Rare Disease Report

Rare Blood Disorder Treatment Gets Orphan Drug Designation

MARCH 07, 2018
Mathew Shanley
Protagonist Therapeutics has announced that the U.S. Food and Drug Administration (FDA) granted Orphan Drug Designation to PTG-300.

PTG-300 is a sub-cutaneous injectable hepcidin mimetic for the treatment of beta-thalassemia, a rare genetic blood disorder. Hepcidin is a natural peptide hormone that is the main regulatory hormone governing iron absorption, recycling and utilization by the body.

The condition is characterized by iron overload, and results in the impaired production of red blood cells. It can eventually lead to life-threatening chronic anemia, typically requiring regular and life-long blood transfusion for survival. It is inherited in an autosomal recessive pattern, which means that both copies of the HBB gene in each cell have mutations.

According to the National Institute of Health (NIH), the parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they don’t normally exhibit signs and symptoms of the condition. In some instances, though, people with only one HBB gene mutation in each cell can develop mild anemia, and these mildly-affected people are said to have “thalassemia minor.”

In a small percentage of families, the HBB gene mutation is passed down in an autosomal dominant manner. In these cases, 1 copy of the altered gene in each cell is adequate to cause the presentation of beta-thalassemia.

The designation was based on data from a recently completed Phase 1 study in which PTG-300 exhibited the ability to achieve dose-related and sustained reductions in serum iron levels in normal healthy volunteers.

"As a hepcidin mimetic, PTG-300 is designed to help reduce these excessive iron levels and thereby it may lead to improvements in anemia and decreased need for blood transfusions and chelation therapy,” said David Y. Liu, Ph.D., Chief Scientific Officer and Head of Research and Development of Protagonist Therapeutics in a press release.

Over time, the blood transfusions commonly received by this patient population can lead to excessive iron levels in the body, which can be toxic and consequently result in end-stage damage to vital organs like the liver and the heart. Throughout the Phase 1, PTG-300 was well tolerated with no serious adverse events (AEs) or dose-limiting toxicities.

Protagonist Therapeutics believes that PTG-300 therapy could also potentially provide clinical benefit in other diseases such as myelodysplastic syndrome (MDS), hereditary hemochromatosis (HH), polycythemia vera (PCV), siderophilic infections, and liver fibrosis, providing additional opportunities for future development.

Per the NIH, thousands of infants with beta-thalassemia are born each year. The disease occurs most frequently in people from Mediterranean countries, North Africa, the Middle East, India, Central Asia, and Southeast Asia.

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