Assessment of the Induction of Dormant Ring Stages in Plasmodium falciparum Parasites by Artemisone and Artemisone Entrapped in Pheroid Vesicles In Vitro

The in vitro antimalarial activities of artemisone and artemisone entrapped in Pheroid vesicles were compared, as was their ability to induce dormancy in Plasmodium falciparum. There was no increase in the activity of artemisone entrapped in Pheroid vesicles against multidrug-resistant P. falciparum lines. Artemisone induced the formation of dormant ring stages similar to dihydroartemisinin. Thus, the Pheroid delivery system neither improved the activity of artemisone nor prevented the induction of dormant rings.     

Treatment of Murine Cerebral Malaria by Artemisone in Combination with Conventional Antimalarial Drugs: Antiplasmodial Effects and Immune Responses

The decreasing effectiveness of antimalarial therapy due to drug resistance necessitates constant efforts to develop new drugs. Artemisinin derivatives are the most recent drugs that have been introduced and are considered the first line of treatment, but there are already indications of Plasmodium falciparum resistance to artemisinins. Consequently, drug combinations are recommended for prevention of the induction of resistance. The research here demonstrates the effects of novel combinations of the new artemisinin derivative, artemisone, a recently described 10-alkylamino artemisinin derivative with improved antimalarial activity and reduced neurotoxicity. We here investigate its ability to kill P. falciparum in a high-throughput in vitro assay and to protect mice against lethal cerebral malaria caused by Plasmodium berghei ANKA when used alone or in combination with established antimalarial drugs. Artemisone effects against P. falciparum in vitro were synergistic with halofantrine and mefloquine, and additive with 25 other drugs, including chloroquine and doxycycline. The concentrations of artemisone combinations that were toxic against THP-1 cells in vitro were much higher than their effective antimalarial concentration. Artemisone, mefloquine, chloroquine, or piperaquine given individually mostly protected mice against cerebral malaria caused by P. berghei ANKA but did not prevent parasite recrudescence. Combinations of artemisone with any of the other three drugs did completely cure most mice of malaria. The combination of artemisone and chloroquine decreased the ratio of proinflammatory (gamma interferon, tumor necrosis factor) to anti-inflammatory (interleukin 10 [IL-10], IL-4) cytokines in the plasma of P. berghei-infected mice. Thus, artemisone in combinations with other antimalarial drugs might have a dual action, both killing parasites and limiting the potentially deleterious host inflammatory response.     

Double-Blind Evaluation of the Safety and Pharmacokinetics of Multiple Oral Once-Daily 750-Milligram and 1-Gram Doses of Levofloxacin in Healthy Volunteers

The safety and pharmacokinetics of once-daily oral levofloxacin in 16 healthy male volunteers were investigated in a randomized, double-blind, placebo-controlled study. Subjects were randomly assigned to the treatment (n = 10) or placebo group (n = 6). In study period 1, 750 mg of levofloxacin or a placebo was administered orally as a single dose on day 1, followed by a washout period on days 2 and 3; dosing resumed for days 4 to 10. Following a 3-day washout period, 1 g of levofloxacin or a placebo was administered in a similar fashion in period 2. Plasma and urine levofloxacin concentrations were measured by high-pressure liquid chromatography. Pharmacokinetic parameters were estimated by model-independent methods. Levofloxacin was rapidly absorbed after single and multiple once-daily 750-mg and 1-g doses with an apparently large volume of distribution. Peak plasma levofloxacin concentration (C_max) values were generally attained within 2 h postdose. The mean values of C_max and area under the concentration-time curve from 0 to 24 h (AUC_0–24) following a single 750-mg dose were 7.1 μg/ml and 71.3 μg · h/ml, respectively, compared to 8.6 μg/ml and 90.7 μg · h/ml, respectively, at steady state. Following the single 1-g dose, mean C_max and AUC_0–24 values were 8.9 μg/ml and 95.4 μg · h/ml, respectively; corresponding values at steady state were 11.8 μg/ml and 118 μg · h/ml. These C_max and AUC_0–24 values indicate modest and similar degrees of accumulation upon multiple dosing at the two dose levels. Values of apparent total body clearance (CL/F), apparent volume of distribution (V_ss/F), half-life (t_1/2), and renal clearance (CL_R) were similar for the two dose levels and did not vary from single to multiple dosing. Mean steady-state values for CL/F, V_ss/F, t_1/2, and CL_R following 750 mg of levofloxacin were 143 ml/min, 100 liters, 8.8 h, and 116 ml/min, respectively; corresponding values for the 1-g dose were 146 ml/min, 105 liters, 8.9 h, and 105 ml/min. In general, the pharmacokinetics of levofloxacin in healthy subjects following 750-mg and 1-g single and multiple once-daily oral doses appear to be consistent with those found in previous studies of healthy volunteers given 500-mg doses. Levofloxacin was well tolerated at either high dose level. The most frequently reported drug-related adverse events were nausea and headache.     

