Ado-Trastuzumab Emtansine Targets Hepatocytes Via Human Epidermal Growth Factor Receptor 2 to Induce Hepatotoxicity

Biomarkers for Antibody-Drug Conjugates in Solid Tumors

The clinical development and then the progressive entry in clinical practice of antibody-drug conjugates (ADC) have marked a transformative advancement in the overall cancer treatment. ADCs have been extensively tested for a large number of tumors, reporting heterogeneous clinical efficacy and safety results. In some diseases, the advent of ADCs has yielded significant changes in the prognostic trajectory, portending an improvement of the survival and/or quality of life. ADCs are targeted agents, capable of delivering highly cytotoxic payloads selectively to antigen-expressing cancer cells. As such, they have been intended as perfect "bullets" to enable the promise of precision medicine, toward high-efficacy and limited-toxicity treatment options. However, only some approved ADCs are intended for the use in biomarker-selected patient populations, restricting potentially the opportunity to be more precise. Yet, key characteristics of modern ADCs might allow the activity of ADCs in tumors with heterogeneous or low expression of cancer antigens, resulting in a clinical activity that could sublimate the classic paradigm of a drug-to-target perfect match. In our review, we portrayed the current landscape of approved ADCs, reporting data of activity as related to the expression of the cancer antigens, and elucidating possible determinants of the safety and efficacy, including when used in a therapeutic sequence.

Comparing the difference of adverse events with HER2 inhibitors: a study of the FDA adverse event reporting system (FAERS)

Aim and background: This study attempted to identify similarities and differences in adverse events (AEs) between human epidermal growth factor receptor 2 (HER2) inhibitors, especially those related to hemorrhagic events and nervous system disorders. Methods: This study summarized the types, frequencies, and system organ classes (SOCs) of AEs of HER2 inhibitors. The US Food and Drug Administration Adverse Event Reporting System (FAERS) data from January 2004 through March 2022 was collected and analyzed. Disproportionality analyses were conducted to detect AEs signals for every HER2 inhibitor. The chi-square test, Wilcoxon test, and descriptive analysis were used to compare the differences of AEs for specific SOCs or drugs. Results: A total of 47,899 AE reports were obtained for eight HER2 inhibitors. Trastuzumab-related AEs were reported in the highest number and combination of regimens. In monotherapy, trastuzumab had the highest reported rate of cardiac disorders-related AEs (24.0%). However, small-molecule drugs exceeded other drugs in the reported rates of AEs related to gastrointestinal disorders, metabolism and nutrition disorders. The highest reported rates of respiratory disorders (47.3%) and hematologic disorders (22.4%) were associated with treatment with trastuzumab deruxtecan (T-DXd). Patients treated with trastuzumab emtansine (TDM-1) had the highest reported rate (7.28%) of hemorrhagic events, especially intracranial haemorrhage events. In addition, patients treated with TDM-1 with concomitant thrombocytopenia were likely to experience hemorrhagic events compared to other HER2 inhibitors (p < 0.001). The median time to onset of intracranial haemorrhage associated with trastuzumab (0.5 months) and TDM-1 (0.75 months) was short. However, there was no significant difference in median time to onset intracranial haemorrhage between patients in different age groups or with different outcomes. Disproportionality analysis results reveal that cerebral haemorrhage is a positive signal associated with T-DXd and TDM-1. In addition, tucatinib was the drug with the highest rate of reported nervous system disorders (31.38%). Memory impairment (83 cases) is a positive signal for tucatinib. Conclusion: The types and reporting rates of AEs associated with different HER2 inhibitors vary across multiple systems. In addition, hemorrhagic events concomitant with TDM-1 treatment and nervous system disorders concomitant with tucatinib treatment may be worthy of attention.

Toxicity profile of antibody-drug conjugates in breast cancer: practical considerations

Antibody-drug conjugates (ADCs) represent a novel and evolving class of antineoplastic agents, constituted by monoclonal antibody linked to biologically active drugs, delivering cytotoxic compounds at the tumor site, reducing the likelihood of systemic exposure and toxicity. They are generally well tolerated, nevertheless some predictable adverse reactions need careful monitoring and timely approach. These include neutropenia, nausea and vomiting, alopecia, diarrhea, left ventricular dysfunction, ILD/pneumonitis. The mechanisms leading to drug-associated toxicities are summarized, and prophylaxis protocols and appropriate management strategies are proposed, based on current literature. This review aims to collect the most updated evidence on toxicities potentially occurring during breast cancer treatment with approved or under clinical investigation (advanced stage) ADCs. A focus is dedicated to monitoring protocols and clinical management, aimed at preventing and/or promptly address relevant problems, in order to avoid premature discontinuation or improper dose reduction.

Atezolizumab Induces Necroptosis and Contributes to Hepatotoxicity of Human Hepatocytes

Atezolizumab is an immune checkpoint inhibitor (ICI) targeting PD-L1 for treatment of solid malignancies. Immune checkpoints control the immune tolerance, and the adverse events such as hepatotoxicity induced by ICIs are often considered as an immune-related adverse event (irAE). However, PD-L1 is also highly expressed in normal tissues, e.g., hepatocytes. It is still not clear whether, targeting PD-L1 on hepatocytes, the atezolizumab may cause damage to liver cells contributing to hepatotoxicity. Here, we reveal a novel mechanism by which the atezolizumab induces hepatotoxicity in human hepatocytes. We find that the atezolizumab treatment increases a release of LDH in the cell culture medium of human hepatocytes (human primary hepatocytes and THLE-2 cells), decreases cell viability, and inhibits the THLE-2 and THLE-3 cell growth. We demonstrate that both the atezolizumab and the conditioned medium (T-CM) derived from activated T cells can induce necroptosis of the THLE-2 cells, which is underscored by the fact that the atezolizumab and T-CM enhance the phosphorylation of RIP3 and MLKL proteins. Furthermore, we also show that necrostatin-1, a necrosome inhibitor, decreases the amount of phosphorylated RIP3 induced by the atezolizumab, resulting in a reduced LDH release in the culture media of the THLE-2 cells. This finding is further supported by the data that GSK872 (a RIP3 inhibitor) significantly reduced the atezolizumab-induced LDH release. Taken together, our data indicate that the atezolizumab induces PD-L1-mediated necrosome formation, contributing to hepatotoxicity in PD-L1⁺-human hepatocytes. This study provides the molecular basis of the atezolizumab-induced hepatotoxicity and opens a new avenue for developing a novel therapeutic approach to reducing hepatotoxicity induced by ICIs.

