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Trastuzumab deruxtecan (Enhertu ® ) is a human epidermal growth factor receptor type 2 (HER2)-directed antibody-drug conjugate that is approved in several countries globally for adults with advanced HER2-positive gastric or gastro-oesophageal junction (GOJ) adenocarcinoma who have received a prior trastuzumab-based regime. In the phase II DESTINY-Gastric01 trial, intravenous trastuzumab deruxtecan was significantly more effective than standard chemotherapy (physician's choice of intravenous irinotecan or paclitaxel) in achieving objective response and improving overall survival in Japanese or South Korean adults with advanced HER2-positive gastric or GOJ adenocarcinoma who had received two or more previous therapies. In the phase II DESTINY-Gastric02 trial, trastuzumab deruxtecan was able to induce durable response in adults from the USA or Europe with unresectable or metastatic HER2-positive gastric or GOJ adenocarcinoma. Trastuzumab deruxtecan was generally tolerable in these patients; the most common adverse events included nausea, neutropenia, fatigue and decreased appetite. Trastuzumab deruxtecan carries regulatory warnings (including boxed warnings in the USA) for interstitial lung disease/pneumonitis and embryo-foetal toxicity. Current evidence indicates that trastuzumab deruxtecan is an effective treatment option, and is generally tolerable, in previously treated adults with advanced HER2-positive gastric or GOJ adenocarcinoma., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Trastuzumab emtansine and trastuzumab deruxtecan are widely used in breast cancer and other solid tumor malignancies. Thrombocytopenia is a common adverse event associated with the use of these agents that can lead to a treatment delay, reduction in dose intensity, and discontinuation. The role of thrombopoietin receptor agonists (TPO-RA) remains unknown in this setting. We report a case series of 6 individuals with breast cancer that experienced dose-reductions and therapy delays due to thrombocytopenia secondary to trastuzumab emtansine or trastuzumab deruxtecan therapy and received intervention with TPO-RA. All 6 were able to resume therapy with TPO-RA support., (© The Author(s) 2023. Published by Oxford University Press.)

Trastuzumab deruxtecan (Enhertu ® ) is a human epidermal growth factor receptor 2 (HER2)-targeted antibody-drug conjugate approved in several countries, including the USA and those of the EU, for adults with unresectable or metastatic HER2-positive breast cancer who have previously received at least one prior anti-HER2-based regimen. In a pivotal phase 3 trial in this setting, intravenous trastuzumab deruxtecan demonstrated prolonged progression-free survival compared with trastuzumab emtansine (previously the recommended second-line therapy in this indication). Trastuzumab deruxtecan had a generally manageable safety and tolerability profile. Common treatment-related adverse events included haematological and gastrointestinal disorders. Interstitial lung disease (ILD)/pneumonitis is associated with a regulatory warning and requires careful monitoring. In conclusion, trastuzumab deruxtecan is a valuable new treatment option for HER2-positive breast cancer, having been shown to be effective with a generally manageable safety and tolerability profile in adults with unresectable or metastatic disease who have received one or more prior anti-HER2-based regimens., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Antibody-drug conjugates have transformed the treatment of HER2+ breast and other cancers. Unfortunately, the CNS remains a sanctuary site for many such patients in part due to poor macromolecule penetration across the blood-brain tumor barrier. Trastuzumab deruxtecan (T-DXd), a high-payload antibody-drug conjugate, was recently found to improve progression-free survival in HER2+ breast cancer patients versus prior-generation trastuzumab emtansine, prompting us to evaluate CNS activity in a woman with brain-only metastatic disease. T-DXd achieved complete response despite heavy pretreatment. Three persistent, previously-irradiated lesions were biopsy-proven to represent treatment effect. Subsequent recurrence occurred upon treatment holiday; partial response was observed with rechallenge. This case suggests T-DXd is active in HER2+ breast cancer brain metastases and supports further prospective evaluation.

