Antibody-drug conjugates targeting TROP-2 and incorporating SN-38: A case study of anti-TROP-2 sacituzumab govitecan

Endosomal pH, Redox Dual-Sensitive Prodrug Micelles Based on Hyaluronic Acid for Intracellular Camptothecin Delivery and Active Tumor Targeting in Cancer Therapy

Background: CPT is a pentacyclic monoterpene alkaloid with a wide spectrum of antitumor activity. Its clinical application is restricted due to poor water solubility, instability, and high toxicity. We developed a new kind of multifunctional micelles to improve its solubility, reduce the side effecs, and obtain enhanced antitumor effects. Methods: We constructed HA-CPT nano-self-assembly prodrug micelles, which combined the advantages of pH-sensitivity, redox-sensitivity, and active targeting ability to CD44 receptor-overexpressing cancer cells. To synthesize dual sensitive HA-CPT conjugates, CPT was conjugated with HA by pH-sensitive histidine (His) and redox-sensitive 3,3'-dithiodipropionic acid (DTPA). In vitro, we studied the cellular uptake and antitumor effect for tumor cell lines. In vivo, we explored the bio-distribution and antitumor effects of the micelles in HCT 116 tumor bearing nude mice. Results: The dual-sensitive and active targeting HA-His-ss-CPT micelles was proved to be highly efficient in CPT delivery by the in vitro cellular uptake study. The HA-His-ss-CPT micelles escaped from endosomes of tumor cells within 4 h after cellular uptake due to the proton sponge effect of the conjugating His and then quickly released CPT in the cytosol by glutathione (GSH). In mice, HA-His-ss-CPT micelles displayed efficient tumor accumulation and conspicuous inhibition of tumor growth. Conclusions: The novel, dual-sensitive, active targeting nano-prodrug micelles exhibited high efficiency in drug delivery and cancer therapy. This "all in one" drug delivery system can be realized in an ingenious structure and avoid intricate synthesis. This construction strategy can illume the design of nanocarriers responding to endogenous stimuli in tumors.

Efficacy and Safety of Sacituzumab Govitecan in Patients With Advanced Solid Tumors (TROPiCS-03): Analysis in Patients With Advanced Endometrial Cancer

PURPOSE

Patients with advanced endometrial cancer (EC) who progress on or after platinum-based therapy and immunotherapy have poor prognosis. We report efficacy and safety of sacituzumab govitecan (SG), a trophoblast cell-surface antigen 2 (Trop-2)-directed antibody-drug conjugate, in patients with advanced EC.

METHODS

TROPiCS-03 (ClinicalTrials.gov identifier: NCT03964727) is a multicohort, open-label, phase II basket study in patients with metastatic solid tumors. Eligible patients in the EC cohort received SG 10 mg/kg once on days 1 and 8 every 3 weeks. Primary end point was objective response rate (ORR) by investigator's assessment per RECIST v1.1. Secondary end points included clinical benefit rate (CBR; complete and partial response, and stable disease ≥6 months), duration of response (DOR), and progression-free survival (PFS) per investigator assessment, overall survival, and safety. Trop-2 expression of archival or baseline tumor specimens was analyzed by immunohistochemistry.

RESULTS

At data extraction date, 41 patients were enrolled. Median follow-up was 5.8 months (range, 0.7-19.3); median previous therapies was three (range, 1-6); and 85% of patients received previous chemotherapy and immunotherapy. ORR was 22% (95% CI, 11 to 38); CBR was 32% (95% CI, 18 to 48). Median DOR was 8.8 months (95% CI, 2.8 to not estimable); median PFS was 4.8 months (95% CI, 2.8 to 9.8). Trop-2 exploratory analysis was conducted retrospectively for 39 patients. Tumor Trop-2 protein was highly expressed in EC, showing limited correlation with efficacy. Grade ≥3 treatment-related adverse events (TRAEs) occurred in 73% of patients. Study drug discontinuation due to TRAEs was 5%. Two deaths occurred, deemed unrelated to SG.

CONCLUSION

Findings from TROPiCS-03 showed encouraging efficacy of SG with a manageable toxicity profile in a heavily pretreated population with advanced EC. Safety findings were consistent with the known SG safety profile.

