A Study of Filgotinib in Korean Participants With Rheumatoid Arthritis

1. Participants who voluntarily provided written consent to participate in this study
2. Male or female, aged greater than or equal to (>=) 19 years at the time of written informed consent
3. Participants diagnosed with rheumatoid arthritis according to the 2010 ACR/ European League Against Rheumatism (EULAR) classification criteria and who have an ACR functional class of I to III

4. Participants who meet the following criteria are eligible for the specified treatment protocol; those who have been treated with two or more type types (including MTX) of Disease-Modifying Antirheumatic Drugs (DMARDs) for at least 6 months (at least 3 months each) but have experienced insufficient therapeutic effects or have had to discontinue treatment due to adverse events of these medications (However, in cases where MTX is contraindicated due to conditions such as liver disease or renal failure, the participant must have been treated with at least two types of DMARDs, excluding MTX).

   • Furthermore, in participants over 65 years of age, those at high risk of cardiovascular diseases, and those with a potential risk of malignancy, this protocol applies if they have not adequately responded to or tolerated conventional therapies, including Tumor Necrosis Factor (TNF) inhibitors or other biologic agents. Eligibility is confirmed if one of the following criteria is met:

     1. DAS28 score exceeding 5.1.
     2. DAS28 score between 3.2 and 5.1, with diagnostic imaging showing progression of joint damage.

Exclusion Criteria:

1. Participants with hypersensitivity reactions to the active ingredient or other components of the investigational product
2. Participants with serious infections (for example [e.g.], sepsis) or active infections including localized infections
3. Participants with active tuberculosis (TB)
4. Participants with severe hepatic impairment (e.g., Child-Pugh C)
5. Participants with end-stage renal disease (\<creatinine clearance [CrCl] 15 milliliters per minute [mL/min])
6. Participants with absolute neutrophil count (ANC) \<1*10\^9 cells per liter (/L)
7. Participants with absolute lymphocyte count (ALC) \<0.5*10\^9 cells/L
8. Participants with hemoglobin \<8 grams per deciliter (g/dL)
9. Pregnant or lactating women
10. Women of childbearing potential who are not willing to consent to using effective contraception
11. Participants with rare hereditary problems of galactose intolerance, total lactase deficiency or glucose-galactose malabsorption should not take this medicinal product
12. Participants who received Janus kinase (JAK) inhibitors for the treatment of rheumatoid arthritis
13. Participants who have participated in other clinical studies for investigational product/medical device within 4 weeks prior to screening
14. Participants in whom the administration of Jyseleca Tablet is contraindicated according to the product label approved in Korea or based on certain medical conditions that have been identified in previous clinical studies
15. Participants for whom follow-up deems impossible