Background: Chemotherapy may work synergistically with immune checkpoint inhibitors by increasing tumor antigen exposure. This 2-part phase I study assessed safety and efficacy of Nivo + nab-P + Gem in APC. Methods: Treatment-naive patients (pts) with APC (locally advanced or metastatic) received nab-P 125 mg/m² + Gem 1000 mg/m² on d 1, 8, and 15 + Nivo 3 mg/kg on d 1 and 15 of each 28-d cycle until disease progression (PD), unacceptable toxicity, or withdrawal. Pts could continue Nivo alone beyond initial PD. Part 1 assessed dose-limiting toxicities (DLTs) and determined the recommended Part 2 dose; Part 2 (expansion phase) further assessed safety. The primary endpoints were DLTs (Part 1) and safety and tolerability (Parts 1 and 2). Key secondary endpoints were response rates, progression-free survival (PFS), and overall survival (OS). Results: As of July 13, 2018, 50 pts with APC were treated: 6 in Part 1; 44 in Part 2. The median age was 67.5 years; 56% were male; 62% had an ECOG PS 1. Of 40 pts with available data, 12 (24%) had ≥ 1% and 6 (12%) had ≥ 5% PD-L1 expression at baseline (data missing for 10 pts). The median follow-up was 11.3 mo. In Part 1, 1 DLT (hepatitis, as evidenced by grade 3 elevated liver function tests; suspected to be related to nab-P + Gem) was reported. In Parts 1 and 2, 48 pts (96%) had ≥ 1 grade 3/4 TEAE; 7 (14%) discontinued treatment due to a TEAE. Most common (> 10%) grade 3/4 TEAEs of special interest were anemia (36%), neutropenia (36%), gastrointestinal events (24%), hepatic toxicity (22%), peripheral neuropathy (16%), thrombocytopenia (12%), and colitis (12%). One grade 5 TEAE, respiratory failure (most likely pneumonitis), was reported. The table shows treatment responses. Of 7 pts (14%) who continued Nivo beyond initial PD, 4 achieved disease control. The median PFS was 5.5 mo (6-mo PFS rate, 47%). The median OS was 9.9 mo (6-mo OS rate, 73%). Conclusions: Combining Nivo with nab-P + Gem is feasible in pts with APC: 1 DLT was reported, and no unexpected safety signals were detected. Clinical trial information: NCT02309177