HER2-Positive Gastric Cancer and Antibody Treatment: State of the Art and Future Developments

Despite a decreasing incidence in Western countries, gastric cancer is among the most common cancer subtypes globally and is associated with one of the highest tumor-related mortality rates. Biomarkers play an increasing role in the treatment against gastric cancer. HER2 was one of the first biomarkers that found its way into clinical practice. Since the ToGA trial, trastuzumab has been part of first-line palliative chemotherapy in metastatic or unresectable gastric cancer. HER2-targeting agents, such as the tyrosine kinase inhibitor lapatinib, the antibody drug conjugate (ADC) trastuzumab-emtansine or dual HER2 inhibition (pertuzumab and trastuzumab), have been investigated in the second-line setting but led to negative study results. More recently, the ADC trastuzumab-deruxtecan was authorized after the failure of trastuzumab-based treatment. However, further improvements in HER2-directed therapy are required as resistance mechanisms and HER2 heterogeneity limit the existing treatment options. This review aims to give an overview of the current standard-of-care HER2-directed therapy in gastric cancer, as well as its challenges and future developments.

Correlation of HER2 Protein Level With mRNA Level Quantified by RNAscope in Breast Cancer

Trastuzumab deruxtecan (T-DXd) has been approved by the US Food and Drug Administration (FDA) to treat patients with metastatic HER2-positive and HER2-low breast cancer, and clinical trials are examining its efficacy against early-stage breast cancer. Current HER2 immunohistochemical (IHC) assays are suboptimal in evaluating HER2-low breast cancers and identifying which patients would benefit from T-DXd. HER2 expression in 526 breast cancer tissue microarray (TMA) cores was measured using the FDA-approved PATHWAY and HercepTest IHC assays, and the corresponding RNA levels were evaluated by RNAscope. HER2 protein levels by regression analysis using a quantitative immunofluorescence score against cell line arrays with known HER2 protein levels determined by mass spectrometry were available in 48 of the cores. RNAscope was also performed in 32 metastatic biopsies from 23 patients who were subsequently treated with T-DXd, and the results were correlated with response rate. HER2 RNA levels by RNAscope strongly correlated with HER2 protein levels (P < .0001) and with HER2 IHC H-scores from the PATHWAY and HercepTest assays (P < .0001). However, neither protein levels nor RNA levels significantly differed between cases scored 0, ultralow, and 1+ by PATHWAY and HercepTest. The RNA levels were significantly higher (P = .030) in responders (6.4 ± 8.2 dots/cell, n = 12) than those in nonresponders (2.6 ± 2.2, n = 20) to T-DXd. RNAscope is a simple assay that can be objectively quantified and is a promising alternative to current IHC assays in evaluating HER2 expression in breast cancers, especially HER2-low cases, and may identify patients who would benefit from T-DXd.

Trastuzumab deruxtecan in human epidermal growth factor receptor 2-positive breast cancer brain metastases: a systematic review and meta-analysis

BACKGROUND

Trastuzumab deruxtecan (T-DXd) has shown promising results in patients with breast cancer brain metastases (BCBMs). We conducted a systematic review and meta-analysis to evaluate the effectiveness and safety of T-DXd in the human epidermal growth factor receptor 2 (HER2)-positive BCBM population.

PATIENTS AND METHODS

We searched PubMed, Embase, and Cochrane Library databases as well as American Society of Clinical Oncology (ASCO), European Society for Medical Oncology (ESMO), and San Antonio Breast Cancer Symposium (SABCS) websites for clinical trials (CTs) and observational studies evaluating T-DXd in patients with HER2-positive BCBM. Heterogeneity was assessed with I2 statistics. Random effects models were used for all statistical analyses, which were carried out using R software (version 4.2.2).

