A study of the pharmacokinetic interaction between lamivudine and alpha interferon

Pharmacology, clinical efficacy and safety of lamivudine in hepatitis B virus infection

Lamivudine was the first nucleoside analog for the treatment of chronic hepatitis B (CHB). It is well-tolerated and induces a decrease in serum HBV DNA levels associated with normalization of serum alanine aminotransferase levels. However, a sustained response with hepatitis B 'e' antigen to anti-hepatitis B e seroconversion is obtained in a smaller proportion of patients and hepatitis B surface antigen loss is exceptional. The response is maintained during therapy, and needs to be continued indefinitely in the majority of patients since withdrawal of treatment is generally followed by a rapid reappearance of the virus. However, mutations can be induced in long-term treatment.

The influence of interferon-alpha and combination interferon-alpha and lamivudine therapy on height and weight in children with chronic hepatitis B infection

AIM

To evaluate the height and weight patterns of children with chronic hepatitis B (CHB) with and without treatment.

METHODS

Thirty-four patients with immunoactive CHB randomly assigned to receive interferon-alpha2a (IFN) (5 mIU/m2, 6 months, group I) or IFN (same dose and duration) plus lamivudine (4 mg/kg/day, 24 months) (group II). Fifteen immunotolerant patients (group III) were followed without any treatment. Height (Ht-SDS), weight (Wt-SDS) and growth velocity (GV-SDS) standard deviation scores were monitored for a total of 36 months.

RESULTS

Ht-SDS was significantly lower in group II than in group I one year after completion of IFN treatment (p < 0.05). Wt-SDS was significantly higher in group I than the other groups two years after completion of IFN treatment (p < 0.05). In groups I and II, the percentage of children showing abnormal GV-SDS decreased once treatment was completed (p < 0.05).

CONCLUSION

CHB does not have deleterious effects on height and weight. Although IFN treatment temporarily compromises weight gain and growth velocity, lamivudine does not have any additional adverse effect.

Combination and newer therapies for chronic hepatitis B

Worldwide the need for effective therapy for chronic hepatitis B is similar to that for chronic hepatitis C. Current licensed treatment for chronic hepatitis B (interferon (IFN)-alpha, lamivudine) does not significantly alter the natural history of the disease because the frequency of sustained response is too low; however, a sustained response to antiviral therapy improves survival. Conversion of active chronic hepatitis B to the inactive hepatitis B carrier state (persistently HBeAg-negative, HBV-DNA < 10(5) copies/mL and alanine aminotransferase (ALT) normal) is the major therapeutic goal. If present 6-12 months after stopping treatment, a sustained response is assumed. Clinical benefit is also likely if HBV-DNA levels < 10(5) copies/mL and ALT normality are being maintained long-term by antiviral therapy. New drugs are adefovir, entecavir, and pegylated IFN. The two nucleoside analogs are active against lamivudine-resistant hepatitis B and are as yet not associated with resistance. Peg-IFN has higher efficacy than standard IFN; its tolerance is similar. Combination therapy appears most effective: IFN-lamivudine combination for induction of a sustained response, and lamivudine-adefovir for long-term antiviral therapy. Uncertainty exists whether the additional effect outweighs the burden of adverse effects and cost. Chronic hepatitis B affects a rather heterogeneous patient population. Differentiation based on HBeAg status is fading with emergence of categorization based on disease stage and immune competence.

Hepatitis B treatment: rational combination chemotherapy based on viral kinetic and animal model studies

Hepatitis B virus (HBV) causes a generally non-cytopathic infection in the liver. Even though HBV is a DNA virus, it replicates via reverse transcription which is coordinated within the viral nucleocapsid by the virus-specific polymerase. The major transcriptional template is the viral mimichromosome from which the viral DNA exists as a covalently closed circular (ccc) molcule. The virus infects hepatocytes but can also be found in non-hepatocyte reservoirs such as bile-duct epithelium, mesangial cells of the kidney, pancreatic islet cells and lymphoid cells. When patients infected with HBV are treated with either interferon alpha or lamivudine, responses are variable and unpredictable. Sophisticated mathematical models analysing the dynamics of viral clearance during antiviral therapy have recently been applied to chronic hepatitis B. Typically complex profiles, rather than the usual biphasic responses seen with other diseases have been observed, indicating that antiviral efficacy requires substantila improvement. This may be achieved with combination chemotherapy. However, chronic hepatitis B is a complex and heterogeneous disease entity, and the challenge for the future is to define measurable end-points of treatment and address key virological issues such as the role of cccDNA and extra-hepatocyte replication in treatment failure. Clearly, new therapies and effective combination therapy protocols are urgently required in order to improve the present poor response rates in patients undergoing treatment.

How will we use the new antiviral agents for hepatitis B?

There are two licensed drugs for chronic hepatitis B virus (HBV), interferon alfa and lamivudine, with similar efficacy rates. Lamivudine is less expensive and better tolerated than interferon alfa and is the drug of choice for patients with decompensated cirrhosis and recurrent HBV infection after liver transplantation. The major problem with lamivudine monotherapy has been the emergence of drug-resistant HBV polymerase (YMDD) mutants. Thus, long-term use of lamivudine in other settings remains somewhat controversial. Alternative nucleoside analogues that are active against both wild-type and YMDD-mutant HBV are currently being tested. It is hoped that a combination of one or more of these agents with lamivudine will not only prove more effective than lamivudine alone but also decrease the rate of lamivudine resistance. Preliminary studies suggest that the combination of interferon and lamivudine is associated with an enhanced rate of virologic response when compared with either agent alone. From a theoretical perspective, the combination of interferon with one or more nucleoside analogues may be the most effective way to treat HBV infection in many clinical situations.