Clinical Dosing Regimen Research Articles

Clinical Dosing Regimen of Selinexor Maintains Normal Immune Homeostasis and T Cell Effector Function in Mice: Implications for Combination with Immunotherapy

Selinexor (KPT-330) is a first in class nuclear transport inhibitor of exportin-1(XPO1) currently in advanced clinical trials to treat patients with solid and hematological malignancies. To determine how selinexor might impact anti-tumor immunity, we analyzed immune homeostasis in mice treated with high selinexor doses (15 mg/kg, three times a week: M, W, F) and found disruptions in T cell development, a progressive loss of CD8 T cells and increases in inflammatory monocytes. Antibody production in response to immunization was mostly normal. Precursor populations in bone marrow and thymus were unaffected by high doses of selinexor, suggesting that normal immune homeostasis could recover. We found that high dose of selinexor given once per week preserved nearly normal immune functioning, whereas a lower dose given 3 times per week (7.5 mg/kg, M, W, F) was not able to restore immune homeostasis. Both naïve and effector CD8 T cells cultured in vitro showed impaired activation in the presence of selinexor. These experiments suggest that XPO1 function is required for T cell development and function. We then determined the minimum concentration of selinexor required to block T cell activation, and showed that T cell inhibitory effects of selinexor occur at levels above 100nM, corresponding to the first 24 hours post-oral dosing of 10 mg/kg. In a model of implantable melanoma, we used selinexor treatment at the clinically relevant dosing regimen of 10 mg/kg with a 5-day drug holiday (M, W selinexor treatment). After two weeks of treatment, tumors were harvested and tumor infiltrating leukocyte (TIL) populations were analyzed. This treatment led to intratumoral IFNg+, granzyme B+ cytotoxic CD8 T cells that were comparable to vehicle treated mice. Overall, selinexor treatment leads to transient inhibition of T cell activation but the clinically relevant once and twice weekly dosing schedules that incorporate sufficient drug holidays allow for normal CD8 T cell functioning and development of anti-tumor immunity. These results provide additional support to the recommended selinexor phase 2 dosing regimen, as was determined recently (Razak et al. 2016). DisclosuresKlebanov:Karyopharm Therapeutics: Employment, Equity Ownership. Kashyap:Karyopharm Therapeutics: Employment, Equity Ownership. Shacham:Karyopharm Therapeutics: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Landesman:Karyopharm Therapeutics: Employment, Equity Ownership. Dougan:Karyopharm Therapeutics: Consultancy. Dougan:Karyopharm Therapeutics: Consultancy.

Synergistic killing by meropenem and colistin combination of carbapenem-resistant Acinetobacter baumannii isolates from Chinese patients in an in vitro pharmacokinetic/pharmacodynamic model

Carbapenem-resistant Acinetobacter baumannii (CRAB) is an important clinical threat. Combination therapy that exerts a synergistic effect has become a potential solution to combat CRAB. However, choosing an optimal combination regimen is challenging. A dynamic in vitro pharmacokinetic/pharmacodynamic (PK/PD) model that can simulate the pharmacokinetic profiles of antibiotics provides a powerful tool to compare antibacterial responses to different clinical dosage regimens. In this study, the synergistic effect of the combination of meropenem and colistin was tested in 12 clinical CRAB isolates from Chinese patients using the chequerboard technique. The antibacterial effect was investigated in an in vitro PK/PD diffusion model by simulating different dosage regimens: meropenem monotherapy (0.5 g with 0.5-h infusion or 1 g with 3-h infusion); colistin monotherapy (fixed unbound concentration maintained at 0.25, 0.5 or 1 mg/L); and combination of meropenem and colistin. The chequerboard method showed that the combination of meropenem and colistin had synergistic effects against all 12 isolates, with fractional inhibitory concentration indices (FICIs) of ≤0.5. Moreover, the dynamic in vitro PK/PD model demonstrated that for clinical CRAB isolates with a meropenem MIC of 128 mg/L, the combination (meropenem 1 g with 3-h infusion combined with colistin maintained at 1 mg/L) could achieve 3.8 log10 killing after 24 h, whereas monotherapy was unable to provide such an antibacterial effect. Taken together, these results suggest that the combination of meropenem and colistin might be a promising therapy against CRAB.

