The present invention relates to bicyclic heterocycles which are inhibitors of BET proteins such as BRD2, BRD3, BRD4, and BRD-t and are useful in the treatment of diseases such as cancer.Cette invention concerne des hétérocycles bicycliques qui sont des inhibiteurs des protéines BET, telles que BRD2, BRD3, BRD4, et BRD-t, et qui sont utiles dans le traitement de maladies telles que le cancer.