I. Pharmacokinetics of FTC. FTC is a cytosine nucleoside analogue. After oral absorption, it forms active triphosphate after multi-step phosphorylation in vivo, which eventually leads to interruption of its DNA strand synthesis through competitive admixture with natural cytosine in the process of viral DNA synthesis. Oral administration is rapidly absorbed and widely distributed, with peak plasma drug concentrations 1 to 2 hours after administration. In vitro studies have shown that FTC is not metabolized by CYP450 enzymes; its plasma half-life is approximately 10 hours, and its renal clearance is higher than that of creatinine, presumably through glomerular filtration and excreted via the renal tubular secretion pathway. In vitro tests and animal studies have shown that the combination of tenofovir (TDF) and FTC has a synergistic anti-HBV effect. the AUC and Cmax of FTC oral absorption pharmacokinetics are not affected by food intake. Second, FTC for the treatment of chronic hepatitis B. 1, FTC treatment of primary treatment CHB patients. The multicenter, double-blind, randomized, placebo-controlled clinical study of FTC for primary treatment of CHB patients reported by Lim et al. included 248 primary treatment HBeAg-positive and HBeAg-negative CHB patients, including 167 in the FTC treatment group (oral FTC 200 mg, qd) and 81 in the placebo control group. The results of 48 weeks of treatment showed that the proportion of patients with HBV DNA < 400 copies/ml was significantly higher in the FTC group than in the placebo group (91% vs. 2%, P<0.001); the rate of ALT normalization was significantly higher than in the placebo control group (65% vs. 25%, P<0.001); and the rate of histological improvement was significantly higher than in the placebo group (62% vs. 25%, P<0.001). The safety index of the FTC group was comparable to that of the placebo group. Therefore, FTC alone can effectively inhibit HBVDNA replication and improve biochemical and histological parameters in patients with primary CHB, but drug resistance should be monitored closely during the course of administration. In view of the drug resistance problem in patients with CHB treated with FTC alone, some studies have investigated FTC in combination with TDF or adefovir (ADV) for the treatment of patients with primary CHB. cases. The proportion of patients with HBV DNA <300 copies/ml and the proportion of patients with normalized ALT was significantly higher in the FTC+ADV group than in the ADV+placebo group (78.6% compared to 37.5%, P = 0.05). FTC and ADV resistance mutations were not detected in the ADV+FTC combination up to 96 weeks. Therefore, FTC in combination with ADV therapy was effective in inhibiting HBV DNA replication and reducing the incidence of FTC resistance. Recommendation 2: FTC in primary CHB patients can effectively inhibit HBVDNA replication, improve patients' biochemical and histological parameters, and is safe and well tolerated; it can be one of the treatment options in CHB patients who are eligible for anti-HBV treatment. 2. FTC for treated patients with CHB. Santos et al. reported that FTC/TDF used in patients who failed ADV treatment significantly inhibited HBVDNA replication. The study included seven patients with poor ADV virological response who switched to FTC/TDF for a mean of 23 months, and all patients achieved HBV DNA below the lower limit of detection, with a mean HBV DNA load reduction of 3.0 log10 copies/ml and no detectable renal impairment. The study suggested that the combination of FTC/TDF could be considered in patients with poor ADV response.Berg et al. reported the use of FTC/TDF in patients with CHB with poor ADV response.A total of 52 patients were enrolled in the study and 39 patients completed 168 weeks of treatment, resulting in virological response (HBVDNA <400 copies/ml) in 82% of patients with good safety tolerability.Fung et al. reported FTC/TDF was used in patients with LAM-resistant CHB. 139 patients with LAM-resistant CHB were enrolled and treated for 96 weeks, resulting in HBVDNA < 69 IU/ml in 86.3% of patients, and was safely tolerated. Further data on the switch to FTC/TDF in patients treated with telbivudine (LdT) and entecavir (ETV) need to be accumulated and applied. The expert committee may also consider FTC/TDF as one of the follow-up regimens for patients treated with LdT and ETV, taking into account the antiviral activity and cross-resistance of FTC/TDF. Recommendation 3: Patients with LAM, ADV, LdT and ETV treated patients can consider switching to FTC/TDF for antiviral therapy, which can achieve virological suppression and is well tolerated safely. Third, FTC is used for antiviral therapy in special HBV-infected patients. 