Thienopyridinone compounds of Formula (I) and pharmaceutically acceptable salts thereof are described. In these compounds, one of X1; X2, and X3 is S and the other two are each independently CR, wherein R and all other variables are as defined herein. The compounds are shown to inhibit HPK1 kinase activity and to have in vivo antitumor activity. The compounds can be effectively combined with pharmaceutically acceptable carriers and also with other immunomodulatory approaches, such as checkpoint inhibition or inhibitors of tryptophan oxidation. Formula (I).