Development of a population pharmacokinetic model to characterize the pharmacokinetics of intrathecally administered tominersen in cerebrospinal fluid and plasma.

Tominersen is an intrathecally administered antisense oligonucleotide targeting huntingtin mRNA which leads to a dose-dependent, reversible lowering of cerebrospinal fluid (CSF) mutant huntingtin protein concentration in individuals with Huntington's disease. Nonlinear mixed-effect population pharmacokinetic (PopPK) modeling was conducted to characterize the CSF and plasma pharmacokinetics (PK) of tominersen, and to identify and quantify the covariates that affect tominersen PKs. A total of 750 participants from five clinical studies with a dose range from 10 to 120 mg contributed CSF (n = 6302) and plasma (n = 5454) PK samples. CSF PK was adequately described by a three-compartment model with first-order transfer from CSF to plasma. Plasma PK was adequately described by a three-compartment model with first-order elimination from plasma. Baseline total CSF protein, age, and antidrug antibodies (ADAs) were the significant covariates for CSF clearance. Body weight was a significant covariate for clearances and volumes in plasma. ADAs and sex were significant covariates for plasma clearance. The developed PopPK model was able to describe tominersen PK in plasma and CSF after intrathecal administration across a range of dose levels, and relevant covariate relationships were identified. This model has been applied to guide dose selection for future clinical trials of tominersen in patients with Huntington's disease.

Population-Pharmacokinetic Modeling of Tildrakizumab (MK-3222), an Anti-Interleukin-23-p19 Monoclonal Antibody, in Healthy Volunteers and Subjects with Psoriasis.

BACKGROUND: Tildrakizumab is an anti-interleukin-23p19 monoclonal antibody recently approved for the treatment of chronic plaque psoriasis. METHODS: This analysis characterizes the population pharmacokinetics of subcutaneous tildrakizumab and identifies covariates influencing exposure in 2098 healthy volunteers and subjects with psoriasis. Tested covariates included body weight, formulation type, sex, age, race, serum albumin, creatinine clearance, Japanese origin, prior treatment with a biologic agent, subject status (subjects with psoriasis vs. healthy volunteers), and ethnicity. RESULTS: The pharmacokinetics was described by a one-compartment model with first-order absorption and elimination kinetics, and inter-individual variability on clearance, volume of distribution, and absorption rate constant. The pharmacokinetics was characterized by low clearance and limited volume of distribution. In subjects with psoriasis, the geometric mean clearance (coefficient of variation) was 0.32 L/day (38%), volume of distribution was 10.8 L (24%), and absorption and elimination half-life were 1.5 days (18%) and 23.4 days (23%), respectively, with an absorption lag time of 1.2 h. For the 100-mg dose, steady-state area under the plasma concentration vs. time curve for one dosing interval and maximum plasma concentration were 305 µg*day/mL (41%) and 8.1 µg/mL (34%), respectively. Steady state was achieved by 16 weeks with the clinical regimen (dosing on week 0 and week 4 and every 12 weeks thereafter) with 1.1-fold accumulation in maximum plasma concentration. Healthy subjects had 31% higher bioavailability than subjects with psoriasis. Subjects with increased body weight had a lower area under the plasma concentration-time curve at steady state vs. those with lower body weight. The modeled exposures were contained within clinical comparability bounds for all covariates including body weight. CONCLUSIONS: The pharmacokinetics of tildrakizumab behaves like a typical monoclonal antibody without requiring dosage adjustment. TRIAL REGISTRATION: NCT01729754, NCT01225731, NCT01722331.

Validation of precision-cut liver slices to study drug-induced cholestasis: a transcriptomics approach.

Hepatotoxicity is one of the major reasons for withdrawal of drugs from the market. Therefore, there is a need to screen new drugs for hepatotoxicity in humans at an earlier stage. The aim of this study was to validate human precision-cut liver slices (PCLS) as an ex vivo model to predict drug-induced cholestasis and identify the possible mechanisms of cholestasis-induced toxicity using gene expression profiles. Five hepatotoxicants, which are known to induce cholestasis (alpha-naphthyl isothiocyanate, chlorpromazine, cyclosporine, ethinyl estradiol and methyl testosterone) were used at concentrations inducing low (<30 %) and medium (30-50 %) toxicity, based on ATP content. Human PCLS were incubated with the drugs in the presence of a non-toxic concentration (60 µM) of a bile acid mixture (portal vein concentration and composition) as model for bile acid-induced cholestasis. Regulated genes include bile acid transporters and cholesterol transporters. Pathway analysis revealed that hepatic cholestasis was among the top ten regulated pathways, and signaling pathways such as farnesoid X receptor- and liver X receptor-mediated responses, which are known to play a role in cholestasis, were significantly affected by all cholestatic compounds. Other significantly affected pathways include unfolded protein response and protein ubiquitination implicating the role of endoplasmic reticulum stress. This study shows that human PCLS incubated in the presence of a physiological bile acid mixture correctly reflect the pathways affected in drug-induced cholestasis in the human liver. In the future, this human PCLS model can be used to identify cholestatic adverse drug reactions of new chemical entities.

Maintenance of drug metabolism and transport functions in human precision-cut liver slices during prolonged incubation for 5 days.

