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Eltrombopag

Orally active thrombopoietin receptor agonist that stimulates thrombopoiesis.

Small molecule, nonapeptide agent.

Eltrombopag, Promacta, is an oral, small non-peptide molecule which binds to the TPO receptor via its transmembrane domain and activates the JAK-STAT and MAP kinase intracellular pathways to increase platelet production.

 

 

Eltrombopag produces a sustained increase in platelet count after 8 days of repeat dosing which decreases to baseline 12 days following discontinuation with a half-life of approximately 12 hours

Trade name Promacta.

Administered orally 50 mg/ day.

Interacts with the transmembrane domain of the thrombopoietin receptor and induces proliferation and differentiation of megakaryocytes.

Activates intracellular signaling pathways JAK-STAT and MAT kinase pathways, which stimulate platelet production.

Increases platelet counts in a dose dependent manner without altering platelet function.

Indicated for the treatment of thrombocytopenia in chronic ITP who have had insufficient response to corticosteroids, immunoglobulins, or splenectomy.

Indicated for the treatment of thrombocytopenia in adults and pediatric patients with chronic ITP who have had an insufficient response to corticosteroids. immunuglobulins, or splenectomy.

Should be used in patients whose thrombocytopenia and clinical condition increases the risk of bleeding, and not for normalizing platelet counts.

The approval of eltrombopag in combination with standard immunosuppressive therapy to include newly diagnosed adult and pediatric patients 2 years and older with severe aplastic anemia.

Eltromopag addition to standard immunosuppressive therapy improved the rate, rapidity, and strength of hematologic response among previously owned treated patients with severe aplastic anemia, without additional toxic effects.

Side effects include headache, dry mouth, abdominal pain, and nausea.

May cause hepatotoxicity, and require regular monitoring serum liver tests.

Drug should be used with caution in the presence of liver disease.

The drug should be discontinued if LFTs are 3 x normal.

Effective in thrombocytopenia secondary to hepatitis C cirrhosis.

A daily dose of 50-75 mg of the drug is an effective short-term treatment for chronic ITP, resulting in elevations of the platelet count to 50,000 or more per cubic millimeter in more than 80% of patients within 2 weeks, platelet counts of 200,000 per cubic millimeter in 37% of patients on 50 mg and in 50% of patients on 75 mg (Bussel).

The recommended starting dose of eltrombopag is 50 mg per day administered orally and then adjusted to a maximum of 75 mg per day to maintain platelet count ≥50,000/μL 

Patients respond to splenectomy refractory disease the same way associated patients that have not undergone splenectomy.

No apparent differences in side effects from placebo.

In ITP thrombopoietin levels are unchanged with the use of this drug.

Associated with an increased risk of thrombosis of the portal venous system as demonstrated in a randomized double blind, placebo controlled study (ELEVATE), 4% vs 1% in controls.

Formulated for a once daily oral administration and should be taken on an empty stomach, and at least 4 hours removed from other medications, foods, and supplements with iron or calcium.

Benefits children with chronic ITP.(Bussel B et al).

Eltrombopag stimulates stem cells and mimics the actions of a natural growth substance for marrow stem cells while suppressing the immune system improving the likelihood, quality and speed of recovery in aplastic anemia patients.

The target of eltrombopag, the MPL receptor, can also be found on blood stem cells.

These rates are about 20% higher than the response rates in our patients treated historically with ATG and cyclosporine alone.

Patients who had shorter telomeres at the start of therapy and therefore more exhausted bone marrow were less likely to respond.

Stimulating remaining stem cells with a drug mimicking the actions of a natural growth substance for marrow stem cells while suppressing the immune system improves the likelihood, quality and speed of recovery in seriously ill patients.

It is a promising therapy for patients with severe aplastic anemia who do not have a stem cell transplantation option or for whom transplantation is too risky.

The recommended starting dose of eltrombopag is 50 mg per day administered orally and then adjusted to a maximum of 75 mg per day to maintain platelet count ≥50,000/μL 

 

A reduced dose of eltrombopag (25 mg per day) should be used in patients with hepatic dysfunction and those of East Asian ancestry.

 

Eltrombopag should not be taken within 1 to 2 hours of a meal, and 4 hours of antacids, dairy products or polyvalent cations (calcium, magnesium, aluminum). 

 

TPO receptor agonists cross the placenta and their safety in pregnancy has not been demonstrated.

Perioperative Eltrombopag May Trump IVIG in Patients With ITP Undergoing Surgery

IVIG is commonly used to raise platelet count in patients with ITP prior to surgery.

But eltrombopag, an oral thrombopoietin receptor agonist, may be a good alternative.

The trial enrolled patients with ITP and a platelet count of <100×109/L before major surgery or <50×109/L before minor surgery.

Patients were randomized to receive daily eltrombopag starting 3 weeks before surgery or IVIG 1 week before surgery.

Ultimately, 30 (78.9%) patients who received eltrombopag achieved perioperative platelet count targets compared with 22 (61.1%) who received IVIG.

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