Single Ascending-Dose Study To Evaluate the Safety, Tolerability, and Pharmacokinetics of Sutezolid in Healthy Adult Subjects.

The primary objective of the study was to evaluate the safety and tolerability of single oral doses of sutezolid tablets administered under fasting conditions in healthy adult subjects. The secondary objective was to determine the pharmacokinetics (PK) of sutezolid and two metabolites, PNU-101603 and PNU-101244. Overall, sutezolid was well tolerated when administered as a 300-mg, 600-mg, 1,200-mg, or 1,800-mg dose in healthy adult subjects under fasting conditions. Maximum concentration (Cmax) of sutezolid, PNU-101603, and PNU-101244 increased in a less-than-proportional manner with an increase in sutezolid dose between 300 mg and 1,800 mg. Total exposure (AUClast [area under the concentration-time curve from time zero to the time of the last quantifiable concentration] and AUCinf [area under the plasma concentration time curve from time zero extrapolated to infinity]) of sutezolid, PNU-101603, and PNU-101244 increased proportionally with an increase in sutezolid dose.

Advancing the Therapeutic Potential of Indoleamides for Tuberculosis.

Indole-2-carboxamide derivatives are inhibitors of MmpL3, the cell wall-associated mycolic acid transporter of Mycobacterium tuberculosis In the present study, we characterized indoleamide effects on bacterial cell morphology and reevaluated pharmacokinetics and in vivo efficacy using an optimized oral formulation. Morphologically, indoleamide-treated M. tuberculosis cells demonstrated significantly higher numbers of dimples near the poles or septum, which may serve as the mechanism of cell death for this bactericidal scaffold. Using the optimized formulation, an expanded-spectrum indoleamide, compound 2, showed significantly improved pharmacokinetic (PK) parameters and in vivo efficacy in mouse infection models. In a comparative study, compound 2 showed superior efficacy over compound 3 (NITD-304) in a high-dose aerosol mouse infection model. Since indoleamides are equally active on drug-resistant M. tuberculosis, these findings demonstrate the therapeutic potential of this novel scaffold for the treatment of both drug-susceptible and drug-resistant tuberculosis.

Toxicity and toxicokinetic assessment of an anti-tubercular drug pretomanid in cynomolgus monkeys.

Pretomanid is a nitroimidazooxazine antimycobacterial drug that was approved in more than 10 countries as part of a three-drug, all oral regimen, consisting of bedaquiline, pretomanid, and linezolid (BPaL) for 6-months treatment of adults with pulmonary extensively drug-resistant tuberculosis (XDR-TB) or with complicated forms of multidrug-resistant tuberculosis (MDR-TB). The toxicological profile of pretomanid was thoroughly evaluated in repeat-dose oral toxicity studies up to 39 weeks long in cynomolgus monkeys. Exposures up to 10-fold higher than in humans at the approved pretomanid dose (200 mg) were achieved in acute studies allowing for characterization of dose-limiting toxicity. Target organs and processes identified in acute and chronic toxicity studies included QT prolongation, nervous system effects, and liver effects (minimal hepatocellular hypertrophy without elevations in liver enzymes). In a 13-week study, no cataracts were present at the end of dosing, but 2 of 12 monkeys had cataracts at the end of a 13-week recovery period. No cataracts related to pretomanid administration were observed in subsequent 13-week or 39-week studies. No male reproductive toxicity was observed in these studies. No-observed-adverse-effect levels (NOAELs) were identified in all studies. Exposures at the NOAELs equaled, or exceeded, human exposure at the approved pretomanid dose with the exception of female monkeys in a 39-week chronic toxicity study. These data support the use of pretomanid as part of the 6-month BPaL regimen for treating XDR-TB and MDR-TB.

Phase 1 Study of the Effects of the Tuberculosis Treatment Pretomanid, Alone and in Combination With Moxifloxacin, on the QTc Interval in Healthy Volunteers.

