Clinical Data In the Phase 1/2 study, 54 patients with ER+/HER2– mBC who received sacituzumab govitecan at a dose of 10 mg/kg on days 1 and 8 of three-week cycles showed a confirmed overall response rate (ORR) of 31 percent (17/54), based on local investigator assessment in accordance with RECIST 1.1. The estimated median duration of response was 7.4 months (95% CI: 4.4, 18.3), the clinical benefit rate (CBR; partial response and stable disease lasting for six months and longer) was 48 percent (26/54). At the time of data cutoff on April 30, 2018, seven responders were still receiving sacituzumab govitecan.In the subgroup of 37 patients who also had received prior CDK 4/6 inhibitors, ORR was 24 percent (9/37). In the difficult-to-treat subgroup of patients with liver metastases, CBR was 48 percent (21/44). The estimated median progression-free survival was 6.8 months (95% CI: 4.6, 8.9).