In vitro pharmacodynamic evaluation of ceftolozane/tazobactam against β-lactamase-producing Escherichia coli in a hollow-fibre infection model

The proliferation of multidrug-resistant Gram-negative pathogens has been exacerbated by a lack of novel agents in current development by pharmaceutical companies. Ceftolozane/tazobactam was recently approved by the FDA for the treatment of complicated intra-abdominal infections and complicated urinary tract infections. In the present study, the activity of ceftolozane/tazobactam against four isogenic Escherichia coli strains was investigated in a hollow-fibre infection model simulating various clinical dosing regimens. The four investigational E. coli strains included #2805 (no β-lactamase), #2890 (AmpC β-lactamase), #2842 (CMY-10 β-lactamase) and #2807 (CTX-M-15 β-lactamase). Each strain was exposed to regimens simulating 1 g ceftolozane, 2 g ceftolozane, 1 g ceftolozane/0.5 g tazobactam, and 2 g ceftolozane/1 g tazobactam utilising a starting inoculum of ca. 106 CFU/mL. Whereas 1 g of ceftolozane eradicated strains #2805 and #2842 without subsequent regrowth, 1 g ceftolozane/0.5 g tazobactam was required to eradicate strain #2890. For strain #2890, ceftolozane monotherapy led to bacterial growth on plates impregnated with 20 mg/L ceftolozane by 24 h, whilst combination treatment with tazobactam completely suppressed the development of ceftolozane resistance. In contrast, none of the regimens, including 2 g ceftolozane/1 g tazobactam, were able to entirely suppress bacterial growth in strain #2807, with bacterial counts exceeding 108 CFU/mL by 48 h and ceftolozane-resistant populations being amplified after 24 h. Thus, the combination of ceftolozane and tazobactam achieved bactericidal activity followed by sustained killing over 10 days for three of four isogenic E. coli strains. Ceftolozane/tazobactam is a promising new agent to counter multidrug-resistant Gram-negative bacteria.

Dose regimens for Chinese adult liver transplant recipients according to the genetic polymorphisms of CYP2C9, CYP2C19, and CYP3A5 in recipients and donors.

Genetic polymorphisms of the P450 2C9 enzyme (CYP2C9), CYP2C19 and CYP3A5 gene are known to affect the metabolism of many drugs applied in liver transplant recipients, such as warfarin, voriconazole, and tacrolimus. The aim of this study was to recommend dose regimens for the liver recipients based on CYP2C9, CYP2C19, and CYP3A5 genotypic combinations of liver transplant recipients and their donors. 91 adult Han Chinese liver transplant recipients who underwent orthotopic liver transplantation at Tianjin First Central Hospital, China, between 2013 and 2014 were included in this study. CYP2C9*2, CYP2C9*3, CYP2C19* 2, CYP2C19*3 and CYP3A5*3, in both liver recipients and their grafted liver were tested by polymerase chain reaction-restriction fragment length polymorphism. The dose regimens for the liver recipients were recommended based on CYP genotypic combinations of the recipients and their donors. In the liver transplant recipients, the frequencies of CYP2C9*2, CYP2C9*3, CYP2C19*2, CYP2C19*3, and CYP3A5*3 were found to be 2.75%, 4.40%, 0%, 24.18%, and 75.27%, respectively. Allele frequencies were significantly different for CYP2C9*2, CYP2C19*2, and CYP2C19* 3 (p < 0.001) when comparing the recipients with Chinese, Eastern Asians and Caucasians populations. Most dose regimens of drugs, especially of immunosuppressive drugs, should be adjusted according to the variant metabolism activity affected by the genetic polymorphisms in both recipients and their grafted liver. The dose regimens would present considerable intraand inter-patient variability in liver transplant recipients since the genetic polymorphisms of P450 enzyme in their grafted liver might complicate the metabolism of drugs in liver transplant recipients. Giving careful consideration to the CYP genotypic combinations of transplant recipients and donors in clinical dose regimens could optimize outcomes.

Self-Assembly of Janus Oligomers into Onion-like Vesicles with Layer-by-Layer Water Discharging Capability: A Minimalist Model.

A vesicle in a cell is an enclosed structure in which the interior fluid is encompassed by a lipid bilayer. Synthetic vesicles are known as the liposomes. Liposomes with a single phospholipid bilayer are called unilamellar liposomes; otherwise, they are called multilamellar liposomes or onion-like liposomes (vesicles). One prototype synthetic onion-like vesicle, namely, onion-like dendrimersomes, have been recently produced via the self-assembly of amphiphilic Janus dendrimers (Proc. Natl. Acad. Sci. U.S.A. 2016, 113, 1162). Herein, we show computer simulation evidence of another type of onion-like vesicle, namely, onion-like oligomersomes, via the self-assembly of amphiphilic Janus oligomers in water. Specifically, we investigate the minimum-sized oligomers (or minimalist model) that can give rise to the onion-like oligomersomes as well as the composition-dependent phase diagrams. Insights into the formation condition and formation process of the onion-like oligomersomes are obtained. We demonstrate that the discharge of the in-vesicle water is through the remarkable "peeling-one-onion-layer-at-a-time" fashion, a feature that can be utilized for a clinical dosing regimen. The ability to control the formation of onion-like oligomersomes by design can be exploited for applications in drug and gene delivery.

