BACKGROUND: Trastuzumab deruxtecan (T-DXd) is approved for human epidermal growth factor receptor 2 (HER2)-positive and HER2-low advanced breast cancer (ABC). T-DXd has shown encouraging intracranial activity in HER2-positive ABC patients with stable or active brain metastases (BMs); however, its efficacy in patients with HER2-low ABC with BMs is not well established yet.
METHODS: DEBBRAH is a single-arm, five-cohort, phase II study evaluating T-DXd in patients with central nervous system involvement from HER2-positive and HER2-low ABC. Here, we report results from patients with heavily pretreated HER2-low ABC and active BMs, enrolled in cohorts 2 (n = 6, asymptomatic untreated BMs) and 4 (n = 6, progressing BMs after local therapy). Patients received 5.4 mg/kg T-DXd intravenously once every 21 days. The primary endpoint was intracranial objective response rate per Response Assessment in Neuro-Oncology Brain Metastases (RANO-BM) for both cohorts.
RESULTS: Intracranial objective response rate per RANO-BM was 50.0% [3/6 patients; 95% confidence interval (CI) 11.8% to 88.2%] and 33.3% [2/6 patients; 95% CI 4.3% to 77.7%; P = 0.033 (one-sided)] in cohorts 2 and 4, respectively. All responders had partial responses. Median time to intracranial response was 2.3 months (range, 1.5-4.0 months) and median duration of intracranial response was 7.2 months (range, 2.8-16.8 months). Median progression-free survival per RECIST v.1.1. was 5.4 months (95% CI 4.1-10.0 months). Treatment-emergent adverse events occurred in all patients included (16.7% grade 3). Three patients (25.0%) had grade 1 interstitial lung disease/pneumonitis.
CONCLUSIONS: T-DXd demonstrated promising intracranial activity in pretreated HER2-low ABC patients with active BMs. Further studies are needed to validate these results in larger cohorts. This trial is registered with ClinicalTrials.gov, NCT04420598.

OBJECTIVE: With the wide application of trastuzumab deruxtecan (T-DXd), the survival of HER2-low breast cancer patients is dramatically improved. However, resistance to T-DXd still exists in a subset of patients, and the molecular mechanism remains unclear.
METHODS: An in vivo shRNA lentiviral library functional screening was performed to identify potential circular RNA (crRNA) that mediates T-DXd resistance. RNA pull-down, mass spectrometry, RNA immunoprecipitation, and co-immunoprecipitation assays were conducted to investigate the molecular mechanism. Ferroptosis was detected using C11-BODIPY, Liperfluo, FerroOrange staining, glutathione quantification, malondialdehyde quantification, and transmission electron microscopy. Molecular docking, virtual screening, and patient-derived xenograft (PDX) models were used to validate therapeutic agents.
RESULTS: VDAC3-derived crRNA (crVDAC3) ranked first in functional shRNA library screening. Knockdown of crVDAC3 increased the sensitivity of HER2-low breast cancer cells to T-DXd treatment. Further mechanistic research revealed that crVDAC3 specifically binds to HSPB1 protein and inhibits its ubiquitination degradation, leading to intracellular accumulation and increased levels of HSPB1 protein. Notably, suppression of crVDAC3 dramatically increases excessive ROS levels and labile iron pool accumulation. Inhibition of crVDAC3 induces ferroptosis in breast cancer cells by reducing HSPB1 expression, thereby mediating T-DXd resistance. Through virtual screening and experimental validation, we identified that paritaprevir could effectively bind to crVDAC3 and prevent its interaction with HSPB1 protein, thereby increasing ubiquitination degradation of HSPB1 protein to overcome T-DXd resistance. Finally, we validated the enhanced therapeutic efficacy of T-DXd by paritaprevir in a HER2-low PDX model.
CONCLUSIONS: This finding reveals the molecular mechanisms underlying T-DXd resistance in HER2-low breast cancer. Our study provides a new strategy to overcome T-DXd resistance by inhibiting the interaction between crVDAC3 and HSPB1 protein.

