Efficacy and Safety Study of Sirukumab in Patients With Giant Cell Arteritis

Sirukumab is a fully human anti-interleukin-6 (IL-6) immunoglobulin G1-kappa with a high affinity and specificity for binding to the human IL-6 molecule that may have therapeutic benefit in the treatment of giant cell arteritis (GCA) by interruption of multiple pathogenic pathways. Sirukumab inhibits IL-6-mediated signal transducer and activator of transcription 3 (STAT3) phosphorylation, resulting in the inhibition of the biological effect of IL-6. This study will evaluate the efficacy and safety of sirukumab to characterize the benefit-to-risk profile of sirukumab in the treatment of active GCA. The study will be conducted in 2 distinct parts (Part A and Part B) and consists of the following phases: Screening phase, Part A: 52-week double-blind treatment phase, Part B: 104-week extension phase with the option to receive open-label sirukumab based on disease status and a 16-week follow-up phase if applicable.

Approximately 204 subjects with a diagnosis of GCA and active disease within 6 weeks of baseline will be randomized into Part A, the 52-week double-blind treatment phase, to receive one of two doses of sirukumab or placebo, each in addition to a pre-specified prednisone taper. The efficacy and safety of sirukumab in sustaining remission will be assessed at Week 52. Subjects completing Part A of the study will be eligible to enter Part B, the 104-week extension phase, designed to investigate the long-term maintenance of remission and safety following cessation of sirukumab treatment and to assess long-term corticosteroid use. Subjects with active GCA at the end of Part A or those with new onset of GCA flare during the first 52 weeks of Part B will be eligible to receive open-label sirukumab. Subjects will need to have follow-up safety evaluations for at least 16 weeks after receiving the last dose of study drug, applicable only for those who are withdrawn prematurely from the study or whose open-label sirukumab treatment in Part B completes after Week 88.


Eligibility Criteria:
Inclusion Criteria:

* Diagnosis of GCA defined by the following Revised GCA Diagnosis Criteria:

Age \>=50 years. History of ESR \>=50 millimeter/hour (mm/hour) or CRP \>=2.45 milligram/deciliter(mg/dL).

Presence of at least one of the following: Unequivocal cranial symptoms of GCA; Unequivocal symptoms of polymyalgia rheumatic (PMR).

Presence of at least one of the following: Temporal artery biopsy revealing features of GCA; Evidence of large-vessel vasculitis by angiography or cross-sectional imaging.

* Active GCA within 6 weeks of Randomization (Baseline) where active disease is defined by an ESR \>=30 mm/hr or CRP \>=1 mg/dL AND the presence of at least one of the following:

Unequivocal cranial symptoms of GCA; Unequivocal symptoms of PMR; Other features judged by the clinician investigator to be consistent with GCA or PMR flares.

* At screening, receiving or able to receive prednisone 20-60 mg/day for the treatment of active GCA.
* Clinically stable GCA disease at baseline such that the subject is able to safely participate in the blinded prednisone taper regimen in the opinion of the investigator.
* Practicing acceptable methods of birth control if a female of child-bearing potential.
* No evidence of active or latent infection with Mycobacterium tuberculosis (TB).

Exclusion Criteria:

* Are pregnant or breastfeeding.
* Recent (within the past 12 weeks) or planned major surgery that would impact on study procedures or assessments.
* Organ transplantation recipients (except corneas within 3 months prior to baseline visit).
* Had prior treatment with any of the following:

Systemic immunosuppressives) within 4 weeks of baseline; Biologic agents targeted at reducing tumor necrosis factor-alpha (TNF-alpha) within 2-8 weeks of baseline, depending on the agent; Any prior use of tocilizumab or other anti-IL-6 agents; B-cell depleting agents (eg, rituximab) within 12 months prior to baseline or longer if B cell counts have not returned to normal range or baseline levels; Cytotoxic drugs such as cyclophosphamide, chlorambucil, nitrogen mustard, or other alkylating agents within 4 weeks of baseline; Abatacept within 8 weeks of baseline; Tofacitinib within 4 weeks of baseline; Methotrexate use within 2 weeks of baseline.

Methylprednisolone \> 100 mg/day intravenous (IV) (or equivalent) within 8 weeks of baseline.

* History of severe allergic reactions to monoclonal antibodies, human proteins, or excipients.
* Evidence of serious concomitant disease, which in the opinion of the investigator makes them unsuitable for participation in the study.
* Major ischemic event, unrelated to GCA, within 12 weeks of screening.
* Marked baseline prolongation of corrected QT (QTc) interval \>= 450 milliseconds (msec) (QTc by Bazett's formula \[QTcB \]or QTc by Fridericia's formula \[QTcF\] ), history of Torsade de Pointes, family history of long QT syndrome, history of second or third degree heart block.
* Current liver disease that could interfere with the trial
* History of or current active diverticulitis, inflammatory bowel disease, or other symptomatic gastrointestinal tract condition that might predispose to bowel perforation.
* History of known demyelinating diseases such as multiple sclerosis or optic neuritis.
* Active infections, or history of recurrent infections or have required management of acute or chronic infections, as follows:

Currently on any suppressive therapy for a chronic infection, history or suspicion of chronic infection, hospitalization for treatment of infection within 60 days of the baseline visit, or use of parenteral (IV) or intra-muscular \[IM\]) antimicrobials within 60 days of baseline or oral antimicrobials within 30 days of baseline

* Primary or secondary immunodeficiency or any other autoimmune disease.
* Human immunodeficiency virus (HIV) infection, hepatitis C or hepatitis B infection
* Live virus or bacterial vaccination within 3 months before the first administration of study drug