1, FTC for the treatment of human immunodeficiency virus ()/HBV co-infected patients. Avihingsanon et al [14] reported that the addition of FTC to a highly active antiretroviral therapy (HAART) regimen for HIV/HBV co-infected patients inhibited HBVDNA replication. The study was divided into the FTC/zidovudine (AZT)/efavirenz (EFV) group and the FTC/TDF/EFV group. Six patients were included in the former and 10 patients in the latter. The results at 48 weeks of treatment showed that the mean decrease in HBVDNA in the FTC/AZT/EFV group was 3.25 log10 copies/ml and the proportion of patients with HBV DNA < 170 copies/ml was 33%, both lower than that in the FTC/TDF/EFV group (5.32 log10 copies/ml, 90%, P < 0.05). The study suggests that HBV/HIV co-infected patients may be considered for the addition of FTC with TDF to the HAART regimen.Engell et al [15] reported HBV/HIV co-infected patients on primary treatment with FTC/TDF, enrolling 12 patients on primary treatment, and achieving virological response in 60% of patients by 12 months of treatment and 100% by 24 months. The results suggest that HBV/HIV co-infected patients can add FTC with TDF to the HAART regimen to suppress HBV replication. Therefore, FTC+TDF was effective in suppressing HBVDNA replication and improving biochemical parameters in both primary and treated HIV/HBV co-infected patients with nucleoside (acid) analogs; it is recommended that FTC+TDF be added to HAART regimens if patients should be treated with both anti-HIV and HBV. Recommendation 4: HIV/HBV co-infected patients who need to be treated with both anti-HIV and HBV treatment, FTC+TDF can be considered to be included in HAART treatment. 2. FTC for antiviral therapy in pediatric CHB patients. FTC has a good safety profile and has been approved for antiviral therapy in HIV-infected children aged 0-18 years. 200 mg?qd can be given orally to patients weighing >33 kg who can swallow capsule formulations; liquid formulations of 6 mg/kg?qd can be given to patients who cannot swallow capsules, such as those >3 months of age; 3 mg/kg?qd can be given to those <3 months of age. However, there is no evidence in patients with CHB alone. Considering its efficacy and safety, individualized application of FTC for anti-HBV therapy can be considered in general patients with full informed consent. Recommendation 5: FTC can be considered for anti-HBV treatment in underage HIV/HBV co-infected patients; general CHB patients can consider individualized application of FTC for anti-HBV treatment with full informed consent. 3, FTC for HBV-infected patients during pregnancy. FTC is a U.S. Food and Drug Administration (FDA) pregnancy class B drug, and it has accumulated a lot of experience in blocking vertical transmission from mother to child in HIV-infected patients. The U.S. Anti-Retroviral Registry website through July 31, 2013 reported a birth defect rate of 2.4% in 1,400 patients who applied the FTC formulation during the first 3 months of pregnancy and a birth defect rate of 2.1% in 669 patients who applied the FTC formulation during the second 6 months of pregnancy. The birth defect rate was comparable to the group of patients who did not apply FTC. There is no evidence for the use of FTC in patients with CHB during pregnancy. Considering its experience in HIV-infected patients and pregnancy staging, some patients with CHB during pregnancy may consider the application of FTC for prophylactic mother-to-child transmission blockade and anti-HBV treatment in actively infected patients, as appropriate. Recommendation 6: FTC can be used for mother-to-child vertical transmission interruption of HBV infection during pregnancy and antiviral therapy for those with active HBV infection during pregnancy, as appropriate, with full informed consent. 4. FTC is used to prevent HBV reinfection in liver transplant patients. FTC/TDF has been reported for the prevention of HBV reinfection after liver transplantation, in which Teperman et al. reported that 40 patients with in situ liver transplantation were randomly discontinued after 24 weeks of treatment with FTC/TDF + hepatitis B immunoglobulin (HBIG) or without discontinuing HBIG treatment for 72 weeks, and the results showed that patients in the discontinued HIBG group were not seen in the FTC/TDF group only. HBV reinfection was not seen in the HIBG group and was safely tolerated. This suggests that prevention of HBV reinfection with FTC/TDF alone can be considered after 24 weeks of FTC/TDF+HBIG treatment in in situ liver transplant patients, but this study needs to be further confirmed with a larger sample size and longer treatment duration data. Therefore, FTC/TDF can be used for the prevention of HBV reinfection after transplantation in patients with in situ liver transplantation. Recommendation 7: FTC/TDF combined with HBIG can be used for the prevention of HBV reinfection after liver transplantation; some liver transplant patients can be considered for the prevention of HBV reinfection with FTC/TDF only after 24 weeks of FTC/TDF + HBIG treatment. 5. FTC is used in patients with decompensated cirrhosis. Liaw et al. reported the interim results of a phase II clinical study of FTC/TDF in patients with HBV-related decompensated liver disease, showing that the rate of patients with HBV DNA < 400 copies/ml was 87.8% at 1 year of treatment in the FTC/TDF group. 76% of patients had a normalized ALT rate. The patient's Child-Pugh score and MELD score both improved. This indicates that FTC/TDF can effectively suppress HBVDNA and improve Child-Pugh scores in patients with decompensated liver disease. Based on this, FTC/TDF can be used for the antiviral treatment of patients with decompensated hepatitis B cirrhosis. Recommendation 8: Patients with decompensated hepatitis B cirrhosis who meet the antiviral indications can be considered for FTC/TDF as one of the treatment options (A2). IV. Monitoring, optimization of treatment and resistance management of FTC therapy. (I) Monitoring of FTC therapy. 