This two-part open-label, multi-arm, non-comparative study will collect long-term safety, efficacy and tolerability data from patients who were responsive to canakinumab from study CACZ885G2301E1 (Cohort 1), and from patients who are treatment naïve to canakinumab (Cohort 2). In addition, the effect of inactivated vaccines in an SJIA patient population will be assessed for the development of adequate (protective) antibody levels following immunization according to respective local vaccination guidelines.

Study Part I:

All patients will be treated with canakinumab 4 mg/kg every 4 weeks (or 2 mg/kg every 4 weeks for Cohort 1 patients who are receiving that dose in CACZ885G2301E1) until study end unless discontinuation occurs, or until they qualify for Part II of the study.

Study Part II:

Patients who are eligible will be randomized to receive canakinumab at a reduced dose or prolonged dose interval (see requirements for dose reduction/dose interval prolongation below).

Patients in Cohort 1 receiving 2 mg/kg q4wk in CACZ885G2301E1 will not be randomized but will be part of the treatment arm canakinumab dose reduction if they are eligible.

Key inclusion criteria:

Cohort 1:

1. All patients currently enrolled in study CACZ885G2301E1, including patients who discontinued canakinumab therapy for inactive disease in CACZ885G2301E1 as per physician discretion and who are now currently in a flare and require canakinumab therapy again

Cohort 2:

1. Male and female patients aged ≥ 2 to < 20 years at the time of the screening visit

2. Confirmed diagnosis of SJIA as per ILAR definition that must have occurred at least 2 months prior to enrollment with an onset of disease < 16 years of age:

   • Arthritis in one or more joints, with or preceded by fever of at least 2 weeks duration that is documented to be daily/quotidian for at least 3 days and accompanied by one or more of the following:

   • Evanescent non-fixed erythematous rash,
   • Generalized lymph node enlargement,
   • Hepatomegaly and/ or splenomegaly,
   • Serositis

3. Active systemic disease at the time of baseline visit defined as having 2 or more of the following:

   • Documented spiking, intermittent fever (body temperature > 38°C) for at least 1 day during the screening period and within 1 week before first canakinumab dose,
   • At least 2 joints with active arthritis (using ACR definition of active joint),
   • C-reactive protein (CRP) > 30 mg/L (normal range < 10 mg/L),
   • Rash,
   • Serositis,
   • Lymphadenopathy,
   • Hepatosplenomegaly

4. Patient's willingness to discontinue anakinra, rilonacept, tocilizumab or other experimental drug under close monitoring

5. Patients who are scheduled to receive an immunization, according to their local vaccination guidelines, with an inactivated vaccine and willing to participate in the assessment schedule for vaccinated patients

Key exclusion criteria:

Cohort 1 and Cohort 2:

1. Active or recurrent bacterial, fungal or viral infection at the time of enrollment
2. Underlying metabolic, renal, hepatic, infectious or gastrointestinal conditions which in the opinion of the investigator immunocompromises the patient and/ or places the patient at unacceptable risk for participation in an immunomodulatory therapy.
3. History of malignancy of any organ system (other than localized basal cell carcinoma of the skin), treated or untreated, within the past 5 years, regardless of whether there is evidence of local recurrence or metastases.
4. Live vaccinations within 3 months prior to the start of the study.

Cohort 2:

The following additional key exclusion criteria apply for Cohort 2.

1. Presence of moderate to severe impaired renal function
2. Clinical evidence of liver disease or liver injury as indicated by abnormal liver function tests at screening
3. History/evidence of macrophage activation syndrome within the previous 6 months

Other protocol-defined inclusion/exclusion criteria may apply.