Safety and Pharmacokinetics Study of XOMA 052 in Subjects With Active, Stable, Moderate to Severe Rheumatoid Arthritis

Inclusion Criteria:

- American College of Rheumatology (ACR) diagnostic criteria for RA

- Moderate to severe disease, defined as follows - At least six tender and six swollen
joints (28 joint count) AND ESR > 28 mm/hr or CRP > 1.0 mg/dL

- Current duration of RA at Screening ≥ 6 months and ≤ 20 years

- RA and other medical conditions must be stable.

- Age ≥ 18 and ≤ 75 at Screening

- Weight ≥ 80 lbs (36.3 kg) and ≤ 275 lbs (125.0 kg)

- For females with child-bearing potential, a negative serum pregnancy test

Exclusion Criteria:

- Major surgery within 28 days prior to Day 0

- Joint replacement surgery within 60 days prior to Day 0 or joint replacement surgery
planned within 9 months following Day 0

- Known HIV antibody, or hepatitis B surface antigen

- History of malignancy within 5 years prior to Screening other than carcinoma in situ
of the cervix, or adequately treated, non-metastatic squamous or basal cell carcinoma
of the skin

- Immunodeficiency

- History or symptoms of a demyelinating disease

- History of severe allergic or anaphylactic reactions to humanized or murine
monoclonal antibodies. Respiratory distress (dyspnea, oxygen desaturation with pO2 <
90% or onset of acute respiratory distress syndrome), flank or back pain, and/or
hypotension may be signs of anaphylaxis.

- History of tuberculosis, positive PPD test, active atopic disease requiring
medication, or asthma. A subject who has had a positive PPD test but has completed a
course of treatment for tuberculosis, had a documented vaccination against
tuberculosis, or had a negative QuantiFERON -TB test result is eligible.

- Chronic obstructive pulmonary disease (COPD), asthma, or other pulmonary disease
requiring more therapy than using one inhaler 4× daily

- Significant systemic involvement secondary to RA (e.g. vasculitis, pulmonary
fibrosis)

- Liver disease (e.g., hepatitis, cirrhosis) or abnormal hepatic function. If the
diagnosis of liver disease was based on positive Hep C serology due to prior
vaccination, the subject is eligible.

- Pregnant or planning to become pregnant during the course of the study, or
breast-feeding