Avelumab + Trastuzumab/FOLFOX Posts 61% Early Response and 8 mo PFS in HER2‑Positive Metastatic G/GEJ Adenocarcinoma

Avelumab, an anti‑PD‑L1 IgG1, was paired with trastuzumab (HER2 antibody) plus mFOLFOX6 in the single‑arm phase II HCRN GI17‑319 study (NCT03783936). Eighteen previously untreated patients with HER2‑amplified metastatic gastric or gastroesophageal adenocarcinoma (~15% to 23%) received nine induction cycles followed by avelumab + trastuzumab maintenance; at 24 weeks 61% responded (confirmed ORR 50%), and median PFS and OS were 8.0 mo and 13.1 mo, respectively, after 14.6 mo median follow‑up. The regimen was well tolerated with no new grade ≥3 immune‑related signals. Compared with historical trastuzumab + chemo alone (ORR 47%, PFS 6.7 mo, OS 13.5 mo), the combo offers a modest efficacy bump, but it trails the pembrolizumab‑trastuzumab‑chemo triplet that achieved a 74% ORR in KEYNOTE‑811.