Mechanisms of ADC Toxicity and Strategies to Increase ADC Tolerability

Anti-cancer antibody-drug conjugates (ADCs) aim to expand the therapeutic index of traditional chemotherapy by employing the targeting specificity of monoclonal antibodies (mAbs) to increase the efficiency of the delivery of potent cytotoxic agents to malignant cells. In the past three years, the number of ADCs approved by the Food and Drug Administration (FDA) has tripled. Although several ADCs have demonstrated sufficient efficacy and safety to warrant FDA approval, the clinical use of all ADCs leads to substantial toxicity in treated patients, and many ADCs have failed during clinical development due to their unacceptable toxicity profiles. Analysis of the clinical data has demonstrated that dose-limiting toxicities (DLTs) are often shared by different ADCs that deliver the same cytotoxic payload, independent of the antigen that is targeted and/or the type of cancer that is treated. DLTs are commonly associated with cells and tissues that do not express the targeted antigen (i.e., off-target toxicity), and often limit ADC dosage to levels below those required for optimal anti-cancer effects. In this manuscript, we review the fundamental mechanisms contributing to ADC toxicity, we summarize common ADC treatment-related adverse events, and we discuss several approaches to mitigating ADC toxicity.

An Enzymatically Cleavable Tripeptide Linker for Maximizing the Therapeutic Index of Antibody-Drug Conjugates

Valine-citrulline is a protease-cleavable linker commonly used in many drug delivery systems, including antibody-drug conjugates (ADC) for cancer therapy. However, its suboptimal in vivo stability can cause various adverse effects such as neutropenia and hepatotoxicity, leading to dose delays or treatment discontinuation. Here, we report that glutamic acid-glycine-citrulline (EGCit) linkers have the potential to solve this clinical issue without compromising the ability of traceless drug release and ADC therapeutic efficacy. We demonstrate that our EGCit ADC resists neutrophil protease-mediated degradation and spares differentiating human neutrophils. Notably, our anti-HER2 ADC shows almost no sign of blood and liver toxicity in healthy mice at 80 mg kg-1. In contrast, at the same dose level, the FDA-approved anti-HER2 ADCs Kadcyla and Enhertu show increased levels of serum alanine aminotransferase and aspartate aminotransferase and morphologic changes in liver tissues. Our EGCit conjugates also exert greater antitumor efficacy in multiple xenograft tumor models compared with Kadcyla and Enhertu. This linker technology could substantially broaden the therapeutic windows of ADCs and other drug delivery agents, providing clinical options with improved efficacy and safety.

Targeted therapy for breast cancer: An overview of drug classes and outcomes

The last 25 years have seen significant growth in new therapeutic options for breast cancer, termed targeted therapies based on their ability to block specific pathways known to drive breast tumor growth and survival. Introduction of these drugs has been made possible through advances in the understanding of breast cancer biology. While the promise of targeted therapy for breast cancer has been clear for some time, the experience of the clinical use of multiple drugs and drug classes allows us to now present a summary and perspective as to the success and impact of this endeavor. Here we will review breast cancer targeted therapeutics in clinical use. We will provide the rationale for their indications and summarize clinical data in patients with different breast cancer subtypes, their impact on breast cancer progression and survival and their major adverse effects. The focus of this review will be on the development that has occurred within classes of targeted therapies and subsequent impact on breast cancer patient outcomes. We will conclude with a perspective on the role of targeted therapy in breast cancer treatment and highlight future areas of development.

Nanotheranostics for Image-Guided Cancer Treatment

Image-guided nanotheranostics have the potential to represent a new paradigm in the treatment of cancer. Recent developments in modern imaging and nanoparticle design offer an answer to many of the issues associated with conventional chemotherapy, including their indiscriminate side effects and susceptibility to drug resistance. Imaging is one of the tools best poised to enable tailoring of cancer therapies. The field of image-guided nanotheranostics has the potential to harness the precision of modern imaging techniques and use this to direct, dictate, and follow site-specific drug delivery, all of which can be used to further tailor cancer therapies on both the individual and population level. The use of image-guided drug delivery has exploded in preclinical and clinical trials although the clinical translation is incipient. This review will focus on traditional mechanisms of targeted drug delivery in cancer, including the use of molecular targeting, as well as the foundations of designing nanotheranostics, with a focus on current clinical applications of nanotheranostics in cancer. A variety of specially engineered and targeted drug carriers, along with strategies of labeling nanoparticles to endow detectability in different imaging modalities will be reviewed. It will also introduce newer concepts of image-guided drug delivery, which may circumvent many of the issues seen with other techniques. Finally, we will review the current barriers to clinical translation of image-guided nanotheranostics and how these may be overcome.

Antibody-Drug Conjugate Targets, Drugs and Linkers

Antibody-drug conjugates offer the possibility of directing powerful cytotoxic agents to a malignant tumor while sparing normal tissue. The challenge is to select an antibody target expressed exclusively or at highly elevated levels on the surface of tumor cells and either not all or at low levels on normal cells. The current review explores 78 targets that have been explored as antibody-drug conjugate targets. Some of these targets have been abandoned, 9 or more are the targets of FDA-approved drugs, and most remain active clinical interest. Antibody-drug conjugates require potent cytotoxic drug payloads, several of these small molecules are discussed, as are the linkers between the protein component and small molecule components of the conjugates. Finally, conclusions regarding the elements for the successful antibody-drug conjugate are discussed.

