HER2 Inhibition in Gastric Cancer-Novel Therapeutic Approaches for an Established Target

Gastric cancer is a leading cause of cancer-related deaths globally. Human epidermal growth receptor 2 (HER2) overexpression of HER2 gene amplification is present in 20% of gastric cancers and defines a subset amenable to HER2-directed therapeutics. The seminal ToGA study led to routine use of the monoclonal antibody trastuzumab in conjunction to platinum-fluoropyridimine first-line chemotherapy for HER2-positive gastric cancers as standard-of-care. Although limited progress was made in the decade following ToGA, there is now an abundance of novel therapeutic approaches undergoing investigation in parallel. Additionally, new data from randomised trials have indicated efficacy of the antibody-drug conjugate trastuzumab deruxtecan in chemorefractory patients and increased responses with the addition of first-line immune checkpoint blockade to trastuzumab and chemotherapy. This review will outline the data supporting HER2 targeting in gastric cancers, discuss mechanisms of response and resistance to HER2-directed therapies and summarise the emerging therapies under clinical evaluation that may evolve the way we manage this subset of gastric cancers in the future.

Retrospective Study on the Efficacy and Safety of Pyrotinib-Based Therapy for HER2-Positive Nonbreast Advanced Solid Tumors

Background

Human epidermal growth factor receptor 2 (HER2) is a member of the large ErbB family and an important oncogene in many solid tumors. Pyrotinib has been approved for the treatment of HER2-positive, recurrent, or metastatic breast cancer. However, there are very few clinical studies on pyrotinib in other HER2-positive solid tumors. Therefore, more evidence of clinical research is impendently needed to shepherd pyrotinib-based therapy in HER2-positive nonbreast advanced solid tumors. Patients and Methods. We performed a retrospective analysis of HER2-positive nonbreast advanced solid tumors patients with HER2 amplification or mutations who were administered with pyrotinib-based therapy in Henan Cancer Hospital between July 1, 2019, and December 2, 2021. In our research, 25 eligible patients were included with 16 patients with lung cancer, 6 patients with gastric cancer, 2 patients with colorectal cancer, and 1 patient with cholangiocarcinoma. Progression-free survival (PFS) is our main research end point.

Results

The median PFS was 188 days (95% CI: 83–not reached (NR)), and overall survival (OS) was 250 days (95% CI: 188–NR), respectively. 16 patients with lung cancer had a median PFS of 204 days (95% CI: 55–NR) and 6 patients with gastric cancer had PFS of 142 days (95% CI: 83–NR), respectively. The median OS was 366 days (95% CI: 248–NR) in patients with lung cancer and 179 days (95% CI: 90–NR) in patients with gastric cancer. The median PFS and OS of patients receiving >3 line treatment were lower than those receiving ≤3 line treatment (PFS: 188 days vs 204 days, p = 0.92; OS: 188 days vs 366 days, p = 0.43). All 25 patients can be evaluated. The objective response rate (ORR) was 24%, and the disease control rate (DCR) was 68%. Lung cancer ORR was 25%, and gastric cancer ORR was 16.7%. In addition, the DCR of lung cancer was 62.5% and that of gastric cancer was 66.7%. In addition, the ORR and DCR of patients receiving treatment ≤3 lines were higher than those receiving treatment >3 lines (ORR: 35.7% vs 9.1%, p = 0.18; DCR: 71.4% vs 63.6%, p > 0.99). The most common treatment-related adverse events (TRAEs) were diarrhea (84%), but only 3 patients (12%) reported grade 3 diarrhea with good control.

Conclusion

These results show that in HER2-positive nonbreast advanced solid tumors, the treatment based on pyrotinib regimen has good antitumor activity and acceptable safety. This retrospective study aims to promote larger clinical studies to further clarify the efficacy and safety of pyrotinib in the treatment of nonbreast solid tumors.

Emerging HER2-directed therapeutic agents for gastric cancer in early phase clinical trials

INTRODUCTION

HER2 positive gastric cancer is a distinct subgroup overexpressing the HER2 receptor. For a decade, first-line Trastuzumab was the only licensed HER2-directed therapy for HER2 positive advanced gastric cancer following results from the ToGA trial in 2010 demonstrating a survival benefit when added to chemotherapy. Within the last year, significant advances have taken place in the field of HER2-directed gastric cancer therapy.

AREAS COVERED

This review discusses pivotal clinical trial results and summarises current clinical trials of HER2-directed therapy in gastric cancer. Evidence for HER2-directed antibodies, immunotherapy, immune stimulating antibody conjugates, antibody-drug conjugates (including DESTINY trial results) and tyrosine kinase inhibitors are placed into clinical context. Key challenges including resistance mechanisms and drug toxicities are outlined. Search terms 'HER2' and 'gastric cancer' were entered into ClinicalTrials.gov, Pubmed and Google. Only English-language studies were included.

EXPERT OPINION

Clinical management of HER2 positive gastric cancer patients is likely to change significantly over the next 5 years. Checkpoint inhibition is likely to be used alongside HER2-directed therapy and chemotherapy first-line in advanced disease. Trastuzumab deruxtecan is likely to be offered second-line and beyond. The sheer number of clinical trials of HER2-directed therapy in gastric cancer are testament to progress and potential.

A Metastatic Cervical Adenocarcinoma Patient Carrying HER2 G292R Achieved Complete Response Upon Pyrotinib Treatment

Cervical cancer patients who develop distant metastasis are rarely curable with very limited treatment options. Chemotherapy is often administered but with limited efficacy. Immunotherapy and anti-angiogenesis therapy are recommended for selected cases of recurrent or metastatic cervical cancers. The clinical efficacy of inhibitors targeting HER2, a commonly mutated gene in cervical cancer, has not been elucidated. Herein, we report a metastatic cervical adenocarcinoma patient carrying HER2 G292R who benefited from pyrotinib after progression on radio-chemotherapy, achieving complete response (CR) with a progression-free survival of 25 months and counting. Our study sheds light on the treatment options for previously treated metastatic cervical adenocarcinoma patients harboring activating HER2 mutations.

Efficacy of Pyrotinib in a Heavily Pretreated Patient with Lung Adenocarcinoma Harboring HER2 Amplification and Exon 20 Insertions: A Case Report

The clinical benefits of HER2 inhibitors in patients with non-small cell lung cancer (NSCLC) have been limited. There is a paucity of effective therapies in NSCLC after developing resistance to initial anti-HER2 therapy. Herein, we presented the clinical benefit of pyrotinib in a 53-year-old patient with advanced lung adenocarcinoma whose circulating tumor DNA (ctDNA) analysis of pleural effusion revealed the coexistence of HER2 exon 20 p.Y772_A775dup (mutation ratio: 38.86%) and HER2 amplification (copy number: 4.5) following failures of multiple therapies including afatinib and ado-trastuzumab emtansine (T-DM1). Notably, pyrotinib treatment induced rapid and marked improvement of clinical symptoms, and partial response was observed after 8 weeks. CtDNA monitoring during the treatment showed that the mutation ratio of HER2 decreased to 7.99%, and the amplification disappeared. The patient achieved a progression-free survival of 7.5 months after treatment with pyrotinib. Thus, pyrotinib may be a new treatment strategy for the subgroup of lung adenocarcinoma patients, with coexistence of HER2 exon 20 p.Y772_A775dup and HER2 amplification even after failures of multiple anti-HER2 therapies. It also indicated the value of capture-based next-generation sequencing to monitor and guide therapy.