P137 | FOSTAMATINIB IN COMBINATION WITH TPO-RA AS TREATMENT IN PATIENTS WITH MULTIREFRACTORY IMMUNE THROMBOCYTOPENIA

Management of multirefractory immune thrombocytopenia (ITP) represents a very difficult clinical challenge. Data on combinations of fostamatinib (FOS) with thrombopoietin receptor agonists (TPO-RA) are lacking, however, this combination could potentially be effective as these drugs have different mechanisms of action. In this retrospective study, we report the safety and effectiveness of FOS in combination with TPO-RA in a small cohort of 7 patients with multirefractory ITP. All patients received FOS in combination with TPO-RA (6 with romiplostim and 1 with eltrombopag) between September 2022 and March 2025. Median age of patients was 58 years (IQR: 48–76) and 4/7 (57%) were females. All patients had chronic ITP and were refractory with a median of 4 treatment lines prior to combination therapy (IQR: 3–5). All patients were refractory to FOS monotherapy and at least to one TPO-RA monotherapy. After a median follow-up from combination start of 15.5 months (IQR: 1 – 33), all patients achieved at least a response, including 5/7 (71.5%) complete responses. Median time from combination start to response was 7 days (IQR: 7 – 15 days), and median duration of response was 12 months (IQR: 1 – 32 months). Median cumulative number of weeks of platelet count ≥ 30 × 10⁹/L was 49 weeks (IQR: 4 – 98 weeks), and median cumulative number of weeks of platelet count ≥ 50 × 10⁹/L was 38 weeks (IQR: 0 – 98 weeks). No bleeding events were reported. Only 1 patient lost response, however, this patient did not discontinue combination therapy since he was increasing TPO-RA dosage at the last time of data collection. Adverse events were described in 2/7 patients (28.5%): 1 patient with hypertension that was managed by reducing the dose of FOS and 1 patient with elevated unconjugated bilirubin and increased transaminases that were handled by temporary interruption of combination therapy. Of note, the patient who experienced hepatotoxicity was the only one treated with FOS in combination with eltrombopag. Despite the limitations of a retrospective study and the small number of patients, this study reported the efficacy and safety of FOS in combination with TPO-RA in patients with multirefractory ITP. In conclusion, management of multirefractory ITP represents an unmet clinical need, and FOS in combination with TPO-RA could be an attractive treatment option to consider. However, further research is needed, and this approach should be validated by randomized clinical trials.