Phase II study of nivolumab and ipilimumab for advanced bladder cancer of variant histologies (BCVH).

Abstract

4518 Background: Patients with BCVH have poor outcomes and data regarding the management of this heterogeneous group of patients is limited. Nivolumab and ipilimumab has demonstrated safety and efficacy in urothelial carcinoma and other malignancies. In this multicenter, single arm, multi-cohort phase II trial we evaluate the efficacy of nivolumab and ipilimumab in patients with BCVH and other advanced rare genitourinary cancers (NCT 03333616). Herein, we report the preliminary results of the fully accrued BCVH cohort. Methods: Eligible patients had metastatic BCVH, ECOG performance status of 0-2 and were either untreated or had received any number of lines of prior therapy excluding prior immunotherapy. Patients underwent a baseline biopsy and blood collection for correlative studies and received treatment with nivolumab 3 mg/kg and ipilimumab 1 mg/kg intravenously every 3 weeks for 4 cycles with continued maintenance of nivolumab 480 mg IV every 4 weeks. The primary endpoint was overall response rate (ORR) by RECIST 1.1. Results: 19 BCVH patients were enrolled at 4 institutions between 4/2018 and 1/2019: squamous cell (n = 6), small cell (n = 3), adenocarcinoma (n = 3), urachal (n = 5), plasmacytoid (n = 1), and spindle cell (n = 1). 13 (68%) patients had received prior systemic therapy including platinum-based chemotherapy in 92% patients. Median number of cycles of ipilimumab plus nivolumab received was 3 (range 1-8) and median follow-up was 3.6 (0.3-8.8) months. 13 patients had undergone at least one scan; ORR was 31% (4/13, 80%CI: 14-52%), with partial responses seen in small cell carcinoma (n = 2), urachal (n = 1) and a complete response in 1 patient with plasmacytoid carcinoma. 3 patients (16%) developed treatment-related grade 3 toxicities with 1 (5%) grade 4 toxicity. Conclusions: Nivolumab and ipilmumab resulted in objective responses in a subset of patients with BCVH with manageable toxicities. Updated clinical and correlative data will be presented. This combination may warrant further investigation in patients with BCVH, which has substantial unmet needs. Clinical trial information: NCT 03333616.