RESULTS

Ten studies were included, six CTs (n = 189) and four observational studies (n = 130), with a total of 319 patients. The median progression-free survival was 15 months [95% confidence interval (CI) 13.9-16.1 months]. The objective response rate (ORR) was 61% (95% CI 52% to 70%), and the intracranial (IC)-ORR was 61% (95% CI 54% to 69%). No significant differences in ORR and IC-ORR were observed between CTs and observational studies (P = 0.31 and 0.58, respectively). The clinical benefit rate (CBR) was 80% (95% CI 52% to 94%), and the IC-CBR was 70% (95% CI 54% to 82%). The ORR was 68% (95% CI 57% to 77%) in the subgroup of patients with stable BMs and 60% (95% CI 48%-72%) in patients with active BM, with no significant difference between groups (P = 0.35).

CONCLUSIONS

Our systematic review and meta-analysis supports the IC activity of T-DXd in patients with stable BM and active BM.

TRIAL REGISTRATION

International Prospective Register of Systematic Reviews (PROSPERO) under the protocol number CRD42023422589.

Advances in the study of marketed antibody-drug Conjugates (ADCs) for the treatment of breast cancer

Breast cancer continues to have a high incidence rate among female malignancies. Despite significant advancements in treatment modalities, the heterogeneous nature of breast cancer and its resistance to various therapeutic approaches pose considerable challenges. Antibody-drug conjugates (ADCs) effectively merge the specificity of antibodies with the cytotoxicity of chemotherapeutic agents, offering a novel strategy for precision treatment of breast cancer. Notably, trastuzumab emtansine (T-DM1) has provided a new therapeutic option for HER2-positive breast cancer patients globally, especially those resistant to conventional treatments. The development of trastuzumab deruxtecan (T-DXd) and sacituzumab govitecan (SG) has further broadened the applicability of ADCs in breast cancer therapy, presenting new hopes for patients with low HER2 expression and triple-negative breast cancer. However, the application of ADCs presents certain challenges. For instance, their treatment may lead to adverse reactions such as interstitial lung disease, thrombocytopenia, and diarrhea. Moreover, prolonged treatment could result in ADCs resistance, complicating the therapeutic process. Economically, the high costs of ADCs might hinder their accessibility in low-income regions. This article reviews the structure, mechanism of action, and clinical trials of commercially available ADCs for breast cancer treatment, with a focus on the clinical trials of the three drugs, aiming to provide insights for clinical applications and future research.

Positive response to trastuzumab deruxtecan in a patient with HER2-mutant NSCLC after multiple lines therapy, including T-DM1: a case report

Human epidermal growth factor 2 (HER2) mutations are uncommon in non-small cell lung cancer (NSCLC), and the lack of established, effective, targeted drugs has resulted in a persistently poor prognosis. Herein, we report the case of a non-smoking, 58-year-old man diagnosed with lung adenocarcinoma (cT3N0M1c, stage IVB) harboring a HER2 mutation (Y772_A775dupYVMA) and PD-L1 (-). The patient's Eastern Cooperative Oncology Group performance status (PS) score was assessed as 1. He commenced first-line treatment with chemotherapy, followed by immuno-chemotherapy, and with disease progression, he received HER2-targeted therapy and chemotherapy with an anti-angiogenic agent. However, HER2-targeted therapy, including pan-HER tyrosine kinase inhibitors (afatinib, pyrotinib, and pozitinib) and antibody-drug conjugate (T-DM1), produced only stable disease (SD) as the best response. After the previously described treatment, primary tumor recurrence and multiple brain metastases were observed. Despite the patient's compromised overall physical condition with a PS score of 3-4, he was administered T-DXd in addition to whole-brain radiotherapy (WBRT). Remarkably, both intracranial metastases and primary lesions were significantly reduced, he achieved a partial response (PR), and his PS score increased from 3-4 to 1. He was then treated with T-DXd for almost 9 months until the disease again progressed, and he did not discontinue the drug despite the occurrence of myelosuppression during this period. This is a critical case as it exerted an effective response to T-DXd despite multiple lines therapy, including T-DM1. Simultaneously, despite the occurrence of myelosuppression in the patient during T-DXd, it was controlled after aggressive treatment.

