Efficiency and safety of eltrombopag for multi-line failed Chinese patients with immune thrombocytopenia: cases with decreased megakaryocyte response well from single-center experience.

Immune thrombocytopenia (ITP) was defined using the International Consensus Guidelines as a platelet count <100×109/L in the absence of other causes or disorders that may be associated with thrombocytopenia. For patients without response to first-line treatment or refractory, TPO receptor agonist (RA) is an ideal choice. This study was to evaluate the efficiency and safety of eltrombopag for multi-line failed Chinese patients with immune thrombocytopenia (ITP) and analyze the possible factors that may contribute to the differences based on personal characteristics. Thirty-five multi-line failed ITP patients who received eltrombopag treatment were enrolled retrospectively at the First Affiliated Hospital of Zhejiang Chinese Medical University from January 2018 to August 2020. The general information, peripheral hemogram changes, count of bone marrow megakaryocyte (MK), peripheral T cell subsets were recorded, the response, and adverse effects, was evaluated. Results showed that the overall, complete, and partial response rates were 54.3% (n=19), 48.6% (n=17), and 5.7% (n=2) respectively to eltrombopag in our center. The overall response rate of patients with decreased MK was 70%, which was unexpectedly higher than that of the patient with increased or normal MK count (52.9% and 40%, respectively). For patients with poorer eltrombopag response group, more NK cells were found in peripheral blood, and the patient with decreased MK have a higher level of T helper (Th) cells and regulatory T (Treg) cells. Nine eltrombopag-related adverse events were reported, and most commonly were upper respiratory tract infection (8.6%), elevated alanine transaminase (ALT, 5.7%), and venous thrombosis (5.7%). In conclusion, this study revealed that ITP patients with decreased megakaryocyte respond well to eltrombopag, and the abnormality of NK cells may play a role in patients with a poor eltrombopag response.