This study is a prospective, open-labelled, randomized, controlled, single-center clinical trial. The aim of this study is to compare the remission rate of patients treated with Telitacicept combined with azathioprine and azathioprine alone in remission-maintenance treatment of AAV.

Background: The basic theme of AAV is relapse and remission. The maintenance therapy of AAV aimed to reduce or prevent relapse is very challenge. Although many medications have been used for the maintenance of AAV, Telitacicept (a BAFF/APRIL dual-target-inhibitor, which has been proved to be effect in treatment of SLE) has not been studied yet. One study tested the efficacy of Belimumab in the maintenance therapy for AAV. When taken Rituximab as remission-induction treatment, no relapse was observed. However, the sample size of this study is small, and the Belimumab, as a BAFF inhibitor, was not been proved to have effect on APRIL.

Many experiences have been accumulated about the efficacy and safety of Telitacicept in Chinese patients with rheumatic diseases. But there is no study to show its effectiveness in the reduction of the relapse of AAV in China. In this study, we add Telitacicept to azathioprine in maintain treatment in AAV patients who receive Rituximab as remission-induction treatment, to compare the relapse rates of Telitacicept combining azathioprine and azathioprine alone in maintenance therapy of AAV.

Objectives: To compare the relapse rates of Telitacicept combining azathioprine and azathioprine alone in maintenance treatment of AAV.

Study Design: This is a prospective, randomized, open-label, control, pilot study.

Inclusion Criteria:

1. Patients age 18 to 65 years, both genders can be included.
2. Patients who are newly diagnosed or relapsing granulomatosis with polyangiitis or microscopic polyangiitis must fulfill the 2022 ACR/EULAR classification criteria of GPA or MPA.
3. Patients who are in complete remission after combined treatment with glucocorticoids and Rituximab. Remission is defined as a Birmingham Vasculitis Activity Score (BVAS version 3) of 0. And the daily dosage of prednisone are no more than 10mg (or equivalent).
4. Patients have to be ANCA-positive at diagnosis or during the course of their disease.

Exclusion Criteria:

1. Patients with TPMT gene mutation.
2. Patients who had been treated with either AZA but relapsed in the past.
3. Patients who had been treated with either AZA but had to stop due to adverse events or intolerance.
4. Patients who have planned for pregnancy in next 1.5 years.
5. Patients with severe liver dysfunction(defined as the 2-folds elevation of normal upper limit or Child grade III), heart failure or ESRD(eGFR<30ml/min).
6. Patients with uncontrolled sever hypertension, diabetes, active bacteria or fungal infection;
7. Patients with active hepatitis virus infection as well as patients who have active mycobacteria infection;
8. Patients who had other autoimmune diseases.
9. Patients with malignancy.
10. Patients who are not eligible according to the judge of the principal investigators or site investigators.