Evofosfamide (TH-302) or an analog thereof has a specific inhibitory effect on a cell having a specific gene mutation, in particular on a DNA repair-damaged cell. The cell or tissue has at least one or more gene mutations in BRCA1, BRCA2, FANCD1, FANCD2, ATM, ATR, CHEK1, CHEK2, CTP, BARD1, BRIP1, PALB2, RAD51D, RAD51C, RAD52, RAD54, RAD55, RAD57, FAM175, NBN, Rad50, MER11, p53, NBS1, XRS2, XRCC2, XRCC3, ERCC1, ERCC2, ERCC3, ERCC4, XRCC1, Ku80, MHS6, MGMT, PARP, and ERCC5. For this, a medical use of evofosfamide (TH-302) or an analog thereof in treating tumors or cancer in a cancer patient having the specific gene mutation(s) is provided.