SYSTEMATIC REVIEW article

Front. Pharmacol., 07 December 2023

Sec. Inflammation Pharmacology

Volume 14 - 2023 | https://doi.org/10.3389/fphar.2023.1189142

Efficacy and safety of iguratimod in the treatment of rheumatic and autoimmune diseases: a meta-analysis and systematic review of 84 randomized controlled trials

  • 1. Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Graduate School of Peking Union Medical College, Nanjing, China

  • 2. People’s Hospital of Ningxiang City, Ningxiang, China

  • 3. Hunan University of Science and Technology, Xiangtan, China

  • 4. Key Laboratory of Hunan Province for Integrated Traditional Chinese and Western Medicine on Prevention and Treatment of Cardio-Cerebral Diseases, School of Integrated Chinese and Western Medicine, Hunan University of Chinese Medicine, Changsha, China

  • 5. Department of Nephrology, The Central Hospital of Shaoyang, Shaoyang, China

  • 6. The First Hospital of Hunan University of Chinese Medicine, Changsha, China

  • 7. Fudan University, Shanghai, China

  • 8. Department of Rehabilitation Medicine, Guangzhou Panyu Central Hospital, Guangzhou, China

  • 9. Department of Rheumatology and Immunology, The First Affiliated Hospital of Anhui Medical University, Anhui, China

Abstract

Objective: To evaluate efficacy and safety of iguratimod (IGU) in the treatment of rheumatic and autoimmune diseases.

Methods: Databases such as Pubmed, Embase, Sinomed were searched (as of July 2022) to collect randomized controlled trials (RCTs) of IGU in the treatment of rheumatic and autoimmune diseases. Two researchers independently screened the literature, extracted data, assessed the risk of bias of the included literature, and performed meta-analysis using RevMan 5.4 software.

Results: A total of 84 RCTs and 4 types of rheumatic and autoimmune diseases [rheumatoid arthritis (RA), ankylosing spondylitis (AS), primary Sjögren’s syndrome (PSS) and Autoimmune disease with interstitial pneumonia]. Forty-three RCTs reported RA and showed that IGU + MTX therapy can improve ACR20 (RR 1.45 [1.14, 1.84], p = 0.003), ACR50 (RR 1.80 [1.43, 2.26], p < 0.0000), ACR70 (RR 1.84 [1.27, 2.67], p = 0.001), DAS28 (WMD −1.11 [−1.69, −0.52], p = 0.0002), reduce ESR (WMD −11.05 [−14.58, −7.51], p < 0.00001), CRP (SMD −1.52 [−2.02, −1.02], p < 0.00001), RF (SMD −1.65 [−2.48, −0.82], p < 0.0001), and have a lower incidence of adverse events (RR 0.84 [0.78, 0.91], p < 0.00001) than the control group. Nine RCTs reported AS and showed that IGU can decrease the BASDAI score (SMD −1.62 [−2.20, −1.05], p < 0.00001), BASFI score (WMD −1.07 [−1.39, −0.75], p < 0.00001), VAS (WMD −2.01 [−2.83, −1.19], p < 0.00001), inflammation levels (decreasing ESR, CRP and TNF-α). Thirty-two RCTs reported PSS and showed that IGU can reduce the ESSPRI score (IGU + other therapy group: WMD −1.71 [−2.44, −0.98], p < 0.00001; IGU only group: WMD −2.10 [−2.40, −1.81], p < 0.00001) and ESSDAI score (IGU + other therapy group: WMD −1.62 [−2.30, −0.94], p < 0.00001; IGU only group: WMD −1.51 [−1.65, −1.37], p < 0.00001), inhibit the inflammation factors (reduce ESR, CRP and RF) and increase Schirmer’s test score (IGU + other therapy group: WMD 2.18 [1.76, 2.59], p < 0.00001; IGU only group: WMD 1.55 [0.35, 2.75], p = 0.01); The incidence of adverse events in IGU group was also lower than that in control group (IGU only group: RR 0.66 [0.48, 0.98], p = 0.01). Three RCTs reported Autoimmune disease with interstitial pneumonia and showed that IGU may improve lung function.

Conclusion: Based on current evidence, IGU may be a safe and effective therapy for RA, AS, PSS and autoimmune diseases with interstitial pneumonia.

Systematic Review Registration: (CRD42021289489).

1 Introduction

The pathogenesis of rheumatic immune diseases is complex, and it is an inflammatory disease that may lead to impaired immune system due to various reasons (involving the musculoskeletal system, joints and their surrounding soft tissues, etc.) (; ). In recent years, the prevalence of rheumatic immune diseases has been on the rise (), among which rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and ankylosing spondylitis (AS) are more common and have certain disability () ]. Meanwhile, with the progression of the disease, most patients may develop complications such as kidney, iris, skin, heart and other organ damage (van der Woude and van der Helm-van Mil, 2018; ). Especially in active disease, there may be radioactive progression, and severe cases may lead to joint deformity and even loss of self-care function in life (Otón and Carmona, 2019). Therefore, rheumatic immune diseases with high disease activity will generate a great economic burden for both society and patients (Otón and Carmona, 2019). The current treatments for rheumatic diseases and autoimmune diseases are precision medicine based on drugs (; Radu and Bungau, 2021), with the aim of controlling the progression of inflammation and reducing inflammatory damage (Winthrop, 2017; ). It mainly includes traditional synthetic DMARDs, biologics DMARDs and synthetic targeted DMARDs (). Among them, biological DMARDs can be divided into two categories: biological agents (bDMARDs) and synthetic targeted (tsDMARDs) (). bDMARDs include the tumor necrosis factor inhibitor class of adalimumab, infliximab, etanercept, and the IL-6 antagonist tocilizumab. tsDMARDs include the Janus kinase (JAK) inhibitor tofacitinib (Winthrop, 2017). Although the efficacy of the above drugs has been proven, their high prices make it impossible for patients in developing countries, including China, to benefit (). Studies have shown that patients in developed countries are also becoming increasingly prominent due to poor compliance and high recurrence rates related to medication problems (Tanaka, 2016; ). Traditional DMARDs are widely used in clinic because of their acceptable side effects and reasonable price. For example, methotrexate (MTX) is the most widely used DMARDs for the treatment of RA (Wang W. et al., 2018). Because of its effectiveness, acceptable side effects, and reasonable price, ACR recommends it as the first-choice drug in the initial treatment regimen for RA patients (). However, there are still about 30%–40% of patients who are insensitive to MTX treatment, have poor treatment effect, or fail to benefit from it because of side effects (). Strand et al. reported that the ACR50 of MTX in RA was 46%, and the ACR70 was 23% (Strand et al., 1999). According to multiple clinical trials, the combined use of DMARDs is one of the effective ways to improve the efficacy (; ; ).

Iguratimod (IGU) is a new type of small molecule DMARDs developed in Japan. As an immunomodulator, through immunomodulation, it reduces immune response, inhibits collagenous arthritis, and relieves the destruction of bone and cartilage tissue (; Mizutani et al., 2021). IGU can also inhibit the activity of nuclear factors, thereby inhibiting the production of inflammatory cytokines, IL-1, IL-6, IL-8, and TNF, and inhibiting the production of immunoglobulins to exert anti-inflammatory, anti-immune, and anti-inflammatory effects. (; Xie S. et al., 2020). Several studies have shown that IGU has good efficacy in rheumatic diseases and autoimmune diseases, such as improving RA, AS, systemic lupus erythematosus, IG4-RD, pulmonary interstitial disease, primary Sjögren’s syndrome (PSS), etc. (; Pu et al., 2021; Zeng et al., 2022a). In clinical practice, more and more rheumatologists use IGU to treat rheumatic and autoimmune diseases, but its efficacy and safety are still uncertain. Therefore, we collected randomized controlled trials (RCTs) of IGU in the treatment of rheumatic and autoimmune diseases in order to conduct a systematic review and meta-analysis of its efficacy and safety.

2 Materials and methods

2.1 Protocol

This systematic review and meta-analysis were conducted strictly in accordance with the protocol registered in PROSPERO (CRD42021289489) and PRISMA-guidelines (see Supplementary Materials) (Page et al., 2021).

2.2 Search criteria

2.2.1 Study design

All RCTs on IGU for rheumatic and autoimmune diseases were included. There are no restrictions on publication year, publication language, publication journal, etc.

2.2.2 Participants

Patients were diagnosed with any rheumatic and autoimmune diseases by accepted criteria.

2.2.3 Intervention methods

The experimental group was treated with IGU, which was administered orally. The course of treatment and the dose were not limited, and it could be combined or not combined with other therapies. The control group is therapy that does not contain IGU, including but not limited to placebo, conventional therapy, etc.

2.2.4 Outcomes

Outcomes are the disease activity indices (such as BASDAI and ACR20), inflammatory factor indicators (such as ESR, CRP, RF) and adverse events.

2.2.5 Exclusion criteria

1) Duplicate publications; 2) Unable to obtain full text or incomplete data; 3) Reviews, case reports, animal experiments, etc.,; 4) Retracted studies; 5) observational studies.

2.3 Search strategy

Pubmed, Wanfang Database, Web of Science, China National Knowledge Infrastructure (CNKI), Sinomed, VIP Database, Medline Complete, Embase were searched for literature on IGU for the treatment of rheumatic and autoimmune diseases. The retrieval time is from inception to 1 July 2022. We also searched ClinicalTrials.gov and Cochrane Library. The search strategy was shown in Supplementary Table S1.

2.4 Data collection and analysis

2.4.1 Literature screening and data extraction

Two researchers independently screened the title and abstract of the articles revealed from the search. Then, they screened the full text of the relevant articles based on search criteria. Finally, the two researchers reconciled the results and negotiated inconsistencies through discussions with all researchers (). Then two researchers independently extracted the basic information, medication regimen, course of treatment, and outcome indicators of eligible RCTs. For inconsistencies, the solution is the same as before.

