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2591 Efficacy and Safety of Fostamatinib for Immune Thrombocytopenia in Clinical Practice in Spain: Interim Results of Fostames, Our National Fostamatinib Registry

Program: Oral and Poster Abstracts
Session: 311. Disorders of Platelet Number or Function: Clinical and Epidemiological: Poster II
Hematology Disease Topics & Pathways:
Bleeding and Clotting, autoimmune disorders, platelet disorders, drug development, Diseases, Immune Disorders, Therapies
Sunday, December 10, 2023, 6:00 PM-8:00 PM

Tomas Jose Gonzalez-Lopez, MD1, Gloria Perez Segura2*, Abel Domingo3*, Elsa Lopez Ansoar, MD4*, Francisco Javier Diaz Galvez5*, Reyes Jimenez Barcenas6*, Daniel Martinez Carballeira, MD7*, Dunia De Miguel Llorente8*, Alvaro Perona Blazquez9*, Gerardo Aguilar-Monserrate10*, Julio Dávila-Valls11*, Isabel Gonzalez Gascon12*, Amalia Cuesta13*, María Luisa Bengochea Casado14*, Gerardo Julio Hermida Fernandez15*, Jose Maria Alonso Alonso16*, Miguel Angel Pozas Mañas17*, Ana Torres-Tienza18*, Carlos Aguilar, MD19*, Dolores Fernandez-Jimenez20*, Inmaculada Soto21* and Silvia Bernat22*

1Hospital Universitario de Burgos, Burgos, Spain
2Hospital Universitario 12 de Octubre, Madrid, Spain
3Fundació Privada Hospital Asil de Granollers, Granollers, ESP
4Hospital Universitario Álvaro Cunqueiro, Vigo, Spain
5Hospital Universitario de Burgos, BURGOS, ESP
6Hospital de la Serranía de Ronda , Ronda, Málaga, Spain, Ronda, Spain
7Hospital Universitario Central de Asturias, Oviedo, Asturias, Spain, Oviedo, Spain
8Hospital Universitario de Guadalajara, Guadalajara, Spain, Guadalajara, ESP
9Complejo Hospitalario Universitario de Albacete, Albacete, Spain, Albacete, ESP
10Hospital Clínico Universitario de Valladolid, Valladolid, Spain, Valladolid, Spain
11Hospital Universitario Nuestra Senora de Sonsoles, Avila, ESP
12Hospital Universitario Infanta Leonor, Madrid, Spain, Madrid, ESP
13Hospital Sierrallana, Torrelavega, Cantabria, Spain, Torrelavega, Spain
14Hospital Universitario Severo Ochoa, Madrid, ESP
15Hospital Universitario de Burgos, Burgos, ESP
16Hospital Rio Carrión, Palencia, Palencia, ESP
17Hospital Universitario Río Hortega, Valladolid, Spain, Valladolid, ESP
18Hospital General de Segovia, Segovia, Spain, Segovia, Spain
19Hospital Santa Bárbara, Soria, Spain, Soria, Spain
20Hospital Universitario San Cecilio, Granada, Spain, Granada, Spain
21Hospital Universitario Central de Asturias, Oviedo, Asturias, Spain, Oviedo, ESP
22Hospital Universitario de La Plana, Villareal, Castellón, Spain, Villareal, Spain

Background: Fostamatinib is a splenic tyrosine kinase (SYK) inhibitor that prevents antibody-mediated platelet destruction. This drug has demonstrated to be effective and safe in immune thrombocytopenia (ITP). However, clinical trials may not accurately reflect what happens in clinical practice. Here we evaluated the efficacy and safety of eltrombopag in ITP in a real-world setting.

Aims: To assess the management of adult patients with immune thrombocytopenia (ITP) with fostamatinib (Tavlesse®) in routine clinical practice outside controlled clinical trials.

Methods: Multicentre, retrospective and prospective observational study at national level to evaluate the management of fostamatinib (Tavlesse®) in adult patients with ITP. An interim analysis of the medical records of all patients treated with fostamatinib (Tavlesse®) and suffering from ITP at each center was performed. Data were obtained in a retrospective and prospective observational, non-interventional manner to fulfil the exclusively scientific objective of this study, by conducting a review of the patient's clinical history. Thus, a total of 46 adult patients with ITP from 19 Spanish centers, who had been treated with fostamatinib, were evaluated.

Results: The median age of our cohort was 74 yr (interquartile range, IQR, 60-81 yr). 25/46 (54%) were women. 43 of them were Primary ITP, 2 Secondary ITP and only one Evans Syndrome. 20 (47.6%) had ≥ 1 comorbidity of the Charlson Comorbidity Index. At the time of ITP diagnosis, the median platelet count was 8 x 109/L (IQR, 4-21 x 109/L) while 31 (69%) patients had hemorrhages.

The median time with a diagnosis of ITP at initiation of fostamatinib was 61 months (IQR, 9-160 months). The median number of therapies prior to fostamatinib was 4 (IQR, 3-6). Of the entire cohort of 46 patients, 35 had been exposed to eltrombopag, 33 to romiplostim, 23 to intravenous immunoglobulins (IVIG), and 21 to rituximab. Only eight and two patients had received avatrombopag and splenectomy prior to fostamatinib treatment, respectively.

26/46 patients (56.5%) were treated with fostamatinib monotherapy throughout ITP. Twenty-three patients (50%) had signs/symptoms of bleeding in the month prior to treatment initiation. The median platelet count at baseline on fostamatinib was 12 × 109/L (IQR, 6-28 × 109/L), while the median platelet count to best response achieved after fostamatinib treatment was 84 × 109/L (IQR, 28-187 × 109/L). The median time from initiation of fostamatinib to maximum response to treatment was 2 months (IQR, 0-3.25). Similarly, the median duration of treatment with fostamatinib was 2 months (IQR, 1-4.25). The median time from initiation of fostamatinib to dose increase to 150 mg twice a day was 16 days (IQR, 8-38).

A total of 32/46 patients (69.5%) responded to fostamatinib. Thus, 21 patients (45.7%) achieved a complete response (platelet count > 100 x 109/L) and 11 achieved a response. Twenty-one patients (45.6%) experienced adverse events, mainly grade 1-2, with diarrhea (n=13) and hypertension (n=8) being the most frequent. Twenty-five patients (54.3%) discontinued fostamatinib treatment: 18 did so due to inefficacy with three exitus due to severe bleeding in the context of refractory ITP. On the contrary, only three patients discontinued the drug due to toxicity/severe adverse events.

Summary/Conclusion: Fostamatinib was used in heavily treated patients. However, fostamatinib proved to be effective and well tolerated in unselected patients with primary and secondary ITP. The association of fostamatinib with other drugs or its use in earlier lines of therapy may be associated with higher platelet response rates.

Disclosures: Gonzalez-Lopez: Amgen: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Sobi: Honoraria, Research Funding; Grifols: Honoraria, Research Funding; Momenta: Honoraria; Alpine: Honoraria; Argenx: Honoraria.

*signifies non-member of ASH