OC 26.4 - Questioning the benefit of Caplacizumab for the treatment of acquired Thrombotic Thrombocytopenic Purpura: a real-world, single center experience

Background: Acquired thrombotic thrombocytopenic purpura (aTTP) is a rare, autoimmune disorder with a high mortality if untreated. Standard of care (SOC) treatment includes plasma exchange (PLEX), and immunosuppressants. Addition of caplacizumab to SOC has been associated with improved time-to-normalization of platelets and clinical outcomes. In January 2020, caplacizumab was added to SOC for aTTP at our institution.

Aims: Compare outcomes before and after addition of caplacizumab to SOC for treatment of aTTP.

Methods: This is a single-center, retrospective study. Data were abstracted from electronic health record for treatment of first aTTP episode between August 2016 and March 2023. Baseline characteristics, aTTP treatment, and clinical outcomes over 12 months were recorded. Primary outcome: time-to-normalization of platelets. Secondary outcomes: composite endpoint of thromboembolic events, one-year mortality, and aTTP exacerbation. Other secondary endpoints: mortality, thromboembolic events, bleeding events, lengths of stay, number of PLEX sessions, rates of remission, exacerbation, and time-to-relapse.

Results: Fifty seven patients were included in the analysis, 43 (75%) received SOC without caplacizumab and 14 (28.2%) received SOC + caplacizumab. Most patients were African Americans (AA; 75%), female (72%), median age 48 (16-83). All patients received immunosuppresants (corticosteroids ± rituximab). There was no difference in time to platelet normalization (median 3.66 vs. 3.42 days, p=0.49). Mortality at 1 year was not significantly different (6 in SOC vs 1 in SOC+caplacizumab, p=0.67). Exacerbation rates were reduced in patients treated with caplacizumab. No difference was observed for all other outcomes.

Conclusion(s): This retrospective, real-world, single center analysis revealed a decrease in exacerbation rates as the only benefit to the addition of caplacizumab to SOC. All other outcomes were comparable between the two groups. Of note, the majority of the subjects in this cohort were AA, further underscoring exisiting questions on race-related differences in response to therapy in aTTP.