Study of Apremilast to Treat Subjects With Active Ankylosing Spondylitis

Patients will be assigned two different treatments based on chance (randomized) to placebo or
apremilast (20 or 30 mg tablet). The duration of the study is approximately 5 years. The
double blind period (when patients nor the physician knows whether placebo or apremilast is
taken) is 24 weeks. At Week 16, subjects who do not have either a ≥ 20% improvement or a ≥ 1
unit improvement from baseline in at least two of the four SpondyloArthritis international
Society (ASAS) domains will enter the "early escape" from their current treatment in a
double-blinded manner. However, such subjects will be permitted to continue in the study. At
Week 24, subjects may enter a long-term extension phase for up to an additional 4.5 years
(236 weeks). At "second escape" (at Week 24), apremilast 20 mg BID treated subjects will be
transitioned to receive double-blinded apremilast 30 mg BID; apremilast 30 mg BID will remain
on double-blinded apremilast 30 mg BID because they may continue to improve with a longer
duration of treatment. After Week 24 and during the early portion of the long-term extension
through Week 52, all subjects will continue on either double-blinded apremilast 20 mg BID or
30 mg BID treatment. After all subjects have completed Week 52 or have terminated early from
the study and the 52-week data base is locked, open-label apremilast 20 mg BID or 30 mg BID
treatment will be provided.

Inclusion Criteria:

- Documented diagnosis of Definite Ankylosing Spondylitis [(AS); arthritis of the spine]

- Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) is ≥ 4

- Total back pain is ≥ 4

- On stable dose of AS medication (or lack of medication) prior to randomization and
through week 24

Exclusion Criteria:

- Prior treatment with a Tumor Necrosis Factor (TNF) blocker and any biologic treatment
for AS