Exposure-response (E-R) analysis of rilotumumab (R, AMG 102) plus epirubicin/cisplatin/capecitabine (ECX) in patients (pts) with locally advanced or metastatic gastric or esophagogastric junction (G/EGJ) cancer.

Abstract

2535 Background: R is an investigational, fully human monoclonal antibody to hepatocyte growth factor/scatter factor (HGF/SF), the only known MET receptor ligand. In a double-blind, placebo-controlled, phase 2 trial of 121 pts with G/EGJ cancer, R (7.5 or 15 mg/kg) + ECX showed trends for improved overall survival (OS) and progression-free survival (PFS) compared to ECX alone (placebo, P). Methods: E-R analyses were performed using pharmacokinetic (PK), biomarker, efficacy, and safety data. A population PK model was used to evaluate covariate effects (eg, demographics, ECX, and MET status) on R PK and predict individual R exposure (trough steady-state Cmin [C]). The effect of C on OS/PFS was evaluated with Kaplan-Meier estimates and Cox proportional hazards models. Covariate effects for OS/PFS were evaluated with multivariate analysis. The relationships between adverse events of interest (AEs), lab values, and C were analyzed with descriptive statistics and linear regression models. Results: R showed linear PKs that were unaffected by ECX or MET levels. Pts who received R + ECX were divided into low C (CL) and high C (CH) groups by the median C (94 µg/mL). Median PFS was 4.2, 4.5, and 6.9 months in the P, CL, and CH groups; median OS was 8.9, 9.5, and 13.3 months. Improved OS/PFS in CH and improved PFS in CH and CL groups (vs P) were seen after adjusting for baseline covariates. Pts with tumors that expressed high MET levels (METHigh: > 50% cells positive) showed greater improvement in OS in the CH vs CL group. No improvement in OS was seen in METLow pts (CH and CL groups) compared to placebo (see Table). No relationship was seen between R exposure and AEs or lab values. Conclusions: Higher R exposure was associated with improved OS/PFS in METHigh pts without increased toxicity, supporting further study of R + ECX in G/EGJ cancer. [Table: see text]