Successful Discontinuation of Eltrombopag after Complete Remission in Patients with Primary Immune Thrombocytopenia
Authors: González-López Tomás José , Pascual Cristina , Álvarez-Román María Teresa , Fernández-Fuertes Fernando , Sánchez-González Blanca , Caparrós Isabel , Jarque Isidro , Mingot María Eva , Hernández-Rivas José Ángel , Martín-Salces Mónica , Solán Laura , Beneit Paola , Jiménez Reyes , Bernat Silvia , Andrade Marcio M , Cortés Montserrat , Cortti Maria José , Pérez-Crespo Susana , Gómez-Núñez Marta , Olivera Pavel E. , Pérez-Rus Gloria , Martínez-Robles Violeta , Alonso Rafael , Fernández-Rodríguez Angeles , Arratibel María Carmen , Perera María , Fernández-Miñano Carmen , Fuertes-Palacio Miguel Angel , Vázquez-Paganini Juan Andrés , Gutierrez-Jomarrón Isabel , Valcarce Inés , de Cabo Erik , Sainz Adriana , Fisac Rosa , Aguilar Carlos , Martínez-Badas María Paz , Peñarrubia María Jesús , Garcia-Frade Javier , Calbacho María , de Cos Carmen , González-Silva Manuel , Coria Erika , Alonso Arancha , Casaus Alberto , Luaña Armando , Galán Pilar , Fernández-Canal Cristina , González-Porras José Ramón 
Published: October 2019

Abstract
Background: Eltrombopag is effective and safe for treating chronic immune thrombocytopenia (ITP) patients who have not responded to previous therapy. Interestingly, some patients in whom hemostatic platelet counts are achieved with eltrombopag may sustain the platelet response when eltrombopag ceases to be administered. However, the frequency of sustained responses after discontinuing eltrombopag without additional therapy for ITP is largely unknown.
Methods: A total of 260 adult patients (aged 18 years or more) with primary ITP treated with eltrombopag included in the Spanish Eltrombopag Registry were retrospectively evaluated. The study was performed in accordance with the standards of the Helsinki declaration and approved by the Hospital Universitario de Burgos Ethics Committee.
Results: The median age was 62 [range, 18–93] years. There were 165 women and 95 men. According to the standard definition, patients were allocated to newly diagnosed (n=29), persistent (n=36) and chronic (n=195) ITP groups. The median time from diagnosis to eltrombopag initiation was 24 [range, 1–480] months. The median number of previous therapies was 3 [range, 0–10], including splenectomy (22%), rituximab (23%) and romiplostim (19%). The initial response rate to eltrombopag was 231/260 (89%), including 77% (n=201) cases of complete remission (platelet count ≥100 x 109/L). The median duration of eltrombopag treatment was 6 [range, 1–54] months.
Eltrombopag was discontinued in 80 out of 201 (39.8%) patients who achieved CR. Reasons for eltrombopag discontinuation were: persistent response despite a reduction in dose over time (n=33), platelet count >400x109/L (n=29), patient’s request (n=5), aspartate aminotransferase elevation (n=3), diarrhea (n=3), thrombosis (n=3) and other reasons (n=4). For analysis of discontinuation, patients with follow-up < 6 months (n=15), newly diagnosed ITP (n=11) or patients who received concomitant or previous (6 months before) treatments at the start of eltrombopag use (n=5) were excluded. Of the 49 evaluable patients, 22 (45%) had an immediate relapse after stopping eltrombopag. One patient with sustained response after stopping treatment relapsed at 10 months. A total of 26 patients (53%) showed sustained response after discontinuing eltrombopag without additional ITP therapy, with a median follow-up of 9 [range, 6–25] months. These patients were characterized by a median time since ITP diagnosis of 46.5±114.1 months, with 4/26 having ITP <1 year. Eleven patients (42%) were male and their median age was 59 [range, 18-88] years. They had received a median of four previous treatment lines [range: 0–9 lines] and 11 (42%) were splenectomized. The median platelet count before starting eltrombopag was 22 x 109/L and that before eltrombopag withdrawal was 269 x 109/L.
The main characteristics (age, gender, duration of ITP, prior anti-ITP lines, prior splenectomy, prior rituximab, prior romiplostim, platelet count before starting eltrombopag, duration of eltrombopag treatment, and platelet count before eltrombopag withdrawal) of the 26 patients with sustained response after stopping eltrombopag were compared with those of the 23 patients relapsing after eltrombopag withdrawal. No predictive factors of sustained response after eltrombopag withdrawal could be identified.
Conclusion: Platelet response following eltrombopag cessation may be sustained in nearly half of adult patients with primary ITP after CR with eltrombopag. However, reliable markers for predicting which patients will have this response are lacking.

Disclosures
No relevant conflicts of interest to declare.