2.4.2 Quality assessments

The risk of bias assessment of the included trials was independently performed by two investigators. The Cochrane Collaboration’s tool was used for assessing risk of bias (). The content of the evaluation mainly includes: 1) Whether the method of random allocation is described; 2) Whether the allocation concealment is sufficient; 3) Whether the blind method is used; 4) Whether the withdrawal from the experiment and the loss to follow-up are completely described; 5) Whether the outcome indicators are selectively reported; 6) Whether there are other factors that may affect the quality of the trial. According to the Cochrane Handbook, the above items were judged as “Yes” (low risk of bias), “No” (high risk of bias), and “Unclear” (unclear risk of bias) ().

2.5 Statistical analysis

Revman 5.4 software were utilized for meta-analysis (). For dichotomous variables data, use the risk ratio (RR). For continuous variables data, when the results of different experiments are expressed in the same unit of measurement, the weighted mean difference (WMD) is used; when the results of the experiments are expressed in different units of measurement, the standard mean difference (SMD) is used. Effect sizes were expressed as 95% confidence intervals (CI). To analyze the heterogeneity between results, the chi-square test was employed. If heterogeneity was deemed small (p > 0.1, I2<50%), the fixed-effects model was utilized for analysis. Otherwise, the random-effects model was used. STATA 15 was used to detect publication bias with the Egger method (for continuous variables) and Harbord methods (for dichotomous variables) for outcomes with RCTs ≥4. p > 0.1 is considered indicative of no publication bias. The level of evidence of efficacy indicators (such as ACR and BASFI) and adverse events was evaluated by the GRADE tool (), following the GRADE handbook (Schünemann et al., 2013).

3 Results

3.1 Literature search results

A total of 1,698 preliminary related literature were detected in this study, and a total of 1,594 literature that did not conform to the research type and content were excluded. After the primary screening, 104 records were obtained. According to the inclusion and exclusion criteria and the completeness of the literature information, 18 records were excluded from the second screening after reading the full text (; ; Okamura et al., 2015; Meng et al., 2016a; ; Yoshioka et al., 2016; Zhu et al., 2016; Wang, 2017; Wang et al., 2017; ; Wang X. et al., 2018; ; ; Shang et al., 2019; Suto et al., 2019; ; ; Xu et al., 2021), and 86 records [(; ; Tian and Tao, 2017; Qi et al., 2019; ; ; ; ; Xia et al., 2020; Xia et al., 2016; ; Zhao et al., 2016; Shi et al., 2015; Meng et al., 2015; ; Zhang, 2018; ; Mo et al., 2018; ; Xiong and GengGuanghui, 2020; Shang, 2014; Mo and Ma, 2015; Tian et al., 2020; Xu B. et al., 2015; Xu LM. et al., 2017; Yan and Wang, 2018; ; Meng et al., 2016b; Wang L. et al., 2019; Meng et al., 2017; ; Zhao and Hao, 2018; ; Xu YM. et al., 2015; ; Zhao et al., 2017a; ; Xie et al., 2018; Rao et al., 2014; Wang et al., 2022; ; Sun and Li, 2022; Wu et al., 2022; ; Qiu et al., 2016; Yuan et al., 2020; Pang et al., 2020; ; Xu et al., 2019; Zeng et al., 2016; ; ; ; ; ; Zhao, 2019; ; ; Zhang, 2019; ; Yu, 2020; Shao et al., 2020; ; Donghui, 2019; Zhang and Shen, 2019; ; Xie H. et al., 2020; ; ; Rao et al., 2022; ; Xu D. et al., 2017; Zhang et al., 2019; ; Wang Y. et al., 2019; Zhao, 2020; ; ; ; Yi, 2018; Zhuang, 2020; Xia et al., 2017; ; ; Zhuang et al., 2021; ; ) were finally included in the quantitative and qualitative analysis of the review. The literature screening process and results are shown in Figure 1.

FIGURE 1

3.2 Description of included trials

Two records (; ) came from the same RCT and were therefore recorded as Hara et al., 2014 (; ). Two records (; Xia et al., 2016) came from the same RCT and were therefore recorded as ; Xia et al. (2016). Therefore, 86 records actually involve 84 RCTs. In some RCTs, there were 2 experimental groups, and to match them, the control group was split into 2 equal parts with half the population each, and labeled as groups a and b (e.g., Xu et al., 2015a and Xu YM. et al., 2015). The included RCTs involved 4 rheumatic and autoimmune diseases (RA, AS, PSS and Autoimmune disease with interstitial pneumonia). The details of study characteristics are presented in Table 1.

