Pharmacokinetics of tulathromycin on plasma and semen of beef bulls

The objective of this investigation was to evaluate the pharmacokinetic parameters of tulathromycin in plasma and semen of beef bulls after administering a single sc dose at two different sites in the neck. Four Simmental bulls with excellent temperament received a comprehensive physical exam that included breeding soundness examination. In addition, blood was collected and analyzed for CBC and chemical panel in order to rule out any subclinical liver or kidney disease. All bulls were diagnosed as healthy and satisfactory potential breeders. The mean plasma levels of tulathromycin for the two neck sites of sc administration were not different between posterior aspect of the ear where it attaches to the head (RP; regio parotidea; 77.9 ± 43.3 ng/mL; X ± SD) and to the middle of the neck (RC; regio collis lateralis; 73.7 ± 39.7 ng/mL; P = 0.84). The mean seminal plasma levels of tulathromycin after administration in the RP was 608 ± 374 ng/mL and for RC was 867 ± 599 ng/mL without differences between both sites (P = 0.29). The mean level of tulathromycin in plasma was 75.8 ± 40.2 ng/mL, which was lower than mean seminal plasma levels of 781 ± 482 ng/mL (P = 0.001). The plasma peak tulathromycin concentration (Cmax) was 160 ± 27 ng/mL at 21 ± 6 h (Tmax) post-administration. The seminal plasma Cmax was 1539 ± 44.4 ng/mL at 33.00 ± 18.00 h (Tmax) post-administration. The Cmax between plasma and seminal plasma were different (P = 0.008) without any differences in Tmax between plasma and seminal plasma (P = 0.35). The terminal half-life for plasma tulathromycin (81.4 ± 27.6 h) showed a tendency to be shorter than in seminal plasma (114.7 ± 21.7; P = 0.10). The plasma area under the curve concentration time from the first to the last sample (AUC0–last) was 15,440 ± 1717 ng/mL/h, which was significatively smaller compared with 171,071 ± 58,556 ng/mL/h for seminal plasma AUC0–last (P = 0.01). The plasma means residence time from the first to the last sample (MRT0-last) was 89.3 ± 5.1 h and it was shorter than for seminal plasma of 96.6 ± 5.0 h (P = 0.05). From the present investigation, it was concluded that tulathromycin is a suitable antibiotic based in its pharmacokinetic properties that could be used for treatment of bull genital infections when its application is indicated.

Pre-Clinical Pharmacokinetic Characterization, Tissue Distribution, and Excretion Studies of Novel Edaravone Oral Prodrug, TEJ-1704.

Edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one) is a free radical scavenger approved for the treatment of amyotrophic lateral sclerosis, a fatal neuromuscular disease. Edaravone is administered as an intravenous infusion over 60 min for several treatment cycles. To ease the burden of patients and caregivers, the oral formulation of edaravone has been developed. The purpose of this study was to evaluate pharmacokinetics and tissue distribution of TEJ-1704, an edaravone oral prodrug, in male Sprague Dawley rats and beagle dogs. Animal experiments were conducted using Sprague Dawley rats and beagle dogs to evaluate pharmacokinetics, tissue distribution, and excretion of TEJ-1704. Blood, tissues, cerebrospinal fluid, urine, and feces samples were collected at designated sampling time after intravenous (IV) or oral (PO) administration of edaravone or TEJ-1704. A modified bioanalysis method was developed to quantify edaravone in samples including plasma, tissues, cerebrospinal fluid, urine, and feces. The bioanalysis method was validated and successfully applied to pharmacokinetics, tissue distribution, and excretion studies of the novel edaravone prodrug. Although plasma Cmax of TEJ-1704 was low, groups administered with TEJ-1704 had high AUCinf, suggesting continuous metabolism of TEJ-1704 into edaravone. Groups treated with TEJ-1704 also showed lower CSF distribution than the control groups. After the administration of TEJ-1704, the majority of edaravone was distributed to the heart, lung, and kidney. It was excreted equally via urine and feces. The pharmacokinetics, tissue distribution, and excretion of TEJ-1704, a novel edaravone oral prodrug, were successfully characterized. Additional studies are needed to fully understand the difference between TEJ-1704 and edaravone and determine the potency of TEJ-1704.