Treatment preferences of patients with early rheumatoid arthritis: a discrete-choice experiment.

To quantify the preferences of patients with early RA (ERA) with the benefits and harms of DMARDs. We assessed patients' preferences using a discrete-choice experiment, an experimentally designed survey to measure trade-offs. Consecutive adult patients with ERA (<2 years since diagnosis) were presented 13 different sets of three treatment options described by eight attributes (clinical outcomes, risks and dosing regimens) and asked to choose one. From patients' responses we estimated the average importance of each attribute and explored preference heterogeneity through latent-class analysis. A total of 152 patients completed the survey (86% response rate): mean age 52 years, 63% female, disease duration 7.8 months. Treatment benefits (increasing the chance of a major symptom improvement and reducing the chance of serious joint damage) were most important. Of potential adverse events, a small risk of serious infections/possible increased risk of cancer was most important. Patients were willing to accept this risk for a 15% absolute increase in the chance of a major symptom improvement. Patients had an aversion to i.v. therapy, but were relatively indifferent to other dosing regimens. Through latent-class analysis, we identified two patient groups: 54% who were more risk averse, particularly to a possible risk of cancer/infection, and others who were highly benefit-driven. On average, patients with ERA were risk tolerant, but important differences in preferences were identified. In particular, a subgroup of patients may prefer to avoid treatments with a possible increased risk of cancer/infection if other effective options are available.

Abstract 4875: Developing tumor-localized, combination immunotherapies

Abstract Building on the recent clinical successes of checkpoint inhibitor antibodies, the field of cancer immunotherapy is now focussing on combination treatment regimens to further improve efficacy benefits to patients. However, combining such systemically dosed agents is associated with a number of challenges including enhanced side effect profiles and high costs. One strategy being explored to overcome such issues is to dose the therapeutics directly into the tumor rather than systemically but many tumors will not be accessible for this type of treatment. We have developed a broadly applicable vector platform system, based on the potent chimeric oncolytic group B adenovirus enadenotucirev (EnAd), for directing the efficient local production of a combination of immunotherapeutic agents selectively within the tumor. The versatility and fidelity of the platform has been exemplified by encoding up to three separate biomolecules in the same virus, including antibodies, cytokines, chemokines and tumor-associated antigens, without altering other virus properties. A systemic clinical dosing regimen has been established for EnAd, with data directly demonstrating selective virus delivery to and protein production from colorectal and other tumor types. The advantage of this approach is that immunotherapeutics encoded in the virus can be produced locally, both in tumors that are not directly injectable and in metastases, while minimising systemic off-target effects. A candidate virus NG-345 has been designed to produce a combination of three secreted immunomodulatory agents (human IFNá, MIP1á and Flt3L) aimed at enhancing the recruitment and activation of immune cells into tumor cell nests. We have shown that NG-345 retains the full oncolytic properties (potency and selectivity) of the parental EnAd virus, with infected human tumor cells producing high levels of all three cytokine/chemokines in the culture supernatants. Functional activity of individual encoded agents has also been demonstrated using relevant cell-based assays. EnAd is highly human-tumor selective and does not replicate, produce infectious progeny or express endogenously regulated transgenes in non-human cells. In vivo evaluation of immuno-modulatory activities of armed viruses is therefore challenging and requires the application of multiple approaches that can collectively provide informative data. In particular, studies are focusing on using surrogate candidate viruses expressing murine gene homologs in human tumor xenografts in immunodeficient mice with or without a reconstituted immune system. Citation Format: Brian R. Champion, Nalini Rasiah, Sam Illingworth, Matthieu Besneux, Rochelle Lear, Darren Plumb, Prithvi Kodialbail, Alice C.N. Brown. Developing tumor-localized, combination immunotherapies. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4875.

Isavuconazole Population Pharmacokinetic Analysis Using Nonparametric Estimation in Patients with Invasive Fungal Disease (Results from the VITAL Study).

