Pharmacokinetics and Bioequivalence Evaluation of 2 Formulations of Tenofovir Alafenamide

The study was conducted to compare the pharmacokinetics and safety profiles of 2 brands of tenofovir alafenamide (TAF) fumarate tablets. This research was a 2-preparation, 2-sequence, 4-period crossover, completely replicated study in 68 healthy Chinese subjects under fasting and fed conditions. The mean values of the area under the concentration-time curve from time 0 to the last time point with blood sample collection (AUC_0-t ), area under the concentration-time curve from time 0 to infinity (AUC_0-∞ ), and maximum concentration (C_max ) for the test and reference products of TAF were 248.5 and 275.7 ng/mL, 148.1 and 157.8 ng • h/mL, and 148.4 and 158.1 ng • h/mL, respectively, under the fasting condition. On the other hand, the mean value of C_max , AUC_0-t , and AUC_0-∞ for the test and reference formulations of TAF were 244.6 and 246.7 ng/mL, 230.4 and 244.9 ng • h/mL, and 233.2 and 246.2 ng • h/mL, respectively, under the fed condition. The 90% confidence intervals for geometric mean ratios of AUC_0-t and AUC_0-∞ of TAF in fasting and fed states were within the bioequivalence acceptance limits when tested using the average-bioequivalence method. The point estimate value for geometric mean ratio of C_max in fasting and fed states (88.4% and 95.5%, respectively) were within the bioequivalence acceptance limits as per the reference-scaled average-bioequivalence method. The safety profiles of the 2 formulations were comparable. Pharmacokinetic analysis demonstrated that the test formulations of TAF exhibited bioequivalence to the reference and were well tolerated by healthy Chinese subjects (Study Registry Identification Number: CTR20190086; CTR20190087).

Microbicide vaginal rings: Technological challenges and clinical development

Vaginal rings (VRs) are flexible, torus-shaped, polymeric devices designed to sustain delivery of pharmaceutical drugs to the vagina for clinical benefit. Following first report in a 1970 patent application, several steroid-releasing VR products have since been marketed for use in hormone replacement therapy and contraception. Since 2002, there has been growing interest in the use of VR technology for delivery of drugs that can reduce the risk of sexual acquisition of human immunodeficiency virus type 1 (HIV-1), the causative agent of acquired immunodeficiency syndrome (AIDS). Although no vaginally-administered product has yet been approved for HIV reduction/prevention, extensive research efforts are continuing and a number of VR devices offering sustained release of so-called 'HIV microbicide' compounds are currently being evaluated in late-stage clinical studies. This review article provides an overview of the published scientific literature within this important field of research, focusing primarily on articles published within peer-reviewed journal publications. Many important aspects of microbicide-releasing VR technology are discussed, with a particular emphasis on the technological, manufacturing and clinical challenges that have emerged in recent years.

Impact on L-carnitine Homeostasis of Short-term Treatment with the Pivalate Prodrug Tenofovir Dipivoxil

Pivalate-generating prodrugs have been suggested to cause clinically significant hypocarnitinaemia. Tenofovir dipivoxil, a novel ester prodrug of tenofovir, can be used for treatment for hepatitis B and HIV infection and it was necessary to evaluate the effect of its treatment on carnitine homeostasis. We sought to investigate the effect of Class 1 drug tenofovir dipivoxil on endogenous L-carnitine level during a 72-hr test in healthy Chinese volunteers and to establish a suitable dose of L-carnitine nutritional supplement for patients who were administered short-term tenofovir dipivoxil tablets for treatment for hepatitis B and herpes simplex virus infection. Tenofovir dipivoxil was administered in one of eight dosing regimens (single dose 150, 300 and 600 mg, multiple dose 300, 450, and 600 mg, multiple dose 450 (600) mg tenofovir dipivoxil and 0.5 g L-carnitine) to gender-balanced groups of 84 healthy Chinese volunteers. Plasma concentrations of L-carnitine were quantified before, during and after treatment. Plasma L-carnitine concentrations fell during tenofovir dipivoxil dosing. The nadir in L-carnitine concentration was dependent on the dose of tenofovir dipivoxil and it decreased from 6.1 ± 0.6 to 4.4 ± 0.8 μg/ml, 6.1 ± 1.8 to 3.3 ± 1.2 μg/ml, 6.2 ± 0.6 to 2.5 ± 0.5 μg/ml for single doses of 150, 300, 600 mg tenofovir dipivoxil tablets and from 6.0 ± 1.4 to 2.1 ± 1.5 μg/ml, 6.2 ± 0.4 to 0.9 ± 0.5 μg/ml for multiple doses of 450, 600 mg tenofovir dipivoxil tablets, respectively. Short-term administration of tenofovir dipivoxil results in hypocarnitinaemia and increased losses of carnitine in resulting of minor adverse events of decreased food appetite, nausea, abdominal distention and muscle weakness.