A Phase I, Open-label, Randomized, 2-Way Crossover Study to Evaluate the Relative Bioavailability of Intranasal and Oral Varenicline

PurposeTo estimate the systemic bioavailability of OC-01 (varenicline) nasal spray, an investigational treatment for dry eye disease, relative to oral varenicline approved for smoking cessation. MethodsThe Study to Evaluate the Relative Bioavailability of Varenicline Administered as OC-01 (Varenicline) Nasal Spray as Compared to Varenicline Administered Orally as Chantix (ZEN study) was a Phase I, open-label, randomized, single-center, 2-way crossover study. On day 1, 22 healthy participants were randomized 1:1 to a single intranasal dose of varenicline 0.12 mg in OC-01 nasal spray or a single oral dose of varenicline 1 mg. On day 15, all participants crossed over to receive a single dose of the alternate treatment. Plasma samples were collected for 6 days after each dose, and pharmacokinetic parameters were estimated using noncompartmental analysis. Tolerability was monitored throughout. FindingsAfter a single dose of intranasal varenicline 0.12 mg in OC-01 nasal spray, peak systemic exposure (mean plasma Cmax) was 0.34 ng/mL, which occurred at a median Tmax of 2.0 hours. In comparison, mean plasma Cmax after oral varenicline 1 mg was 4.63 ng/mL at a median Tmax of 3.0 hours. On the basis of geometric mean ratio point estimates, peak exposure (Cmax) and total exposure (AUC0–∞) after intranasal varenicline 0.12 mg were 7.0% and 7.5%, respectively, of the systemic exposure associated with oral varenicline 1 mg. Dose-normalized Cmax and AUC0–∞ for intranasal varenicline remained 39% and 33% lower versus oral varenicline, respectively. No new or unexpected tolerability signals were detected. ImplicationsAt its highest intended single dose in OC-01 nasal spray, intranasal varenicline delivered less drug to the systemic circulation than oral varenicline at its highest approved single dose. ClinicalTrials.gov identifier: NCT04072146.

Strictly regulated agonist-dependent activation of AMPA-R is the key characteristic of TAK-653 for robust synaptic responses and cognitive improvement

Agonistic profiles of AMPA receptor (AMPA-R) potentiators may be associated with seizure risk and bell-shaped dose-response effects. Here, we report the pharmacological characteristics of a novel AMPA-R potentiator, TAK-653, which exhibits minimal agonistic properties. TAK-653 bound to the ligand binding domain of recombinant AMPA-R in a glutamate-dependent manner. TAK-653 strictly potentiated a glutamate-induced Ca2+ influx in hGluA1i-expressing CHO cells through structural interference at Ser743 in GluA1. In primary neurons, TAK-653 augmented AMPA-induced Ca2+ influx and AMPA-elicited currents via physiological AMPA-R with little agonistic effects. Interestingly, TAK-653 enhanced electrically evoked AMPA-R-mediated EPSPs more potently than AMPA (agonist) or LY451646 (AMPA-R potentiator with a prominent agonistic effect) in brain slices. Moreover, TAK-653 improved cognition for both working memory and recognition memory, while LY451646 did so only for recognition memory, and AMPA did not improve either. These data suggest that the facilitation of phasic AMPA-R activation by physiologically-released glutamate is the key to enhancing synaptic and cognitive functions, and nonselective activation of resting AMPA-Rs may negatively affect this process. Importantly, TAK-653 had a wide safety margin against convulsion; TAK-653 showed a 419-fold (plasma Cmax) and 1017-fold (AUC plasma) margin in rats. These findings provide insight into a therapeutically important aspect of AMPA-R potentiation.

Comparative pharmacokinetics of levofloxacin in the saliva and blood plasma of patients with pneumonia