Acid-sensitive prodrugs; a promising approach for site-specific and targeted drug release

Drugs administered through conventional formulations are devoid of targeting and often spread to various undesired sites, leading to sub-lethal concentrations at the site of action and the emergence of undesired effects. Hence, therapeutic agents should be delivered in a controlled manner at target sites. Currently, stimuli-based drug delivery systems have demonstrated a remarkable potential for the site-specific delivery of therapeutic moieties. pH is one of the widely exploited stimuli for drug delivery as several pathogenic conditions such as tumor cells, infectious and inflammatory sites are characterized by a low pH environment. This review article aims to demonstrate various strategies employed in the design of acid-sensitive prodrugs, providing an overview of commercially available acid-sensitive prodrugs. Furthermore, we have compiled the progress made for the development of new acid-sensitive prodrugs currently undergoing clinical trials. These prodrugs include albumin-binding prodrugs (Aldoxorubicin and DK049), polymeric micelle (NC-6300), polymer conjugates (ProLindac™), and an immunoconjugate (IMMU-110). The article encompasses a broad spectrum of studies focused on the development of acid-sensitive prodrugs for anticancer, antibacterial, and anti-inflammatory agents. Finally, the challenges associated with the acid-sensitive prodrug strategy are discussed, along with future directions.

Sacituzumab govitecan for hormone receptor-positive HER2-negative advanced breast cancer

INTRODUCTION

Initial treatment for hormone-receptor positive (HR+)/human epidermal growth factor receptor 2 negative (HER2-) advanced breast cancer (ABC) typically involves endocrine therapy (ET) combined with different targeted agents. When hormonal therapies fail, until recently, the only option available was chemotherapy (ChT), presenting a significant therapeutic challenge. However, the recent introduction of antibody-drug conjugates (ADCs) has provided new treatment alternatives in this context. Sacituzumab govitecan (SG), a novel trophoblast cell-surface antigen 2 (Trop-2)-targeting ADC, has been evaluated following disease progression to ET and ChT in HR+/HER2- ABC.

AREAS COVERED

This review examines the latest clinical trials, including phase I/II and III studies and evaluates the impact of SG on HR+/HER2- ABC. The literature search focused on clinical outcomes, particularly regarding efficacy and safety, comparing them with traditional ChT.

EXPERT OPINION

SG has demonstrated to be an effective treatment for patients with HR+/HER2- ABC after progression to ET and cyclin-dependent kinase 4/6 inhibitors (CDKi) in any setting, and at least two ChT-containing regimens in the advanced setting. With a manageable toxicity profile, SG represents a significant advancement in the treatment landscape for this patient population. However, further research is essential to optimize its application and establish long-term benefits.

Sacituzumab-govitecan in metastatic triple-negative breast cancer: a multicenter effectiveness and safety study

Aim: Sacituzumab-govitecan (Sgov) is a new antibody-drug conjugate recently approved for metastatic triple negative breast cancer (mTNBC), so there are still few data published in the real-world setting.Materials & methods: This study was to analyze the effectiveness and safety of Sgov in mTNBC of patients from the three main hospitals of a city and to compare with the pivotal ASCENT-trial. A total of 46 patients were included, all women diagnosed with mTNBC, with a median age of 52 years and Eastern Cooperative Oncology Group performance status 0-1 71.8% of patients.Results: Sgov effectiveness data seem to be slightly inferior than expected. Furthermore, it is observed that patients with an Eastern Cooperative Oncology Group of two or higher benefit significantly less from treatment with the drug. Safety profile of Sgov is acceptable.

New Advances in Metastatic Urothelial Cancer: A Narrative Review on Recent Developments and Future Perspectives

The standard of care for advanced or metastatic urothelial carcinoma (mUC) was historically identified with platinum-based chemotherapy. Thanks to the advances in biological and genetic knowledge and technologies, new therapeutic agents have emerged in this setting recently: the immune checkpoint inhibitors and the fibroblast growth factor receptor inhibitors as the target therapy for patients harboring alterations in the fibroblast growth factor receptor (FGFR) pathway. However, chasing a tumor's tendency to recur and progress, a new class of agents has more recently entered the scene, with promising results. Antibody-drug conjugates (ADCs) are in fact the latest addition, with enfortumab vedotin being the first to receive accelerated approval by the U.S. Food and Drug Administration in December 2019, followed by sacituzumab govitecan. Many other ADCs are still under investigation. ADCs undoubtedly represent the new frontier, with the potential of transforming the management of mUC treatment in the future. Therefore, we reviewed the landscape of mUC treatment options, giving an insight into the molecular basis and mechanisms, and evaluating new therapeutic strategies in the perspective of more and more personalized treatments.