TABLE 1

DiseaseStudySample sizeInterventionRelevant outcomesMean age (years)Duration
Trial groupControl groupTrial groupControl groupTrial groupControl group
RA18595a: IGU 25 mg Qd; b: 25 mg BidPlaceboAmerican college of rheumatology (ACR)20, ACR50, ACR70, Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), rheumatoid factor (RF), adverse eventsa: 48.05 ± 10.30; b: 46.98 ± 10.9347.46 ± 10.3024 weeks
Tian and Tao (2017)5858IGU 25 mg Bid + MTX 10 mg once or twice a weekMTX 10 mg once or twice a weekDisease activity score (DAS)28, ESR, CRP, adverse events52.6 ± 7.649.7 ± 8.424 weeks
Qi et al. (2019)4040IGU 25 mg Bid + MTX 7.5 mg once a week at the beginning, gradually increase to 10 mg within 4 weeksMTX 7.5 mg once a week at the beginning, Gradually increase to 10 mg within 4 weeksACR20, ACR50, ACR70, ESR, CRP, adverse events25–6524 weeks
16468IGU 25 mg Qd for the first 4 weeks of the extension period 25 mg Bid for the subsequent 20 weeks + MTX 6–8 mg once a weekMTX 6–8 mg once a week + placeboACR20, ACR50, ACR70, CRP, RF, DAS28, adverse events54.8 ± 9.953.5 ± 10.024 weeks
5151IGU 25 mg Bid + MTX 15 mg once a weekMTX 15 mg once a weekAdverse events74.16 ± 2.4274.32 ± 2.5215 weeks
2020IGU 25 mg BidMTX 10 mg once a weekDAS28, ACR20, adverse events47.3 ± 13.546.2 ± 15.824 weeks
326163a: IGU 25 mg for the first 4 weeks and 50 mg for the subsequent 20 weeks; b: IGU 25 mg BidMTX 10 mg/week for the first 4 weeks and 15 mg/week for the subsequent 20 weeksACR20, ACR50, ACR70, ESR, CRP, RF, adverse eventsa: 46.0 ± 10.6; b: 45.9 ± 10.447.2 ± 11.024 weeks
13264IGU 25 mg for the first 4 weeks and 50 mg for the subsequent 24 weeksplaceboCRP, ESR, adverse events57.5 ± 10.857.0 ± 10.828 weeks
Xia et al. (2020)5050IGU 25 mg Bid + MTX 7.5 mg once a week at the beginning, increase by 2.5 mg per week, with a final dose of 15 mgMTX 7.5 mg once a week at the beginning, increase by 2.5 mg per week, with a final dose of 15 mg + Tripterygium glycosides 1–1.5 mg/kgESR, CRP53.73 ± 2.7853.62 ± 2.4512 weeks
; Xia et al. (2016)10050a: IGU 25 mg Bid + MTX 10 mg once a week; b: IGU 25 mg BidMTX 10 mg once a weekESR, CRP46.63 ± 10.6124 weeks
Zhao et al. (2016)6030a: IGU 25 mg Bid + MTX 10 mg once a week; b: IGU 25 mg BidMTX 15 mg once a weekACR20, ACR50, ACR70, adverse eventsa: 30.1 ± 2.4; b: 29.3 ± 2.728.1 ± 3.424 weeks
Shi et al. (2015)3030IGU 25 mg Bid + MTX 10 mg once a week at the beginning; 12.5 mg twice a week after 4 weeksMTX 10 mg once a week at the beginning; 12.5 mg twice a week after 4 weeksDAS28, ESR, CRP, ACR20, ACR50, ACR70, adverse events48.9 ± 12.248.4 ± 10.224 weeks
Meng et al. (2015)3333IGU 25 mg Bid + MTX 10 mg once a weekMTX 10 mg once a week + Leflunomide 10 mg QdDAS28, ACR20, ACR50, ACR70, adverse events44.2 ± 20.541.7 ± 22.816 weeks
3030IGU 25 mg Bid + MTX 10 mg once a weekMTX 10 mg once a week + Leflunomide 20 mg QdDAS28, adverse events53.10 ± 12.9054.60 ± 11.8812 weeks
Zhang (2018)6060IGU 25 mg QdMTX 10 mg once a week + Leflunomide 20 mg QdACR20, CRP, ESR, RF, adverse events46.35 ± 18.1924 weeks
4440IGU 25 mg Qd + MTX 7.5–10 mg once a weekMTX 7.5–10 mg once a week + Tripterygium glycosides 20 mg BidDAS28, ESR, CRP, adverse events60–7760–8212 weeks
Mo et al. (2018)3030IGU 25 mg Bid + MTX 10 mg once a weekMTX 10 mg once a week + Tripterygium glycosides 20 mg BidDAS28, ESR, CRP, CCP, RF, adverse events45 ± 11.643.3 ± 10.2512 weeks
3030IGU 25 mg Bid + MTX 10 mg once a week at the beginning, gradually increase to 12.5 mg within 4 weeksMTX 10 mg once a week at the beginning, gradually increase to 12.5 mg within 4 weeksESR, CRP, DAS28, adverse events48.9 ± 12.248.4 ± 10.224 weeks
Xiong and GengGuanghui (2020)5151IGU 25 mg Bid + MTX 10 mg once a week at the beginning; 12.5 mg twice a week after 2 weeks; 15 mg once a week after 4 weeksMTX 10 mg once a week at the beginning; 12.5 mg twice a week after 2 weeks; 15 mg once a week after 4 weeksAdverse events48.21 ± 6.0448.33 ± 5.9324 weeks
Shang (2014)2020IGU 25 mg BidEtoricoxib 60 mg QdAdverse events43.73 ± 3.6245.73 ± 3.5612 weeks
Mo and Ma (2015)3030IGU 25 mg Bid + MTX 15 mg once a weekMTX 15 mg once a weekACR20, ACR50, ACR70, ESR, CRP, RF, adverse events31.8 ± 8.531.9 ± 8.612 weeks
Tian et al. (2020)120120IGU 25 mg Bid + MTX 10 mg once a weekMTX 10 mg once a week + Leflunomide 20 mg QdDAS28, ESR, CRP, RF, adverse events50 ± 1049 ± 1152 weeks
Xu et al. (2015a)7238a: IGU 25 mg Bid + MTX 7.5–20 mg once a week; b: IGU 25 mg BidMTX 7.5–20 mg once a weekESR, CRP, RF, adverse eventsa: 46.10 ± 17.09; b: 44.71 ± 9.3243.28 ± 10.4648 weeks
Xu et al. (2017a)4241IGU 25 mg Bid + MTX 7.5–20 mg once a weekMTX 7.5–20 mg once a weekDAS28, ESR, CRP46.34 ± 2.2946.19 ± 2.5748 weeks
Yan and Wang (2018)3535IGU 25 mg Bid + MTX 10 mg once a weekMTX 10 mg once a weekAdverse events56 ± 756 ± 724 weeks
3837IGU 25 mg Bid + MTX 10 mg once a week at the beginning; 12.5 mg once a week after 2 weeks; 15 mg once a week after 4 weeksMTX 10 mg once a week at the beginning; 12.5 mg once a week after 2 weeks; 15 mg once a week after 4 weeksDAS2849.0 ± 10.148.7 ± 10.224 weeks
Meng et al. (2016b)3030IGU 25 mg Bid + MTX 15 mg once a weekMTX 15 mg once a weekDAS28, adverse events41.6 ± 20.345.1 ± 19.216 weeks
Wang et al. (2019a)4746IGU 25 mg Bid + MTX 15 mg once a weekMTX 15 mg once a weekCRP, RF, ESR, DAS2848.13 ± 6.4047.83 ± 6.3724 weeks
Meng et al. (2017)6060IGU 25 mg Bid + MTX 10 mg once a weekMTX 10 mg once a weekRF, CRP, adverse events64.83 ± 9.4164.31 ± 8.2212 weeks
5858IGU 25 mg Bid + MTX 10 mg once a weekMTX 10 mg once a weekDAS28, ESR, CRP, RF42.31 ± 13.7841.87 ± 13.9424 weeks
Zhao and Hao (2018)3636IGU 25 mg Bid + MTX 7.5 mg once a weekMTX 7.5 mg once a weekDAS28, CRP, adverse events47.20 ± 3.4050.80 ± 4.1012 weeks
2013IGU 25 mg Bid + MTX 10 mg once a weekMTX 10 mg once a week + Adalimumab 40 mg once every 2 weeksDAS2858 ± 1155 ± 1124 weeks
Xu et al. (2015b)3028IGU 25 mg Bid + MTX 10 mg once a weekMTX 10 mg once a weekRF, CRP, ESR, DAS28, adverse events56 ± 1251 ± 1324 weeks
6060IGU 25 mg Bid + MTX 10 mg once a weekMTX 10 mg once a weekCRP, adverse events45.7 ± 5.445.9 ± 4.824 weeks
Zhao et al. (2017a)6333a: IGU 25 mg Bid; b: IGU 25 mg Bid + MTX 10 mg once a weekMTX 10 mg once a weekACR20, ACR50, ACR70, DAS28, ESR, CRP, RF, adverse eventsa: 46.46 ± 11.01; b: 45.97 ± 10.7546.31 ± 10.8924 weeks
5931a: IGU 25 mg Bid + MTX 10 mg once a week; b: IGU 25 mg BidMTX 10 mg once a week + Leflunomide 20 mg QdDAS28, ESR, CRP, RF, adverse events47.23 ± 15.6248 weeks
Xie et al. (2018)3939IGU 25 mg Bid + MTX 10 mg once a week at the beginning; 12.5 mg twice a week after 2 weeks; 15 mg once a week after 4 weeksMTX 10 mg once a week at the beginning; 12.5 mg twice a week after 2 weeks; 15 mg once a week after 4 weeksDAS28, adverse events62.89 ± 4.5762.74 ± 3.9616 weeks
Rao et al. (2014)6030a: IGU 25 mg Bid; b: IGU 25 mg QdMTX 10 mg once a weekACR20, ACR50, ACR7042.6 ± 5.212 weeks
Wang et al. (2022)6060IGU 25 mg Bid + MTX 10 mg once a weekMTX 10 mg once a weekCRP, adverse events54 ± 1455 ± 1312 weeks
6060IGU 25 mg Bid + MTX 7.5 mg once a weekMTX 7.5 mg once a weekDAS28, CRP, ESR, RF59.4 ± 7.860.1 ± 9.712 weeks
Sun and Li (2022)4343IGU 25 mg Bid + MTX 10 mg once a weekMTX 10 mg once a weekAdverse events49.05 ± 4.3248.96 ± 5.2424 weeks
Wu et al. (2022)5858IGU 25 mg Bid + MTX 10 mg once a week + Tripterygium wilfordii polyglycosides 50 mg for the first time and 20 mg Qd after 3daysMTX 10 mg once a week + Tripterygium wilfordii polyglycosides 50 mg for the first time and 20 mg Qd after 3daysDAS28, CRP, ESR, RF61.48 ± 4.3662.73 ± 4.5818 weeks
52104IGU 25 mg Bid + Tripterygium glycosides 1.5 mg/(kg·d)a: Prednisone + Sulfasalazine; b: Tripterygium glycosides 1.5 mg/(kg·d)Forced vital capacity (FVC), Forced expiratory volume in 1 s (FEV1), total lung capacity (TLC), CRP, RF, adverse events54.7 ± 5.1a: 55.6 ± 4.9; b: 54.1 ± 5.424 weeks
ASQiu et al. (2016)1818Iguratimod 25 mg BidNSAIDs + DMARDsESR, Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI), visual analogue scale (VAS), back pain score, adverse events37.3 ± 7.034.5 ± 9.324 weeks
Yuan et al. (2020)4139Iguratimod 25 mg Bid + Etoricoxib tablets 60 mg Qd. + ibuprofen 300 mg Tid. + methotrexate 15 mg once a weekEtoricoxib tablets 60 mg Qd. + ibuprofen 300 mg Tid. + methotrexate 15 mg once a weekVAS, CRP, ESR, adverse events39.28 ± 5.3040.08 ± 5.6712 weeks
Pang et al. (2020)3939Iguratimod 25 mg Bid + Etanercept 25 mg tiwce a weekEtanercept 25 mg tiwce a weekESR, CRP, BASDAI24.85 ± 4.1825.01 ± 4.2912 weeks
2424Iguratimod 25 mg Bid + Sulfasalazine 1 g Bid. + methotrexate 10 mg once a week + NSAIDsSulfasalazine 1 g Bid. + methotrexate 10 mg once a week + NSAIDsBASDAI, BASFI, VAS, adverse events32.71 ± 8.8028.21 ± 6.6924 weeks
Xu et al. (2019)2121Iguratimod 25 mg Bid + Celecoxib 0.2 g QdSulfasalazine 1 g Bid. + Celecoxib 0.2 g QdBASDAI, BASFI, VAS, ESR, CRP, adverse events35.1 ± 10.334.3 ± 9.524 weeks
Zeng et al. (2016)2525Iguratimod 25 mg Bid + Meloxicam 7.5 mg QdSulfasalazine 0.75 g Tid. + Meloxicam 7.5 mg QdBASDAI, CRP, adverse events38 ± 1240 ± 1024 weeks
4825Iguratimod 50 mg Qd + NSAIDsNSAIDs + PlaceboBASDAI, BASFI, CRP, ESR, adverse events31.38 ± 7.3630.28 ± 5.9424 weeks
4343Iguratimod 25 mg Bid + Sulfasalazine 1 g Bid + Celecoxib 200 mg BidSulfasalazine 1 g Bid + Celecoxib 200 mg BidBASDAI, VAS, CRP, ESR, adverse events28.52 ± 9.4327.87 ± 8.0512 weeks
3030Iguratimod 25 mg Bid + Sulfasalazine 0.5–1 g Bid + Thalidomide 50–200 mg QnSulfasalazine 0.5–1 g Bid + Thalidomide 50–200 mg QnBASDAI31.24 ± 4.7130.01 ± 4.6824 weeks
PS4040Iguratimod 25 mg BidPrednisone 8 mg Qd + HCQ 200 mg BidRF, Adverse events66.72 ± 4.3466.51 ± 4.2312 weeks
2525Iguratimod 25 mg BidPrednisone 5–10 mg Qd + HCQ 200 mg Bid + Bromoethylsine 16 mg BidEULAR SS Patient Reported Index (ESSPRI), EULAR SS disease activity index (ESSDAI), Schirmer’s test, Adverse events29.3 ± 9.732.5 ± 11.512 weeks
Zhao (2019)4141Iguratimod 25 mg BidPrednisone 8 mg Qd + HCQ 200 mg BidRF, ESR, Adverse events55.51 ± 6.5254.52 ± 6.5412 weeks
4848Iguratimod 25 mg Bid + HCQ 0.2 g BidHCQ 0.2 g BidESR, RF, adverse events45.52 ± 7.4844.24 ± 8.3212 weeks
2323Iguratimod 25 mg BidPrednisone 8 mg Qd + HCQ 200 mg BidESSPRI, ESR, Adverse events46.29 ± 1.2446.38 ± 1.3712 weeks
Zhang (2019)6060Iguratimod 25 mg Bid + Methylprednisolone 8 mgMethylprednisolone 8 mg Qd + HCQ 200 mg BidESSPRI, ESSDAI, Schirmer’s test49.43 ± 3.7412 weeks
4343Iguratimod 25 mg BidMethylprednisolone 8 mg Qd + HCQ 200 mg BidESSPRI, ESSDAI, ESR, RF, adverse events50.47 ± 9.1150.47 ± 9.1116 weeks
Yu (2020)3838Iguratimod 25 mg BidMethylprednisolone 8 mg Qd + HCQ 200 mg BidESR, RF41.18 ± 3.3641.14 ± 3.3912 weeks
Shao et al. (2020)4422Iguratimod 25 mg BidPlaceboESSPRI, ESR, ESSDAI, Adverse events49.5 ± 12.348.2 ± 11.524 weeks
6262Iguratimod 25 mg Bid + Total Glucosides of Paeony 0.6 g Tid + HCQ 0.2 g BidTotal Glucosides of Paeony 0.6 g Tid + HCQ 0.2 g BidESSPRI, ESSDAI, ESR, RF68.02 ± 3.0268.50 ± 3.0512 weeks
Donghui (2019)3030Iguratimod 25 mg Bid + Methylprednisolone 8 mgMethylprednisolone 8 mg Qd + HCQ 200 mg BidESR, adverse events46.9 ± 4.246.5 ± 4.312 weeks
Zhang and Shen (2019)4343Iguratimod 25 mg Bid + Methylprednisolone 8 mgMethylprednisolone 8 mg Qd + HCQ 200 mg BidESSPRI, ESSDAI, ESR, RF, Schirmer’s test, adverse events40.35 ± 9.4141.03 ± 10.0112 weeks
3030Iguratimod 50 mg QdPrednisone 8 mg Qd + HCQ 200 mg BidRF, ESR, Adverse events45.13 ± 12.1146.33 ± 13.7412 weeks
Xie et al. (2020b)3838Iguratimod 25 mg Bid + Total Glucosides of Paeony 0.6 g Tid + HCQ 0.2 g BidTotal Glucosides of Paeony 0.6 g Tid + HCQ 0.2 g BidESR, CRP, Schirmer’s test, Adverse events57.3 ± 7.9256.8 ± 8.4424 weeks
2525Iguratimod 50 mg QdPrednisone 10 mg, hydroxychloroquine (HCQ) 400 mg, new hydrochloride bromine ethyl QdEULAR Sjögren’s syndrome patient-reported index (ESSPRI), ESSDAI, Schirmer’s test, Adverse events29.3 ± 9.732.5 ± 11.512 weeks
3030Iguratimod 25 mg BidMethylprednisolone 8 mg Qd + HCQ 200 mg Bid + Leflunomide 50 mg QdESSPRI, ESSDAI, RF, ESR, Adverse events43 ± 2143 ± 1012 weeks
Rao et al. (2022)4343Iguratimod 25 mg BidMethylprednisolone 4 mg Qd + HCQ 200 mg BidSchirmer’s test, ESR, RF51.8 ± 10.350.1 ± 9.912 weeks
2020Iguratimod 25 mg Bid + HCQ 100 mg Bid + Prednisone 5 mg BidHCQ 100 mg Bid + Prednisone 5 mg BidESSPRI, ESSDAI, ESR, RF, Schirmer’s test, adverse events66.15 ± 3.7166.31 ± 3.9812 weeks
Xu et al. (2017b)4747Iguratimod 25 mg BidPrednisone 8 mg Qd + HCQ 200 mg BidESSPRI, ESSDAI, ESR, RF, Schirmer’s test44.5 ± 13.245.3 ± 13.112 weeks
Zhang et al. (2019)100100Iguratimod 25 mg BidPrednisone + HCQ + olfactionFVC, maximum mid-expiratory flow (MMF), ESR, adverse events30.68 ± 3.5131.00 ± 3.6020 weeks
4040Iguratimod 25 mg BidPrednisone 8 mg Qd + HCQ 200 mg BidESR, RF, adverse events43.6 ± 10.545.2 ± 12.912 weeks
Wang et al. (2019b)3232Iguratimod 25 mg Bid + Total Glucosides of Paeony 0.6 g Bid + HCQ 0.1 g BidTotal Glucosides of Paeony 0.6 g Bid + HCQ 0.1 g BidESSPRI, ESSDAI, Schirmer’s test, ESR, RF, Adverse events66.8 ± 7.765.3 ± 8.212 weeks
Zhao (2020)2525Iguratimod 25 mg Bid + Basic therapyHCQ 200 mg Bid + Basic therapyESR, RF, adverse events45.3 ± 2.845.7 ± 2.8Unkown
3030Iguratimod 25 mg Bid + Methylprednisolone 8 mgMethylprednisolone 8 mg Qd + HCQ 200 mg BidESSDAI, ESSPRI, ESR, CRP, adverse events45.16 ± 6.3740.15 ± 6.6516 weeks
3434Iguratimod 25 mg BidPrednisone 8 mg Qd + HCQ 200 mg BidESSPRI, RF, ESR, Adverse events40.05 ± 3.1640.02 ± 3.1512 weeks
2422Iguratimod 25 mg Bid + Chere Cunjing GranulesChere Cunjing Granules (Traditional Chinese Medicine)ESSPRI, ESSDAI, ESR, CRP, adverse events45.95 ± 11.5248.92 ± 11.5312 weeks
Yi (2018)2020Iguratimod 25 mg Bid + Total Glucosides of Paeony 0.6 g Tid + HCQ 0.2 g BidTotal Glucosides of Paeony 0.6 g Tid + HCQ 0.2 g BidESR, CRP, Adverse events56.87 ± 2.5656.23 ± 2.8612 weeks
Zhuang (2020)3434Iguratimod 25 mg Bid + Methylprednisolone 8 mgMethylprednisolone 8 mg Qd + HCQ 200 mg BidESR, RF36.48 ± 1.2536.51 ± 1.1912 weeks
Xia et al. (2017)5050Iguratimod 25 mg Bid + MethylprednisoloneHCQ 200 mg Bid + MethylprednisoloneESR, RF42.13 ± 9.9742.08 ± 9.6512 weeks
4242Iguratimod 25 mg BidMethylprednisolone 8 mg Qd + HCQ 200 mg BidESSPRI, adverse events40.97 ± 10.2441.56 ± 10.212 weeks
4040Iguratimod 25 mg Bid + Total Glucosides of Paeony 0.6 g Tid + HCQ 200 mg Bid + methylprednisolone 8 mg QdTotal Glucosides of Paeony 0.6 g Tid + HCQ 200 mg Bid + methylprednisolone 8 mg QdESSDAI, ESSPRI, ESR, RF, adverse events44.05 ± 8.8243.68 ± 8.7512 weeks
Zhuang et al. (2021)1010Iguratimod 25 mg Bid + Prednisone 5–10 mg TidCyclophosphamide + Prednisone 5–10 mg TidDispersive carbon monoxide (DLCO), 6-min walk test (6MWT), CRP, ESR, RF, adverse events45.69 ± 2.8045.31 ± 2.7824 weeks