Target-responsive subcellular catabolism analysis for early-stage antibody-drug conjugates screening and assessment

Events including antibody‒antigen affinity, internalization, trafficking and lysosomal proteolysis combinatorially determine the efficiency of antibody-drug conjugate (ADC) catabolism and hence the toxicity. Nevertheless, an approach that conveniently identifies proteins requisite for payload release and the ensuing toxicity for mechanistic studies and quality assessment is lacking. Considering the plethora of ADC candidates under development, we developed a target-responsive subcellular catabolism (TARSC) approach that examines ADC catabolism and probes changes in response to targeted interferences of proteins of interest. We firstly applied TARSC to study the commercial T-DM1 and the biosimilar. We recorded unequivocal catabolic behaviors regardless of the absence and presence of the targeted interferences. Their negligible differences in TARSC profiles agreed with their undifferentiated anti-tumoral efficacy according to further in vitro viability and in vivo tumor growth assays, highlighting TARSC analysis as a useful tool for biosimilarity assessment and functional dissection of proteins requisite for ADC catabolism. Additionally, we employed TARSC to investigate the catabolic behavior of a new trastuzumab-toxin conjugate. Collectively, TARSC can not only characterize ADC catabolism at (sub)cellular level but also comprehensively determine which protein targets affect payload release and therapeutic outcomes. Future use of TARSC is thus anticipated in early-stage screening, quality assessment and mechanistic investigations of ADCs.

Trastuzumab does not bind rat or mouse ErbB2/neu: implications for selection of non-clinical safety models for trastuzumab-based therapeutics

PURPOSE

Assessment of non-clinical safety signals relies on understanding species selectivity of antibodies. This is particularly important with antibody-drug conjugates, where it is key to determine target-dependent versus target-independent toxicity. Although it appears to be widely accepted that trastuzumab does not bind mouse or rat HER2/ErbB2/neu, numerous investigators continue to use mouse models to investigate safety signals of trastuzumab and trastuzumab emtansine (T-DM1). We, therefore, conducted a broad array of both binding and biologic studies to demonstrate selectivity of trastuzumab for human HER2 versus mouse/rat neu.

METHODS

Binding of anti-neu and anti-HER2 antibodies was assessed by ELISA, FACS, IHC, Scatchard, and immunoblot methods in human, rat, and mouse cell lines. In human hepatocytes, T-DM1 uptake and catabolism were measured by LC-MS/MS; cell viability changes were determined using CellTiter-Glo.

RESULTS

Our data demonstrate, using different binding methods, lack of trastuzumab binding to rat or mouse neu. Structural studies show important amino acid differences in the trastuzumab-HER2 binding interface between mouse/rat and human HER2 ECD. Substitution of these rodent amino acid residues into human HER2 abolish binding of trastuzumab. Cell viability changes, uptake, and catabolism of T-DM1 versus a DM1 non-targeted control ADC were comparable, indicating target-independent effects of the DM1-containing ADCs. Moreover, trastuzumab binding to human or mouse hepatocytes was not detected.

CONCLUSIONS

These data, in total, demonstrate that trastuzumab, and by extension T-DM1, do not bind rat or mouse neu, underscoring the importance of species selection for safety studies investigating trastuzumab or trastuzumab-based therapeutics.

Recombinant immunotoxins development for HER2-based targeted cancer therapies

Understanding the molecular mechanisms of cancer biology introduces targeted therapy as a complementary method along with other conventional therapies. Recombinant immunotoxins are tumor specific antibodies that their recognizing fragment is utilized for delivering modified toxins into tumor cells. These molecules have been considered as a targeted strategy in the treatment of human cancers. HER2 tumor biomarker is a transmembrane tyrosine kinase receptor that can be used for targeted therapies in the forms of anti-HER2 monoclonal antibodies, antibody-drug conjugates and immunotoxins. There have been many studies on HER2-based immunotoxins in recent years, however, little progress has been made in the clinical field which demanded more improvements. Here, we summarized the HER2 signaling and it's targeting using immunotherapeutic agents in human cancers. Then, we specifically reviewed anti-HER2 immunotoxins, and their strengths and drawbacks to highlight their promising clinical impact.

First-in-Human, Phase 1 Dose-Escalation Study of Biparatopic Anti-HER2 Antibody-Drug Conjugate MEDI4276 in Patients with HER2-positive Advanced Breast or Gastric Cancer

MEDI4276 is a biparatopic tetravalent antibody targeting two nonoverlapping epitopes in subdomains 2 and 4 of the HER2 ecto-domain, with site-specific conjugation to a tubulysin-based microtubule inhibitor payload. MEDI4276 demonstrates enhanced cellular internalization and cytolysis of HER2-positive tumor cells in vitro This was a first-in-human, dose-escalation clinical trial in patients with HER2-positive advanced or metastatic breast cancer or gastric cancer. MEDI4276 doses escalated from 0.05 to 0.9 mg/kg (60- to 90-minute intravenous infusion every 3 weeks). Primary endpoints were safety and tolerability; secondary endpoints included antitumor activity (objective response, progression-free survival, and overall survival), pharmacokinetics, and immunogenicity. Forty-seven patients (median age 59 years; median of seven prior treatment regimens) were treated. The maximum tolerated dose was exceeded at 0.9 mg/kg with two patients experiencing dose-limiting toxicities (DLTs) of grade 3 liver function test (LFT) increases, one of whom also had grade 3 diarrhea, which resolved. Two additional patients reported DLTs of grade 3 LFT increases at lower doses (0.4 and 0.6 mg/kg). The most common (all grade) drug-related adverse events (AEs) were nausea (59.6%), fatigue (44.7%), aspartate aminotransferase (AST) increased (42.6%), and vomiting (38.3%). The most common grade 3/4 drug-related AE was AST increased (21.3%). Five patients had drug-related AEs leading to treatment discontinuation. In the as-treated population, there was one complete response (0.5 mg/kg; breast cancer), and two partial responses (0.6 and 0.75 mg/kg; breast cancer)-all had prior trastuzumab, pertuzumab, and ado-trastuzumab emtansine (T-DM1). MEDI4276 has demonstrable clinical activity but displays intolerable toxicity at doses >0.3 mg/kg.

