Metabolism and disposition of lesinurad, a uric acid reabsorption inhibitor, in humans.

The objectives of this study were to determine the absolute bioavailability of lesinurad and to characterized its disposition in humans. The oral bioavailability assessment was performed using a clinical design of simultaneous dosing of a therapeutic oral dose of lesinurad with an intravenous infusion of [14C]lesinurad microdose. The bioavailability of lesinurad was determined to be 100%. The disposition of lesinurad in humans involves hepatic oxidation and renal elimination following administration of oral [14C]lesinurad dose. Metabolism of lesinurad occurred post-systemically with low circulating levels of metabolites <3% of total radioactivity as 74.2% of total radioactivity was attributed to lesinurad. In vitro metabolism studies identified CYP2C9 as the predominant isoform, and summation of metabolites indicated that it was responsible for ∼50% of metabolism.

Discovery of ANA975: an oral prodrug of the TLR-7 agonist isatoribine.

ANA975, a 5-amino-3-beta -D-ribofuranosyl-3H-thiazolo[4,5-d]pyrimidin-2-one derivative, was synthesized in the search of an oral prodrug of isatoribine, a small molecule toll-like receptor 7 (TLR-7) agonist. Several strategies were studied to enable the kilogram-scale synthesis of ANA975. Three general total syntheses are described. In the phase I clinical study of ANA975 against hepatitis C virus (HCV), conversion to isatoribine in plasma was rapid and effective, delivering levels of isatoribine that have been shown to be clinically relevant.

Pharmacokinetic interaction of nelfinavir and methadone in intravenous drug users.

UNLABELLED: The effect of nelfinavir 1250 mg twice daily (b.i.d.) on the pharmacokinetics of methadone was determined in 14 HIV-negative methadone users. DESIGN: The methadone dose (20-140 mg/day) was stabilized and fixed for at least 1 month before nelfinavir (1250 mg b.i.d. for 8 days) was added to the regimen. The concentrations of methadone enantiomers were measured before and during nelfinavir treatment, and the concentrations of nelfinavir and its active metabolite, AG1402, were measured during nelfinavir treatment. Adverse events and withdrawal/intoxication symptoms were monitored throughout the study. RESULTS: Nelfinavir reduced the area under the concentration-time curve of R-methadone, and S-methadone by 43% and 51%, respectively. Nelfinavir and AG1402 concentrations were within the normal range of historical data, and no subject experienced withdrawal symptoms during the study or required dose adjustment during or after the study. CONCLUSIONS: Although nelfinavir reduced the plasma concentrations of both R- and S-methadone, it seems to have no impact on the maintenance dose of methadone. A routine reduction of methadone dose is not recommended when coadministered with nelfinavir.

Isatoribine, an agonist of TLR7, reduces plasma virus concentration in chronic hepatitis C infection.

Immune-based therapy is the mainstay treatment for chronic hepatitis C virus (HCV) infection but causes multiple side effects and achieves durable viral clearance in only approximately 50% of patients. Most new investigational anti-HCV compounds are direct-acting antivirals for which durability of response and risk of viral mutations and resistance are not yet known. Therefore, continuing discovery and development of new immune-based treatments is desirable. Toll-like receptors (TLRs) are pathogen recognition receptors that initiate the innate immune response. The responsiveness of HCV or other ongoing chronic systemic infections to treatment with a selective TLR agonist has not been reported. Isatoribine is a selective agonist of TLR7. In a proof-of-concept study, we found that once-daily 7-day treatment with intravenous isatoribine 800 mg caused a significant (P = .001) reduction of plasma HCV RNA (mean, -0.76; range, -2.85 to +0.21 log(10) units) in otherwise untreated patients (n = 12) who were chronically infected with HCV. Viral load reduction occurred in patients infected with genotype 1 as well as non-genotype 1 HCV. The reduction of viral load was correlated with induction of markers of a heightened immune antiviral state, including 2'-, 5'- oligoadenylate synthetase levels in whole blood. This treatment was well tolerated, with a low frequency of mild to moderate adverse events. In conclusion, systemic administration of the selective TLR7 agonist isatoribine resulted in dose-dependent changes in immunologic biomarkers and a statistically significant antiviral effect with relatively few and mild side effects.

Pharmacokinetic interaction between amprenavir and delavirdine: evidence of induced clearance by amprenavir.

OBJECTIVE: Our objective was to determine the pharmacokinetic interaction between amprenavir and delavirdine. METHODS: Healthy volunteers participated in 2 open-label, 3-period, longitudinal studies. In the first study, 12 volunteers received a single dose of amprenavir, 1200 mg, alone and then again after 7 days of delavirdine, 600 mg twice daily. In the second study, another 12 subjects received amprenavir, 1200 mg twice daily, alone for 7 days. After a 7-day washout period, subjects received delavirdine, 600 mg twice daily, alone for 7 days followed by a combination with amprenavir, 600 mg twice daily, for another 7 days. Amprenavir and delavirdine pharmacokinetics when given alone and in combination were compared. RESULTS: All 12 subjects completed the first study, and 11 subjects completed the second study. Delavirdine significantly increased the area under the curve (AUC) of single-dose amprenavir by 4-fold (P =.0001). Amprenavir, 600 mg twice daily, with delavirdine produced higher levels of amprenavir AUC, minimum concentration (C(min)), and maximum concentration (C(max)), by 30%, 90%, and 18%, respectively, than those of amprenavir, 1200 mg twice daily, alone (P <.05). In contrast, amprenavir decreased delavirdine AUC, C(min), and C(max) by 50%, 70%, and 30%, respectively (P <.005). CONCLUSIONS: Because of the inhibitory effect of delavirdine on the cytochrome P450 3A4-mediated metabolism of amprenavir, the combination of a reduced dose of amprenavir, 600 mg twice daily, with delavirdine resulted in a higher amprenavir exposure than the standard dose of amprenavir, 1200 mg twice daily. However, amprenavir induced the clearance of delavirdine, resulting in a reduction in delavirdine exposure. Further clinical studies are needed to determine the appropriate dosing regimens for delavirdine and amprenavir during coadministration.

Pharmacokinetics and safety of an antirhinoviral agent, ruprintrivir, in healthy volunteers.

A single-dose study and a multiple-dose study of the safety and pharmacokinetics of ruprintrivir, a new selective irreversible inhibitor of human rhinovirus 3C protease, were conducted with healthy adult volunteers. Both studies were double-blind, randomized, placebo-controlled, parallel-group investigations of ruprintrivir administered intranasally at two dose levels. The parent drug and its acid metabolite, AG7185, were measured in plasma samples and nasal washings, and the safety of the treatments was monitored. Intranasal ruprintrivir, administered as single doses of 4 and 8 mg or every 3 h, six times per day, for 7 days was safe and well tolerated. Adverse events were mild, short-lived, and confined to the upper respiratory tract (i.e., nose and throat, taste and smell perceptions). Adverse events were similar after placebo and after single or multiple doses of active drug. Systemic exposure to ruprintrivir was rarely detectable with the highest measured concentration of < or =0.52 ng/ml; the assay had a lower limit of quantification of 0.2 ng/ml. Systemic exposure to the metabolite was also low, with a highest measured concentration of 3.25 ng/ml. Concentrations of AG7185 observed during multiple dosing were higher than those observed after the first dose but were no more than predicted from the single-dose study. Substantial amounts of ruprintrivir were observed intranasally for at least 9 h after multiple doses of ruprintrivir.