This clinical trial is designed for men and women with Essential thrombocythemia (ET) and either need to start with therapy to reduce their blood counts, or their current therapy is not sufficiently controlling their disease.
   
The purpose of this study is to evaluate if the study drug, P1101 (Ropeginterferon alfa-2b-njft) can normalize blood counts and the safety of P1101. 
   
Ropeginterferon alfa-2b-njft (P1101) is approved by the U.S. Food and Drug Administration (FDA) for the treatment of polycythemia vera (PV), but is considered investigational in this study which means it has not yet been approved for ET.

Ropeginterferon alfa-2b-njft (P1101) will be administered subcutaneously every 2 weeks. Participants will also need to come into the office regularly to have their vital signs taken, undergo clinical safety laboratory tests, physical examinations, Echocardiogram (ECHO), and other tests as required.
   
Total study participation is expected to last about 15 months.