BACKGROUND: Levofloxacin concentrations do not always reach desired levels when administered at a standard dose; therefore, measuring levofloxacin levels in the blood plasma or other alternative matrices, such as the saliva, can help clinicians make informed decisions concerning the dosage and mode of administration. Saliva, as an object of research, is of particular interest due to the simplicity and non-invasiveness of sampling for analysis.&#x0D; AIM: This study aimed to determine the comparative pharmacokinetics of levofloxacin in the blood plasma and saliva of patients with community-acquired pneumonia (CAP) and assess the possibility of using saliva as an alternative sampling matrix in pharmacokinetic studies.&#x0D; MATERIALS AND METHODS: Levofloxacin concentration in the blood plasma and saliva of patients with CAP and volunteers was determined using high-performance liquid chromatography on an Agilent 1200 liquid chromatography (Agilent, USA) with an ultraviolet detector. Sample preparation of bioassays was performed using protein precipitation. Patients and volunteers took 1 tablet (500 mg dose) of levofloxacin per os in the morning, on an empty stomach. Blood and saliva samples were taken at the initial blood sample and 0.5, 1, 1.5, 2, 3, 4, 6, 8, 10, and 24 h after taking the drug. The pharmacokinetic parameters were determined, namely Cmax as the peak concentration of the drug; Тmax as the time-to-peak concentration; AUC0t as the area under the pharmacokinetic curve in the range from 0 to the last experimental point on the curve; AUC0 as the total area under the pharmacokinetic curve from zero to infinity; t1/2 as half-life period; MRT as mean residence time of the drug in the blood (h); Cl/F as clearance; and Vss/F as the total distribution volume.&#x0D; RESULTS: The maximum blood plasma and saliva concentration of patients was reached 1 h after taking the drug and amounted to Сmax=5.982.89 g/ml and Сmax=4.413.83 g/ml, respectively. Additionally, the maximum concentrations in blood plasma and saliva were recorded 1 h after taking the drug as 5.523.07 g/ml and 3.250.85 g/ml, respectively, in healthy volunteers. The correlation coefficient (r) between the mean values of the levofloxacin concentrations in the blood plasma and the saliva of patients with CAP was 0.953 and that of healthy volunteers was 0.977.&#x0D; DISCUSSION: Pharmacokinetic parameters were calculated based on blood plasma and saliva concentrations. Their comparative analysis revealed almost the same absorption rate from the gastrointestinal tract in patients and healthy volunteers. Correlation-regression analysis revealed a high correlation between the average values of Cmax in saliva and plasma both in the patient (r=0.96) and healthy volunteer group (r=0.98).&#x0D; CONCLUSIONS: With statistically significant differences in the areas under pharmacokinetic curves in blood plasma and saliva, the remaining pharmacokinetic parameters of saliva and blood plasma did not significantly differ between patients with CAP and healthy volunteers. A significant direct correlation was revealed between the mean concentration and pharmacokinetic parameters in saliva and blood plasma in both groups. The study demonstrated the possibility of using saliva as a biomaterial in the study of levofloxacin pharmacokinetics.

Pharmacokinetics and Safety of a Single Dose and Multiple Doses of Allisartan Isoproxil, an Angiotensin II Receptor Blocker, in Healthy Chinese People.

Allisartan isoproxil (AI) is a blocker of the angiotensin II type 1 receptor. We evaluated the safety and pharmacokinetics of single- and multiple-dose AI in healthy Chinese individuals. Participants were assigned to receive AI or placebo. Plasma concentration of EXP3174 (carboxylic acid derivative) was measured using liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were determined by noncompartmental methods. Twelve subjects were enrolled, and the ratio of men to women was 5:1. Main pharmacokinetic parameters of EXP3174 after single and multiple doses of AI were a mean maximum concentration in plasma (Cmax ) of 2242 ± 1037 ng/mL and median time to reach Cmax (Tmax ) of 3.5 hours (2.5-8 hours). The median Tmax, at steady state was 4.0 hours (1.5-8 hours). The mean Cmax at steady state (Cmax, SS ) was 2047 ± 1050 ng/mL. In terms of EXP3174, there was no significant difference in the Cmax, SS , area under the curve from time zero to 24 hours of quantifiable concentration at steady state (AUC0-24 SS ), and AUC0-72 after multiple doses of AI. Serious adverse events did not occur. These data suggest that AI is safe and well tolerated in healthy Chinese individuals at a single dose of 480 or 480 mg once daily for 7 days.

Carrier-free resveratrol nanoparticles: Formulation development, In-vitro anticancer activity, and oral bioavailability evaluation

Resveratrol nanoparticles (RNP) formulation was prepared with 0.5% w/v of SDS and confirmed by TEM, XRD, DSC, XRD, FTIR and NMR. The prepared RNP were evaluated for physicochemical properties like solubility, stability, dissolution profile and partition coefficient. The anticancer activity of prepared RNP formulation was determined against HCT 116 human colorectal cancer cells by cell viability and apoptosis studies. An in vivo pharmacokinetic study in SD rats showed that, the AUC of the RNP was significantly higher (p < 0.0001) than the pure RSV. The plasma Cmax was found to be 0.23 ± 0.02 μg/mL for RSV and 0.62 ± 0.09 μg/mL for RNP. An increase in AUC and Cmax suggested that, the developed formulation was more bioavailable than the pure RSV.

