According to the latest estimates from the World Health Organization, the global seroprevalence of hepatitis B surface antigen (HBsAg) in 2019 was 4.1%, with approximately 316 million people living with chronic hepatitis B (CHB) (Global, regional, and national burden of hepatitis B, 1990-2019: a systematic analysis for the Global Burden of Disease Study 2019, 2022). HBV infection is a major contributor to the development of liver cirrhosis and hepatocellular carcinoma (HCC). Additionally, acute exacerbations, viral reactivation, extrahepatic complications, and psychosocial impacts further exacerbate the societal burden of HBV infection (Hsu et al., 2023). Early diagnosis, appropriate antiviral therapy, and proactive monitoring of clinical complications are critical to alleviating the disease burden in individuals with HBV infection. Currently, the optimal therapeutic goal for CHB is achieving functional cure, but this target remains challenging to achieve on a broad scale (Ghany et al., 2023).

Interferon (IFN) has been used to treat CHB for nearly 50 years and has demonstrated higher rates of HBeAg and HBsAg seroclearance compared to nucleos(t)ide analogs (NAs) (Wong et al., 2022). In recent years, various combination strategies involving NAs and IFNα have been evaluated to improve HBsAg seroclearance rates. A meta-analysis of 60 studies revealed that combination therapy with NAs and IFNα significantly enhances HBsAg seroclearance rates compared to NA monotherapy (Liu et al., 2020). Recent studies further indicate that IFNα, as an add-on therapy, can improve HBsAg clearance rates in HBeAg-negative CHB patients who have been treated with NAs for more than one year (Wu et al., 2020; Farag et al., 2024).

Numerous studies have highlighted the importance of baseline biomarkers, including HBsAg levels, HBV DNA levels, HBeAg status, anti-HBc, and liver function, in predicting patient responses to antiviral therapy (Chan et al., 2018; Wang et al., 2022; Wang et al., 2024; Zhang et al., 2024). Generally, patients with undetectable HBV DNA, HBeAg negativity, and lower baseline HBsAg levels are considered ideal candidates for achieving clinical cure with IFNα therapy. However, in real-world clinical practice, interferon is used not only for these favorable patient populations but also for CHB patients with varying baseline characteristics. The differences in HBsAg seroclearance rates and the dynamics of HBsAg levels during IFNα treatment among favorable and non-favorable patients remain poorly understood. The primary reasons include the relatively limited use of interferon compared to nucleos(t)ide analogs due to its significant adverse effects and the inherent challenges of achieving functional cure for hepatitis B. Consequently, previous studies on functional cure have been limited, with few large-scale investigations addressing this critical outcome.

This study systematically analyzed data from a large cohort of CHB patients treated with interferon to evaluate the relationships between various baseline characteristics and functional cure. Additionally, generalized estimating equations were applied to assess the overall trend of HBsAg level changes. These findings aim to provide more precise individualized assessment and treatment guidance for CHB patients.

This study retrospectively analyzed functional cure outcomes in 5,288 chronic hepatitis B (CHB) patients receiving interferon therapy, highlighting the impact of various baseline characteristics and biochemical markers on treatment efficacy. To the best of our knowledge, this is the largest real-world study to date focusing on CHB patients treated with interferon, particularly with functional cure as the therapeutic goal. The findings of this study provide valuable insights and serve as an important reference for individualized treatment strategies in CHB patients.

First, the critical role of baseline clinical characteristics in achieving functional cure deserves attention. Baseline HBsAg levels are instrumental in distinguishing immune tolerance from immune clearance in HBeAg-positive patients, predicting inactive disease and spontaneous HBsAg seroclearance in HBeAg-negative patients, and are essential for individualizing pegylated interferon (Peg-IFN) therapy (Cornberg et al., 2017). In this study, patients in the FC group had significantly lower baseline HBsAg and HBV DNA levels compared to the NFC group, along with a lower HBeAg positivity rate, consistent with findings from previous studies (Chuaypen et al., 2018; Mimura et al., 2021; Chu et al., 2022). CHB patients with lower baseline HBsAg levels and HBeAg negativity demonstrated higher functional cure rates following interferon therapy, suggesting that baseline HBsAg levels and HBeAg status are important predictive factors. These results highlight the importance of risk stratification prior to treatment, as patients with lower baseline levels may derive greater benefit from interferon-based therapy.

