A phase II trial of durvalumab and tremelimumab in metastatic, non-urothelial carcinoma of the urinary tract.

Background: Immune checkpoint blockade has made a significant impact on the clinical outcomes of patients with metastatic urothelial carcinoma (UC). However, evidence for this approach in patients with non-UC of the urinary tract is limited.

Methods: This was a phase II open-label study of durvalumab 1500 mg and tremelimumab 75 mg every 4 weeks for four cycles followed by durvalumab 1500 mg every 4 weeks. Eligible patients had metastatic non-UC with ECOG PS 0-1 regardless of prior therapy (except small cell carcinoma who were pretreated). The primary endpoint was overall response rate per RECIST v1.1. A Simon's minimax two-stage design was employed, with 13 patients planned for stage one. Pre-treatment tumors underwent PD-L1 staining and next-generation sequencing.

Results: Thirteen patients were treated, including seven small cell carcinoma, three squamous cell carcinoma, and three adenocarcinoma. Eleven patients had visceral metastases. No responses were observed; 11 patients had PD and 2 patients had SD. Median PFS was 1.8 months (95% CI, 1.25-not reached [NR]) with a median follow-up of 7.38 months (range, 5.23-21.99 months). Median OS was 6.97 months (95% CI, 4.34-NR). One patient's tumor was PD-L1 positive and all sequenced tumors (n = 8) were microsatellite stable. Grades 3-4 treatment-related adverse events occurred in 38.4% of patients.

Conclusions: In a poor prognosis cohort of patients with non-UC, durvalumab and tremelimumab lacked clinical activity while demonstrating a manageable safety profile.