P-38 KEYNOTE-859: A randomized, double-blind, placebo-controlled phase 3 trial of first-line pembrolizumab plus chemotherapy in patients with advanced gastric or gastroesophageal junction adenocarcinoma

A phase 1b multicenter study of TAS-102 in combination with irinotecan in patients with advanced recurrent or unresectable gastric and gastroesophageal adenocarcinoma after at least one line of treatment with a fluoropyrimidine and platinum-containing regimen

TAS-102 is approved for treatment of refractory metastatic gastroesophageal carcinoma (mGEC). This study sought to determine whether the combination of TAS-102 with irinotecan (TASIRI) was safe and effective in previously treated mGEC. This was a single-arm phase 1b study for patients (pts) with mGEC previously treated with at least one line of fluoropyrimidine and platinum-containing regimen. TAS-102 was given at 25 mg/m² twice daily on days 1 to 5 with irinotecan 180 mg/m² on day 1 of a 14-day cycle. The primary endpoint was progression-free survival at 6 months ≥ 35% (PFS-6). 20 Pts were enrolled. The study met its primary endpoint. PFS-6 is 40% (95% CI 19.3-60.0). Median PFS and overall survival are 5.3 months and not reached, respectively. 17 of 20 pts had measurable disease by RECIST criteria. Of the 17, 13 had stable disease and 4 had progressive disease as best response (8 pts had tumor shrinkage < 30%). The disease control rate was 75%. In exploratory analyses, mutations in homologous recombination deficiency genes were associated with inferior PFS (P < 0.03). The most common any grade (G) treatment-related adverse events (TRAE) were nausea (n = 14, 70%), diarrhea (n = 9, 45%), and fatigue (n = 8, 40%). G3-4 TRAE in > 5% of pts were anemia (20%) and neutropenia (10%). 2 serious TRAE were reported: G4 febrile neutropenia (n = 1) and G3 hypotension (n = 1). There was no G5 TRAE. The combination of TASIRI showed encouraging clinical activity with a meaningful improvement in PFS-6 compared to historic controls.

How to Best Exploit Immunotherapeutics in Advanced Gastric Cancer: Between Biomarkers and Novel Cell-Based Approaches

Despite extensive research efforts, advanced gastric cancer still has a dismal prognosis with conventional treatment options. Immune checkpoint inhibitors have revolutionized the treatment landscape for many solid tumors. Amongst gastric cancer subtypes, tumors with microsatellite instability and Epstein Barr Virus positive tumors provide the strongest rationale for responding to immunotherapy. Various predictive biomarkers such as mismatch repair status, programmed death ligand 1 expression, tumor mutational burden, assessment of tumor infiltrating lymphocytes and circulating biomarkers have been evaluated. However, results have been inconsistent due to different methodologies and thresholds used. Clinical implementation therefore remains a challenge. The role of immune checkpoint inhibitors in gastric cancer is emerging with data from monotherapy in the heavily pre-treated population already available and studies in earlier disease settings with different combinatorial approaches in progress. Immune checkpoint inhibitor combinations with chemotherapy (CT), anti-angiogenics, tyrosine kinase inhibitors, anti-Her2 directed therapy, poly (ADP-ribose) polymerase inhibitors or dual checkpoint inhibitor strategies are being explored. Moreover, novel strategies including vaccines and CAR T cell therapy are also being trialed. Here we provide an update on predictive biomarkers for response to immunotherapy with an overview of their strengths and limitations. We discuss clinical trials that have been reported and trials in progress whilst providing an account of future steps needed to improve outcome in this lethal disease.