CHEK1 and Ewing sarcoma: A clinical trial was also initiated last year (ClinicalTrials.gov No. NCT05275426) to determine whether LY2880070, a Checkpoint kinase 1 (Chk1) inhibitor capable of regulating the G2/M transition of the cell cycle in combination with the chemotherapeutic agent gemcitabine could be an effective treatment for ES (Supplementary Table S2).