Effects and Safety of the Tripterygium Glycoside Adjuvant Methotrexate Therapy in Rheumatoid Arthritis: A Systematic Review and Meta-Analysis

Objective This study aimed to systematically review the efficacy and clinical safety of different courses and doses of tripterygium glycoside (TG) adjuvant methotrexate (MTX) therapy in the treatment of rheumatoid arthritis (RA). Methods Randomized controlled trials (RCTs) of TG adjuvant MTX therapy in patients with RA were retrieved from SinoMed, China Network Knowledge Infrastructure, WanFang Data, PubMed, Cochrane Library, and Embase from inception to September 30, 2021. The effects and clinical safety evaluations were conducted using RevMan 5.3 software. Results A total of 9 RCTs and 892 patients with RA were included in this study. In the meta-analysis, a total of 463 and 429 patients were enrolled into the TG adjuvant MTX therapy group and MTX monotherapy group, respectively. In comparison with MTX monotherapy, the results of the analyzed effects showed that the TG adjuvant MTX therapy can achieve 20%, 50%, and 70% improvements in American College of Rheumatology (ACR) criteria ACR20, ACR50, and ACR70 at P = 0.005, P = 0.0001, and P = 0.004, respectively. Simultaneously, the efficacy of the TG adjuvant MTX therapy was improved at either 30 or 60 mg/day over a six-month course compared to MTX monotherapy (P < 0.0001). There was no statistical difference in the effects between the doses of 30 and 60 mg/day after three months (P = 0.82). TG adjuvant MTX also reduced the expression rate of the swollen joint count, tender joint count, erythrocyte sedimentation rate, rheumatoid factor, and C-reactive protein in subgroup analyses with different courses and doses. In terms of hepatic adverse effects (P = 0.28), leukopenia (P = 0.78), gastrointestinal adverse effects (P = 0.17), cutaneous adverse effects (P = 0.94), and irregular menstruation adverse effects (P = 0.29), there was no statistically significant difference with TG adjuvant MTX therapy and MTX monotherapy with different courses and doses. Conclusions TG adjuvant MTX therapy is more effective than MTX monotherapy and is a safe strategy for RA treatment in doses of 30 or 60 mg/day over a treatment course of six months. However, high-quality multicenter RCT studies with large sample sizes are still needed to confirm the effects and clinical safety of different courses and doses of TG adjuvant MTX therapy.


Introduction
Rheumatoid arthritis (RA) is a complex, inflammatory, and systemic autoimmune disease. It is associated with progressive disability, and it primarily affects the lining of the synovial joints [1,2]. Patients with RA typically present with symmetrical polyarthritis of the small joints of the hands and feet with early morning stiffness and occasional constitutional symptoms [3]. Methotrexate (MTX) is the first-line treatment given to patients with RA. MTX can reduce the level of inflammation and prevent joint erosion and functional damage.
e clinical effect of using MTX monotherapy is only 60% to 70%, whereas adjuvant therapy has positive significance in improving clinical effects [4]. erefore, the clinical treatment of RA often uses MTX and adjuvant drugs, such as sinomenine and iguratimod, to enhance effects [5,6].
Traditional Chinese herbal medicine has achieved considerable progress in treating RA [7,8]. Tripterygium glycosides (TGs), which are the extracts of Tripterygium wilfordii Hook F, have been widely used as anti-inflammatory drugs and immunosuppressants for treating RA. e effective parts of TGs mainly include diterpenoids, alkaloids, triterpenoids, and glycosides. Most of these active constituents of TGs are effective in anti-inflammation and immunosuppression [9]. In the United States, several clinical trials have shown that TG has good effects in patients with RA because of its anti-inflammatory and immunosuppressive activities [10][11][12].
During RA treatment, adjuvant therapeutics, which involve several drugs that interact with multiple targets in the molecular networks of RA, may achieve better effects compared with monotherapy [13,14]. TG has been empirically applied in adjuvant therapy with MTX for RA treatment [15,16]. Previous studies have shown that TG adjuvant MTX therapy is a more effective strategy than MTX monotherapy for RA treatment and adverse reactions were not aggravated [17][18][19]. However, the effects and safety of different courses and doses of TG adjuvant MTX therapy in RA need to be further explored.