The characteristics of the included studies.

3.3 Risk of bias assessments

The summary and graph of risk of bias ware shown in Figures 2, 3.

FIGURE 2

FIGURE 3

3.3.1 Sequence generation and allocation concealment

Fifty RCTs described detailed random sequence generation methods and were therefore assessed as low risk of bias, whereas the remainder were assessed as unclear risk of bias. , , Tian et al. (2020), Zhao et al. (2017a), ) and Shao et al. (2020) described methods of allocation concealment and was therefore assessed as low risk of bias, whereas the remainder were assessed as unclear risk of bias.

3.3.2 Blinding

Zeng et al. (2016), , and Donghui (2019) reported the use of blinding in their RCTs, but did not provide sufficient details about the implementation process, resulting in an unclear risk of bias assessment. Of the total 84 RCTs, 19 reported blinding of participants, and 18 reported blinding of assessors, indicating a low risk of bias. The remaining RCTs were assessed as high risk of bias because blinding was not described and outcomes included subjectively assessed outcomes.

3.3.3 Incomplete outcome data and selective reporting

Zhang (2018) and SShao et al. (2020) had incomplete outcomes and were therefore assessed as high risk of bias. There was not enough evidence to prove whether there were incomplete outcomes in , Xia et al. (2016), , Zhao et al. (2017a) and , so they were assessed as unknown risk of bias. The remaining RCTs did not have incomplete outcomes and were therefore assessed as low risk of bias.

Mo et al. (2018) did not report all data planned in the methodology and was therefore assessed as high risk of bias. The remaining RCTs did not have selective reports and were therefore assessed as low risk of bias.

3.3.4 Other potential bias

No other sources of bias were identified in any of the RCTs, indicating a low risk of bias from other sources.

3.4 IGU for RA

3.4.1 RA remission rate

ACR20, ACR50 and ACR70 were used to represent RA remission rate. According to the medication of the IGU group, it is divided into IGU + MTX subgroup and IGU only subgroup.

For ACR20, the heterogeneity test showed that some subgroups had high heterogeneity (IGU + MTX subgroup: p = 0.005, I2 = 68%; IGU only subgroup: p = 0.20, I2 = 27%), and a random effect model was used. The meta-analysis findings indicate that the IGU + MTX group had a significantly lower ACR20 compared to the control group (RR 1.45 [1.14, 1.84], p = 0.003; random-effect model). However, there was no significant difference in ACR20 between the IGU-only group and the control group (RR 0.99 [0.87, 1.13], p = 0.94; random-effect model) (Figure 4). The results of publication bias test showed that it was less likely to have publication bias in IGU + MTX subgroup (p = 0.313) and IGU only subgroup (p = 0.396).

