DOACs versus VKAs to prevent repeat clots in low‑risk antiphospholipid syndrome

Real-world Observational Study to Evaluate the Effectiveness and Safety of Direct Oral Anticoagulants Compared With Vitamin K Antagonists for Secondary Thrombosis Prevention in Low-risk Thrombotic Antiphospholipid Syndrome Patients

This project will see if direct oral anticoagulants (DOACs) work as well and are as safe as vitamin K antagonists (VKAs) to prevent repeat venous clots in adults with low‑risk thrombotic antiphospholipid syndrome.

Quick facts

• Study type: Observational
• Enrollment: 600 (estimated)
• Ages: 18 Years and up
• Sex: All
• Sponsor: Infanta Leonor University Hospital (Academic / other)
• Locations: 2 sites (Madrid, Madrid and 1 other locations)
• Trial ID: NCT07372170 on ClinicalTrials.gov

What this trial studies

This ambispective observational study compares outcomes in adults with prior venous thrombosis and a low‑risk antiphospholipid antibody profile who are treated with either DOACs or VKAs in routine clinical practice. Investigators will collect retrospective and prospective clinical data to compare thrombotic recurrence and bleeding events between the two anticoagulant strategies. Eligible patients must have at least two weeks of continuous anticoagulation and are excluded if they have triple antibody positivity or a history of arterial thrombosis. The study is being conducted at two university hospitals in Madrid and reflects real‑world prescribing and monitoring.

Who should consider this trial

Good fit: Adults with thrombotic APS whose prior event was venous thrombosis and who have single or double antiphospholipid antibody positivity and are on long‑term DOAC or VKA therapy are the ideal candidates.

Not a fit: Patients with triple antiphospholipid antibody positivity, prior arterial thrombosis, anticoagulation for other indications, or those under 18 are unlikely to benefit from conclusions aimed at this low‑risk adult group.

Why it matters

Potential benefit: If results show comparable protection and safety, clinicians could have stronger evidence to offer DOACs as a simpler alternative to VKAs for selected low‑risk APS patients.

How similar studies have performed: Randomized trials raised safety concerns about DOACs in high‑risk APS, while smaller observational series suggest DOACs may be acceptable in carefully selected low‑risk venous APS patients, but overall evidence remains limited.

Eligibility criteria

Inclusion Criteria:

* Adults (≥18 years) with a diagnosis of thrombotic antiphospholipid syndrome.
* Low-risk antiphospholipid syndrome defined by previous venous thrombosis and a single or double positive antiphospholipid antibody profile (lupus anticoagulant, anticardiolipin antibodies, and/or anti-beta-2-glycoprotein I antibodies).
* Patients receiving long-term anticoagulant treatment with direct oral anticoagulants or vitamin K antagonists according to routine clinical practice.
* At least 2 weeks of continuous anticoagulant treatment before study inclusion.

Exclusion Criteria:

* Age \<18 years.
* Triple antiphospholipid antibody positivity.
* History of arterial thrombosis.
* Anticoagulation for indications other than secondary prevention of venous thrombosis related to antiphospholipid syndrome.

Where this trial is running

Madrid, Madrid and 1 other locations

• Hospital Universitario Infanta Leonor — Madrid, Madrid, Spain (Recruiting)
• Hospital Universitario Infanta Sofía — Madrid, Madrid, Spain (Recruiting)

Study contacts

• Principal investigator: Anabel Franco-Moreno, MD, PhD — Sociedad Española De Medicina Interna
• Study coordinator: Anabel Franco Moreno, MD, PhD

Conditions Antiphospholipid Syndrome; Venous Thrombosis; Thrombophilia; Direct oral anticoagulants; Vitamin K antagonists; Low-risk antiphospholipid syndrome; Secondary thrombosis prevention; Real-world study