The study is a multicenter, randomized, double-blind, placebo-controlled study to evaluate the safety and efficacy of 12 weeks daily treatment with 100 mg AP1189 in RA patients who are to start up-titration with methotrexate (MTX).

Main Inclusion Criteria:

• Confirmed diagnosis of RA according to the 2010 ACR/EULAR RA classification criteria and are ACR class I-III

• ≥ 6 swollen joints (based on 66 joint counts) and ≥ 6 tender joints (based on 68 joint counts).

• Candidate for MTX treatment

• Is about to begin treatment with MTX

• Must meet at least one of the following parameters at Screening:

  1. positive result for anti-CCP or RF
  2. Serum CRP ≥ 6 mg/L

• Highly active RA (CDAI > 22) at screening and baseline

• Negative QuantiFERON-in-Tube test (QFG-IT)

• Females of child-bearing potential must use of highly effective birth control method

Main Exclusion Criteria:

• Major surgery (including joint operation) within 8 weeks prior to screening or planned surgery within 1 month following randomization
• Rheumatic autoimmune disease other than RA, including systemic lupus erythematosus (SLE), mixed connective tissue disease (MCTD), scleroderma, polymyositis, or significant systemic involvement secondary to RA. Sjögren's syndrome with RA is allowable
• Prior history of or current inflammatory joint disease other than RA
• Subjects with fibromyalgia
• Use of hydroxychloroquine within 4 weeks prior the Screening Visit
• Initiation of, or change in existing NSAID treatment within 2 weeks prior to the baseline visit
• Corticosteroids except inhaled or nasal formulations for seasonal allergy or asthma are prohibited within 2 weeks prior to screening
• Evidence of serious uncontrolled concomitant cardiovascular, nervous system, pulmonary, renal, hepatic, endocrine, or gastrointestinal disease
• Have prior renal transplant, current renal dialysis, or severe renal insufficiency
• Uncontrolled disease states, such as asthma, psoriasis, or inflammatory bowel disease where flares are commonly treated with oral or parenteral corticosteroids
• Evidence of active malignant disease (except basal cell carcinoma of the skin that has been excised and cured)
• Neuropathies or other painful conditions that might interfere with pain evaluation
• Body weight of >150 kg
• HBsAg positive and/or Anti-HBc with sign of current infection.