AKT3 and cancer: Triciribine’s target of inhibition Akt, also known as protein kinase B (PKB), is a serine/threonine kinase that has three isolated isoforms: Akt1 (PKBα), Akt2 (PKBβ) and Akt3 (PKBγ), whereby Akt1 is specifically up-regulated in most cancers [24].