Opportunities and Challenges for a Histology-Agnostic Utilization of Trastuzumab Deruxtecan

PURPOSE OF REVIEW

This review delves into the prospects and challenges offered by a potential pan-histological utilization of trastuzumab deruxtecan (T-DXd) in patients with advanced solid tumors.

RECENT FINDINGS

The HER2-targeted antibody-drug conjugate (ADC) T-DXd has shown broad activity across cancer types, with current indications for patients with biomarker-selected breast, gastric, and non-small-cell lung cancer and relevant activity observed in multiple histology-specific trials. Moreover, two recently reported phase 2 trials (DESTINY-Pantumor02 and HERALD) have supported the potential for a pan-cancer utilization of this ADC in patients with advanced cancers expressing HER2 or with HER2 amplifications. By improving the delivery of cytotoxic chemotherapy, ADCs have allowed for meaningful clinical advantages in broad populations of cancer patients, often leading to survival advantages over conventional chemotherapy. Notably, the broad spectrum of activity of certain ADCs has led to the hypothesis of a histology-agnostic utilization based on detecting specific biomarkers, similar to what is already established for certain targeted treatments and immunotherapy. To date, T-DXd has shown the broadest activity across cancer types, with current approvals in breast, gastric, and lung cancer, and relevant antitumor activity observed in a multiplicity of additional cancer types. The optimization of the drug dose, identification of predictive biomarkers, and clarification of mechanisms of resistance will be critical steps in view of a pan-histological expansion in the use of T-DXd.

CF33-hNIS-anti-PD-L1 oncolytic virus followed by trastuzumab-deruxtecan in a patient with metastatic triple negative breast cancer: a case study

Prognosis of metastatic triple negative breast cancer (mTNBC) remains poor despite recent advances in therapeutic options. Trastuzumab deruxtecan (T-DXd) has shown promising efficacy in patients with human epidermal growth factor receptor 2 (HER2)-low breast cancer, which is defined by immunohistochemistry (IHC) 1+ or 2+ and lack of HER2 amplification by fluorescence in situ hybridization (FISH) testing. The purpose of the study is to evaluate the safety and initial evidence of efficacy of intratumoral administration of CF33-hNIS-anti-PD-L1 (CHECKvacc) against mTNBC. Oncolytic virus CHECKvacc intratumoral injection is currently undergoing investigation in patients with mTNBC as a single agent (NCT05081492). The patient was enrolled on the clinical trial CHECKvacc for the Treatment of Metastatic Triple Negative Breast Cancer, received a single dose of CHECKvacc, and discontinued the study due to lack of immediate response. We report a case of a patient with mTNBC who was heavily pretreated and presented with extensive dermal metastasis. Two dermal metastasis biopsies in 2021 showed HER2 0 by IHC. The patient received a single dose of CHECKvacc and discontinued the study due to lack of immediate response. Twenty-five days later, the patient received treatment with T-DXd, and her tumor regressed significantly. The patient's disease-free survival was 10 months (December 2021-October 2022). The sequential treatment with intratumoral injection of CHECKvacc followed by T-DXd may have significant clinical activity in select patients with heavily pretreated mTNBC. ClinicalTrials.gov NCT05081492.

