Phase II trial of pembrolizumab (PEM) plus granulocyte macrophage colony stimulating factor (GM-CSF) in advanced biliary cancers (ABC).

Abstract

386 Background: The efficacy of immune checkpoint inhibition (CPI) has not been established in ABC. GM-CSF modulates immune effector cells and has demonstrated safety and improved survival (OS) in combination with ipilimumab in melanoma. This phase 2 trial aims to evaluate the efficacy and safety of PEM in combination with GM-CSF in ABC. Methods: Design: Simon’s 2-stage. Key eligibility: ABC with progression/intolerance on ≥ 1 standard therapy, no prior CPI, bilirubin ≤1.5xULN. Treatment: PEM 200 mg IV Q21 days plus 2 cycles of GM-CSF 250 µg SC D1-14 Q21 days in cycles 2 and 3 (Stage 1 Safety Cohort) or in cycles 1 and 2 (Stage 2). Endpoints: 1◦: Progression-free survival at 6 months (PFS6) with H0 25% vs. H1 50%. Key 2◦: Safety, overall response rate (ORR) and duration (DOR), OS, PD-L1 expression. Exploratory: PBMC and tumor immune cell profiles, tumor genotype, microsatellite (in)stability (MSI or MSS). Results: Accrual has completed with 27 patients (pts) enrolled 5/2016-6/2017: F/M 13/14; median age 61 (range 37-77); intrahepatic 19 (70%), extrahepatic 7 (26%), mixed 1 (4%) cholangiocarcinoma; stage IVA/B 85%, II/III 15%; median prior therapies 2 (range 1-6). Adverse events (AE): Related grade(Gr) ≥3 AE occurred in 4/27 (15%) pts including immune-related (ir)AE of Gr4 diabetes mellitus and Gr3 thrombocytopenia in 1 pt each. Gr≤2 irAE in ≥5% were: arthralgia (33%), dry eye/mouth (15%), hyperthyroid/thyroiditis (15%), hypothyroid (15%), neuropathy (11%), rash (11%), and adrenal insufficiency (7%). Steroids were required in 3/27 (11%) pts. Disposition: 19 pts removed for PD, 1 for Gr2 irAE; 7 pts remain active on treatment. Median time on treatment: 6 cycles (range 2-22+). Best response by RECIST 1.1: Partial response (PR) in 5/24 (21%) evaluable pts (1 MSI, 4 MSS); minor regression and ≥50% CA 19-9 decline in 2 additional MSS pts for 11+ and 16+ months. PBMC analyses show changes in expression of activating and inhibitory markers including PD-1 on various immune cell populations. Conclusions: PEM plus induction GM-CSF is safe and tolerable in ABC. Durable radiographic and tumor marker responses including MSS pts warrant further study. PFS6, OS, and correlative analyses are ongoing. Clinical trial information: NCT02703714.