Additional Study Information: You are being asked to participate in this study because you have been diagnosed with Polycythemia Vera (PV) that requires you to have phlebotomies (blood draws from a vein) to control your symptoms. This type of PV is called Phlebotomy-Dependent Polycythemia Vera (PD-PV). This clinical study is testing a new study treatment for this medical condition. The new study treatment is called ISIS 702843 and will be referred to as study drug throughout the rest of this form. All medications, drugs, and devices must be approved for use by country regulators such as the U.S. Food and Drug Administration (FDA). ISIS 702843 is not an approved study drug for PD-PV and can only be used for research. The study drug is designed to suppress the production of a protein called TMPRSS6. When this happens, your body increases the production of a different protein called hepcidin. Increased hepcidin limits how much iron is available for your body to create hemoglobin and red blood cells (RBCs). People with PD-PV have too many RBCs in their blood, which causes some symptoms of the disease.