Pos1139 the efficacy of tacrolimus in antiphospholipid antibodies associated thrombocytopenia: a prospective cohort study

Background Thrombocytopenia is a common manifestation associated with the presence of antiphospholipid antibodies (aPLs)[1]. A specific guideline for management of aPLs associated thrombocytopenia is still absent. Objectives To investigate the efficacy and safety of tacrolimus treatment in aPLs associated thrombocytopenia and to evaluate potential clinical factors affecting treatment response. Methods This is a single-center observational prospective study. Patients with aPLs associated thrombocytopenia were recruited. Patients with systemic lupus erythematosus (SLE) related major organ involvement were excluded. Treatment response, adverse effects, bleeding events were monitored. Results A total of 61 patients were enrolled from Jan 2016 to Apr 2022 with a median treatment duration of 22 months. The response characteristics are summarized in Table 1. The overall response rate in this cohort was 80.3% (n = 49), including 49.2% of complete responses (n = 30). Compared to commonly used second line therapy for immune thrombocytopenia like eltrombopag and rituximab, the response rate was similar[2,3]. The median time to achieve a response was 3 months (IQR 1, 3). Within the first 3 months, the mean platelet count of patients with overall response elevated continuously (Figure 1). A total of 8 (16.3%) patients with a response experienced a loss of response, 12.2% (n = 6) during treatment, the other in the process of tapering. The median duration of response under treatment was 24.5 months (IQR 9.8, 40.3). 11 (18%) patients had a sustained response after the termination of tacrolimus treatment. Patients diagnosed with SLE had a significantly higher rate of achieving overall response (91.3% vs 73.7%, Figure 2). Side effects were reported in 9.8% (n = 6) of the patients in this cohort and treatment was interrupted due to side effects in 3.3% (n = 2) of patients. Conclusion This study suggests that tacrolimus has adequate efficacy and is well tolerated for aPLs associated thrombocytopenia. Patients with mild to moderate SLE might benefit the most from tacrolimus treatment. References [1]Artim-Esen B, Diz-Küçükkaya R, İnanç M: The significance and management of thrombocytopenia in antiphospholipid syndrome. Curr Rheumatol Rep 2015, 17(3):14. [2]Sandal R, Mishra K, Jandial A, Sahu KK, Siddiqui AD: Update on diagnosis and treatment of immune thrombocytopenia. Expert Rev Clin Pharmacol 2021, 14(5):553-568. [3]Khellaf M, Charles-Nelson A, Fain O, Terriou L, Viallard JF, Cheze S, Graveleau J, Slama B, Audia S, Ebbo M et al : Safety and efficacy of rituximab in adult immune thrombocytopenia: results from a prospective registry including 248 patients. Blood 2014, 124(22):3228-3236. Table 1. Response characteristics of the studied patients. All patients (n = 61) Nonrespond--ers (n = 12) Overall responders (n = 49) Response (n = 19) Complete response (n = 30) p-value Total follow-up, months, mean (SD) 37.6 (19.3) 27.4 (22.1) 40.1 (17.9) 34.7 (18.7) 43.5 (16.9) 0.09 a Duration of treatment, months, median (IQR) 22 (11, 42) 10 (5.8, 13) 27 (14, 44) 27 (14, 40.5) 31 (14.3, 43.8) 0.009 a Time to response, months, median (IQR) / / 3 (1, 3) 3 (1, 4.5) 2 (1, 3) 0.5 b LR during treatment, n (%) / / 6 (12.2) 2 (10.4) 4 (13.3) 1 b LR after cessation of treatment, n (%) / / 2 (4.1) 0 2 (6.7) 0.5 b Duration of response under treatment, months, median (IQR) / / 24.5 (9.8, 40.3) 20 (12, 26.8) 27.5 (9.3, 40.8) 0.4 b Patients achieved TFR, n (%) / / 11 (22.4) 3 (15.8) 8 (26.7) 0.5 b Duration of TFR, months, mean (SD) / / 32.7 (19) 31.3 (16.9) 33.3 (20.8) 0.9 b Concentration of tacrolimus, ng/ml, mean (SD) 5.9 (2.9) 6.6 (3.6) 6.6 (3.6) 6.4 (2.7) 5.0 (2.6) 0.6 a a: nonresponders vs. overall responders. B: response vs. complete response. LR: loss of response. TFR: treatment-free response. Figure 1. Percentages and mean platelet count of patients with different treatment response during follow-up. Figure 2. Cumulative incidence curve of achieving overall response between patients diagnosed with and without SLE. Acknowledgements: NIL. Disclosure of Interests None Declared.