#8 Oral Thrombopoeitin (TPO) Receptor Agonist That Stimulates Platelet Production

Overview

Adults suffering from a serious blood disorder that destroys blood platelets and prevents proper clotting now have the option of a new medication that may dramatically improve their health.

An estimated 50,000 to 100,000 people in the United States are diagnosed with chronic immune
thrombocytopenic purpura (ITP). Also known as idiopathic thrombocytopenic purpura, ITP is an autoimmune
disorder that causes the body to mount an attack against the body’s blood platelets, the cells that help blood to clot.

Mistakenly deemed foreign by the immune system, they are then eliminated in the spleen, or sometimes by the
liver, resulting in a lower number of platelets than normal.

The result: Low blood platelet count (thrombocytopenia) that may produce bruising or excessive bleeding. Severe fatigue and complications during surgery and pregnancy are definite possibilities. Although rare, the decreased number of platelets can also trigger a spontaneous cerebral hemorrhage.

No one really knows what causes ITP. While most cases of ITP can be controlled, the response to medication is often variable, typically disappointing, and associated with risk. More drastic measures, like surgical removal of the spleen(splenectomy) are sometimes taken in order to prevent the body from destroying platelet cells within the organ. However, with the spleen gone and no longer filtering the blood stream, a patient is now at higher risk for infection.

The medical and ITP community welcomed the promising results of an international Phase III clinical trial that were the basis of the recent approval of the first oral thrombopoietin (TPO) receptor agonist to treat adults with ITP. The new drug works by stimulating the production of cells in bone marrow that form platelet cells in the blood.

By the end of the 43-day testing period, 59% of subjects receiving the study drug achieved platelet counts at or over 50,000 per microliter of circulating blood, compared with 16% of subjects in the placebo group.

A safe-level platelet count is between 30,000 and 50,000 per microliter of blood. In addition, those test subjects taking the new drug were almost 10 times more likely to reach the target platelet counts as the placebo group.

“It’s important that we now have a promising new drug that can help patients with ITP manage their symptoms,” says Roy Silverstein, MD, Chair, Department of Cell Biology, Cleveland Clinic. “Increasing the production of platelets with this drug may play an important role in managing this disorder.”

Ongoing and future studies will evaluate the safety and efficacy of the drug not only as a long-term treatment for ITP, but as a possible treatment for the 4 million Americans with hepatitis-C-related thrombocytopenia and for patients receiving chemotherapy for leukemia.

Where Are They Now

An estimated 50,000 to 100,000 people in the United States are diagnosed with chronic immune thrombocytopenic purpura (ITP). Patients with ITP have low blood platelet count that may produce bruising or excessive bleeding. While most cases of ITP can be controlled, the response to medication is often disappointing and associated with risk. An oral thrombopoietin receptor agonist has shown high effectiveness in the treatment of ITP by stimulating production of cells in bone marrow that form platelet cells in the blood. Patients taking this new drug were 10 times more likely to reach the target platelet counts as the control group.

This drug has now received FDA approval as a treatment for severe aplastic anemia (2014) and low platelet counts due in patients with chronic Hepatitis C, in addition to its original indication for chronic immune (idiopathic) thrombocytopenia (ITP). In June 2015, it was approved by the FDA to treat children 6 years and older with low platelet counts due to ITP who have not responded to treatment, an important decision as these patients have very few options available to them.

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