P131 | EVALUATION OF PLATELET RESPONSE IN CHRONIC ITP PATIENTS TREATED WITH A PERSONALIZED DOSING REGIMEN OF AVATROMBOPAG: A SINGLE-CENTER COHORT ANALYSIS

Introduction: ITP is an autoimmune disorder characterized by isolated thrombocytopenia caused by immune-mediated platelet destruction and insufficient platelet production, resulting in an increased bleeding risk. Thrombopoietin receptor agonists (TPO-RAs) have revolutionized the treatment of ITP. Avatrombopag, a second-generation oral TPO-RA, binds to a distinct site on the thrombopoietin receptor without competing with endogenous thrombopoietin and is distinguished by its rapid action, allowing a timely increase in platelet count Aim:To evaluate the platelet response in a monocentric cohort of patients with chronic ITP treated with Avatrombopag under a personalized dosing regimen Patients and Methods:28 patients (7 males,21 females; median age 57 years) followed at our center were analyzed. They had a median of 3 prior therapy lines; in 68% of cases, a direct switch from another TPO-RA was performed. For each patient, the minimum effective dose of Avatrombopag required to maintain a platelet count ≥30×10³/µL was identified, and response duration was evaluated. Cases of thrombocytosis (>250×10³/µL), their onset, and correlation with dosage were also analyzed Results:The median dose of Avatrombopag was 9.3 mg/day, with median platelet counts of 85×10³/µL. 78.6% of patients achieved and maintained stable platelet counts ≥30×10³/µL (median dose 8.8 mg/day, median platelets 101×10³/µL, median response duration 60 days). At FUP, 57% of patients were still on treatment. The main reasons for discontinuation were: lack or loss of response (n=5), platelet fluctuations (n=3), death unrelated to ITP (n=2), and thrombotic event (n=1, in a patient with cardiovascular risk factors). Thrombocytosis exceeding 250×10³/µL (the treatment suspension threshold according to the product label) occurred in 64% of patients, predominantly in those under 65 years old, with a median onset of 9 days after treatment initiation (median dose 20 mg/day); platelet counts above 440×10³/µL (the upper normal limit of the local laboratory) were observed in 25% of cases Conclusions: Our experience confirms that Avatrombopag enables rapid and significant platelet responses in most patients with chronic ITP. The rapid increase in platelet count suggests potential use in acute settings or in the presence of hemorrhagic syndromes where a timely response is essential. These data support the hypothesis of earlier avatrombopag use in ITP management, pending confirmation from larger prospective studies