Antimalarial efficacy and drug interactions of the novel semi-synthetic endoperoxide artemisone in vitro and in vivo

OBJECTIVES: The in vitro and in vivo efficacy and drug-drug interactions of the novel semi-synthetic endoperoxide artemisone with standard antimalarials were investigated in order to provide the basis for the selection of the best partner drug. METHODS: Antimalarial activity and drug interactions were evaluated in vitro against Plasmodium falciparum by the incorporation of [(3)H]hypoxanthine. In vivo efficacy and drug interactions were assessed using the standard 4-day Peters' test. RESULTS: Artemisone was 10 times more potent than artesunate in vitro against a panel of 12 P. falciparum strains, independent of their susceptibility profile to antimalarial drugs, and consistently 4 to 10 times more potent than artesunate in rodent models against drug-susceptible and primaquine- or sulfadoxine/pyrimethamine-resistant Plasmodium berghei lines and chloroquine- or artemisinin-resistant lines of Plasmodium yoelii. Slight antagonistic trends were found between artemisone and chloroquine, amodiaquine, tafenoquine, atovaquone or pyrimethamine and additive to slight synergistic trends with artemisone and mefloquine, lumefantrine or quinine. Various degrees of synergy were observed in vivo between artemisone and mefloquine, chloroquine or clindamycin. CONCLUSIONS: These results confirm the increased efficacy of artemisone over artesunate against multidrug-resistant P. falciparum and provide the basis for the selection of potential partner drugs for future deployment in areas of multidrug-resistant malaria. Artemisone represents an important addition to the repertoire of artemisinin combination therapies currently in use, as it has enhanced antimalarial activity, improved bioavailability and stability over current endoperoxides.     

Ex Vivo Activity of Endoperoxide Antimalarials,Including Artemisone and Arterolane,against Multidrug-Resistant Plasmodium falciparum Isolates from Cambodia

Novel synthetic endoperoxides are being evaluated as new components of artemisinin combination therapies (ACTs) to treat artemisinin-resistant Plasmodium falciparum malaria. We conducted blinded ex vivo activity testing of fully synthetic (OZ78 and OZ277) and semisynthetic (artemisone, artemiside, artesunate, and dihydroartemisinin) endoperoxides in the histidine-rich protein 2 enzyme-linked immunosorbent assay against 200 P. falciparum isolates from areas of artemisinin-resistant malaria in western and northern Cambodia in 2009 and 2010. The order of potency and geometric mean (GM) 50% inhibitory concentrations (IC₅₀s) were as follows: artemisone (2.40 nM) > artesunate (8.49 nM) > dihydroartemisinin (11.26 nM) > artemiside (15.28 nM) > OZ277 (31.25 nM) > OZ78 (755.27 nM). Ex vivo activities of test endoperoxides positively correlated with dihydroartemisinin and artesunate. The isolates were over 2-fold less susceptible to dihydroartemisinin than the artemisinin-sensitive P. falciparum W2 clone and showed sensitivity comparable to those with test endoperoxides and artesunate, with isolate/W2 IC₅₀ susceptibility ratios of <2.0. All isolates had P. falciparum chloroquine resistance transporter mutations, with negative correlations in sensitivity to endoperoxides and chloroquine. The activities of endoperoxides (artesunate, dihydroartemisinin, OZ277, and artemisone) significantly correlated with that of the ACT partner drug, mefloquine. Isolates had mutations associated with clinical resistance to mefloquine, with 35% prevalence of P. falciparum multidrug resistance gene 1 (pfmdr1) amplification and 84.5% occurrence of the pfmdr1 Y184F mutation. GM IC₅₀s for mefloquine, lumefantrine, and endoperoxides (artesunate, dihydroartemisinin, OZ277, OZ78, and artemisone) correlated with pfmdr1 copy number. Given that current ACTs are failing potentially from reduced sensitivity to artemisinins and partner drugs, newly identified mutations associated with artemisinin resistance reported in the literature and pfmdr1 mutations should be examined for their combined contributions to emerging ACT resistance.     

Pharmacokinetics and tolerability of multiple-dose rosuvastatin: An open-label, randomized-sequence, three-way crossover trial in healthy Chinese volunteers

