In this study, we recorded the changes of various indices before and after the use of belimumab in SLE patients, including the improvement of serological indices and disease activity and the reduction of urinary protein levels. This is consistent with the results of some previously published literature from abroad [12, 13]. In recent years, the concept of “Treat to Target” (T2T) [14, 15] has become established in the clinical treatment of SLE. Greater adoption of DORIS remission and LLDAS as T2T targets may help to overcome barriers to achieving T2T and lead to better clinical outcomes for more patients. Although DORIS remission is the recommended therapy goal for SLE, LLDAS is a more clinically achievable treatment goal with similar clinical efficacy to DORIS remission [14, 16]. The Asia Pacific Lupus Collaboration (APLC) proposed LLDAS as the minimum attainment status for SLE in 2016. In addition, after achieving LLDAS, patients should continue to receive treatment to maximize clinical benefit, and a study [17] also showed that achieving LLDAS and maintaining it for at least 2 years can significantly reduce the degree of organ damage. LLDAS and DORIS remissions are associated with slowing disease progression and a reduction in mortality. For example, Ugarte-Gil [18] et al. found a direct association between the proportion achieving DORIS remission or LLDAS and a reduction in disease damage accumulation. Data from this study showed that after 52 weeks of belimumab treatment, 55.4% of patients achieved LLDAS and 23.8% achieved DORIS remission. Of note, we found that patients who did not achieve LLDAS had a more active disease state at baseline and had a higher SLEDAI-2 K. Our results suggest that belimumab could play a role in helping patients achieve LLDAS and DORIS remission, slowing disease progression, and optimizing quality of life.

SLE is a chronic progressive disease, and assessment of disease activity is needed to guide clinical treatment in clinical work. SRI-4 can more sensitively reflect the treatment effect and disease change of patients [19, 20] and respond to the degree of disease control, and is particularly suitable for assessing the effect of drug treatment in SLE. Two multicenter, randomized, controlled trials (BLISS-52 and BLISS-76) showed that treatment with belimumab in combination with SoC significantly increased the SRI-4 response rate, reduced disease activity and severe relapses in SLE, and improved the quality of life of SLE patients [12, 21]. In our study, the SRI-4 response rate of patients in the active group increased to 79.8% at week 52 and disease activity was significantly reduced. Since SRI-4 is not applicable to patients with low disease activity, we chose SFI as an indicator of clinical relapse in the mild group. At week 52, 71.4% of patients in the mild group had no relapses, and the two patients who did relapse had a new rash and alopecia, respectively. However, the sample size of the mild group was too small, which is a limitation of this study and more data are required to validate our conclusions in the future.

LN, as a serious complication of SLE [22, 23], can cause kidney damage with different protein content in urine, edema and even kidney failure, which seriously endangers the health of patients. Some studies have shown that autoantibodies produced by B lymphocytes can form immune complexes, which in turn can lead to glomerulosclerosis and interstitial fibrosis. Sciascia et al. analyzed data from a large clinical trial and some case reports, suggesting that belimumab may play an effective role in the treatment of LN [24]. Of the 56 patients with LN, 47 had complete kidney biopsies data, with the most common pathologic type being LN type IV (38.3%), followed by type IV + V (31.9%), type V (17.0%) %) and type III LN (12.8%). We found that patients with LN treated with belimumab showed a significant reduction in 24-hour urine protein levels, an increase in albumin levels, and no significant change in serum creatinine levels compared to baseline, consistent with the results of a previous study agrees [25]. A retrospective study showed that belimumab combined with SoC treatment could significantly alleviate kidney damage and improve kidney function in patients with LN [26]. In this study, complete and partial renal remission were used as criteria for evaluating LN patients. At 52 weeks, the complete remission rate in LN patients was 73.2%, the partial remission rate was 16.1%, and in one case no response to treatment (did not achieve complete or partial response). After treatment with belimumab, the overall renal remission rate of patients was significantly higher, indicating that belimumab combined with SoC treatment can improve the degree of kidney injury in patients with LN.

The safety of belimumab in combination with SoC for the treatment of SLE has been demonstrated in many studies, with the probability of various adverse reactions being comparable to that of the placebo group [27, 28]. In our study, the incidence of adverse events was 14.9%. After symptomatic treatment, all patients returned to normal, showing that overall the use of belimumab treatment is well tolerated, but it is still necessary to focus on the occurrence of side effects (e.g. infections) and treat them in a timely manner treat. Furthermore, our study also documented the reasons for discontinuation in 18 patients treated with belimumab for less than 52 weeks (these patients were not counted in the 101 patients in the study): 6 patients were discontinued due to the COVID-19, 4 were lost to follow-up, 3 were discontinued due to ineffectiveness, 2 were discontinued due to pregnancy as well as 3 were discontinued due to financial burden.

However, this study still has some limitations that need to be addressed. First, this study is a single-center retrospective study with a small sample size and some orientations in patient enrollment, which may bias the results. Second, the follow-up period is short, which requires greater attention to the patient’s organ damage and treatment progress. Third, placebo-controlled trials are still needed, such as a comparison between patients treated with belimumab + SoC and those treated with SoC alone is necessary to adequately demonstrate its efficacy of the former. Therefore, multicenter clinical trials with a larger sample size and a longer follow-up period are needed to further validate the results. Moreover, we did not documented suicidal and depressive side effects of treatment with belimumab, which also needed special attention.