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Currently, the only approved treatments for gastrointestinal stromal tumor (GIST) are tyrosine kinase inhibitors (TKI), which eventually lead to the development of secondary resistance mutations in KIT or PDGFRA and disease progression. Herein, we identified G protein-coupled receptor 20 (GPR20) as a novel non-tyrosine kinase target in GIST, developed new GPR20 IHC, and assessed GPR20 expression in cell lines, patient-derived xenografts, and clinical samples from two institutes (United States and Japan). We studied GPR20 expression stratified by treatment line, KIT expression, GIST molecular subtype, and primary tumor location. We produced DS-6157a, an anti-GPR20 antibody-drug conjugate with a novel tetrapeptide-based linker and DNA topoisomerase I inhibitor exatecan derivative (DXd). DS-6157a exhibited GPR20 expression-dependent antitumor activity in GIST xenograft models including a GIST model resistant to imatinib, sunitinib, and regorafenib. Preclinical pharmacokinetics and safety profile of DS-6157a support its clinical development as a potential novel GIST therapy in patients who are refractory or have resistance or intolerance to approved TKIs. SIGNIFICANCE: GPR20 is selectively expressed in GIST across all treatment lines, regardless of KIT / PDGFRA genotypes. We generated DS-6157a, a DXd-based antibody-drug conjugate that exhibited antitumor activity in GIST models by a different mode of action than currently approved TKIs, showing favorable pharmacokinetics and safety profiles. This article is highlighted in the In This Issue feature, p. 1307 ., (©2021 American Association for Cancer Research.)

Background: Trifluridine/tipiracil showed activity and was well tolerated in a phase 2 study of pretreated patients with advanced gastric cancer done in Japan. We investigated whether the treatment was efficacious compared with placebo in a global population., Methods: TAGS was a randomised, double-blind, placebo-controlled, phase 3 trial done in 110 academic hospitals in 17 countries. Patients aged 18 years or older with histologically confirmed, non-resectable, metastatic gastric adenocarcinoma (including adenocarcinoma of the gastroesophageal junction) as defined by the American Joint Committee on Cancer staging classification (7th edition) who had received at least two previous chemotherapy regimens and had experienced radiological disease progression were eligible for inclusion. Patients were randomly assigned (2:1) via dynamic randomisation from a centralised interactive voice-response system to receive either oral trifluridine/tipiracil (35 mg/m 2 twice daily on days 1-5 and days 8-12 every 28 days) plus best supportive care or placebo plus best supportive care. Participants were allocated to groups by study-site personnel. Randomisation was stratified by region (Japan vs rest of world), ECOG performance status (0 vs 1), and previous treatment with ramucirumab (yes vs no). Both patients and investigators were masked to treatment allocation. The primary endpoint was overall survival. Efficacy was assessed in the intention-to-treat population and safety in all patients who received at least one dose of treatment. This trial is registered with ClinicalTrials.gov, number NCT02500043. The trial, including follow-up of all participants, has been completed., Findings: Between Feb 24, 2016, and Jan 5, 2018, 507 patients were enrolled and randomly assigned, 337 to the trifluridine/tipiracil group and 170 to the placebo group. Median overall survival was 5·7 months (95% CI 4·8-6·2) in the trifluridine/tipiracil group and 3·6 months (3·1-4·1) in the placebo group (hazard ratio 0·69 [95% CI 0·56-0·85]; one-sided p=0·00029, two-sided p=0·00058). Grade 3 or worse adverse events of any cause occurred in 267 (80%) patients in the trifluridine/tipiracil group and 97 (58%) in the placebo group. The most frequent grade 3 or worse adverse events of any cause were neutropenia (n=114 [34%]) and anaemia (n=64 [19%]) in the trifluridine/tipiracil group and abdominal pain (n=15 [9%]) and general deterioration of physical health (n=15 [9%]) in the placebo group. Serious adverse events of any cause were reported in 143 (43%) patients in the trifluridine/tipiracil group and 70 (42%) in the placebo group. One treatment-related death was reported in each group (because of cardiopulmonary arrest in the trifluridine/tipiracil group and because of toxic hepatitis in the placebo group)., Interpretation: Trifluridine/tipiracil significantly improved overall survival compared with placebo and was well tolerated in this heavily pretreated population of patients with advanced gastric cancer. Trifluridine/tipiracil could be a new treatment option in this population who represent a high unmet medical need., Funding: Taiho Oncology and Taiho Pharmaceutical., (Copyright © 2018 Elsevier Ltd. All rights reserved.)