Isavuconazonium sulfate (Cresemba; Astellas Pharma Inc.), a water-soluble prodrug of the triazole antifungal agent isavuconazole, is available for the treatment of invasive aspergillosis (IA) and invasive mucormycosis. A population pharmacokinetic (PPK) model was constructed using nonparametric estimation to compare the pharmacokinetic (PK) behaviors of isavuconazole in patients treated in the phase 3 VITAL open-label clinical trial, which evaluated the efficacy and safety of the drug for treatment of renally impaired IA patients and patients with invasive fungal disease (IFD) caused by emerging molds, yeasts, and dimorphic fungi. Covariates examined were body mass index (BMI), weight, race, impact of estimated glomerular filtration rate (eGFR) on clearance (CL), and impact of weight on volume. PK parameters were compared based on IFD type and other patient characteristics. Simulations were performed to describe the MICs covered by the clinical dosing regimen. Concentrations (n = 458) from 136 patients were used to construct a 2-compartment model (first-order absorption compartment and central compartment). Weight-related covariates affected clearance, but eGFR did not. PK parameters and intersubject variability of CL were similar across different IFD groups and populations. Target attainment analyses demonstrated that the clinical dosing regimen would be sufficient for total drug area under the concentration-time curve (AUC)/MIC targets ranging from 50.5 for Aspergillus spp. (up to the CLSI MIC of 0.5 mg/liter) to 270 and 5,053 for Candida albicans (up to MICs of 0.125 and 0.004 mg/liter, respectively) and 312 for non-albicans Candida spp. (up to a MIC of 0.125 mg/liter). The estimations for Candida spp. were exploratory considering that no patients with Candida infections were included in the current analyses. (The VITAL trial is registered at ClinicalTrials.gov under number NCT00634049.)

Cancer-Selective Targeting of the NF-κB Survival Pathway in Multiple Myeloma with the GADD45β/MKK7 Inhibitor, DTP3

The NF-κB transcription factor pathway is aberrantly activated in multiple myeloma (MM) and many other cancers, where it promotes malignancy by upregulating survival genes, thus providing a compelling rationale for therapeutically targeting this pathway in MM. However, despite aggressive efforts to develop a specific NF-κB or IκB kinase (IKK)β inhibitor, no such inhibitor has been approved, due to the preclusive toxicities associated with the general suppression of NF-κB. As a key pathogenetic activity of NF-κB in MM is to block apoptosis through the induction of target genes, an attractive alternative to globally inhibiting NF-κB would be to therapeutically target the non-redundant, cancer-specific downstream effectors of the NF-κB survival pathway.Recently, we identified the interaction between the NF-κB-regulated antiapoptotic factor, GADD45β, and the JNK kinase, MKK7, as a pathogenically critical and cancer cell-restricted survival module downstream of NF-κB and novel therapeutic target in MM. Further, we developed a D-tripeptide inhibitor of the GADD45β/MKK7 complex, DTP3, which effectively kills MM cells by inducing MKK7/JNK-dependent apoptosis and, importantly, is not toxic to normal tissues. Due to this cancer-cell specificity, DTP3 has similar anti-cancer efficacy to bortezomib, but more than 100-fold higher cancer-cell specificity in patient MM cells, ex vivo. DTP3 also displays potent and cancer-selective activity against MM in preclinical animal models, with no apparent side-effects, and far greater therapeutic index than existing treatments. DTP3 further displays synergistic activity with conventional MM therapies, such as bortezomib, suggesting a clinical utility as frontline combination therapy. Additionally, it retains therapeutic efficacy in MM cells that are resistant to most common MM treatments, suggesting further clinical utility.We currently aim to conduct a phase I/IIa clinical trial of DTP3 in MM to deliver clinical Proof of Concept for a cancer-selective NF-κB-targeting strategy as a highly effective novel therapy. This first-in-man study will commence in late 2015.We report here the results from the regulatory pharmacodynamics (PD), safety pharmacology, pharmacokinetic (PK), and toxicology studies.28-day intravenous (i.v.) repeat dose toxicology studies in rat and dog demonstrate that DTP3 is well tolerated, with no significant target organs of toxicity at up to 17 times the optimal exposure in mouse efficacy models. Toxicokinetic (TK) analyses indicate that DTP3 does not accumulate on repeat dosing. Safety pharmacology studies indicate no adverse effect on the central nervous, cardiovascular or respiratory systems. In an Ames assay, DTP3 was not mutagenic.In the rat, i.v. DTP3 rapidly and extensively distributes to tissues, does not pass the blood-brain barrier, and is readily eliminated in urine (30%) and faeces (60%). No major metabolites have been identified.In vitro, DTP3 did not inhibit or induce major human cytochrome P450 isoforms, suggesting no potential for drug interactions via P450. In vitro, DTP3 is neither a substrate for nor inhibitor of P-gp or BCRP, nor is it a substrate or inhibitor of most transporters evaluated. However, DTP3 is a substrate for the uptake transporters, MATE1, MATE2-K and OATP1B3, with some inhibitory potential for MATE1 and MATE2-K at high concentrations.PD studies in a mouse xenograft model show that i.v. bolus injection of at least 10 mg/kg of DTP3 over 2 weeks, daily, every other day, or every 3 days, is highly effective in causing complete tumour regression. The PK and TK evaluation of DTP3 in rat and dog identified long plasma half-lives, modelled into a half-life of 20-24 hr in man. On these bases, we have proposed an initial clinical dosing regimen of DTP3 of three times per week i.v., testing doses from 0.5 to 20 mg/kg. The data also support a subcutaneous route of administration, and an i.v. bolus regimen of twice per week.Collectively, the preclinical package demonstrates the outstanding selective pharmacology and efficacy of DTP3, combined with excellent i.v. tolerability, wide therapeutic window, and favourable PK profile, and supports progression into clinical development.A companion biomarker programme has also been developed in order to inform patient stratification, demonstrate pathway-specific PD activity and proof of mechanism, and so maximise the chance of a positive clinical response. DisclosuresTornatore:Kesios Therapeutics Ltd.: Consultancy, Equity Ownership, Honoraria, Patents & Royalties. Adams:Kesios Therapeutics Ltd.: Consultancy. Kelly:Kesios Therapeutics Ltd.: Consultancy. Ruvo:Kesios Therapeutics Ltd.: Equity Ownership, Patents & Royalties. Oakervee:Celgene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Schey:Celgene Corporation: Honoraria. Apperley:Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; ARIAD: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Franzoso:Kesios Therapeutics Ltd.: Consultancy, Equity Ownership, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties.

