To study the correlations of genetic variants of telbivudine phosphorylase kinases and telbivudine plasma concentration with creatine kinase elevation in chronic hepatitis B patients who received telbivudine.

An observational study was performed in China chronic hepatitis B patients receiving telbivudine therapy at 600 mg once daily. Plasma concentration was measured 12 h after taking telbivudine using ultra-performance liquid chromatography-tandem mass spectrometry and SNPs located in RRM2B, TK2, and NME4 was detected by MALDI-TOF mass spectrometry. All statistical analyses were performed with R 4.3.1 and all graphs were drawn by Origin 2023b and P value < 0.05 was considered statistically significant.

A total of 140 patients receiving telbivudine therapy were recruited with a median plasma concentration of 952.49 (781.07-1238.98) ng/mL. The value of plasma concentration was proportional to the grade of creatine kinase elevation and the best telbivudine plasma concentration threshold to discriminate the grade 3/4 CK elevation was 1336.61 ng/mL. Multivariate analysis revealed that plasma concentration and rs3826160 were the independent risk factor of telbivudine-induced creatine kinase elevation. Patients with TC and CC genotype in rs3826160 not only had a higher incidence of creatine kinase elevation but also a higher plasma concentration than TT genotype carriers.

Chronic hepatitis B patients with TC and CC genotype in rs3826160 have high telbivudine plasma concentration are at risk of elevated creatine kinase.

Creatine kinase elevation is commonly reported in telbivudine-treated patients. However, little is known about the relationship between this adverse drug reaction and plasma concentration. In this study, a sensitive, rapid and safe quantitative bioanalytical method has been established by using LC-MS/MS for the determination of telbivudine in a clinical study of chronic hepatitis B patients. The assay was linear in a dynamic 10-10,000 ng/mL range (r² > 0.999) and total analysis time was 6 min in this method. The validated method was applied to quantitatively determine plasma concentration in chronic hepatitis B patients during long-term telbivudine treatment. The results revealed that telbivudine concentration in the creatine kinase-elevated group (707.92-2788.78 ng/mL) was significantly higher than those with normal creatine kinase (412.63-1108.32 ng/mL). This method was adapted for therapeutic drug monitoring.

The pharmacokinetics of telbivudine, an L-nucleoside with potent activity against hepatitis B virus, was assessed in 42 healthy Chinese volunteers. Subjects were assigned to receive a single oral dose of 200, 400, or 800 mg telbivudine or repeat doses of 600 mg/d. Telbivudine was absorbed rapidly and exhibited dose-related plasma exposure. After reaching maximum concentration (C(max)) at a median time of 2.0 to 2.5 hours, plasma disposition of the drug was biphasic with a mean terminal half-life ranging from 39.4 to 49.1 hours. Telbivudine accumulated slightly after repeat doses, and steady state was reached after 5 to 6 consecutive doses of 600 mg/d. The mean steady-state C(max) and area under the plasma concentration-time curve over the dosing interval of telbivudine 600 mg were 3.7 microg/mL and 26.1 microg x h/mL, respectively. Cumulative urinary excretion of telbivudine over 32 hours represented 24.4% of the administered dose, with a mean renal clearance of 6.6 L/h. Telbivudine was well tolerated in the studied dose range in healthy Chinese subjects, with no pattern of dose-related clinical or laboratory adverse events.

Interferon alpha has restricted efficacy in as much as only a proportion of patients show a response. However, in appropriately selected HBeAg-positive and HBeAg-negative patients, sustained suppression of viral replication can be achieved, and HBeAg or even HBsAg seroconversion can be attained. Thus, finite course of interferon alpha can be successful, and offer an advantage to patient. Interferon (IFN) remains a benchmark therapy for chronic hepatitis B. The main advantages of IFN-α over nucleoside analogues are the absence of resistance and the possibility of immune-mediated clearance of hepatitis B. Unfortunately, side effects preclude the use of interferon alpha in substantial proportions of patients, and prolonged maintenance therapy to suppress hepatitis B virus (HBV) is not feasible. Nucleoside analogues are given by mouth, once per day, and the safety, potency and efficacy have improved and facilitated treatment. However, maintenance of long-term suppression is required for the majority of patients. In general, treatment of chronic hepatitis B should target patients with active disease and viral replication, preferably before the signs and symptoms of cirrhosis or significant injury has occurred. Current EASL guidelines suggest that treatment be based on the evaluation of three criteria: Serum aminotransferase levels, serum HBV DNA levels and histological grade and stage. Many questions remain unanswered on the optimal treatment of patients with chronic hepatitis B with a nucleoside vs interferon alpha. Both forms of treatment have benefits and the choice should be selected and tailored. Stopping or futility rules can be implemented in patients who fail interferon. Recent data suggest the safety and efficacy of nucleoside analogues in the third trimester of pregnancy to reduce the risk of transmission from mothers to their children.

