The Phase I/II trial included an expansion cohort of 41 patients with metastatic urothelial cancer that progressed after one or more prior systemic therapies. Patients were treated until progression or unacceptable toxicity.
Patients with advanced epithelial cancers, including metastatic urothelial cancer (mUC), have a poor prognosis and this phase I/II trial looks at the safety and efficacy of a novel antibody-drug conjugate, IMMU-132 (hRS7-SN38), also known as Sacituzumab Govitecan. The antibody, hRS7, is a humanized anti-Trop-2 monoclonal antibody attached to SN38 which is the active metabolite of irinotecan (CPT-11). The drug targets Trop-2 which is overexpressed in aggressive epithelial cancers including up to 83% of urothelial tumors and the conjugate binds to Trop-2 and delivers the active metabolite of a topoisomerase I inhibitor.
The primary endpoint was safety and antitumor efficacy was the secondary endpoint.
Similar to data presented at ASCO 2018 for another antibody-drug conjugate, enfortumab vedotin, this trial demonstrates that IMMU-132 (hRS7-SN38), Sacituzumab Govitecan, also has good activity in patients who have not only failed prior platinum chemotherapy but also in patients who have failed prior checkpoint inhibitor therapy. The ongoing trial will further establish its activity.
This was a heavily pre-treated cohort as patients received a median of 3 prior therapies including prior platinum chemotherapy in up to 93% of patients. Furthermore, 34% of patients had received a checkpoint inhibitor (CPI). Overall, the treatment was highly tolerable with grade 3-4 neutropenia being the most commonly seen adverse event (AE) in 39%. The overall response rate (ORR) was 34% with 2 complete responses. The response rate was 29% in patients who had received a previous checkpoint inhibitor. The median overall survival was 16.1 months.