A Study of the EP4 Antagonist CR6086 in Combination With Methotrexate, in DMARD-naïve Patients With Early Rheumatoid Arthritis

Inclusion Criteria: 1. Male or female aged ≥18 years. 2. Patients with diagnosis of definite Rheumatoid Arthritis (RA) according to the 2010 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) classification criteria. 3. Disease duration no longer than 1 year (early RA). 4. Patients must be naïve to any DMARDs (csDMARDs, or bDMARDs, or tsDMARDs) other than hydroxychloroquine. 5. Patients with "moderate" disease activity as documented by a Disease Activity Score 28 (DAS28) (C-Reactive Protein - CRP) index score \> 3.2. 6. Patients with serum C-Reactive Protein (hsCRP) higher than the upper limit of normal. 7. Patients positive for serum rheumatoid factor (RF) or anti-cyclic citrullinated peptide antibodies (ACPA). Exclusion Criteria: 1. Rheumatic autoimmune disease other than RA, or current inflammatory joint disease other than RA, or non-inflammatory type of musculoskeletal condition (e.g., osteoarthritis or fibromyalgia) that in the Investigator's opinion is symptomatic and/or severe enough to interfere with the study procedures. 2. History of gastric/duodenal ulcers and gastrointestinal bleeding, or gastrointestinal diseases known to interfere with the absorption or excretion of medications. 3. Severe, progressive, or uncontrolled renal, hepatic, hematologic, gastrointestinal, metabolic, endocrine, pulmonary, cardiac or neurologic disease. 4. Malignancy (with the exception of adequately treated or excised non-metastatic basal cell or squamous cell cancer of the skin or cervical carcinoma in situ) active during the 12 months preceding the Screening Visit. 5. Acute hepatitis (during the 3 months preceding the Screening Visit), chronic hepatitis, or HIV infection. 6. History of alcohol or drug abuse, or 7. allergy/sensitivity to lactose. 8. Vaccination with live vaccines during the 6 weeks preceding the Screening Visit. 9. Clinically significant abnormalities in haematology, serum alkaline-phosphatase, gamma-glutamyl-transferase, alanine aminotransferase, aspartate aminotransferase, total bilirubin, creatinine clearance, 12-lead ECG. 10. Use of hydroxychloroquine during the 4 weeks preceding the Screening Visit. 11. Treatment with oral corticosteroids, unless maintained at doses equivalent to ≤10 mg/day prednisone ≥7 days before the Screening Visit. 12. Use of nonsteroidal anti-inflammatory drugs (NSAIDs). 13. Use of other investigational drugs/treatments, or enrolment in a clinical trial during the 6 months preceding the Screening Visit. 14. For women of childbearing potential: 1. Pregnancy (i.e. positive pregnancy test at Screening) or breastfeeding 2. Failure to agree to practice a highly effective method of contraception. 15. For sexually active men with a female partner of childbearing potential: failure to agree to use contraception.