BACKGROUND: This exploratory pooled analysis investigated the efficacy and safety of trastuzumab deruxtecan (T-DXd) versus comparator treatment in patients with HER2-positive metastatic breast cancer (mBC) with brain metastases (BMs) at baseline, categorized according to previous local treatment.
METHODS: T-DXd data were pooled from DESTINY-Breast01/-02/-03. Comparator data, from patients receiving physician\'s choice therapy and trastuzumab emtansine, were pooled from DESTINY-Breast02 and -03, respectively. Baseline BM status was assessed according to US Food and Drug Administration criteria. Endpoints included intracranial objective response rate (ORR; complete or partial response in brain) per blinded independent central review (BICR) by RECIST v1.1, time to intracranial response, intracranial duration of response (DoR), central nervous system progression-free survival (CNS-PFS) by BICR, overall survival (OS), and safety.
RESULTS: 148 patients who received T-DXd and 83 patients who received comparator treatment had BMs at baseline. In those who were treated with T-DXd, the intracranial ORR of patients with treated/stable and untreated/active BMs was 45.2% and 45.5%, respectively. The median (range) time to intracranial response was 2.8 months (1.1-13.9 months) and 1.5 months (1.2-13.7 months) in patients with treated/stable and untreated/active BMs, respectively. For those with treated/stable BMs, the median (95% CI) intracranial DoR was 12.3 months (9.1-17.9 months), and for those with untreated/active BMs it was 17.5 months (13.6-31.6 months). The median (95% CI) CNS-PFS and OS was 12.3 months (11.1-13.8 months) and not reached (22.1 months-not estimable [NE]) in those with treated/stable BMs, and 18.5 months (13.6-23.3 months) and 30.2 months (21.3 months-NE) in those with untreated/active BMs, respectively. Drug-related TEAEs grade ≥3 were experienced by 43.2% of patients with BMs and 46.4% without BMs with T-DXd.
CONCLUSIONS: T-DXd demonstrated meaningful intracranial efficacy and clinical benefit in OS, with an acceptable and manageable safety profile in patients with HER2-positive mBC with treated/stable and untreated/active BMs.

UNASSIGNED: The third-generation antibody-drug conjugates (ADC), trastuzumab deruxtecan (T-DXd) and sacituzumab govitecan (SG), recently obtained approval for metastatic breast cancer treatment across various subtypes and therapeutic contexts.
UNASSIGNED: This retrospective, multicentric study evaluated real-world tolerability, feasibility and efficacy in a pre-treated, real-world cohort at three major German breast cancer centers.
UNASSIGNED: 125 patients treated with T-DXd or SG from November 2020 to June 2023 were included (T-DXd: 77 patients; SG: 48 patients). The median treatment duration was 6.0 months for T-DXd and 3.5 months for SG therapy, with a median follow-up duration of 10.4 months for T-DXd (95% CI: 8.4-11.6) and 11.8 months for SG (95% CI: 8.0-14.4). Severe neutropenia (CTC ≥ III°) occurred in 33.3% during SG therapy, with a numerical reduction observed following primary, prophylactic use of G-CSF. T-DXd-associated pneumonitis occurred in 8 out of 77 patients (10.4 %). Median progression-free survival (mPFS) was 8.6 months (95% CI: 5.8-12.4) with T-DXd (HER2+: 10.8; HER2-low: 4.7) and 4.9 months (95% CI: 2.8-6.3) with SG (TNBC 4.9; HR+/HER2-: not reached). Median overall survival (OS) was 23.8 months (95% CI: 16.1-not estimable) with T-DXd (HER2+: 27.1; HER2-low: not reached), and 12.4 months (95% CI: 8.7-not estimable) with SG therapy (TNBC: 12.4, HR+/HER2-: not reached). 95.7% of the protocol-specified, therapeutic dose was administered for T-DXd and 89.6% for SG.
UNASSIGNED: Overall, this indicates good feasibility, tolerability, and effectiveness of ADC therapies in the real-world setting.
UNASSIGNED: Trastuzumab-Deruxtecan (T-DXd) und Sacituzumab-Govitecan (SG) sind Antikörper-Wirkstoff-Konjugate (ADCs) der 3. Generation, die vor Kurzem zur Behandlung von metastatischem Brustkrebs über mehrere Subtypen hinweg und in verschiedenen therapeutischen Zusammenhängen zugelassen wurden.
UNASSIGNED: Ziel dieser retrospektiven multizentrischen Studie war es, die Real-World-Daten über die Verträglichkeit, Umsetzbarkeit und Wirksamkeit dieser Wirkstoffe in einer vorbehandelten Real-World-Kohorte in 3 großen deutschen Brustkrebszentren zu bewerten.
UNASSIGNED: Eingeschlossen wurden 125 Patientinnen, die zwischen November 2020 und Juni 2023 mit T-DXd oder SG behandelt wurden (T-DXd: 77 Patientinnen; SG: 48 Patientinnen). Die mediane Behandlungsdauer betrug 6,0 Monate für eine T-DXd- und 3,5 Monate für eine SG-Therapie mit einer medianen Nachbeobachtungszeit von 10,4 Monaten für T-DXd (95%-KI: 8,4–11,6) und 11,8 Monaten für SG (95%-KI: 8,0–14,4). 33,3% der Patientinnen entwickelten eine schwere Neutropenie (CTC ≥ III°) im Verlauf der SG-Therapie, wobei eine numerische Reduktion nach dem primären prophylaktischen Einsatz von G-CSF beobachtet wurde. Bei 8 von 77 Patientinnen (10,4 %) trat eine T-DXd-bedingte Pneumonitis auf. Das mediane progressionsfreie Überleben (mPFÜ) betrug 8,6 Monate (95%-KI: 5,8–12,4) mit T-DXd (HER2+: 10,8; HER2-low: 4,7) und 4,9 Monate (95%-KI: 2,8–6,3) mit SG (TNBC 4,9; HR+/HER2−: nicht erreicht). Das mediane Gesamtüberleben (GÜ) betrug 23,8 Monate (95%-KI: 16,1–nicht schätzbar) mit einer T-DXd-Therapie (HER2+: 27,1; HER2-low: nicht erreicht) und 12,4 Monate (95%-KI: 8,7–nicht schätzbar) mit einer SG-Therapie (TNBC: 12,4, HR+/HER2−: nicht erreicht). Verabreicht wurden 95,7% der im Protokoll vorgegebenen therapeutischen T-DXd-Dosis bzw. 89,6% der vorgegebenen SG-Dosis.
UNASSIGNED: Insgesamt weisen die Daten auf eine gute Umsetzbarkeit, Wirksamkeit und Verträglichkeit von ADC-Therapien in einer realen Umgebung hin.

