HER2 targeted therapy in colorectal Cancer: Current landscape and future directions

Colorectal cancer (CRC) is one of the most common causes of tumor-related deaths globally. Despite recent improvements in the comprehensive therapy of malignancy, metastatic CRC continues to have a poor prognosis. Human epidermal growth factor receptor 2 (HER2) is an established oncogenic driver, which is successfully targeted for breast and gastric cancers. Approximately 5% of CRC patients carry somatic HER2 mutations or gene amplification. In 2019, the U.S. Food and Drug Administration have approved trastuzumab and pertuzumab in combination with chemotherapy for the treatment of HER2-positive metastatic CRC. This approval marked a significant milestone in the treatment of CRC, as HER2-positive patients now have access to targeted therapies that can improve their outcomes. Yet, assessment for HER2 overexpression/ amplification in CRC has not been standardized. The resistance mechanisms to anti-HER2 therapy have been not clearly investigated in CRC. Although many unknowns remain, an improved understanding of these anti-HER2 agents will be essential for advanced CRC. In this review, we provide an overview of the role of HER2 in CRC as an oncogenic driver, a prognostic and predictive biomarker, and a clinically actionable target, as well as the current progress and challenges in the field.

Novel HER-2 Targeted Therapies in Breast Cancer

Human epidermal growth factor 2 (HER-2)-positive breast cancer represents 15-20% of all breast cancer subtypes and has an aggressive biological behavior with worse prognosis. The development of HER-2-targeted therapies has changed the disease's course, having a direct impact on survival rates and quality of life. Drug development of HER-2-targeting therapies is a prolific field, with numerous new therapeutic strategies showing survival benefits and gaining regulatory approval in recent years. Furthermore, the acknowledgement of the survival impact of HER-2-directed therapies on HER-2-low breast cancer has contributed even more to advances in the field. The present review aims to summarize the newly approved therapeutic strategies for HER-2-positive breast cancer and review the new and exploratory HER-2-targeted therapies currently under development.

Bispecific antibodies in cancer therapy: Target selection and regulatory requirements

In recent years, the development of bispecific antibodies (bsAbs) has been rapid, with many new structures and target combinations being created. The boom in bsAbs has led to the successive issuance of industry guidance for their development in the US and China. However, there is a high degree of similarity in target selection, which could affect the development of diversity in bsAbs. This review presents a classification of various bsAbs for cancer therapy based on structure and target selection and examines the advantages of bsAbs over monoclonal antibodies (mAbs). Through database research, we have identified the preferences of available bsAbs combinations, suggesting rational target selection options and warning of potential wastage of medical resources. We have also compared the US and Chinese guidelines for bsAbs in order to provide a reference for their development.

Emerging Targeted Therapies for HER2-Positive Breast Cancer

Breast cancer is the most common cancer in women and the leading cause of death. HER2 overexpression is found in approximately 20% of breast cancers and is associated with a poor prognosis and a shorter overall survival. Tratuzumab, a monoclonal antibody directed against the HER2 receptor, is the standard of care treatment. However, a third of the patients do not respond to therapy. Given the high rate of resistance, other HER2-targeted strategies have been developed, including monoclonal antibodies such as pertuzumab and margetuximab, trastuzumab-based antibody drug conjugates such as trastuzumab-emtansine (T-DM1) and trastuzumab-deruxtecan (T-DXd), and tyrosine kinase inhibitors like lapatinib and tucatinib, among others. Moreover, T-DXd has proven to be of use in the HER2-low subtype, which suggests that other HER2-targeted therapies could be successful in this recently defined new breast cancer subclassification. When patients progress to multiple strategies, there are several HER2-targeted therapies available; however, treatment options are limited, and the potential combination with other drugs, immune checkpoint inhibitors, CAR-T cells, CAR-NK, CAR-M, and vaccines is an interesting and appealing field that is still in development. In this review, we will discuss the highlights and pitfalls of the different HER2-targeted therapies and potential combinations to overcome metastatic disease and resistance to therapy.

Efficacy and safety of HER2-targeted therapy in patients with colorectal cancer: What should we expect from a meta-analysis?

