Antibody-Drug Conjugates in Breast Cancer: Ascent to Destiny and Beyond-A 2023 Review

Efficacy of Anti-Cancer Immune Responses Elicited Using Tumor-Targeted IL-2 Cytokine and Its Derivatives in Combined Preclinical Therapies

Effective cancer therapies must address the tumor microenvironment (TME), a complex network of tumor cells and stromal components, including endothelial, immune, and mesenchymal cells. Durable outcomes require targeting both tumor cells and the TME while minimizing systemic toxicity. Interleukin-2 (IL-2)-based therapies have shown efficacy in cancers such as metastatic melanoma and renal cell carcinoma but are limited by severe side effects. Innovative IL-2-based immunotherapeutic approaches include immunotoxins, such as antibody-drug conjugates, immunocytokines, and antibody-cytokine fusion proteins that enhance tumor-specific delivery. These strategies activate cytotoxic CD8+ T lymphocytes and natural killer (NK) cells, eliciting a potent Th1-mediated anti-tumor response. Modified IL-2 variants with reduced Treg cell activity further improve specificity and reduce immunosuppression. Additionally, IL-2 conjugates with peptides or anti-angiogenic agents offer improved therapeutic profiles. Combining IL-2-based therapies with immune checkpoint inhibitors (ICIs), anti-angiogenic agents, or radiotherapy has demonstrated synergistic potential. Preclinical and clinical studies highlight reduced toxicity and enhanced anti-tumor efficacy, overcoming TME-driven immune suppression. These approaches mitigate the limitations of high-dose soluble IL-2 therapy, promoting immune activation and minimizing adverse effects. This review critically explores advances in IL-2-based therapies, focusing on immunotoxins, immunocytokines, and IL-2 derivatives. Emphasis is placed on their role in combination strategies, showcasing their potential to target the TME and improve clinical outcomes effectively. Also, the use of IL-2 immunocytokines in "in situ" vaccination to relieve the immunosuppression of the TME is discussed.

Antibody-Drug Conjugates in Breast Cancer: The Road Towards Biologically-Informed Selection and Sequencing

PURPOSE OF REVIEW

In this review, we discuss evidence supporting the use of antibody-drug conjugates (ADCs) in breast cancer treatment, describe novel ADCs and combination regimens under development, and examine our current understanding of resistance mechanisms and biomarkers to guide ADC selection and sequencing.

RECENT FINDINGS

Three ADCs have proven benefit in patients with metastatic breast cancer: trastuzumab emtansine (T-DM1), trastuzumab deruxtecan (T-DXd), and sacituzumab govitecan (SG). There are over two hundred investigational ADCs on the horizon, as pre-clinical studies work to identify novel ADC targets and structures. In this new frontier, translational efforts are underway to personalize the use of ADCs, including refining HER2 quantification and elucidating genetic, epigenetic, and post-translational mechanisms of resistance. ADCs have provided important treatment options for patients with breast cancer. As patients become eligible for more than one ADC, there is an unmet need to identify the appropriate timing and sequence of these therapies to maximize their efficacy.

Targeted Therapy in Breast Cancer: Advantages and Advancements of Antibody-Drug Conjugates, a Type of Chemo-Biologic Hybrid Drugs

Cancer is a significant health challenge globally, with millions of people affected every year, resulting in high morbidity and mortality. Although other treatment options are available with limitations, chemotherapy, either standalone or combined with other therapeutic procedures, is the most commonly used practice of treating cancer. In chemotherapy, cancer cells/malignant tumors are targeted; however, due to less target specificity, along with malignant cells, normal cells are also affected, which leads to various off-target effects (side effects) that impact the patient quality of life. Out of all the different types of cancers, breast cancer is the most common type of cancer in humans worldwide. Current anticancer drug discovery research aims to develop therapeutics with higher potency and lower toxicity, which is only possible through target-specific therapy. Antibody-drug conjugates (ADCs) are explicitly designed to target malignant tumors and minimize off-target effects by reducing systemic cytotoxicity. Several ADCs have been approved for clinical use and have shown moderate to good efficacy so far. Considering various aspects, chemotherapy and ADCs are useful in treating cancer. However, ADCs provide a more focused and less toxic approach, which is especially helpful in cases where resistance to chemotherapy (drug resistance) occurs and in the type of malignancies in which specific antigens are overexpressed. Ongoing ADC research aims to develop more target-specific cancer treatments. In short, this study presents a concise overview of ADCs specific to breast cancer treatment. This study provides insight into the classifications, mechanisms of action, structural aspects, and clinical trial phases (current status) of these chemo-biologic drugs (ADCs).