Immuno-PET Detects Antibody-Drug Potency on Coadministration with Statins

The human epidermal growth factor receptor 2 (HER2)-targeting trastuzumab emtansine (T-DM1) and trastuzumab deruxtecan (T-DXd) are antibody-drug conjugates (ADC) clinically used to treat HER2-positive breast cancer, with the latter receiving clinical approval in 2021 for HER2-positive gastric cancer. Lovastatin, a cholesterol-lowering drug, temporally elevates cell-surface HER2 in ways that enhance HER2-ADC binding and internalization. Methods: In an NCIN87 gastric xenograft model and a gastric patient-derived xenograft model, we used the 89Zr-labeled or 64Cu-labeled anti-HER2 antibody trastuzumab to investigate the dosing regimen of ADC therapy with and without coadministration of lovastatin. We compared the ADC efficacy of a multiple-dose ADC regime, which replicates the clinical dose regimen standard, with a single-dose regime. Results: T-DM1/lovastatin treatment inhibited tumor growth, regardless of multiple- or single-dose T-DM1 administration. Coadministration of lovastatin with T-DM1 or T-DXd as a single dose enhanced tumor growth inhibition, which was accompanied by a decrease in signal on HER2-targeted immuno-PET and a decrease in HER2-mediated signaling at the cellular level. DNA damage signaling was increased on ADC treatment in vitro. Conclusion: Our data from a gastric cancer xenograft show the utility of HER2-targeted immuno-PET to inform the tumor response to ADC therapies in combination with modulators of cell-surface target availability. Our studies also demonstrate that statins enhance ADC efficacy in both a cell-line and a patient-derived xenograft model in ways that enable a single-dose administration of the ADC.

HER2-Low Breast Cancer: Current Landscape and Future Prospects

More than 50% of breast cancers are currently defined as "Human epidermal growth factor receptor 2 (HER2) low breast cancer (BC)", with HER2 immunohistochemistry (IHC) scores of +1 or +2 with a negative fluorescence in situ hybridization (FISH) test. In most studies that compared the clinical and biological characteristics of HER2-low BC with HER2-negative BC, HER2-low was not associated with unique clinical and molecular characteristics, and it seems that the importance of HER2 in these tumors is being a docking site for the antibody portion of antibody drug conjugates (ADCs). Current pathological methods may underestimate the proportion of BCs that express low levels of HER2 due to analytical limitations and tumor heterogeneity. In this review we summarize and contextualize the most recent literature on HER2-low breast cancers, including clinical and translational studies We also review the challenges of assessing low HER2 expression in BC and discuss the current and future therapeutic landscape for these tumors.

Cost-effectiveness and Value-based Pricing of Trastuzumab Deruxtecan in Metastatic Breast Cancer With Low HER2 Expression

BACKGROUND

Recently, the DESTINY-Breast04 trial revealed that trastuzumab deruxtecan (T-DXd) significantly prolonged overall survival in patients with human epidermal growth factor receptor 2 (HER2)-low metastatic breast cancer (MBC). Considering the extraexpensive price of the new drug, a cost-effectiveness analysis of T-DXd is necessary to perform in the United States. In addition, because T-DXd has not been marketed in China, the pricing is a very important driver for the cost-effectiveness of T-DXd. The range of drug costs for which T-DXd could be considered cost-effective from a Chinese healthcare system perspective was explored.

METHODS

We developed a Markov model to evaluate the cost-effectiveness of T-DXd versus physician's choice of chemotherapy (PCC). The simulation time horizon for this model was the life-time of patients. Transition probabilities were based on data from the DESTINY-Breast04 trial. Health utility data were derived from published studies. Outcome measures were costs (in 2022 US$), life-years (LYs), quality-adjusted LYs (QALYs), and the incremental cost-effectiveness ratio (ICER). One-way and probabilistic sensitivity analyses assessed the uncertainty of key model parameters and their joint impact on the base-case results.

RESULTS

The model predicted that T-DXd provided an improvement of 0.84 LYs and 0.58 QALYs compared to PCC, with an ICER of $259,452.05 per QALY in the United States and $87,646.40 per QALY in China. The one-way sensitivity analysis demonstrated that the price of T-DXd had the greatest impact on ICERs. Probabilistic sensitivity analysis predicted that the probabilities of T-DXd being cost-effective compared to PCC were 7.2% and 0% at a willingness-to-pay of $150,000 per QALY in the United States and $36,475 per QALY (3 times the per capita gross domestic product) in China, respectively. Subgroup analyses showed that T-DXd was more effective for patients without visceral disease at baseline, followed by patients with Asian ethnic, patients without prior CDK 4/6 inhibitors therapy, and patients with HER2-1+ (IHC detection) status.

