There is no clear therapeutic effect among the enrolled patients for the time being.

This is a single-arm pilot study in Peking Union Medical College Hospital. Telitacicept will be added on traditional antithrombotic and immunosuppressive treatment in primary antiphospholipid syndrome (APS) patients with three positive antiphospholipid antibodies (aPL) and at least one extra-criteria manifestations, including thrombocytopenia, autoimmune hemolytic anemia, aPL associated nephropathy, heart valvular disease, non-stroke neurological manifestations. This study aims to evaluate the efficacy of Telitacicept in preventing thrombosis and improving extra-criteria manifestations on high-risk APS patients.

The study started on July 2021 and will last 1.5 years. Primary APS patients with three positive aPL and extra-criteria manifestations with be enrolled. This is a single-arm pilot study. Telitacicept 160mg once a week for 24 weeks will be added on traditional antithrombotic and immunosuppressive treatment. Patients will be followed on week 12 and week 24. The primary endpoint is new thrombotic event. The secondary endpoints are improvement of extra-criteria manifestations, and titer change of aPL.

Inclusion Criteria:

• meet 2006 Sapporo classification criteria of APS;
• diagnosis of primary APS, exclude other etiologies of thrombosis;
• with three aPL medium-to-high titer positivity, namely lupus anticoagulant, anti cardiolipin antibody, and anti-β2 glycoprotein antibody;
• with at least one extra-criteria manifestations of APS, including thrombocytopenia, hemolytic anemia, aPL nephropathy, valve heart disease and neurological manifestations.

Exclusion Criteria:

• overlap with other connective tissue diseases, such as systemic lupus erythematosus;
• during pregnancy;
• can not follow-up.