| Clinical remission | Having a BVAS/WG = 0, regardless of immunosuppressive therapy. |
| Complete response | Having a BVAS/WG = 0 on low dose prednisone and on maintenance AZA/AZA placebo. |
| Remission | Having a BVAS/WG = 0. |
| Complete remission | Having a BVAS/WG = 0 and being off glucocorticoid therapy. |
| Partial remission | Having a BVAS/WG ≤ 2 and being off glucocorticoid therapy during the trial. |
| Sustained remission | Complete remission for at least 6 months. |
| Clinical tolerance | Complete remission without immunosuppressive therapy, a normalized B-cell count, an absence of ANCA, and an adaptive immune system that responds normally to neoantigens. |
| Control arm | The study treatment group receiving rituximab-placebo, CYC, AZA, and prednisone. |
| Crossover | A change in treatment group to the opposite study therapy regimen between visit V5 (1 week after the last rituximab/rituximab-placebo infusion) and visit V8 (month-6 study visit). |
| Switchover | Participants who do not deviate from original study therapy and all crossover participants that achieve clinical remissions (BVAS/WG = 0) deemed stable by the investigator will switch from CYC/CYC-placebo to AZA/AZA-placebo between months 3–6 after the first dose of the rituximab/rituximab-placebo infusion. |
| Disease response | A reduction of at least 1 in the BVAS/WG as compared to the screening measure, no new disease manifestation, and no new worsening of existing disease. |
| Early treatment failure | Failure to achieve disease response by the month 1 study visit, i.e., 1 week after the fourth infusion, or to complete the full course of rituximab/rituximab-placebo infusions due to treatment-related adverse effects. |
| Experimental arm | The study treatment group receiving rituximab, prednisone, CYC-placebo, and AZA-placebo. |
| Investigational agent | Rituximab (375 mg/m2) |
| Investigational regimen | Rituximab (375 mg/m2) once a week x4, plus glucocorticoids |
| Limited flare | Having a new occurrence or worsening of one or more minor BVAS/WG items. |
| Post-study phase | The study period that starts after the last scheduled study visit in the remission maintenance phase (the 18-month study visit after V1 or V1A) and lasts until the common closing date. The post study phase for open-label rituximab patients starts 6 months after V1B. |
| Severe flare | Having a BVAS/WG >3 or experiencing one of the major BVAS/WG items listed in Table 2 that requires treatment with CYC following remission (BVAS/WG = 0). |
| Pretreatment phase | The study period that lasts approximately 2 weeks and that includes screening, signing of the informed consent form, receipt of intravenous steroids, and randomization. |
| Remission induction phase (phase I) | The 6-month study period following randomization. |
| Remission maintenance phase (phase II) | The 12-month study period following the remission induction phase. |
| Remission induction treatment | Rituximab infusion (once weekly for 4 weeks) or rituximab placebo infusion (once weekly for 4 weeks), cyclophosphamide or cyclophosphamide placebo (orally for 3–6 months), and prednisone (orally for up to 6 months). |
| Remission maintenance treatment | AZA or AZA placebo (orally for 12–15 months), depending on the timing of switchover from CYC/CYC placebo to AZA/AZA placebo). |
| Severe AAV | Having a diagnosis of AAV (GPA or MPA) that meets the Chapel Hill Consensus Conference definitions, a positive PR3-ANCA or MPO-ANCA test, and disease activity/severity that requires treatment with CYC. |
| Study medications | Rituximab or placebo, CYC or placebo, AZA or placebo. |
| Study therapy | CYC/CYC placebo, AZA/AZA placebo, or rituximab/rituximab placebo. |
| Study termination | Discontinuing the rituximab/rituximab placebo, CYC/CYC placebo, or AZA/AZA placebo study therapies as per protocol. |
| Treatment failure | Situations that may lead to treatment modification as defined in the protocol. |