Therapeutic developments in the targeting of human epidermal growth factor receptor 2 (HER2)-expressing gastric cancer have followed the dramatic success of HER2-expressing breast cancer treatment, which has facilitated the expansion of indications for anti-HER2 agents to include not only conventional HER2-positive breast cancer, but also HER2-low and HER2-ultralow subgroups. The targetability of HER2-low gastric cancer, however, has yet to be established. Hence, further studies are needed to comprehensively understand the clinicopathological features, specific gene alterations, and distinct tumor immune microenvironment of HER2-low gastric cancer and compare them with those for HER2-positive or -negative gastric cancer. Antibody-drug conjugates for HER2 play an important role in making HER2-low gastric cancer targetable. In this context, a deeper understanding of the novel anti-HER2 agents, including antibody-drug conjugates, bispecific T-cell engager antibodies, and a combination of these agents, as well as new forms of immunomodulatory agents are also required. Redefining and re-categorizing HER2 status through not only immunohistochemistry/fluorescence in situ hybridization but also evaluating ERRB2 copy number gain or protein overexpression levels measured using DNA or RNA sequencing might be helpful for identifying populations with HER2-expressing tumors who would ideally benefit from anti-HER2 treatment. The current paper reviewed recent clinical trials, focusing particularly on HER2-low gastric cancer together with basic/translational findings, and discuss perspectives on further therapeutic development in the treatment of this distinct subgroup.

We provide updated results (median follow-up duration: 20.4 months) of a retrospective study on the effectiveness of trastuzumab deruxtecan (T-DXd) in patients with human epidermal growth factor receptor 2-positive (HER2+) breast cancer with brain metastases (BM) and/or leptomeningeal disease (ROSET-BM). Median progression-free survival (PFS) was 14.6 months. Median overall survival (OS) was not reached (NR); 24-month OS rate was 56.0%. Subgroup analysis showed that median PFS was 13.2 months in patients with analytical active BM, 17.5 months in patients with leptomeningeal carcinomatosis (LMC), and NR in patients with analytical stable BM (24-month PFS rates in patients with analytical active BM, LMC, and analytical stable BM were 32.7%, 25.1%, and 60.8%, respectively). Median OS was 27.0 months in patients with analytical active BM and NR in patients with LMC or analytical stable BM (24-month OS rates in patients with analytical active BM, LMC, and analytical stable BM were 52.0%, 61.6%, and 71.6%, respectively). The most common adverse event leading to discontinuation of T-DXd was interstitial lung disease (ILD; 23.1%); median ILD onset time among patients who discontinued T-DXd treatment due to ILD was 5.3 months. T-DXd has promising effectiveness in heavily pre-treated HER2+ metastatic breast cancer patients with BM and LMC. The incidence and median onset time of ILD were similar to those of Japanese subgroups in previous studies.

Breast cancer with brain metastasis accounts for the second largest number of brain metastases among solid malignancies. Despite advances in HER2-targeted therapy, 50% of patients with human epidermal growth factor receptor 2-positive (HER2+) breast cancer develop brain metastases and are associated with poor outcomes. In this article, we report the case of a patient with HER2+ metastatic breast cancer who developed brain metastases, despite experiencing a durable effect on extracranial metastases after treatment with trastuzumab and pertuzumab. The patient exhibited intracranial progression while receiving treatment with trastuzumab deruxtecan monotherapy after secondary brain radiotherapy and multiple lines of therapy with anti-HER2 agents, such as pyrotinib, lapatinib, tucatinib, and ado-trastuzumab emtansine. However, the administration of anlotinib (an antiangiogenesis medication) and trastuzumab deruxtecan resulted in intracranial and extracranial partial response and was linked to manageable side effects. The present case indicates that the combination of anlotinib and trastuzumab deruxtecan may be a promising treatment option for patients with HER2+ breast cancer with brain metastasis. Nevertheless, further studies are warranted to verify the present findings.