Second, the analysis of HBsAg trends over time revealed that patients in the FC group experienced a significant decline in HBsAg levels during the early phase of treatment, whereas the NFC group showed relatively minor changes. This underscores the critical importance of early treatment response in determining long-term outcomes. Previous prospective research by our team demonstrated that quantitative HBsAg levels and changes during the early phase of treatment (Weeks 12 and 24) are strong predictors of HBsAg seroclearance (Cao et al., 2017). Similarly, a study by Filip De Ridder et al. reported that the mean decline in HBsAg levels from baseline at Week 24 serves as an early marker for HBsAg clearance during Peg-IFN therapy (De Ridder et al., 2021). Even among untreated patients, a rapid decline in HBsAg levels has been associated with higher rates of spontaneous HBsAg seroclearance (Chen et al., 2012; Lin et al., 2023). These findings suggest that early changes in HBsAg levels provide critical insights into subsequent treatment responses. This highlights the clinical utility of early HBsAg monitoring as an effective biomarker for predicting functional cure. For patients demonstrating suboptimal treatment responses, trends in HBsAg levels during the early phase can guide treatment modifications to improve success rates. An interesting phenomenon observed in this study is that while all patients exhibited a rapid decline in HBsAg levels during interferon therapy, distinct post-treatment dynamics were noted. Patients with higher baseline HBsAg levels (100–1500 IU/mL and >1500 IU/mL) continued to show a steady decline in HBsAg levels after stopping interferon therapy. In contrast, patients with lower baseline HBsAg levels (<100 IU/mL) who failed to achieve functional cure experienced a rebound in HBsAg levels to baseline or even higher levels after treatment cessation. Therefore, the results of this study suggest that for patients who fail to achieve functional cure under standard IFN therapy, particularly those with low baseline HBsAg levels who are unable to maintain a sustained clearance state, it becomes crucial to adjust the treatment strategy. While IFN therapy is widely used in hepatitis B, its efficacy varies across different patient populations. With the continuous development of next-generation antiviral drugs, such as PD-1 receptor antagonists and small molecules, these treatments may become part of an optimized therapeutic regimen. For patients with persistent or rebounding HBsAg, the adoption of these novel therapies could potentially help them achieve functional cure in the later stages.

Furthermore, this study revealed a significant gender-based difference in HBsAg clearance, with female patients achieving higher clearance rates than males. This phenomenon has been consistently reported in multiple studies. A meta-analysis on factors influencing HBsAg seroclearance in chronic HBV patients treated with Peg-IFNα identified gender as an independent factor associated with Peg-IFN-induced HBsAg seroclearance (Jiang et al., 2024). Similarly, a real-world study investigating HBsAg clearance in HBeAg-negative CHB patients receiving Peg-IFN combination therapy also reported a gender advantage in females, with higher HBsAg seroclearance rates (Chu et al., 2022). Another large cohort study on HBeAg-negative patients treated with Peg-IFN, lamivudine, or combination therapy highlighted that baseline ALT and HBV DNA levels, patient age, female gender, and HBV genotype significantly influenced the composite response at Week 24 post-treatment (Bonino et al., 2007). However, the underlying mechanisms behind this gender difference, particularly its relationship with interferon-based therapy, remain unclear. This disparity may be attributable to certain physiological advantages of the female immune system. Studies have shown that women generally exhibit a more active immune system than men, especially in response to viral infections. Female T-cell responses are often stronger, enabling more effective viral clearance (Dunn et al., 2024). Consequently, female patients undergoing Peg-IFN therapy may benefit from more efficient immune responses, leading to better control of HBV replication and higher rates of HBsAg clearance. Additionally, sex hormones, particularly estrogen, have been demonstrated to play a critical role in modulating immune responses. Estrogen has been shown to enhance the immune functions of both B cells and T cells, which may provide the biological basis for the superior antiviral treatment outcomes observed in female patients (Hoffmann et al., 2023). While it is well-documented that women generally exhibit stronger immune responses compared to men, particularly in response to viral infections, the exact mechanisms behind this phenomenon remain unclear. We have speculated that the higher functional cure rates observed in female patients may be partly due to enhanced T-cell responses or other aspects of the female immune system. However, it is important to note that these observations are based on the existing literature and require further investigation to confirm the underlying mechanisms to better understand this potential immune advantage in women.

