TROPION-Breast01: Datopotamab deruxtecan vs chemotherapy in pre-treated inoperable or metastatic HR+/HER2- breast cancer

TOP1 Mutations and Cross-Resistance to Antibody-Drug Conjugates in Patients with Metastatic Breast Cancer

PURPOSE

Antibody-drug conjugates (ADC) harboring topoisomerase I (TOP1) inhibitor payloads have improved survival for patients with metastatic breast cancer. However, knowledge of ADC resistance mechanisms and potential impact on the sequential use of ADCs is limited. In this study, we report the incidence and characterization of TOP1 mutations arising in the setting of ADC resistance in metastatic breast cancer.

EXPERIMENTAL DESIGN

Patients with metastatic breast cancer treated with ADCs with available posttreatment plasma-based genotyping were included. TOP1 mutation incidence, mutant allele frequency, and functional characterization were assessed, and incidence was compared with that in patients with metastatic breast cancer not receiving ADC treatment and in The Cancer Genome Atlas.

RESULTS

Plasma-based genotyping identified distinct TOP1 mutations (S57C, R364H, W401C, and G359E) in 12.9% of patients (4/31) at the time of disease progression on ADC, compared with 0.7% (3/420) in non-ADC-treated patients with metastatic breast cancer and 0.5% in The Cancer Genome Atlas. The appearance of mutations was associated with clinical cross-resistance, as median duration on the first ADC was 455 versus 52 days for the second ADC. The functional characterization of three novel TOP1-mutant proteins demonstrated that all exhibited reduced enzymatic activity, attenuated covalent DNA binding, and resistance to TOP1 inhibitor ADC payloads SN38 and deruxtecan.

CONCLUSIONS

We describe the recurrent emergence of functionally altered, resistance-associated TOP1 mutations in vivo under selective pressure from ADCs and the potential impact on mediating cross-resistance to sequential ADCs. TOP1 mutation may represent a biomarker of resistance in this setting, and additional work is needed to optimize biomarkers and ADC payload design to improve outcomes for the sequential use of ADCs. See related commentary by Gwin and Hurvitz, p. 1824.

Epitope Expression Persists in Circulating Tumor Cells as Breast Cancers Acquire Resistance to Antibody Drug Conjugates

Antibody-drug conjugates (ADCs) targeting cell surface proteins TROP2 or HER2 are effective in metastatic breast cancer, but the precise clinical contribution of epitope expression is uncertain. We prospectively monitored circulating tumor cells (CTCs) in 33 patients receiving ADC therapies using quantitative imaging. The expression of TROP2 and HER2 are heterogeneous across single CTCs from untreated patients, comparable to matched tumor biopsies, and display poor association with clinical response. Within three weeks of treatment initiation, declining CTC numbers correlate with a durable response (TROP2: median time to progression 391 versus 97 days, HR 4.15, P=0.0046; HER2: 322 versus 66 days, HR 9.12, P=0.0002). Neither TROP2 nor HER2 expression is reduced at progression, compared to matched pretreatment CTCs, and switching ADC epitope while maintaining a similar payload shows poor efficacy. Thus, epitope downregulation is not a common driver of acquired resistance to TROP2 or HER2 ADCs, and second-line ADC therapies may benefit from distinct payloads.

SIGNIFICANCE

ADCs target tumor-associated antigens, followed by internalization and release of drug payloads. However, clinical studies of epithelial-targeting ADCs show efficacy despite low tumor epitope expression. Our finding that epitope downregulation does not commonly accompany acquired resistance suggests alternative drivers of clinical efficacy and the need for testing non-cross-resistant payloads to overcome resistance.

Efficiency of Fulvestrant Monotherapy After CDK4/6 Inhibitor Exposure: Is This a Viable Choice?

