Lamivudine for chronic hepatitis B

The inhibition mechanism of the uptake of lamivudine via human organic anion transporter 1 by Stellera chamaejasme L. extracts

Stellera chamaejasme L. is a traditional Chinese medicine with a long history to treat stubborn skin ulcer, and it also has antiviral and antitumor effects. Neochamaejasmine B (NCB), Neochamaejasmine A (NCA) and Chamaechromone (CMC) are the major components in dried roots of Stellera chamaejasme L.. Our studies suggested that NCB, NCA and CMC are inhibitors of Organic anion transporter 1 (OAT1). OAT1 is encoded by solute carrier family 22 member 6 gene (SLC22A6) in humans and plays a critical role in the organic anion drug uptake and excretion in the kidney. Lamivudine is the typical substrate of OAT1 and is frequently used in combination with other antiviral drugs in clinical antiviral treatments. The aim of this study is to investigate the interaction and its mechanism between these bi-flavone components in Stellera chamaejasme L. and lamivudine via OAT1 both in vitro and in vivo. In vitro, the uptake studies in Madin-Darby canine kidney (MDCK) cells overexpressing OAT1 suggested that NCB inhibited the uptake of 6-CFL and lamivudine.Similar results were obtained for NCA and CMC. NCB was a noncompetitive and competitive inhibitor interaction with OAT1. IC₅₀ values of NCB, NCA and CMC for inhibiting OAT1-mediated lamivudine transport were 2.46, 8.35 and 0.61 μmol·L^-1, respectively. In vivo, the pharmacokinetic results of lamivudine in rats showed that the mean area under the plasma concentration-time curve (AUC_0-∞) and maximal plasma concentration (C_max) of lamivudine after co-administration is increased 2.94-fold and 1.87-fold, respectively, compared to lamivudine administration alone. The results of interactions between lamivudine and these bi-flavone components in Stellera chamaejasme L. extracts via OAT1 in vivo are consistent with studies in vitro. The inhibition of OAT1-mediated uptake of lamivudine by NCB, NCA and CMC is the possible mechanism for Stellera chamaejasme L. extracts improving the oral bioavailability of lamivudine in rats.

Overview of the Chromatographic and Mass Spectrometry Analytical Methods for Determination of Lamivudine in Biological Fluids

Background:

Lamivudine was approved by Food and Drug Administration of the United States for the treatment of both HIV and HBV infection, which has been widely used as monotherapy or a component of combination therapy in clinics in many countries and nationalities.

Methods:

In this paper, the recent chromatographic and mass spectrometry analytical methods for the determination of lamivudine individually or combination with other drugs simultaneously were presented. These methods were widely applied in pharmacokinetics studies, bioequivalence studies, therapeutic drug monitoring studies, cell and animal experiments.

Conclusion:

The review paper might provide references for determining lamivudine in biological fluids, the intracorporal process of lamivudine, and the clinical practice by monitoring plasma concentration of lamivudine in the future.

Synthesis and in vitro evaluation of novel acyclic and cyclic nucleoside analogs with a thiadiazole ring

The synthesis of six thiadiazole nucleoside analogs is reported: 5-diacetylamino-1,2,4-thiadiazol-3-one (1), 5-amino-2- (tetrahydrofuran-2-yl)-1,2,4-thiadiazol-3-one (2), 5-amino-3-[(2′-hydroxyethoxy)methyl]-1,3,4-thiadiazol-2-one (3), 5-amino-3-(4′-hydroxy-2′-hydroxymethyl-butyl)-1,3,4-thiadiazole-2-thione (4), (R)-5-amino-3-(2′,3′-dihydroxypropyl)-1,3,4-thiadiazole-2-thione (5), and (S)-5-amino-3-(2′,3′-dihydroxypropyl)-1,3,4-thiadiazole-2-thione (6). The synthesis, characterization, and properties of these new synthesized thiadiazole derivatives are discussed. A dimerization of 5-amino-3H-1,3,4-thiadiazole-2-thione (14) by sodium nitrite resulting in di-(5-amino-1,3,4-thiadiazol-2-yl) disulfide (19) is also reported. The preliminary in vitro evaluation of these newly synthesized compounds is discussed.

Efficacy of telbivudine on interruption of hepatitis B virus vertical transmission: a meta-analysis

BACKGROUND AND OBJECTIVES

Hepatitis B virus (HBV) infection is one of the most common infections in the world. Vertical transmission is the main reason for the continued endemic infection rates, at least in Asia. This study aimed to investigate the efficacy of telbivudine on mother-to-child transmission (MTCT) interruption.

METHODS

Studies up to April 2012 were collected by searching Pubmed, EMBASE, the Cochrane Library, EBM Review, WangFang Database and China National Knowledge Infrastructure. Serum hepatitis B surface antigen (HBsAg) and HBV DNA in newborns and infants, maternal HBV DNA negative conversion and alanine trans.aminase (ALT) normalization and adverse events were analyzed.

RESULTS

Seven clinical trials involving 644 pregnant women were included in this meta-analysis. Telbivudine resulted in lower HBsAg and HBV DNA seroprevalence in newborns and infants. When maternal viral load prior to delivery was higher than 103copies/mL, HBsAg or HBV DNA positivity had no statistical difference.

CONCLUSIONS

Telbivudine treatment has efficacy and safety on MTCT interruption during late pregnancy. In addition, we demonstrated benefit of telbivudine for mothers in terms of HBV DNA negative conversion and ALT normalization. Telbivudine treatment at the end of pregnancy should be considered in women with high viral load.

