Southwest Oncology Group study S0413: a phase II trial of lapatinib (GW572016) as first-line therapy in patients with advanced or metastatic gastric cancer

Phase I and II clinical trials for gastric cancer

Gastric cancer remains a global public health problem with considerable heterogeneity in pathogenesis and clinical presentation across geographic regions. Improved understanding of the molecular biology of this disease has opened avenues for targeted intervention. An individualized treatment approach is required for optimal management of this cancer. Overcoming resistance to therapy requires combining targeted agents with the traditional options of chemotherapy/radiation therapy, and also targeting more than 1 pathway of carcinogenesis at a time. Encouraging molecular hypothesis and biomarker-driven trials will lead to improved patient outcomes and may eventually enable the therapeutic nihilism associated with gastric cancer to be overcome.

Targeted therapy in the management of advanced gastric cancer: are we making progress in the era of personalized medicine?

BACKGROUND

Gastric cancer is one of the leading causes of cancer death. With greater understanding of the molecular basis of carcinogenesis, targeted agents have led to a modest improvement in the outcome of advanced gastric cancer (AGC) patients.

METHODS AND RESULTS

We conducted an overview of the published evidence regarding the use of targeted therapy in AGC patients. Thus far, the human epidermal growth factor receptor (HER) pathway, angiogenic pathway, and phosphatidylinositol-3-kinase (PI3K)-Akt-mammalian target of rapamycin pathway have emerged as potential avenues for targeted therapy in AGC patients. The promising efficacy results of the Trastuzumab for Gastric Cancer trial led to the approved use of trastuzumab-based therapy as first-line treatment for patients with HER-2+ AGC. On the other hand, the Avastin® in Gastric Cancer trial evaluating bevacizumab in combination with chemotherapy did not meet its primary endpoint of a longer overall survival duration despite a significantly higher response rate and longer progression-free survival time in patients in the bevacizumab arm. Phase III data are awaited for other targeted agents, including cetuximab, panitumumab, lapatinib, and everolimus.

CONCLUSION

Recent progress in targeted therapy development for AGC has been modest. Further improvement in the outcome of AGC patients will depend on the identification of biomarkers in different patient populations to facilitate the understanding of gastric carcinogenesis, combining different targeted agents with chemotherapy, and unraveling new molecular targets for therapeutic intervention.

Targeted therapies for gastric cancer: current status

Gastric cancer represents one of the most common cancers internationally. Unfortunately the majority of patients still present at an advanced stage, and despite advances in diagnostic and treatment strategies, outcomes still remain poor with high mortality rates despite a decline in incidence. Whilst the utility of classical chemotherapy agents has been explored thoroughly (and continues to be investigated, alone or in various combinations), advances have been slow and the efficacy of these agents has reached a plateau. As such, the focus of recent study has shifted toward developing a greater understanding of the molecular biology of carcinogenesis and the cancer cell phenotype, and, in turn, the development of rationally designed drugs that target molecular aberrancies in signal transduction pathways specific to gastric cancer. These targets include circulating growth and angiogenic factors, cell surface receptors, and other molecules that comprise downstream intracellular signalling pathways, including receptor tyrosine kinases. Therapeutic advances in this area significantly lag behind other solid organ malignancies such as breast and colorectal cancer. This article reviews the role of targeted therapies in gastric cancer, including rationale and mechanism of action, current and emerging data, as single-agent therapy or in combination regimens. A recently published randomized phaseIII trial supporting the use of trastuzumab, an anti-human epidermal growth factor receptor 2 (HER2)/neu monoclonal antibody, in a selected population of patients is discussed. Therapies that have been evaluated in phase II trials are also reviewed, as well as promising new therapies currently being investigated in preclinical or phase I studies. There is optimism that targeted therapies, whether as single-agent therapy or in combination with traditional therapies, including chemotherapy, radiotherapy and surgery, may yet have an impact on improvement of the overall prognosis of gastric cancer.

Predicting the response to chemotherapy in gastric adenocarcinoma: who benefits from neoadjuvant chemotherapy?

Despite a decline in the overall incidence, gastric adenocarcinoma remains the second most common cause of cancer death worldwide and thus a significant global health problem. Even in early-stage locoregional confined disease the 5-year survival rarely exceeds 25-35 %. Randomized trials have demonstrated a benefit from neoadjuvant and perioperative chemotherapy. However the optimal approach in individual patients is not clear and remains controversial. A consistent finding is that patients who have a histopathological response to neoadjuvant therapy are more likely to receive a survival benefit. These clinical data provide a strong argument for the urgent development of methods to predict histopathological response to neoadjuvant therapies for gastric adenocarcinomas. Published data demonstrate that clinico-pathological features (tumour histology and location), imaging through metabolic response by FDG-PET and tissue/molecular biomarkers may all have a predictive value for neoadjuvant therapies. However it is still uncertain from published data whether or not they will be useful for clinical decision making in individual patients. Existing candidate biomarkers need to be properly qualified and validated and novel biomarkers are required and an optimal approach should involve the combination and integration of clinical, imaging, pathological and molecular biomarkers.

