The application discloses tricyclic pyrazolopyrmidine of formula (I), their activity toward the heat shock protein 90 (HCP90), and their use as anti-cancer agents. Examples of these compounds are: 2-{ 4-amino-2-[(3-chloro-4-methoxy-5-methylpyridin-2-yl)methyl]-2,7-dihydro-6-thia-1,2, 3, 5-tetraazabenzo[cd ]azulen-8-yl} -N-methylacetamide, 2-{ 4-amino-2-[(3-bromo-4-methoxy-5-methylpyridin-2-yl)methyl]-2,7-dihydro-6-thia-1,2,3,5-tetraazabenzo[cd]azulen-8-yl} -N-methylacetamide, 2-{ 4-amino-2-[(3-bromo-4-methoxy-5-methylpyridin-2-yl)methyl]-2,7-dihydro-6-thia-1,2,3,5-tetraazabenzo[cd]azulen-8-yl} acetamide, 2-{ 4-amino-2-[(3-chloro-4-methoxy-S-methylpyridin-2-yl)methyl]-2,7-dihydro-6-thia-l,2,3,S-tetraazabenzo[cd]azulen-8-yl} -N-(2-fluoroethyl) acetamide.
