Efficacy and Safety of Ivarmacitinib in the Treatment of Patients With Polymyalgia Rheumatica

Inclusion Criteria: 1. Age and Weight: 50-75 years old, body weight 40-80 kg. 2. Diagnosis: Confirmed diagnosis of polymyalgia rheumatica (PMR) according to the 2012 ACR/EULAR classification criteria . 3. Disease Activity: CRP-PMR-AS (C-reactive protein polymyalgia rheumatica activity score) ≥17 . 4. Glucocorticoid Use: * Newly Diagnosed Patients: No glucocorticoid use within 12 weeks prior to enrollment. * Relapsed Patients: No increase in glucocorticoid dosage within 2 weeks prior to enrollment, and willingness to discontinue current glucocorticoids after enrollment. 5. Compliance: Participants must understand and agree to adhere to study procedures and restrictions. \- Exclusion Criteria: 1. Allergy: Known hypersensitivity to the investigational drug or excipients (including lactose, cellulose-lactose, low-substituted hydroxypropyl cellulose (L-HPC), colloidal silicon dioxide, stearic acid). 2. Comorbidities: * Giant cell arteritis (GCA) . * Other diffuse connective tissue diseases (e.g., systemic lupus erythematosus), spondyloarthropathy, or active fibromyalgia . 3. Uncontrolled Chronic Conditions: * Diabetes (HbA1c ≥8.0%) or uncontrolled hypertension (resting SBP ≥140 mmHg and/or DBP ≥90 mmHg) . * Clinically significant ECG abnormalities (e.g., acute myocardial ischemia, myocardial infarction, severe arrhythmia, QTc \>500 ms). 4. Organ Dysfunction: * Liver/Kidney Impairment: * AST/ALT ≥2× upper limit of normal (ULN). * Serum creatinine or total bilirubin ≥1.5× ULN . 5. Malignancy: History of malignancy within the past 5 years. 6. Infections: * Active uncontrolled infections (e.g., tuberculosis, hepatitis B surface antigen (HBsAg) positive with elevated HBV-DNA, HCV, HIV, or active syphilis). * Severe herpes zoster infection or systemic antimicrobial therapy within 2 weeks prior to randomization. 7. Reproductive Plans: Pregnancy planning within 1 year. 8. Prior Medications: Previous use of JAK inhibitors. 9. Thrombosis: History of thrombotic events. 10. Other: Any condition deemed inappropriate by the investigator for participation in this clinical study.