Comparative Analysis and Future Prospects of Human Epidermal Growth Factor Receptor 2 (HER2) and Trophoblast Cell-Surface Antigen 2 (Trop-2) Targeted Antibody-Drug Conjugates in Breast Cancer Treatment

Breast cancer remains the most prevalent malignancy among women globally, presenting significant challenges in therapeutic strategies due to tumor heterogeneity, drug resistance, and adverse side effects. Recent advances in targeted therapies, particularly antibody-drug conjugates (ADCs), have shown promise in addressing these challenges by selectively targeting tumor cells while sparing normal tissues. This study provides a comprehensive analysis of two innovative ADCs targeting HER2 and Trop-2, which are critical markers in various breast cancer subtypes. These conjugates combine potent cytotoxic drugs with specific antibodies, leveraging the antigens' differential expression to enhance therapeutic efficacy and reduce systemic toxicity. Our comparative analysis highlights the clinical applications, efficacy, and safety profiles of these ADCs, drawing on data from recent clinical trials. In addition, the paper discusses the potential of these ADCs in treating other types of cancers where HER2 and Trop-2 are expressed, as well as the toxicity risks associated with targeting these antigens in normal cells. Additionally, the paper discusses novel synthetic drugs that show potential in preclinical models, focusing on their mechanisms of action and therapeutic advantages over traditional chemotherapy. The findings underscore the transformative impact of targeted ADCs in breast cancer treatment, noting significant advancements in patient outcomes and management of side effects. However, ongoing issues such as resistance mechanisms and long-term safety remain challenges. The conclusion offers a forward-looking perspective on potential improvements and the future trajectory of ADC research. This study not only elucidates the current landscape of ADCs in breast cancer but also sets the stage for the next generation of oncological therapeutics. This study not only elucidates the current landscape of ADCs in breast cancer but also sets the stage for the next generation of oncological therapeutics, with particular attention to their broader applications and associated risks.

Characterization of HER2-Low Breast Tumors among a Cohort of Colombian Women

HER2-low tumors have shown promise in response to antibody-drug conjugates (ADCs) in recent clinical trials, underscoring the need to characterize this group's clinical phenotype. In this study, we aimed to explore the clinicopathological features, survival rates, and HER2 amplicon mRNA expression of women affected with HER2-low breast cancer, compared with HER2-negative and HER2-positive groups. We included 516 breast cancer patients from Colombia, for whom we compared clinicopathological features, mRNA expression of three HER2 amplicon genes (ERBB2, GRB7 and MIEN1), survival and risk of mortality between HER2-low cases (1+ or 2+ with negative in situ hybridization (ISH) result) with HER2-positive (3+ or 2+ with positive ISH test) and HER2-negative (0+) cases. A higher proportion of patients with better-differentiated tumors and a lower proliferation index were observed for HER2-low tumors compared to the HER2-positive group. Additionally, HER2-low tumors showed higher mRNA expression of the ERBB2 gene and longer overall survival rates compared to HER2-negative cases. Nonetheless, a Cox-adjusted model by ER status and clinical stage showed no statistically significant differences between these groups. Our results show differences in important clinicopathological features between HER2-low and both HER2-positive and negative tumors. Given this unique phenotype, it is crucial to evaluate the potential advantages of ADC therapies for this emerging subtype of breast cancer.