HER-2 Neu gene: A valuable therapeutic target in metastatic mucoepidermoid carcinoma

INTRODUCTION

Salivary gland neoplasms (SGNs) respond poorly to the traditional chemotherapy agents limiting the availability of systemic treatment options in the metastatic setting. The recent identification of actionable molecular targets in SGNs has led to the evaluation of targeted therapies in non-approved advanced SGNs.

CASE REPORT

We present the case of an elderly male with HER-2 Neu overexpressing metastatic mucoepidermoid carcinoma (MEC) who demonstrated a prompt and sustained disease response to targeted therapies directed against HER-2 Neu with long survival interrupted by hepatoxicity to Trastuzumab emtansine (TDM-1) treatment.Management and Outcome: The patient was started on Trastuzumab and Pertuzumab on a clinical trial and resulted in an objective improvement sustained over 3 years. Following the disease progression, TDM-1 was started with a response until the patient developed severe hepatotoxicity as an adverse effect of TDM-1 therapy resulting in its discontinuation. Close follow-up post-treatment-discontinuation demonstrated continued clinical improvement until 6 months, when the patient developed brain metastasis. He passed away a few months later in hospice care.

DISCUSSION

The metastatic MEC in our patient overexpressed HER-2 Neu. Owing to Trastuzumab and Pertuzumab response, Trastuzumab emtansine (TDM-1) was initiated on a compassionate basis which further extended the survival but had to be terminated owing to adverse effects. Given the paucity of data on targeted therapies in the treatment of metastatic SGNs and the safety, tolerability, and efficacy of TDM-1 therapy among the elderly, further studies are warranted to answer these important questions and to identify eligible patients for this novel treatment option.

Mechanisms contributing to ado-trastuzumab emtansine-induced toxicities: a gateway to better understanding of ADC-associated toxicities

In order to improve the safety of novel therapeutic drugs, better understanding of the mechanisms of action is important. Ado-trastuzumab emtansine (also known as T-DM1) is an antibody-drug conjugate (ADC) approved for the treatment of HER2-positive breast cancer. While the treatment with T-DM1 results in significant efficacy in the selected patient population, nonetheless, there are concerns with side effects such as thrombocytopenia and hepatotoxicity. While current understanding of the mechanism of T-DM1-mediated side effects is still incomplete, there have been several reports of HER2-dependent and/or -independent mechanisms that could be associated with the T-DM1-induced adverse events. This review highlights the importance of HER2-independent mechanism of T-DM1 to induce hepatotoxicity, which offers a new insight into a role for CKAP5 in the overall maytansinoid-based ADC (DM1 and DM4)-mediated cytotoxicity. This discovery provides a molecular basis for T-DM1-induced off-target toxicity and opens a new avenue for developing the next generation of ADCs.

PET and SPECT Imaging of the EGFR Family (RTK Class I) in Oncology

The human epidermal growth factor receptor family (EGFR-family, other designations: HER family, RTK Class I) is strongly linked to oncogenic transformation. Its members are frequently overexpressed in cancer and have become attractive targets for cancer therapy. To ensure effective patient care, potential responders to HER-targeted therapy need to be identified. Radionuclide molecular imaging can be a key asset for the detection of overexpression of EGFR-family members. It meets the need for repeatable whole-body assessment of the molecular disease profile, solving problems of heterogeneity and expression alterations over time. Tracer development is a multifactorial process. The optimal tracer design depends on the application and the particular challenges of the molecular target (target expression in tumors, endogenous expression in healthy tissue, accessibility). We have herein summarized the recent preclinical and clinical data on agents for Positron Emission Tomography (PET) and Single Photon Emission Tomography (SPECT) imaging of EGFR-family receptors in oncology. Antibody-based tracers are still extensively investigated. However, their dominance starts to be challenged by a number of tracers based on different classes of targeting proteins. Among these, engineered scaffold proteins (ESP) and single domain antibodies (sdAb) show highly encouraging results in clinical studies marking a noticeable trend towards the use of smaller sized agents for HER imaging.

Adjuvant Trastuzumab Emtansine (T-DM1) and Concurrent Radiotherapy for Residual Invasive HER2-positive Breast Cancer: Single-center Preliminary Results

OBJECTIVES

The treatment of nonmetastatic HER2-positive breast cancer with residual invasive disease using concurrent Trastuzumab emtansine (T-DM1) and radiotherapy appears to be an effective option. Our aim was to evaluate the acute side effects of this treatment regime.

METHODS

Fourteen patients were treated between March 2019 and April 2020 concurrent T-DM1 and radiotherapy. Left ventricular ejection fraction was assessed at baseline, before and after radiotherapy. All toxicities were evaluated using Common Terminology Criteria of Adverse Events (CTCAE) version 3.0.

RESULTS

The median age was 55 years (range 36 to 72). All patients received total dose of 50 Gy for the breast/ chest wall, 10 patients got lymph node irradiation, 4 patients received an additional tumor bed boost. The most common side effect was grade 1 radiodermatitis. A reversible grade 2 left ventricular ejection fraction decrease occurred in 2 patients. During our examination 3 patients showed alanine aminotransferases increase after the cycle 4 of T-DM1, 1 patient had grade 1, 1 patient grade 2, and 1 patient grade 3 alanine aminotransferase increases.

