Globally, the fifth most common cancer and the fourth leading cause of cancer-related mortality is gastric cancer (GC). Recent clinical trials on solid tumors enrolled patients who possess druggable genetic alterations, protein expression, and immune characteristics. In gastric or gastroesophageal junction (GEJ) cancers, trastuzumab combined with first-line chemotherapy in human epidermal growth factor receptor 2 (HER2)-positive patients and ramucirumab combined with second-line paclitaxel remarkably prolonged overall survival (OS) compared with chemotherapy alone, according to phase 3 trial results. Recently, immune checkpoint inhibitor (ICI) monotherapy was approved as third- or later-line treatment. Chemotherapy plus ICIs as first-line treatment exhibited improved survival compared with chemotherapy alone in HER2-negative patients according to Checkmate 649 trial results. Conversely, systemic chemotherapy prognosis remains poor. although some patients may achieve durable response to treatment and prolonged survival in advanced GC. Recently, a first-in-class, chimeric immunoglobulin G1 monoclonal antibody (zolbetuximab) that targets and binds to claudin 18 isoform 2 (CLDN18.2) has emerged as a new target therapy in GC treatment. Global phase Ⅲ trials revealed that the addition of zolbetuximab to first-line chemotherapy prolonged OS in CLDN18.2-positive and HER2-negative GC patients. This review summarizes recent clinical trials of CLDN18.2-targeted therapy.

The cyclin D‐CDK4/6‐INK4‐Rb pathway is frequently dysregulated in cancers. Ribociclib, an orally available, selective CDK4/6 inhibitor, showed preliminary clinical activity in a phase I study in the USA and Europe for patients with solid tumors and lymphomas. The present study aimed to determine the single‐agent maximum tolerated dose (MTD) and recommended dose for expansion (RDE) in Japanese patients with advanced solid tumors. Ribociclib safety, tolerability, pharmacokinetic profile, and preliminary antitumor activity were also assessed. Japanese patients with solid tumors that had progressed on prior therapies received escalating doses of single‐agent ribociclib on a 3‐weeks‐on/1‐week‐off schedule. Treatment continued until the development of toxicity or disease progression. A dose escalation was planned for patients with esophageal cancer. In the dose‐escalation phase, 4 patients received 400 mg ribociclib and 13 patients received 600 mg ribociclib. Four patients experienced dose‐limiting toxicities, 3 of whom were in the 600 mg group. The RDE was declared to be 600 mg, and the MTD was not determined. The most frequent adverse events were hematologic and gastrointestinal. Four patients achieved stable disease at the 600 mg dose; no patients achieved complete or partial response. All patients discontinued the study, the majority due to disease progression. No patients discontinued due to adverse events. Dose escalation was not pursued due to lack of observed efficacy in esophageal cancer. At the RDE of 600 mg/d on a 3‐weeks‐on/1‐week‐off schedule, ribociclib showed acceptable safety and tolerability profiles in Japanese patients with advanced solid tumors.

Patients with unresectable advanced or recurrent gastric cancer have a poor prognosis with overall survival times increasing by only a few months after anti-cancer drug therapy in the last four decades. The survival times from previous clinical trials for untreated metastatic gastric cancer in Japan are generally better than those reported from trials in European and North or South American countries. Therefore, the proportion of Japanese patients enrolled in recent global trials of novel anti-cancer drugs should be increased in order to identify drugs that specifically prolong the survival of such patients. S-1 plus oxaliplatin (SOX) therapy is the most commonly used standard first-line treatment for advanced gastric cancer in Japan. SOX induces mild nausea and vomiting, even in elderly patients, that can be treated by maintaining oral intake with adequate anti-emetic treatment usually given in an outpatient clinic. Neutropenia, nausea, and vomiting in SOX therapy were more frequently observed in female patients compared with males. Intensive toxic chemotherapy such as triplet therapy never prolonged overall survival or maintained a favorable quality of life. The current strategies used against metastatic gastric cancer need to be modified in regard to innovative treatments with current drugs, keeping in mind each categorized treatment population. In a real world of a diverse society even if the same treatment is performed, the outcome of the individual patient is different. It is important for each society to implement established treatment, knowing that the evidence from global trials aimed at drug approval does not necessarily show external validity.

Mechanisms accounting for sex differences in the incidence of adverse events caused by fluoropyrimidine treatments, and histologic differences in efficacy are insufficiently understood. We determined differences between the sexes in terms of the safety of S-1 plus oxaliplatin (SOX)/bevacizumab-versus-l-leucovorin, 5-fluorouracil (5-FU) and oxaliplatin (FOLFOX)/bevacizumab, and the impact of histology on their therapeutic effects, in 512 unresectable metastatic colorectal cancer patients from the SOFT phase III study. Nausea (OR: 2.88, P < 0.001) and vomiting (OR: 3.04, P = 0.005) occurred more frequently in females than males treated with SOX/bevacizumab, while nausea (OR: 2.12, P = 0.006), vomiting (OR: 3.26, P = 0.004), leukopenia (OR: 2.61, P < 0.001), neutropenia (OR: 2.92, P < 0.001), and alopecia (OR: 4.13, P < 0.001) were higher in females on FOLFOX/bevacizumab. Mean relative dose intensities (RDIs) of S-1 during all cycles of SOX/bevacizumab were significantly lower in females (73.9%) than males (81.5%) (P < 0.001), while RDIs of continuous infusion of 5-FU in the FOLFOX/bevacizumab regimen were 75.0% in females and 80.5% in males (P = 0.005). No significant differences in efficacy with regard to overall survival (OS) and progression-free survival (PFS) were identified between the sexes for either SOX/bevacizumab or FOLFOX/bevacizumab treatment. Patients with poorly-differentiated adenocarcinoma had significantly worse OS (HR: 2.72, 95% CI: 1.67-4.44, P < 0.0001) and PFS (HR: 1.89, 95% CI: 1.18-3.02, P = 0.0079) than patients with well- or moderately-differentiated adenocarcinoma. Female patients experienced more frequent and severe adverse reactions to SOX/bevacizumab and FOLFOX/bevacizumab and a worse prognosis for poorly-differentiated adenocarcinoma were confirmed in this phase III study. This warrants further translational research to identify the responsible mechanisms.

Background: To define the optimal chemotherapy regimen for each patient we therefore used tissue from patients to identify molecular prognostic or predictive biomarkers. Methods: Endoscopic biopsy specimens from primary lesions and surgical specimens on a phase III trial in patients with unresectable advanced or recurrent gastric cancer treated with docetaxel with cisplatin plus S-1 (DCS) or cisplatin plus S-1 (CS), were collected. We measured the mRNA expression of ERCC1 and analyzed SNPs in GSTP1 and ERCC1. Results: Low ERCC1 expression was associated with favorable prognosis for overall survival, OS by multivariable analysis (P = 0.001). There were significant interactions between the two treatment arms of DCS and CS, and ERCC1 mRNA expression. In patients with low ERCC1 expression of a favorable prognosis, DCS therapy was inferior to CS (P = 0.046). In addition to GSTP1 rs1695 (HR 1.728), ERCC1 rs3212980, ERCC1 rs2298881, ERCC1 rs3212964 with high expression of ERCC1 mRNA were associated with significantly worse prognosis with regard to OS. Conclusions: ERCC1 mRNA is an independent prognostic factor and predictive marker that can be used to guide the addition of docetaxel. The SNPs of ERCC1 and GSTP1 could be also prognostic or predictive factors.