Six-month repeated dose toxicity of orally administered metacavir in rhesus monkeys

OBJECTIVE

To explore the toxicities of metacavir, a novel deoxyguanosine analog with an anti-hepatitis B virus (HBV) potential, in a 6-month repeated dosing in rhesus monkeys.

METHODS

Rhesus monkeys were divided into four groups with eight animals in each group. Metacavir or blank vehicles were given for up to 6-month, and then the animals were euthanized 3 and 6 months later. Biochemical and hematological parameters, general symptoms, ECG, serum antibodies, and tissue pathology were observed and recorded.

RESULTS

No biologically meaningful influences on body weight, body temperature, ocular examination, ECG, and organ weight were observed. The main toxic effects included: obvious gastrointestinal toxicities were observed in metacavir 200 mg/kg group, in which animals experienced vomiting and decrease in food consumption. Along with the increase of dosing times, animals gradually tolerated the drug and all these effects gradually abated. Hematological damages included increased damage of red blood cells, decrease of red blood cell count and hemoglobin levels. Hepatic functions were also damaged at certain levels, including the decreases in total protein, albumin, and glucose and the fatty degeneration in hepatocytes. Mild stenosis and exfoliation of gastric and duodenal mucosa was observed. The mild necrosis and exfoliation of renal tubules epithelia was found 6 months after the start of dosing. All these toxic effects were dose dependent.

CONCLUSION

The main target organs of the toxic effects of metacavir are gastrointestinal tract, liver, blood, and kidneys. The no-observed-adverse-effect-level (NOAEL) of metacavir for rhesus monkey were considered to be 50 mg/kg/day.

New antiviral choice for chronic hepatitis B: tenofovir disoproxil fumarate

Tenofovir disoproxil fumarate (TDF) is an oral prodrug of tenofovir, a novel, acyclic nucleotide analogue with in vitro activity against HIV-1 and HIV-2. TDF is licensed by American Food and Drug Administration (FDA) in 2001 for the treatment of HIV infection. TDF is currently one of the most widely used nucleotide reverse transcriptase inhibitors (NRTIs) for the treatment of HIV infection. Its efficacy, favorable toxicity profile, and convenient dosing have made this drug one of the most popular first-line treatment. Numerous studies have demonstrated the use of TDF in the treatment of HIV infection. It also has been shown to be effective in HIV/HBV coinfected patients and in patients with wild-type and lamivudine-resistant strains. Accumulating evidence suggests that TDF is more potent in suppressing HBV replication. In this review, we summarize the study progress of TDF in treating HBV infection.

Treatment paradigms on hepatitis B e antigen-negative chronic hepatitis B patients

The primary goal of treatment in hepatitis B e antigen (HBeAg)-negative patients with chronic hepatitis B (CHB) is potent and durable suppression of hepatitis B virus (HBV) replication. It results in biochemical and histological remission of CHB and is the prerequisite for the prevention of cirrhosis, its life-threatening complications and hepatocellular carcinoma. Responses that are durable after the cessation of treatment are referred to as sustained virological responses, whereas those persisting under therapy are referred to as treatment-maintained virological responses. Treatment paradigms of sustained virological response in HBeAg-negative CHB are practically restricted to conventional IFN-alpha and pegylated interferons (peg-IFNs), and are limited only to patients with compensated liver disease. Long-lasting maintained virological responses without HBV resistance in HBeAg-negative CHB are achievable by all approved nucleos(t)ide analogues (lamivudine, adefovir and entecavir) in highly variable rates, depending on their potency, rapidity of virological response and genetic barrier to resistance. The maintenance of response under 5 years of adefovir treatment represents the most effective treatment paradigm for HBeAg-negative CHB, whereas such long-term data with entecavir and tenofovir monotherapy may become available in the near future. In patients with lamivudine-resistant HBV mutants, the recommended treatment strategy is to add adefovir at the same time as continuing treatment with lamivudine. There are no treatment paradigms as yet of combination therapy from the very outset with two nucleoside analogues for use in treatment-naive patients.

Patterns of hepatitis B virus infection in Brazilian human immunodeficiency virus infected patients: high prevalence of occult infection and low frequency of lamivudine resistant mutations

Hepatitis B virus (HBV) molecular profiles were determined for 44 patients who were infected with human immunodeficiency virus (HIV) type 1 and had antibodies to the hepatitis B core antigen (anti-HBc), with and without other HBV serological markers. In this population, 70% of the patients were under lamivudine treatment as a component of antiretroviral therapy. HBV DNA was detected in 14 (32%) patients. Eight out of 12 (67%) HBsAg positive samples, 3/10 (30%) anti-HBc only samples, and 3/22 (14%) anti-HBs positive samples were HBV DNA positive. HBV DNA loads, measured by real time polymerase chain reaction, were much higher in the HBsAg positive patients (mean, 2.5 x 10(9) copies/ml) than in the negative ones (HBV occult infection; mean, 2.7 x 10(5) copies/ml). Nine out of the 14 HBV DNA positive patients were under lamivudine treatment. Lamivudine resistant mutations in the polymerase gene were detected in only three patients, all of them belonging to the subgroup of five HBsAg positive, HBV DNA positive patients. A low mean HBV load (2.7 x 10(5) copies/ml) and an absence of lamivudine resistant mutations were observed among the cases of HBV occult infection.

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