This is a multicenter, randomized, double-blind, parallel, placebo- and active comparator- controlled clinical study conducted in patients with moderately to severely active RA and an inadequate response to at least one DMARD, designed to assess the efficacy and safety of GenSci120 injection in this patient population. The study consists of a screening period (≤ 4 weeks), a placebo-controlled treatment period (14 weeks), an extension treatment period (14 weeks), and a follow-up period (10 weeks), with a total of 17 scheduled visits.

This is a multicenter, randomized, double-blind, parallel, placebo- and active comparator- controlled clinical study conducted in patients with moderately to severely active RA and an inadequate response to at least one DMARD, designed to assess the efficacy and safety of GenSci120 injection in this patient population. The study consists of a screening period (≤ 4 weeks), a placebo-controlled treatment period (14 weeks), an extension treatment period (14 weeks), and a follow-up period (10 weeks), with a total of 17 scheduled visits.

Participants who meet the inclusion criteria will be randomized in a 1:1:1:1:1 ratio to the GenSci120 low dose group-150 mg (Group A), GenSci120 medium dose group-600 mg (Group B), GenSci120 high dose group-1000 mg (Group C), adalimumab group (Group D), and placebo group (Group E), with 90 participants in each group, totaling 450 participants. Among them, the proportion of participants who "have treatment experience of at least one bDMARDs or tsDMARDs" is at least 40%.

Inclusion Criteria:

1. Participants who voluntarily sign an informed consent form before the start of activities related to this study, understand the procedures and methods of this study, and are willing to strictly follow the clinical study protocol to complete this study;
2. Male or female participants aged 18- 70 years (inclusive) when signing the informed consent form;
3. Participants diagnosed with RA according to the 2010 RA classification criteria of the American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR), with ACR functional classification Class I-III at screening;
4. Moderately to severely active RA is defined as TJC ≥ 6 and SJC ≥ 6 at screening and baseline based on 68/66 joint counts, and ESR or C-reactive protein (CRP)/hsCRP exceeding the upper limit of normal at screening. Joints with major surgery history will not be included in TJC and SJC;

Exclusion Criteria:

1. Known allergy to any component in the GenSci120 formulation, or a history of allergic reactions to any drugs, compounds, foods, or other substances, or a history of hypersensitivity.
2. Any autoinflammatory disease or autoimmune disease (excluding secondary Sjogren's syndrome) other than RA, including but not limited to psoriatic arthritis, inflammatory bowel disease, ankylosing spondylitis, systemic lupus erythematosus, systemic sclerosis or idiopathic inflammatory myopathy, multiple sclerosis or other central demyelinating diseases, primary Sjogren's syndrome, immunodeficiency syndrome, etc;
3. Other joint disorders which could interfere with the assessment of joint disease activity according to the investigators' judgement, such as severe osteoarthritis;
4. History of lymphoproliferative disorders, such as lymphoma, or presence of signs or symptoms of lymphoproliferative disorders, including abnormal lymph node enlargement or hepatosplenomegaly;
5. Those with malignant disease or with a history of malignant disease;