Tenofovir, emtricitabine, lamivudine and dolutegravir concentrations in plasma and urine following drug intake cessation in a randomized controlled directly observed pharmacokinetic trial to aid point-of-care testing.

BACKGROUND: Poor adherence to ART and pre-exposure prophylaxis (PrEP) can impact patient and public health. Point-of-care testing (POCT) may aid monitoring and adherence interventions. OBJECTIVES: We report the pharmacokinetics of tenofovir [dosed as tenofovir disoproxil (TDF) and tenofovir alafenamide (TAF)], emtricitabine (FTC), lamivudine (3TC) and dolutegravir (DTG) in plasma and urine following drug cessation to evaluate adherence targets in urine for POCT. METHODS: Subjects were randomized (1:1) to receive DTG/FTC/TAF or DTG/3TC/TDF for 15 days. Plasma and spot urine were collected on Day 15 (0-336 h post final dose). Drug concentrations were quantified using LC-MS, and non-linear mixed-effects models applied to determine drug disposition between matrices and relationship with relevant plasma [dolutegravir protein-adjusted 90% inhibitory concentration (PA-IC90 = 64 ng/mL) and minimum effective concentration (MEC = 324 ng/mL)] and urinary thresholds [tenofovir disoproxil fumarate 1500 ng/mL]. RESULTS: Of 30 individuals enrolled, 29 were included (72% female at birth, 90% Caucasian). Median (range) predicted time to plasma dolutegravir PA-IC90 and MEC were 83.5 (41.0-152) and 49.0 h (23.7-78.9), corresponding to geometric mean (90%) urine concentrations of 5.42 (4.37-6.46) and 27.4 ng/mL (22.1-32.7). Tenofovir in urine reached 1500 ng/mL by 101 h (58.6-205) with an equivalent plasma concentration of 6.20 ng/mL (4.21-8.18). CONCLUSIONS: These data support use of a urinary tenofovir threshold of <1500 ng/mL (tenofovir disoproxil fumarate-based regimens) as a marker of three or more missed doses for a POCT platform. However, due to low dolutegravir concentrations in urine, POCT would be limited to a readout of recent dolutegravir intake (one missed dose).

Novel Mechanism of Decyanation of GDC-0425 by Cytochrome P450.

GDC-0425 [5-((1-ethylpiperidin-4-yl)oxy)-9H-pyrrolo[2,3-b:5,4-c']dipyridine-6-carbonitrile] is an orally bioavailable small-molecule inhibitor of checkpoint kinase 1 that was investigated as a novel cotherapy to potentiate chemotherapeutic drugs, such as gemcitabine. In a radiolabeled absorption, distribution, metabolism, and excretion study in Sprague-Dawley rats, trace-level but long-lived 14C-labeled thiocyanate was observed in circulation. This thiocyanate originated from metabolic decyanation of GDC-0425 and rapid conversion of cyanide to thiocyanate. Excretion studies indicated decyanation was a minor metabolic pathway, but placing 14C at nitrile magnified its observation. Cytochrome P450s catalyzed the oxidative decyanation reaction in vitro when tested with liver microsomes, and in the presence of 18O2, one atom of 18O was incorporated into the decyanated product. To translate this finding to a clinical risk assessment, the total circulating levels of thiocyanate (endogenous plus drug-derived) were measured following repeated administration of GDC-0425 to rats and cynomolgus monkeys. No overt increases were observed with thiocyanate concentrations of 121-154 µM in rats and 71-110 µM in monkeys receiving vehicle and all tested doses of GDC-0425. These findings were consistent with results from the radiolabel rat study where decyanation accounted for conversion of <1% of the administered GDC-0425 and contributed less than 1 µM thiocyanate to systemic levels. Further, in vitro studies showed only trace oxidative decyanation for humans. These data indicated that, although cyanide was metabolically released from GDC-0425 and formed low levels of thiocyanate, this pathway was a minor route of metabolism, and GDC-0425-related increases in systemic thiocyanate were unlikely to pose safety concerns for subjects of clinical studies.

The metabolism and disposition of GSK2140944 in healthy human subjects.