Guidelines for the first-line treatment of Hormone Receptor-positive, HER2-negative advanced or recurrent breast cancer have shifted to combination therapies of a CDK4/6 inhibitor and endocrine therapy. However, determining an optimal subsequent therapy following CDK4/6 inhibitor progression remains challenging, especially for tumors lacking actionable mutations. Real-world data suggest that fulvestrant monotherapy is frequently selected in this post-CDK4/6 inhibitor setting. This review examines its therapeutic potential in this evolving landscape. A systematic literature search using PubMed and ClinicalTrials.gov identified 153 clinical trials published between 2017 and November 2024, from which ten studies met our strict inclusion criteria, focusing solely on fulvestrant monotherapy. These trials encompassed 1038 patients who had prior exposure to CDK4/6 inhibitors. The selected studies were categorized into three groups: monotherapy trials (EMERALD, SERENA-2, AMEERA-3, and ELAINE-1), combination therapy trials (CAPItello-291 and VERONICA), and CDK4/6 inhibitor rechallenge trials (post-MONARCH, PACE, PALMIRA, and MAINTAIN). The median progression-free survival for fulvestrant monotherapy was 3.18 months (range 1.9-5.3 months). Factors affecting the efficacy of fulvestrant monotherapy in second-line therapy include prior treatments, treatment duration, and genetic mutations. Given that the efficacy of fulvestrant was short-lived in the second or subsequent lines, participating in clinical trials is a vital option until a novel alternative treatment choice becomes available.

Current and Novel Treatment Options in Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Metastatic Breast Cancer

Metastatic breast cancer (mBC) remains an incurable disease, and most patients will experience disease progression during their treatment course. Although endocrine therapy remains the mainstay of treatment for hormone receptor-positive/human epidermal growth factor receptor 2-negative mBC, significant progress has been and continues to be made in the treatment of this BC subtype. The discovery of molecular markers, mutations in key cellular pathways, and genomic signatures have led to the development of novel and targeted agents, such as antibody-drug conjugates, oral selective estrogen receptor downregulators, and inhibitors of the PI3K/AKT/mTOR pathway. This has resulted in significant improvements in the survival and quality of life of patients. With the increasing number of treatment options for patients, appropriate drug sequencing remains a challenge. Treatment discussions should involve patient-physician shared decision making, with consideration of genomic data, previous lines of therapy, side effect profiles, and clinical trial enrollment.

Datopotamab Deruxtecan Versus Chemotherapy in Previously Treated Inoperable/Metastatic Hormone Receptor-Positive Human Epidermal Growth Factor Receptor 2-Negative Breast Cancer: Primary Results From TROPION-Breast01

PURPOSE

The global, phase 3, open-label, randomized TROPION-Breast01 study assessed the trophoblast cell surface antigen 2-directed antibody-drug conjugate datopotamab deruxtecan (Dato-DXd) versus investigator's choice of chemotherapy (ICC) in hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) breast cancer.

METHODS

Adult patients with inoperable/metastatic HR+/HER2‒ breast cancer, who had disease progression on endocrine therapy, for whom endocrine therapy was unsuitable, and had received one to two previous lines of chemotherapy in the inoperable/metastatic setting, were randomly assigned 1:1 to Dato-DXd (6 mg/kg once every 3 weeks) or ICC (eribulin/vinorelbine/capecitabine/gemcitabine). Dual primary end points were progression-free survival (PFS) by blinded independent central review (BICR) and overall survival (OS).

RESULTS

Patients were randomly assigned to Dato-DXd (n = 365) or ICC (n = 367). Dato-DXd significantly reduced the risk of progression or death versus ICC (PFS by BICR hazard ratio [HR], 0.63 [95% CI, 0.52 to 0.76]; P < .0001). Consistent PFS benefit was observed across subgroups. Although OS data were not mature, a trend favoring Dato-DXd was observed (HR, 0.84 [95% CI, 0.62 to 1.14]). The rate of grade ≥3 treatment-related adverse events (TRAEs) with Dato-DXd was lower than ICC (20.8% v 44.7%). The most common TRAEs (any grade; grade ≥3) were nausea (51.1%; 1.4%) and stomatitis (50%; 6.4%) with Dato-DXd and neutropenia (grouped term, 42.5%; 30.8%) with ICC.

CONCLUSION

Patients receiving Dato-DXd had statistically significant and clinically meaningful improvement in PFS and a favorable and manageable safety profile, compared with ICC. Results support Dato-DXd as a novel treatment option for patients with inoperable/metastatic HR+/HER2‒ breast cancer who have received one to two previous lines of chemotherapy in this setting.