BACKGROUND AND OBJECTIVE

Human epidermal growth factor receptor 2 (HER2) is an effective therapeutic target for breast and stomach cancers. However, the application of HER2-targeted therapy in colorectal cancer (CRC) remains controversial. We sought to assess the efficacy and safety of HER2-targeted therapy in CRC by performing a meta-analysis of relevant studies.

METHODS

We searched PubMed, Embase, Cochrane Library, Web of Science, and the ClinicalTrials.gov database to retrieve relevant studies. STATA 16 was used for the statistical analysis. The objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), and incidence of treatment‑related adverse events (TRAEs) were used as the outcome indicators analyzed by random- or fixed-effects models.

RESULTS

A total of 267 patients from nine studies were included in this meta-analysis. The overall ORR and DCR were 27.5% (95% CI 16.8% to 39.6%) and 68.9% (95% CI 55.4% to 81.0%), respectively. No significant heterogeneity was found in PFS among these studies and the overall median PFS was 4.35 months (95% CI 3.70 to 4.99). The overall incidence of all-grade and grade 3 or higher adverse events were 93.5% (95% CI 88.4% to 97.4%) and 16.8% (95% CI 4.8% to 33.3%).

CONCLUSIONS

HER2-targeted therapy was confirmed as a promising treatment for colorectal cancer, warranting further high-quality clinical randomized controlled trials to verify.

Role of Fcγ receptors in HER2-targeted breast cancer therapy

Several therapeutic monoclonal antibodies (mAbs), including those targeting epidermal growth factor receptor, human epidermal growth factor receptor 2 (HER2), and CD20, mediate fragment crystallizable gamma receptor (FcγR)–dependent activities as part of their mechanism of action. These activities include induction of antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP), which are innate immune mechanisms of cancer cell elimination. FcγRs are distinguished by their affinity for the Fc fragment, cell distribution, and type of immune response they induce. Activating FcγRIIIa (CD16A) on natural killer cells plays a crucial role in mediating ADCC, and activating FcγRIIa (CD32A) and FcγRIIIa on macrophages are important for mediating ADCP. Polymorphisms in FcγRIIIa and FcγRIIa generate variants that bind to the Fc portion of antibodies with different affinities. This results in differential FcγR-mediated activities associated with differential therapeutic outcomes across multiple clinical settings, from early stage to metastatic disease, in patients with HER2+ breast cancer treated with the anti-HER2 mAb trastuzumab. Trastuzumab has, nonetheless, revolutionized HER2+ breast cancer treatment, and several HER2-directed mAbs have been developed using Fc glyco-engineering or Fc protein-engineering to enhance FcγR-mediated functions. An example of an approved anti-HER2 Fc-engineered chimeric mAb is margetuximab, which targets the same epitope as trastuzumab, but features five amino acid substitutions in the IgG 1 Fc domain that were deliberately introduced to increase binding to activating FcγRIIIa and decrease binding to inhibitory FcγRIIb (CD32B). Margetuximab enhances Fc-dependent ADCC in vitro more potently than the combination of pertuzumab (another approved mAb directed against an alternate HER2 epitope) and trastuzumab. Margetuximab administration also enhances HER2-specific B cell and T cell–mediated responses ex vivo in samples from patients treated with prior lines of HER2 antibody-based therapies. Stemming from these observations, a worthwhile future goal in the treatment of HER2+ breast cancer is to promote combinatorial approaches that better eradicate HER2+ cancer cells via enhanced immunological mechanisms.

Evolution of Escherichia coli Expression System in Producing Antibody Recombinant Fragments

Antibodies and antibody-derived molecules are continuously developed as both therapeutic agents and key reagents for advanced diagnostic investigations. Their application in these fields has indeed greatly expanded the demand of these molecules and the need for their production in high yield and purity. While full-length antibodies require mammalian expression systems due to the occurrence of functionally and structurally important glycosylations, most antibody fragments and antibody-like molecules are non-glycosylated and can be more conveniently prepared in E. coli-based expression platforms. We propose here an updated survey of the most effective and appropriate methods of preparation of antibody fragments that exploit E. coli as an expression background and review the pros and cons of the different platforms available today. Around 250 references accompany and complete the review together with some lists of the most important new antibody-like molecules that are on the market or are being developed as new biotherapeutics or diagnostic agents.