Interferon therapies are well established as treatment options for some types of cancer, but they have not been used to treat cancers characterized by the overproduction of blood cells. The FDA has now approved a PharmaEssentia interferon drug for polycythemia, a rare blood cancer that can progress to a range of severe cardiovascular problems.
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The agency’s late Friday regulatory nod for the PharmaEssentia drug, ropeginterferon alfa, makes it the first drug therapy approved for polycythemia vera. It’s also the company’s first FDA-approved product. Taiwan-based PharmaEssentia, which operates U.S. headquarters in Burlington, Massachusetts, will market its drug under the name Besremi.
The cause of polycythemia vera is a mutation in stem cells of the bone marrow, which is where blood cells are produced. The high red blood cell levels caused by the disorder lead to blood that is abnormally thick, which also means that blood clots may form more easily, putting patients at risk of a heart attack or stroke. Polycythemia vera can progress to other types of blood cancers.
According to the FDA, polycythemia vera affects about 6,200 American annually. Treatment options include phlebotomy, in which blood is withdrawn to bring the red blood cell count closer to normal. However, this procedure does not address the high white blood cell and platelet levels. Another treatment option is chemotherapy or other drugs that suppress blood cell formation. But the National Organization for Rare Disorders notes that some drug therapies that work in this way also increase the risk of leukemia.
The PharmaEssentia drug is an engineered version of interferon alpha, a signaling protein produced by the immune system that regulates and activates the immune response. Interferon therapies have been developed and approved for some viral infections and cancers. The way that the PharmaEssentia drug addresses polycythemia vera is not fully understood. It’s believed to work by attaching to interferon alpha receptors, which in turn starts a signaling cascade that reduces the bone marrow blood cell production.
PharmaEssetia engineered Besremi in a way that makes its effect in the body long lasting. The drug is dosed as a subcutaneous injection given every two weeks. The FDA said that if a patient responds to treatment and is able to maintain normal red blood cell levels for at least a year, dosing frequency may be reduced to every four weeks.
Besremi was evaluated in a seven-and-a-half year open label study. The 51 patients in the study received treatment with the PharmaEssentia drug for an average of five years. The main goal was to assess how many patients achieved a complete hematological response—a red blood cell volume of less than 45% without a recent phlebotomy, white cell and platelet counts at normal levels, a normal spleen size, and no blood clots. The FDA said that 61% of patients in the study achieved this response.
Side effects reported in the clinical trial included elevated liver enzymes, low levels of white blood cells and platelets, joint pain, fatigue, and upper airway infections. The FDA cautioned that more severe side effects may include urinary tract infection, depression, and stroke-like attacks. Those risks were flagged in a black box warning on the drug’s label. The warning cautions physicians and patients that that like other interferon alfa products, Besremi may cause or aggravate neuropsychiatric, autoimmune, ischemic, and infectious disorders. These conditions may become life-threatening. The label advises clinicians to monitor patients closely and withdraw treatment if symptoms of these disorders worsen.
The drug also poses the risk of harm to an unborn fetus. The FDA said women who could be pregnant should be tested for pregnancy before using the PharmaEssentia drug.
FDA approval of Besremi follows the agency’s rejection of PharmaEssentia’s drug application in March. At that time, the company said the FDA cited Covid-19 travel restrictions that delayed inspection of a manufacturing facility in Taiwan. PharmaEssentia resubmitted its drug application in May.
Besremi was previously approved by the European Medicines Agency in 2019. It also has regulatory approvals in Taiwan and South Korea. PharmaEssentia said the drug will be available in the U.S. in coming weeks. The drug is also in Phase 3 clinical testing as a treatment for essential thrombocythemia, a condition in which the body produces too many platelets. The company’s pipeline includes clinical-stage compounds for breast and gastric cancers, the liver infection hepatitis D, and the skin condition actinic keratosis.
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