Recent advances of antibody-drug conjugates in treating breast cancer with different HER2 status

Despite the availability of multiple treatment options for breast cancer, challenges such as adverse events, drug resistance, and disease progression persist for patients. The identification of human epidermal growth factor receptor 2 (HER2) as an oncogenic driver in a subset of breast cancers, alongside the development of HER2-targeted therapies, has significantly improved the prognosis of HER2-amplified breast cancers. However, therapeutic options remain limited for HER2-overexpressing or HER2-negative breast cancers. In response to this gap, antibody-drug conjugates (ADCs) have emerged as a promising approach. ADCs combine the specificity of monoclonal antibodies with the cytotoxic effects of chemotherapy, which allows for the targeted delivery of a cytotoxic payload to cancer cells. ADCs have been used as adjuvant chemotherapeutic treatments and salvage therapies across various breast cancer subtypes, which have greatly improved the prognosis of breast cancer patients. Numerous ongoing clinical trials seek to optimize dosing strategies and identify patient populations that would benefit most from ADCs. This review presents an updated and comprehensive overview of emerging investigational ADCs for treating breast cancer patients with various HER2 subtypes. These ADCs are spearheading a new era in targeted cancer therapy, promising to innovate treatment paradigms for both HER2-positive and HER2-low breast cancers.

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.

Datopotamab-deruxtecan in early-stage breast cancer: the sequential multiple assignment randomized I-SPY2.2 phase 2 trial

Among the goals of patient-centric care are the advancement of effective personalized treatment, while minimizing toxicity. The phase 2 I-SPY2.2 trial uses a neoadjuvant sequential therapy approach in breast cancer to further these goals, testing promising new agents while optimizing individual outcomes. Here we tested datopotamab-deruxtecan (Dato-DXd) in the I-SPY2.2 trial for patients with high-risk stage 2/3 breast cancer. I-SPY2.2 uses a sequential multiple assignment randomization trial design that includes three sequential blocks of biologically targeted neoadjuvant treatment: the experimental agent(s) (block A), a taxane-based regimen tailored to the tumor subtype (block B) and doxorubicin-cyclophosphamide (block C). Patients are randomized into arms consisting of different investigational block A treatments. Algorithms based on magnetic resonance imaging and core biopsy guide treatment redirection after each block, including the option of early surgical resection in patients predicted to have a high likelihood of pathological complete response, the primary endpoint. There are two primary efficacy analyses: after block A and across all blocks for the six prespecified breast cancer subtypes (defined by clinical hormone receptor/human epidermal growth factor receptor 2 (HER2) status and/or the response-predictive subtypes). We report results of 103 patients treated with Dato-DXd. While Dato-DXd did not meet the prespecified threshold for success (graduation) after block A in any subtype, the treatment strategy across all blocks graduated in the hormone receptor-negative HER2-Immune-DNA repair deficiency- subtype with an estimated pathological complete response rate of 41%. No new toxicities were observed, with stomatitis and ocular events occurring at low grades. Dato-DXd was particularly active in the hormone receptor-negative/HER2-Immune-DNA repair deficiency- signature, warranting further investigation, and was safe in other subtypes in patients who followed the treatment strategy. ClinicalTrials.gov registration: NCT01042379 .

Advances in Trop-2 targeted antibody-drug conjugates for breast cancer: mechanisms, clinical applications, and future directions