Natural-source payloads used in the conjugated drugs architecture for cancer therapy: Recent advances and future directions

Drug conjugates are obtained from tumor-located vectors connected to cytotoxic agents via linkers, which are designed to deliver hyper-toxic payloads directly to targeted cancer cells. These drug conjugates include antibody-drug conjugates (ADCs), peptide-drug conjugates (PDCs), small molecule-drug conjugates (SMDCs), nucleic acid aptamer-drug conjugates (ApDCs), and virus-like drug conjugate (VDCs), which show great therapeutic value in the clinic. Drug conjugates consist of a targeting carrier, a linker, and a payload. Payloads are key therapy components. Cytotoxic molecules and their derivatives derived from natural products are commonly used in the payload portion of conjugates. The ideal payload should have sufficient toxicity, stability, coupling sites, and the ability to be released under specific conditions to kill tumor cells. Microtubule protein inhibitors, DNA damage agents, and RNA inhibitors are common cytotoxic molecules. Among these conjugates, cytotoxic molecules of natural origin are summarized based on their mechanism of action, conformational relationships, and the discovery of new derivatives. This paper also mentions some cytotoxic molecules that have the potential to be payloads. It also summarizes the latest technologies and novel conjugates developed in recent years to overcome the shortcomings of ADCs, PDCs, SMDCs, ApDCs, and VDCs. In addition, this paper summarizes the clinical trials conducted on conjugates of these cytotoxic molecules over the last five years. It provides a reference for designing and developing safer and more efficient conjugates.

Antibody-drug conjugates for hepato-pancreato-biliary malignancies: "Magic bullets" to the rescue?

Hepato-Pancreato-Biliary (HPB) malignancies constitute a highly aggressive group of cancers that have a dismal prognosis. Patients not amenable to curative intent surgical resection are managed with systemic chemotherapy which, however, confers little survival benefit. Antibody-Drug Conjugates (ADCs) are tripartite compounds that merge the intricate selectivity and specificity of monoclonal antibodies with the cytodestructive potency of attached supertoxic payloads. In view of the unmet need for drugs that will enhance the survival rates of HPB cancer patients, the assessment of ADCs for treating HPB malignancies has become the focus of extensive clinical and preclinical investigation, showing encouraging preliminary results. In the current review, we offer a comprehensive overview of the growing body of evidence on ADC approaches tested for HPB malignancies. Starting from a concise discussion of the functional principles of ADCs, we summarize here all available data from preclinical and clinical studies evaluating ADCs in HPB cancers.

Sacituzumab govitecan response in extensive leptomeningeal carcinomatosis from triple-negative breast cancer: a case report

Sacituzumab govitecan (SG), a Trop-2-directed antibody-drug conjugate (ADC), was the first ADC approved for patients with metastatic triple-negative breast cancer (mTNBC) who had received at least two prior lines of therapy for advanced disease. Although SG has shown promising clinical activity in treating brain metastases in both ASCENT randomized trials and real-world analysis, its utility in leptomeningeal carcinomatosis (LC) remains underexplored. We report the diagnostic and therapeutic process of a patient who develops extensive LC from TNBC treated with SG. She presented a clinical response after the first cycle of SG with a PFS of 6 months. This case report highlights the need for further inquiry into the use of SG in LC.