1.Monitoring during FTC treatment: Relevant indicators should be monitored regularly during FTC treatment: ①Biochemical indicators: including liver function indicators such as ALT, which should be tested once a month after the start of treatment, for 3 times continuously, and then once every 3 months as the condition improves. ② Virological markers: HBV DNA should be tested every 3 months after the start of treatment, and HBsAg, HBeAg and anti-HBe should be tested every 3-6 months. ③ HCC monitoring: AFP and abdominal ultrasound imaging (CT or MRI if necessary) should be tested every 3-6 months for early detection of HCC. ④: Blood creatinine, creatine kinase and blood lactate should be tested regularly during FTC treatment. indicators. ⑤ Treatment monitoring should follow the principle of individualization and can be adjusted accordingly according to the patient's condition. 2. Follow-up after discontinuation of FTC: Although the relevant guidelines suggest that patients who meet the corresponding indications may consider discontinuing anti-FTC therapy, the expert committee strongly recommends that antiviral therapy for FTC should be discontinued with caution, and extending the course of FTC therapy can improve the efficacy and reduce relapse. ALT, HBsAg, HBeAg, anti-HBe and HBVDNA should be tested at least once every 1 to 2 months for 6 months after discontinuation, and every 3 to 6 months thereafter, with a minimum follow-up of 12 months. The follow-up interval should be shortened if there is any change in the condition during the follow-up. (B) Response-guided treatment of FTC. At present, there is a lack of evidence regarding the optimal treatment of patients with primary non-response and poor response to FTC. Considering the similarities between FTC and LAM in terms of mechanism of action, inhibition of viral effects and occurrence of drug resistance, it is recommended to refer to LAM for treatment related to primary non-response and poor response, which can be referred to the Expert Consensus on Antiviral Therapy for Patients with Chronic Hepatitis B Nucleoside (Acid) Analogues Under Treatment. (B) Drug resistance of FTC treatment. FTC is a low resistance genetic barrier drug, and its resistance should be closely monitored in clinical application. Both in vivo and in vitro studies have shown that the FTC resistance locus is the same as LAM, i.e. rtM204V/I ± rtL180M variant, and the incidence of genotypic resistance at 1 year of FTC treatment is 13%-16%, but long-term resistance data are lacking. Patients should be adequately evaluated for treatment indications and a detailed history of prior therapy should be obtained before initiating FTC therapy. Patients with CHB in the immune tolerance phase are generally not recommended for antiviral therapy unless they require special circumstances such as immunosuppressive therapy. Patients with CHB who develop elevated ALT for the first time should be analyzed for possible triggers and antiviral therapy should be started cautiously; patients should be urged to take medication regularly during FTC treatment and be followed up regularly to improve patient compliance as much as possible. If patients are found to have poor virological response or virological breakthrough during follow-up, it should be promptly clarified whether patients have compliance problems. After ruling out compliance problems, HBV genotype resistance testing should be performed in a timely manner to clarify FTC drug resistance and adjust the treatment plan accordingly. The evidence for FTC resistance salvage therapy is not yet sufficient. In reference to LAM drug resistance salvage therapy, the addition of ADV or TDF antiviral therapy may be considered, or the switch to TDF antiviral therapy may be considered. Recommendation 9: The salvage treatment of FTC resistance can be referred to LAM, and the addition of ADV or TDF antiviral therapy can be considered, and the switch to TDF antiviral therapy can also be considered. V. Safety of FTC. A large amount of safety data has been accumulated on the use of FTC in the treatment of HIV-infected patients, and the available data indicate that it is well tolerated safely. Similar to other nucleoside (acid) analogues, patients should be closely monitored for blood creatinine, blood lactate, creatine kinase and other indicators during FTC treatment. VI. Issues to be further addressed or clarified for FTC. FTC for different types of HBV infected patients has accumulated certain clinical data, and its safety and tolerability have been widely recognized. In particular, both in vivo and ex vivo studies have confirmed that FTC/TDF inhibits HBV better than TDF monotherapy formulations, providing a new treatment option for patients with high baseline viral load and poor HBV inhibition by other antiviral drugs. However, the drug resistance problem of FTC needs to be given full attention by clinicians, and the efficacy and safety data of its use in Chinese CHB patients still need to be accumulated. The recommendations formed by this consensus are based on the available data and the views of the experts present, and will be updated as relevant evidence accumulates.