Breast cancer remains a leading cause of cancer-related deaths among women worldwide, highlighting the need for novel therapeutic strategies. Trophoblast cell surface antigen 2 (Trop-2), a type I transmembrane glycoprotein highly expressed in various solid tumors including all subtypes of breast cancer, has emerged as a promising target for cancer therapy. This review focuses on recent advancements in Trop-2-targeted antibody-drug conjugates (ADCs) for breast cancer treatment. We comprehensively analyzed the structure and mechanism of action of ADCs, as well as the role of Trop-2 in breast cancer progression and prognosis. Several Trop-2-targeted ADCs, such as Sacituzumab Govitecan (SG) and Datopotamab Deruxtecan (Dato-DXd), have demonstrated significant antitumor activity in clinical trials for both triple-negative breast cancer (TNBC) and hormone receptor-positive/HER2-negative (HR+/HER2-) breast cancer. We systematically reviewed the ongoing clinical studies of these ADCs, highlighting their efficacy and safety profiles. Furthermore, we explored the potential of combining Trop-2-targeted ADCs with other therapeutic modalities, including immunotherapy, targeted therapies, and small molecule inhibitors. Notably, Trop-2-targeted ADCs have shown promise in reprogramming the tumor microenvironment through multiple signaling pathways, potentially enhancing antitumor immunity. This review aims to provide new insights and research directions for the development of innovative breast cancer therapies, offering potential solutions to improve treatment outcomes and quality of life for breast cancer patients.

Understanding the chemistry & pharmacology of antibody-drug conjugates in triple-negative breast cancer with special reference to exatecan derivatives

In the spectrum of breast malignancies, triple-negative breast cancer is the most widely spreading subtype of breast cancer due to a low availability of therapeutic remedies. Recently, antibody-drug conjugates dramatically resolved the landscape for the treatment of triple-negative breast cancer. This review mainly focuses on the chemistry, structure, mechanism of action, and role of antibody-drug conjugates in triple-negative breast cancer. Datopotecan Deruxtecan (Dato-DXd) is a new-generation ADC showing encouraging results for TNBC. In this review, we have also emphasized TROP-2-directed Datopotamab deruxtecan ADCs to treat triple-negative breast cancer, its synthesis, mechanism of action, pharmacokinetics, pharmacodynamics, adverse events, and their ongoing clinical trials.

Protein biomarkers for subtyping breast cancer and implications for future research: a 2024 update

INTRODUCTION

Breast cancer subtyping is used clinically for diagnosis, prognosis, and treatment decisions. Subtypes are categorized by cell of origin, histomorphology, gene expression signatures, hormone receptor status, and/or protein levels. Categorizing breast cancer based on gene expression signatures aids in assessing a patient's recurrence risk. Protein biomarkers, on the other hand, provide functional data for selecting therapies for primary and recurrent tumors. We provide an update on protein biomarkers in breast cancer subtypes and their application in prognosis and therapy selection.

AREAS COVERED

Protein pathways in breast cancer subtypes are reviewed in the context of current protein-targeted treatment options. PubMed, Science Direct, Scopus, and Cochrane Library were searched for relevant studies between 2017 and 17 August 2024.

EXPERT OPINION

Post-translationally modified proteins and their unmodified counterparts have become clinically useful biomarkers for defining breast cancer subtypes from a therapy perspective. Tissue heterogeneity influences treatment outcomes and disease recurrence. Spatial profiling has revealed complex cellular subpopulations within the breast tumor microenvironment. Deciphering the functional relationships between and within tumor clonal cell populations will further aid in defining breast cancer subtypes and create new treatment paradigms for recurrent, drug resistant, and metastatic disease.

Synergizing Immunotherapy and Antibody-Drug Conjugates: New Horizons in Breast Cancer Therapy

The advent of immunotherapy and antibody-drug conjugates (ADCs) have revolutionized breast cancer treatment, offering new hope to patients. However, challenges, such as resistance and limited efficacy in certain cases, remain. Recently, the combination of these therapies has emerged as a promising approach to address these challenges. ADCs play a crucial role by delivering cytotoxic agents directly to breast cancer cells, minimizing damage to healthy tissue and enhancing the tumor-killing effect. Concurrently, immunotherapies harness the body's immune system to recognize and eliminate cancer cells. This integration offers potential to overcome resistance mechanisms and significantly improve therapeutic outcomes. This review explores the rationale behind combining immunotherapies with ADCs, recent advances in this field, and the potential implications for breast cancer treatment.