Antitumor effect of cetuximab in combination with S-1 in EGFR-amplified gastric cancer cells

Overexpression of human epidermal growth factor receptor (EGFR) has been detected in gastric cancer (GC) and is associated with poor outcomes. Combination treatment regimens with EGFR-targeting agents and cytotoxic agents are considered to be a potential therapeutic option for EGFR-overexpressing GC. Herein, we have investigated the effects of combination treatment with the oral fluoropyrimidine S-1 and the EGFR-targeting agent cetuximab in GC cells with or without EGFR overexpression. EGFR expression was determined by FACS and quantitative PCR in GC cells. Experimental 5-fluorouracil (5FU) was used instead of S-1 for in vitro experiments. The efficacy of 5FU or cetuximab monotherapy or combination 5FU/cetuximab therapy was examined in vitro and in vivo. Clinical specimens were examined for EGFR by immunohistochemistry (IHC). EGFR expression score was defined as strong membrane and cytoplasmic staining in at least 50–75% of cells. The combination of 5FU and cetuximab synergistically inhibited cell proliferation and exhibited an enhanced proapoptotic effect in GC cells with EGFR overexpression. Cetuximab also induced down-regulation of phosphorylation of EGFR and AKT, leading to diminished signaling. The antitumor effect of the combination of S-1 and cetuximab in vivo was also greater than that of either drug alone. Our preclinical findings thus indicate that the combination of S-1 and EGFR-targeting therapy is a promising treatment option for GC with EGFR overexpression.

Molecular targeted agents for gastric and gastroesophageal junction cancer

Despite recent improvements in surgical techniques and chemotherapy, advanced cancers of the stomach and gastroesophageal junction (GEJ) continue to have poor clinical outcomes. However, molecules intimately related to cancer cell proliferation, invasion, and metastasis have been studied as candidates for molecular targeted agents. Target molecules, such as the epidermal growth factor receptor, vascular endothelial growth factor receptor, and P13k/Akt/mTor pathway, as well as the insulin-like growth factor receptor, c-Met pathways, fibroblast growth factor receptor, and other pathways are considered to be promising candidates for molecular targeted therapy for gastric and GEJ cancer. In this review we focus on the recent developments in targeting relevant pathways in these types of cancer.

Design and synthesis of novel human epidermal growth factor receptor 2 (HER2)/epidermal growth factor receptor (EGFR) dual inhibitors bearing a pyrrolo[3,2-d]pyrimidine scaffold

Dual inhibitors of human epidermal growth factor receptor 2 (HER2) and epidermal growth factor receptor (EGFR) have been investigated for breast, lung, gastric, prostate, and other cancers; one, lapatinib, is currently approved for breast cancer. To develop novel HER2/EGFR dual kinase inhibitors, we designed and synthesized pyrrolo[3,2-d]pyrimidine derivatives capable of fitting into the receptors' ATP binding site. Among the prepared compounds, 34e showed potent HER2 and EGFR (HER1) inhibitory activities as well as tumor growth inhibitory activity. The X-ray cocrystal structures of 34e with both HER2 and EGFR demonstrated that 34e interacts with the expected residues in their respective ATP pockets. Furthermore, reflecting its good oral bioavailability, 34e exhibited potent in vivo efficacy in HER2-overexpressing tumor xenograft models. On the basis of these findings, we report 34e (TAK-285) as a promising candidate for clinical development as a novel HER2/EGFR dual kinase inhibitor.

Targeted therapies for metastatic esophagogastric cancer

The prognosis and long-term survival for patients with metastatic esophagogastric cancer (EGC) is poor. Historically, the mainstay of treatment has been combination chemotherapy. More recently, a number of targeted therapies have been developed and are being studied with the goal of improving response rate and survival in patients with metastatic EGC. To date, the only targeted therapy which has been clinically approved is trastuzumab which targets the HER2/Neu oncogene. However, only a small group of patients with EGCs are HER2 amplified, and there are other important targets/pathways which play a role in the development of these cancers that are currently being studied. With the identification of these other clinically relevant pathways, it is anticipated that several other therapies will be approved in the future.

Chemotherapy for metastatic gastric cancer: past, present, and future

Despite the numerous efforts of randomized studies on advanced gastric cancer, no globally accepted standard regimen has yet been established. Two triplet regimens have already demonstrated significant survival prolongation in Western studies. However, the benefit seems to be marginal, and these regimens may be replaced by recently published newer generation regimens for which favorable survival is reported. At present, the combination of 5-fluorouracil (5-FU) and platinum analog is still the most widely accepted standard regimen worldwide: 5-FU can be replaced by S-1 or capecitabine, and cisplatin by oxaliplatin. In Japan, S-1 plus cisplatin is the most reasonable first-line standard, based on recent randomized studies. Some early clinical studies using molecular targeting agents have shown promising activity, particularly in combination with cytotoxic agents for gastric cancer. Several targeting agents such as trastuzumab, bevacizumab, and lapatinib are now under investigation in international randomized studies, including in Japan. These agents have shown a survival benefit in other tumor types. The next-generation targeting agents, including mammalian target of rapamycin inhibitor and a c-Met tyrosine kinase inhibitor, are also being evaluated in early clinical studies in association with biology research. Such agents can be advantageously used in gastric cancer studies, which, because of the ease with which tumor tissues can be obtained by endoscopy and the high incidence of gastric cancer in Japan, might advance the frontiers of biologic therapy. These efforts should result not only in further clinical advances but also in tailored medicine.