Pharmacokinetics and Pharmacodynamics of Ionis-FXIRx, an Antisense Inhibitor of Factor XI, in Patients with End-Stage Renal Disease on Hemodialysis

BACKGROUNDPatients with end-stage renal disease (ESRD) on hemodialysis are at high risk of both thrombotic and bleeding events. Experimental and clinical data indicate that reducing factor XI (FXI), a key component of the intrinsic pathway, prevents thrombosis without causing bleeding. FXI activity can be lowered with IONIS-FXIRx, a 2nd generation antisense oligonucleotide that specifically reduces human FXI mRNA expression in the liver. This study sought to determine the safety, pharmacokinetics (PK) and pharmacodynamics (PD) of IONIS-FXIRx in participants with ESRD. METHODSIn this Phase 2 multicenter study, we enrolled a total of 49 ESRD patients: (A) 6 participants receiving chronic in-center hemodialysis (HD) to receive an open-label single-dose of 300 mg IONIS-FXIRx either 5 minutes before or 10 minutes after HD and assessed the effects of HD on peak (Cmax) and the extent of exposure (AUC0-24hr) parameters of IONIS-FXIRx and (B) another 43 participants in a double-blind design to one of two multiple-dose regimens (200 mg or 300 mg) IONIS-FXIRx or placebo for 12 weeks with 12 weeks of additional follow up. In the double-blind portion, IONIS-FXIRx was administered subcutaneously ~10 minutes after HD. For PK, plasma trough concentration and apparent elimination half-life (t1/2λz) were evaluated. The PD parameters including FXI activity and antigen, aPTT, prothrombin time (PT), and INR were evaluated in the per-protocol population (N= 34) that was defined as all participants who received the complete protocol-specified administration of IONIS-FXIRx or placebo through week 8 and who did not have any major protocol violations. The rate and frequency of clotting on the HD filters and circuit were qualitatively measured with a clotting scale as an exploratory PD analysis. RESULTSThe PK cohort included 6 males (5 white) with a mean age of 61 years. The plasma PK profile of IONIS-FXIRx was not significantly altered whether injected before or after HD. After multiple dosing, plasma Cmax values were dose-dependent and similar between Day 1 (first dose) and Day 78 (last dose), suggesting no accumulation of IONIS-FXIRx in ESRD participants after 12-weeks of dosing. After treatment cessation, IONIS-FXIRx had an apparent elimination half-life of approximately 2 weeks. In the double-blind portion of the study, 22 (51.2%) of the participants were male, 24 (55.8%) were white and the mean age was 59 years. Attenuation of FXI activity was associated with a reduction in the incidence of severe clotting events on both the air filter and dialyzer (Table). The reduction in severe clotting events was observed when FXI activity was < 0.4 U/mL. Consistent with prior observations in healthy subjects, IONIS-FXIRx prolonged aPTT in a time and dose-dependent manner with maximum mean percent changes from baseline of 53.3% (p < 0.05) for the 200 mg dose group and 75.6% (p < 0.05) for the 300 mg dose group at Week 14, but had no effect on PT. Treatment emergent adverse events (TEAEs) were mostly mild; participants reporting serious TEAEs were 1 (16.7%) for the PK cohort, 4 (30.8%) for placebo and 3 (20.0%) each for the 200 mg and 300 mg IONIS-FXIRx dose groups. There were no drug-related SAEs and no drug-related major or clinically-relevant non-major bleeding events. Minor bleeds were primarily observed in the 300 mg multiple-dose group at AV fistula/graft sites but did not correlate with reduction of FXI activity. No clinically significant reductions in platelet counts were reported during the study. CONCLUSIONSThis study demonstrated that (i) HD had no effect on IONIS-FXIRx PK, (ii) IONIS-FXIRx was well tolerated and produced sustained, and dose-dependent reductions in FXI antigen and activity, and (iii) IONIS-FXIRx reduced severe dialysis circuit clotting events beyond standard heparin use. Collectively, these data support further evaluation of IONIS-FXIRx as a potentially safe, effective antithrombotic therapy in ESRD patients on HD. [Display omitted] DisclosuresBethune:Ionis Pharmaceuticals: Employment. Walsh:Population Health Research Institute: Employment; Ionis Pharmaceuticals: Consultancy. Jung:Ionis Pharmaceuticals: Employment. Yu:Ionis Pharmaceuticals: Employment. Geary:Ionis Pharmaceuticals: Employment. Bhanot:Ionis Pharmaceuticals: Employment.