Background: Rosuvastatin has been reported to be beneficial in the treatment of dyslipidemia. The C_max and AUC_0−t of rosuvastatin were reported to be ~2 to 4 times higher in Chinese subjects compared with white subjects after administration of a single 1-mg/kg dose.Objectives: The aims of this study were to assess the pharmacokinetics and tolerability of multiple doses of rosuvastatin in healthy Chinese volunteers.Methods: This open-label, randomized-sequence, 3-way crossover trial consisted of three 7-day treatment periods and two 10-day washout periods. Healthy volunteers were randomly allocated to 1 of 3 daily treatment regimens: rosuvastatin 5, 10, or 20 mg. To assess the pharmacokinetics and tolerability of rosuvastatin, blood samples were drawn before dosing (hour 0) on days 5, 6, and 7 and 0.5, 1, 1.5, 2, 3, 4, 5, 6, 8, 12, 15, 24, 36, 48, 72, and 96 hours after the final dose was administered on day 7. A validated HPLC-MS/MS method was used to determine rosuvastatin levels. A 2-compartment pharmacokinetic model was fitted to the plasma concentration-time profiles obtained for each volunteer. Adverse events (AEs) were monitored throughout the study via subject interview, vital signs, and blood sampling. Serious AEs were those requiring hospitalization, treatment discontinuation, or resulting in death.Results: Twelve healthy Chinese volunteers (6 men: mean [SD] age, 21.8 [1.7] years; weight, 62.3 [5.8] kg; height, 174.3 [7.2] cm; 6 women: age, 20.8 [1.2] years; weight, 53.2 [4.7] kg; height, 161.3 [4.3] cm) participated in and completed the trial. The mean (SD) steady-state C_max was significantly greater after ro-suvastatin administration in the 20-mg group compared with the 5-mg group (37.69 [29.83] vs 6.17 [6.03] ng/mL; P = 0.04). The t_1/2 was significantly greater in the 20-mg group (15.51 [6.43] hours) compared with the 5-mg group (5.65 [5.08] hours; P = 0.001) and the 10-mg group (8.58 [5.17] hours; P = 0.002). The mean AUC_0−t was significantly greater in the 20-mg group compared with the 5-mg group (349.16 [257.20] vs 40.63 [39.31] ng/mL/h; P = 0.02). All AEs were considered by the investigators to be mild in intensity, with the exception of 2 cases of abdominal discomfort (1 man and 1 woman, both in the 5-mg dose group). Two women in the 20-mg group experienced dizziness and cold sweats simultaneously. In the 10-mg group, 1 woman had abdominal discomfort and nausea and 1 woman had jaw pain. All reported AEs were considered possibly related to study drug administration.Conclusions: In this small study in healthy Chinese volunteers, rosuvastatin systemic exposure appeared to be dose-proportional over the dosing range of 5 to 20 mg with multiple-dose administration. There was no accumulation of rosuvastatin in the body with the 5- and 10-mg doses. However, the results suggest that rosuva-statin might accumulate when the dose is increased to 20 mg. No serious AEs occurred in any of the 3 dosing groups.     

Pharmacokinetics and bioequivalence of two formulations of rebamipide 100-mg tablets: A randomized,single-dose,two-period,two-sequence crossover study in healthy Korean male volunteers

Background: Rebamipide is a quinolinone-derived gastroprotective agent approved in Korea for the treatment of gastric ulcers, acute gastritis, and exacerbated chronic gastritis.Objectives: The aims of this study were to evaluate the pharmacokinetics and bioequivalence of a reference (branded) and test (generic) formulation of rebamipide 100-mg tablets in healthy Korean male volunteers for the purposes of generic substitution and to evaluate the relationship between genetic polymorphisms in the ABCB1 gene (exons 21 and 26) and rebamipide pharmacokinetics.Methods: This study had a 2-period crossover design, with a 7-day washout between formulations. Healthy Korean male volunteers were randomly assigned to receive a single 100-mg dose of the test or reference formulation, administered with 240 mL of water after a 12-hour overnight fast. Serum concentrations of rebamipide up to 12 hours after administration were determined using a validated HPLC method with fluorescence detection. Vital signs (temperature, blood pressure, and heart rate) were measured before and after dosing in both periods. Adverse events were monitored by clinic staff on the days of study drug administration and were recorded for up to 1 week after the last dose of study medication. Pharmacokinetic parameters were determined using a noncompartmental method. The formulations were considered bioequivalent if the log-transformed ratios of AUC_0?t, AUC_0?∞), and C_max were within the predetermined bioequivalence range (80%–125%) established by the US Food and Drug Administration and Korean legislation. The in vitro dissolution profiles of the 2 formulations were examined, and the influence on rebamipide pharmacokinetics of genetic polymorphisms in the ABCB1 gene (P-glycoprotein) was investigated.Results: Thirty healthy Korean male volunteers (mean [SD] age, 22.97 [1.67] years [range, 20–27 years]; height, 174.56 [6.27] cm [range, 159.1–184.8 cm]; and weight, 69.44 [8.32] kg [range, 54.7–90.2 kg]) were enrolled in and completed the study. No adverse events were reported. The 2 formulations had comparable in vitro dissolution profiles. The mean AUC_0?t for the test and reference formulations was 831.09 (329.52) and 903.46 (419.17) ng/mL/h, respectively; the AUC_0?∞ was 851.68 (332.62) and 923.58 (423.21) ng/mL/h; the C_max was 218.12 (93.90) and 220.57 (107.48) ng/mL; the T_max was 2.05 (1.15) and 2.10 (0.76) hours; and the t_½ was 1.96 (0.52) and 1.93 (0.49) hours. No significant sequence, subject, formulation, or period effects were detected for any pharmacokinetic parameter. The point estimates for AUC_0?t, AUC_0?∞, and C_max were 0.95 (90% CI, 0.84–1.06), 0.95 (90% CI, 0.84–1.06), and 1.01 (90% CI, 0.89–1.15), respectively, satisfying the criterion for bioequivalence. There was no statistically significant difference in T_max. No significant differences in rebamipide AUC_0?t, AUC_0?∞, or C_max were found among the ABCB1 2677 GG, GT, or TT groups, or among the ABCB1 3435 CC, CT, or TT groups. There was no evidence that genetic polymorphisms in the ABCB1 gene influenced the pharmacokinetics of rebamipide.Conclusions: The results of this study in healthy Korean male volunteers suggest that the 2 rebamipide 100-mg tablet formulations administered in the fasted state met the regulatory criterion for bioequivalence. There was no evidence that rebamipide pharmacokinetic parameters were influenced by genetic polymorphisms in the ABCB1 gene (exons 21 and 26). ClinicalTrials.gov identifier: NCT00997789     