Antibody-drug conjugates for breast cancer: a bibliometric study and clinical trial analysis

BACKGROUND

Breast cancer (BC) remains the most commonly malignancy among women worldwide. Although early-stage BC typically presents with curative possibilities, advanced-stage disease, especially with metastasis, is significantly limited in terms of effective therapeutic interventions, thereby establishing it as the second leading cause of cancer-related deaths in women. Antibody-Drug Conjugates (ADCs) establish a groundbreaking class of anti-neoplastic agents characterized by high specificity and targeting precision. These agents have been significant in reshaping the therapeutic approach to breast cancer, especially those subtypes with overexpression of the Human Epidermal Growth Factor Receptor 2 (HER2). Comprising monoclonal antibodies, cytotoxic payloads, and conjugative linkers, ADCs function by specifically targeting antigens on cancer cells, thereby facilitating the intracellular delivery of the toxic payload. The present investigation endeavors to synthesize existing primary research outcomes through rigorous bibliometric and data analytical approaches, thereby elucidating the current research landscape, delineating research foci, and identifying potential avenues for future innovation.

METHODS

For bibliometric analysis, a comprehensive data set comprising 2181 entries related to ADCs in breast cancer was retrieved from the Web of Science Core Collection (WoSCC) spanning the years 1999 to 2023. This data was further filtered from the Science Citation Index Expanded (SCI-Expanded). Analysis software tools such as CiteSpace and VOSviewer were employed for multifaceted analyses such as trends of publications, contributions of countries, and burst analytics. In the dimension of clinical trials, we interrogated databases including ClinicalTrials.gov ( https://www.

CLINICALTRIALS

gov ) and the WHO International Clinical Trials Registry Platform (ICTRP) ( https://trialsearch.who.int ). A total of 239 clinical trials were initially sourced, among which, 175 were from ClinicalTrials.gov and 64 from ICTRP. After repetitive and correlation-based screening, 119 trials specifically addressing ADC therapeutic strategies in breast cancer were included. Analytical algorithms were executed using Microsoft-based software to evaluate treatment paradigms, emergent research themes, and progress.

RESULTS

Our investigations signify a growing trend of research on ADCs, with consistent advancements in scientific achievements. The analysis revealed that variables such as economic stratification of nations, healthcare investment paradigms, and disease incidence rates serve as significant determinants in shaping research output. Geographically, the United States emerged as the predominant contributor to the research corpus (36.56%), closely followed by China (21.33%). The underpinning of research accomplishments was found to be significantly bolstered by advancements in molecular biology, immunology, and genetic research. Moreover, the advent of nuclear magnetic resonance diagnostic modalities has contributed saliently to the diagnostic and therapeutic management of breast cancer.

CONCLUSION

Our study provides a comprehensive overview of the ADC research landscape through rigorous bibliometric and clinical trial evaluations. At present, the ADC arena has witnessed the successful development and FDA approval of 14 distinct agents, substantially improving the clinical outcomes for a broad spectrum of oncological patients. Future research imperatives may include the exploration of ADCs targeting mutated oncoproteins, dual-specificity ADCs, combination payload strategies, peptide-drug conjugates (PDCs), and non-internalizing ADC modalities. With sustained academic and clinical focus, the ADC domain is poised for transformative advancements in targeted therapeutics across a variety of malignancies.

Prognostic stratification ability of the CPS+EG scoring system in HER2-low and HER2-zero early breast cancer treated with neoadjuvant chemotherapy

BACKGROUND

The CPS+EG scoring system was initially described in unselected early breast cancer (eBC) patients treated with neoadjuvant chemotherapy (NAC), leading to refined prognostic stratification, and thus helping to select patients for additional post-NAC treatments. It remains unknown whether the performance is the same in new biological breast cancer entities such as the HER2-low subtype.

