Eltrombopag Olamine

Description

Eltrombopag Olamine Tablet is an oral, small molecule, non-peptide thrombopoietin receptor agonist (TPO-RA) that acts to increase the number of platelets. Eltrombopag Olamine is a drug used to treat thrombocytopenia (a low blood platelet count) in adults and children with chronic immune thrombocytopenic purpura that did not improve with other treatments. Eltrombopag olamine is also used to treat severe aplastic anemia. It is also being studied in treating other conditions and types of cancer. Eltrombopag olamine binds to the thrombopoietin receptor, which causes the bone marrow to make more platelets.

The Uses of Eltrombopag Olamine

Treatment of chemotherapy-induced thrombocytopenia and treatment of immune thrombocytopenic purpura.

Clinical Use

Eltrombopag olamine, a thrombopoietin receptor (TpoR) agonist, was approved in late 2008 for the once-daily, oral short-term and long-term treatment of adult patients with previously treated chronic idiopathic thrombocytopenic purpura (ITP). It is the first small-molecule TpoR agonist and was launched in the U.S. for this indication in 2009 by GlaxoSmithKline (GSK). Because eltrombopag is a small molecule, the drug is administered orally and has a reduced potential for causing an immune system reaction versus alternative protein-based therapies. In 2010, eltrombopag was approved in Europe for the long-term treatment of adult patients with previously treated chronic ITP.

Synthesis

The synthesis began with the nitration of 2-bromophenol (39) with sodium nitrate and sulfuric acid in water at 10 ℃ to give 2-bromo-6-nitrophenol (40) in 25% yield, which was methylated using methyl iodide and potassium carbonate in refluxing acetone providing 2-bromo- 6-nitroanisole (41) in 76% yield. Suzuki coupling of compound 41 with 3-carboxyphenyl boronic acid with Pd(PPh3)4 and 2 M sodium carbonate in refluxing dioxane gave 20-methoxy- 30-nitrobiphenyl-3-carboxylic acid (42) in 47% yield as a tan powder. Demethylation using 48% HBr (aq) in refluxing acetic acid resulted in a 79% yield of 20-hydroxy-30-nitrobiphenyl-3-carboxylic acid (43). The nitro group of compound 43 was reduced via catalytic hydrogenation at 50 psi at room temperature over Pd/C in mixed ethanol/3 M aq NaOH solution to give 30-amino-20-hydroxybiphenyl- 3-carboxylic acid (44) in quantitative yield. The intermediate 1-(3,4-dimethylphenyl)-3-methyl-2,5-dihydro-1Hpyrazol- 5-one (47) was prepared by condensing of 3,4-dimethylphenyl- hydrazine 45 with ethyl acetoacetate 46 with sodium acetate in refluxing acetic acid in 76% yield. Treatment of (44) with sodium nitrite in 1 M HCl at 5 ℃, followed by condensation with 1-(3,4-dimethylphenyl)-3-methyl-2,5-dihydro-1H-pyrazol-5-one (47) at a constant pH of 7¨C8 via the addition of sodium bicarbonate and ethanol afforded eltrombopag in 32% yield. Finally, eltrombopag was treated with hydroxyl ethylamine to give eltrombopag olamine.