JPC-2997, a New Aminomethylphenol with High In Vitro and In Vivo Antimalarial Activities against Blood Stages of Plasmodium

4-(tert-Butyl)-2-((tert-butylamino)methyl)-6-(6-(trifluoromethyl)pyridin-3-yl)-phenol (JPC-2997) is a new aminomethylphenol compound that is highly active in vitro against the chloroquine-sensitive D6, the chloroquine-resistant W2, and the multidrug-resistant TM90-C2B Plasmodium falciparum lines, with 50% inhibitory concentrations (IC_50s) ranging from 7 nM to 34 nM. JPC-2997 is >2,500 times less cytotoxic (IC₅₀s > 35 μM) to human (HepG2 and HEK293) and rodent (BHK) cell lines than the D6 parasite line. In comparison to the chemically related WR-194,965, a drug that had advanced to clinical studies, JPC-2997 was 2-fold more active in vitro against P. falciparum lines and 3-fold less cytotoxic. The compound possesses potent in vivo suppression activity against Plasmodium berghei, with a 50% effective dose (ED₅₀) of 0.5 mg/kg of body weight/day following oral dosing in the Peters 4-day test. The radical curative dose of JPC-2997 was remarkably low, at a total dose of 24 mg/kg, using the modified Thompson test. JPC-2997 was effective in curing three Aotus monkeys infected with a chloroquine- and pyrimethamine-resistant strain of Plasmodium vivax at a dose of 20 mg/kg daily for 3 days. At the doses administered, JPC-2997 appeared to be well tolerated in mice and monkeys. Preliminary studies of JPC-2997 in mice show linear pharmacokinetics over the range 2.5 to 40 mg/kg, a low clearance of 0.22 liters/h/kg, a volume of distribution of 15.6 liters/kg, and an elimination half-life of 49.8 h. The high in vivo potency data and lengthy elimination half-life of JPC-2997 suggest that it is worthy of further preclinical assessment as a partner drug.     

New Dosing Strategies for an Old Antibiotic: Pharmacodynamics of Front-Loaded Regimens of Colistin at Simulated Pharmacokinetics in Patients with Kidney or Liver Disease

Increasing evidence suggests that colistin monotherapy is suboptimal at currently recommended doses. We hypothesized that front-loading provides an improved dosing strategy for polymyxin antibiotics to maximize killing and minimize total exposure. Here, we utilized an in vitro pharmacodynamic model to examine the impact of front-loaded colistin regimens against a high bacterial density (10⁸ CFU/ml) of Pseudomonas aeruginosa. The pharmacokinetics were simulated for patients with hepatic (half-life [t_1/2] of 3.2 h) or renal (t_1/2 of 14.8 h) disease. Front-loaded regimens (n = 5) demonstrated improvement in bacterial killing, with reduced overall free drug areas under the concentration-time curve (fAUC) compared to those with traditional dosing regimens (n = 14) with various dosing frequencies (every 12 h [q12h] and q24h). In the renal failure simulations, front-loaded regimens at lower exposures (fAUC of 143 mg · h/liter) obtained killing activity similar to that of traditional regimens (fAUC of 268 mg · h/liter), with an ∼97% reduction in the area under the viable count curve over 48 h. In hepatic failure simulations, front-loaded regimens yielded rapid initial killing by up to 7 log₁₀ within 2 h, but considerable regrowth occurred for both front-loaded and traditional regimens. No regimen eradicated the high bacterial inoculum of P. aeruginosa. The current study, which utilizes an in vitro pharmacodynamic infection model, demonstrates the potential benefits of front-loading strategies for polymyxins simulating differential pharmacokinetics in patients with hepatic and renal failure at a range of doses. Our findings may have important clinical implications, as front-loading polymyxins as a part of a combination regimen may be a viable strategy for aggressive treatment of high-bacterial-burden infections.     

Pharmacokinetic,Pharmacodynamic, and Safety Profiles of Ferric Carboxymaltose in Chinese Patients with Iron-deficiency Anemia

PurposeIron deficiency (ID) is one of the most commonly known nutritional deficiencies and is considered the primary cause of anemia (iron-deficiency anemia). Ferric carboxymaltose (FCM), an intravenous iron preparation, has been widely used for >10 years for iron-deficiency anemia treatment worldwide because of its many advantages.MethodsThis single-center, open-label, single dose escalation study in Chinese subjects was designed to assess the pharmacokinetic/pharmacodynamic parameters and safety of FCM in this population. The first 12 subjects received a 500-mg dose; after assessing safety data from the first 6 subjects in this cohort, another 12 subjects were assigned to the 1000-mg dose cohort.FindingsAfter an infusion of FCM over 15 min, a rapid dose-dependent increase in total serum iron levels was observed with a median T_max of 30 min following the start of the infusion for both cohorts. The C_max and AUC for the 1000-mg dose were ~1.8-fold (p = 0.2929) and 2.3-fold (p = 0.0318) those associated with the 500-mg dose, respectively. Mean terminal t_1/2 values were 12.3 and 10.5 h for the 2 cohorts. The renal elimination of FCM was negligible (<0.1%). Increase in mean serum iron levels and ferritin concentrations showed dose dependency. Iron-binding capacity was transiently well utilized after dosing, as indicated by transferrin saturation >88% with 500-mg FCM and >90% with 1000-mg FCM. Hemoglobin levels did not show significant changes during the 7-day observation period, whereas mean reticulocyte counts significantly increased in both cohorts, suggesting activation of the hematopoietic system. FCM was well tolerated in these Chinese subjects. No new or unexpected treatment-emergent adverse events were attributable to FCM.ImplicationsThe pharmacokinetic/pharmacodynamic and safety profiles in Chinese subjects seemed comparable to those in white and Japanese populations. ChinaDrugTrials.org.cn identifier: CTR20160863     