FIGURE 4

For ACR50, the heterogeneity test showed that the heterogeneity was low (IGU + MTX subgroup: p = 0.44, I2 = 0%; IGU only subgroup: p = 0.14, I2 = 36%), and a fixed effect model was used. The meta-analysis findings indicate that the IGU + MTX group had a lower ACR50 compared to the control group (RR 1.80 [1.43, 2.26], p < 0.00001; fixed-effect model). However, there was no significant difference between the IGU only group and the control group (RR 0.94 [0.79, 1.12], p = 0.48; fixed-effect model) (Figure 5). The results of publication bias test showed that it was less likely to have publication bias in IGU + MTX subgroup (p = 0.433) and IGU only subgroup (p = 0.245).

FIGURE 5

For ACR70, the heterogeneity test showed that some subgroups had high heterogeneity (IGU + MTX subgroup: p = 0.74, I2 = 0%; IGU only subgroup: p = 0.02, I2 = 58%), and a random effect model was used. The findings of the meta-analysis indicate that the IGU + MTX group had a lower ACR70 than the control group (RR 1.84 [1.27, 2.67], p = 0.001; random effect model), while the difference between the IGU only group and the control group did not reach statistical significance (RR 1.51 [0.79, 2.86], p = 0.21; random effect model) (Figure 6). The results of publication bias test showed that it was less likely to have publication bias in IGU + MTX subgroup (p = 0.193) and IGU only subgroup (p = 0.230).

FIGURE 6

3.4.2 DAS28

According to the medication of the IGU group, it is divided into IGU + MTX subgroup and IGU only subgroup. The heterogeneity test showed that the heterogeneity was high (IGU + MTX subgroup: p < 0.00001, I2 = 99%; IGU only subgroup: p < 0.00001, I2 = 98%), and a random effect model was used. According to the meta-analysis results, the IGU + MTX group showed a significant decrease in DAS28 compared to the control group (WMD −1.11 [−1.69, −0.52], p = 0.0002; random effect model). However, the difference between the IGU only group and control group was not statistically significant (WMD −0.30 [−0.94, 0.33], p = 0.35; random effect model) (Figure 7). The results of publication bias test showed that it may be likely to have publication bias in IGU + MTX subgroup (p = 0.080); but was less likely in and IGU only subgroup (p = 0.122).

FIGURE 7

3.4.3 Inflammatory factor

Inflammatory factors include CRP, ESR and RF. According to the medication of the IGU group, it is divided into IGU + MTX subgroup, IGU only subgroup and IGU + Tripterygium Extract subgroup.

For CRP, the heterogeneity test showed that the heterogeneity was high (IGU + MTX subgroup: p < 0.00001, I2 = 95%; IGU only subgroup: p < 0.00001, I2 = 96%; IGU + Tripterygium Extract subgroup: p < 0.00001, I2 = 96%), and a random effect model was used. The meta-analysis results show that compared with the control group, the CRP in the IGU + MTX group, IGU only subgroup and IGU + Tripterygium Extract subgroup was lower (Figure 8).

FIGURE 8

For ESR, the heterogeneity test showed that the heterogeneity was high (IGU + MTX subgroup: p < 0.00001, I2 = 93%; IGU only subgroup: p < 0.00001, I2 = 96%; IGU + Tripterygium Extract subgroup: p < 0.00001, I2 = 96%), and a random effect model was used. The meta-analysis results show that compared with the control group, the ESR in the IGU + MTX group (WMD −11.05 [−14.58, −7.51], p < 0.00001; random effect model) and IGU + Tripterygium Extract group was lower (WMD −8.15 [−9.25, −7.05], p < 0.00001; random effect model), while its difference between IGU only group and control group was of no statistical significance (WMD −6.31 [−12.91, 0.29], p = 0.06; random effect model) (Figure 9).

FIGURE 9

For RF, the heterogeneity test showed that the heterogeneity was high (IGU + MTX subgroup: p < 0.00001, I2 = 97%; IGU only subgroup: p < 0.00001, I2 = 94%; IGU + Tripterygium Extract subgroup: p = 0.89, I2 = 0%), and a random effect model was used. The meta-analysis results indicate that compared with the control group, the RF in the IGU + MTX group (SMD −1.65 [−2.48, −0.82], p < 0.0001; random effect model) and IGU + Tripterygium Extract group were significantly lower (SMD −1.34 [−1.61, −1.07], p < 0.00001; random effect model). However, there was no significant difference between the IGU only group and control group (SMD −0.37 [−1.00, 0.26], p = 0.25; random effect model) (Figure 10).

FIGURE 10

3.4.4 Adverse events

According to the medication of the IGU group, it is divided into IGU + MTX subgroup, IGU only subgroup and IGU + Tripterygium Extract subgroup. The heterogeneity test showed that the heterogeneity was high (IGU + MTX subgroup: p = 0.64, I2 = 0%; IGU only subgroup: p = 0.003, I2 = 59%; IGU + Tripterygium Extract subgroup: p = 0.47, I2 = 0%), and a random effect model was used. The meta-analysis results show that compared with the control group, the adverse events in the IGU + MTX group was lower (RR 0.84 [0.78, 0.91], p < 0.00001; random effect model), while its difference between IGU only group and control group (RR 1.18 [0.89, 1.56], p = 0.26; random effect model), and between IGU + Tripterygium Extract and control group was of no statistical significance (RR 1.10 [0.69, 1.77], p = 0.69; random effect model) (Figure 11). The results of publication bias test showed that it was less likely to have publication bias in IGU + MTX subgroup (p = 0.443) and in IGU only subgroup (p = 0.474).

FIGURE 11

3.4.5 Quality of evidence

Only IGU + MTX and IGU only subgroups met the requirements of publication bias detection and evidence quality assessments.

According to the GRADE handbook, the evidence of IGU + MTX subgroup was judged to be moderate to very low (Table 2). The evidence of IGU only subgroup was judged to be moderate to low (Table 3).

TABLE 2

OutcomesIllustrative comparative risks* (95% CI)Relative effect (95% CI)No of participants (studies)Quality of the evidence (GRADE)Comments
Assumed riskCorresponding risk
Control
ACR20 - IGU + MTXStudy populationRR 1.45 (1.14–1.84)620 (7 studies)⊕⊕⊝⊝ lowa,b
481 per 1,000698 per 1,000 (548–885)
Moderate
475 per 1,000689 per 1,000(541–874)
ACR50 - IGU + MTXStudy populationRR 1.8 (1.43–2.26)620 (7 studies)⊕⊕⊕⊝ moderatea,b
269 per 1,000484 per 1,000 (385–608)
Moderate
325 per 1,000585 per 1,000 (465–734)
ACR70 - IGU + MTXStudy populationRR 1.84 (1.27–2.67)620 (7 studies)⊕⊕⊕⊝ moderatea,b
129 per 1,000237 per 1,000 (164–344)
Moderate
150 per 1,000276 per 1,000 (190–401)
DAS28 - IGU + MTXThe mean DAS28-IGU + MTX in the intervention groups was 1.11 lower (1.69–0.52 lower)1,567 (20 studies)⊕⊝⊝⊝ very lowa,b,c
AEs - IGU + MTXStudy populationRR 0.84 (0.78–0.91)2,254 (25 studies)⊕⊕⊕⊝ moderatea
283 per 1,000237 per 1,000 (220–257)
Moderate
179 per 1,000150 per 1,000 (140–163)

Evidence quality of IGU for RA in IGU + MTX subgroup.

*The basis for the assumed risk (e.g., the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).

CI: confidence interval; RR: Risk ratio.

GRADE, working group grades of evidence.

High quality: Further research is very unlikely to change our confidence in the estimate of effect.

Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.

Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.

Very low quality: We are very uncertain about the estimate.

a

Downgraded one level due to serious risk of bias (random sequence generation, allocation concealment, blinding, incomplete outcomes) and most of the data comes from the RCTs, with moderate risk of bias.

b

Downgraded one level due to the probably substantial heterogeneity.

c

Downgraded one level due to potential publication bias.

TABLE 3

OutcomesIllustrative comparative risks* (95% CI)Relative effect (95% CI)No of participants (studies)Quality of the evidence (GRADE)Comments
Assumed riskCorresponding risk
Control
ACR20 - IGU onlyStudy populationRR 0.99 (0.87–1.13)1,429 (10 studies)⊕⊕⊕⊝ moderatea
471 per 1,000467 per 1,000 (410–533)
Moderate
500 per 1,000495 per 1,000 (435–565)
ACR50 - IGU onlyStudy populationRR 0.94 (0.79–1.12)1,274 (8 studies)⊕⊕⊕⊝ moderatea
272 per 1,000256 per 1,000 (215–305)
Moderate
200 per 1,000188 per 1,000 (158–224)
ACR70 - IGU onlyStudy populationRR 1.51 (0.79–2.86)1,274 (8 studies)⊕⊕⊝⊝ lowa,b
121 per 1,000182 per 1,000 (95–345)
Moderate
50 per 1,00076 per 1,000 (40–143)
DAS28 - IGU onlyThe mean DAS28-IGU only in the intervention groups was 0.3 lower (0.94 lower to 0.33 higher)432 (6 studies)⊕⊕⊝⊝ lowa,b
AEs - IGU onlyStudy populationRR 1.18 (0.89–1.56)1887 (14 studies)⊕⊕⊝⊝ lowa,b
269 per 1,000317 per 1,000 (239–419)
Moderate
171 per 1,000202 per 1,000 (152–267)

Evidence quality of IGU for RA in IGU only subgroup.

a

Downgraded one level due to serious risk of bias (random sequence generation, allocation concealment, blinding, incomplete outcomes) and most of the data comes from the RCTs, with moderate risk of bias.

b

Downgraded one level due to the probably substantial heterogeneity.

