Thieno[3,2-d]pyrimidines in Anticancer Drug Discovery: Recent Advances in Drug Design and Molecular Targets

The thieno[3,2-d]pyrimidine scaffolds have emerged as an important class of heterocycles in anticancer drug discovery, with clinically advanced drugs olmutinib and pictilisib highlighting their therapeutic potential. This review presents thieno[3,2-d]pyrimidine-containing anticancer agents reported between January 2008 and August 2025, focusing on synthetic methodologies, anticancer-related biological activities, and structure–activity relationships. Thieno[3,2-d]pyrimidine derivatives have been investigated as inhibitors of numerous cancer-related targets, including EGFR, PI3K/mTOR, CDKs, JAK, VEGFR, HDAC, ATR, and other oncogenic proteins. This review also summarizes thieno[3,2-d]pyrimidine scaffolds with anticancer activity, with particular emphasis on the design and synthesis of lead compounds, molecular hybridization strategies, and recent advances in this area. Synthetic pathways for lead compounds are systematically presented and discussed, along with pharmacophoric features. In addition, detailed structure–activity relationship analyses are provided to highlight the influence of heterocyclic fusion, linker optimization, hydrogen-bonding motifs, electronic effects, hydrophobic fragments, and the introduction of hybrid scaffolds on antiproliferative potency, kinase inhibition, selectivity, and multitarget activity. In addition, this review demonstrates the significant potential of thieno[3,2-d]pyrimidine-based scaffolds as a privileged platform for the development of next-generation targeted anticancer agents and offers valuable guidance for future medicinal chemistry research.