CONCLUSION

T-DXd was unlikely to offer a reasonable value for the money spent compared to PCC for patients with HER2-low MBC in the United States. A value-based price for T-DXd was reduced by 51% in the United States and less than $1950 per cycle in China.

HER2 Low Breast Cancer: A New Subtype or a Trojan for Cytotoxic Drug Delivery?

Despite the great progress made in the understanding of the biological behavior of certain types of invasive breast cancer, there is still no single histological or molecular classification that encompasses such diversity and accurately predicts the clinical course of distinct breast cancer subtypes. The long-lasting classification of breast cancer as HER2-positive vs. HER2-negative has recently come into question with the discovery of new antibody drug conjugates (ADC), which are proven to be remarkably efficient in treating HER2-low breast cancer. The HER2-low paradigm has challenged the traditional understanding of HER2 overexpression and emphasized the need for more robust HER2 testing in order to encompass HER2 intratumoral heterogeneity and spatial distribution more accurately. It is yet to be seen if low HER2 will remain merely a marker of HER2-equipped tumors targetable with ADCs or if distinctive molecular and phenotypic groups within HER2-low tumors will eventually be discerned.

Trastuzumab deruxtecan in patients with central nervous system involvement from HER2-positive breast cancer: The DEBBRAH trial

BACKGROUND

Trastuzumab deruxtecan (T-DXd) has shown durable antitumor activity in pretreated patients with HER2-positive advanced breast cancer (ABC), but its efficacy has not yet been evaluated in patients with active brain metastases (BMs). DEBBRAH aims to assess T-DXd in patients with HER2-positive or HER2-low ABC and central nervous system involvement.

METHODS

This ongoing, five-cohort, phase II study (NCT04420598) enrolled patients with pretreated HER2-positive or HER2-low ABC with stable, untreated, or progressing BMs, and/or leptomeningeal carcinomatosis. Here, we report findings from HER2-positive ABC patients with non-progressing BMs after local therapy (n = 8; cohort 1), asymptomatic untreated BMs (n = 4; cohort 2), or progressing BMs after local therapy (n = 9; cohort 3). Patients received 5.4 mg/kg T-DXd intravenously once every 21 days. The primary endpoint was 16-week progression-free survival (PFS) for cohort 1 and intracranial objective response rate (ORR-IC) for cohorts 2 and 3.

RESULTS

As of October 20, 2021, 21 patients received T-DXd. In cohort 1, 16-week PFS rate was 87.5% (95%CI, 47.3-99.7; P < .001). ORR-IC was 50.0% (95%CI, 6.7-93.2) in cohort 2 and 44.4% (95%CI, 13.7-78.8; P < .001) in cohort 3. Overall, the ORR-IC in patients with active BMs was 46.2% (95%CI, 19.2-74.9). Among patients with measurable intracranial or extracranial lesions at baseline, the ORR was 66.7% (12 out of 18 patients; 95%CI, 41.0-86.7), 80.0% (95%CI, 28.4-99.5) in cohort 1, 50.0% (95%CI, 6.7-93.2) in cohort 2, and 66.7% (95%CI, 29.9-92.5) in cohort 3. All responders had partial responses. The most common adverse events included fatigue (52.4%; 4.8% grade ≥3), nausea (42.9%; 0% grade ≥3), neutropenia (28.6%; 19% grade ≥3), and constipation (28.6%; 0% grade ≥3). Two (9.5%) patients suffered grade 1 interstitial lung disease/pneumonitis.

CONCLUSIONS

T-DXd showed intracranial activity with manageable toxicity and maintained the quality of life in pretreated HER2-positive ABC patients with stable, untreated, or progressing BMs. Further studies are needed to validate these results in larger cohorts.

Current and future landscape of targeted therapy in HER2-positive advanced breast cancer: redrawing the lines

BACKGROUND

Evidence to date supports continued human epidermal growth factor receptor 2 (HER2) suppression beyond progression on HER2-directed therapy for advanced HER2-positive breast cancer. Data from several phase II and III trials evaluating HER2-directed therapy following second-line T-DM1 have recently become available.