3.5 IGU for AS

3.5.1 BASDAI

Eight RCTs used BASDAI as an assessment tool to evaluate the effectiveness of IGU in improving AS. The included studies showed high heterogeneity, with p < 0.00001 and I2 = 86%, and thus a random effects model was used for analysis. The meta-analysis results showed that the IGU group had a significantly lower BASDAI score compared to the control group (SMD −1.62 [−2.20, −1.05], p < 0.00001; random effect model) (Figure 12). The results of publication bias test showed that it was less likely to have publication bias (p = 0.302).

FIGURE 12

3.5.2 BASFI

Four RCTs were included in the meta-analysis, all of whom were assessed using BASFI to evaluate the improvement of AS. The heterogeneity test showed low heterogeneity, with p = 0.54 and I2 = 0%, indicating that a fixed effects model was appropriate for analysis. The results of the meta-analysis indicated that the IGU group had a significantly lower BASFI score compared to the control group (WMD −1.07 [−1.39, −0.75], p < 0.00001; fixed effect model) (Figure 13). The results of publication bias test showed that it was less likely to have publication bias (p = 0.254).

FIGURE 13

3.5.3 VAS

Four RCTs were used to evaluate the effect of IGU on the improvement of AS through VAS, with a total of 137 patients in the IGU group and 135 patients in the control group. The heterogeneity test showed significant heterogeneity with p < 0.00001 and I2 = 95%, indicating the use of a random effects model for analysis. The meta-analysis results indicated a significant reduction in the VAS score for the IGU group compared to the control group (WMD −2.01 [−2.83, −1.19], p < 0.00001; random effects model) (Figure 14). The results of publication bias test showed that it may be likely to have publication bias (p = 0.071).

FIGURE 14

3.5.4 Inflammatory factor

3.5.4.1 Inflammatory factors include ESR, CRP and TNF-α.

Six RCTs were included in the meta-analysis to evaluate the improvement of AS using ESR. High heterogeneity was observed (p < 0.00001, I2 = 90%), and therefore, a random effects model was used for the analysis. The results of the meta-analysis showed that the IGU group had a significantly lower ESR compared to the control group (WMD −10.01 [−14.72, −5.29], p < 0.0001; random effect model) (Figure 15).

FIGURE 15

Six RCTs were included in the analysis of CRP to evaluate the improvement of AS. The heterogeneity test indicated high heterogeneity (p < 0.00001, I2 = 98%), thus a random effects model was utilized for the analysis. The results of the meta-analysis demonstrated that IGU significantly decreased CRP levels compared to the control group (WMD −7.90 [−12.01, −3.80], p < 0.00001; random effect model) (Figure 16).

FIGURE 16

Three RCTs evaluated the effects of IGU on TNF-α levels in the treatment of AS. Significant heterogeneity was detected by the heterogeneity test (p < 0.00001, I2 = 95%), and a random effects model was applied for analysis. The results of the meta-analysis indicated that TNF-α levels were significantly lower in the IGU group compared to the control group (WMD -6.08 [-8.59, −3.58], p < 0.00001; random effects model) (Figure 17).

FIGURE 17

3.5.5 Adverse events

A total of eight RCTs provided data on adverse events. The heterogeneity test indicated low heterogeneity with p = 0.48 and I2 = 0%, suggesting that a fixed effects model was appropriate for analysis. The meta-analysis indicated that there was no significant difference in adverse events between the IGU and control groups (RR 0.72 [0.47, 1.12], p = 0.15; fixed effect model) (Figure 18). The results of publication bias test showed that it was less likely to have publication bias (p = 0.766).

FIGURE 18

3.5.6 Quality of evidence

According to the GRADE handbook, the evidence was judged to be moderate to very low (Table 4).

TABLE 4

OutcomesIllustrative comparative risks* (95% CI)Relative effect (95% CI)No of participants (studies)Quality of the evidence (GRADE)Comments
Assumed riskCorresponding risk
ControlAdverse event
BASDAIThe mean basdai in the intervention groups was 1.62 standard deviations lower (2.2–1.05 lower)472 (8 studies)⊕⊕⊝⊝ lowa,bSMD -1.62 (−2.2 to −1.05)
BASFIThe mean basfi in the intervention groups was 1.07 lower (1.39–0.75 lower)199 (4 studies)⊕⊕⊕⊝ moderatea
VASThe mean vas in the intervention groups was 2.01 lower (2.85–1.17 lower)291 (5 studies)⊕⊝⊝⊝ very lowa,b,c
Adverse eventsStudy populationRR 0.73 (0.47–1.12)473 (8 studies)⊕⊕⊕⊝ moderatea
179 per 1,000130 per 1,000 (84–200)
Moderate
175 per 1,000128 per 1,000 (82–196)

Evidence quality of IGU for AS.

a

Downgraded one level due to serious risk of bias (random sequence generation, allocation concealment, blinding, incomplete outcomes) and most of the data comes from the RCTs, with moderate risk of bias.

b

Downgraded one level due to the probably substantial heterogeneity.

c

Downgraded one level due to potential publication bias.

3.6 IGU for PSS

3.6.1 ESSPRI

The heterogeneity test showed that some subgroups had high heterogeneity (IGU + other therapy subgroup: p < 0.00001, I2 = 96%; IGU only subgroup: p < 0.0001, I2 = 78%), and a random effect model was used. The meta-analysis results show that compared with the control group, the ESSPRI in the IGU + other therapy group (WMD −1.71 [−2.44, −0.98], p < 0.00001; random effect model) and IGU only group (WMD −2.10 [−2.40, −1.81], p < 0.00001; random effect model) was lower (Figure 19). The results of publication bias test showed that it was less likely to have publication bias in IGU + other therapy subgroup (p = 0.667), while the publication bias test showed that it was likely to have publication bias in IGU only subgroup (p = 0.066).

FIGURE 19

3.6.2 ESSDAI

The heterogeneity test showed that some subgroups had high heterogeneity (IGU + other therapy subgroup: p < 0.00001, I2 = 90%; IGU only subgroup: p = 0.80, I2 = 0%), and a random effect model was used. The meta-analysis results show that compared with the control group, the ESSDAI in the IGU + other therapy group (WMD −1.62 [−2.30, −0.94], p < 0.00001; random effect model) and IGU only group (WMD −1.51 [−1.65, −1.37], p < 0.00001; random effect model) was lower (Figure 20). The results of publication bias test showed that it was less likely to have publication bias in IGU + other therapy (p = 0.691) and IGU only subgroup (p = 0.659).

FIGURE 20

3.6.3 Schirmer’s test

The heterogeneity test showed that some subgroups had high heterogeneity (IGU + other therapy subgroup: p = 0.02, I2 = 63%; IGU only subgroup: p < 0.00001, I2 = 99%), and a random effect model was used. The meta-analysis results show that compared with the control group, the schirmer’s test in the IGU + other therapy group (WMD 2.18 [1.76, 2.59], p < 0.00001; random effect model) and IGU only group (WMD 1.55 [0.35, 2.75], p = 0.01; random effect model) was higher (Figure 21). The results of publication bias test showed that it was less likely to have publication bias in IGU + other therapy (p = 0.612) and IGU only subgroup (p = 0.934).

FIGURE 21

3.6.4 Inflammation factors

Inflammation factors include ESR, CRP and RF.

For ESR, the heterogeneity test showed that some subgroups had high heterogeneity (IGU + other therapy subgroup: p < 0.00001, I2 = 95%; IGU only subgroup: p < 0.00001, I2 = 95%), and a random effect model was used. The meta-analysis results show that compared with the control group, the ESR in the IGU + other therapy group (WMD −8.80 [−11.88, −5.72], p < 0.00001; random effect model) and IGU only group (WMD −4.97 [−7.41, −2.54], p < 0.0001; random effect model) was lower (Figure 22).

FIGURE 22

For CRP, the heterogeneity test showed that some subgroups had high heterogeneity (IGU + other therapy subgroup: p < 0.00001, I2 = 93%; IGU only subgroup: not applicable), and a random effect model was used. The meta-analysis results show that compared with the control group, the CRP in the IGU + other therapy group was lower (SMD −1.16 [−2.31, −0.00], p = 0.05; random effect model) (Figure 23).

FIGURE 23

For RF, the heterogeneity test showed that some subgroups had high heterogeneity (IGU + other therapy subgroup: p < 0.00001, I2 = 88%; IGU only subgroup: p < 0.00001, I2 = 83%), and a random effect model was used. The meta-analysis results show that compared with the control group, the RF in the IGU + other therapy group (WMD −6.44 [−8.05, −4.83], p < 0.00001; random effect model) and IGU only group (WMD −4.42 [−5.94, −2.90], p < 0.0001; random effect model) was lower (Figure 24).

FIGURE 24

3.6.5 Adverse events

The heterogeneity test showed that some subgroups had high heterogeneity (IGU + other therapy subgroup: p = 0.95, I2 = 0%; IGU only subgroup: p = 0.49, I2 = 0%), and a fixed effect model was used. The meta-analysis results show that compared with the control group, the incidence of adverse events in the IGU only group (RR 0.66 [0.48, 0.98], p = 0.01; fixed effect model) was lower, while the difference of the incidence of adverse events between IGU + other therapy group and control grouo was of no statistical significance (RR 0.94 [0.68, 1.29], p = 0.68; fixed effect model) was lower (Figure 25). The results of publication bias test showed that it was less likely to have publication bias in IGU + other therapy (p = 0.777) and IGU only subgroup (p = 0.501).

FIGURE 25

3.6.6 Quality of evidence

According to the GRADE handbook, the evidence of IGU + other therapy subgroup was judged to be moderate to low (Table 5). The evidence of IGU only subgroup was judged to be moderate to very low (Table 6).

