In the phase 2 TROPHY-U-01 trial (NCT03547973) of sacituzumab govitecan-hziy (Trodelvy) plus pembrolizumab (Keytruda) administered in the second line to patients with checkpoint inhibitor–naïve metastatic urothelial cancer, promising anti-tumor efficacy was induced, according to the cohort 3 results presented at the 2022 Genitourinary Cancers Symposium.

At a median follow-up of 5.8 months, patients treated with the combination experienced an objective response rate (ORR) of 34% (95% CI, 20.1%-50.6%), and an ORR of 38% among evaluable patients. One patient experienced a complete response (CR), 13 had partial responses (PR), and 11 achieved stable disease. Of those who experienced stable disease, 4 had stable disease for 6 months or more.

“These data support further evaluation of antibody-drug conjugate/checkpoint inhibitor combination [therapy] in metastatic urothelial cancer in the platinum-refractory setting and probably in earlier lines of therapy in a different patient population,” according to lead author Petros Grivas, MD, PhD, a physician at Seattle Cancer Care Alliance; clinical director of the Genitourinary Cancers Program and associate professor of the Division of Medical Oncology at the University of Washington School of Medicine; and associate professor of Clinical Research Division at Fred Hutchinson Cancer Research Center. “Additional follow up for survival events and biomarkers are ongoing.”

As treatment options for patients with metastatic urothelial cancer remain limited and outcomes poor, investigators aimed to assess other safe and efficacious options to improve patient responses. Investigators theorized that antibody-drug conjugates and checkpoint inhibitors may be a valuable combination strategy capable of providing benefit to patients with metastatic disease.

In cohort 3 of the registrational, open-label multicohort study, investigators enrolled up to 61 patients who were checkpoint inhibitor-naïve with progressive disease following treatment with platinum-based therapies. The cohort received sacituzumab govitecan at a dose of 10 mg/kg on days 1 and 8 every 21 days and 200 mg of pembrolizumab on day 1 every 21 days. Treatment continued until patients experienced unacceptable toxicity or disease progression. Patients needed to be 18 years or older with an ECOG performance status of 0 or 1. Additionally, a creatinine clearance of 30 mL per minute or higher and adequate hepatic function were required.

The study’s primary end point was ORR by investigator review, with key secondary end points including safety, duration of response (DOR), progression-free survival (PFS), and overall survival (OS).

The majority of patients were male (83%) and the median age was 67 years. Most patients were White (54%) and had an ECOG performance status of 1 (61%). In total, 49% and 27% of patients had a Bellmunt risk factor of 1 and 2, respectfully. Investigators also reported 49% of patients underwent neoadjuvant or adjuvant therapy with a median time from end of most recent prior systemic therapy to screening date of 1.6 months. In terms of best response to prior systemic therapy in the metastatic setting, 1 patient had a previous CR and 2 had a PR.

Additional findings from the study indicated that 63% of patients experienced tumor shrinkage and the clinical benefit rate was 61% (95% CI, 44.5%-75.8%). Patients had a median time to response of 2 months and the median DOR was not reached (95% CI, 2.80–not available). The median PFS was 5.5 months (95% CI, 1.7–not reached) and the median OS was not reached.

When examining ORR by subgroup, investigators reported that patients with or without baseline visceral metastases and liver involvement, had rates of 41.7% (95% CI, 15.17%-72.33%) and 31.0% (95% CI, 15.28%-50.83%), respectively. Additionally, for patients who had a Bellmunt risk factor of 0, 1, and 2, the ORRs were 40.0% (95% CI, 12.16%-73.76%), 35.0% (95% CI, 15.39%-59.22%), and 27.3% (95% CI, 6.02%-60.97%).

The most common any grade adverse effects (AEs) in cohort 3 were diarrhea (76%), nausea (59%), and anemia (56%), with grade 3 or higher AEs including neutropenia (27%), diarrhea (24%), anemia (20%), and leukopenia (20%).

The median duration of treatment was 4 months with sacituzumab govitecan and 3.5 months with pembrolizumab. Sixty-eight percent of patients permanently discontinued treatment and 32% were still being treated at the time of data cutoff. Patients who discontinued did so due to progressive disease (51%), withdrawal of consent (5%), and AEs (3%).

Grade 3/4 treatment-related AEs (TRAEs) occurred in 59% of patients, with 39% of patients discontinuing sacituzumab govitecan treatment because of TRAEs. The most common any grade TRAEs were diarrhea (71%), nausea (54%), and neutropenia (44%). Twenty-five percent of patients required a steroid to combat an immune-related AE, with 15% of patients requiring topical and 10% requiring oral steroids for diarrhea (n = 2), pruritis (n = 1), and maculopapular rash (n = 1). Investigators also reported that 29% of patients required granuloma macrophage colony–stimulating factor.

“[Other] TROPHY-U-01 cohorts are being assessed. We have cohort 2 looking at sacituzumab govitecan as a single agent after checkpoint inhibition and cohorts 4 and 5 evaluating sacituzumab govitecan in combination with cisplatin plus or minus avelumab [Bavencio] as induction therapy followed…avelumab [switch maintenance therapy],” Grivas concluded.

_Reference

_{Grivas P, Poussel D, Park CH, et al. TROPHY-U-01 Cohort 3: sacituzumab govitecan (SG) in combination with pembrolizumab (Pembro) in patients (pts) with metastatic urothelial cancer (mUC) who progressed after platinum (PLT)-based regimens. J Clin Oncol. 2022;40(suppl 6):434. doi:10.1200/JCO.2022.40.6_suppl.434}