Refractoriness To Eltrombopag In Adult Primary Immune Thrombocytopenia: Utility Of Next Generation Sequencing Techniques

• One hundred and ten genes of the most important cell-signaling pathways involved in the mechanism of action of eltrombopag were studied.

• Thirteen DNA variants associated with eltrombopag refractoriness in immune thrombocytopenia (ITP) were observed.

Thrombopoietin receptor agonists e.g. eltrombopag are standard second line treatment for immune thrombocytopenia (ITP). Eltrombopag has demonstrated high response rates both in clinical trials and in routine practice studies. However, some ITP patients are refractory to this drug. Next-generation sequencing (NGS) may help us identify underlying molecular biology variants that may be involved in eltrombopag refractoriness. Our multicenter national NGS study investigated 110 genes of the most important cell-signaling pathways involved in the mechanism of action of eltrombopag in 35 refractory cases and 35 eltrombopag-responsive controls. Our refractory population involved 51.4% men with a median age at diagnosis of 48 [range, 38-69] years and a median platelet count of 7 [range, 4-16] x 10⁹/μL. At eltrombopag initiation, 78.3% had chronic ITP with a median platelet count of 8 [range, 5-30] x 10⁹/μL. Treatment with eltrombopag was maintained for a median of 3 [range, 1-9] months before discontinuation. No major grade 3-4 side effects were observed. Several statistical differences were observed in relation to the control responders. Of the total sum of the NGS variants found, thirteen variants with statistical significance (p ≤ 0.05) between case and controls were observed. Two of these have been shown to be associated with cancer. Seven variants are considered benign. Four variants are not previously described and their significance is unknown. To our knowledge, none of the thirteen variants described here has ever been correlated with ITP or eltrombopag refractoriness. Further studies are required to establish their role in this setting.