TABLE 5

OutcomesIllustrative comparative risks* (95% CI)Relative effect (95% CI)No of participants (studies)Quality of the evidence (GRADE)Comments
Assumed riskCorresponding risk
ControlPrimary outcomes
ESSPRI - IGU + other therapyThe mean ESSPRI in the intervention groups was 1.71 lower (2.44–0.98 lower)500 (7 studies)⊕⊕⊝⊝ lowa,b
ESSDAI - IGU + other therapyThe mean ESSDAI in the intervention groups was 1.62 lower (2.3–0.94 lower)620 (8 studies)⊕⊕⊝⊝ lowa,b
Schirmer’s test - IGU + other therapyThe mean Schirmer’s test in the intervention groups was 2.18 higher (1.76–2.59 higher)466 (6 studies)⊕⊕⊝⊝ lowa,b
Advers events - IGU + other therapyStudy populationRR 0.94 (0.68–1.29)800 (13 studies)⊕⊕⊕⊝ moderatea
160 per 1,000151 per 1,000 (109–207)
Moderate
132 per 1,000124 per 1,000 (90–170)

Evidence quality of IGU for PSS in IGU + other therapy subgroup.

a

Downgraded one level due to serious risk of bias (random sequence generation, allocation concealment, blinding, incomplete outcomes) and most of the data comes from the RCTs, with moderate risk of bias.

b

Downgraded one level due to the probably substantial heterogeneity.

TABLE 6

OutcomesIllustrative comparative risks* (95% CI)Relative effect (95% CI)No of participants (studies)Quality of the evidence (GRADE)Comments
Assumed riskCorresponding risk
ControlAdverse event
ESSPRI - IGU onlyThe mean ESSPRI in the intervention groups was 2.1 lower (2.4–1.81 lower)583 (9 studies)⊕⊝⊝⊝ very lowa,b,c
ESSDAI - IGU onlyThe mean ESSDAI in the intervention groups was 1.51 lower (1.65–1.37 lower)385 (6 studies)⊕⊕⊕⊝ moderatea
Schirmer’s test - IGU onlyThe mean schirmer’s test in the intervention groups was 1.55 higher (0.35–2.75 higher)325 (5 studies)⊕⊕⊝⊝ lowa,b
Adverse events - IGU onlyStudy populationRR 0.66 (0.48–0.92)930 (12 studies)⊕⊕⊕⊝ moderatea
165 per 1,000109 per 1,000 (79–152)
Moderate
200 per 1,000132 per 1,000 (96–184)

Evidence quality of IGU for PSS in IGU only subgroup.

a

Downgraded one level due to serious risk of bias (random sequence generation, allocation concealment, blinding, incomplete outcomes) and most of the data comes from the RCTs, with moderate risk of bias.

b

Downgraded one level due to the probably substantial heterogeneity.

c

Downgraded one level due to potential publication bias.

3.7 IGU for autoimmune disease with interstitial pneumonia

Zhuang et al. (2021) and Zhang et al. (2019) reported the treatment of PSS with interstitial pneumonia. reported the treatment of RA with interstitial pneumonia. Zhang et al. (2019) and reported FVC; they found that IGU may improve FVC.

Meanwhile, Zhuang et al. (2021) showed that both DLCO and 6MWT improved in both groups after treatment, and the degree of improvement in 6MWT in the IGU group was due to that in the control group. Zhang et al. (2019) reported that MMF was also improved after treatment, and the improvement was greater in the IGU group than in the control group. showed that compared with the control group, both FEV1 and TLC were improved after IGU treatment (p < 0.05).

4 Discussion

4.1 IGU for RA

IGU was approved for the treatment of RA in China and Japan in 2012, and in the RA guidelines of the Asia Pacific Association of Rheumatology (APLAR) meeting in 2014. It is recommended as an effective option for intensive treatment of refractory RA (; ). It is now widely used to treat autoimmune diseases and improve related inflammation, such as PSS, IgG4-related diseases, lupus nephritis, etc. (Nozaki, 2021). Studies have shown that compared with other traditional DMARDs drugs, IGU can not only inhibit the production of immunoglobulin and various inflammatory cytokines (IL-1, IL-6, IL-8 and TNF), promote the differentiation of bone cells, inhibit the generation of osteoclasts, reduce bone resorption and joint destruction, but also reduce the expression of matrix metalloproteinases by inhibiting the production of MMP-1 and MMP-3, thereby playing an anti-inflammatory role (; Mizutani et al., 2021; Mu et al., 2021; Tanaka, 2021). In addition, IGU can also inhibit COX-2 and reduce the short-term synergistic effect of pain and inflammation (Mu et al., 2021; Tanaka, 2021).

This meta-analysis found that IGU + MTX therapy can improve ACR20, ACR50, ACR70, DAS28, reduce ESR, CRP, RF, and have a lower incidence of adverse events than the control group. However, IGU alone only significantly improved CRP. IGU + Tripterygium Extract can also improve ESR, CRP and RF. This suggests that IGU + MTX may be a better combination of IGU in the treatment of RA, because it has obvious efficacy, can reduce inflammatory factors, and has a lower incidence of adverse events than the control group therapy (mainly MTX). There is heterogeneity in most outcomes, which is considered to be related to the following points: 1) the dose and duration of IGU and MTX are different; 2) the degree of disease activity of patients at baseline is not the same. Since the extent of disease activity in patients at baseline was not clearly stated in each study, further analysis was not performed. In addition, the dose of IGU in all RCTs was 25–50 mg (25 mg Bid for most RCTs; and 25 Qd or 50 mg Qd for a few RCTs), suggesting that IGU at this dose had a good effect on RA without increasing the incidence of adverse events.

A recent 52-week randomized, double-blind, parallel-controlled, multicenter study by Bao et al. showed that IGU (Use alone) was more effective than MTX in the treatment of RA (). In terms of efficacy, the ACR20 response rate of IGU was 77.44%, which was significantly better than that of MTX (65.87%). In the direction of imaging improvement, the results showed that the proportion of patients with no imaging progression in IGU or combined therapy for 1 year was higher than that in MTX therapy, indicating that IGU therapy was significantly better than MTX therapy. The efficacy of IGU + MTX is similar to that of IGU only, suggesting that patients with early RA can consider IGU alone, and only when the single drug is not effective, combined with other drugs such as biological agents. They also found that IGU or combination therapy can delay the imaging progress of RA patients, which provides an important reference for clinical medication. Another important factor for RA patients and doctors when choosing a drug is the efficacy, safety and cost of the drug. Jie et al. reported data from a real-world pharmacoeconomics study on IGU and other drugs in RA at the 2022 EULAR meeting. Their results show that IGU combined with MTX in the treatment of RA is both safe and effective, and the price is moderate, providing a treatment plan for RA patients that takes into account efficacy, safety and economic cost.

4.2 IGU for AS

The current study shows that IGU, as a new type of DMARD, mainly acts through anti-inflammatory and immune regulation. For example, IGU can inhibit the production of inflammatory cytokines (such as IL-1 and TNF-α), block the IL-17 signaling pathway and inhibit cyclooxygenase, and regulate the balance of osteoclasts (; ), so it may be effective against AS/SpA in mechanism. Therefore, a number of exploratory RCTs have previously applied IGU to AS/SpA (Qiu et al., 2016; Zeng et al., 2016; ; Xu et al., 2019; Pang et al., 2020; Yuan et al., 2020; ; ; ).

The meta-analysis findings revealed that IGU was effective in reducing the BASDAI score, BASFI score, and VAS. Additionally, IGU was able to lower inflammation levels by decreasing ESR, CRP, and TNF-α. However, there was considerable heterogeneity in the results, especially in VAS, ESR, CRP, and TNF-α. This could be attributed to the fact that BASDAI and VAS are subjective measures, and the experiences of patients across different RCTs may differ. Moreover, ESR, CRP, and TNF-α are individual biochemical indicators, and variations in patients’ conditions across different RCTs may also contribute to the heterogeneity. All RCTs reported adverse events, but no patient deaths were recorded. Compared to the control group, the IGU group did not experience any statistically significant difference in adverse events. Therefore, IGU does not appear to increase the risk of adverse events. Notably, the IGU dose was 50 mg in all RCTs (25 mg Bid in most RCTs and 50 mg Qd in a few RCTs), indicating that this dose had a beneficial effect on AS without raising the incidence of adverse events.

4.3 IGU for PSS

The pathogenesis of PSS is complex and has not yet been clearly studied. At present, it is believed that it may be related to various factors such as genetics, environment, endocrine, and immune abnormalities (; ). Among them, the excessive activation of B cells produces a variety of autoantibodies and hyperimmunoglobulinemia plays an important role in the development of pSS. In this process, T cells also participate in the maturation and differentiation of B cells by secreting a variety of cytokines (Rivière et al., 2020). More than 80% of patients with Sjögren’s syndrome will experience symptoms of dryness, fatigue and joint pain, which will affect the patient’s work efficiency and reduce the patient’s quality of life (Marshall and Stevens, 2018). However, there is currently no specific drug for the treatment of pSS. Therefore, exploratory research on PSS therapeutic drugs is currently underway (; Vehof et al., 2020). As a new type of DMARD, IGU’s main mechanism of action is highly compatible with the complex pathogenesis of SS, and has therapeutic potential. A number of clinical studies have shown that IGU can effectively improve the disease activity (such as ESSDAI), various serum indicators (IgG, IgM, IgA, ESR, RF) and lacrimal gland secretion function (detected by Schirmer I test) in patients with pSS.

This meta-analysis also showed that IGU can reduce the ESSPRI score and ESSDAI score, inhibit the inflammation factors (reduce ESR, CRP and RF) and increase Schirmer’s test score. The incidence of adverse events in IGU group was also lower than that in control group, indicating that the addition of IGU may be an effective and safe treatment plan. In addition, the dose of IGU in all RCTs was 50 mg (25 mg Bid for most RCTs and 50 mg Qd for a few RCTs), suggesting that IGU at this dose had a good effect on PSS without increasing the incidence of adverse events. B cell hyperactivity is a key pathogenic factor in pSS, which is mainly characterized by the formation of ectopic germinal centers in the lacrimal and salivary glands (; ; ). Therefore, reducing B cell activity and suppressing immunoglobulin production have become the key to treatment. Studies have shown that IGU not only inhibits the proliferation of T cells, but also inhibits the differentiation of antibody secreting cells (ASCs) in RA patients by activating the PKC/EGR1 pathway, thereby regulating the immune response of B cell differentiation and relieving clinical symptoms (Ye et al., 2019a). However, whether IGU can play a role in the treatment of pSS patients by inhibiting the activity of B cells has not yet been determined.