CONCLUSIONS

The acute toxicity rate especially focusing on skin and cardiac toxicity were assumed acceptable in our cohort. To safely administer this concomitant treatment, further examination and prospective data are needed.

Quantification of Trastuzumab-HER2 Engagement In Vitro and In Vivo

Human EGF Receptor 2 (HER2) is an important oncogene driving aggressive metastatic growth in up to 20% of breast cancer tumors. At the same time, it presents a target for passive immunotherapy such as trastuzumab (TZM). Although TZM has been widely used clinically since 1998, not all eligible patients benefit from this therapy due to primary and acquired drug resistance as well as potentially lack of drug exposure. Hence, it is critical to directly quantify TZM–HER2 binding dynamics, also known as cellular target engagement, in undisturbed tumor environments in live, intact tumor xenograft models. Herein, we report the direct measurement of TZM–HER2 binding in HER2-positive human breast cancer cells and tumor xenografts using fluorescence lifetime Forster Resonance Energy Transfer (FLI-FRET) via near-infrared (NIR) microscopy (FLIM-FRET) as well as macroscopy (MFLI-FRET) approaches. By sensing the reduction of fluorescence lifetime of donor-labeled TZM in the presence of acceptor-labeled TZM, we successfully quantified the fraction of HER2-bound and internalized TZM immunoconjugate both in cell culture and tumor xenografts in live animals. Ex vivo immunohistological analysis of tumors confirmed the binding and internalization of TZM–HER2 complex in breast cancer cells. Thus, FLI-FRET imaging presents a powerful analytical tool to monitor and quantify cellular target engagement and subsequent intracellular drug delivery in live HER2-positive tumor xenografts.

Dose-reduced trastuzumab deruxtecan can be safely used in liver failure and active leptomeningeal metastases

Trastuzumab deruxtecan has been shown to have responses in heavily pretreated patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer. However, the safety of this medication in patients with severe liver dysfunction and untreated or symptomatic central nervous system metastases is unknown. We describe a patient with metastatic HER2-positive breast cancer with liver failure and leptomeningeal metastases who was treated with dose-reduced trastuzumab deruxtecan. With treatment, the patient’s hyperbilirubinemia resolved and she demonstrated a response on imaging. She was dose-escalated to full dose with minimal adverse events.

Safety of trastuzumab after trastuzumab emtansine-induced nodular regenerative hyperplasia: A case report

INTRODUCTION

Trastuzumab emtansine is an antibody-drug conjugate targeting the human epidermal growth factor receptor 2 use in recurrent metastatic breast cancer. Cases of trastuzumab emtansine-induced nodular regenerative hyperplasia are often reported as overt noncirrhotic portal hypertension with ascites and variceal bleeding.

CASE REPORT

We report the case of a 61-year-old woman who present multiple stellate angiomas with gradual increased liver transaminases and reduced platelet count during a 27-months course on trastuzumab emtansine therapy for recurrent metastatic breast cancer. After the nodular regenerative hyperplasia was histologically confirmed, the trastuzumab emtansine was stopped. After two months, trastuzumab was restarted together with exemestane. During trastuzumab therapy, the patient had a normalization of liver transaminases, platelet count and a gradual improvement of her stellate angiomas. Trastuzumab was continued for 15 months without any reoccurrence of nodular regenerative hyperplasia.

MANAGEMENT AND OUTCOME

Nodular regenerative hyperplasia should be suspected after one year of trastuzumab emtansine treatment in patients with signs of portal hypertension without cirrhosis. Definitive cessation of trastuzumab emtansine is required after a diagnosis of nodular regenerative hyperplasia and complete resolution of symptoms generally takes several months.

DISCUSSION

Based on fundamental studies, nodular regenerative hyperplasia is probably caused by the emtansine (DM1) part of the trastuzumab emtansine. It is still unclear if trastuzumab therapy can be reintroduced after nodular regenerative hyperplasia induced by trastuzumab emtansine, depriving the patient of a HER2-targeted therapy. Only one case reported having given trastuzumab in this situation over one month. In our case, trastuzumab was reintroduced without any complications for a long extent following TDM1-associated nodular regenerative hyperplasia.

Binding and functional profiling of antibody mutants guides selection of optimal candidates as antibody drug conjugates

An increasingly appreciated conundrum in the discovery of antibody drug conjugates (ADCs) is that an antibody that was selected primarily for strong binding to its cancer target may not serve as an optimal ADC. In this study, we performed mechanistic cell-based experiments to determine the correlation between antibody affinity, avidity, internalization and ADC efficacy. We used structure-guided design to assemble a panel of antibody mutants with predicted Her2 affinities ranging from higher to lower relative to the parent antibody, Herceptin. These antibodies were ranked for binding via SPR and via flow-cytometry on high-Her2 SKOV3 cells and low-Her2 MCF7 cells, the latter acting as a surrogate for low-Her2 normal cells. A subpanel of variants, representative of different Her2-binding affinities (2 strong, 2 moderate and 3 weak), were further screened via high-content imaging for internalization efficacies in high versus low-Her2 cells. Finally, these antibodies were evaluated in ADC cytotoxicity screening assays (using DM1 and MMAE secondary antibodies) and as antibody-drug conjugates (DM1 and PNU159682). Our results identified specific but weak Her2-binding variants as optimal candidates for developing DM1 and PNU ADCs since they exhibited high potencies (low to sub-nM) in high-Her2 SKOV3 cells and low toxicities in low-Her2 cells. The 2 strong-affinity variants were highly potent in SKOV3 cells but also showed significant toxicities in low-Her2 cells and therefore are predicted to be toxic in normal tissues. Our findings show that pharmacological profiling of an antibody library in multiple binding and functional assays allows for selection of optimal ADCs.