METHODS

We performed a systematic search of the published and presented literature to identify phase II and phase III trials assessing novel HER2-targeted agents as third-line therapy or beyond for HER2-positive advanced breast cancer using search terms 'breast cancer' AND 'HER2' AND 'advanced' AND ('phase II' OR 'phase III').

RESULTS

Eight clinical trials reporting efficacy outcomes on third-line or greater HER2-directed therapy for HER2-positive advanced breast cancer were identified. In phase III trials, margetuximab and neratinib combinations demonstrated significant 1.3-month (hazard ratio, HR = 0.71, p < 0.001) and 0.1-month (HR = 0.76, p = 0.006) net improvements in median progression-free survival (PFS), respectively, with no significant improvements in overall survival (OS). Tucatinib added to trastuzumab and capecitabine demonstrated a significant 2.7-month improvement in median PFS (HR = 0.57, p < 0.00001) and a 5.5-month improvement in median OS (HR = 0.73, p = 0.004) in a randomized phase II trial, including significant clinical benefit for patients with brain metastases. Finally, trastuzumab-deruxtecan, zenocutuzumab, and poziotinib demonstrated benefit in phase II trials with the most robust overall response rate (62.0%) and median duration of response (18.2 months) observed for trastuzumab-deruxtecan among heavily pretreated patients.

CONCLUSION

Tucatinib plus trastuzumab and capecitabine significantly prolongs OS, and promising preliminary response outcomes for trastuzumab-deruxtecan suggest that sequencing of these regimens following second-line therapy is reasonable.

Trastuzumab deruxtecan for HER2+ advanced breast cancer

Trastuzumab deruxtecan (T-DXd, DS-8201), an anti-HER2 antibody-drug conjugate, has shown significant clinical benefits in HER2+ metastatic breast cancer patients. In the phase 2 DESTINY-Breast01 trial, T-DXd demonstrated an objective response of 60.9% and median progression-free survival of 16.4 months, laying the foundation for accelerated approval in HER2+ metastatic breast cancer patients who have received two or more prior anti-HER2-based regimens in the metastatic setting. Moreover, T-DXd exhibited promising antitumor efficacy against HER2-low-expressing metastatic breast cancer. Its distinctive side effect was pneumonitis, with a 13.6% incidence. It is approved in the US with boxed warnings for interstitial lung disease and embryo-fetal toxicity. This review focuses on preclinical, pharmacokinetic and pharmacodynamic data on T-DXd and clinical evidence of its antitumor activity (both as monotherapy and in combination) and tolerability in metastatic breast cancer.

Spotlight on Trastuzumab Deruxtecan (DS-8201,T-DXd) for HER2 Mutation Positive Non-Small Cell Lung Cancer

Human epidermal growth factor receptor 2 (HER2) is a proto-oncogene that, when mutated or overexpressed, plays an important role in oncogenesis. The landscape of HER2-positive breast cancer has changed dramatically over the past 2 decades with the FDA approval of a growing number of agents (antibodies, tyrosine kinase inhibitors, and antibody-drug conjugates) targeting the HER2 receptor. HER2 inhibition has also been approved for HER2-positive gastric cancer. HER2 is amplified in 9% and mutated in 3% of lung cancer. Historically, HER2-targeted therapy for lung cancer with trastuzumab, pertuzumab, and trastuzumab emtansine has failed to demonstrate a survival benefit. Trastuzumab deruxtecan (T-DXd) is a novel antibody–drug conjugate with a tetrapeptide linker, which delivers a topoisomerase I inhibitor with a drug-to-antibody ratio of 7~8. The potency of the active payload, as well as its significant bystander effect, resulted in significant anti-tumor activity. The DESTINY-Lung01 trial evaluated T-DXd in HER2-positive non-squamous non-small cell lung cancer (NSCLC) and reported a progression-free survival of 14 months in HER2-mutated NSCLC, earning its breakthrough designation by the FDA. In this review, we will discuss the structural characteristics, pharmacodynamics, and pharmacokinetics of T-DXd. We will also shed light on the preclinical and ongoing clinical trials of T-DXd along with future directions in the management of HER2 positive lung cancer.

