By Sara Bondell - December 14, 2020
Polycythemia vera is a rare type of blood cancer that causes bone marrow to make too many red blood cells. These excess cells thicken blood and slow its flow, which can cause serious problems such as blood clots.
One of the most common treatments for the disease is aspirin combined with frequent phlebotomies, or blood withdrawals. Phlebotomies help reduce a patient’s risk for blood clots, strokes and heart attacks, but they ultimately lead to iron deficiency.
“As iron is required for red blood cell production, iron deficiency allows hematocrit (the measure of how much of the blood is made up of red blood cells) to be better controlled; however, it also results in a diverse array of symptoms that impairs quality of life,” said Dr. Andrew Kuykendall, an oncologist in the Malignant Hematology Program at Moffitt Cancer Center. “Provisions of iron may help these symptoms, but that leads to red blood cell overproduction and the need for more phlebotomies. It is a Catch-22.”
Because many polycythemia vera patients require phlebotomies and have significant iron deficiency, it is difficult to balance the two. However, a study presented at the annual American Society of Hematology (ASH) meeting, shows a new drug called PTG-300 can be effective in controlling hematocrit and reversing iron deficiency.
Iron deficiency suppresses hepcidin, the body’s main negative regulator of iron absorption. This leads to enhanced iron absorption and increased iron availability for enhanced red blood cell production. PTG-300 mimics hepcidin, leading to an increase in iron stores as well as an iron restricted reduction in hemoglobin and red blood cell count.
Thirteen patients were enrolled in the phase 2 trial and given PTG-300 subcutaneously on a weekly basis. The doses were individualized for each patient. All of the patients experienced a normalization of iron distribution.
“What is shown in the abstracts presented at ASH is that PTG-300 dramatically reduces a patient’s need for phlebotomy,” said Kuykendall. “Ultimately, this means we can offer a well-tolerated therapy that can ostensibly replace the need for phlebotomy and allow for hematocrit control without worsening patients’ quality of life by causing or worsening iron deficiency.”