This is a Phase I, open-label, dose escalation, multicenter study to evaluate the safety, tolerability, preliminary efficacy, pharmacodynamics (PD), and pharmacokinetics (PK) of EA5 injection in adult participants with Antiphospholipid Syndrome (APS) and recurrent thrombosis who are receiving standard-of-care antithrombotic therapy. Approximately 12 participants will be enrolled. The whole study treatment cycle was 24 weeks. Administration of low-dose EA5: First, administer the loading dose regimen intravenously, then maintain administration subcutaneously every 2 weeks(Q2W). Administration of high-dose EA5: First, administer the loading dose regimen intravenously, then maintain administration subcutaneously every 2 weeks(Q2W).The primary objective is to assess safety and tolerability. Secondary objectives include evaluation of preliminary efficacy, immunogenicity, PK, PD (complement inhibition), and APS-related biomarker changes.