CO094 | ASSESSMENT OF THE MINIMAL EFFECTIVE DOSE OF AVATROMBOPAG IN IMMUNE THROMBOCYTOPENIA: A SINGLE-CENTER REAL-WORLD STUDY

A. Baffioni¹, C. Giubbilei¹, G. Giustini¹, A.M. Vannucchi², V. Carrai³ | ¹SOD Ematologia, Università degli studi di Firenze, Italy; ²Center for Innovation and Research in Myeloproliferative Neoplasms, SOD Ematologia, Azienda Ospedaliera Universitaria Careggi, Università degli studi di Firenze, Italy; ³SOD Ematologia, Dipartimento di Oncologia, Azienda Ospedaliera Universitaria Careggi, Firenze, Italy

Background and Aims. Avatrombopag, a second-generation thrombopoietin receptor agonist (TPO-RA), represents an effective treatment option for chronic immune thrombocytopenia (ITP). In clinical practice, its use is increasingly embedded in a personalized treatment strategy, in which dosing is progressively adjusted to the individual patient in order to optimize platelet count control while minimizing the risk of adverse events and toxicity. In this context, defining the minimal effective dose plays a central role within a tailored approach to ITP management. The aim of this study was to evaluate the minimal maintenance dose of avatrombopag required to sustain a platelet count >50,000/µL while also analyzing clinical characteristics, treatment response, and safety profile.
Methods. We retrospectively analyzed 37 patients treated at our center with avatrombopag (26 females, 11 males), either currently on therapy or previously exposed to the drug. Median age was 47 years (range 19–86). At diagnosis, median platelet count was 10,000/µL, with bleeding manifestations in 56% of patients. Patients had received a median of 3 prior lines of therapy; all had been treated with first-line corticosteroids and 78.38% with intravenous immunoglobulins (IVIG). Twenty-seven patients had received a prior TPO-RA, and among them, 24 underwent a direct switch to avatrombopag. Reasons for switching included lack or loss of response in 62.5% of cases, significant platelet count fluctuations in 8.33%, adverse events in 8.33%, and patient preference for a better tolerability profile. We assessed time to response, number of dose adjustments, minimal effective maintenance dose, and safety outcomes.
Results. During follow-up, a median of 3 dose adjustments was required before reaching a stable effective dose capable of maintaining platelet counts >50,000/µL. In 5 patients (13.5%), temporary treatment interruption due to thrombocytosis during the tapering phase was required, with subsequent reintroduction of therapy. The median stable maintenance dose of avatrombopag was 50 mg/week, associated with a median platelet count of 151,000/µL. At the time of analysis, 25 patients (67.6%) remained on active treatment, while 12 (32.4%) had permanently discontinued therapy. Among these, the median dose at discontinuation was 210 mg/week, with a median platelet count of 21,500/µL. Reasons for discontinuation included loss or lack of response in 6 cases (50%), marked platelet count fluctuations in 4 cases (33.3%), one major adverse event (NSTEMI, 8.3%), and achievement of sustained off-treatment response (SROT, 8.3%). Regarding safety, 14 patients (37.8%) experienced treatment-related adverse events, including thrombocytosis in 5/37 patients (13.5%), thrombotic events (NSTEMI) in 1/37 (2.7%), platelet count fluctuations in 4/37 (10.8%), hepatotoxicity in 3/37 (8.1%), bleeding events in 2/37 (5.4%), and asthenia in 1/37 (2.7%).
Conclusions. In our real-world experience, avatrombopag confirms its effectiveness as a rapid-acting treatment for chronic ITP. The variability in maintenance dose highlights the need for a highly individualized approach, in which the minimal effective dose is often lower than the initial dosing regimen. Dose tapering represents a key step in clinical practice, transforming ITP management into a truly tailored model in which both efficacy and safety are optimized on a patient-specific basis.