Successful treatment of chronic hepatitis B (CHB) often requires long-term oral nucleoside/nucleotide agents which can be associated with viral resistance, patient non-compliance and adverse effects. Telbivudine is one of the more potent options available, with a 6.5- to 6.6-log copies/ml hepatitis B DNA reduction at 12 weeks in an early viral kinetic study, a potency comparable to entecavir. It is also one of the few drugs in the treatment of CHB under FDA pregnancy Category B.

The efficacy and safety profile of telbivudine in compensated and decompensated CHB patients compared to other agents are discussed. Viral resistance, characteristic adverse effects including elevation in creatine kinase and peripheral neuropathy in telbivudine treatment are reviewed. Infrequent but significant adverse effects of other nucleoside/nucleotide analogs are highlighted.

Readers are provided the latest update on the clinical profile of long-term use of telbivudine.

Long-term telbivudine treatment offers effective viral suppression to CHB patients with certain baseline characteristics and on-treatment virologic response. Creatine kinase elevation is not a good predictor of muscle-related adverse effects with nucleoside/nucleotide analogs. But significant myopathy and neuropathy have been reported in a small number of patients receiving telbivudine.

Telbivudine (Sebivo®; Tyzeka®) is a synthetic nucleoside analogue that inhibits replication of hepatitis B virus (HBV). It is used in the treatment of adults with chronic hepatitis B (CHB) with evidence of viral replication and persistently elevated serum ALT and/or AST levels, and/or histological evidence of active disease. Telbivudine is a potent antiviral that provides effective and sustained viral suppression in patients with compensated CHB. In clinical trials, treatment outcomes were improved significantly more with telbivudine 600 mg once daily than with lamivudine 100 mg or adefovir 10 mg once daily, and telbivudine-treated patients had significantly less viral resistance than lamivudine-treated patients. Increasing rates of hepatitis B e antigen (HBeAg) seroconversion were achieved in HBeAg-positive patients during periods of up to 4 years continuous telbivudine treatment, and seroconversion was durable in most patients throughout a 2-year, off-treatment follow-up, indicating the potential for a finite treatment period in this group of patients. Telbivudine is associated with a medium genetic barrier to resistance and, as patients with undetectable HBV DNA levels have significantly improved outcomes, it is recommended that HBV DNA levels are monitored at week 24 (and 6 monthly thereafter), with the addition of a nucleoside/nucleotide analogue without cross resistance (such as adefovir dipivoxil) if viraemia is present to reduce the risk of resistance (Roadmap concept). Telbivudine was generally well tolerated in clinical trials for periods of up to 4 years, and has a similar tolerability profile to that of lamivudine. A minority of telbivudine-treated patients experience creatinine kinase elevation, usually transient, and myopathy occurs rarely. In modelled cost effectiveness studies in several Asian countries, treatment with telbivudine Roadmap was cost effective in HBeAg-positive patients. Thus, telbivudine provides a valuable treatment option in CHB, particularly when administered using the Roadmap concept in HbeAg-positive patients.

Approximately 350 million persons worldwide are chronically infected with hepatitis B, which can result in cirrhosis, liver failure, and hepatocellular carcinoma. Currently, 2 interferons and 5 nucleos(t)ide analogues have been approved for the treatment of chronic hepatitis B (CHB). This article discusses the mechanisms of action, pharmacokinetics, optimal dose, clinical efficacy, and side effects of medications used for the treatment of CHB.

