The following changes were made throughout the protocol: - Inclusion criteria were broadened to include subjects meeting the ASAS clinical criteria and not limited only to subjects meeting the new ASAS imaging criteria. Subjects meeting the new imaging criteria represented at least 50% of subjects not meeting the mNY classification criteria. - Clarification was included that x-rays and MRIs documenting sacroiliitis for subjects meeting the new ASAS imaging criteria must be read by a radiologist (MRIs) and records (x-rays and MRIs) must be included in source documentation. - Update was made to permit samples collected for measurement of CZP plasma concentration to be possibly used for exploratory biomarker (Dickkopf-related protein 1 [DKK1] and sclerostin) research. - Update was made to Exclusion Criteria 6 and 7 to more clearly define exclusion of subjects with fibromyalgia. - The secondary objective assessment of subject symptomatic state was added, which included the secondary (Patient Acceptable Symptomatic State [PASS] and Physician Acceptable Symptomatic State) and exploratory (Patient’s Global Impression of Change [PGIC]) variables. - Update was made to collect SI joint x-ray at Baseline for all subjects not receiving a Baseline MRI. - The schematic of the injection schedule was corrected to remove placebo injection from Week 48 in the CZP 200mg group. - Information on the possible use of other MRI reading criteria in addition to the Spondyloarthritis Research Consortium of Canada (SPARCC) criteria (such as Berlin or modified Berlin criteria) was included. - Clarification was added that the 44 joint counts include both swollen and tender joint counts. - Clarification was added that recording of axSpA history includes relevant family history and prior and concomitant medication history.

The following changes were made throughout the protocol: - The Full Analysis Set (FAS) was replaced by the RS for primary efficacy analyses. - The SAP was adjusted for multiple endpoints including implementation of the following: Addition of Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) (Weeks 12 and 24) and Bath Ankylosing Spondylitis Metrology Index (BASMI) (Weeks 12 and 24) to the key secondary variables. A hierarchical test procedure was applied to protect the overall significance level of the multiplicity of dose groups and endpoints with a predefined order of hypotheses testing for the following endpoints: ASAS20 response at Weeks 12 and 24 (200mg Q2W and 400mg Q4W), Bath Ankylosing Spondylitis Functional Index (BASFI) Weeks 12 and 24 (combined dose groups), BASDAI Weeks 12 and 24 (combined dose groups), and BASMI Weeks 12 and 24 (combined dose groups). - A marker for inflammation (C-reactive protein [CRP] >upper limit of normal [ULN]) was added to Inclusion Criterion #6. One retesting of subjects failing Screening due to CRP level was permitted. - Clarification was added that SI joint x-rays were performed at Baseline for all subjects. - Update was added that a SI joint x-ray performed <12 weeks (instead of <4 weeks) prior to the Baseline Visit may be used as the Baseline assessment provided that the film can be submitted and meets the requirements for central reading. - Clarification was added that subjects who were enrolled on the basis of meeting the imaging criteria must have been diagnosed on this basis prior to the Screening Visit. - Clarification was added that abatacept was both a prohibited medication (if used within 3 months prior to Baseline) and a prohibited concomitant and rescue treatment. - For TB testing, inconsistencies in visit referencing (eg, Baseline) with regards to purified protein derivative (PPD) tests were corrected to reference the Screening Visit. (Continued below)