Human precision-cut liver slices (hPCLS) are a valuable ex vivo model that can be used in acute toxicity studies. However, a rapid decline in metabolic enzyme activity limits their use in studies that require a prolonged xenobiotic exposure. The aim of the study was to extend the viability and function of hPCLS to 5 days of incubation. hPCLS were incubated in two media developed for long-term culture of hepatocytes, RegeneMed®, and Cellartis®, and in the standard medium WME. Maintenance of phase I and II metabolism was studied both on gene expression as well as functional level using a mixture of CYP isoform-specific substrates. Albumin synthesis, morphological integrity, and glycogen storage was assessed, and gene expression was studied by transcriptomic analysis using microarrays with a focus on genes involved in drug metabolism, transport and toxicity. The data show that hPCLS retain their viability and functionality during 5 days of incubation in Cellartis® medium. Albumin synthesis as well as the activity and gene expression of phase I and II metabolic enzymes did not decline during 120-h incubation in Cellartis® medium, with CYP2C9 activity as the only exception. Glycogen storage and morphological integrity were maintained. Moreover, gene expression changes in hPCLS during incubation were limited and mostly related to cytoskeleton remodeling, fibrosis, and moderate oxidative stress. The expression of genes involved in drug transport, which is an important factor in determining the intracellular xenobiotic exposure, was also unchanged. Therefore, we conclude that hPCLS cultured in Cellartis® medium are a valuable human ex vivo model for toxicological and pharmacological studies that require prolonged xenobiotic exposure.

Classification of Cholestatic and Necrotic Hepatotoxicants Using Transcriptomics on Human Precision-Cut Liver Slices.

Human toxicity screening is an important stage in the development of safe drug candidates. Hepatotoxicity is one of the major reasons for the withdrawal of drugs from the market because the liver is the major organ involved in drug metabolism, and it can generate toxic metabolites. There is a need to screen molecules for drug-induced hepatotoxicity in humans at an earlier stage. Transcriptomics is a technique widely used to screen molecules for toxicity and to unravel toxicity mechanisms. To date, the majority of such studies were performed using animals or animal cells, with concomitant difficulty in interpretation due to species differences, or in human hepatoma cell lines or cultured hepatocytes, suffering from the lack of physiological expression of enzymes and transporters and lack of nonparenchymal cells. The aim of this study was to classify known hepatotoxicants on their phenotype of toxicity in humans using gene expression profiles ex vivo in human precision-cut liver slices (PCLS). Hepatotoxicants known to induce either necrosis (n = 5) or cholestasis (n = 5) were used at concentrations inducing low (<30%) and medium (30-50%) cytotoxicity, based on ATP content. Random forest and support vector machine algorithms were used to classify hepatotoxicants using a leave-one-compound-out cross-validation method. Optimized biomarker sets were compared to derive a consensus list of markers. Classification correctly predicted the toxicity phenotype with an accuracy of 70-80%. The classification is slightly better for the low than for the medium cytotoxicity. The consensus list of markers includes endoplasmic reticulum stress genes, such as C2ORF30, DNAJB9, DNAJC12, SRP72, TMED7, and UBA5, and a sodium/bile acid cotransporter (SLC10A7). This study shows that human PCLS are a useful model to predict the phenotype of drug-induced hepatotoxicity. Additional compounds should be included to confirm the consensus list of markers, which could then be used to develop a biomarker PCR-array for hepatotoxicity screening.

Acute toxicity of CCl4 but not of paracetamol induces a transcriptomic signature of fibrosis in precision-cut liver slices.

In rat in vivo, both paracetamol (APAP) and carbon tetrachloride (CCl4) induce liver necrosis, but long-term treatment with CCl4, in contrast to paracetamol, causes liver fibrosis. The aim of this study was to perform transcriptomic analysis to compare the early changes in mRNA expression profiles induced by APAP and CCl4 in the rat precision-cut liver slice model (PCLS) and to identify early markers that could predict fibrosis-inducing potential. Microarray data of rat PCLS exposed to APAP andCCl4was generated using a toxic dose based on decrease in ATP levels. Toxicity pathway analysis using a custom made fibrosis-related gene list showed fibrosis as one of the predominant toxic endpoints in CCl4-treated, but not in APAP-treated PCLS. Moreover, genes which have a role in fibrosis such as alpha-B crystallin, jun proto-oncogene, mitogen-activated protein kinase 6, serpin peptidase inhibitor and also the transcription factor Kruppel-like-factor-6 were up-regulated by CCl4, but not by APAP. Predicted activation or inhibition of several upstream regulators due to CCl4 is in accordance with their role in fibrosis. In conclusion, transcriptomic analysis of PCLS successfully identified the fibrotic potential of CCl4 as opposed to APAP. The application of PCLS as an ex vivo model to identify early biomarkers to predict the fibrogenic potential of toxic compounds should be further explored.

Development of [18F]-labeled pyrazolo[4,3-e]-1,2,4- triazolo[1,5-c]pyrimidine (SCH442416) analogs for the imaging of cerebral adenosine A2A receptors with positron emission tomography.

Cerebral adenosine A2A receptors (A2ARs) are attractive therapeutic targets for the treatment of neurodegenerative and psychiatric disorders. We developed high affinity and selective compound 8 (SCH442416) analogs as in vivo probes for A2ARs using PET. We observed the A2AR-mediated accumulation of [18F]fluoropropyl ([18F]-10b) and [18F]fluoroethyl ([18F]-10a) derivatives of 8 in the brain. The striatum was clearly visualized in PET and in vitro autoradiography images of control animals and was no longer visible after pretreatment with the A2AR subtype-selective antagonist KW6002. In vitro and in vivo metabolite analyses indicated the presence of hydrophilic (radio)metabolite(s), which are not expected to cross the blood-brain-barrier. [18F]-10b and [18F]-10a showed comparable striatum-to- cerebellum ratios (4.6 at 25 and 37 min post injection, respectively) and reversible binding in rat brains. We concluded that these compounds performed equally well, but their kinetics were slightly different. These molecules are potential tools for mapping cerebral A2ARs with PET.