Trop2-targeted therapy in breast cancer

Human trophoblastic cell surface antigen 2 (Trop2) is a glycoprotein, a cellular marker of trophoblastic and stem cells, and a calcium signaling transducer involved in several signaling pathways, leading to the proliferation, invasion, and metastasis of tumors. It is expressed at a low level in normal epithelial cells, but at a high level in many tumors, making it an ideal target for cancer therapy. According to previous literature, Trop2 is broadly expressed in all breast cancer subtypes, especially in triple negative breast cancer (TNBC). Several clinical trials have demonstrated the effectiveness of Trop2-targeted therapy in breast cancer. Sacituzumab govitecan (SG) is a Trop2-targeted antibody-drug conjugate (ADC) that has been approved for the treatment of metastatic TNBC and hormone receptor-positive (HR+) and human epidermal growth factor receptor 2-negative (HER2-) breast cancer. This article reviews the structure and function of Trop2, several major Trop2-targeted ADCs, other appealing novel Trop2-targeted agents and relevant clinical trials to provide a landscape of how Trop2-targeted treatments will develop in the future.

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.

The treatment pattern of advanced HR-positive and HER2-negative breast cancer in central southern China: a hospital-based cross-sectional study

AIMS

This investigation aims to elucidate the treatment status of advanced HR+/HER2- breast cancer patients in Hunan Province of Central Southern China from November 2021 to December 2022.

METHODS

Data from 301 patients with advanced HR+/HER2- breast cancer were collected from the breast cancer investigation project in Hunan under the guidance of the Chinese Society of Clinical Oncolfogy (CSCO). The data included the clinical characteristics of patients and the status of first-line and second-line rescue treatment.

RESULTS

First-line chemotherapy and endocrine therapy for mBC accounted for 40% (121/301) and 60% (180/301) of treatments, respectively. AI (21%), AI plus CDK4/6 inhibitor (28%), and fulvestrant (24%) or fulvestrant plus CDK4/6 inhibitor (18%) were the most common first-line endocrine therapies. Taxane-based chemotherapy was the most common first-line chemotherapy (59%). Second-line chemotherapy and endocrine therapy for mBC accounted for 43% (72/166) and 57% (94/166) of treatments, respectively. Fulvestrant (23%) or fulvestrant plus CDK4/6 inhibitor (29%) were the most common second-line endocrine therapies. The prevalences of AI and AI plus CDK4/6 inhibitor decreased to 19% and 11%, respectively. T (taxane)-based chemotherapy was still the most common chemotherapy regimen (46%). Third-line chemotherapy was more prevalent than endocrine therapy (57% vs. 41%). T (taxane)-based chemotherapy was still the most common chemotherapy regimen (46%). Fulvestrant plus CDK4/6 inhibitor was the most common endocrine therapy (33%). AI, AI plus CDK4/6 inhibitor, and fulvestrant accounted for 21%, 12% and 18% of third-line endocrine therapies, respectively.

CONCLUSIONS

Compared to chemotherapy, endocrine therapy was a more favorable choice for first-line and second-line treatment for HR+/HER2- advanced breast cancer patients in Hunan Province.

Dark force rising: Reawakening and targeting of fetal-like stem cells in colorectal cancer

Stem cells play pivotal roles in maintaining intestinal homeostasis, orchestrating regeneration, and in key steps of colorectal cancer (CRC) initiation and progression. Intriguingly, adult stem cells are reduced during many of these processes. On the contrary, primitive fetal programs, commonly detected in development, emerge during tissue repair, CRC metastasis, and therapy resistance. Recent findings indicate a dynamic continuum between adult and fetal stem cell programs. We discuss critical mechanisms facilitating the plasticity between stem cell states and highlight the heterogeneity observed upon the appearance of fetal-like states. We focus on therapeutic opportunities that arise by targeting fetal-like CRC cells and how those concepts can be translated into the clinic.

Systemic Therapy in Breast Cancer

Therapeutic advances in breast cancer have significantly improved outcomes in recent decades. In the early setting, there has been a gradual shift from adjuvant-only to neoadjuvant strategies, with a growing focus on customizing post-neoadjuvant treatments through escalation and de-escalation based on pathologic response. At the same time, the transition from a pre-genomic to a post-genomic era, utilizing specific assays in the adjuvant setting and targeted sequencing in the advanced stage, has deepened our understanding of disease biology and aided in identifying molecular markers associated with treatment benefit. Finally, the introduction of new drug classes such as antibody-drug conjugates, and the incorporation in the (neo)adjuvant setting of therapies previously investigated in the advanced stage, like immunotherapy and CDK4-6 inhibitors, poses new challenges in treatment sequencing.