Sinusoidal obstruction syndrome post-treatment with trastuzumab emtansine (T-DM1) in advanced breast cancer

Trastuzumab emtansine (T-DM1) is an antibody-drug conjugate approved for use in the treatment of human epidermal growth factor receptor 2-positive metastatic breast cancer. Here, we present the cases of two patients with metastatic breast cancer who received T-DM1 monotherapy and developed noncirrhotic portal hypertension (NCPH). Patient 1 presented with ruptured gastric varices at 2 years and 5 months after T-DM1 treatment. Patient 2 presented with intrahepatic portal-hepatic venous shunt at 2 years and 6 months and portal-systemic shunt encephalopathy at 4 years and 11 months after T-DM1 treatment. In both the patients, liver biopsies revealed sinusoidal obstruction syndrome (SOS). T-DM1-induced hepatotoxicity can result from SOS. In long-term administration of T-DM1 the unfavorable events associated with chronic liver circulatory disorder due to SOS, such as NCPH, are concerning.

HER2-Overexpressing/Amplified Breast Cancer as a Testing Ground for Antibody-Drug Conjugate Drug Development in Solid Tumors

Efficacy data from the KATHERINE clinical trial, comparing the HER2-directed antibody-drug conjugate (ADC) ado-trastuzumab emtansine (T-DM1) to trastuzumab in patients with early-stage HER2-amplified/overexpressing breast cancer with residual disease after neoadjuvant therapy, demonstrates superiority of T-DM1 (HR for invasive disease or death, 0.50; P < 0.001). This establishes foundational precedent for ADCs as effective therapy for treatment of subclinical micrometastasis in an adjuvant (or post-neoadjuvant) early-stage solid tumor setting. Despite this achievement, general principles from proposed systems pharmacokinetic modeling for intracellular processing of ADCs indicate potential shortcomings of T-DM1: (i) C _max limited by toxicities; (ii) slow internalization rate; (iii) resistance mechanisms due to defects in intracellular trafficking [loss of lysosomal transporter solute carrier family 46 member 3, (SLC46A3)], and increased expression of drug transporters MDR1 and MRP1; and (iv) lack of payload bystander effects limiting utility in tumors with heterogeneous HER2 expression. These handicaps may explain the inferiority of T-DM1-based therapy in the neoadjuvant and first-line metastatic HER2⁺ breast cancer settings, and lack of superiority to chemotherapy in HER2⁺ advanced gastric cancer. In this review, we discuss how each of these limitations is being addressed by manipulating internalization and trafficking using HER2:HER2 bispecific or biparatopic antibody backbones, using site-specific, fixed DAR conjugation chemistry, and payload swapping to exploit alternative intracellular targets and to promote bystander effects. Newer HER2-directed ADCs have impressive clinical activity even against tumors with lower levels of HER2 receptor expression. Finally, we highlight ongoing clinical efforts to combine HER2 ADCs with other treatment modalities, including chemotherapy, molecularly targeted therapies, and immunotherapy.

Incorporation of a Hydrophilic Spacer Reduces Hepatic Uptake of HER2-Targeting Affibody-DM1 Drug Conjugates

Affibody molecules are small affinity-engineered scaffold proteins which can be engineered to bind to desired targets. The therapeutic potential of using an affibody molecule targeting HER2, fused to an albumin-binding domain (ABD) and conjugated with the cytotoxic maytansine derivate MC-DM1 (AffiDC), has been validated. Biodistribution studies in mice revealed an elevated hepatic uptake of the AffiDC, but histopathological examination of livers showed no major signs of toxicity. However, previous clinical experience with antibody drug conjugates have revealed a moderate- to high-grade hepatotoxicity in treated patients, which merits efforts to also minimize hepatic uptake of the AffiDCs. In this study, the aim was to reduce the hepatic uptake of AffiDCs and optimize their in vivo targeting properties. We have investigated if incorporation of hydrophilic glutamate-based spacers adjacent to MC-DM1 in the AffiDC, (Z_HER2:2891)₂-ABD-MC-DM1, would counteract the hydrophobic nature of MC-DM1 and, hence, reduce hepatic uptake. Two new AffiDCs including either a triglutamate-spacer-, (Z_HER2:2891)₂-ABD-E₃-MC-DM1, or a hexaglutamate-spacer-, (Z_HER2:2891)₂-ABD-E₆-MC-DM1 next to the site of MC-DM1 conjugation were designed. We radiolabeled the hydrophilized AffiDCs and compared them, both in vitro and in vivo, with the previously investigated (Z_HER2:2891)₂-ABD-MC-DM1 drug conjugate containing no glutamate spacer. All three AffiDCs demonstrated specific binding to HER2 and comparable in vitro cytotoxicity. A comparative biodistribution study of the three radiolabeled AffiDCs showed that the addition of glutamates reduced drug accumulation in the liver while preserving the tumor uptake. These results confirmed the relation between DM1 hydrophobicity and liver accumulation. We believe that the drug development approach described here may also be useful for other affinity protein-based drug conjugates to further improve their in vivo properties and facilitate their clinical translatability.

Antibody-Drug Conjugates for the Therapy of Thoracic Malignancies

Antibody-drug conjugates (ADCs) are a novel class of therapeutic agents incorporating both target-specific monoclonal antibodies and cytotoxic small molecules via a chemical linker. They were first introduced into the clinic for the treatment of advanced hematologic malignancies. The only approved ADC for solid tumors targets erb-b2 receptor tyrosine kinase (HER2), a validated antigen in breast cancer. Many ADCs are under active investigation for various types of solid tumors. In this article, we review the literature from several perspectives including the design, pharmacology, and mechanism-based toxicities of antibody-drug conjugates. We then discuss ADCs currently in clinical development for thoracic malignancies.