Telbivudine is an orally bioavailable L-nucleoside with potent and specific anti-hepatitis B virus activity. The higher rate of hepatitis B e antigen (HBeAg) seroconversion during telbivudine treatment than other potent anti-HBV agents suggests a potential immunomodulatory effect. We sought to determine the effects of telbivudine on the immune system, particularly on cytokine production and T-cell response, using an animal model with mouse hepatitis virus strain 3 (MHV-3)-induced hepatitis. The effects of telbivudine on virus replication and cytokine production were investigated in vitro using MHV-3-infected macrophages, and the effects on T-cell response were investigated in vivo in an MHV-3-induced viral hepatitis model. Telbivudine had no effect on MHV-3 replication in macrophages. However, the production of tumour necrosis factor-alpha and interleukin-12 was increased significantly in MHV-3-induced macrophages treated with telbivudine. In vivo survival was enhanced in telbivudine-treated mice, with marked normalization in clinical conditions and histological lesions. Serum levels of interferon-gamma were elevated significantly after telbivudine treatment in MHV-3-infected C3H mice. In contrast, serum interleukin-4 levels were decreased significantly. Furthermore, telbivudine treatment enhanced the ability of T cells to undergo proliferation and secrete cytokines but did not affect cytotoxicity of infected hepatocytes. Of note, we found that telbivudine treatment suppressed programmed death ligand 1 expression on T cells. The results demonstrate the immunomodulatory properties of telbivudine, independent of its antiviral activity, in a mouse model of MHV-3-induced hepatitis.

The effect of telbivudine on cardiac repolarization was evaluated in healthy participants at clinical and supratherapeutic doses. Sixty-two participants were enrolled, stratified by sex, and randomized according to a crossover design among 4 treatment sequences: placebo, a single moxifloxacin 400-mg dose as positive calibrator, and telbivudine 600 and 1800 mg/d for 7 days. Intensive time-matched electrocardiogram measurements and pharmacokinetic sampling were performed at baseline and on day 7 over 24 hours. For telbivudine and moxifloxacin, time-matched, placebo-adjusted change from baseline in QT was calculated and corrected using Fridericia's formula (QTcF). While moxifloxacin produced the expected significant changes in QTcF, none of the changes in QTcF for either doses of telbivudine exceeded 5 ms, and none of the associated upper 1-sided 95% confidence intervals (CI) exceeded the limit of 10 ms. There was no increase in QTcF with increasing plasma telbivudine. The supratherapeutic dose of telbivudine was well tolerated with a safety profile similar to the clinical dose despite a 3-fold increase in plasma exposure. This study therefore met the criteria for a negative thorough QT study. Telbivudine had no adverse effect on cardiac repolarization in healthy participants, even at supratherapeutic exposure, suggesting a broad safety margin.

Telbivudine is a new nucleoside analog indicated for the treatment of chronic hepatitis B infection. A population pharmacokinetic model was developed based on data pooled from 16 early phase studies in 363 healthy participants and patients. Telbivudine was administered as single and/or multiple doses of 25 to 1800 mg daily for up to 28 days. A 2-compartment model with first-order input and lag time provided the best fit to the data. A final model was built with identified covariates, including creatinine clearance on plasma clearance, dose and race on bioavailability fraction, and body weight on central volume of distribution. The final model was applied to simulate steady-state exposure for patients with impaired renal function for various dosing regimens. Results from these simulation analyses support that in patients with moderate to severe renal impairment or end-stage renal disease, reduced daily doses of telbivudine could be an alternative to interval adjustment to achieve exposure comparable to patients with normal renal function or mild renal impairment treated with the full clinical dose.

The treatment of chronic hepatitis B virus (HBV) infection has been revolutionized in the past decade by the increased availability of effective antiviral agents. Telbivudine is an L-nucleoside that is structurally related to lamivudine and has recently been approved for use in patients with chronic HBV infection. Telbivudine is highly selective for HBV DNA and inhibits viral DNA synthesis with no effect on human DNA or other viruses. This article reviews the pharmacology, pharmacokinetics, therapeutic efficacy and safety of telbivudine, and discusses its place in the current armamentarium against HBV.

Relevant publications were identified from searches of Medline and PubMed between 2000 and 2008, using the search terms "hepatitis B/HBV," "telbivudine/LdT," "beta-L-thymidine," "pharmacokinetics," "safety," "adverse events," and "resistance." The reference lists of retrieved articles were searched for relevant studies.

Phase 3 clinical studies demonstrate that telbivudine is superior to lamivudine over a 2-year period in hepatitis B e-antigen (HBeAg)-positive and HBeAg-negative patients. Telbivudine was associated with a statistically significantly greater reduction in HBV DNA, greater proportion of alanine aminotransferase normalization, and greater histological response than lamivudine. Furthermore, telbivudine use resulted in fewer cases of treatment failure and less virological resistance than lamivudine. However, after 2 years of therapy, telbivudine resistance was appreciable (25%) and considerably higher than that seen with other new antivirals such as tenofovir and entecavir. Overall, telbivudine was found to be safe, although grade 3 or 4 adverse events, including elevations in creatine kinase, were more commonly found in patients receiving telbivudine than lamivudine. Telbivudine is not active against lamivudine-resistant HBV.

