No abstract available.
Adenine/*analogs & derivatives ; Antiviral Agents/*therapeutic use ; Female ; Hepatitis B virus/*drug effects ; Hepatitis B, Chronic/*drug therapy ; Humans ; Male ; Phosphorous Acids/*therapeutic use

A simple, rapid and sensitive method was developed for the quantification of tenofovir in plasma of Beagle dogs using HPLC-MS/MS analysis. The analytes tenofovir and internal standard (IS) adefovir were separated on a Zorbax SB-C18 column (3.5 microm, 100 mm x 2.1 mm, Agilent, USA) with mobile phase of methanol/water containing 0.3% formic acid using a gradient elution mode at a flow rate of 0.2 mL x min(-1). The plasma sample preparation was a simple deproteinization by the addition of 20% trichloroacetic acid followed by centrifugation. The detection was performed in positive selected reaction monitoring (SRM) mode with an electrospray ionization (ESI) source. The reactions monitored were m/z 288.1-176.2 for tenofovir and m/z 274.1-162.2 for adefovir (IS). Linear detection responses were obtained for tenofovir ranging from 10 to 5 000 ng x mL(-1). The intra- and inter-day precisions (RSD%) was no more than 6.3% with high recovery and good stability for the quantification, indicating the present method was specific, fast, accurate and reliable. The method was successfully applied to the pharmacokinetic study of two tenofovir agents. Tenofovir dipivoxil fumarate (BP0018, test agent) and tenofovir disoproxil fumarate (reference agent) were orally administrated to 8 Beagle dogs according to the 2 x 2 crossover design. Comparing with the reference agent, the longer MRT and t1/2 were obtained in the group of BP0018, while no significant difference was observed in AUC(0-t), AUC(0-infinity), C(max) and t(max) between them, suggesting that tenofovir dipivoxil fumarate was bioequivalent to the tenofovir disoproxil fumarate in Beagle dogs.
Adenine ; administration & dosage ; analogs & derivatives ; blood ; pharmacokinetics ; Administration, Oral ; Animals ; Area Under Curve ; Chromatography, High Pressure Liquid ; Dogs ; Female ; Male ; Organophosphonates ; administration & dosage ; blood ; pharmacokinetics ; Phosphorous Acids ; administration & dosage ; pharmacokinetics ; Reverse Transcriptase Inhibitors ; blood ; Tandem Mass Spectrometry ; Tenofovir

BACKGROUND/AIMS: The efficacy of tenofovir disoproxil fumarate (TDF) for the treatment of chronic hepatitis B (CHB) patients following prior treatment failure with multiple nucleos(t)ide analogues (NAs) is not well defined, especially in Asian populations. In this study we investigated the efficacy and safety of TDF rescue therapy in CHB patients after multiple NA treatment failure. METHODS: The study retrospectively analyzed 52 CHB patients who experienced failure with two or more NAs and who were switched to regimens containing TDF. The efficacy and safety assessments included hepatitis B virus (HBV) DNA undetectability, hepatitis B envelop antigen (HBeAg) seroclearance, alanine transaminase (ALT) normalization and changes in serum creatinine and phosphorus levels. RESULTS: The mean HBV DNA level at baseline was 5.4 +/- 1.76 log10 IU/mL. At a median duration of 34.5 months of TDF treatment, the cumulative probabilities of achieving complete virological response (CVR) were 25.0%, 51.8%, 74.2%, and 96.7% at 6, 12, 24, and 48 months, respectively. HBeAg seroclearance occurred in seven of 48 patients (14.6%). ALT levels were normalized in 27 of 31 patients (87.1%) with elevated ALT at baseline. Lower levels of HBV DNA at baseline were significantly associated with increased CVR rates (p < 0.001). However, CVR rates did not differ between TDF monotherapy or combination therapy with other NAs, and were not affected by mutations associated with resistance to NAs. No significant adverse events were observed. CONCLUSIONS: TDF is an efficient and safe rescue therapy for CHB patients after treatment failure with multiple NAs.
Adenine/adverse effects/*analogs & derivatives/therapeutic use ; Adult ; Aged ; Alanine Transaminase/blood ; Antiviral Agents/adverse effects/*therapeutic use ; Biological Markers/blood ; Creatinine/blood ; DNA, Viral/blood ; Drug Resistance, Viral/genetics ; Drug Substitution ; Female ; Genotype ; Hepatitis B e Antigens/blood ; Hepatitis B virus/*drug effects/genetics/immunology/pathogenicity ; Hepatitis B, Chronic/blood/diagnosis/*drug therapy ; Humans ; Kaplan-Meier Estimate ; Male ; Middle Aged ; Mutation ; Phosphorous Acids/adverse effects/*therapeutic use ; Phosphorus/blood ; Retrospective Studies ; Time Factors ; Treatment Failure ; Viral Load ; Young Adult

Nowadays, available phosphorus (P) deficiency in soil and weed resistance to herbicides have emerged as two severe limiting factors for sustainable agriculture. Therefore, it is of urgent needs to improve plant absorption/utilization ability of the soil P, seek phosphate (Pi)-alternative P fertilizers, and develop new forms of weed control systems. Phosphite (Phi), as a P resource of relatively high amount only less than Pi in Earth, can be converted to utilizable Pi uniquely in some bacterial species by oxidization via its specific dehydrogenase (PTDH), but inhibits plant growth and development. This implies that Phi might rather become a suitable P fertilizer for plants if introducing a PTDH detoxifier from bacteria. Herein, we created the transgenic tobaccos harboring a Pseudomonas PTDH gene (PsPtx) amplified from the soil metagenome previously. RT-PCR showed that the exotic PsPtx gene could express similarly in root, stem and leaf tissues of all transgenic lines. PsPtx transgenic tobaccos could utilize Phi by oxidization as the sole Pi supply, and also outperformed wild-type tobacco with a remarkably dominant growth under Phi stress conditions. Moreover, the PsPtx gene was preliminarily evaluated with a notable quality as a potential candidate of the selection marker in plant genetic transformation. Conclusively, PsPtx and its encoded phosphite dehydrogenase might be applicable for developing a dual system of plant phosphorus utilization and weed control using Phi as P fertilizer and herbicide, and provide an effectual solution to some obstacles in the current crop transgenic studies.
Oxidoreductases ; Phosphites ; Phosphorus ; Plants, Genetically Modified ; Weed Control