Payload of T-DM1 binds to cell surface cytoskeleton-associated protein 5 to mediate cytotoxicity of hepatocytes

Off-target toxicity is a major cause of dose-limiting toxicity for antibody-drug conjugates (ADCs), mechanisms of which remain poorly understood. Here, we demonstrate that cytoskeleton-associated protein 5 (CKAP5) serves as a cell surface target for T-DM1 and that binding of T-DM1 to CKAP5 is mediated by payload (DM1). This study introduces a novel molecular mechanism of ADC payload-mediated interaction with cell surface molecules to induce cytotoxicity. Upon binding to CKAP5, T-DM1 causes cell membrane damage and leads to calcium influx into the cells, resulting in disorganized microtubule network and apoptosis. While binding of T-DM1 with HER2 is critical for killing HER2-positive tumor cells, our data suggest that cytotoxicity induced by T-DM1 interaction with CKAP5 may preferentially damage normal cells/tissues where HER2 expression is low or missing to cause off-target toxicity. This study provides molecular basis of ADC-induced off-target cytotoxicity and opens a new avenue for developing next generation of ADCs.

Nodular Regenerative Hyperplasia Induced by Trastuzumab Emtansine: Role of Emtansine?

Trastuzumab is a monoclonal antibody targeted against the Human Epidermal Growth Factor Receptor 2 (HER2) overexpressed in some breast cancer. This targeted therapy significantly improves the prognosis of these cancers. Recently an anti-HER2 antibodydrug conjugate was shaped in order to facilitate the targeted delivery of potent cytotoxic drug to cancer cells and to reduce resistance. This formulation, called trastuzumab emtansine (T-DM1), consists of the monoclonal antibody trastuzumab linked to a cytotoxic drug (a derivative of maytansine) via a chemical linker. Little is known about adverse reactions due to this new formulation. Herein we described the case of a woman suffering from a HER2-positive breast cancer, treated with trastuzumab for 30 months followed by T-DM1 monotherapy. After 12 months of T-DM1 treatment, a nodular regenerative hyperplasia confirmed by liver biopsy occurred. T-DM1 was stopped and medical imagery showed a resolution of the nodular regenerative hyperplasia. Unfortunately, hepatic metastasis progressed. Few cases of nodular regenerative hyperplasia induced by T-DM1 have been described so far. Further studies are needed to explore pathogenesis of nodular regenerative hyperplasia with this new antibody-drug conjugate treatment.

T-DM1-resistant cells gain high invasive activity via EGFR and integrin cooperated pathways

Ado-trastuzumab emtansine (Kadcyla®; T-DM1) is an antibody-drug conjugate developed to treat trastuzumab-resistant disease. Despite initial favorable outcomes, most patients eventually cease to respond due to developing acquired resistance to T-DM1. Currently, there is no targeted therapy to treat T-DM1-resistant disease. To explore novel therapeutic targets to improve therapeutic efficacy of T-DM1, we generated T-DM1-resistant cells using trastuzumab-resistant JIMT1 cells. We found that the loss of human epidermal growth factor receptor 2 confers T-DM1 resistance, which in turn activates a compensatory mechanism that increases epidermal growth factor receptor (EGFR) expression. Upregulation of EGFR increases the protein levels of α5β1 and αVβ3 integrins, resulting in enhanced motility and invasion of T-DM1-resistant cells. This study delineates previously unappreciated relationships between α5β1 and αVβ3 and suggests that specific integrins should be carefully selected as therapeutic targets to treat T-DM1-resistant disease. Specifically, silencing β1 integrin expression by siRNA in T-DM1-resistant cells destabilizes α5, but increases expression of αV, a critical integrin mediating the invasion and metastases in many different cancers. As a consequence, T-DM1-resistant cells gain metastatic potential and become more invasive. This finding is underscored by the fact that β1 integrin blockage induced by an inhibitory antibody, MAB 13, significantly increases invasion of T-DM1-resistant cells. However, the increased cell invasion induced by β1 integrin blockage can be significantly reduced by either EGFR inhibitor or specific siRNA against αV integrin. The discovery of functional cooperation between EGFR and αV integrin in regulating cell growth and invasion provides an opportunity to develop novel therapeutic strategy by dual-targeting EGFR and specific integrin to overcome T-DM1 resistance.

Bilirubin detoxification using different phytomaterials: characterization and in vitro studies

BACKGROUND

Activated carbon (AC) is a common adsorbent that is used in both artificial and bioartificial liver devices.

METHODS

Three natural materials - date pits of Phoenix dactylifera (fruit), Simmondsia chinensis (jojoba) seeds, and Scenedesmus spp. (microalgae) - were used in the present investigation as precursors for the synthesis of AC using physical activation. The chemical structures and morphology of AC were analyzed. Then, AC's bilirubin adsorption capacity and its cytotoxicity on normal liver (THLE2) and liver cancer (HepG2) cells were characterized.

RESULTS

Compared with the other raw materials examined, date-pit AC was highly selective and showed the most effective capacity of bilirubin adsorption, as judged by isotherm-modeling analysis. MTT in vitro analysis indicated that date-pit AC had the least effect on the viability of both THLE2 and HepG2 cells compared to jojoba seeds and microalgae. All three biomaterials under investigation were used, along with collagen and Matrigel, to grow cells in 3D culture. Fluorescent microscopy confirmed date-pit AC as the best to preserve liver cell integrity.

CONCLUSION

The findings of this study introduce date-pit-based AC as a novel alternative biomaterial for the removal of protein-bound toxins in bioartificial liver devices.

