King's College London

Funding Information: Funding The APS ACTION registry was created using REDCAP provided by the Clinical and Translational Science Center at Weill Cornell Medical College (CTSC grant UL1 TR000457). APS ACTION has received partial support from a private donor, APS Foundation of America, APS Support UK, and APS Foundation of Australia. Antiphospholipid antibody kits used at Core laboratories have been donated by INOVA Diagnostics and Instrumentation Laboratory. ML Bertolaccini is supported by the King’s BHF Centre for Award Excellence RE/18/2/34213. Funding Information: The first major clinical trial designed by APS ACTION was the international, multicenter, randomized controlled trial (RCT) assessing the efficacy of hydroxychloroquine (HCQ) for primary thrombosis prevention in persistently aPL-positive but thrombosis-free patients with no other systemic autoimmune diseases. The study, partially supported by New York Community Trust, was terminated earlier than the planned completion date due to the low patient recruitment rate exacerbated by the prolonged manufacturing shortage and price increase of HCQ. Given that a small number of patients with a relatively short follow-up were enrolled in this RCT, and no patients developed thrombosis, we were not able to accurately assess the effectiveness of HCQ for primary thrombosis prevention in persistently aPL-positive patients with no other systemic autoimmune diseases. The details of the study design, results, and challenges have been addressed elsewhere [19]. Publisher Copyright: © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.