Tuberculosis (TB) continues to be a serious threat to public health throughout the world. Newer treatments are needed that could offer simplified regimens with activity against both drug-sensitive and drug-resistant bacilli, while optimizing safety. Pretomanid (PA-824), a nitroimidazooxazine compound, is a new drug for the treatment of pulmonary TB that was recently approved in the United States and Europe in the context of a regimen combined with bedaquiline and linezolid. This phase 1 double-blind, randomized, placebo-controlled crossover study specifically examined the effect of single-dose administration of pretomanid 400 or 1000 mg and pretomanid 400 mg plus moxifloxacin 400 mg on the QTc interval in 74 healthy subjects. Subjects were fasting at the time of drug administration. Pretomanid concentrations following single 400- or 1000-mg doses were not associated with any QT interval prolongation of clinical concern. Moxifloxacin did not alter the pharmacokinetics of pretomanid, and the effect of pretomanid 400 mg plus moxifloxacin 400 mg on the individually corrected QT interval was consistent with the effect of moxifloxacin alone. Both drugs were generally well tolerated. Although supratherapeutic exposure of pretomanid relative to the now-recommended dosing with food was not achieved, these findings contribute to the favorable assessment of cardiac safety for pretomanid.

The conduct of in vitro studies to address time-dependent inhibition of drug-metabolizing enzymes: a perspective of the pharmaceutical research and manufacturers of America.

Time-dependent inhibition (TDI) of cytochrome P450 (P450) enzymes caused by new molecular entities (NMEs) is of concern because such compounds can be responsible for clinically relevant drug-drug interactions (DDI). Although the biochemistry underlying mechanism-based inactivation (MBI) of P450 enzymes has been generally understood for several years, significant advances have been made only in the past few years regarding how in vitro time-dependent inhibition data can be used to understand and predict clinical DDI. In this article, a team of scientists from 16 pharmaceutical research organizations that are member companies of the Pharmaceutical Research and Manufacturers of America offer a discussion of the phenomenon of TDI with emphasis on the laboratory methods used in its measurement. Results of an anonymous survey regarding pharmaceutical industry practices and strategies around TDI are reported. Specific topics that still possess a high degree of uncertainty are raised, such as parameter estimates needed to make predictions of DDI magnitude from in vitro inactivation parameters. A description of follow-up mechanistic experiments that can be done to characterize TDI are described. A consensus recommendation regarding common practices to address TDI is included, the salient points of which include the use of a tiered approach wherein abbreviated assays are first used to determine whether NMEs demonstrate TDI or not, followed by more thorough inactivation studies for those that do to define the parameters needed for prediction of DDI.

Role of biotransformation studies in minimizing metabolism-related liabilities in drug discovery.

Metabolism-related liabilities continue to be a major cause of attrition for drug candidates in clinical development. Such problems may arise from the bioactivation of the parent compound to a reactive metabolite capable of modifying biological materials covalently or engaging in redox-cycling reactions leading to the formation of other toxicants. Alternatively, they may result from the formation of a major metabolite with systemic exposure and adverse pharmacological activity. To avert such problems, biotransformation studies are becoming increasingly important in guiding the refinement of a lead series during drug discovery and in characterizing lead candidates prior to clinical evaluation. This article provides an overview of the methods that are used to uncover metabolism-related liabilities in a pre-clinical setting and offers suggestions for reducing such liabilities via the modification of structural features that are used commonly in drug-like molecules.

Effective dosing regimen of 1-aminobenzotriazole for inhibition of antipyrine clearance in rats, dogs, and monkeys.

1-Aminobenzotriazole (ABT) has been extensively used as a nonspecific inhibitor of cytochromes p450 (p450s) in animals for mechanistic studies, and antipyrine (AP) has been used as a probe for hepatic oxidative metabolic capacity determination in vivo. The method of use of ABT has been variable from lab to lab due largely to unknown pharmacokinetics of ABT itself and incomplete information on various p450s inhibited. The oral pharmacokinetic profiles of ABT were generated in rats, dogs, and monkeys in the dose range of 5 to 200 mg/kg. The results showed that after single oral doses of 50 mg/kg in rats, and 20 mg/kg in dogs and monkeys, the plasma concentrations were high and were sustained for over 24 h. In vitro, inhibition of various expressed p450s upon 30-min preincubation with ABT (0-500 micro M) showed that CYP1A2, 2B6, 2C9, 2C19, 2D6, and 3A4 were inhibited in a dose-dependent manner. The intravenous pharmacokinetics of AP also was affected in a dose-dependent manner in all species, treated 2 h earlier with ABT. Thus, the plasma clearance of AP was inhibited by 88% in rats pretreated with 50 mg/kg ABT and 96% in dogs and 83% in monkeys pretreated with 20 mg/kg ABT. Based on these data in rats, dogs, and monkeys, and the established safety profile of ABT in rats dosed up to 100 mg/kg, a pretreatment at 2 h with a single oral dose of ABT at 100 mg/kg in rats (providing 93% inhibition) and 20 mg/kg in dogs and monkeys effectively inhibited the clearance of the probe compound.

