Final results of PEANUT: Pembrolizumab and nanoparticle albumin-bound paclitaxel (nab-paclitaxel) as salvage therapy for metastatic urothelial carcinoma (UC).
5017 Background: Pembrolizumab (pembro) is a new standard of care in chemotherapy (CT) pre-treated patients (pts) with metastatic UC. Nab-paclitaxel demonstrated preliminary activity in advanced UC. In the PEANUT study (NCT03464734) we investigated their combination in advanced UC after CT failure. Methods: In an open-label, single-arm, phase 2 trial, pts received 200 mg pembro, intravenously (IV), on D1 and 125 mg/m2 IV nab-paclitaxel on D1 and D8, every 3 weeks, until disease progression (PD) or unacceptable toxicity. Inclusion criteria were: predominant UC histology, failure of ≤2 platinum-based CT for metastatic disease. Response was evaluated by RECIST v.1.1 criteria every 2 cycles. Biomarkers included PD-L1 combined positive score (CPS) and comprehensive genomic profiling on tumor and blood samples (FoundationONE and FoundationACT assay). The primary endpoint was the progression-free survival (PFS). The target was to detect an improvement in the median PFS from ≤3.0 months (H0) to ≥5.0 months (H1). Results: Between 01 and 12/2019, PEANUT study enrolled 65 pts: 24% were female, median age was 69 yrs (IQR: 61-73); 25% had failed > 1 prior systemic therapies; 35% had ECOG-performance status 1; 33% had liver metastases. The median TMB was 6.9 mut/Mb. After median follow-up (FUP) of 5.5 months, 34 pts have relapsed (52.3%). The median PFS was 5 months (95%CI: 3-not reached). The 3-month PFS was 60.7% (95%CI: 49.8-74.1). The confirmed objective response-rate (ORR) was 47.7% (95%CI: 35.2-60.4): 22 partial responses and 9 complete responses (13.8%). The median duration of response was not reached, and 4 pts (6.1%) are long-term responders ( > 12 months). Grade 3 treatment-related adverse events (TRAE) were seen in 20 pts (30.7%). Most common any-grade TRAE included alopecia (76%), neutropenia (33.3%) and asthenia (33%). Neither TMB nor CPS were significantly associated with PFS on univariable analyses. In matched tumor/blood samples, objective responses were seen in 8/10 pts with PI3KCA mutations (80%); 6/10 pts with RB1 alterations (60%); 5/12 pts with DNA damage repair gene alterations (41.7%). Conclusions: Pembro-nab-paclitaxel, the first salvage CT-immunotherapy combination in UC, demonstrated a good tolerability, promising PFS and a clinically meaningful ORR in II-III line setting of advanced UC. As more mature data on biomarker selection emerges, this combination warrants additional studies in either second-line or earlier disease settings. Clinical trial information: NCT03464734 .