4.4 IGU for interstitial pneumonia

Early symptoms of RA-interstitial pneumonia (RA-ILD) are often atypical and easy to miss (; ). At present, there is no targeted treatment for RA-ILD, and two clinical strategies are mainly used: anti-inflammatory and anti-fibrosis. In terms of anti-inflammatory, the dosage and treatment time of hormones and immunosuppressants are difficult to grasp. Excessive immunosuppression can also lead to secondary infection aggravating the disease. Therefore, clinical studies are still searching for safe and effective therapeutic drugs for RA-ILD (Wells and Denton, 2014; Santhanam et al., 2020). The current study shows that the potential mechanisms of IGU treatment of pulmonary fibrosis include: inhibition of inflammation and epithelial-mesenchymal transition (EMT) process (). For example, Luo et al. found that inflammatory cell infiltration, inflammatory factor and chemokine expression in the lung tissue of mice treated with IGU treated mice with idiopathic pulmonary fibrosis decreased in a dose-dependent manner. This suggests that IGU can inhibit the pulmonary inflammatory response that accompanies the process of pulmonary fibrosis (Yoo et al., 2020). Zhao et al. found that high doses of IGU and methylprednisolone had inhibitory effects on alveolitis and pulmonary fibrosis in a bleomycin-induced mouse model of pulmonary fibrosis (). Zhu et al. found that IGU can inhibit TGF-β1-mediated human lung fibroblast activation and collagen secretion through the Smad3/p300 pathway, and it may be an effective anti-fibrotic drug to delay the progression of PF ().

In this systematic review and meta-analysis, Zhuang et al. (2021) and Zhang et al. (2019) reported the treatment of PSS with interstitial pneumonia. reported the treatment of RA with interstitial pneumonia. The meta-analysis results showed that FVC increased after IGU treatment. Meanwhile, Zhuang et al. (2021) showed that both DLCO and 6MWT improved in both groups after treatment, and the degree of improvement in 6MWT in the IGU group was due to that in the control group. Zhang et al. (2019) reported that MMF was also improved after treatment, and the improvement was greater in the IGU group than in the control group. showed that compared with the control group, both FEV1 and TLC were improved after IGU treatment. These all suggest the therapeutic effect of IGU on autoimmune diseases complicated with interstitial pneumonia. In terms of economics and drug insurance policy, IGU is a relatively inexpensive drug that is available in most countries. A real-world study retrospectively analyzed the population characteristics, efficacy and influencing factors of RA patients who received IGU treatment for at least 6 months between July 2015 and October 2020 and had more than 3 follow-up records. The results showed that IGU was well tolerated and an effective treatment drug, which is a treatment option for RA patients with interstitial lung disease.

4.5 IGU for other rheumatic and autoimmune diseases

SLE is an autoimmune inflammatory disease that affects multiple organs and connective tissues. It is more common in young women and is seeing an increase in early, mild, and atypical cases (; Shao et al., 2021). Within 5 years, most SLE patients will develop LN, which remains a significant cause of morbidity and mortality (Zhao et al., 2017b). While several drugs have demonstrated efficacy in treating the disease, 20%–35% of LN patients experience relapse or treatment failure, and drug intolerance is a frequent issue (Fu et al., 2021). In preclinical studies with lupus, IGU prevented autoimmune nephritis, reduced proteinuria, and decreased immune complex deposition in MRL/lpr mice (). As the most critical pathogenic cells in the progression and development of systemic lupus erythematosus, B cells are closely related to the systemic damage and antibody secretion of SLE (; ). The earliest study on the mechanism of IGU on B cell differentiation found that it can inhibit the production of immunoglobulin by B cells (Mahajan et al., 2020). In a phase III clinical trial in RA, IGU reduced serum immunoglobulin concentrations (Yan et al., 2014; ). In animal models of RA and lupus, IGU reduced autoantibody titers, including anti-collagen antibodies (Tanaka et al., 2003; Ma et al., 2019) and anti-double-stranded (dsDNA) antibodies [198]. Interestingly, IGU has been reported to reduce peripheral plasma cell counts without affecting the total B cell population in MRL/lpr mice (). Further studies have shown that in RA patients receiving IGU only, IGU regulates key transcription factors affecting plasma cell differentiation through the PKC/Egr1 axis, especially Blimp-1 (). A recent observational study found that more than 90% of patients with refractory LN responded to IGU within 24 weeks without the need to increase steroid dosage or add any other drugs during follow-up (). Yan et al. are currently conducting a multicenter, randomized, 52-week parallel active drug-controlled study (). The study aims to investigate the efficacy of iguratimod as first-line treatment for patients with LN. Patients with biopsy-proven active lupus nephritis from six study sites in China were randomly assigned to the experimental or control group. During the first 24 weeks, IGU was compared to cyclophosphamide as induction therapy, while during the second 24 weeks, IGU was compared to azathioprine as maintenance therapy. The primary outcome was the rate of renal response, including complete and partial response at week 52, which will be analyzed using a noninferiority hypothesis test. This ongoing trial will determine whether iguratimod can be used as an alternative induction or maintenance therapy for lupus nephritis patients ().

In summary, the mechanism of IGU treatment of rheumatic and autoimmune diseases is summarized in Figure 26.

FIGURE 26

4.6 Strengths and limitations

Compared with previous systematic reviews and meta-analyses, the strengths of this study are: 1) Compared with previous studies on PSS (; Pu et al., 2021), this study included newer and more RCTs (32, 5 of which were published in 2022), and the quality of evidence was assessed. 2) Compared with previous studies on RA (Ye et al., 2019b; ; Shrestha et al., 2020; ; Shrestha et al., 2021; Yan et al., 2021; Zeng et al., 2022a; Zeng et al., 2022b; ), this study also included newer and more RCTs (43, 4 of which were published in 2022); and the intervention in the IGU group is IGU alone or IGU combined with other drugs, not limited to IGU + MTX, and further found that the combination of IGU + MTX may reduce the occurrence of adverse events, while IGU combined with other drugs only does not increase adverse events. 3) Compared with previous studies on AS (; ; ; Ouyang et al., 2022; ), this research employed a more rigorous screening process for RCTs. Moreover, this systematic review and meta-analysis integrated findings from various rheumatic and autoimmune diseases. As a result, the efficacy of IGU treatment for AS can be cross-compared with the outcomes of IGU treatment for other rheumatic and autoimmune diseases. 4) This study also evaluated the efficacy and safety of IGU in the treatment of autoimmune disease with interstitial pneumonia for the first time. 5) This study performed a thorough search of different databases and included Chinese databases.

The limitations include: 1) Although there is no language restriction, most of the included RCTs are in Chinese and English, and no literature in other languages has been found, so there may be publication bias. 2) The basic treatment, course of treatment, and observation time of the indicators are also different, and the clinical heterogeneity among the subgroups is high, which leads to a decrease in the accuracy and implementability of the results. 3) Although 84 RCTs were included, only 4 types of diseases (RA, AS, PSS and Autoimmune disease with interstitial pneumonia) were involved, and RCTs of IGU for other rheumatic and autoimmune diseases were not retrieved. 4) Since RCTs did not report on patients’ disease conditions in detail (such as naive RA and MTX-resistant RA), subgroup analysis of patients’ disease conditions could not be performed. 5) The RCTs included in this study are all in English or Chinese, and there are no literature in other languages (such as Japanese) for the time being, which may lead to potential bias. 6) The quality of evidence for most outcomes was assessed as low to very low, which may affect the generalization of conclusions.

Based on these shortcomings, more IGUs are needed in the future for RCTs of other rheumatic and autoimmune diseases (such as SLE). Furthermore, future RCTs are expected to report more detailed patient medication information to facilitate subgroup analysis and reduce clinical heterogeneity.

5 Conclusion

Based on current evidence, IGU may be a safe and effective for the treatment of RA, AS, PSS and autoimmune diseases with interstitial pneumonia. The quality of evidence was very low to moderate. The recommended dose is 25–50 mg. However, more RCTs about other type of rheumatic and autoimmune diseases are still needed.

Statements

Data availability statement

The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding authors.

Author contributions

LZ and KY are responsible for the study concept and design. LZ, QH, YD, YL, JC, YL, AG, KY, XZ, ZL, and LS are responsible for the data collection, data analysis and interpretation; LZ and KY drafted the paper; LS supervised the study. All authors contributed to the article and approved the submitted version.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fphar.2023.1189142/full#supplementary-material

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Summary

Keywords

autoimmune disease, iguratimod, rheumatoid arthritis, ankylosing spondylitis, primary Sjögren’s syndrome, autoimmune disease with interstitial pneumonia, systematic review, meta-analysis

Citation

Zeng L, He Q, Deng Y, Li Y, Chen J, Yang K, Luo Y, Ge A, Zhu X, Long Z and Sun L (2023) Efficacy and safety of iguratimod in the treatment of rheumatic and autoimmune diseases: a meta-analysis and systematic review of 84 randomized controlled trials. Front. Pharmacol. 14:1189142. doi: 10.3389/fphar.2023.1189142

Received

18 March 2023

Accepted

21 August 2023

Published

07 December 2023

Volume

14 - 2023

Edited by

Mohammad Movahedi, University of Toronto, Canada

Reviewed by

Dazhi Fan, Foshan Women and Children Hospital, China

Abir Mokbel, Cairo University, Egypt

Updates

Copyright

*Correspondence: Liuting Zeng, ; Lingyun Sun,

† These authors share first authorship

Disclaimer

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

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