{Reference Type}: Journal Article {Title}: Discovery and optimization of narrow spectrum inhibitors of Tousled like kinase 2 (TLK2) using quantitative structure activity relationships. {Author}: Asquith CRM;East MP;Laitinen T;Alamillo-Ferrer C;Hartikainen E;Wells CI;Axtman AD;Drewry DH;Tizzard GJ;Poso A;Willson TM;Johnson GL; {Journal}: Eur J Med Chem {Volume}: 271 {Issue}: 0 {Year}: 2024 May 5 {Factor}: 7.088 {DOI}: 10.1016/j.ejmech.2024.116357 {Abstract}: The oxindole scaffold has been the center of several kinase drug discovery programs, some of which have led to approved medicines. A series of two oxindole matched pairs from the literature were identified where TLK2 was potently inhibited as an off-target kinase. The oxindole has long been considered a promiscuous kinase inhibitor template, but across these four specific literature oxindoles TLK2 activity was consistent, while the kinome profile was radically different ranging from narrow to broad spectrum kinome coverage. We synthesized a large series of analogues, utilizing quantitative structure-activity relationship (QSAR) analysis, water mapping of the kinase ATP binding sites, kinome profiling, and small-molecule x-ray structural analysis to optimize TLK2 inhibition and kinome selectivity. This resulted in the identification of several narrow spectrum, sub-family selective, chemical tool compounds including 128 (UNC-CA2-103) that could enable elucidation of TLK2 biology.