Targeting HER3 for cancer treatment: a new horizon for an old target.

Human epidermal growth factor receptor 3 (HER3) is a member of the human epidermal growth factor receptors family, having as its main ligands neuregulins 1 and 2. Although its poor tyrosine kinase activity entails a weak oncogenic power on its own, HER3 can heterodimerize with HER2 and/or epidermal growth factor receptor (EGFR), leading to a drastic enhancement of transphosphorylation and activation of downstream signaling pathways, ultimately promoting oncogenesis, metastatic dissemination, and drug resistance. Given its ubiquitous expression across solid tumors, multiple efforts have been done to therapeutically target HER3 by blocking either the ligand binding domain or its dimerization with other receptors. Treatment with anti-HER3 monoclonal antibodies or bispecific antibodies, both as single agents and in combination with other compounds, unfortunately led to unsatisfactory results across several tumor types. The HER3-directed delivery of cytotoxic payloads through antibody-drug conjugates has recently demonstrated encouraging activity in several tumor types, however, suggesting a potential role for the therapeutic targeting of HER3 in cancer treatment.

Clinical development and current role of margetuximab for the treatment of breast cancer.

Up to 20% of breast cancers overexpress HER2, a molecular alteration conferring these tumors a particularly aggressive behavior. However, targeting HER2 has radically changed the prognosis of this disease in the last 2 decades, with multiple anti-HER2 compounds shown to improve disease outcomes both in the early and advanced setting. The latest anti-HER2 compound to be approved by the U.S. Food and Drug Administration (FDA) was margetuximab, an Fc-engineered monoclonal antibody with an improved binding to FcγRIIIA receptor, which leads to a greater antibody-dependent cellular cytotoxicity (ADCC) activation compared with trastuzumab. Margetuximab was shown to slightly improve progression-free survival compared with trastuzumab when combined with chemotherapy for the treatment of advanced HER2-positive breast cancer patients, and is now included among the available treatment options for pretreated HER2-positive breast cancer patients. In this monograph we recapitulate the clinical development, current role and future perspectives of margetuximab for the treatment of breast cancer.

Benefit of adjuvant chemotherapy in patients with special histology subtypes of triple-negative breast cancer: a systematic review.

PURPOSE: Breast cancer (BC) is a leading cause of morbidity, disability, and mortality in women, worldwide; triple-negative BC (TNBC) is a subtype traditionally associated with poorer prognosis. TNBC special histology subtypes present distinct clinical and molecular features and sensitivity to antineoplastic treatments. However, no consensus has been defined on the best adjuvant therapy. The aim of the review is to study the evidence from literature to inform the choice of adjuvant treatments in this setting. METHODS: We systematically searched literature assessing the benefit of adjuvant chemotherapy in patients with TNBC special histotypes (PROSPERO: CRD42020153818). RESULTS: We screened 6404 records (15 included). All the studies estimated the benefit of different chemotherapy regimens, in retrospective cohorts (median size: 69 patients (range min-max: 17-5142); median follow-up: 51 months (range: 21-268); mostly in Europe and USA). In patients with early-stage adenoid cystic TNBC, a marginal role of chemotherapy was reported. Similar for apocrine TNBC. Medullary tumors exhibited an intrinsic good prognosis with a limited role of chemotherapy, suggested to be modulated by the presence of tumor-infiltrating lymphocytes. A significant impact of chemotherapy on the overall survival was estimated in patients with metaplastic TNBC. Limitations were related to the retrospective design of all the studies and heterogeneous treatments received by the patients. CONCLUSIONS: There is potential opportunity to consider treatment de-escalation and less intense therapies in some patients with early, special histology-type TNBC. International efforts are indispensable to validate prospective clinical decision models.