Antibody-drug conjugates (ADCs) have demonstrated effectiveness in treating various cancers, particularly exhibiting specificity in targeting human epidermal growth factor receptor 2 (HER2)-positive breast cancer. Recent advancements in phase 3 clinical trials have broadened current understanding of ADCs, especially trastuzumab deruxtecan, in treating other HER2-expressing malignancies. This expansion of knowledge has led to the US Food and Drug Administration\'s approval of trastuzumab deruxtecan for HER2-positive and HER2-low breast cancer, HER2-positive gastric cancer, and HER2-mutant nonsmall cell lung cancer. Concurrent with the increasing use of ADCs in oncology, there is growing concern among health care professionals regarding the rise in the incidence of interstitial lung disease or pneumonitis (ILD/p), which is associated with anti-HER2 ADC therapy. Studies on anti-HER2 ADCs have reported varying ILD/p mortality rates. Consequently, it is crucial to establish guidelines for the diagnosis and management of ILD/p in patients receiving anti-HER2 ADC therapy. To this end, a panel of Chinese experts was convened to formulate a strategic approach for the identification and management of ILD/p in patients treated with anti-HER2 ADC therapy. This report presents the expert panel\'s opinions and recommendations, which are intended to guide the management of ILD/p induced by anti-HER2 ADC therapy in clinical practice.

OBJECTIVE: Emerging data suggest that trastuzumab deruxtecan (T-DXd) is an active treatment for brain metastases from HER2 + breast cancer. We aimed to characterize the activity of T-DXd in the treatment of leptomeningeal metastases (LM) from a range of HER2-altered cancers.
METHODS: We reviewed neuro-oncology clinic records between July 2020 and December 2023 to identify patients who received T-DXd to treat LM.
RESULTS: Of 18 patients identified, 6 had HER2 + breast cancer, 8 had HER2-low/negative breast cancer, 2 had HER2 + gastroesophageal cancer, and 2 had HER2-mutant non-small cell lung cancer (NSCLC). 10/18 (56%) patients had cytologically confirmed LM by CSF cytology or circulating tumor cell (CTC) capture. A partial response (PR) on MRI using the EORTC/RANO-LM Revised-Scorecard occurred in 4/6 (67%) patients with HER2 + breast LM, 2/8 (25%) patients with HER2-low/negative breast cancer, and 0/4 (0%) patients with HER2 + gastroesophageal cancer or HER2-mutant NSCLC. Median overall survival after initiating T-DXd was 5.8 months. Survival after initiating T-DXd was numerically longer for HER2 + breast cancer patients compared with HER2-low/negative breast and HER2-altered non-breast cancer patients (13.9 months vs. 5.2 months and 4.6 months, respectively). Landmark analysis showed that patients with radiologic LM response to T-DXd by 2.5 months had longer survival than non-responders (14.2 months vs. 2.6 months, HR 0.18, 95% CI 0.05-0.63, p < 0.05), and landmark analyses at 3.5 and 4.5 months after starting T-DXd showed a similar but nonsignificant trend.
CONCLUSIONS: T-DXd induces LM responses in a subset of patients, and such responses may be associated with prolongation of survival. Prospective trials are needed to clarify the role of T-DXd in treating LM and which patients are most likely to benefit.

Human epidermal growth factor 2 (HER2)-positive breast cancer (BC) represents nearly 20% of all breast tumors. Historically, these patients had a high rate of relapse and dismal prognosis. The advent of HER2-targeting monoclonal antibodies such as trastuzumab followed by pertuzumab had improved the prognosis of HER2-positive metastatic BC. More recently, antibody-drug conjugates (ADCs) are now reshaping the treatment paradigm of solid tumors, especially breast cancer. Tratsuzumab emtansine (T-DM1) was one of the first ADC developed in oncology and was approved for the management of HER2-positive metastatic BC. In a head-to-head comparison, trastuzumab deruxtecan (T-DXd) defeated T-DM1 as a second-line treatment. The efficacy of ADCs is counterbalanced by the appearance of acquired resistance to these agents. In this paper, we summarize the mechanisms of action and resistance of T-DM1 and T-DXd, as well as their clinical efficacy. Additionally, we also discuss potential strategies for addressing resistance to ADC.