Prediction of Drug Clearance and Drug-Drug Interactions in Microscale Cultures of Human Hepatocytes

Accurate prediction of in vivo hepatic drug clearance using in vitro assays is important to properly estimate clinical dosing regimens. Clearance of low-turnover compounds is especially difficult to predict using short-lived suspensions of unpooled primary human hepatocytes (PHHs) and functionally declining PHH monolayers. Micropatterned cocultures (MPCCs) of PHHs and 3T3-J2 fibroblasts have been shown previously to display major liver functions for several weeks in vitro. In this study, we first characterized long-term activities of major cytochrome P450 enzymes in MPCCs created from unpooled cryopreserved PHH donors. MPCCs were then used to predict the clearance of 26 drugs that exhibit a wide range of turnover rates in vivo (0.05-19.5 ml/min per kilogram). MPCCs predicted 73, 92, and 96% of drug clearance values for all tested drugs within 2-fold, 3-fold, and 4-fold of in vivo values, respectively. There was good correlation (R(2) = 0.94, slope = 1.05) of predictions between the two PHH donors. On the other hand, suspension hepatocytes and conventional monolayers created from the same donor had significantly reduced predictive capacity (i.e., 30-50% clearance values within 4-fold of in vivo), and were not able to metabolize several drugs. Finally, we modulated drug clearance in MPCCs by inducing or inhibiting P450s. Rifampin-mediated CYP3A4 induction increased midazolam clearance by 73%, while CYP3A4 inhibition with ritonavir decreased midazolam clearance by 79%. Similarly, quinidine-mediated CYP2D6 inhibition reduced clearance of dextromethorphan and desipramine by 71 and 22%, respectively. In conclusion, MPCCs created using cryopreserved unpooled PHHs can be used for drug clearance predictions and to model drug-drug interactions.

In Vivo Pharmacodynamic Evaluation of an FtsZ Inhibitor, TXA-709, and Its Active Metabolite, TXA-707, in a Murine Neutropenic Thigh Infection Model.