The choice of the anti-HER2 agent depends on country-specific availability, the specific, previously administered anti-HER2 therapy and the relapse-free interval, although there is not much published data on the use of lapatinib after progression on pertuzumab and/or T-DM1. The aim of this research is to determine efficacy of lapatinib in this setting. This research included 111 patients with metastatic HER2 positive breast cancer who received lapatinib with capecitabine at The Oncology Institute of Vojvodina. Lapatinib was given to 83 patients after trastuzumab without prior exposure to pertuzumab or T-DM1 while 28 patients received lapatinib after prior exposure to trastuzumab, pertuzumab and/or T-DM1. In order to determine efficacy of lapatinib in both groups, we measured progression free survival (PFS) and overall survival (OS), as well as by subsets: hormonal status (ER-positive and/or PR-positive tumours versus ER-negative and PR-negative tumours), the number of positive axillary lymph nodes (four or more positive axillary lymph nodes versus less than four positive axillary lymph nodes), marker of proliferation (Ki-67 ≥ 30 versus Ki-67 < 30), disease free interval (metastatic recurrence ≤ 1 year after initial diagnosis versus metastatic recurrence > 1 year after initial diagnosis or de novo metastatic disease. Median PFS was 5.6 months (95% CI 4.6-6.6) in the group of patients who received lapatinib after prior exposure to trastuzumab, pertuzumab and/or T-DM 1 and 7.4 months (95% CI 6.1-10.2) in the group of patients who received lapatinib after trastuzumab (HR, 0.79; 95% CI 0.61-0.98; P = 0.09). The patients with negative prognostic factors such as hormone receptor negativity, more than four positive axillary lymph nodes, marker of proliferation Ki 67 ≥ 30 and metastatic recurrence ≤ 1 year after initial diagnosis, had a similar PFS, regardless of receiving lapatinib after prior exposure to trastuzumab, pertuzumab and/or T-DM1 or without prior exposure. Median OS was 10.1 months (95% CI 8.6-NR) in the group that received lapatinib after exposure to trastuzumab, pertuzumab and/or T-DM1 and 16.3 months (95% CI 14.4-20.2) in the group of patients who received lapatinib after trastuzumab (HR, 0.76; 95% CI, 0.59-0.94; P = 0.04). Patients with negative prognostic factors such as hormone receptor negativity, more than four positive axillary lymph nodes and marker of proliferation Ki 67 ≥ 30, had no distinctly worse OS, regardless of receiving lapatinib after prior exposure to trastuzumab, pertuzumab and/or T-DM1 or without prior exposure. Lapatinib with capecitabine is an effective therapeutic option, especially in patients with negative prognostic factors, who have received prior chemotherapy, trastuzumab, pertuzumab, T-DM1 and remains an acceptable option for HER2 positive metastatic breast cancer until the novel drugs are approved in developing countries.

In DESTINY-Breast 03, Trastuzumab Deruxtecan, a HER2-specific antibody-drug conjugate, proved superior to T-DM1 in patients with HER2+ metastatic breast cancer progressing on taxane and trastuzumab. 1 This study supported its recent approval as second-line therapy in HER2+ metastatic breast cancer., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

With three clinically approved antibody-drug conjugates targeting HER2, this target is clearly identified to be of interest in oncology. Moreover, the advent of new bioconjugation technologies producing site-specific homogenous conjugates led to the opportunity of developing new medicines linking antibodies and payloads. Here, a new relevant HER2-targeting ADC was obtained by the conjugation of monomethyl auristatin E onto trastuzumab using McSAF Inside bioconjugation technology. The antibody-drug conjugate formed presented an average drug-to-antibody ratio of 4 with a high homogeneity and an excellent stability especially when incubated with human serum albumin or in human plasma. Moreover, it demonstrated a strong efficacy in an HER2 xenograft tumor model in mice, superior to the clinically approved antibody-drug conjugate ado-trastuzumab emtansine, with a complete tumor regression observed both macroscopically and microscopically demonstrating its therapeutic potential.

Background: Breast cancer Auger electron therapy is a growing field of study in radioimmunotherapy and oncology research. Trastuzumab, a high affinity-binding monoclonal antibody against HER2/neu is which is over-expressed in breast tumors, is used in radiopharmaceutical development., Objectives: In this work, the lethal effects of 111 In 3+ , 111 In-DTPA-trastuzumab and 111 In-trastuzumab coupled-nuclear localizing sequence peptide ( 111 In-DTPA-NLS-trastuzumab) on malignant cells were studied in vitro., Methods: DTPA-NLS-trastuzumab was prepared using sulfosuccinimidyl-4-(N-maleimidomethyl) cyclohexane-1-carboxylate (sulfo-SMCC) conjugation with NLS peptide in the first step, followed by conjugation with diethylenetriaminepentaacetic acid (DTPA). Both DTPA-trastuzumab and DTPA- NLS-trastuzumab were labeled with 111 In followed by purification and quality control techniques. Sk-Br-3 (a HER2/neu+ cell line), was used in the cell viability assessment assay for 111 In, 111 In-DTPA-trastuzumab and 111 In-DTPA-NLS-trastuzumab (3.7 MBq) at 37 ºC. The cytotoxicity of the three species was studied using MTT and comet assay was utilized DNA damage detection., Results: A significant radiochemical purity for 111 In-DTPA-NLS-trastuzumab (99.36% ± 0.30%, ITLC) at the DTPA:antibody ratio of 6.90 ± 0.34:1, was obtained. Significant cell viability difference was found for 111 In-DTPA-NLS-trastuzumab compared to the other treatments at two-time points. In addition, comet assay demonstrated significant DNA damage at 144 h using 111 In-DTPA- NLS-trastuzumab., Conclusion: The results of cell viability and cell death using MTT assay and comet assay, respectively, demonstrate the NLS-peptide effectively facilitates 111 In-trastuzumab transport into the HER2/neu positive cancer cell nuclei to impose the radiotherapeutic effects of Auger electrons on DNA leading to cell death., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

