Sirolimus Monotherapy for Thrombocytopenia in Primary Antiphospholipid Syndrome: A Pilot Study From a Tertiary Referral Center.

Background: Thrombocytopenia (TP) is considered as a warning sign of high-risk antiphospholipid syndrome (APS) and sometimes a paradoxical sign of anti-thrombosis treatment. Currently, there is an extreme paucity of effective and safe drugs for long-term management of TP in primary APS patients; therefore, we explored the efficacy and safety of sirolimus monotherapy. Methods: In this real-world study, we included 7 consecutive patients with primary APS who received sirolimus monotherapy for TP. Oral sirolimus was initiated at a dose of 1-2 mg once daily and then adjusted primarily based on clinical efficacy and tolerance, with consideration of the sirolimus trough concentration of ≤15 ng/ml. Results: Of included patients, the median age was 58 years with a median disease course of 1.5 years and 4 patients were treatment-naïve. All patients completed 6 months of sirolimus therapy with a median follow-up of 6 months (range: 6-15). All patients received sirolimus monotherapy for TP during the entire follow-up, without any additional agents. Overall, the platelet count exhibited a substantially increasing trend after sirolimus administration during the first 6 months (p < 0.001) and stability later. Specifically, the median platelet count was significantly increased from 59 × 10 Conclusion: Sirolimus monotherapy confers good efficacy and tolerance for TP in primary APS patients and therefore may be considered as a first-line therapy.