CS cell lines harboring Signature-3/HRD (3 OCS/1 UCS) were significantly more sensitive to olaparib when compared to HRP cell lines (5 UCS/1 OCS) [mean IC50 ± SEM = 2.94 μM ± 0.07 vs mean ± SEM = 23.3 μM ± 0.09, (p = 0.02), respectively]….In vivo, olaparib significantly impaired HRD CS xenografts tumor growth (p = 0.0008) and increased overall animal survival (p < 0.0001)....OCS and UCS cell lines harboring HRD signature-3 were significantly more sensitive to olaparib in vitro and in vivo when compared to HRP CS.