SLFN11 and Ewing sarcoma: This has proven to be the case with PARP inhibition (PARPi) which displays synergistic activity in combination with ATRi in BRCA-mutant ovarian (32, 33), SLFN11-negative prostate, leukemia, and Ewing’s sarcoma cell lines (34) as well as in HR-proficient cell lines (35).