A Study to Evaluate Sapablursen (Formerly ISIS 702843, IONIS-TMPRSS6-LRx) in Patients With Polycythemia Vera

The main purpose of this study is to evaluate the efficacy of sapablursen in reducing the frequency of phlebotomy and in improving quality of life assessments in participants with polycythemia vera.

Inclusion Criteria 1. Meet modified World Health Organization (WHO) 2016 diagnostic criteria for polycythemia vera (PV) at the time of clinical diagnosis 2. Participant must be phlebotomy dependent. 3. Participants do not need to be on cytoreductive therapy and do not need to have been previously treated with cytoreductive therapy. If the patient was previously on cytoreductive therapy it must have been discontinued at least 3 months prior to Screening, with all associated AEs resolved. If the patient is currently on cytoreductive therapy they must be on a stable dose of hydroxyurea, recombinant or PEGylated interferon, or ruxolitinib for at least 3 months prior to Screening. Exclusion Criteria 1. Meets criteria for post-polycythemia vera myelofibrosis (PPV-MF) as defined by the International Working Group- Myeloproliferative Neoplasms Research and Treatment (IWG-MRT) 2. Moderate to severe splenic pain or spleen-related organ obstruction 3. Active or chronic bleeding within 1 month of Screening, significant concurrent/recent coagulopathy, history of immune thrombocytopenic purpura (ITP) 4. Known primary or secondary immunodeficiency 5. Active infection with human immunodeficiency virus (HIV), hepatitis C, or hepatitis B. 6. Active infection requiring systemic antiviral or antimicrobial therapy or active novel coronavirus disease (Covid-19) infection 7. Malignancy within 5 years, except for basal or squamous cell carcinoma of the skin or carcinoma in situ of the cervix or non-metastatic prostate cancer that has been successfully treated 8. Surgery requiring general anesthesia within 1 month prior to Screening