Efficacy of TDF, TAF, TMF, and TDF-to-TAF switch in chronic hepatitis B:

The efficacy of TDF, TAF, TMF, and the TDF-to-TAF switch in treating chronic hepatitis B (CHB) has been extensively studied to identify the most effective regimen for individualized care. Here is a detailed breakdown of their efficacy based on the study context:

### 1. **TDF (Tenofovir Disoproxil Fumarate):**

• **Virological Response:** TDF is highly effective in suppressing HBV replication. It achieves similar viral suppression rates as TAF and TMF.
• **HBsAg Clearance:** HBsAg clearance is rare (<5%) across all regimens, including TDF, indicating limited ability to achieve functional cure.
• **HBeAg Loss:** TDF demonstrated lower rates of HBeAg loss compared to TAF, suggesting relatively weaker immune restoration.
• **ALT Normalization:** TDF showed good efficacy in normalizing ALT levels but was outperformed by TMF and TAF.
• **Safety Concerns:** Long-term use of TDF has been associated with renal and bone safety issues, including declines in estimated glomerular filtration rate (eGFR) and bone mineral density (BMD).

### 2. **TAF (Tenofovir Alafenamide):**

• **Virological Response:** TAF achieves similar viral suppression rates as TDF and TMF.
• **HBsAg Clearance:** TAF showed no significant advantage in HBsAg clearance compared to other regimens (<5% clearance rate).
• **HBeAg Loss:** TAF demonstrated the highest HBeAg clearance rates among the four regimens, indicating stronger immune restoration potential.
• **ALT Normalization:** TAF provided high rates of ALT normalization, comparable to TMF.
• **Safety Profile:** TAF significantly improves renal and bone safety compared to TDF. It causes minimal declines in eGFR and less BMD loss during long-term follow-up, making it a safer alternative for patients with pre-existing comorbidities.

### 3. **TMF (Tenofovir MonoFumarate):**

• **Virological Response:** TMF achieves comparable viral suppression rates to TDF and TAF, indicating strong antiviral efficacy.
• **HBsAg Clearance:** Similar to other regimens, TMF showed rare HBsAg clearance (<5%).
• **HBeAg Loss:** TMF demonstrated comparable HBeAg loss rates to TAF, indicating good immune restoration potential.
• **ALT Normalization:** TMF showed the highest ALT normalization rates among the four regimens, suggesting better hepatic enzyme recovery potential.
• **Safety Profile:** TMF exhibited promising biochemical improvements, but long-term data on renal and bone safety are limited. Most TMF trials were short-term (≤48 weeks) and predominantly conducted in Asian populations.

### 4. **TDF-to-TAF Switch:**

• **Virological Response:** Patients switching from TDF to TAF initially showed slightly higher virological response rates compared to TDF alone. However, this advantage diminished after adjusting for confounders.
• **HBsAg Clearance:** No significant improvement in HBsAg clearance was observed after switching to TAF.
• **HBeAg Loss:** Switching to TAF did not significantly enhance HBeAg loss rates compared to TAF monotherapy.
• **ALT Normalization:** The switch provided comparable ALT normalization rates to TAF monotherapy.
• **Safety Benefits:** Patients switching from TDF to TAF experienced notable improvements in renal and bone safety markers, including better eGFR and reduced bone mineral density loss, without compromising antiviral efficacy. This supports transitioning to TAF in patients with existing renal or bone comorbidities.

### **Efficacy Rankings (SUCRA Probabilities):**

Based on surface under the cumulative ranking (SUCRA) probabilities:

• **Virological Response:** TDF-to-TAF switch ranked highest.
• **HBeAg Loss:** TAF and TMF ranked highest.
• **ALT Normalization:** TMF ranked highest.
• **HBsAg Clearance:** TAF ranked highest, though clearance rates remained rare across all regimens.

### **Clinical Implications:**

• **TAF:** Emerged as the most balanced regimen, combining strong antiviral activity with superior renal and bone safety. It is ideal for patients with pre-existing bone or renal issues.
• **TMF:** Shows promise for hepatic enzyme normalization and may serve as an alternative for patients with high ALT but preserved renal function. However, its long-term safety profile requires further study.
• **TDF:** Remains a cost-effective option for low-risk individuals without renal or bone concerns.
• **TDF-to-TAF Switch:** Recommended for patients experiencing renal or bone complications during long-term TDF therapy, as it improves safety without compromising efficacy.

### **Limitations:**

• TMF data are primarily short-term, with limited long-term follow-up on resistance or cumulative toxicity beyond 144 weeks.
• Most studies lacked detailed long-term data on outcomes like resistance or cumulative toxicity.

### **Conclusions:**

• All four regimens effectively suppress HBV replication.
• TAF stands out as the most comprehensive option, combining efficacy and safety.
• TMF shows promise for hepatic normalization, warranting further multicenter and long-duration studies to confirm its role in CHB therapy.
• Switching from TDF to TAF is beneficial for patients with renal or bone comorbidities.

This detailed evaluation highlights the strengths and limitations of each regimen, enabling clinicians to tailor CHB therapy based on individual patient needs and risk profiles.