Previous retrospective studies have reported the occurrence of thyroid antibodies and thyroid dysfunction in 7.3% and 8.8% of patients, respectively, during Peg-IFNα therapy, with a higher prevalence in female patients (Liu et al., 2023). However, thyroid antibodies and dysfunction are not absolute contraindications for Peg-IFNα therapy, and the development of thyroid dysfunction during treatment has been linked to higher rates of HBsAg seroclearance in CHB patients (Luo et al., 2021). This phenomenon may be closely related to the immunomodulatory effects of thyroid hormones. Studies have shown that thyroid hormones, particularly FT3 and FT4, significantly influence the functions of immune cells, especially T and B cells, by promoting their proliferation and activity, thereby enhancing the immune response (Rubingh et al., 2020). This could explain the stronger ability of the immune system to clear HBV in patients with higher thyroid function, contributing to improved HBsAg clearance rates. In clinical practice, monitoring and managing thyroid function are critical for CHB patients undergoing interferon therapy. While patients with thyroid dysfunction may exhibit higher rates of HBsAg clearance, it is essential to closely monitor changes in thyroid function during treatment to avoid potential side effects or excessive immune responses. Although the exact mechanisms by which FT3 and FT4 influence HBsAg clearance remain unclear, this finding suggests that future research should further explore the potential relationship between thyroid function and the response to antiviral therapy, providing more insights for individualized treatment strategies.

The identification of baseline predictors of functional cure, such as HBsAg levels, HBeAg status, sex, and thyroid hormone levels, provides important insights for the development of personalized treatment strategies and predictive models for chronic hepatitis B (CHB). In our study, patients with HBsAg levels <100 IU/mL have a significantly higher probability of achieving functional cure within a defined treatment period, and a faster decrease in HBsAg levels was observed in patients of the functional cure group. This suggests that HBsAg quantification can therefore be used to screen patients suitable for interferon therapy and to optimize the duration and intensity of treatment (Fan et al., 2024). HBeAg-negative as well as female patients have a higher cure rate and therefore can be prioritized for treatment with interferon. In addition, in our cohort, these interferon-treated patients had thyroid function in the normal range at baseline, yet the correlation of normally high FT3 and FT4 levels with functional cure suggests a role for thyroid function in the immune response. By integrating baseline HBsAg levels and rate of decline on treatment, HBeAg status, gender, and thyroid hormone levels, clinicians can identify patients who are more likely to respond to interferon therapy and thus tailor treatment plans accordingly. Our next studies will consider integrating these baseline metrics into predictive models, which will help to develop individualized treatment regimens, improve treatment success, and reduce unnecessary treatments.

Despite the large sample size and extended follow-up period of this study, several limitations should be acknowledged. First, the inherent constraints of retrospective studies may introduce potential biases. Second, variability in patient adherence to treatment during the follow-up period might have influenced the assessment of functional cure rates. Third, while several factors have been identified as predictors of interferon response in chronic hepatitis B (CHB), such as baseline HBsAg levels and HBeAg status, HBV genotype (e.g., genotype B vs. C) is also a known determinant of treatment outcomes. Unfortunately, genotype data were not available for the majority of patients in this study; the lack of genotype data prevents us from assessing its potential impact on the functional cure rates in our cohort. Thus, larger-scale prospective studies are needed in the future to validate the reliability of these predictive factors and to further explore strategies for optimizing individualized treatment.

In conclusion, this study demonstrates that in chronic hepatitis B patients treated with interferon, lower baseline HBsAg levels, HBeAg negativity, female gender, and higher thyroid function are associated with an increased likelihood of HBsAg seroclearance, suggesting a better response to interferon therapy in these patients. These findings not only contribute to optimizing clinical treatment decisions but also offer new insights into achieving functional cure in chronic hepatitis B.