Inclusion Criteria  Meet modified World Health Organization (WHO) 2016 diagnostic criteria for polycythemia vera (PV) at the time of clinical diagnosis Participant must be phlebotomy dependent The participant's cytoreductive therapy must either be discontinued at least 3 months prior to Screening, OR participant must be on a stable dose for at least 3 months prior to Screening  Exclusion Criteria  Meets criteria for post-polycythemia vera myelofibrosis (PPV-MF) as defined by the International Working Group- Myeloproliferative Neoplasms Research and Treatment (IWG-MRT) Moderate to severe splenic pain or spleen-related organ obstruction Active or chronic bleeding within 1 month of Screening, significant concurrent/recent coagulopathy, history of immune thrombocytopenic purpura (ITP) Known primary or secondary immunodeficiency Active infection with human immunodeficiency virus (HIV), hepatitis C, or hepatitis B. Active infection requiring systemic antiviral or antimicrobial therapy or active novel coronavirus disease (Covid-19) infection 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 Surgery requiring general anesthesia within 1 month prior to Screening