Changes in the Pharmacokinetics and Pharmacodynamics of Sildenafil in Cigarette and Cannabis Smokers.

Sildenafil citrate, a widely-used oral therapy for erectile dysfunction, is a cytochrome P3A4 (CYP3A4) enzyme substrate. Studies have reported that this substrate has an inhibitory effect on CYP3A4 enzymes in long-term cigarette and cannabis smokers, which predominantly mediate the hepatic elimination of sildenafil. Cigarette and/or cannabis smoking could therefore alter the exposure of sildenafil. The aim of this study was to examine the effect of smoking cigarettes and/or cannabis on the pharmacokinetics, pharmacodynamics, safety and tolerability of sildenafil. Thirty-six healthy human subjects were equally divided into three groups: non-smokers, cigarette smokers and cannabis smokers. Each group was administered a single dose of sildenafil (50 mg tablets). The primary outcome measures included the maximum concentration of sildenafil in plasma (Cmax), the elimination half-life (t1/2) and the area under the plasma concentration time curve from zero to time (AUC0–t). The pharmacodynamics were assessed by the International Index of Erectile Function (IIEF-5). The exposure of sildenafil (AUC0–t) showed a statistically significant increase in cigarette smokers (1156 ± 542 ng·h/mL) of 61% (p < 0.05) while in cannabis smokers (967 ± 262 ng·h/mL), a non-significant increase in AUC0–t of 35% (p > 0.05) was observed relative to non-smokers (717 ± 311 ng·h/mL). Moreover, the Cmax of sildenafil increased by 63% (p < 0.05) and 22% (p > 0.05) in cigarette smokers and cannabis smokers, respectively. Cigarette smoking increases the exposure of sildenafil to a statistically significant level with no effect on its pharmacodynamics, safety and tolerability.

SBP-101, a polyamine metabolic inhibitor, administered in combination with gemcitabine and nab-paclitaxel, shows signals of efficacy as first-line treatment for subjects with metastatic pancreatic ductal adenocarcinoma.

4127 Background: SBP-101, a polyamine metabolic inhibitor, inhibited growth in 6 human pancreatic ductal adenocarcinoma (PDA) cell lines and 3 murine xenograft tumor models of human PDA. SBP-101 monotherapy in heavily pre-treated PDA patients (&gt; 2 prior regimens) showed a median survival of 5.9 months at the optimal dose level. Purpose: To assess the PK, safety and efficacy of SBP-101 in combination with gemcitabine (G) and nab-paclitaxel (A) in patients with previously untreated metastatic PDA. Methods: In a modified 3+3 dose escalation scheme, subcutaneous injections of SBP-101 were dosed at 0.2, 0.4 or 0.6 mg/kg days 1-5 of each 28-day cycle. G (1000 mg/m2) and A (125 mg/m2) were administered intravenously on Days 1, 8, and 15 of each cycle. PK was evaluated on day 1 of cycle 1 in cohorts 1-3. Safety was evaluated by clinical and laboratory assessments. Efficacy was assessed by CA19-9 levels, objective response using RECIST criteria, progression-free survival (PFS) and overall survival (OS). A fourth cohort using a modified dosing schedule of 0.4 mg/kg SBP-101 days 1-5 for cycles 1-2 and days 1, 8, and 15 every cycle thereafter was added to mitigate hepatic toxicity, and that dose and schedule were recommended for phase 1b expansion. Interim Results: Fifty patients were enrolled (N=25, phase 1a and N=25, phase 1b) and have received up to 12 treatment cycles. SBP-101 plasma Cmax and AUC0-t increased in a slightly more than dose proportional manner and were unchanged by the addition of G and A. PK parameters of G and A were unaltered by increasing doses of SBP-101. The most common nonserious adverse events related to SBP-101 (&gt;10%) are fatigue (N=15), LFT/transaminase abnormalities (N=15), vision abnormalities (N=6), injection site pain (N=13), dehydration (N=7), diarrhea (N=7) and nausea (N=6). Serious adverse events related to SBP-101 observed in some subjects include hepatic toxicity (N= 6) and retinal toxicity (N=6) both occurring after prolonged treatment and requiring dose reduction or discontinuation. There is no evidence of SBP-101-related bone marrow suppression or peripheral neuropathy. At the recommended dose and schedule (N=30), CA19-9 levels decreased 60-99% in 19 of 29 evaluable patients, with 12/28 evaluable patients achieving partial responses (43%) and 11/28 achieving stable disease at 8 weeks (39%). Nine subjects are ongoing. PFS was confounded by SBP-101 dosing holds implemented to investigate potential toxicity. Median OS has not been reached. Conclusions: Interim results suggest SBP-101 may enhance first-line treatment with G and A in patients with metastatic PDA. Hepatic toxicity can be mitigated with dose reduction or discontinuation. Retinal toxicity that occurred in some subjects is under investigation. Clinical trial information: NCT03412799.