Methods
is study was investigated according to the preferred reporting items for systematic review and meta-analysis (PRISMA) 2020 checklist (Supplementary Information 1).

Protocol Registration.
is meta-analysis study and its protocol were registered in PROSPERO of the Centre for Reviews and Dissemination (NO. CRD42021224095).

Study Selection and Data Extractions.
e titles and abstracts of the searched results were independently assessed by two investigators (Q. Geng and B. Liu). e full texts of the potentially eligible studies were then screened for final inclusion in the current study. Disagreements were resolved by a third opinion (C. Lu). e extracted data included the study characteristics (authors, title, etc.), patient characteristics (number of patients, age, gender, etc.), intervention, control, and outcomes.

Risk of Bias in Individual Studies.
e two investigators (Q. Geng and B. Liu) used the Cochrane Collaboration [22] "Risk of Bias" tool to assess the methodological quality of the each included studies. Seven items including random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective reporting, and other biases were assessed as low risk, high risk, or unclear risk. Each potential source of bias was graded as high, low, or unclear.
2.6. Statistical Analysis. Statistical analyses were performed using RevMan 5.3 software from the Cochrane Collaboration. e data were summarized using risk ratio (RR) at 95% confidence intervals (CIs) for dichotomous data. For continuous variables, the mean difference (MD) was used if the outcome measurement units of each study were the same, however, standardized MD (SMD) was used if the measurement units and methods were different among the studies. Statistical heterogeneity was tested by examining both the chi-square test and the I 2 statistic. e I 2 values ranged from 0 to 100% and were categorized as follows: I 2 <40%, might not be important; 50% < I 2 < 90%, moderate heterogeneity; 75% < I 2 < 100%, considerable heterogeneity [23]. A fixed-effect model was used to pool the estimates using the fixed effects model when I 2 ≤ 50%,P ≥ 0.1. I 2 > 50% and P < 0.1 indicated the possibility of statistical heterogeneity, and random-effects model was adopted. Potential sources of heterogeneity were explored using subgroup and sensitivity analyses. We conducted a subgroup analysis of different courses and doses (three-month course of 30 mg/ day, three-month course of 60 mg/day, six-month course of 30 mg/day, and six-month course of 60 mg/day). e results are presented as forest plots. Sensitivity analyses were also performed to test the stability of the results via the leave-oneout method. Funnel plots and Egger's test were used to assess for publication bias when there are at least 10 studies included in the meta-analysis [22].

Evidence Quality Evaluation.
e results of the metaanalysis were evaluated using the GRADE method [24], and degradation was considered in terms of the risk of bias, inconsistency, indirectness, imprecision, and publication bias. e evidence quality was classified as "high quality," "moderate quality," "low quality," and "very low quality."

Risk of Bias of the Included RCTs.
Four studies [19,25,29,30] had a low risk of bias for random sequence generation because their random number generation method uses a random number table or centralized randomization. e other studies were at unclear risk of random sequence generation because the method was not mentioned in any of these studies. All studies were rated as having an unclear risk for allocation concealment because it was unclear whether the allocation concealment researchers were third-party personnel. With regard to attrition bias, three studies [19,25,26] reported the results according to preset outcomes. us, these studies were rated as having low risk. e remaining studies failed to clarify whether the outcomes were established in advance. us, these studies were rated as having an unclear risk. Two studies [19,31] were considered at low risk of detection bias, and the remaining studies did not provide blinding information and were Evidence-Based Complementary and Alternative Medicine 3 considered at unclear risk. Due to the specificity of the intervention, all included studies were considered to be at high risk for performance bias. For reporting bias, the current study had to check the Methods and Results sections of all trials on the bias of the information in the Methods section because of the unavailability of protocols in the included trials. After a rigorous assessment, there was a low risk of selective reporting and other biases in all studies (Figures 2 and 3).  6(b)).

Safety of Interventions.
e forest plot (Supplementary Figure 4)    Evidence-Based Complementary and Alternative Medicine       Evidence-Based Complementary and Alternative Medicine 3.7. Evidence Quality Evaluation. We used the GRADE Pro system to evaluate the quality of evidence for the primary outcomes of different courses and doses. e RCT was preset to the highest level of evidence in the GRADE evidence quality assessment and was processed according to five degradation factors. e results suggested that the quality of the evidence was low ( Supplementary Information 4). e main reason for this result is that the study design is not rigorous, and the sample size is not sufficient.

