Chronic Hepatitis B: Tenofovir, Entecavir, and Functional Cure Strategies
Treatment Indications: Who Needs Antiviral Therapy
The 2022 AASLD guidance and 2024 EASL Clinical Practice Guidelines recommend antiviral therapy for all patients with HBV DNA above 2,000 IU/mL and ALT above the ULN (35 U/L for males, 25 U/L for females per AASLD-defined thresholds), significant fibrosis (Metavir F2 or above), cirrhosis regardless of HBV DNA level, and immunosuppressed patients with any detectable HBV DNA. The simplified AASLD 2023 algorithm expands treatment eligibility to include all HBeAg-positive patients over age 30 with HBV DNA above 10,000 IU/mL regardless of ALT, reducing the number of patients in the monitoring-only category.
Tenofovir versus Entecavir: Comparative Efficacy
Both tenofovir disoproxil fumarate (TDF, 300 mg daily) and entecavir (ETV, 0.5 mg daily for treatment-naive) achieve HBV DNA suppression below 20 IU/mL in 93-97% of patients by 48 weeks. A landmark Korean cohort study (Choi et al., 2019, JAMA Oncology) suggested TDF may reduce HCC risk compared to ETV (adjusted HR 0.68, 95% CI 0.59-0.78), though subsequent randomized trials (including the 2024 TARGET study) found no significant difference in HCC incidence (HR 0.92, 95% CI 0.65-1.31). Tenofovir alafenamide (TAF, 25 mg daily) provides comparable virologic efficacy with significantly less renal and bone toxicity: at 96 weeks, the TAF pivotal trials showed 0% versus 5% decline in hip BMD and 0.1% versus 1.2% decline in eGFR compared to TDF.
Monitoring on Antiviral Therapy
HBV DNA quantification every 3-6 months until undetectable, then every 6-12 months. HBeAg and anti-HBe every 6-12 months for HBeAg-positive patients. HBsAg quantification annually guides functional cure trajectory: an annual decline exceeding 0.5 log IU/mL predicts eventual HBsAg loss. ALT and hepatic function panels every 6 months. For patients on TDF, serum creatinine, phosphate, and urinalysis annually. HCC surveillance with abdominal ultrasound plus AFP every 6 months for patients with cirrhosis, significant fibrosis, or additional risk factors (Asian males above 40, Asian females above 50, family history of HCC, or African-origin patients above 20).
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Functional Cure: HBsAg Loss Strategies
Functional cure, defined as sustained HBsAg loss with or without anti-HBs seroconversion, occurs in less than 1% per year with nucleos(t)ide analogs alone. Peginterferon alfa-2a (180 mcg weekly for 48 weeks) achieves HBsAg loss in 3-7% of HBeAg-positive patients at 1 year post-treatment. The combination of NUC plus peginterferon (add-on or switch strategies) increases HBsAg loss rates to 8-12% in selected patients with declining HBsAg levels below 1,000 IU/mL. Novel agents in phase 2-3 trials include RNA interference (bepirovirsen showed 9% HBsAg loss at 24 weeks in the B-Clear study), core protein allosteric modulators, and therapeutic vaccines targeting cccDNA and integrated HBV DNA.
Safe Discontinuation of Antiviral Therapy
NUC discontinuation can be considered in non-cirrhotic HBeAg-negative patients with sustained virologic suppression (HBV DNA undetectable for 3 or more years) and HBsAg levels below 100 IU/mL. The STOP-NUC trial demonstrated HBsAg loss at 144 weeks in 19% of patients who discontinued TDF versus 3% who continued (p<0.001), though 48% experienced hepatitis flares. The RETRACT-B study confirmed that low baseline HBsAg (below 100 IU/mL) is the strongest predictor of successful discontinuation. Close monitoring with ALT and HBV DNA every 4 weeks for 3 months, then every 3 months for 1 year, is mandatory after discontinuation.
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