Telbivudine is a new antiviral agent joining the armamentarium against HBV. It is superior to lamivudine in terms of therapeutic response and resistance profile. However, concerns about resistance with long-term use, along with inferior cost-effective analyses, have relegated telbivudine to a second-line agent in the management of chronic HBV infection.

In recent years, marked progress has been made in the treatment of chronic hepatitis B. Several agents have been approved: interferon alpha-(IFN), pegylated interferon alpha2a (PEG-IFN alpha2a), lamivudine, adefovir, entecavir, telbivudine and recently, tenofovir. Each drug has advantages and limitations. IFN and PEG-IFN alpha2a have the advantage of inducing a sustained virologic response after a defined, limited course of treatment. However, these drugs are only effective in a minority of patients and have frequent side effects. Analogues have the advantage of being administered orally, with good safety profiles and a potent antiviral effect. However, these drugs need to be administered indefinitely since withdrawal of therapy is generally associated with reactivation, and a sustained response is uncommon except in HBeAg positive patients who develop HBe seroconversion. In case of HBe seroconversion, therapy should usually be continued for at least another 24 weeks. The efficacy of lamivudine is limited by the emergence of lamivudine-resistant HBV. Adefovir is associated with a moderate incidence of resistance but its antiviral effect is not optimal. Entecavir has shown to be more effective with a favourable safety profile and a low incidence of resistance. Telbivudine is more potent and has a lower rate of resistance than lamivudine but the resistance rate is significantly higher than other approved drugs. Tenofovir has a potent antiviral effect with a good resistance profile. The future of chronic hepatitis B therapy appears to be different drug combinations. Normally the advantage of drug combinations versus monotherapy should be additive or synergistic antiviral effects and a decrease in viral resistance. Unfortunately, there are few data available and none of the evaluated analogue combinations have been shown to be better than monotherapy. The only combination which has shown a synergistic effect is of pegylated interferon alpha2a with lamivudine. Therefore, combinations of pegylated interferon with the most potent analogues need to be evaluated. The ultimate goal of therapy is HBsAg seroconversion which is more often observed with interferon. Indeed, quantification of serum HBsAg will be a useful tool to predict the treatment outcome. More potent drugs and new combinations as well as understanding the mechanisms of viral resistance should be evaluated to improve the efficacy of treatment.

Forty years ago in 1967, Professor Blumberg discovered the Australian Antigen, later known as the hepatitis B surface antigen, and was awarded the Nobel Prize. This discovery enables the diagnosis of hepatitis B virus (HBV) infection and defines its epidemiology. Viral hepatitis B infection affects global health situation, and chronic hepatitis B (CHB) is particularly serious in the Asia-Pacific region. HBV vaccines created the first breakthrough in HBV prevention. Through universal HBV vaccination program for the newborns, promoted since the mid-1980s, the main route that perpetuates chronic infection from mother to child is curbed. Most children and young adults now have immunity against HBV infection. The next breakthrough comes with therapy for CHB. This prevents progression to cirrhosis and hepatocellular carcinoma. Standard interferon therapy with modest efficacy has been largely replaced by therapy with nuclos(t)ide analogues or pegylated interferons alfa-2a and -2b. Lamivudine was approved by the FDA USA in 1998, followed by adefovir dipivoxil in 2002, entecavir in 2005, and telbivudine in 2006. Clevudine, tenofovir, and many promising candidates are in different stages of development and clinical trial. This paper critically reviews recent data published or presented since the APASL Consensus and Guideline Update of 2005. Clinical efficacy mostly in patients with raised serum alanine aminotransferase will be analyzed.

