ATR and Ewing sarcoma: Notably, our group and others have shown that Ewing sarcoma tumors are sensitive, in vitro and in vivo in xenograft tumors, to drugs targeting the DNA replication pathway, including drug combinations targeting RNR and the ATR–CHK1 signaling pathway (refs. 3, 17–29; bioRxiv 2024:2023.04.30.538578).