Interim results of PEANUT: pembrolizumab and nanoparticle albumin-bound paclitaxel (nab-paclitaxel) as salvage therapy for metastatic urothelial carcinoma (UC).
494 Background: Pembrolizumab (pembro) is a new standard of care in chemotherapy (CT) pre-treated patients (pts) with metastatic UC. Nab-paclitaxel (nPtx) demonstrated preliminary activity in advanced UC. In the PEANUT study (NCT03464734) we investigate their combination in advanced UC after CT failure. Methods: In an open-label, single-arm, phase 2 trial, pts receive 200 mg pembro, intravenously (IV), on D1 and 125 mg/m2 IV nPtx on D1 and D8, every 3 weeks, until disease progression (PD) or onset of unacceptable toxicity. Key inclusion criteria are: predominant UC histology, failure of ≤2 platinum-based CT for metastatic disease. Response is evaluated by RECIST v.1.1 criteria every 2 cycles. Biomarkers include PD-L1 expression with the combined positive score (CPS) and comprehensive genomic profiling on tumor and blood samples (FoundationONE and FoundationACT assay). The primary endpoint of the study is the progression-free survival (PFS). The target is to detect an improvement in the median PFS from ≤3.0 months (H0) to ≥5.0 months (H1). Results: Between 01 and 08/2019, PEANUT enrolled 46 pts evaluable for the study endpoint: 26% female, median age 66 y (range 43-78); 70% had failed 1 prior systemic therapy vs 30% 2 prior therapies; 24% had ECOG-performance status 1; 28% had liver metastases. The median TMB was 6.9 mut/Mb. After median follow-up of 5 months, 18 pts have relapsed (39%). The projected median PFS was 7 months (95%CI: 4-not achieved). The confirmed objective response-rate (ORR) was 47.8% (95%CI: 32.9-63.1): 18 partial responses and 4 complete responses (8.7%). Grade 3 treatment-related adverse events (TRAE) were seen in 6 pts (13%). Most common any-grade TRAE included alopecia (91%), asthenia (21.7%), and neutropenia (15%). Neither TMB nor CPS were significantly associated with PFS on univariable analyses. 7/8 pts with PI3KCA mutations in matched tumor/blood samples had an objective response (87.5%). Conclusions: Preliminary results from PEANUT study demonstrated a promising PFS and a clinically meaningful ORR in II-III line setting of advanced UC. Updated data, including mature PFS, duration of response and biomarkers will be presented. Clinical trial information: NCT03464734.