The emergence of a new tumor entity called HER2-low breast cancer leads us to reconsider therapeutic indications in patients whose tumors were usually considered as luminal or triple negative. The development of antibody-drug conjugates (ADCs) allows using HER2 as a vector of a cytoxic drug with significant clinical efficacy in breast cancer with low HER2 expression. Trastuzumab deruxtecan monotherapy is currently evaluated in phase III trials in HER2-low patients, but also in combination in earlier phase studies. Many ADCs are in development, with highly anticipated results. The toxicities of these various ADCs seem manageable and compatible with prolonged administration. Her2-low breast cancer subtype may benefit from dedicated therapeutic strategies in the next few years., (Copyright © 2021 Société FranÇaise du Cancer. Publié par Elsevier Masson SAS. Tous droits réservés.)

Antibody drug conjugates (ADCs) provide an efficacious and relatively safe means by which chemotherapeutic agents can be specifically targeted to cancer cells. In addition to the selection of antibody targets, ADCs offer a modular design that allows selection of ADC characteristics through the choice of linker chemistries, toxins, and conjugation sites. Many studies have indicated that release of toxins bound to antibodies via noncleavable linker chemistries relies on the internalization and intracellular trafficking of the ADC. While this can make noncleavable ADCs more stable in the serum, it can also result in lower efficacy when their respective targets are not internalized efficiently or are recycled back to the cell surface following internalization. Here, we show that a lysosomally targeted ADC against the protein APLP2 mediates cell killing, both in vitro and in vivo, more effectively than an ADC against Trop2, a protein with less efficient lysosomal targeting. We also engineered a bispecific ADC with one arm targeting HER2 for the purpose of directing the ADC to tumors, and the other arm targeting APLP2, whose purpose is to direct the ADC to lysosomes for toxin release. This proof-of-concept bispecific ADC demonstrates that this technology can be used to shift the intracellular trafficking of a constitutively recycled target by directing one arm of the antibody against a lysosomally delivered protein. Our data also show limitations of this approach and potential future directions for development.

To determine the toxicity and immunogenicity of the HER-2/neu, HLA-A2-restricted peptide E75 in patients with metastatic breast and ovarian cancer, 14 patients were vaccinated with escalating amounts of E75 (100, 500, and 1000 microg) mixed with 250 microg granulocyte macrophage colony-stimulating factor as adjuvant. Each vaccine dose was administered in a total volume of 1.5 ml divided into four intradermal injections and administered weekly for 4 weeks, followed by monthly boosts for a total of 10 injections. Vaccinations were well tolerated without significant toxicity. Blood was drawn before, at 8 weeks, and up to 13-16 months after vaccination for measurement of cellular immunity. Seven of 8 patients tested had significant delayed type hypersensitivity to E75 defined as >5 mm induration. Peripheral blood mononuclear cells from 5 of 9 patients tested proliferated to E75 with a stimulation index of > or = 2.0. Of 8 vaccinated patients tested for induction of a CTL response, 4 responded to stimulation by autologous dendritic cells plus cytokines by eliciting E75-specific lytic activity consistent with the presence of activated/memory cells, 2 others after in vitro stimulation with E75 + interleukin-12 +/- anti-CD152(33KD), whereas 2 others did not respond. Four patients with E75-specific CTLs present specifically recognized E75 on indicator tumors as demonstrated by cold-target inhibition of tumor lysis. These 4 patients showed E75-specific IFN-gamma production. peripheral blood mononuclear cell from 3 of these patients proliferated to E75, but stimulation indices were higher in the prevaccine samples. All 4 of the patients showed DTH responses to E75. These results demonstrate that vaccination with E75+ granulocyte macrophage colony-stimulating factor can induce both peptide-specific IFN-gamma and epitope specific CTLs, which lyse HER-2/neu+ tumors in stage IV patients.