Development of Mucoadhesive Buccal Film for Rizatriptan: In Vitro and In Vivo Evaluation.

The reduced therapeutic efficacy of rizatriptan in migraine treatment is primarily due to low oral bioavailability and extensive first pass metabolism. The purpose of this investigation was to optimize the thin mucoadhesive buccal film of rizatriptan and assess the practicability of its development as a potential substitute for conventional migraine treatment. Buccal films (FR1–FR10) were fabricated by a conventional solvent casting method utilizing a combination of polymers (Proloc, hydroxypropyl methylcellulose and Eudragit RS 100). Drug-loaded buccal films (F1–F4) were examined for mechanical, mucoadhesive, swelling and release characteristics. In vivo pharmacokinetics parameters of selected buccal film (F1) in rabbits were compared to oral administration. Films F1–F4 displayed optimal physicomechanical properties including mucoadhesive strength, which can prolong the buccal residence time. A biphasic, complete and higher drug release was seen in films F1 and F4, which followed Weibull model kinetics. The optimized film, F1, exhibited significantly higher (p < 0.005) rizatriptan buccal flux (71.94 ± 8.26 µg/cm2/h) with a short lag time. Film features suggested the drug particles were in an amorphous form, compatible with the polymers used and had an appropriate surface morphology suitable for buccal application. Pharmacokinetic data indicated a significantly higher rizatriptan plasma level (p < 0.005) and Cmax (p < 0.0001) upon buccal film application as compared to oral solution. The observed AUC0–12h (994.86 ± 95.79 ng.h/mL) in buccal treatment was two-fold higher (p < 0.0001) than the control, and the relative bioavailability judged was 245%. This investigation demonstrates the prospective of buccal films as a viable and alternative approach for effective rizatriptan delivery.

Does fed‐state associated prolonged gastric emptying affect drug transport kinetics in intestine?

In vitro dissolution testing to estimate the likelihood of food-effect for the solubility-limited drugs is recommended by the regulatory agencies; however, the effect of changes in physiology such as delayed gastric emptying after food intake cannot be simulated in a dissolution apparatus. To address this, we performed metanalysis of food-effect studies and investigated the effect of food on drug bioavailability due to the changes in physiology and drug properties in fed-state. Our specific aims were to: i) identify the determinants of food-effect on drug absorption, ii) determine the magnitude by which fed-state associated physiological changes affect the absorption of efflux transporter substrates, and iii) measure the effect of high-fat versus low-fat diets on the magnitude of food-effect for the efflux transporter substrates. A systematic meta-analysis of clinical food-effect studies on 311 drugs was performed to evaluate the association of food-effect magnitude with drug- and physiology-specific properties (i.e., change in maximal plasma concentration, Cmax, and area under the plasma concentration-time profile curve, AUC). Of the studied drugs, 124 and 88 drugs showed positive and negative food-effects, respectively, whereas 99 showed no food-effect. Five deterministic properties that influence food-effect were identified, i.e., logP, log dose number, metabolic extraction ratio (EH), and saturation indices of intestinal apical uptake and efflux transporters (Equation 1). In particular, a majority of the drugs with efficient efflux transport (saturation index ≥2) showed negative food-effect. Since these data cannot be explained by dissolution testing, the negative food-effect for the efflux transporter substrates is likely a result of prolonged gastric emptying time in fed-state that leads to increased efflux transport efficiency (luminal drug concentration < Michaelis-Menten constant, Km) (Figure 1A). For example, drugs with saturation index ≥2, such as didanosine, voriconazole, erythromycin, omadacycline, and asciminib, showed 50-67% decrease in Cmax and AUC. Moreover, prolonged gastric emptying time with high-fat diet is associated with a greater negative food-effect as compared to low-fat diet conditions in these transporter substrates. For example, omadacycline, eltrombopag, indinavir, and asciminib showed significantly decreased Cmax (P <0.01) and AUC (P <0.001) with high-fat diet (Figure 1B). The present study is the first to confirm the impact of fed-state associated prolonged gastric emptying time on the saturable kinetics of efflux transporter substrates. Preclinical validation of the postulated mechanism is ongoing in our laboratory. The understanding and integration of changes in physiology and drug properties will allow prospective prediction of food-effect on oral drug absorption.

