This trial is conducted in Europe. The aim of this trial is to evaluate the change in disease activity following 12 weekly s.c. (under the skin) doses of NNC109-0012 compared to placebo in subjects with active Rheumatoid Arthritis (RA).

Inclusion Criteria:

• Czech Republic: Age between 18 - 65 years (both inclusive)
• A diagnosis of RA made at least 3 months prior to trial start
• Active RA
• Methotrexate treatment (between 7.5 mg and 25 mg/week, both inclusive) for at least 12 weeks with a stable dose for at least 4 weeks prior to trial start
• Female subjects must be willing to avoid pregnancy and breast feeding throughout this trial at least until 15 weeks following the last dose of trial medication
• Male subjects with partners of childbearing potential must be willing to use a highly effective contraception throughout trial incl. a 15 week follow up periode

Exclusion Criteria:

• Known or suspected allergy to trial product or related products
• Body Mass Index (BMI) lower than 18.5 or higher than 35.0 kg/m^2
• Subjects with chronic inflammatory autoimmune disease other than RA (except secondary Sjögren's syndrome or stable hypothyroidism)