Linking Murine and Human Plasmodium falciparum Challenge Models in a Translational Path for Antimalarial Drug Development

Effective progression of candidate antimalarials is dependent on optimal dosing in clinical studies, which is determined by a sound understanding of pharmacokinetics and pharmacodynamics (PK/PD). Recently, two important translational models for antimalarials have been developed: the NOD/SCID/IL2Rγ^−/− (NSG) model, whereby mice are engrafted with noninfected and Plasmodium falciparum-infected human erythrocytes, and the induced blood-stage malaria (IBSM) model in human volunteers. The antimalarial mefloquine was used to directly measure the PK/PD in both models, which were compared to previously published trial data for malaria patients. The clinical part was a single-center, controlled study using a blood-stage Plasmodium falciparum challenge inoculum in volunteers to characterize the effectiveness of mefloquine against early malaria. The study was conducted in three cohorts (n = 8 each) using different doses of mefloquine. The characteristic delay in onset of action of about 24 h was seen in both NSG and IBSM systems. In vivo 50% inhibitory concentrations (IC₅₀s) were estimated at 2.0 μg/ml and 1.8 μg/ml in the NSG and IBSM models, respectively, aligning with 1.8 μg/ml reported previously for patients. In the IBSM model, the parasite reduction ratios were 157 and 195 for the 10- and 15-mg/kg doses, within the range of previously reported clinical data for patients but significantly lower than observed in the mouse model. Linking mouse and human challenge models to clinical trial data can accelerate the accrual of critical data on antimalarial drug activity. Such data can guide large clinical trials required for development of urgently needed novel antimalarial combinations. (This trial was registered at the Australian New Zealand Clinical Trials Registry [http://anzctr.org.au] under registration number ACTRN12612000323820.)     

Pharmacokinetics,Microbial Response,and Pulmonary Outcomes of Multidose Intravenous Azithromycin in Preterm Infants at Risk for Ureaplasma Respiratory Colonization

The study objectives were to refine the population pharmacokinetics (PK) model, determine microbial clearance, and assess short-term pulmonary outcomes of multiple-dose azithromycin treatment in preterm infants at risk for Ureaplasma respiratory colonization. Fifteen subjects (7 of whom were Ureaplasma positive) received intravenous azithromycin at 20 mg/kg of body weight every 24 h for 3 doses. Azithromycin concentrations were determined in plasma samples obtained up to 168 h post-first dose by using a validated liquid chromatography-tandem mass spectrometry method. Respiratory samples were obtained predose and at three time points post-last dose for Ureaplasma culture, PCR, antibiotic susceptibility testing, and cytokine concentration determinations. Pharmacokinetic data from these 15 subjects as well as 25 additional subjects (who received either a single 10-mg/kg dose [n = 12] or a single 20-mg/kg dose [n = 13]) were analyzed by using a nonlinear mixed-effect population modeling (NONMEM) approach. Pulmonary outcomes were assessed at 36 weeks post-menstrual age and 6 months adjusted age. A 2-compartment model with all PK parameters allometrically scaled on body weight best described the azithromycin pharmacokinetics in preterm neonates. The population pharmacokinetics parameter estimates for clearance, central volume of distribution, intercompartmental clearance, and peripheral volume of distribution were 0.15 liters/h · kg^0.75, 1.88 liters · kg, 1.79 liters/h · kg^0.75, and 13 liters · kg, respectively. The estimated area under the concentration-time curve over 24 h (AUC₂₄)/MIC₉₀ value was ∼4 h. All posttreatment cultures were negative, and there were no drug-related adverse events. One Ureaplasma-positive infant died at 4 months of age, but no survivors were hospitalized for respiratory etiologies during the first 6 months (adjusted age). Thus, a 3-day course of 20 mg/kg/day intravenous azithromycin shows preliminary efficacy in eradicating Ureaplasma spp. from the preterm respiratory tract.     