1. GSK2140944 is a novel bacterial topoisomerase inhibitor in development for the treatment of bacterial infections. The metabolism and disposition in healthy human subjects was investigated. 2. Six male subjects received [(14)C] GSK2140944 orally (2000 mg) and as a single 2-hour i.v. infusion (1000 mg). Urinary elimination (59%) was major by the i.v. route, whereas fecal elimination (53%) pre-dominated via the oral route. Accelerator mass spectrometry (AMS) was used for the analysis of plasma and bile samples due to the low level of radioactivity in samples (low specific activity of the doses). Unchanged GSK2140944 was the predominant circulating component (>60% DRM), with the main circulating metabolite M4 formed by oxidation of the triazaacenaphthylene moiety representing 10.8% (considered major) and 8.6% drug-related material by the oral and i.v. route, respectively. Approximately 50% of the oral dose was absorbed and eliminated mainly as unchanged GSK2140944 in urine (∼20% of dose). Elimination via metabolism (∼13% of dose) was relatively minor. The facile oxidation of GSK2140944 to metabolite M4 was believed to be a result of activation by adjacent electron withdrawing groups. 3. This study demonstrates the use of AMS to overcome radioprofiling challenges presented by low specific activity resulted from high doses administration.

Characterization of the Effect of Renal Impairment on Upadacitinib Pharmacokinetics.

Upadacitinib is a novel selective Janus kinase 1 inhibitor developed for treatment of rheumatoid arthritis and other autoimmune diseases. The objective of this study was to assess the pharmacokinetics and safety of a single upadacitinib dose in subjects with normal renal function and in subjects with renal impairment. A total of 24 subjects between the ages of 18 and 75 years were assigned to 1 of 4 renal function groups based on estimated glomerular filtration rate (normal, mild, moderate, severe; N = 6/group). A single 15-mg dose of upadacitinib extended-release formulation was administered under fasting conditions. Serial plasma and urine samples were assayed to evaluate the effect of renal impairment on upadacitinib exposure through regression analysis and analysis of covariance. The primary analysis was the regression analysis of upadacitinib exposures versus estimated glomerular filtration rate. The point estimates for upadacitinib plasma exposure ratios (90% confidence interval [CI]) in subjects with mild, moderate, and severe renal impairment were 1.18 (90%CI, 1.06-1.32), 1.33 (90%CI, 1.11-1.59), and 1.44 (90%CI, 1.14-1.82) for area under the plasma concentration-time curve and 1.06 (90%CI, 0.92-1.23), 1.11 (90%CI, 0.88-1.40), and 1.14 (90%CI, 0.84-1.56) for maximum observed plasma concentration, respectively, relative to subjects with normal renal function based on the regression analysis. The analysis of covariance categorical analysis provided consistent results. Upadacitinib was well tolerated by all subjects, and no safety issues were identified in subjects with renal impairment. Renal impairment has a limited effect on upadacitinib pharmacokinetics. This is in agreement with the known limited role of urinary excretion in upadacitinib elimination. Based on the limited impact on exposure, no dose adjustment is necessary for upadacitinib in subjects with impaired renal function.

Single- and multiple-dose pharmacokinetics of fiduxosin under nonfasting conditions in healthy male subjects.

Selective alpha1a-adrenoreceptor antagonists are effective agents for treatment of benign prostatic hyperplasia, a disorder occurring in middle-aged and elderly males. The objective of this study was to determine the single- and multiple-dose pharmacokinetics of fiduxosin, a novel, selective alpha1a-adrenoreceptor antagonist. This was a Phase I, randomized, double-blind, placebo-controlled, parallel-group, single and multiple oral dose study of fiduxosin. Single daily oral doses of 30, 60, or 90 mg of fiduxosin or placebo were administered to healthy adult male subjects (N = 36; 8 active and 4 placebo per dosing group) on Day 1 and Days 5 to 11 (7 consecutive days) after a high-fat breakfast. Fiduxosin plasma concentration-time profiles for Days 1 and 11 were used to assess fiduxosin pharmacokinetics. Fiduxosin single-dose and steady-state pharmacokinetics were dose independent after oral administration under nonfasting conditions. Steady state was achieved after 4 days of qd dosing. Approximately 28% of the oral dose was eliminated by the fecal route as unchanged drug. Less than 1% of the unchanged drug was recovered in the urine after oral administration.