A Study of Rusfertide in Adults With Polycythemia Vera (PV)

Polycythemia vera (PV) is a long-term condition in which the bone marrow makes too many red blood cells (RBCs). Bone marrow is the soft tissue inside the large bones where blood cells are made. When there are too many RBCs, called erythrocytosis, the blood can become thicker and move less easily through blood vessels and organs. This can raise the risk of blood clots (thrombosis) in veins or arteries. Sometimes, these clots can be life-threatening and may cause a stroke or heart attack. Treatment aims to keep the percentage of RBCs in the blood (hematocrit) in a safe range. For adults with PV, this means keeping the hematocrit below 45%. This helps lower the blood thickness and the risk of thrombosis. PV can also be linked to low iron levels (iron deficiency), because the body uses iron to make more RBCs. Many people with PV are treated with blood removal (phlebotomy) to lower RBC levels in the blood. This can worsen the iron deficiency, because each blood removal also takes iron out of the body. Rusfertide is a medicine that lowers the amount of iron available in the blood. It works like hepcidin, a natural hormone that helps control iron levels in the body. By limiting iron available for RBC production, rusfertide may help keep hematocrit below 45% and may improve symptoms. It may also reduce, or even remove, the need for phlebotomy in people. The main aim of this study is to check how well rusfertide works compared with placebo to lower the number of phlebotomies. A placebo looks like rusfertide but does not have any medicine in it. Other aims are to learn how safe rusfertide is compared with placebo and to understand how well it works to reduce the need for phlebotomy and to keep hematocrit levels under control. The study also wants to learn how rusfertide moves through the body (pharmacokinetics) and how it affects the body (pharmacodynamics or PD). This study has 4 parts that follow each other: * In part 1a, participants will receive either rusfertide or placebo. * In part 1b, all participants will receive rusfertide. * In part 2, participants can continue to receive rusfertide if they benefit from treatment with rusfertide. * Part 3 will include participants who finish Part 2 and still benefit from rusfertide. During the study, participants will visit the study clinical several times at fixed timepoints.

Inclusion criteria: 1. Male and female participants aged 18 (or the minimum country specific age of consent if greater than \[\>\]18) years or older. 2. Participant understands the study procedures, is willing and able to adhere to study requirements and agrees to participate in the study by giving written informed consent. 3. Meet revised 2016 World Health Organization (WHO) criteria for the diagnosis of PV. 4. Phlebotomy requiring defined as ALL of the following: 1. At least 3 phlebotomies due to inadequate hematocrit control in 28 weeks before randomization or at least 5 phlebotomies due to inadequate hematocrit control in 1 year before randomization, and 2. Last phlebotomy due to inadequate hematocrit control within 3 months before randomization, and 3. No phlebotomy within 6 days prior to randomization (do not include day of phlebotomy and day of randomization in the 6-day count). 5. Complete blood count (CBC) values immediately prior to randomization: 1. Hematocrit \