Discussion
is study focused on 9 RCTs with 892 RA participants to evaluate the effects and clinical safety of different courses and doses of TG adjuvant MTX therapy in the treatment of RA in comparison with MTX monotherapy. e test results show that there were no significant differences in the baseline of patients and interventions in all evaluated studies. Most system baselines also showed no significant differences, thus conforming to the principle of metaanalysis. e results of this study showed that TG adjuvant MTX therapy is more effective than MTX monotherapy and is a safe strategy for RA treatment with different courses and doses. For effects, a six-month course of TG adjuvant MTX for RA increased the primary outcomes of ACR20, ACR50, and ACR70, which are the gold standard composite measures used in clinical trials of patients with RA [32]. For secondary outcomes, TG adjuvant MTX also reduced the expressions of SJC, TJC, ESR, CRP, and RF. SJC and TJC are indices for evaluating disease activity, severity, and curative effect in patients with RA [33]. ESR and CRP are often used in the clinical diagnosis of RA [34]. RF is a nonspecific detection indicator of RA with high sensitivity [35]. In terms of safety, TG adjuvant MTX therapy did not increase the incidence of adverse effects for three or six months compared with MTX monotherapy. erefore, these clinical data suggest that a six-month course of treatment at 30 or 60 mg/ day of TG adjuvant MTX therapy may be a more effective and safer strategy for RA treatment.
Currently, although the etiology and pathological mechanism of RA are not clear, a large number of studies have shown that the abnormality and interaction of cytokines play important roles in the pathogenesis of RA [36,37]. Interleukin-6 (IL-6) is a type of proinflammatory cytokine that can promote the proliferation of B cells in RA disease, increase the biological effect of tumor necrosis factor-alpha (TNF-α), and promote the development of RA [38]. TNF-α is involved in the pathogenesis of RA by activating endothelial cells and promoting the synthesis and release of inflammatory cytokines [39]. Several studies have shown that both MTX monotherapy and TG adjuvant MTX therapy can reduce the expressions of IL-6 and TNF-α, however, the expressions of IL-6 and TNF-α decrease more significantly in the adjuvant therapy. It suggests that TG adjuvant MTX treatment can enhance the synergistic effect of the two drugs by inhibiting the activities of IL-6 and TNF-α and control the progression of RA [40]. is finding may explain the improvement in secondary outcomes at the three-month course even though no significant improvements were observed in ACR20, ACR50, and ACR70. It does not conflict with the absence of improvements in ACR20, ACR50, and ACR70, which is one of the secondary outcomes evaluated for ACR20, ACR50, and ACR70. Significant improvements in ACR20, ACR50, and ACR70 can only be evaluated if three additional indicators improve by more than 20%, 50%, and 70% on top of the improvement in SJC and TJC. e heterogeneity of secondary outcomes was high. Although we performed subgroup analysis, we were unable to reduce the heterogeneity probably because of the fact that most secondary outcomes were laboratory measures with different reference ranges in different hospitals or probably because there was an uneven distribution among the subgroups in terms of the number of studies and cases.
is meta-analysis has some limitations. Firstly, random allocation principle, allocation concealment, and blinding were not described in detail in some of the included documents. Secondly, given that the sample of raw data in this study was small and because all involved trials were conducted in China, the results of this review might have introduced potential selection bias. It may have caused measurement bias in the implementation and outcome evaluation.
irdly, the high heterogeneity of individual literature may be because of the low quality of the included literature, the difference in sample size, the difference in disease activity of patients, and the difference in the course of treatment. Although these limitations may undermine the level of evidence of this meta-analysis, the selected trials are highly comparable, and the documents were selected in strict accordance with the inclusion criteria.

Conclusion
According to the nine RCTs included, a six-month course of TG adjuvant MTX therapy at 30 or 60 mg/day is more effective than MTX monotherapy and is a safe strategy for treating RA. However, because of the low quality of GRADE evaluations and given the limitations of existing research, further high-quality multicenter RCT studies with large sample sizes are needed to confirm the clinical safety of TG combination therapy.

Data Availability
e data used to support the findings of this study are available from the corresponding author upon request. extracted and analyzed the data. Guilin Ouyang and Zhixing Nie assessed the risk of bias. All authors read and approved the manuscript for submission.