Current Status and Future Perspectives of Antibody-Drug Conjugates in Hormone Receptor-Positive Breast Cancer

Breast cancer is the most common cancer type in women. The vast majority of breast cancer patients have hormone receptor-positive (HR+) tumors. In advanced HR+ breast cancer, the combination of endocrine therapy with cyclin-dependent kinase 4/6 (CDK4/6) inhibitors is considered the standard of care in the front-line setting. Nevertheless, resistance to hormonal therapy and CDK4/6 inhibitors eventually occurs, leading to progression of the disease. Antibody-drug conjugates (ADCs) comprise a promising therapeutic choice with significant efficacy in patients with HR+ breast cancer, which is resistant to endocrine treatment. ADCs typically consist of a cytotoxic payload attached by a linker to a monoclonal antibody that targets a specific tumor-associated antigen, offering the advantage of a more selective delivery of chemotherapy to cancer cells. In this review, we focus on the ADC mechanisms of action, their toxicity profile and therapeutic uses as well as on related biomarkers and future perspectives in advanced HR+ breast cancer.

Emerging pharmacotherapy trends in preventing and managing oral mucositis induced by chemoradiotherapy and targeted agents

INTRODUCTION

The introduction of targeted therapy and immunotherapy has tremendously changed the clinical outcomes and prognosis of cancer patients. Despite innovative pharmacological therapies and improved radiotherapy (RT) techniques, patients continue to suffer from side effects, of which oral mucositis (OM) is still the most impactful, especially for quality of life.

AREAS COVERED

We provide an overview of current advances in cancer pharmacotherapy and RT, in relation to their potential to cause OM, and of the less explored and more recent literature reports related to the best management of OM. We have analyzed natural/antioxidant agents, probiotics, mucosal protectants and healing coadjuvants, pharmacotherapies, immunomodulatory and anticancer agents, photobiomodulation and the impact of technology.

EXPERT OPINION

The discovery of more precise pathophysiologic mechanisms of CT and RT-induced OM has outlined that OM has a multifactorial origin, including direct effects, oxidative damage, upregulation of immunologic factors, and effects on oral flora. A persistent upregulated immune response, associated with factors related to patients' characteristics, may contribute to more severe and long-lasting OM. The goal is strategies to conjugate individual patient, disease, and therapy-related factors to guide OM prevention or treatment. Despite further high-quality research is warranted, the issue of prevention is paramount in future strategies.

Cyclin-dependent kinase 2 (CDK2) inhibitors and others novel CDK inhibitors (CDKi) in breast cancer: clinical trials, current impact, and future directions

Aberrant cyclin-dependent kinase 2 (CDK2) activation has been identified as a main resistance mechanism to CDK4/6 inhibition in hormone-receptor positive (HR+) breast cancer. Additionally, consistent preclinical evidence states its crucial role in MYC and CCNE1 overexpressed cancer survival, such as triple-negative breast cancers (TNBC), thus representing an appealing and relatively unexplored target treatment opportunity. Despite emerging initial results of novel CDK2 inhibitors (CDK2i) activity, a comprehensive outcomes collection is currently absent from the scientific literature. We aim to provide an overview of ongoing clinical trials involving CDK2i in the context of metastatic breast cancer (mBC), either as monotherapy or in combination with other agents. The review extends beyond CDK2i to encompass novel emerging CDK4 inhibitors, combined CDK2/4/6 inhibitors, and the well-known pan-CDK inhibitors including those specifically directed at CDK2. Delving into the results, we critically appraise the observed clinical efficacy and offer valuable insights into their potential impact and future applications.

