Romiplostim Treatment Mimicking Cyclic Thrombocytopenia In 3 Patients with Chronic Idiopatic Thrombocytopenic Purpura

The thrombopoietic growth factors (TGFs) are a novel class of compounds for the treatment of chronic immune thrombocytopenia (ITP). The first of these agents to receive regulatory approval, romiplostim and eltrombopag, have demonstrated impressive efficacy and tolerability in randomized controlled trials and open-label extension studies of several years duration and stand poised to revolutionize the management of ITP. Nonetheless, critical questions regarding the safety of these agents, remain partially unanswered. The aim of this report is to focus on the incidence of thrombocytosis and rebound thrombocytopenia mimicking cyclic thrombocytopenia in a series of 15 patients treated with romiplostim in a single institution.

15 patients (8 M and 7 F, median age 45 years range 21–76) with chronic ITP (median onset 6 years, range 1–11), 1/15 splenectomized, plts median 2 ×10⁹/L, (range 18–24) were treated with Romiplostim initial dose of 1 mg/kg, weekly checks, with only weekly increase of 1 mg/kg to reach a platelet count ≥ 50 × 10⁹/L. The target platelet count range was 50 to 250 × 10⁹/L. Twenty-two percent of patients (3/15) were receiving concurrent treatment for ITP (corticosteroids, danazol) at the time of first romiplostim dose. These medications were discontinued after platelet counts reached 50 × 10⁹/L.

A platelet response had been achieved by 30% of patients after the first dose and by 51% of patients after the third dose. Treatment response was observed in 100% of pts treated after 6 weeks. In three patients after the eighth week, with average values plts 120×109/l, the subsequent administration of the drug led to an increase in platelet count > 1000×109/l, with rapid fall to <30 ×109/l at the third week suspension in 2/3, while the third patient is in CR at six months follow-up despite treatment was stopped.

According to an analysis of all patients with ITP treated with romiplostim in 4 controlled trials have been reported 3 thrombocytosis events in 271 pts (1.1%). In our series the percentage was 20% (3/15), much higher than that reported in the literature, with no thrombotic complications related. Interesting in a case CR was still maintained at 8 months of follow-up despite cessation of treatment. It would be very useful to create a network of information between users of romiplostim to evaluate on a larger series, the true incidence of thrombocytosis and any related thrombotic phenomena associated in a day by day clinical practice.

No relevant conflicts of interest to declare.