First-in-Humans Study of the Safety,Tolerability, and Pharmacokinetics of ACT-451840, a New Chemical Entity with Antimalarial Activity

Emerging resistance to antimalarial agents raises the need for new drugs. ACT-451840 is a new compound with potent activity against sensitive and resistant Plasmodium falciparum strains. This was a first-in-humans single-ascending-dose study to investigate the safety, tolerability, and pharmacokinetics of ACT-451840 across doses of 10, 50, 200, and 500 mg in healthy male subjects. In the 200- and 500-mg dose groups, the effect of food was investigated, and antimalarial activity was assessed using an ex vivo bioassay with P. falciparum. No (serious) adverse events leading to discontinuation were reported. At the highest dose level, the peak drug concentration (C_max) and the area under the plasma concentration-time curve from zero to infinity of ACT-451840 under fasted conditions reached 11.9 ng/ml and 100.6 ng · h/ml, respectively, and these were approximately 13-fold higher under fed conditions. Food did not affect the half-life (approximately 34 h) of the drug, while the C_max was attained 2.0 and 3.5 h postdose under fasted and fed conditions, respectively. The plasma concentrations estimated by the bioassay were approximately 4-fold higher than those measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Several potentially active metabolites were also identified. ACT-451840 was well tolerated across all doses. Exposure to ACT-451840 significantly increased with food. The bioassay indicated the presence of circulating active metabolites. (This study has been registered at ClinicalTrials.gov under registration no. {"type":"clinical-trial","attrs":{"text":"NCT02186002","term_id":"NCT02186002"}}NCT02186002.)     

Population Pharmacokinetics of Fosfomycin in Critically Ill Patients

This study describes the population pharmacokinetics of fosfomycin in critically ill patients. In this observational study, serial blood samples were taken over several dosing intervals of intravenous fosfomycin treatment. Blood samples were analyzed using a validated liquid chromatography-tandem mass spectrometry technique. A population pharmacokinetic analysis was performed using nonlinear mixed-effects modeling. Five hundred fifteen blood samples were collected over one to six dosing intervals from 12 patients. The mean (standard deviation) age was 62 (17) years, 67% of patients were male, and creatinine clearance (CL_CR) ranged from 30 to 300 ml/min. A two-compartment model with between-subject variability on clearance and volume of distribution of the central compartment (V_c) described the data adequately. Calculated CL_CR was supported as a covariate on fosfomycin clearance. The mean parameter estimates for clearance on the first day were 2.06 liters/h, V_c of 27.2 liters, intercompartmental clearance of 19.8 liters/h, and volume of the peripheral compartment of 22.3 liters. We found significant pharmacokinetic variability for fosfomycin in this heterogeneous patient sample, which may be explained somewhat by the observed variations in renal function.     

Pharmacodynamics of a Simulated Single 1,200-Milligram Dose of Oritavancin in an In Vitro Pharmacokinetic/Pharmacodynamic Model of Methicillin-Resistant Staphylococcus aureus Infection

The safety and efficacy of a single 1,200-mg dose of the lipoglycopeptide oritavancin are currently being investigated in two global phase 3 studies of acute bacterial skin and skin structure infections. In this study, an in vitro pharmacokinetic/pharmacodynamic model was established to compare the free-drug pharmacodynamics associated with a single 1,200-mg dose of oritavancin to once-daily dosing with daptomycin at 6 mg/kg of body weight and twice-daily dosing with vancomycin at 1,000 mg against three methicillin-resistant Staphylococcus aureus (MRSA) strains over 72 h. The area under the bacterial-kill curve (AUBKC) was used to assess the antibacterial effect of each dosing regimen at 24 h (AUBKC_0-24), 48 h (AUBKC_0-48), and 72 h (AUBKC_0-72). The rapid bactericidal activities of oritavancin and daptomycin contributed to lower AUBKC_0-24s for the three MRSA strains than with vancomycin (P < 0.05, as determined by analysis of variance [ANOVA]). Oritavancin exposure also resulted in a lower AUBKC_0-48 and AUBKC_0-72 against one MRSA strain and a lower AUBKC_0-48 for another strain than did vancomycin exposure (P < 0.05). Furthermore, daptomycin exposure resulted in a lower AUBKC_0-48 and AUBKC_0-72 for one of the MRSA isolates than did vancomycin exposure (P < 0.05). Lower AUBKC_0-24s for two of the MRSA strains (P < 0.05) were obtained with oritavancin exposure than with daptomycin. Thus, the antibacterial effect from the single-dose regimen of oritavancin is as effective as that from either once-daily dosing with daptomycin or twice-daily dosing with vancomycin against the MRSA isolates tested in an in vitro pharmacokinetic/pharmacodynamic model over 72 h. These results provide further justification to assess the single 1,200-mg dose of oritavancin for treatment of acute bacterial skin and skin structure infections.     