New Therapeutic Strategies in Advanced Nonoperable or Metastatic HER2-positive Breast Cancer

Despite therapeutic gains in the treatment of HER2-positive (HER2: human epidermal growth factor receptor 2) advanced/metastatic breast cancer, there remains an urgent need for more effective treatment options. At present, there is no definitive approved standard therapy beyond second-line treatment. One of the major challenges is overcoming treatment resistance. Depending on the underlying resistance mechanism, different strategies are being pursued for new innovative treatment concepts in HER2-positive breast cancer. Specifically designed antibodies for targeted therapy are one important focus to successfully meet these challenges. Trastuzumab deruxtecan (T-DXd, DS-8201a), an optimised antibody drug conjugate (ADC) is in clinical trials, showing promising outcomes in patients with advanced, nonoperable or metastatic HER2-positive breast cancer who had already undergone intensive prior treatment. Based on this data, T-DXd has already been approved in the US and Japan for HER2-positive advanced nonoperable and metastatic breast cancer - in the US after at least two prior anti-HER2 targeted treatment lines and in Japan after prior chemotherapy. T-DXd represents successful "antibody engineering". Since the beginning of the year, T-DXd has also been approved in Europe as monotherapy for inoperable or metastatic HER2-positive breast cancer in patients who are pretreated with at least two anti-HER2 directed therapies. This paper presents strategies for improving treatment options in advanced nonoperable and metastatic HER2-positive breast cancer, with the development of T-DXd as an example.

Trastuzumab deruxtecan for the treatment of patients with HER2-positive gastric cancer

Trastuzumab deruxtecan (T-DXd) is a novel anti-human epidermal growth factor receptor 2 (HER2) antibody–drug conjugate composed of a monoclonal anti-HER2 antibody and a topoisomerase I inhibitor, DX-8951 derivative (an exatecan derivative). T-DXd showed potential anti-tumor activities in HER2-positive gastric cancer cell lines and xenograft models. In the randomized, phase II trial DESTINY-Gastric01, T-DXd demonstrated a significantly higher objective response rate as a primary endpoint and a longer overall survival as a secondary endpoint in patients with pretreated HER2-positive advanced gastric cancer (AGC). Although adverse events caused by T-DXd were generally manageable, approximately 10% of patients experienced treatment-related interstitial lung disease. Based on the results of the DESTINY-Gastric01 trial, T-DXd was approved for HER2-positive pretreated AGC in Japan. This study reviews the preclinical and clinical data of T-DXd for treating HER2-positive gastric cancer.

Trastuzumab-deruxtecan: an investigational agent for the treatment of HER2-positive breast cancer

INTRODUCTION

The prognosis of patients with HER2-positive breast cancer was dramatically changed by the introduction of targeted therapies. With trastuzumab, pertuzumab, and T-DM1 widely used as (neo)adjuvant therapy today, novel treatment options are required to optimize treatment of HER2-positive metastatic disease. Trastuzumab-deruxtecan is an antibody-drug conjugate (ADC) consisting of a monoclonal humanized immunoglobulin G1 antibody, a linker molecule, and the exatecan derivative DXd. T-DXd has a higher drug to antibody ratio compared with T-DM1; in addition, membrane permeability of DXd is high, resulting in an increased bystander effect. Results from early clinical development suggest a clinically relevant activity of T-DXd in heavily pretreated patients with HER2-positive metastatic breast cancer progressing on T-DM1. Interstitial lung disease was a side-effect requiring special attention and was observed in approximately 13% of patients.

AREAS COVERED

This article reviews preclinical and clinical data on T-DXd. A systematic literature search was performed to identify relevant publications. The search included original research articles, abstracts from major conferences, and reviews and was limited to English-language publications.

EXPERT OPINION

T-DXd is an efficacious and tolerable drug and harbors promise as a key addition to the therapeutic field in HER2-positive breast cancer.