Systemic sclerosis (SSc) is a chronic autoimmune disease with a poor prognosis. Among the various complications of SSc, treatment options for the fibrotic lesions, skin sclerosis, and SSc-associated interstitial lung disease (SSc-ILD) have been limited. However, since 2019, the efficacy and safety of nintedanib, tocilizumab, and rituximab for SSc or SSc-ILD have been demonstrated in double-blind, randomized, placebo-controlled trials, respectively. The antifibrotic agent nintedanib was approved for SSc-ILD in all regions of the United States, Europe, and Japan after the SENSCIS study confirmed that it suppressed the reduction in forced vital capacity (FVC), a measure of SSc-ILD. Tocilizumab, an anti-interleukin-6 receptor antibody, was approved for the treatment of SSc-ILD in the United States after the FocuSSced study showed that it inhibited the decrease in FVC. Rituximab, an anti-CD20 antibody, showed improvement in both modified Rodnan skin score, a measure of skin sclerosis, and FVC in the DESIRES study, and was approved in Japan for the treatment of SSc itself. With the development of these three drugs, SSc treatment is entering a new era. This paper outlines the latest advances in SSc therapeutics, focusing on nintedanib, tocilizumab, and rituximab.

Previous studies have shown the relationship between higher skin thickness score and the existence of organ involvements in systemic sclerosis (SSc). Here, we firstly investigated the correlation between skin thickness score and quantitative measurements of each organ involvement in Japanese patients with SSc. All Japanese SSc patients hospitalized to our clinic for initial evaluation of SSc were selected. Skin thickness was evaluated by modified Rodnan total skin thickness score (mRSS). Relationship between mRSS and prevalence or incidence of organ involvements was examined by logistic analyses. Correlation between mRSS and quantitative measurements of organ involvements was examined by correlation analyses and regression analyses. We recruited 198 patients into our study. The mean disease duration was 7.3 years with the mean follow-up duration of 3.2 years. Multivariate logistic regression analyses revealed that higher mRSS is related to higher prevalence of interstitial lung disease (P < 0.05), restrictive impairment (P < 0.01), and diffusion impairment (P < 0.05) of the lung. Correlation analyses revealed mRSS negatively correlates with forced vital capacity (P < 0.001) and diffusing capacity (P < 0.001) of the lung. Correlation between longitudinal change of mRSS and that of forced vital capacity (P < 0.05) or diffusing capacity (P < 0.001) of the lung was also demonstrated. Skin thickness score significantly correlates with quantitative measurements of lung involvement in Japanese patients with SSc.

Objectives: The double-blind, parallel-group comparison, investigators initiated phase II clinical trial of IDEC-C2B8 (Rituximab) in patients with Systemic sclerosis (DesiReS) trial showed that rituximab is effective in treating skin sclerosis in SSc. However, which patient groups are likely to benefit from rituximab is unknown. Methods: We performed post-hoc analysis of prospective data from 54 patients who received rituximab or placebo in the DesiReS trial. Twenty-seven baseline factors were used to investigate subpopulations with different magnitudes of rituximab effect on modified Rodnan skin score (mRSS) change at 24 weeks. Based on a machine-learning algorithm called the causal tree, we explored the combination of predictors needed to identify subpopulations that would respond to rituximab and have good treatment outcomes. Results: Three factors were identified as branches of the decision tree: peripheral blood CD19-positive cell counts’, ‘mRSS’, and ‘serum surfactant protein D (SP-D) levels’. It was only in the subpopulation of patients with CD19-positive cell counts of <57/μl that rituximab did not show a significant improvement in mRSS vs placebo. In the subpopulation of patients with CD19-positive cell counts of ≥57/μl and mRSS ≥ 17, mRSS was most improved with rituximab [difference −17.06 (95% CI: −24.22, −9.89)]. The second greatest improvement in mRSS with rituximab was in the subpopulation with CD19-positive cell counts of ≥57/μl, mRSS < 17, and serum SP-D levels of ≥151 ng/ml [difference −10.35 (95% CI: −14.77, −5.93)]. Conclusion: SSc patients who have high CD19-positive cell counts and high mRSS are expected to have greater improvement in mRSS with rituximab. When the patients with high CD19-positive cell counts show low mRSS, serum SP-D levels may modify the treatment effect. Trial registration: ClinicalTrials.gov, https://clinicaltrials.gov, NCT04274257 and UMIN-CTR; https://center6.umin.ac.jp, UMIN000030139.