Population Pharmacokinetics of Pyronaridine in Pediatric Malaria Patients

Pyramax is a pyronaridine (PYR)-artesunate (PA) combination for the treatment of uncomplicated malaria in adult and pediatric patients. A granule formulation of this combination is being developed for treatment of uncomplicated P. falciparum and P. vivax malaria in pediatric patients. The aims of this study were to describe the pharmacokinetics of PYR using a total of 1,085 blood PYR concentrations available from 349 malaria patients younger than 16 years of age with mild to moderate uncomplicated malaria and to confirm the dosing regimen for the pediatric granule formulation. Nonlinear mixed-effects modeling using NONMEM software was used to obtain the pharmacokinetic and inter- and intraindividual variability parameter estimates. The population pharmacokinetics of PYR were described by a two-compartment model with first-order absorption and elimination. Allometric scaling was implemented to address the effect of body weight on clearance and volume parameters. The final parameter estimates of PYR apparent clearance (CL/F), central volume of distribution (V₂/F), peripheral volume of distribution (V₃/F), intercompartmental clearance (Q/F), and absorption rate constant (K_a) were 377 liters/day, 2,230 liters, 3,230 liters, 804 liters/day and 17.9 day⁻¹, respectively. Covariate model building conducted using forward addition (P < 0.05) followed by backward elimination (P < 0.001) yielded two significant covariate-parameter relationships, i.e., age on V₂/F and formulation on K_a. Evaluation of bootstrapping, visual predictive check, and condition number indicated that the final model displayed satisfactory robustness, predictive power, and stability. Simulations of PYR concentration-time profiles generated from the final model show similar exposures across pediatric weight ranges, supporting the proposed labeling for weight-based dosing of Pyramax granules. (These studies have been registered at ClinicalTrials.gov under registration no. NCT00331136 [phase II study] and NCT00541385, NCT00403260, NCT00422084, and NCT00440999 [phase III studies]. The most recent phase III study was registered at pactr.org under registration no. PACTR201105000286876.)     

Pharmacokinetics of intravenous and oral linezolid in adults with cystic fibrosis

Linezolid is a treatment option for methicillin-resistant Staphylococcus aureus (MRSA) infections in cystic fibrosis (CF) patients. Little is known, however, about its pharmacokinetics in this population. Eight adults with CF were randomized to receive intravenous (i.v.) and oral linezolid at 600 mg twice daily for 9 doses in a crossover design with a 9-day washout. Plasma samples were collected after the first and ninth doses of each phase. Population pharmacokinetic analyses were performed by nonlinear mixed-effects modeling using a previously described 2-compartment model with time-dependent clearance inhibition. Monte Carlo simulation was performed to assess the activities of the linezolid dosing regimens against 42 contemporary MRSA isolates recovered from CF patients. The following pharmacokinetic parameter estimates were observed for the population: absorption rate constant, 1.91 h(-1); clearance, 9.54 liters/h; volume of central compartment, 26.8 liters; volume of peripheral compartment, 17.3 liters; and intercompartmental clearance, 104 liters/h. Linezolid demonstrated nonlinear clearance after 9 doses, which was reduced by a mean of 38.9% (range, 28.8 to 59.9%). Mean bioavailability was 85% (range, 47 to 131%). At steady state, 600 mg given twice daily produced 93.0% and 87.2% probabilities of obtaining the target pharmacodynamic exposure against the MRSA isolates for the i.v. and oral formulations, respectively. Thrice-daily dosing increased the probabilities to 97.0% and 95.6%, respectively. Linezolid pharmacokinetics in these adults with CF were well described by a 2-compartment model with time-dependent clearance inhibition. Standard i.v. and oral dosing regimens should be sufficient to reliably attain pharmacodynamic targets against most MRSA isolates; however, more frequent dosing may be required for isolates with MICs of ≥ 2 μg/ml.     

Single- and multiple-dose pharmacokinetics of genistein capsules in healthy chinese subjects: A phase I, randomized, open-label study

Background: Genistein capsules are currently being developed to treat osteoporosis in China. Genistein is extracted from the fruit of Sophora japonica Leguminosae.Objective: The objective of this study was to assess the pharmacokinetics of genistein capsules after single and multiple oral doses in healthy Chinese subjects.Methods: This was a Phase I, randomized, open-label, single- and multiple- dose study in healthy Chinese adults (aged 19-40 years). In the single-dose study, subjects were randomly assigned in a 1:1:1 ratio to receive genistein 50, 100, or 300 mg (in 50-mg capsules). To assess the effect of food on the pharmacokinetics, subjects in the 50-mg group were equally randomized again into fasting and postprandial (genistein was administered after a high-fat breakfast) groups according to a 2-way cross-over design. A separate equal-sized group of subjects were administered genistein 50 mg on day 1 (single dose), received no treatment on days 2 and 3, and were administered genistein 50 mg QD for 6 days (days 4-9) to obtain a multiple-dose pharmacokinetic profile. Because genistein is converted so rapidly and completely to glucuronidated genistein after administration, plasma concentrations of glucuronidated genistein were determined using a validated high-performance liquid chromatography/ tandem mass spectrometry method. Drug tolerability was assessed by monitoring adverse events (AEs) and laboratory parameters.Results: The study enrolled 40 healthy subjects (24 men, 16 women; 10 each in the 50-, 100-, and 300-mg single-dose groups and 10 in the multiple-dose group). Three subjects voluntarily withdrew (2 in the 100-mg group and 1 in the 300-mg group) before study drug administration. Thirty-seven subjects (24 men, 13 women) completed the study and were included in the analysis. The mean (SD) values of the single-dose genistein 50-, 100-, and 300-mg groups were as follows: T_max, 6.0 (2.4), 7.4 (2.4), and 5.6 (1.2) hours, respectively; t_l/2, 13.0 (4.0), 12.6 (5.8), and 9.4 (1.1) hours; AUC_0−t, 3344 (1635), 8389 (5164), and 9361 (2428) ng/mL · h⁻¹; and C_max , 218.7 (68.6), 435.7 (202.1), and 553.4 (152.8) ng/mL. The plasma glucuronidated genistein concentrations were directly proportional to the administered dose over the range of 50 to 100 mg and increased nonproportionately with the 300-mg dose. No statistically significant differences in pharmacokinetic parameters were found in the fasting group compared with the postprandial group. In the multiple-dose group, the mean (SD) steady-state pharmacokinetic parameters on day 9 were similar to those following a single dose of genistein on day 1 (T_max, 6.0 [1.0] vs 5.9 [1.5] hours, respectively; t_l/2, 9.5 [1.5] vs 9.1 [1.5] hours; AUC_0−t, 2830 [1541] vs 2078 [1308] ng/mL · h⁻¹; C_max, 203.1 [130.9] vs 168.4 [105.7] ng/mL). All AEs were assessed as mild or moderate and resolved without treatment, with the exception of elevated alanine aminotransferase and aspartate aminotransferase activities in one subject that resolved with treatment.Conclusions: The pharmacokinetics of glucuronidated genistein appeared to fit the linear-dose range of genistein 50 to 100 mg, but not the 300-mg dose in these healthy Chinese volunteers. Food consumption did not significantly affect the pharmacokinetic properties. No significant differences were observed in the pharmacokinetic parameters after multiple doses of genistein compared with a single dose, suggesting that the drug did not accumulate after multiple doses.     

