Sustained response off treatment after fostamatinib in refractory immune thrombocytopenia: A series of four case reports.

INTRODUCTION

A goal of most primary immune thrombocytopenia (ITP) treatments is reducing or discontinuing treatment while maintaining a response including an absence of bleeding events. We present four cases describing treatment with the spleen tyrosine kinase (SYK) inhibitor, fostamatinib, that showed sustained response off treatment (SROT).

CASE PRESENTATIONS

Case 1 was a 66-year-old male with chronic ITP. He was pre-treated with prednisone and rituximab before being in the FIT-2 clinical trial (placebo). He received fostamatinib in the FIT-3 open-label extension for seven weeks and maintained SROT for 2.5 years. Case 2 was a 54-year-old female patient with chronic, highly refractory ITP. SROT was achieved after 6 months of fostamatinib and was maintained for more than 16 months (in remission to date). Case 3 was a 60-year-old male with chronic ITP. He was successfully treated with cycles of corticosteroids for six years prior to fostamatinib. He was treated with fostamatinib plus prednisone for approximately two months. SROT was observed in this patient for one year. Case 4 was a 67-year-old male with persistent ITP. Before fostamatinib, he was unresponsive to high-dose dexamethasone, IVIG, eltrombopag and romiplostim. After 11 months of fostamatinib, his dose was tapered for three months and ultimately discontinued. SROT was observed for more than ten months (in remission to date).

DISCUSSION

These cases emphasize that SROT is achievable with fostamatinib in complex ITP cases unresponsive to multiple previous therapies. Additional research is needed to identify the magnitude of the underlying mechanisms, and the clinical factors associated with, and potentially predictive of, SROT.