Janus kinase inhibition (JAKi) therapy in refractory anti-synthetase syndrome: A retrospective cohort study

To evaluate the efficacy and safety of Janus kinase inhibitors (JAKi) in the treatment of refractory anti-synthetase syndrome (ASS) in real-world clinical settings. The medical records of all refractory ASS patients who were treated with JAKi from October 2020 to June 2023 were retrospectively reviewed. Twenty patients were included, and all (100%) patients had interstitial lung disease (ILD). After treatment with JAKi, 14 (70%) of the refractory ASS patients showed significant improvement in clinical manifestations, including arthritis (56.3% vs. 6.3%, p = 0.002), rash (77.8% vs. 27.8%, p = 0.012), shortness of breath (55.6% vs. 16.7%, p = 0.039), cough (61.1% vs. 11.1%, p = 0.012). Improvement was noted for myalgia (50% vs. 11.1%, p = 0.016) and muscular weakness (61.1% vs. 11.1%, p = 0.012), while creatine kinase (CK) levels, which were abnormally elevated in five patients prior treatment, were significantly lowered (1096 ± 1042.98 IU/L vs. 199.2 ± 144.66 IU/L, p = 0.043). A decrease in levels of inflammatory markers, including erythrocyte sedimentation rate (ESR) (p = 0.001) and C-reactive protein (CRP) (p = 0.023) was observed in the patients. In ASS-ILD, the CT score reduced (188.75 ± 69.67 vs. 156.35 ± 74.62, p = 0.001). Furthermore, the glucocorticoid dose significantly reduced (21.42 ± 13.26 mg vs. 11.32 ± 8.59 mg; p = 0.001). JAKi were effective in most refractory ASS patients as evidenced by improved skin rash, myositis, and ILD. However, larger prospective controlled studies are required to evaluate its efficacy.