Efficacy and Safety of BIIL 284 BS in Adult Patients With Active Rheumatoid Arthritis

Inclusion Criteria: * Patients of \>=18 and \<= 70 years of age * Patients suffering from rheumatoid arthritis as defined by the American Rheumatism Association (ARA) criteria revised 1987 and date of diagnosis \>= 6 months. At least 4 of the following 7 criteria must be present: * Morning stiffness in and around the joints lasting at least 1 hour before maximal improvement for at least 6 weeks * Arthritis (soft tissue thickening or fluid - not bony overgrowth alone) of at least 3 joint areas for at least 6 weeks * Arthritis of hand joints (at least one area swollen in a wrist, metacarpophalangeal (MCP) or proximal interphalangeal (PIP) joint) for at least 6 weeks * Symmetrical arthritis (observed by a physician) with simultaneous involvement of the joints on both sides of the body for at least 6 weeks * Rheumatoid nodules (observed by a physician) over bony prominence or extensor surfaces or in juxta-articular regions * Serum rheumatoid factor positive * X-ray changes typical of rheumatoid arthritis (erosions or unequivocal bony decalcification localized in or most marked adjacent to the involved joints) * Patients belonging to the RA functional class I, II or III * Active RA as defined at visit 2 by: * Swollen joint count at least of 6 (of 28 joints examined) and * Tender joint count at least of 8 (of 28 joints examined) and * Patients must fulfil 2 out of the 3 following criteria: * Patient's assessment of pain (VAS) \>= 40 mm * Investigator's global assessment of disease activity on a VAS \>= 40 mm * ESR \>= 28 mm/h or CRP \>= 20 mg/L * Patient's written informed consent obtained at Visit 1 (screening) before enrolment in the study Exclusion Criteria: * Patient presenting or having a history of inflammatory rheumatic disease other than RA (e.g.: mixed connective tissue disease, systemic lupus erythematosus, seronegative spondyloarthropathy) * Patients who have failed to more than 3 different disease-modifying antirheumatic drug (DMARDs) therapies previously due to lack of efficacy (in case of combined therapy each DMARDs used is counted as one) * Patients with any other disease that could interfere with the evaluation of efficacy and safety * Patients in treatment with any DMARDs / slow-acting anti-rheumatic drug (SAARDs) during the periods specified: * 4 weeks before V2: Methotrexate, parenteral/oral gold, D-penicillamine, Sulphasalazine, antimalarials (e.g.:Chloroquine/Hydroxychloroquine), Azathioprine, Cyclosporine A, Alkylating agents (e.g.: Cyclophosphamide / Chlorambucil), Minocycline, Etanercept (Enbrel®), and Leflunomide (only if wash-out with Colestyramine has been done after leflunomide discontinuation) * 3 months before Visit 2: Leflunomide if no wash- out with colestyramine has been done after leflunomide discontinuation, Infliximab (Remicade®), any other biological compound. * Patient in treatment with oral corticosteroids at a dose higher than 10 mg/day or 0.2 mg/Kg/day (prednisone equivalent) whichever is lower, during the 4 weeks prior to Visit 2, change in the treatment with oral corticosteroids during the 4 weeks prior to Visit 2 or intended change during the trial * Patients in treatment with any parenteral (intravenous, intramuscular or intraarticular) treatment with corticosteroids during the 4 weeks prior to Visit 2 or their intended use during the trial. * Change in treatment with non-steroidal anti-inflammatory drugs (NSAIDs) during the 2 weeks prior to Visit 2 or any intended change during the trial. * Synovectomy, and/or surgical treatment for RA in the previous 3 months prior to visit 2 or intended indication during the trial. * Synoviorthesis in the previous 4 weeks prior to Visit 2 or intended indication during the trial. * Patients in treatment with any other leukotriene inhibitors such as montelukast or zafirlukast 4 weeks prior to Visit 2 or intended use during the trial. * Initiation of physiotherapy during the 2 weeks before V2, or intended change during the trial * Patients with history of cardiovascular, renal, neurologic, psychiatric, liver, gastrointestinal (including lactose intolerance ), immunologic or endocrine dysfunction if they are clinically significant. * Patients with any other known condition or circumstance, which would in the investigator's opinion, prevents compliance or completion of the study * Patients with history of cancer within the past 5 years, excluding treated basal cell carcinoma * Patients with chronic infection or acute infections during the 4 weeks before visit 1 * Patients with known positive serology for hepatitis B or C * Patients with anticoagulant treatment (i.e. dicumarol or derivatives, warfarin) * Any of the following abnormal laboratory parameters at Visit 2: * Impaired hepatic function, defined by serum levels of either Aspartate Aminotransferase (AST)(SGOT), Alanine Aminotransferase (ALT) (SGPT), alkaline phosphatase or bilirubin \> 2 x upper limit of normal (ULN) * Impaired renal function, defined by serum creatinine \> 133 mmol/L (1.5 mg/dl) * Hemoglobin values \< 10 g/dl * White blood cell count \<= 3.500 cells/mm3 * Platelet count of less than 120.000/mm3 * Severe hypoproteinemia (e.g. in case of severe liver disease or nephrotic syndrome) with albumin \< 3.0 g/dl * Patients with any other abnormal, clinically relevant laboratory values not related to RA * Patients participating in another clinical trial during the 3 months prior to visit 2 * Previous participation in the randomised period of this study * Patients with a significant history and/or active alcohol or drug abuse Significant is defined as that which in the opinion of the investigator may either put the patient at risk because of participation in the study or may influence the results of the study or the patient's ability to participate in the study * Pregnancy (to be excluded by pregnancy test at visit 1) or breast feeding, and sexually active women with childbearing potential not using a medically approved method of contraception (i.e. oral contraceptives, intrauterine devices, or double-barrier) for at least one month before and throughout the study period