Three hundred and fifty million people worldwide are estimated to be chronically infected with hepatitis B virus. 15%-40% of these subjects will develop cirrhosis, liver failure or hepatocellular carcinoma during their life. The treatment of chronic hepatitis B has improved dramatically over the last decade merits to the advent of nucleoside/nucleotide analogues and the use of pegylated interferons. Approved drugs for chronic hepatitis B treatment include: standard interferon-alpha 2b, pegylated interferon-alpha 2a, lamivudine, adefovir dipivoxil, and entecavir. Unfortunately, these agents are not effective in all patients and are associated with distinct side effects. Interferons have numerous side effects and nucleoside or nucleotide analogues, which are well tolerated, need to be used for prolonged periods, even indefinitely. However, prolonged treatment with nucleoside or nucleotide analogues is associated with a high rate of resistance. Telbivudine is a novel, orally administered nucleoside analogue for use in the treatment of chronic hepatitis B. In contrast to other nucleoside analogues, Telbivudine has not been associated with inhibition of mammalian DNA polymerase with mitochondrial toxicity. Telbivudine has demonstrated potent activity against hepatitis B with a significantly higher rate of response and superior viral suppression compared with lamivudine, the standard treatment. Telbivudine has been generally well tolerated, with a low adverse effect profile, and at its effective dose, no dose-limiting toxicity has been observed. Telbivudine is one of the most potent antiviral agents for chronic hepatitis B virus and was approved by the FDA in late 2006.

Telbivudine, a l-nucleoside enantiomer, is a potent specific inhibitor of hepatitis B virus (HBV) polymerase. It recently completed Phase III trials and has been licensed in most countries worldwide. It has shown superior efficacy compared with lamivudine in therapeutic response, reduction in HBV DNA, proportion of patients with undetectable HBV DNA, reduced primary treatment failure and reduced viral resistance over 2 years, in Hepatitis B e antigen-positive and -negative patients. Further studies show that switching to telbivudine in lamivudine-suboptimal responders improves the reduction in HBV DNA at week 24 and shows superiority compared with adefovir in reduction of HBV DNA at week 24. Multivariate analysis showed that week 24 HBV DNA best predicted outcomes at 2 years and a 'hepatitis B roadmap' concept has been proposed to manage patients based on this. Thus, telbivudine is a useful addition to the current landscape of hepatitis B therapeutic agents.

Chronic hepatitis B and its life-threatening sequelae are highly prevalent in China. There is a need for effective new therapies to suppress hepatitis B virus (HBV) replication and ameliorate liver disease. In this study, we compared the efficacy of telbivudine, a nucleoside analogue, with lamivudine in Chinese patients. In this phase III, double-blind, multicenter trial conducted in China, 332 patients with compensated hepatitis B e antigen (HBeAg)-positive or HBeAg-negative chronic hepatitis B were randomly assigned to treatment with 600 mg of telbivudine or 100 mg of lamivudine daily for 104 weeks. The primary efficacy endpoint was reduction in serum HBV DNA levels at week 52 of treatment. Secondary endpoints included clearance of HBV DNA to undetectable levels, HBeAg loss and seroconversion, therapeutic response, and alanine aminotransferase (ALT) normalization. Viral resistance and safety were assessed. At week 52, among 290 HBeAg-positive patients, mean reductions of serum HBV DNA were significantly greater in telbivudine recipients than lamivudine recipients (6.3 log(10) versus 5.5 log(10), P < 0.001), and HBV DNA was polymerase chain reaction-negative in significantly more telbivudine recipients than lamivudine recipients (67% versus 38%, P < 0.001). ALT normalization (87% versus 75%, P = 0.007), therapeutic response (85% versus 62%, P = 0.001), and HBeAg loss (31% versus 20%, P = 0.047) were also significantly more common in the telbivudine group. Treatment effects showed similar patterns in the smaller HBeAg-negative group (n = 42). Viral resistance in telbivudine recipients was approximately half that observed with lamivudine; however, this difference was not statistically significant. Clinical adverse events were similar in the two treatment groups.

In Chinese patients with chronic hepatitis B, telbivudine treatment for 52 weeks provided greater antiviral and clinical efficacy than lamivudine, with less resistance.

Treatment of chronic hepatitis B with oral nucleos(t)ide analogs is evolving rapidly with newer compounds gaining approval. Recently, the US FDA and European Medicines Agency (EMEA) have approved telbivudine, a potent anti-hepatitis B virus (HBV)-specific agent with a hitherto excellent safety profile. This review focuses on the efficacy of this agent in chronic hepatitis B compared with lamivudine, evaluated clinically in Phase II and a large Phase III study. Monitoring of the virologic response under treatment with sensitive HBV-DNA assays has been applied, aiming at increasing efficacy and reducing HBV resistance. The results are critically presented and the evolving concept of effective long-term telbivudine and other nucleos(t)ide analog therapy, predicted by the extent of suppression of HBV replication at week 24, are analyzed and discussed.