PATIENTS AND METHODS

Outcomes (disease-free (DFS) and overall survival OS)) of 608 patients with HER2-non amplified eBC and treated with NAC were retrospectively analyzed according to CPS-EG score. We compared the prognostic stratification abilities of the CPS+EG in HER2-low and HER2-0 eBC, analyzing ER+ and ER- tumors separately.

RESULTS

In ER+ eBC, the CPS+EG scoring system seems to retain a prognostic value, both in HER2-low and HER2-0 tumors, by distinguishing populations with significantly different outcomes (good: score 0-1, poor: score 2-3, and very poor: score 4-5). Using C-indices for DFS and OS, CPS+EG provided the highest prognostic information in ER+ eBC, especially in HER2-0 tumors. In contrast, in ER- eBC, the CPS+EG does not appear to be able to distinguish different outcome groups, either in HER2-low or HER2-0 tumors. In ER- eBC, C-indices for DFS and OS were highest for pathological stage, reflecting the predominant prognostic importance of residual disease in this subtype.

CONCLUSIONS

HER2-low status does not influence the prognostic performance of the CPS+EG score. Our results confirm the usefulness of the CPS+EG score in stratifying the prognosis of ER+ eBC after NAC, for both HER2-0 and HER2-low tumors. For ER- eBC, HER2-low status does not influence the performance of the CPS+EG score, which was lower than that of the pathological stage alone.

Engineered polyspecific antibodies: A new frontier in the field of immunotherapeutics

The 21st-century beginning remarked with the huge success of monospecific MAbs, however, in the last couple of years, polyspecific MAbs (PsAbs) have been an interesting topic and show promise of being biobetter than monospecific MAbs. Polyspecificity, in which a single antibody serves multiple specific target binding, has been hypothesized to contribute to the development of a highly effective antibody repertoire for immune defence. This polyspecific MAb trend represents an explosion that is gripping the whole pharmaceutical industry. This review is concerned with the current development and quality enforcement of PsAbs. All provided literature on monospecific MAbs and polyspecific MAbs (PsAbs) were searched using various electronic databases such as PubMed, Google Scholar, Web of Science, Elsevier, Springer, ACS, Google Patent and books via the keywords Antibody engineering, Polyspecific antibody, Conventional antibody, non-conventional antibody, and Single domain antibody. In the literature, there are more than 100 different formats to construct PsAb by quadroma technology, chemical conjugation and genetic engineering. Till March 2023, nine PsAb have been approved around the world, and around 330 are in advanced developmental stages, showing the dominancy of PsAb in the growing health sector. Recent advancements in protein engineering techniques and the fusion of non-conventional antibodies have made it possible to create complex PsAbs that demonstrate higher stability and enhanced potency. This marks the most significant achievement for cancer immunotherapy, in which PsAbs have immense promise. It is worth mentioning that seven out of the nine PsAbs have been approved as anti-cancer therapy. As PsAbs continue to acquire prominence, they could pave the way for the development of novel immunotherapies for multiple diseases.

A network meta-analysis of efficacy and safety for first-line and second/further-line therapies in postmenopausal women with hormone receptor-positive, HER2-negative, advanced breast cancer

BACKGROUND

Hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR + /HER2 -) advanced breast cancer is a prevalent subtype among postmenopausal women. Despite the growing number of randomized clinical trials (RCTs) exploring this topic, the efficacy and safety of first-line and second/further-line treatments remain uncertain. Accordingly, our aim was to conduct a comprehensive evaluation of the efficacy and safety of these therapies through network meta-analysis.

METHODS

RCTs were identified by searching Pubmed, Embase, and major cancer conferences. The efficacy of interventions was assessed using the hazard ratios (HRs) of progression-free survival (PFS) and overall survival (OS), while safety was indicated by the incidence of any grade adverse events (AEs), grade 3-5 AEs, AEs leading to treatment discontinuation, and AEs leading to death. Both time-variant HRs fractional polynomial models and time-invariant HRs Cox-proportional hazards models were considered for handling time-to-event data. Safety indicators were analyzed using Bayesian network meta-analysis. Additionally, subgroup analyses were conducted based on patient characteristics.

