Sustained remissions of immune thrombocytopenia associated with the use of thrombopoietin receptor agonists

BackgroundThrombopoietin receptor agonists (TRAs) are effective treatments for immune thrombocytopenia (ITP). However, continuous therapy is generally required to maintain platelet (PLT) count responses. Study Design and MethodsIn this case series, we describe ITP patients from our practice who achieved durable responses to the TRAs romiplostim and eltrombopag. Patients were classified as having a definiteTRA-induced remission if PLT counts increased above 100x10(9)/L after TRA treatment and remained above 100x10(9)/L even after the medication was discontinued; or a possibleTRA-induced remission if PLT counts increased above 100x10(9)/L, remained elevated for at least 3 months after the medication was discontinued, but a subsequent relapse occurred or the effect of other disease-modifying therapies could not be excluded. ResultsOf 31 patients with chronic ITP treated with TRAs in our practice, nine patients achieved a PLT count response with either romiplostim (n=6) or eltrombopag (n=3) that was maintained even after the medications were discontinued. Three patients met criteria for a definite TRA-induced remission, each after exposure to romiplostim. Patients had ITP for a median of 7.8 years and had failed a median of four prior therapies including eight patients who had a splenectomy. We documented a progressive decline in anti-glycoprotein IIbIIIa PLT autoantibodies in one patient while on treatment. ConclusionSome patients with ITP can achieve sustained PLT count responses after the use of TRAs. This observation raises the possibility that these agents may restore immune tolerance to PLT antigens in some patients and supports the practice of down titrating the dose.