Telbivudine, the unmodified L-enantiomer of the naturally occurring nucleoside D-thymidine, is a potent synthetic nucleoside analogue. It acts as a hepatitis B virus (HBV) polymerase inhibitor and preferentially inhibits HBV second strand (DNA-dependent) compared with first strand (RNA-dependent) DNA synthesis. More telbivudine than lamivudine recipients with hepatitis B e antigen (HBeAg)-positive chronic hepatitis B and similar proportions of telbivudine or lamivudine recipients with HBeAg-negative disease achieved a therapeutic response at 52 weeks in the large 2-year GLOBE trial. In a phase III trial in Chinese patients, greater reductions in serum HBV DNA occurred with telbivudine than lamivudine at 52 weeks. Reductions in serum HBV DNA at 24 weeks were greater with telbivudine than adefovir in the 1-year switching trial. A lower residual viral load at 52 weeks was seen in patients who received telbivudine or who switched from adefovir to telbivudine at 24 weeks than in patients receiving adefovir. In the 1-year lamivudine switching trial in patients with serum HBV DNA levels >3 log10 copies/mL despite having received prior treatment with lamivudine for a mean of [almost equal or equal to]7 months, those randomised to telbivudine therapy achieved greater reductions in serum HBV DNA levels at 24 weeks than patients randomised to continue lamivudine therapy. Telbivudine was generally well tolerated and most adverse events were of mild or moderate severity. The incidence of severe ALT flares with telbivudine was half that seen with lamivudine at both 52 and 104 weeks in the GLOBE trial.

Three hundred and fifty million people worldwide are estimated to be chronically infected with hepatitis B virus. 15%-40% of these subjects will develop cirrhosis, liver failure or hepatocellular carcinoma during their life. The treatment of chronic hepatitis B has improved dramatically over the last decade merits to the advent of nucleoside/nucleotide analogues and the use of pegylated interferons. Approved drugs for chronic hepatitis B treatment include: standard interferon-alpha 2b, pegylated interferon-alpha 2a, lamivudine, adefovir dipivoxil, and entecavir. Unfortunately, these agents are not effective in all patients and are associated with distinct side effects. Interferons have numerous side effects and nucleoside or nucleotide analogues, which are well tolerated, need to be used for prolonged periods, even indefinitely. However, prolonged treatment with nucleoside or nucleotide analogues is associated with a high rate of resistance. Telbivudine is a novel, orally administered nucleoside analogue for use in the treatment of chronic hepatitis B. In contrast to other nucleoside analogues, Telbivudine has not been associated with inhibition of mammalian DNA polymerase with mitochondrial toxicity. Telbivudine has demonstrated potent activity against hepatitis B with a significantly higher rate of response and superior viral suppression compared with lamivudine, the standard treatment. Telbivudine has been generally well tolerated, with a low adverse effect profile, and at its effective dose, no dose-limiting toxicity has been observed. Telbivudine is one of the most potent antiviral agents for chronic hepatitis B virus and was approved by the FDA in late 2006.

This study evaluates the effect of renal impairment on the pharmacokinetics of telbivudine. Thirty-six subjects were assigned, on the basis of creatinine clearance (CL(CR)), to 1 of 5 renal function groups with 6 to 8 subjects per group: normal renal function; mild, moderate, or severe renal impairment; or end-stage renal disease [ESRD] requiring hemodialysis. Subjects received a single oral dose of telbivudine at 600 mg (normal function and mild impairment), 400 mg (moderate impairment), or 200 mg (severe impairment and ESRD); plasma and/or urine samples were collected over a 48-h period for pharmacokinetic analyses. Telbivudine was well tolerated by all subjects. The pharmacokinetics of 600 mg of telbivudine were comparable for subjects with mild renal impairment and normal renal function. Likewise, for subjects with moderate to severe impairment, including ESRD, reduced doses from 200 to 400 mg produced plasma exposure similar to that for subjects with normal renal function. These results indicate that the pharmacokinetics of telbivudine were dependent on renal function, especially for subjects with moderate to severe renal impairment or ESRD. Apparent total plasma clearance, renal clearance (CL(R)), and urinary excretion of telbivudine decreased as renal function deteriorated. A linear relationship was established between CL(R) and CL(CR). In ESRD subjects, a routine 3.5- to 4-h hemodialysis session removed telbivudine from plasma at an extraction ratio of approximately 45%, representing a approximately 23% reduction in total exposure. These results suggest that while no adjustment of the telbivudine dose appears necessary for subjects with mild renal impairment, dose adjustment is warranted for those with moderate to severe renal impairment or ESRD in order to achieve optimal plasma exposure.

