Evaluation of Safety and Efficacy of T1h (anti-CD6) as Monotherapy and in Combination with Methotrexate in Patientes with Rheumatoid Arthritis

INTERVENTION: Antibodies, Monoclonal, Humanized Stage I: Four level doses of T1h (0.1, 0.2, 0.4 y 0.8 mg/Kg respectively) by Intravenous route [IV] (infusion in 200 mL of sterile 0.9% sodium chloride solution over 2 hours) once weekly for 12 weeks. Stage II: Group control: Placebo Group study: T1h at optimal dose determined in Stage I Both groups will receive the product (placebo or T1h) by intravenous route (detailed above), once weekly for 12 weeks. All patients will also receive concomitant MTX (7.5 to 25 mg/Kg orally), once weekly for 12 weeks. T1h (anti‐CD6) CONDITION: Arthritis, Rheumatoid Rheumatoid Arthritis PRIMARY OUTCOME: Stage I: Safety, tolerability and optimal biological dose. Measuring time: 4th week after last T1h dose. Stage II: ACR50. Measuring time: 12nd week after last T1h dose. SECONDARY OUTCOME: Pharmacokinetics, ACR20, ACR50, ACR 70. Measuring time: during 24 weeks of study INCLUSION CRITERIA: 1. Patients who expressed in writing in its informed consent form available from participating in the clinical trial. 2. Age between 18 and 65, inclusive, of any gender or skin color. 3. Patient who has not previously been treated with monoclonal antibodies. 4. Patients with at least 1 year with active RA diagnosed according to ACR criteria (American College of Rheumatology) revised in 1987. 5. Patients without concomitant anti‐rheumatic during the four weeks before the administration of MAb. 6. Patients with hemoglobin = 8.5 g / L, WBC> 3x109 cells / mL, platelet count> 100x109/mL and transaminase (TGP) within the normal reference values (UI). 7. Patients with 8 or more joints swollen at the time of starting treatment. 8. Patients with 8 or more joints painful at the time of starting treatment.