• Adding caplacizumab to standard of care for the treatment of iTTP does not reduce all-cause mortality but increases bleeding risk.

  • Frontline caplacizumab may not benefit all patients with thrombotic thrombocytopenic purpura.

Introduction Immune thrombotic thrombocytopenic purpura (iTTP) is an acquired, fatal microangiopathy if untreated. Randomized controlled trials (RCT's) demonstrated faster time-to-response with adding caplacizumab to standard of care (SOC). However, concerns about RCT selection bias and the high cost of caplacizumab warrant examination of all evidence, including real-world observational studies. Methods In this systematic review and meta-analysis, we searched the literature for comparative studies evaluating SOC with or without caplacizumab for the treatment of iTTP. We assessed risk-of-bias using the Cochrane RoB-2 tool (RCT's) and Newcastle-Ottawa Scale (observational studies). The primary efficacy outcome was all-cause mortality, and the primary safety outcome was treatment-emergent bleeding. Secondary outcomes included exacerbation and relapse, refractory iTTP, and time-to-response. Results We included two high-quality RCT's and three observational studies at high-risk-of-bias comprising 632 participants. Compared with SOC, caplacizumab was associated with a non-significant reduction in the RR (0.21 [CI 0.05-1.74]) of death in RCT's and observational studies (RR 0.62 [CI 0.07, 4.41]). Compared with SOC, caplacizumab was associated with an increased risk of bleeding in RCT's (RR 1.37 [CI 1.06, 1.77]). In observational studies, the risk of bleeding was not significantly increased (RR 7.10 [CI 0.90, 56.14]). Addition of caplacizumab was also associated with a significant reduction in refractory iTTP and exacerbation, increased risk of relapse, and shortened response time. Conclusion Frontline addition of caplacizumab does not significantly reduce all-cause mortality compared with SOC alone, although it reduces refractory disease risk, shortens time-to-response, and improves exacerbation rates, at the expense of increased relapse and bleeding risk.

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