This, coupled with mixed reports of PARPi efficacy in trials in other cancer backgrounds of HR-deficiency [31, 33–36, 55–58], led us to examine whether loss of the lysine methyltransferase and pro-NHEJ factor SETD1A influenced PARPi efficacy outside BRCA1. The gene discussed is SETD1A; the disease is hyperinsulinemic hypoglycemia, familial, 4.