Inclusion Criteria:

• Male or female aged ≥ 18 years.
• A diagnosis of rheumatoid arthritis according to the American College of Rheumatology (ACR1987 classification) of at least six months duration from diagnosis at screening.
• Positive screening for Rheumatoid Factor and/or anti-CCP.
• Subjects must be treated with MTX, 7.5-25 mg/week, for at least 12 weeks prior to Visit 2, with the last 4 weeks prior to Day 2 at a stable dosage.
• Patient must be willing to receive folic acid.
• Body mass index (BMI) < 35kg/m2 (inclusive).
• A female subject is eligible to participate if she is of child-bearing potential and agrees to use one of the contraception methods listed in Section 8.1 for an appropriate period of time (as determined by the product label or investigator) prior to the start of dosing to sufficiently minimize the risk of pregnancy at that point. Female subjects must agree to use contraception until one year after the last dose of Ofatumumab.
• Male subjects must agree to use one of the contraception methods listed in Section 8.1. This criterion must be followed from the time of the first dose of study medication until one year after the last dose of Ofatumumab.
• QTcB or QTcF < 450 msec.
• Chest x-ray is negative for any finding associated with an acute or chronic lung infection at screening.
• A chest X-ray with postero-anterior projections and, if indicated, lateral projections, taken within 12 weeks prior to Visit 1, may be used. Only if clinically warranted should the x-ray be repeated at screening.
• Capable of giving written informed consent, which includes compliance with the requirements and restrictions listed in the consent form.
• Following receipt of verbal and written information about the study, the subject must provide signed informed consent before any study related activity including wash-out of other drug products is carried out.
• France: In France, a subject will be eligible for inclusion in this study only if either affiliated to or a beneficiary of a social security category.

5.2.2. Additional Inclusion Criteria for subjects in Part B

• Active disease at the time of screening and baseline with a DAS28 score ≥3.2 (based on ESR) despite stable dose of methotrexate (MTX), 7.5-25mg/week.

Exclusion Criteria:

• Subjects with a history of a rheumatic autoimmune disease other than RA (except secondary Sjögren's syndrome), significant systemic involvement secondary to RA (vasculitis, pulmonary fibrosis or Felty's syndrome).
• Previous exposure to biologic cell depleting anti-rheumatic therapies, including investigational compounds (e.g. anti-CD11a, anti-CD19, anti-CD20, anti-CD22, anti-BLyS/BAFF, anti-CD3, anti-CD4, anti-CD5, anti-CD52.
• Exposure to etanercept < 4 weeks, infliximab or adalimumab < 8 weeks, or abatacept or anakinra < 12 weeks prior to visit 2.

• Received any of the following treatments within 4 weeks prior to Visit 2:

  • Anti-cancer therapy (e.g. alkylating agents, anti-metabolites, purine analogues, monoclonal antibodies)
  • Glucocorticoid unless given in doses equivalent to ≤ 10 mg of prednisolone /day
  • Intra-articular, i.m. or IV corticosteroids
  • Live/attenuated vaccinations
  • Cyclosporine
  • Azathioprine
  • Penicillamine
• Exposure to sulfasalazine within 6 weeks prior to Visit 2.
• Exposure to Hydroxychloroquine or leflunomide within 12 weeks prior to Visit 2 unless the subject who has received leflunomide has also completed peroral cholestyramine treatment for washout according to locally accepted clinical practices.
• Exposure to gold therapy ≤ 12 weeks prior to Visit 2.
• Exposure to IV immunogammaglobulins ≤ 24 weeks prior to Visit 2
• Past or current malignant melanoma.

• Past or current malignancy, except for:

  • Cervical carcinoma Stage 1B or less
  • Non-invasive basal cell skin carcinoma
  • Other cancer with a complete response duration of > 5 years

• Chronic or ongoing active infectious disease requiring systemic treatment such as, but not limited to, renal infection, chest infection with bronchiectasis, tuberculosis and active hepatitis B and C.

  • Screening for TB will be done in accordance with local guidelines including Mantoux testing, and if necessary follow-up with QuantiFERON testing for patients whose history of immunization with BCG cannot be documented.
  • Patients with a negative test OR a positive Mantoux test and a negative QFT-G test are eligible for inclusion into the study.
  • Patients with a positive Mantoux test without QFT-G negativity are excluded. Additionally, patients with documented BCG vaccination will be exempted from the Mantoux test assessment.
• Please refer to Study Procedures Manual for more detail.
• Clinically significant cardiac disease including unstable angina, acute myocardial infarction within six months from screening, congestive heart failure, known QT abnormalities, and arrhythmia requiring therapy, with the exception of extra systoles or minor conduction abnormalities.
• Significant concurrent, uncontrolled medical condition including, but not limited to, renal, hepatic, hematological, gastrointestinal, endocrine, pulmonary, neurological, cerebral psychiatric disease, or evidence of demyelinating disease.
• History of significant cerebrovascular disease.
• Known HIV positive.

• Screening laboratory values (according to central laboratory):

  • Hemoglobin < 5.6 mmol/L (9.0 g/dL)
  • CD19+ B-cell count < 0.1 x 109/L
  • Neutrophils < 2 x 109/ L
  • Platelets < 100 x 109/ L
  • Serum IgG < lower limit of normal
  • S-ALAT > 3 times the upper limit of normal
  • S-AST > 3 times the upper limit of normal
  • S-ALP > 2 times the upper limit of normal
  • S-creatinine > 133 µmol/L (1.5 mg/dL)

• Positive serology for hepatitis B (HB) defined as:

  o Positive test for HBsAg.

• If negative, Hep B serology negativity will be confirmed by:

  • Negative serology to anti-HBc. Patients who are positive for Hepatitis B core antibody are excluded.
  • Negative serology to HB surface antibody.
• Hepatitis B surface antibody positivity without core antibody positivity indicates vaccination against Hepatitis B and is not exclusionary.
• Positive test for anti-hepatitis C antibody.
• Positive plasma / white cell JC Virus (JCV) PCR (either compartment)
• Known hypersensitivity to components of the investigational medicinal product or MTX.
• Where participation in the study would result in donation of blood or blood products in excess of 500 mL within a 56 day period.
• Subjects who have received treatment with any non-marketed drug substance or experimental therapy within 4 weeks or 5 half-lives (whichever is longer) prior to screening.
• Current participation in any other interventional clinical study.
• Subjects known or suspected of not being able to comply with a study protocol (e.g. due to alcoholism, drug dependency or psychological disorder).
• The subject has a positive pre-study drug screen with positive results for amphetamines, cocaine or cannabinoids.
• Breast feeding women or women with a positive pregnancy test at screening.
• Unwillingness or inability to follow the procedures outlined in the protocol.