Sacituzumab govitecan (IMMU-132) in patients with previously treated metastatic urothelial cancer (mUC): Results from a phase I/II study.

354 Background: Patients (pts) with mUC who progress after platinum (PLT)-based chemotherapy and immune checkpoint inhibitor (CPI) therapy have poor outcomes and limited treatment options. Sacituzumab govitecan (SG) is a novel antibody-drug conjugate. It consists of a monoclonal antibody targeting Trop-2, an epithelial cell surface antigen overexpressed in UC, conjugated to the active metabolite of irinotecan (SN38). Methods: We performed a phase I/II basket study in pts with advanced solid tumors receiving intravenous SG administered on day 1 and 8 of 21-day cycles, until progression or unacceptable toxicity. CT/MRI scans were obtained at 8-week intervals for response assessment. We evaluated pts with mUC who progressed after ≥1 prior systemic therapy and were treated with SG at the 10 mg/kg dose level. Endpoints included safety, objective response rate (ORR) by RECIST 1.1, clinical benefit rate (CBR; complete response [CR], partial response [PR], or else SD ≥6-mo), and Kaplan-Meier estimated duration of response (DOR), progression-free survival (PFS), and overall survival (OS). Results: 45 pts (41M/4F; median age 67, range 49-90; ECOG 0/1: 31%/69%) received a median of 2 (range: 1-6) prior treatment lines, including PLT-based chemotherapy (95%) and CPI (38%). 33 had visceral metastases involving liver (n=15), lung (n=27), and other organs (n=5). The ORR was 31% (14/45), with 2 CR and 12 PR. In pts with visceral involvement, the ORR was 27% (9/33). The ORR in CPI-treated pts was 23% (4/17). The median DOR was 12.6 mo (2 pts continuing >2 y), and the CBR was 47% (21/45). Median PFS and OS were 7.3 mo and 18.9 mo, respectively. The AE profile was consistent with prior reports. Grade ≥3 AEs in ≥5% of pts were neutropenia/neutrophil count decreased (38%), anemia (11%), hypophosphatemia (11%), diarrhea (9%), fatigue (9%), and febrile neutropenia (7%). Conclusions: SG demonstrated clinical activity in pts with relapsed/refractory mUC, including CPI-treated pts and pts with visceral disease. A single-arm, open-label, global phase 2 trial is underway to evaluate antitumor activity and safety of SG in advanced UC.(TROPHY-U-01; NCT03547973). Clinical trial information: NCT03547973.