A 42-year-old man with a 10-year history of HBsAg positivity presents with HBV DNA level of 2 × 10^5 IU/mL and ALT 3 times the upper limit of normal. Liver biopsy shows moderate inflammation and early fibrosis. He is HBeAg-positive. What is the drug of choice to initiate antiviral therapy?

Explanation

## First-Line Antiviral Therapy for Chronic Hepatitis B ### Indications for Treatment in HBeAg-Positive Chronic HBV Treatment is indicated when: - HBV DNA ≥2 × 10^5 IU/mL (or ≥10^5 copies/mL) - AND ALT ≥ 1 × ULN (or evidence of significant fibrosis on biopsy) This patient meets both criteria. ### First-Line Antiviral Agents **Key Point:** Entecavir and tenofovir are the preferred first-line nucleos(t)ide analogues for chronic HBV due to high barrier to resistance, potent viral suppression, and favorable safety profiles. | Agent | Barrier to Resistance | HBV DNA Suppression | Renal Safety | First-Line? | |-------|----------------------|-------------------|--------------|-------------| | Entecavir | High | Excellent (>90% undetectable) | Safe | **YES** | | Tenofovir | High | Excellent (>90% undetectable) | Monitor renal function | **YES** | | Lamivudine | Low | Moderate | Safe | NO (resistance) | | Adefovir | Intermediate | Moderate | Monitor renal function | NO (less potent) | | Interferon-α | N/A | Variable | N/A | NO (side effects, contraindications) | ### Why Entecavir Is Optimal 1. **High barrier to resistance:** <1% resistance at 5 years in treatment-naïve patients 2. **Potent viral suppression:** Achieves HBV DNA <20 IU/mL in >90% of patients 3. **Excellent tolerability:** Minimal side effects, no renal toxicity 4. **Oral administration:** Once-daily dosing improves adherence 5. **No cross-resistance with tenofovir:** Allows salvage therapy if needed **High-Yield:** Entecavir 0.5 mg once daily is the standard dose for treatment-naïve patients. Lamivudine-resistant patients require 1 mg daily. ### Why Interferon-Alpha Is Not First-Line - Requires parenteral administration (subcutaneous 3× weekly) - Significant side effects: flu-like symptoms, depression, cytopenias, autoimmune exacerbation - Lower response rates in HBeAg-positive patients with high HBV DNA - Contraindicated in decompensated cirrhosis - May be considered in selected HBeAg-positive patients with mild disease and high ALT as an alternative to achieve HBeAg seroconversion **Clinical Pearl:** HBeAg seroconversion (loss of HBeAg and development of anti-HBe) is a treatment endpoint that may allow discontinuation of nucleos(t)ide therapy in some patients; however, continuous monitoring is required as reactivation can occur.