Part A: Patients will be randomized to 0.3 mg CH-4051, 1.0 mg CH-4051 or MTX. Part B: Patients will not be randomized into Part B until the Data Monitoring Committee has reviewed safety data from the Part A when approximately 25 patients (10 patients in each CH-4051 dose groups and 5 patients in the MTX groups) have completed 3 months of treatment. At this time the DMC will make a recommendation whether or not to commence randomization to 3.0 mg CH-4051, 3.0 mg CH-4051 with 1.0 mg of folic acid.