Antibiotics with novel mechanisms of action are urgently needed. Processes of cellular division are attractive targets for new drug development. FtsZ, an integral protein involved in cell cytokinesis, is a representative example. In the present study, the pharmacodynamic (PD) activity of an FtsZ inhibitor, TXA-709, and its active metabolite, TXA-707, was evaluated in the neutropenic murine thigh infection model against 5 Staphylococcus aureus isolates, including both methicillin-susceptible and methicillin-resistant isolates. The pharmacokinetics (PK) of the TXA-707 active metabolite were examined after oral administration of the TXA-709 prodrug at 10, 40, and 160 mg/kg of body weight. The half-life ranged from 3.2 to 4.4 h, and the area under the concentration-time curve (AUC) and maximum concentration of drug in serum (Cmax) were relatively linear over the doses studied. All organisms exhibited an MIC of 1 mg/liter. Dose fractionation demonstrated the area under the concentration-time curve over 24 h in the steady state divided by the MIC (AUC/MIC ratio) to be the PD index most closely linked to efficacy (R(2) = 0.72). Dose-dependent activity was demonstrated against all 5 isolates, and the methicillin-resistance phenotype did not alter the pharmacokinetic/pharmacodynamic (PK/PD) targets. Net stasis was achieved against all isolates and a 1-log10 kill level against 4 isolates. PD targets included total drug 24-h AUC/MIC values of 122 for net stasis and 243 for 1-log10 killing. TXA-709 and TXA-707 are a promising novel antibacterial class and compound for S. aureus infections. These results should prove useful for design of clinical dosing regimen trials.

Computational pharmacokinetics/pharmacodynamics of rifampin in a mouse tuberculosis infection model.

One critical approach to preclinical evaluation of anti-tuberculosis (anti-TB) drugs is the study of correlations between drug exposure and efficacy in animal TB infection models. While such pharmacokinetic/pharmacodynamic (PK/PD) studies are useful for the identification of optimal clinical dosing regimens, they are resource intensive and are not routinely performed. A mathematical model capable of simulating the PK/PD properties of drug therapy for experimental TB offers a way to mitigate some of the practical obstacles to determining the PK/PD index that best correlates with efficacy. Here, we present a preliminary physiologically based PK/PD model of rifampin therapy in a mouse TB infection model. The computational framework integrates whole-body rifampin PKs, cell population dynamics for the host immune response to Mycobacterium tuberculosis infection, drug-bacteria interactions, and a Bayesian method for parameter estimation. As an initial application, we calibrated the model to a set of available rifampin PK/PD data and simulated a separate dose fractionation experiment for bacterial killing kinetics in the lungs of TB-infected mice. The simulation results qualitatively agreed with the experimentally observed PK/PD correlations, including the identification of area under the concentration-time curve as best correlating with efficacy. This single-drug framework is aimed toward extension to multiple anti-TB drugs in order to facilitate development of optimal combination regimens.

Comparative pharmacokinetic and tissue distribution profiles of four major bioactive components in normal and hepatic fibrosis rats after oral administration of Fuzheng Huayu recipe

Fuzheng Huayu recipe (FZHY) is a herbal product for the treatment of liver fibrosis approved by the Chinese State Food and Drug Administration (SFDA), but its pharmacokinetics and tissue distribution had not been investigated. In this study, the liver fibrotic model was induced with intraperitoneal injection of dimethylnitrosamine (DMN), and FZHY was given orally to the model and normal rats. The plasma pharmacokinetics and tissue distribution profiles of four major bioactive components from FZHY were analyzed in the normal and fibrotic rat groups using an ultrahigh performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) method. Results revealed that the bioavailabilities of danshensu (DSS), salvianolic acid B (SAB) and rosmarinic acid (ROS) in liver fibrotic rats increased 1.49, 3.31 and 2.37-fold, respectively, compared to normal rats. There was no obvious difference in the pharmacokinetics of amygdalin (AMY) between the normal and fibrotic rats. The tissue distribution of DSS, SAB, and AMY trended to be mostly in the kidney and lung. The distribution of DSS, SAB, and AMY in liver tissue of the model rats was significantly decreased compared to the normal rats. Significant differences in the pharmacokinetics and tissue distribution profiles of DSS, ROS, SAB and AMY were observed in rats with hepatic fibrosis after oral administration of FZHY. These results provide a meaningful basis for developing a clinical dosage regimen in the treatment of hepatic fibrosis by FZHY.

Overuse of proton pump inhibitors.

Proton pump inhibitors (PPIs) are currently the most effective drugs inhibiting hydrochloric acid secretion. They have replaced histamine type 2 receptor antagonists in the majority of clinical indications, for example, functional dyspepsia, gastroesophageal reflux disease, or drug‑induced upper gastrointestinal tract injury. High prevalence of acid‑related upper gastrointestinal tract diseases, as well as the potency, good tolerance, and acceptable costs of treatment with PPIs have largely increased their use in hospitals and outpatient clinics. At present, PPIs are used more frequently, often long‑term and in high doses, and not necessarily according to the current recommendations. PPI‑induced inhibition of hydrochloric acid secretion causes iatrogenic hypochlorhydria and hypergastrinemia, which may result in parietal cell hypertrophy and enterochromaffin‑like cell hyperplasia, exposing patients to rebound hydrochloric acid hypersecretion. It is believed that this phenomenon may be responsible for failure to discontinue pharmacotherapy with PPIs and to their overuse. As a result, an inappropriate, especially chronic, treatment increases the risk of some side effects as well as individual and institutional expenditures. Therefore, a reasonable approach to clinical indications, dosing, and treatment regimen in each individual patient should be recommended.