Pharmacokinetics of Tildipirosin in Healthy and Mycoplasma gallisepticum Infected Chickens

The pharmacokinetic features of tildipirosin were explored following a single dose of 4 mg/kg in healthy and Mycoplasma gallisepticum (M. gallisepticum) infected chickens. Eighteen healthy chickens (400-500g) were allocated into 3 groups (n=6); group I and II were received tildipirosin by intravenous (IV) and intramuscular (IM) routes, respectively. Group III was experimentally infected with M. gallisepticum and injected IM with tildipirosin after confirming the infection (9-10 days after inoculation of M. gallisepticum). Plasma samples were harvested at different time points until 14 days after tildipirosin injection to measure its concentrations using HPLC. After IM administration of tildipirosin in healthy chickens, the maximum concentration in plasma (Cmax), time to achieve Cmax (Tmax), area under the plasma concentration time curve from 0 to last time (AUC0-last), clearance (Cl-F-obs) and the absolute bioavailability were recorded to be 403.76ng/ml, 0.25 hr, 6.82 µg.hr/ml, 0.56L/hr/kg, and 103.50% respectively. Cmax and AUC0-last, were significantly lower in infected than healthy chickens, while Cl-F-obs was significantly higher in infected than healthy chickens. Therefore, M. gallispeticum infection produced significant changes in some of the pharmacokinetic parameters of tildipirosin in chickens. Further studies are warranted to assess pharmacokinetic/ pharmacodynamic profile of tildipirosin against M. gallisepticum in chickens and to gain deeper insight into its safety utilization in chickens.

Apigenin-Loaded PLGA-DMSA Nanoparticles: A Novel Strategy to Treat Melanoma Lung Metastasis.

The flavone apigenin (APG), alone as well as in combination with other chemotherapeutic agents, is known to exhibit potential anticancer effects in various tumors and inhibit growth and metastasis of melanoma. However, the potential of apigenin nanoparticles (APG-NPs) to prevent lung colonization of malignant melanoma has not been well investigated. APG-loaded PLGA-NPs were surface-functionalized with meso-2,3-dimercaptosuccinic acid (DMSA) for the treatment of melanoma lung metastasis. DMSA-conjugated APG-loaded NPs (DMSA-APG-NPs) administered by an oral route exhibited sustained APG release and showed considerable enhancement of plasma half-life, Cmax value, and bioavailability compared to APG-NPs both in plasma and the lungs. DMSA-conjugated APG-NPs showed comparably higher cellular internalization in B16F10 and A549 cell lines compared to that of plain NPs. Increased cytotoxicity was observed for DMSA-APG-NPs compared to APG-NPs in A549 cells. This difference between the two formulations was lower in B16F10 cells. Significant depolarization of mitochondrial transmembrane potential and an enhanced level of caspase activity were observed in B16F10 cells treated with DMSA-APG-NPs compared to APG-NPs as well. Western blot analysis of various proteins was performed to understand the mechanism of apoptosis as well as prevention of melanoma cell migration and invasion. DMSA conjugation substantially increased accumulation of DMSA-APG-NPs given by an intravenous route in the lungs compared to APG-NPs at 6 and 8 h. This was also corroborated by scintigraphic imaging studies with radiolabeled formulations administered by an intravenous route. Conjugation also allowed comparatively higher penetration as evident from an in vitro three-dimensional tumor spheroid model study. Finally, the potential therapeutic efficacy of the formulation was established in experimental B16F10 lung metastases, which suggested an improved bioavailability with enhanced antitumor and antimetastasis efficacy of DMSA-conjugated APG-NPs following oral administration.