Targeting Sphingosine-1-Phosphate Signaling in Breast Cancer

In recent years, newly emerging therapies, such as immune checkpoint inhibitors and antibody-drug conjugates, have further improved outcomes for breast cancer patients. However, recurrent and metastatic breast cancer often eventually develops resistance to these drugs, and cure is still rare. As such, the development of new therapies for refractory breast cancer that differ from conventional mechanisms of action is necessary. Sphingosine-1-phosphate (S1P) is a key molecule with a variety of bioactive activities, including involvement in cancer cell proliferation, invasion, and metastasis. S1P also contributes to the formation of the cancer microenvironment by inducing surrounding vascular- and lymph-angiogenesis and regulating the immune system. In this article, we outline the basic mechanism of action of S1P, summarize previous findings on the function of S1P in cancer cells and the cancer microenvironment, and discuss the clinical significance of S1P in breast cancer and the therapeutic potential of targeting S1P signaling.

Raludotatug Deruxtecan, a CDH6-Targeting Antibody-Drug Conjugate with a DNA Topoisomerase I Inhibitor DXd, Is Efficacious in Human Ovarian and Kidney Cancer Models

Cadherin-6 (CDH6) is expressed in several cancer types, but no CDH6-targeted therapy is currently clinically available. Here, we generated raludotatug deruxtecan (R-DXd; DS-6000), a novel CDH6-targeting antibody-drug conjugate with a potent DNA topoisomerase I inhibitor, and evaluated its properties, pharmacologic activities, and safety profile. In vitro pharmacologic activities and the mechanisms of action of R-DXd were assessed in serous-type ovarian cancer and renal cell carcinoma cell lines. In vivo pharmacologic activities were evaluated with several human cancer cell lines and patient-derived xenograft mouse models. The safety profile in cynomolgus monkeys was also assessed. R-DXd exhibited CDH6 expression-dependent cell growth-inhibitory activity and induced tumor regression in xenograft models. In this process, R-DXd specifically bound to CDH6, was internalized into cancer cells, and then translocated to the lysosome. The DXd released from R-DXd induced the phosphorylation of Chk1, a DNA damage marker, and cleaved caspase-3, an apoptosis marker, in cancer cells. It was also confirmed that the DXd payload had a bystander effect, passing through the cell membrane and impacting surrounding cells. The safety profile of R-DXd was favorable and the highest non-severely toxic dose was 30 mg/kg in cynomolgus monkeys. R-DXd demonstrated potent antitumor activity against CDH6-expressing tumors in mice and an acceptable safety profile in monkeys. These findings indicate the potential of R-DXd as a new treatment option for patients with CDH6-expressing serous-type ovarian cancer and renal cell carcinoma in a clinical setting.

Breaking barriers in triple negative breast cancer (TNBC) - Unleashing the power of antibody-drug conjugates (ADCs)

Antibody-drug conjugates (ADCs) represent a novel class of molecules composed of a recombinant monoclonal antibody targeted to a specific cell surface antigen, conjugated to a cytotoxic agent through a cleavable or non-cleavable synthetic linker. The rationale behind the development of ADCs is to overcome the limitations of conventional chemotherapy, such as the narrow therapeutic window and the emergence of resistance mechanisms. ADCs had already revolutionized the treatment algorithm of HER2-positive breast cancer. Currently, emergent non-HER2 targeted ADCs are gaining momentum, with special focus on triple-negative disease therapeutic landscape. Sacituzumab govitecan (SG) is an ADC consisting of a humanized monoclonal antibody hRS7 targeting trophoblast cell surface antigen 2 (Trop2), linked to the topoisomerase I inhibitor SN-38 by a hydrolysable linker. It currently stands as the only non-HER2 targeted ADC that already received approval for the treatment of unresectable locally advanced or metastatic triple negative breast cancer (TNBC) in patients who had received two or more prior systemic therapies, with at least one for advanced disease. The purpose of these review is to analyze the available evidence regarding ADCs in TNBC, alongside with providing an overview on the ongoing and future research horizons in this field.

