Andecaliximab/GS-5745 alone and combined with mFOLFOX6 in advanced gastric and gastroesophageal junction adenocarcinoma: Results from a phase 1 study

Purpose: Matrix metalloproteinase-9 (MMP9) is implicated in pro-tumorigenic processes. Andecaliximab (GS-5745, a monoclonal antibody targeting MMP9) was evaluated as monotherapy and in combination with mFOLFOX6. Experimental Design: Three dosages of andecaliximab monotherapy (200, 600, and 1800 mg IV every 2 weeks [q2w]) were investigated in patients with advanced solid tumors (n=13 in a 3+3 design). After determining a recommended dose, patients with advanced HER2-negative gastric/gastroesophageal junction (GEJ) adenocarcinoma (n=40) received 800 mg andecaliximab + mFOLFOX6 q2w. Pharmacokinetics, pharmacodynamics, safety, and efficacy were assessed. Results: Andecaliximab monotherapy demonstrated no dose-limiting toxicity (DLT) in any cohort, displaying target-mediated drug disposition at the lowest dose (200 mg) and linear pharmacokinetics at higher doses. Based on target engagement, recommended doses for further study are 800 mg q2w or 1200 mg q3w. Maximal andecaliximab target binding, defined as undetectable andecaliximab-free MMP9 in plasma, was observed in the gastric/GEJ adenocarcinoma cohort. We observed no unusual toxicity, although there were 4 deaths on study not attributed to andecaliximab treatment. In first-line patients (n=36), median progression free survival (PFS) was 9.9 months (95% CI 5-13.9 months) and the overall response rate (ORR) was 50%. Among all patients (n=40), median PFS was 7.8 (90% CI, 5.5-13.9) months and ORR was 48%, with a median duration of response of 8.4 months. Conclusions: Andecaliximab monotherapy achieved target engagement without DLT. Andecaliximab + mFOLFOX6 showed encouraging clinical activity without additional toxicity in patients with HER2-negative gastric/GEJ adenocarcinoma. A phase 3 study evaluating mFOLFOX6 +/- andecaliximab in this setting is ongoing.

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