Abatacept for Treating Adults With Giant Cell Arteritis and Takayasu's Arteritis

GCA and TAK both cause inflammation in the lining of the arteries, which can interfere with
the body's ability to carry oxygen to areas that need it. Symptoms of GCA include headaches,
jaw pain, and blurred or double vision. Serious symptoms that occur less commonly are
blindness and stroke. TAK symptoms include fever, fatigue, weight loss, arthritis, and
non-specific aches and pains. There may also be tenderness near affected arteries.
Researchers believe that GCA and TAK are diseases that are controlled by the body's immune
system. Activated T-cells, specifically, are critical to the origin and development of these
diseases. Abatacept is a medication that modulates the signal required for T-cell activation.
This study will evaluate the safety and effectiveness of abatacept in treating GCA and TAK
and preventing disease relapse.

Participation in this study may last up to 4 years. Participants will receive abatacept
intravenously on specified days during Months 1, 2, and 3. They will also receive daily
prednisone, which will be started at a dose of 40 to 60mg, then tapered to 20mg by Month 3,
and finally further tapered until discontinuation is reached. At Month 3, participants who
have achieved remission will be randomly assigned under double-blind conditions to either
continue abatacept or be switched to placebo infusions. Both treatments will be given once a
month at study visits. Blood samples will also be collected at the monthly study visits to
conduct laboratory-based studies. Participants who remain in remission will continue to
receive abatacept or placebo monthly until the common closing date, defined as 12 months
after enrollment of the 33rd participant for each disease.

Inclusion Criteria:

- Diagnosis of GCA or TAK (defined below)

- History of active GCA or TAK within the past 2 months

- Age of 15 years or older

- Willing to use an effective means of birth control throughout the study

Specific Inclusion Criteria for Participants with GCA:

- Participants must meet three of the following five criteria, including either
Criterion 4 or 5:

1. Age at disease onset was equal to or greater than 50 years

2. Disease onset was recent or experiencing a new type of localized pain in the head

3. Erythrocyte sedimentation rate greater than 40mm in the first hour, as determined
using the Westergren method

4. Temporal artery abnormality (i.e., temporal artery tenderness to palpation or
decreased pulsation, unrelated to arteriosclerosis of cervical arteries)

5. Temporal artery or large vessel biopsy showing vasculitis characterized by a
predominance of mononuclear cell infiltration or granulomatous inflammation,
usually with multinucleated giant cell or characteristic changes of large vessel
stenosis or aneurysm by arteriography

Specific Inclusion Criteria for Participants with TAK:

- Presence of abnormalities that are consistent with TAK identified using arteriography,
plus at least one of the following criteria:

1. Age at disease onset was less than 50 years

2. Pain in the legs or arms

3. Decreased brachial artery pulse (one or both arteries)

4. Difference of more than 10mm Hg in blood pressure between the arms

5. Bruit over subclavian arteries or aorta

Exclusion Criteria:

- Evidence of active infection (including chronic infection)

- Pregnant or breastfeeding

- HIV infected, hepatitis C infected, or a positive hepatitis B surface antigen

- Inability to comply with study guidelines

- Inability to provide informed consent

- Cytopenia, as defined by a platelet count of less than 80,000/mm3, an absolute
neutrophil count of less than 1,500/mm3, and hematocrit less than 20%

- Insufficient kidney function, as defined by a serum creatinine of more than 3 mg/dL or
creatinine clearance of 20 ml/min or less

- Other uncontrolled disease that could prevent safe study completion

- History of any malignant neoplasm except adequately treated basal or squamous cell
carcinoma of the skin or solid tumors treated with curative therapy and disease-free
for at least 5 years

- Receipt of an investigational agent or device within 30 days prior to study entry

- A live vaccination within 4 weeks prior to study entry

- Presence of a positive tuberculin skin test with induration of at least 5mm

- Radiographic evidence suggestive of tuberculosis

- Poor tolerability of blood draws or lack of adequate access to veins for medication
administration and blood draws

- History of treatment with rituximab within 12 months prior to study entry or history
of treatment with rituximab more than 12 months prior to study entry, where the B
lymphocyte count has not returned to normal

- History of treatment with infliximab within the past 49 days, adalimumab within the
past 28 days, or etanercept within the past 21 days.

- Presence of any of the following diseases or conditions:

1. Microscopic polyangiitis

2. Churg-Strauss syndrome

3. Polyarteritis nodosa

4. Cogan's syndrome

5. Behcet disease

6. Sarcoidosis

7. Kawasaki disease

8. Tuberculosis or atypical mycobacterial infection

9. Deep fungal infection

10. Lymphoma, lymphomatoid granulomatosis, or other type of malignancy that mimics
vasculitis

11. Cryoglobulinemic vasculitis

12. Systemic lupus erythematosus

13. Rheumatoid arthritis

14. Mixed connective tissue disease or any overlap autoimmune syndrome