Study on the bioavailability of stevioside-encapsulized lutein and its mechanism

This study aims to develop novel lutein nanoparticles encapsulized by stevioside (LUT-STE, 165 ± 2 nm average particles size) and systematically evaluate its bioavailability. Multiple spectroscopy and NMR analyses showed lutein and stevioside could interact through hydrogen bonds, CHπ interaction and van der Waals forces. Molecular docking simulation showed lutein was well distributed in the hydrophobic cavity of stevioside. Analyzed by Caco-2 cellular models, the transported amount of LUT-STE was 2.39 times that of lutein in 120 min with a Papp (B → A)/Papp (A → B) value of 0.63 ± 0.04. Nystatin and dynasore significantly reduced the cellular uptake of LUT-STE by 41.3% and 57.7%, respectively. Compared with free lutein, LUT-STE increased the Cmax in mice plasma by 5.01-fold and promoted the accumulation in multiple organs. LUT-STE promoted the protein expressions of CD36, NPC1L1 and PPARγ in both cell and animal models. In conclusion, stevioside entrapment significantly promote the bioavailability of lutein through multiple transmembrane pathways.

The role of drug efflux and uptake transporters ABCB1 (P-gp), ABCG2 (BCRP) and OATP1A/1B and of CYP3A4 in the pharmacokinetics of the CDK inhibitor milciclib

The promising anticancer drug milciclib potently inhibits cyclin-dependent kinase (CDK) 2 and tropomyosin receptor kinase (TRK) A, and is currently in phase II clinical studies. To characterize factors affecting milciclib pharmacokinetics, we investigated whether milciclib is a substrate of the multidrug efflux and uptake transporters ABCB1 (P-gp), ABCG2 (BCRP), and OATP1A/1B, and the drug-metabolizing enzyme CYP3A, using genetically-modified mouse models and Madin-Darby Canine Kidney (MDCK-II) cells. In vitro, milciclib was transported by mAbcg2, and this was inhibited by the ABCG2 inhibitor Ko143. Upon oral administration of milciclib, its plasma exposure in Abcb1a/1b−/−, Abcg2−/−, and Abcb1a/1b;Abcg2−/− mice was similar to that found in wild-type mice. Milciclib showed good brain penetration even in wild-type mice (brain-to-plasma ratio of 1.2), but this was further increased by 5.2-fold when both Abcb1 and Abcg2 were ablated, and to a lesser extent in single Abcb1- or Abcg2-deficient mice. Oatp1a/1b deficiency had only a minor impact on the milciclib plasma AUC0-24h and Cmax. The milciclib AUC0-8h increased 1.9-fold in Cyp3a−/− mice but decreased only 1.3-fold upon overexpression of human CYP3A4. Thus, ABCB1 and ABCG2 cooperatively limit milciclib brain penetration. The low impact of OATP1 and CYP3A could be clinically favorable for milciclib, reducing the risks of unintended drug-drug interactions or interindividual variation in CYP3A4 activity.

Population Pharmacokinetics Analysis of Amikacin Initial Dosing Regimen in Elderly Patients.

There are limited data of amikacin pharmacokinetics (PK) in the elderly population. Hence, we aimed to describe the population PK of amikacin in elderly patients (>70 years old) and to establish optimized initial dosing regimens. We simulated individual maximum concentrations in plasma (Cmax) and minimal concentrations (Cmin) for several dosing regimens (200–2000 mg every 24, 48, and 72 h) for patients with creatinine clearance (CCr) of 10–90 mL/min and analyzed efficacy (Cmax/minimal inhibitory concentration (MIC) ≥ 8) for MICs of 4, 8, and 16 mg/L and safety (Cmin < 4 mg/L). A one-compartment model best described the data. CCr was the only covariate associated with amikacin clearance. The population PK parameter estimates were 2.25 L/h for clearance and 18.0 L for volume of distribution. Dosing simulations recommended the dosing regimens (1800 mg) with dosing intervals ranging 48–72 h for patients with CCr of 40–90 mL/min based on achievement of both efficacy for the MIC of 8 mg/L and safety. None of the dosing regimens achieved the targets for an MIC of 16 mg/L. We recommend the initial dosing regimen using a nomogram based on CCr for an MIC of ≤8 mg/L in elderly patients with CCr of 40–90 mL/min.