Population Pharmacokinetic Study of Amikacin Administered Once or Twice Daily to Febrile, Severely Neutropenic Adults

Once-daily (o.d.) administration of 20 mg of amikacin per kg of body weight to neutropenic patients has been validated by clinical studies, but amikacin pharmacokinetics have been documented only for the 7.5-mg/kg twice-daily (b.i.d.) regimen in this population. In order to determine in neutropenic patients (i) the influence of the dosing regimen on the kinetics of amikacin, (ii) the linearity of kinetics of amikacin in the range of 7.5 to 20 mg/kg, and (iii) the influence of patient characteristics on the disposition of amikacin and (iv) to provide a rationale for dosing recommendations, we evaluated the population pharmacokinetics of amikacin administered to 57 febrile neutropenic adults (neutrophil count, <500/mm³) being treated for a hematological disorder and receiving amikacin at 7.5 mg/kg b.i.d. (n = 29) or 20 mg/kg o.d. (n = 28) and administered intravenously over 0.5 h. A total of 278 blood samples were obtained (1 to 14 samples per patient) during one or several administration intervals (1 to 47). Serum amikacin levels were measured by the enzyme-multiplied immunoassay technique. A mixed-effect modeling approach was used to fit a bicompartmental model to the data (NONMEM software). The influences of the dosing regimen and the demographic and biological indices on the pharmacokinetic parameters of amikacin were evaluated by the maximum-likelihood ratio test on the population model. The dosing regimen had no influence on amikacin pharmacokinetic parameters, i.e., the kinetics of amikacin were linear over the range of 7.5 to 20 mg/kg. Amikacin elimination clearance (CL) was only correlated with creatinine clearance or its covariates, namely, sex, age, body weight, and serum creatinine level. The interindividual variability of CL was 21%, while those of the central volume of distribution, the distribution clearance, and the tissue volume of distribution were 15, 30, and 25%, respectively. On the basis of the expected distribution of amikacin concentrations in this population, dosing recommendations as a function of creatinine clearance (CL_CR) are proposed: for patients with normal renal function (CL_CR of 80 to 130 ml/min), 20 mg/kg o.d. is recommended, whereas for patients with severe renal impairment (CL_CR, 10 to 20 ml/min), a dosage of 17 mg/kg every 48 h is recommended.     

In Vitro Antimalarial Activity of Novel Semisynthetic Nocathiacin I Antibiotics

Presently, the arsenal of antimalarial drugs is limited and needs to be replenished. We evaluated the potential antimalarial activity of two water-soluble derivatives of nocathiacin (BMS461996 and BMS411886) against the asexual blood stages of Plasmodium falciparum. Nocathiacins are a thiazolyl peptide group of antibiotics, are structurally related to thiostrepton, have potent activity against a wide spectrum of multidrug-resistant Gram-positive bacteria, and inhibit protein synthesis. The in vitro growth inhibition assay was done using three laboratory strains of P. falciparum displaying various levels of chloroquine (CQ) susceptibility. Our results indicate that BMS461996 has potent antimalarial activity and inhibits parasite growth with mean 50% inhibitory concentrations (IC₅₀s) of 51.55 nM for P. falciparum 3D7 (CQ susceptible), 85.67 nM for P. falciparum Dd2 (accelerated resistance to multiple drugs [ARMD]), and 99.44 nM for P. falciparum K1 (resistant to CQ, pyrimethamine, and sulfadoxine). Similar results at approximately 7-fold higher IC₅₀s were obtained with BMS411886 than with BMS461996. We also tested the effect of BMS491996 on gametocytes; our results show that at a 20-fold excess of the mean IC₅₀, gametocytes were deformed with a pyknotic nucleus and growth of stage I to IV gametocytes was arrested. This preliminary study shows a significant potential for nocathiacin analogues to be developed as antimalarial drug candidates and to warrant further investigation.