1. Must be receiving and tolerating oral or parenteral MTX therapy at a dose of 15 to 25 mg per week (dose may be as low as 10 mg per week if the patient is unable to tolerate a higher dose) for at least 12 weeks immediately prior to Day 1. The dose and administration route should remain stable for at least 4 weeks prior to Day 1 until Week 24. After Week 24 the administration route can be changed at the investigator's discretion. Patients receiving a lower dose of MTX (10 to 14 mg/week) should be doing so as a result of a documented history of intolerance to higher doses of MTX.