The present invention relates to a dosage regimen for a phosphatidylinositol 3-kinase (PI3K) inhibitor compound of formula (I) or a pharmaceutically acceptable salt thereof. More specifically, the present invention relates to a dosage regimen for the treatment of patients suffering from a proliferative disease, such as, for example, cancer, with a phosphatidylinositol 3-kinase (PI3K) inhibitor compound of formula (I) or a pharmaceutically acceptable salt thereof.