Pembrolizumab and nab-paclitaxel as salvage therapy for platinum-treated, locally advanced or metastatic urothelial carcinoma: interim results of the open-label, single-arm, phase II PEANUT study

Background: Pembrolizumab is a new standard of care for patients with platinum-treated, metastatic urothelial carcinoma (UC). Nab-paclitaxel is active in advanced UC. In the PEANUT study (NCT03464734) we investigated their combination in advanced UC. Patients and methods: PEANUT was an open-label, single-arm, phase II trial that included patients who had failed one or two chemotherapy regimens, including platinum chemotherapy. Biomarker analyses focused on programmed cell-death ligand-1 combined positive score (CPS) and comprehensive genomic profiling on tumor samples and circulating tumor DNA. Patients received 200 mg pembrolizumab on day 1 (D1), and 125 mg/m2 nab-paclitaxel on D1 and D8, every 3 weeks, until disease progression or unacceptable toxicity. The primary end point was progression-free survival (PFS) according to RECIST (v1.1). The assumption was to detect an improvement in the median PFS from ≤3.0 months (H0) to ≥5.0 months (H1). Results: Between January 2019 and January 2020, the PEANUT study enrolled 70 patients: 24% had failed two prior systemic therapies; 31% had an Eastern Cooperative Oncology Group (ECOG) performance status of 1; and 28.6% had liver metastases. After a median follow-up of 9.8 months, 40 patients have relapsed (57.1%). The median PFS was 5.9 months [95% confidence interval (CI) 3.1–11.5]. The confirmed objective response rate (ORR) was 38.6% (95% CI 27–51) with 17 partial responses and 10 complete responses (14.3%). The median duration of response was not reached. Five patients (7.1%) had ongoing responses lasting >12 months. The most common any-grade treatment-related adverse events included alopecia (71.4%), neutropenia (32.9%), and peripheral neuropathy (34.3%). Neither tumor mutational burden nor CPS was significantly associated with PFS at univariable analyses. The single-arm design of the trial was the major limitation. Conclusions: Pembrolizumab combined with nab-paclitaxel, as second- and third-line chemoimmunotherapy for metastatic UC, showed a favorable safety profile, durable PFS, and a clinically meaningful ORR in these preliminary analyses. This combination warrants additional randomized studies in earlier disease stages. ClinicalTrials.gov number: ClinicalTrials.gov NCT03464734; https://clinicaltrials.gov/ct2/show/NCT03464734.