Interaction of ritonavir on tissue distribution of a [(14)c]L-valinamide, a potent human immunodeficiency virus-1 protease inhibitor, in rats using quantitative whole-body autoradiography.

N-[(3-fluorophenyl)methyl]glycyl-N-[3-[((3-aminophenyl)sulfonyl)- 2-(aminophenyl)amino]-(1S,2S)-2-hydroxy-1-(phenylmethyl)propyl]- 3-methyl-L-valinamide (DPC 681, DPC(1)) on oral coadministration with ritonavir (RTV) in rats caused a significant increase in systemic exposure to DPC. Following a single oral dose of [(14)C]DPC with and without RTV pretreatment in rats, and subsequent analysis of whole-body sections, prepared at 1 and 7 or 8 h postdose, using whole-body autoradiography showed an increase in radioactivity in tissues (e.g., brain, and testes) upon coadministration. The distribution of radioactivity in the brain parenchyma and ventricles was different, such that the concentration of radioactivity was greater in cerebrospinal fluid (CSF) than in central nervous system. Thus, the use of CSF concentration of the total radioactivity as a surrogate for brain penetration would result in an overestimation. DPC was determined to be metabolized prominently by rCYP3A4. The increased tissue exposure to DPC in rats could largely be attributed to inhibition of CYP3A1/2 by RTV. DPC was also a good substrate for P-glycoprotein (Pgp), with K(m) of 4 microM and V(max) of 13 pmol/min. The Pgp-mediated transport of DPC across Caco-2 cells was readily saturated at >or=10 microM and was inhibited significantly by RTV at 5 to 10 microM. The data above and the reported RTV concentrations suggested that both the Pgp and CYP3A4 inhibition by RTV may play a significant role in enhancing the systemic and tissue exposure to DPC in humans.

Concurrent induction and mechanism-based inactivation of CYP3A4 by an L-valinamide derivative.

DPC 681 (N-[(3-fluorophenyl)methyl]glycyl-N-[3-[((3-aminophenyl) sulfonyl)-2-(aminophenyl)amino]-(1S,2S)-2-hydroxy-1-(phenyl-methyl)propyl]-3-methyl-l-valinamide) is a potent peptide-like human immunodeficiency virus protease inhibitor that was evaluated in phase I clinical trials. In primary cultures of hepatocytes, DPC 681 significantly induced the testosterone 6beta-hydroxylase activity of rat CYP3A, but not human CYP3A4. Western blot analysis, however, demonstrated a 3-fold increase in expression of CYP3A4 protein by 20 microM DPC 681 in primary cultures of human hepatocytes. Subsequent studies showed that DPC 681 was a potent inhibitor of human CYP3A4 (IC50 = 0.039 microM) and rat CYP3A (IC50 = 1.62 microM). Moreover, DPC 681 was a mechanism-based inactivator of CYP3A4 with KI and kinact of 0.24 microM and 0.22 min-1, respectively. Thus, DPC 681 is both a potent inhibitor and a strong inducer of CYP3A4. Induction of CYP3A4 by DPC 681 was masked in vitro by autoinactivation, similar to the protease inhibitor ritonavir. In pharmacokinetic studies in healthy human volunteers and rats, DPC 681 was found to highly autoinduce its metabolism. Human volunteers dosed with DPC 681 at 600 mg twice daily for 14 days had a 75% decrease in the mean area under the concentration-time curve and a more than 3-fold increase in apparent clearance as compared with that on day 1. Because the primary route of DPC 681 clearance is via CYP3A metabolism, the increased clearance observed in clinical studies is due to induction of human CYP3A4 expression.