The present invention provides a compound of formula I; wherein R1 is an alkyl pyrazole or an alkyl carboxamide, and R2 is a hydroxycycloalkyl; or a pharmaceutically acceptable salt thereof, and compositions containing these compounds, for use to treat a brain tumor, particularly glioblastoma. The invention provides effective treatment of a brain tumor and can be used by oral administration of a compound of Formula I as further described herein. The invention also provides a method to treat a subject having a brain tumor such as glioblastoma, wherein the method comprises administering to the subject an effective amount of a compound of Formula I. Gene signatures correlated with successful treatment using these methods are also disclosed.