Trial supports early treatment of lower-risk ET
Efficacy
The primary endpoint was time to ET-related cardiovascular events (as confirmed by a blinded expert panel) or disease progression/worsening (platelet increase >1000 G/L).
The 1-year event-free rate (patients who did not meet criteria for the primary endpoint) was 87% in the AR arm and 69% in the placebo arm (hazard ratio=0.356, P=0.0008).
According to the expert panel, there were 12 ET-related events in 11 patients in the AR arm, as well as 17 such events in 14 patients in the placebo arm. This included major and minor arterial, venous, and bleeding events.
In total, there were 13 patients who had ET-related events or met platelet criteria in the AR arm (13 events) and 26 patients who had ET-related events or met platelet criteria in the placebo arm (30 events).
Nine patients in the AR arm (11.7%) and 18 in the placebo arm (26.1%) changed to high-risk status at some point during the trial (odds ratio=2.67, P=0.033).
Safety
The overall incidence of AEs was 88.3% in the AR arm and 69.6% in the placebo arm. The incidence of treatment-related AEs was 76.6% and 27.5%, respectively.
The incidence of treatment-related serious AEs was 1.3% and 0%, respectively. And the incidence of treatment-related AEs leading to withdrawal was 9.1% and 7.2%, respectively.
Treatment-related AEs occurring in more than 10% of patients in either arm (the AR and placebo arms, respectively) included headache (41.6% and 15.9%), dizziness (35.1% and 14.5%), palpitations (28.6% and 1.4%), and tachycardia (10.4% and 1.4%).
In closing, Dr Gisslinger noted that the primary endpoint of this study was met, and AR allowed for platelet count normalization and delayed progression to high-risk status.
Furthermore, the safety profile of AR is consistent with conventional anagrelide formulations, but AR allows for a more convenient dosing schedule.
Dr Gisslinger concluded, “[T]hese data from the ARETA study support an early treatment concept for all ET patients where platelet count or symptom reduction is a goal and those patients who can be attributed as intermediate-risk patients.” 
