Photo courtesy of
St. Michael’s Hospital
New research appears to explain why symptoms and treatment responses vary in patients with immune thrombocytopenia (ITP). The work has also revealed a new potential treatment option.
Researchers previously thought that all ITP antibodies lead platelets to the spleen for destruction.
But the new study, published in Nature Communications, has shown that some ITP antibodies destroy platelets in the liver.
“Every existing treatment for ITP has been dedicated to stopping antibodies from destroying platelets in the spleen, but we’ve discovered that some antibodies actually destroy platelets in the liver,” said study author Heyu Ni, MD, of St. Michael’s Hospital in Toronto, Ontario, Canada.
The discovery was made by analyzing mice treated with two monoclonal antibodies, each targeting a different protein on the surface of platelets—GPIb or GPIIbIIIa.
The researchers found that antibodies targeting GPIb lead to platelet destruction in the liver, and those targeting GPIIbIIIa cause platelet destruction in the spleen.
“By detecting the specific antibodies present in someone with ITP, we may be able to detect where and how the immune system will attack,” Dr Ni said. “And because we now know the liver’s immune response destroys platelets covered with GPIb, we may be able to design new therapies to stop this type of platelet destruction.”
Dr Ni noted that sialidase inhibitors such as oseltamivir phosphate (Tamiflu) may be able to inhibit the liver’s immune response to the platelets. In fact, he and his colleagues used human blood samples to test whether Tamiflu might inhibit antibodies targeting GPIb.
“Using healthy blood samples and ITP antibodies in a test tube, we showed that Tamiflu may impede platelet destruction for those with antibodies that target GPIb,” Dr Ni said.
Based on an early abstract of this research, some ITP patients around the world have been treated with oseltamivir phosphate. These patients were extremely resistant to existing treatments targeting the spleen, and their ITP was considered life-threatening.
Although these instances of experimental treatment have been successful, Dr Ni said more research is needed to verify the safety and efficacy of this approach.
