A Study to Evaluate the Pharmacokinetics, Pharmacodynamics, and Safety of Tocilizumab (TCZ) Administered to Participants With Giant Cell Arteritis (GCA).

Inclusion Criteria: * Diagnosis of GCA as classified according to protocol-specified criteria; * Participants entering Period 1 must be receiving treatment with TCZ 8 mg/kg IV Q4W. Exclusion Criteria: * Treatment with any other investigational agent besides TCZ within 12 weeks (or 5 half-lives of the investigational drug, whichever is longer) prior to screening; * Evidence of serious uncontrolled disease; * Known active current or history of recurrent bacterial, viral, fungal, mycobacterial, or other infections; * Active TB requiring treatment within the previous 3 years.