The collagen receptor uPARAP/Endo180 as a novel target for antibody-drug conjugate mediated treatment of mesenchymal and leukemic cancers

A key task in developing the field of personalized cancer therapy is the identification of novel molecular targets that enable treatment of cancers not susceptible to other means of specific therapy. The collagen receptor uPARAP/Endo180 is overexpressed by malignant cells in several non-epithelial cancers, notably including sarcomas, glioblastomas and subsets of acute myeloid leukemia. In contrast, in healthy adult individuals, expression is restricted to minor subsets of mesenchymal cells. Functionally, uPARAP/Endo180 is a rapidly recycling endocytic receptor that delivers its cargo directly into the endosomal-lysosomal system, thus opening a potential route of entry into receptor-positive cells. This combination of specific expression and endocytic function appears well suited for targeting of uPARAP/Endo180-positive cancers by antibody-drug conjugate (ADC) mediated drug delivery. Therefore, we utilized a specific monoclonal antibody against uPARAP/Endo180, raised through immunization of a uPARAP/Endo180 knock-out mouse, which reacts with both the human and the murine receptor, to construct a uPARAP-directed ADC. This antibody was coupled to the highly toxic dolastatin derivative, monomethyl auristatin E, via a cathepsin-labile valine-citrulline linker. With this ADC, we show strong and receptor-dependent cytotoxicity in vitro in uPARAP/Endo180-positive cancer cell lines of sarcoma, glioblastoma and leukemic origin. Furthermore, we demonstrate the potency of the ADC in vivo in a xenograft mouse model with human uPARAP/Endo180-positive leukemic cells, obtaining a complete cure of all tested mice following intravenous ADC treatment with no sign of adverse effects. Our study identifies uPARAP/Endo180 as a promising target for novel therapy against several highly malignant cancer types.

EpCAM aptamer-functionalized polydopamine-coated mesoporous silica nanoparticles loaded with DM1 for targeted therapy in colorectal cancer

DM1, a maytansine derivative, is a highly potential cytotoxic agent but with severe side effects; therefore, its application in clinical cancer therapy is limited. Here, in order to mitigate this intrinsic drawback of DM1, we developed mesoporous silica nanoparticles (MSNs) loaded with DM1 and surface-decorated with hydrochloride dopamine (PDA), polyethylene glycol (PEG), and epithelial cell adhesion molecule (EpCAM) aptamer (APt) for the targeted treatment of colorectal cancer (CRC). In this system, the PDA coating could be used as pH-sensitive gatekeepers to control the release of DM1 from MSNs in response to the pH stimulus and EpCAM APt-guided active targeting enables the increased delivery of DM1 to CRC as well as a reduction in toxicity and side effects by minimizing the exposure of normal tissues to DM1. Results demonstrated that DM1 inhibited the formation of microtubules and induced apoptosis in tumor cells via caspase signaling. In comparison with the control groups, the MSNs-DM1@PDA-PEG-APt bioconjugates exhibited increased binding ability and much higher cytotoxicity to the CRC SW480 cell line. Furthermore, in vivo assays confirmed the advantages of such a strategy. These findings suggested that MSNs-DM1@PDA-PEG-APt could represent a promising therapeutic platform for EpCAM-positive CRC.

Advancing pharmaceutical quality: An overview of science and research in the U.S. FDA's Office of Pharmaceutical Quality

Failures surrounding pharmaceutical quality, particularly with respect to product manufacturing issues and facility remediation, account for the majority of drug shortages and product recalls in the United States. Major scientific advancements pressure established regulatory paradigms, especially in the areas of biosimilars, precision medicine, combination products, emerging manufacturing technologies, and the use of real-world data. Pharmaceutical manufacturing is increasingly globalized, prompting the need for more efficient surveillance systems for monitoring product quality. Furthermore, increasing scrutiny and accelerated approval pathways provide a driving force to be even more efficient with limited regulatory resources. To address these regulatory challenges, the Office of Pharmaceutical Quality (OPQ) in the Center for Drug Evaluation and Research (CDER) at the U.S. Food and Drug Administration (FDA) harbors a rigorous science and research program in core areas that support drug quality review, inspection, surveillance, standards, and policy development. Science and research is the foundation of risk-based quality assessment of new drugs, generic drugs, over-the-counter drugs, and biotechnology products including biosimilars. This is an overview of the science and research activities in OPQ that support the mission of ensuring that safe, effective, and high-quality drugs are available to the American public.

Liver Microvascular Injury and Thrombocytopenia of Antibody-Calicheamicin Conjugates in Cynomolgus Monkeys-Mechanism and Monitoring

Purpose: Adverse reactions reported in patients treated with antibody-calicheamicin conjugates such as gemtuzumab ozogamicin (Mylotarg) and inotuzumab ozogamicin include thrombocytopenia and sinusoidal obstruction syndrome (SOS). The objective of this experimental work was to investigate the mechanism for thrombocytopenia, characterize the liver injury, and identify potential safety biomarkers.Experimental Design: Cynomolgus monkeys were dosed intravenously at 6 mg/m²/dose once every 3 weeks with a nonbinding antibody-calicheamicin conjugate (PF-0259) containing the same linker-payload as gemtuzumab ozogamicin and inotuzumab ozogamicin. Monkeys were necropsied 48 hours after the first administration (day 3) or 3 weeks after the third administration (day 63).Results: PF-0259 induced acute thrombocytopenia (up to 86% platelet reduction) with nadirs on days 3 to 4. There was no indication of effects on megakaryocytes in bone marrow or activation of platelets in peripheral blood. Microscopic evaluation of liver from animals necropsied on day 3 demonstrated midzonal degeneration and loss of sinusoidal endothelial cells (SECs) associated with marked platelet accumulation in sinusoids. Liver histopathology on day 63 showed variable endothelial recovery and progression to a combination of sinusoidal capillarization and sinusoidal dilation/hepatocellular atrophy, consistent with early SOS. Among biomarkers evaluated, there were early and sustained increases in serum hyaluronic acid (HA) that correlated well with serum aspartate aminotransferase and liver microscopic changes, suggesting that HA may be a sensitive diagnostic marker of the liver microvascular injury.Conclusions: These data support the conclusion that target-independent damage to liver SECs may be responsible for acute thrombocytopenia (through platelet sequestration in liver sinusoids) and development of SOS. Clin Cancer Res; 23(7); 1760-70. ©2016 AACR.