Therapeutic evolution in HR+/HER2- breast cancer: from targeted therapy to endocrine therapy

Breast cancer, a complex and varied disease, has four distinct subtypes based on estrogen receptor and human epidermal growth factor receptor 2 (HER2) levels, among which a significant subtype known as HR+/HER2-breast cancer that has spurred numerous research. The prevalence of breast cancer and breast cancer-related death are the most serious threats to women's health worldwide. Current progress in treatment strategies for HR+/HER2-breast cancer encompasses targeted therapy, endocrine therapy, genomic immunotherapy, and supplementing traditional methods like surgical resection and radiotherapy. This review article summarizes the current epidemiology of HR+/HER2-breast cancer, introduces the classification of HR+/HER2-breast cancer and the commonly used treatment methods. The mechanisms of action of various drugs, including targeted therapy drugs and endocrine hormone therapy drugs, and their potential synergistic effects are deeply discussed. In addition, clinical trials of these drugs that have been completed or are still in progress are included.

Antibodies to watch in 2024

The 'Antibodies to Watch' article series provides an annual summary of commercially sponsored monoclonal antibody therapeutics currently in late-stage clinical development, regulatory review, and those recently granted a first approval in any country. In this installment, we discuss key details for 16 antibody therapeutics granted a first approval in 2023, as of November 17 (lecanemab (Leqembi), rozanolixizumab (RYSTIGGO), pozelimab (VEOPOZ), mirikizumab (Omvoh), talquetamab (Talvey), elranatamab (Elrexfio), epcoritamab (EPKINLY), glofitamab (COLUMVI), retifanlimab (Zynyz), concizumab (Alhemo), lebrikizumab (EBGLYSS), tafolecimab (SINTBILO), narlumosbart (Jinlitai), zuberitamab (Enrexib), adebrelimab (Arelili), and divozilimab (Ivlizi)). We briefly review 26 product candidates for which marketing applications are under consideration in at least one country or region, and 23 investigational antibody therapeutics that are forecast to enter regulatory review by the end of 2024 based on company disclosures. These nearly 50 product candidates include numerous innovative bispecific antibodies, such as odronextamab, ivonescimab, linvoseltamab, zenocutuzumab, and erfonrilimab, and antibody-drug conjugates, such as trastuzumab botidotin, patritumab deruxtecan, datopotamab deruxtecan, and MRG002, as well as a mixture of two immunocytokines (bifikafusp alfa and onfekafusp alfa). We also discuss clinical phase transition and overall approval success rates for antibody therapeutics, which are crucial to the biopharmaceutical industry because these rates inform decisions about resource allocation. Our analyses indicate that these molecules have approval success rates in the range of 14-32%, with higher rates associated with antibodies developed for non-cancer indications. Overall, our data suggest that antibody therapeutic development efforts by the biopharmaceutical industry are robust and increasingly successful.

Sequencing Antibody Drug Conjugates in Breast Cancer: Exploring Future Roles

Antibody drug conjugates (ADCs) have emerged as a highly effective treatment strategy across breast cancer (BC) subtypes, including human epidermal growth factor receptor 2-positive (HER2+), hormone-receptor positive (ER/PR+), and triple-negative breast cancer (TNBC). Over the past twenty years, ADCs have undergone relevant evolutions, from target diversity to payload ratio, to linker design, allowing for a progressive increase in their efficacy. From the first-generation ADC, trastuzumab emtansine (T-DM1), approved in 2013 for HER2+ breast cancer, to next generation ADCs such as sacituzumab govitecan and trastuzumab deruxtecan, to emerging ADCs on the horizon, we continue to see unparalleled efficacy compared to traditional chemotherapy. However, each ADC has brought a new cadre of adverse events for clinicians and patients to manage. Importantly, with the development and approval of several ADCs to treat metastatic breast cancer, there are unanswered clinical questions surrounding how to optimally sequence treatment for patients who may be candidates for more than one ADC and, in general, how to treat patients beyond progression on ADCs. From bench to bedside, in this review, we will discuss the pharmacology and current indications for the novel ADCs trastuzumab deruxtecan and sacituzumab govitecan. Highlighting emerging ADCs and ongoing clinical trials, we will anticipate the changes in the breast cancer treatment paradigm. Lastly, we will outline the available data and current approaches for adverse event management and sequencing strategies for ADCs in clinical practice, including proposed mechanisms of resistance.