Efficacy Endpoint: Percentage of subjects achieving clinical response (reduction in Birmingham Vasculitis Activity Score version 3 [BVASv3] of ≥50% compared to baseline and no worsening in any body system). Subjects who received rescue therapy after Day 1 or discontinued due to related adverse event, lack of efficacy or progressive disease are considered as non-responders at all subsequent visits. The BVASv3 score ranges from 0 to 63 with higher values representing higher disease activity.

Full Analysis Set

Efficacy endpoint: Percentage of subjects with clinical remission, defined as having a BVASv3 = 0. Subjects who received rescue therapy after Day 1 or discontinued due to related adverse event, lack of efficacy or progressive disease are considered as non-responders at all subsequent visits. The BVASv3 score ranges from 0 to 63 with higher values representing higher disease activity.

Full Analysis Set

Efficacy endpoint: Absolute Change from baseline (= screening assessment) in Birmingham Vasculitis Activity Score version 3 (BVASv3) total score; The BVASv3 score ranges from 0 to 63 with higher values representing higher disease activity. The total score is derived by summing up item scores according to the scoring manual for the BVASv3.

Full Analysis Set

Efficacy endpoint: Absolute values of VDI; The VDI total score ranges from 0 to 64 with higher scores indicating more organ damage since the onset of vasculitis. The total score is the number of present damage items.

Full Analysis Set

Efficacy endpoint: Absolute values in PGA; Physician global assessment scale: 0 = Remission to 10 = Maximum activity;

Full Analysis Set

Efficacy endpoint: Absolute values of estimated glomerular filtration rate (eGFR) in mL/min/1.73 m²; The eGFR was calculated by the central laboratory according to the Modified Diet in Renal Disease equation:

eGFR = 175 x (serum creatinine, mg/dL)-1.154 x (age, years)-0.203 x (0.742 if female) x (1.212 if black)

Full Analysis Set

Safety endpoint: Number and percentage of subjects who had a treatment-emergent adverse event (TEAE)

Safety Analysis Set

Safety endpoint: The GTI total score ranges from -35 to 410 (because the bone domain is excluded in this study) with higher score indicating greater Glucocorticoid toxicity. Scoring was performed in the electronic case report form according to the corresponding scoring manual in "Development of a Glucocorticoid Toxicity Index (GTI) using multicriteria decision analysis." by Miloslavsky EM, Naden RP, Bijlsma JW, Brogan PA, Brown ES, Brunetta P, et al.

Safety Analysis Set (Data missing from 2 patients in IFX-1 + Placebo-GC group, from 2 patients in Placebo-IFX-1 + standard dose GC group, and from 3 patients in IFX-1 + reduced dose GC group)

Pharmacokinetics endpoint: IFX-1 plasma concentrations assessed prior to study drug administration at corresponding visit.

Safety Analysis Set (Data missing from 5 patients in IFX-1 + Placebo-GC group, from 7 patients in Placebo-IFX-1 + standard dose GC group, and from 7 patients in IFX-1 + reduced dose GC group)

Pharmacodynamics endpoint: Plasma concentrations of C5a

Full Analysis Set (Data missing from 4 patients in IFX-1 + Placebo-GC group, from 10 patients in Placebo-IFX-1 + standard dose GC group, and from 8 patients in IFX-1 + reduced dose GC group)

Pharmacodynamics endpoint: IFX-1 blocking activity 10 nM

Full Analysis Set (Data missing from 4 patients in IFX-1 + Placebo-GC group, and from 7 patients in IFX-1 + reduced dose GC group, IFX-1 blocking activity was not assessed for patients in Placebo-IFX-1 + standard dose GC group)

Pharmacodynamics endpoint: IFX-1 blocking activity 2.5 nM

Full Analysis Set (Data missing from 4 patients in IFX-1 + Placebo-GC group, and from 7 patients in IFX-1 + reduced dose GC group, IFX-1 blocking activity was not assessed for patients in Placebo-IFX-1 + standard dose GC group)