Impact of first-line use of caplacizumab on treatment outcomes in immune thrombotic thrombocytopenic purpura

Abstract

Background: The von Willebrand factor-directed nanobody caplacizumab has greatly changed the treatment of immune thrombotic thrombocytopenic purpura (iTTP) in recent years. Data from randomized controlled trials established efficacy and safety.

Objectives: This study aims to address open questions regarding patient selection, tailoring of therapy duration, obstacles in prescribing caplacizumab in iTTP, effect on adjunct treatment, and outcomes in the real-world setting.

Methods: We report retrospective, observational cohorts of 113 iTTP episodes treated with caplacizumab and 119 historical control episodes treated without caplacizumab. We aggregated data from the caplacizumab phase II/III trials and real-world data from France, the United Kingdom, Germany, and Austria (846 episodes, 396 treated with caplacizumab, and 450 historical controls).

Results: Caplacizumab was efficacious in iTTP, independent of the timing of therapy initiation, but curtailed the time of active iTTP only when used in the first-line therapy within 72 hours after diagnosis and until at least partial ADAMTS13-activity remission. Aggregated data from multiple study populations showed that caplacizumab use resulted in significant absolute risk reduction of 2.87% for iTTP-related mortality (number needed to treat 35) and a relative risk reduction of 59%.

Conclusion: Caplacizumab should be used in first line and until ADAMTS13-remission, lowers iTTP-related mortality and refractoriness, and decreases the number of daily plasma exchange and hospital stay. This trial is registered at www.

Clinicaltrials: gov as #NCT04985318.

Keywords: ADAMTS13 protein; observational study; purpura; thrombotic microangiopathies; thrombotic thrombocytopenic; von Willebrand factor.