The present invention relates to compounds of formula (I) as defined herein and their salts, hydrates and solvates. The present invention also relates to pharmaceutical compositions comprising a compound of formula (I) and to the use of a compound of formula I for the treatment or prevention of PRMT5-mediated disorders such as cancer. 本発明は、本明細書に定義した式(I)の化合物並びにその塩、水和物及び溶媒和物に関する。本発明は、式(I)の化合物を含む医薬組成物に、及びがん等のPRMT5媒介性障害の治療又は予防への式Iの化合物の使用にも関する。