RESULTS

A total of 41 RCTs (first-line 17, second/further-lines 27) were included in the analysis. For first-line treatment, the addition of Cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors to endocrine therapy significantly improved therapeutic efficacy in terms of both PFS and OS, demonstrating the best performance across all mechanisms. Specifically, the combination of Abemaciclib and Letrozole demonstrated the most favorable performance in terms of PFS, while Ribociclib plus Fulvestrant yielded the best outcomes in OS. Incorporating the immune checkpoint inhibitor Avelumab into the regimen with CDK4/6 inhibitors and selective estrogen receptor degraders significantly enhanced both PFS and OS in second-line or later treatments. Regarding safety, endocrine monotherapy performed well. Regarding safety, endocrine monotherapy performed well. There is mounting evidence suggesting that most CDK4/6 inhibitors may demonstrate poorer performance with respect to hematologic AEs. However, additional evidence is required to further substantiate these findings.

CONCLUSIONS

CDK4/6 inhibitors, combined with endocrine therapy, are pivotal in first-line treatment due to their superior efficacy and manageable AEs. For second/further-line treatment, adding immune checkpoint inhibitors to CDK4/6 inhibitors plus endocrine therapy may produce promising results. However, to reduce the results' uncertainty, further trials comparing these novel treatments are warranted.

TRIAL REGISTRATION

Registration number: PROSPERO (CRD42022377431).

HER2+ Early Breast Cancer: From Escalation via Targeted and Post-Neoadjuvant Treatment to De-Escalation

Background

Human epidermal growth factor receptor 2 positive (HER2+, also referred to as ERBB2+) breast cancer is a subtype, historically associated with a particularly poor prognosis. Research into biological and molecular pathomechanisms of breast cancer has resulted in the development and adoption of several therapies targeting HER2. In parallel, various escalation/de-escalation strategies have been examined to further optimize patient outcomes and care.

Summary

In this review, we highlighted the landmark trials in the evolution of treatment and management of HER2+ early breast cancer (eBC).

Key Messages

Continuous research over the last two decades has gradually prolonged survival in patients with early HER2+ eBC. Incorporation of post-neoadjuvant setting into clinical practice improved long-term outcomes in high-risk patients with residual disease after neoadjuvant therapy. In parallel, use of modern anti-HER2 agents may potentially allow omission of chemotherapy without compromising the survival in a significant number of selected patients. Current research focused on exploring the molecular heterogeneity of HER2+ breast cancer resulted in identification of new prognostic and predictive biomarkers which could pave the way toward the development of truly personalized therapy.

The Fundamental Role of Oxime and Oxime Ether Moieties in Improving the Physicochemical and Anticancer Properties of Structurally Diverse Scaffolds

The present review explores the critical role of oxime and oxime ether moieties in enhancing the physicochemical and anticancer properties of structurally diverse molecular frameworks. Specific examples are carefully selected to illustrate the distinct contributions of these functional groups to general strategies for molecular design, modulation of biological activities, computational modeling, and structure-activity relationship studies. An extensive literature search was conducted across three databases, including PubMed, Google Scholar, and Scifinder, enabling us to create one of the most comprehensive overviews of how oximes and oxime ethers impact antitumor activities within a wide range of structural frameworks. This search focused on various combinations of keywords or their synonyms, related to the anticancer activity of oximes and oxime ethers, structure-activity relationships, mechanism of action, as well as molecular dynamics and docking studies. Each article was evaluated based on its scientific merit and the depth of the study, resulting in 268 cited references and more than 336 illustrative chemical structures carefully selected to support this analysis. As many previous reviews focus on one subclass of this extensive family of compounds, this report represents one of the rare and fully comprehensive assessments of the anticancer potential of this group of molecules across diverse molecular scaffolds.