Sodium Fusidate Inhibits rCYP3A4 in vitro-A Possible Mechanism Defining the Interaction with Statins

Sodium fusidate (fusidic acid) is an antimicrobial agent used to treat methicillin-resistant Staphylococcus aureus infections. Several case reports have described drug interactions between sodium fusidate and CYP3A4 metabolised statins, leading to statin myotoxicity, including fatal myotoxicity. The mechanism of this interaction is unknown. We investigated the effects of sodium fusidate on recombinant CYP3A4 in vitro and found it to be a timedependent inhibitor of this enzyme at concentrations likely to be achieved with clinical dosing regimens. This finding may help to explain the mechanism of the apparent statin-fusidate interaction.

In vivo pharmacokinetics and pharmacodynamics of the lantibiotic NAI-107 in a neutropenic murine thigh infection model.

NAI-107 is a novel lantibiotic compound with potent in vitro activity against Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). The purpose of this study was to examine the activity of NAI-107 against S. aureus strains, including MRSA, in the neutropenic murine thigh infection model. Serum pharmacokinetics were determined and time-kill studies were performed following administration of single subcutaneous doses of 5, 20, and 80 mg/kg body weight. The dose fractionation included total doses ranging from 1.56 to 400 mg/kg/72 h, divided into 1, 2, 3, or 6 doses. Studies of treatment effects against 9 S. aureus strains (4 methicillin-susceptible Staphylococcus aureus [MSSA] and 5 MRSA) using a 12-h dosing interval and total dose range of 1.56 to 400 mg/kg/72 h were also performed. A maximum effect (Emax) model was used to determine the pharmacokinetic/pharmacodynamic (PK/PD) index that best described the dose-response data and to estimate the doses required to achieve a net bacteriostatic dose (SD) and a 1-log reduction in CFU/thigh. The pharmacokinetic studies demonstrated an area under the concentration-time curve (AUC) range of 26.8 to 276 mg·h/liter and half-lives of 4.2 to 8.2 h. MICs ranged from 0.125 to 0.5 μg/ml. The 2 highest single doses produced more than a 2-log kill and prolonged postantibiotic effects (PAEs) ranging from 36 to >72 h. The dose fractionation-response curves were similar, and the AUC/MIC ratio was the most predictive PD index (AUC/MIC, coefficient of determination [R2]=0.89; maximum concentration of drug in serum [Cmax]/MIC, R2=0.79; time [T]>MIC, R2=0.63). A ≥2-log kill was observed against all 9 S. aureus strains. The total drug 24-h AUC/MIC values associated with stasis and a 1-log kill for the 9 S. aureus strains were 371±130 and 510±227, respectively. NAI-107 demonstrated concentration-dependent killing and prolonged PAEs. The AUC/MIC ratio was the predictive PD index. Extensive killing was observed for S. aureus organisms, independent of the MRSA status. The AUC/MIC target should be useful for the design of clinical dosing regimens.

Impact on resistance of the use of therapeutically equivalent generics: the case of ciprofloxacin.

Therapeutic nonequivalence of generic antibiotics may lead to treatment failure and enrichment of resistance. However, there has been no demonstration that an equivalent generic displays the same resistance selection profile as the innovator drug. We aimed to test this hypothesis with five generic versions of ciprofloxacin by assessing their pharmaceutical equivalence with microbiological assays and their efficacy against Pseudomonas aeruginosa PAO1 in the neutropenic murine thigh infection model. One equivalent generic was selected for analysis by high-pressure liquid chromatography-tandem mass spectrometry (LC-MS/MS), to confirm chemical identity, and resistance selection experiments in a hollow-fiber (HF) system simulating two clinical dosing regimens. Total and resistant populations were measured, and the MICs of the resistant cells with and without an efflux pump inhibitor were determined. LC-MS/MS found no differences between products, and the innovator and the generic selected resistance with the same magnitude and mechanism after 7 days of treatment in the HF system, supporting the fact that a generic with demonstrated equivalence in vivo is also equivalent regarding resistance selection.