Chronic hepatitis B virus (HBV) infection affects > 350 million individuals worldwide. Chronic hepatitis B is associated with complications of end-stage liver disease, including cirrhosis and hepatocellular carcinoma. HBV replication is the best predictor of liver disease progression to cancer, and antiviral therapy may diminish or halt this unfavorable outcome. Six drugs have been approved for the treatment of chronic hepatitis B: interferon-alpha(2b), pegylated interferon-alpha(2a), lamivudine, adefovir, entecavir and telbivudine. Most agents designed to target hepatitis B are hindered by the development of resistance, poor tolerability or limited efficacy; therefore, new agents and treatment strategies are needed. Telbivudine is the latest approved anti-HBV agent; it is an orally administered nucleoside analog that selectively inhibits HBV replication. It has demonstrated potent activity against HBV in Phase III clinical studies, with good tolerance, lack of mitochondrial toxicity and no dose-limiting side effects.

Two phase I studies were conducted to assess the plasma pharmacokinetics of telbivudine and potential drug-drug interactions between telbivudine (200 or 600 mg/day) and lamivudine (100 mg/day) or adefovir dipivoxil (10 mg/day) in healthy subjects. Study drugs were administered orally. The pharmacokinetics of telbivudine were characterized by rapid absorption with biphasic disposition. The maximum concentrations in plasma (Cmax) were reached at median times ranging from 2.5 to 3.0 h after dosing. Mean single-dose Cmax and area under the plasma concentration-time curve from time zero to infinity (AUC0-infinity) were 1.1 and 2.9 microg/ml and 7.4 and 21.8 microg . h/ml for the 200- and 600-mg telbivudine doses, respectively. Steady state was reached after daily dosing for 5 to 7 days. The mean steady-state Cmax and area under the plasma concentration-time curve over the dosing interval (AUCtau) were 1.2 and 3.4 microg/ml and 8.9 and 27.5 microg . h/ml for the 200- and 600-mg telbivudine repeat doses, respectively. The steady-state AUCtau of telbivudine was 23 to 57% higher than the single-dose values. Concomitant lamivudine or adefovir dipivoxil did not appear to significantly alter the steady-state plasma pharmacokinetics of telbivudine; the geometric mean ratios and associated 90% confidence interval (CI) for the AUCtau of telbivudine alone versus in combination were 106.3% (92.0 to 122.8%) and 98.6% (86.4 to 112.5%) when coadministered with lamivudine and adefovir dipivoxil, respectively. Similarly, the steady-state plasma pharmacokinetics of lamivudine or adefovir were not markedly affected by the coadministration of telbivudine; the geometric mean ratios and associated 90% CI, alone versus in combination with telbivudine, were 99.0% (87.1 to 112.4%) and 92.2% (84.0 to 101.1%), respectively, for the lamivudine and adefovir AUCtau values. Moreover, the combination regimens studied were well tolerated in all subjects. The results from these studies provide pharmacologic support for combination therapy or therapy switching involving telbivudine, lamivudine, and adefovir dipivoxil for the treatment of chronic hepatitis B virus infection.

This study evaluated the effect of hepatic impairment on the pharmacokinetics of telbivudine, an investigational nucleoside antiviral for the treatment of chronic hepatitis B virus infection. Twenty-four subjects were assigned to four hepatic function groups (normal function and mild, moderate, and severe impairment, with six subjects in each group) on the basis of Child-Pugh scores. The subjects were administered a single oral dose of 600 mg telbivudine, and blood samples were collected over a 48-h interval for pharmacokinetic analyses. Telbivudine was well tolerated by all subjects. Telbivudine plasma concentration-time profiles were similar across the four hepatic function groups. The principal pharmacokinetic parameters of drug exposure, i.e., the maximum plasma concentration and area under the drug concentration-time curve, were comparable between subjects with various degrees of hepatic impairment and those with normal hepatic function. Results from this single-dose pharmacokinetic assessment therefore provide a pharmacologic rationale for further evaluation of the safety and efficacy of telbivudine in hepatitis B virus-infected patients with decompensated liver diseases.