Background: There is no globally established second-line therapy after progression on GemCis in BTC. Although ABC-06 trial showed the clinical benefit of mFOLFOX compared to active symptom control, further investigation is needed. Methods: NIFTY is an investigator-initiated, multicenter, open-label, randomized, phase 2b study. Pts with > 19 years, ECOG PS 0/1, histologically confirmed metastatic BTC, and disease progression on first-line GemCis were eligible. Pts were randomized 1:1 to nal-IRI (70 mg/m2, 90 min) plus 5-FU (2400 mg/m2, 46 hours)/LV (400 mg/m2, 30 min), every 2 weeks or 5-FU/LV, every 2 weeks until disease progression per investigator review or intolerable toxicities (stratification: primary tumor site, prior surgery and institution). Tumor response was evaluated per RECIST v1.1, every 6 weeks (fixed schedule). Primary endpoint is progression-free survival (PFS) per blinded independent central review (BICR). Secondary endpoints were PFS per investigator review, overall survival (OS) overall response rates (ORR), and safety. This study was designed to improve median PFS from 2 months (P0) to 3.3 months (P1; HR 0.6) with 2-sided alpha of 0.05, power of 80% and follow-up loss rates of 10%; a total of 174 pts were required. Results: A total of 178 patients were enrolled between SEP 2018 and FEB 2020; with exclusion of 4 pts who did not receive any study treatment, 174 pts (88 for nal-IRI plus 5-FU/LV group and 86 for 5-FU/LV group) were included in the Full Analysis Set. Median age was 64 yrs (range 37-84); 99/75 pts were male/female; 74/47/53 pts had intrahepatic/extrahepatic/gallbladder cancers. Pts characteristics were well balanced between two arms. With median follow-up duration of 6.1 mo (IQR 3.5-11.2), median PFS per BICR in nal-IRI plus 5-FU/LV group and 5-FU/LV group was 7.1 mo (95% CI, 3.6-8.8) and 1.4 mo (1.2-1.5), respectively (HR=0.56 [0.39-0.81], p=0.0019); median PFS per investigator review was 3.9 mo (2.7-5.2) and 1.6 mo (1.3-2.2), respectively (HR=0.48 [0.34-0.69], p<0.0001). Median OS was 8.6 mo (5.4-10.5) and 5.5 mo (4.7-7.2), respectively (HR=0.68 [0.48-0.98], p=0.0349). ORR was 14.8% and 5.8% per BICR, respectively (p=0.0684) and 19.3% and 2.3% per investigator review, respectively (p=0.0002). Grade ≥3 adverse events (AEs) were reported in 68 pts (77.3%) of nal-IRI plus 5-FU/LV group and 27 pts (31.4%) of 5-FU/LV group. Most common grade ≥3 AEs in nal-IRI plus 5-FU/LV group were neutropenia (n=21, 23.9%), fatigue (7, 8.0%), and nausea (5, 5.7%). Conclusion: Nal-IRI plus 5-FU/LV significantly improved PFS and OS compared to 5-FU/LV in BTC pts who progressed on prior GemCis. Nal-IRI plus 5-FU/LV should be considered as standard second-line therapy for advanced BTC. ClinicalTrials.gov identifier: NCT03524508 Clinical trial information: NCT03524508