Mechanism‐based approach using a biomarker response to evaluate tocilizumab subcutaneous injection in patients with rheumatoid arthritis with an inadequate response to synthetic DMARDs (MATSURI study)

A multicenter, open-label, dose-escalation phase 1/2 study was undertaken to evaluate the optimal subcutaneous tocilizumab dose that would result in exposure comparable to the intravenous tocilizumab 8-mg/kg approved dose in patients with rheumatoid arthritis. A pharmacokinetic and biomarker approach was used to estimate the clinical optimal dose regimen of subcutaneous tocilizumab. Safety and efficacy of subcutaneous tocilizumab were assessed as secondary end points. Patients received subcutaneous tocilizumab at 81 mg every 2 weeks (q2w) (n = 8), 162 mg q2w (n = 12), or 162 mg weekly (qw) (n = 12) for 24 weeks. 88% of 162-mg q2w patients and 100% of 162-mg qw patients maintained mean serum trough tocilizumab concentrations of ≥1 µg/mL, and had exposure comparable with the approved intravenous tocilizumab dose of 8 mg/kg; this resulted in normalized C-reactive protein levels and improvement in ACR20/50/70 responses. The most common adverse events were abnormal laboratory results, which were mild in severity. Anti-tocilizumab antibodies were detected in a few patients in the 81-mg q2w and 162-mg qw groups. In conclusion, coupled with efficacy and tolerability results, the appropriate dose of subcutaneous tocilizumab was determined to be 162 mg q2w for Japanese patients.

Effect of ritonavir-induced cytochrome P450 3A4 inhibition on plasma fentanyl concentrations during patient-controlled epidural labor analgesia: a pharmacokinetic simulation

BackgroundRitonavir inhibition of cytochrome P450 3A4 decreases the elimination clearance of fentanyl by 67%. We used a pharmacokinetic model developed from published data to simulate the effect of sample patient-controlled epidural labor analgesic regimens on plasma fentanyl concentrations in the absence and presence of ritonavir-induced cytochrome P450 3A4 inhibition. MethodsFentanyl absorption from the epidural space was modeled using tanks-in-series delay elements. Systemic fentanyl disposition was described using a three-compartment pharmacokinetic model. Parameters for epidural drug absorption were estimated by fitting the model to reported plasma fentanyl concentrations measured after epidural administration. The validity of the model was assessed by comparing predicted plasma concentrations after epidural administration to published data. The effect of ritonavir was modeled as a 67% decrease in fentanyl elimination clearance. Plasma fentanyl concentrations were simulated for six sample patient-controlled epidural labor analgesic regimens over 24h using ritonavir and control models. Simulated data were analyzed to determine if plasma fentanyl concentrations producing a 50% decrease in minute ventilation (6.1ng/mL) were achieved. ResultsSimulated plasma fentanyl concentrations in the ritonavir group were higher than those in the control group for all sample labor analgesic regimens. Maximum plasma fentanyl concentrations were 1.8ng/mL and 3.4ng/mL for the normal and ritonavir simulations, respectively, and did not reach concentrations associated with 50% decrease in minute ventilation. ConclusionOur model predicts that even with maximal clinical dosing regimens of epidural fentanyl over 24h, ritonavir-induced cytochrome P450 3A4 inhibition is unlikely to produce plasma fentanyl concentrations associated with a decrease in minute ventilation.

Dose-Dependent Pharmacokinetic Profiles of 2′-O-Methyl Phosphorothioate Antisense OligonucleotidesinmdxMice

Antisense-mediated exon skipping is a promising therapeutic approach for Duchenne muscular dystrophy. It aims to restore the dystrophin open reading frame by skipping exons with antisense oligonucleotides (AONs) to allow production of partly functional proteins. The approach is currently tested in phase 3 clinical trials, but dosing and maintenance regimens have not yet been well studied. This study compared pharmacokinetic and pharmacodynamic effects of different 2'-O-methyl phosphorothioate RNA AON dosing and maintenance regimens in the preclinical mdx mouse model. When comparing different dosing regimens over a period of 8 weeks, higher levels of AON, exon skipping, and protein were observed in muscle after low daily doses compared with large weekly doses. Secondly, after receiving a high loading dose (1,250 mg/kg) in the first week, mice treated with maintenance injections twice weekly for 8 weeks showed higher preservation of therapeutic effects than mice receiving less or no maintenance injections. In both cases, the regimen resulting in the highest AON and exon skipping levels in muscle also resulted in high AON levels in liver and kidneys. These studies underline the importance of balancing optimal AON efficacy and tolerable levels in non-target organs, which may be fine-tuned by further optimization of AON treatment regimens.