INA03: A Potent Transferrin-Competitive Antibody-Drug Conjugate against CD71 for Safer Acute Leukemia Treatment

Innovative strategies for enhancing efficacy and overcoming drug resistance in hematologic cancers, such as using antibody-drug conjugates (ADC), have shifted the paradigm of conventional care by delivering promising outcomes in cancer therapies with a significant reduction in the risk of relapse. Transferrin receptor (TfR1), cluster of differentiation 71 (CD71), is known to be overexpressed in malignant cells and considered a potent antitumor target. Therefore, we developed an anti-CD71 ADC, INA03, a humanized antibody conjugated to monomethyl auristatin E through a 3-arylpropiolonitrile-valine-citrulline linker. In this study, we investigated the potency and safety of INA03, in competition with Transferrin (Tf), the CD71's natural ligand, as a novel strategy to specifically target highly proliferative cells. The high expression of CD71 was confirmed on different leukemic cell lines, allowing INA03 to bind efficiently. Subsequently, INA03 rapidly internalizes into lysosomal compartments, in which its cytotoxic drug is released following cathepsin B cleavage. Downregulation of CD71 expression using shRNA highlighted that INA03-induced cell death was dependent on CD71 density at the cell surface. INA03 intravenous treatment in acute leukemia mouse models significantly reduced tumor burden, increased mouse survival, and showed no residual disease compared with conventional chemotherapies. Because INA03 competes with human Tf, a double knock-in (human CD71/human Tf) competent mouse model was generated to mimic human pharmacokinetics and pharmacodynamics. INA03 administration in human CD71/hTf mice did not reveal any improper toxicities, even at high doses. Hence, these data demonstrate the promising preclinical efficacy and safety of INA03 and support its development as a novel acute leukemia treatment. Significance: The Tf receptor is believed to be undruggable because of its ubiquitous expression. By entering into competition with its cognate ligand, the Tf and INA03 ADC can safely achieve potency.

Antibody drug conjugates: Design implications for clinicians

OBJECTIVE

There are currently 11 antibody-drug conjugates (ADC) that are FDA approved for use in oncologic disease states, with many more in the pipeline. The authors aim to review the pharmacokinetic profiles of the components of ADCs to engage pharmacist practitioners in practical considerations in the care of patients. This article provides an overview on the use of ADCs in the setting of organ dysfunction, drug-drug interactions, and management of on- and off-target adverse effects.

DATA SOURCES

A systematic search of the literature on ADCs through September 2023 was conducted. Clinical trials as well as articles on ADC design and functional components, adverse effects, and pharmacokinetics were reviewed. Reviewed literature included prescribing information as well as tertiary sources and primary literature.

DATA SUMMARY

A total of 11 ADCs were reviewed for the purpose of this article. A description of the mechanism of action and structure of ADCs is outlined, and a table containing description of each currently FDA-approved ADC is included. Various mechanisms of ADC toxicity are reviewed, including how ADC structure may be implicated.

CONCLUSION

It is imperative that pharmacist clinicians understand the design and function of each component of an ADC to continue to assess new approvals for use in oncology patients. Understanding the design of the ADC can help a pharmacy practitioner compare and contrast adverse effect profiles to support their multidisciplinary teams and to engage patients in education and management of their care.

Development of an ELISA with acidification treatment for an antibody conjugate incorporating Exatecans

The successful development of Sacituzumab Govitecan and Trastuzumab Deruxtecan has made camptothecin derivatives one of the most popular payloads for antibody-drug conjugates (ADCs). Camptothecin and its derivatives all exist in a pH-dependent equilibrium between the carboxylate and lactone forms. Such transformation may lead to differences in the ratio of the two molecular forms in calibration standards and biological matrix (bio-matrix) samples, thereby leading to inaccurate conjugated antibody results. In this study, we reported an enzyme-linked immunosorbent assay (ELISA) free of the aforementioned influence for the detection of the Exatecans-conjugated antibody (conjugated SM001) in cynomolgus monkey serum. The assay was developed by first acidifying all samples with glacial acetic acid (HAc), then performing neutralization and thereafter capturing conjugated SM001 with anti-Exatecan monoclonal antibody (mAb) and detecting it with biotinylated Nectin4 (hNectin4-Bio) and horseradish peroxidase-labeled streptavidin (SA-HRP). Results showed that all tested performance parameters met the acceptance criteria. The conjugated SM001 concentrations obtained were in parallel to but slightly lower than total antibody (TAb) throughout the pharmacokinetic (PK) study, revealing that the assay strategy implemented for conjugated SM001 measurement worked well for the elimination of interference triggered by the heterogeneous existence of the lactone and carboxylate forms of Exatecan (lactone-Exatecan and carboxylate-Exatecan).

OptimICE-RD: sacituzumab govitecan + pembrolizumab vs pembrolizumab (± capecitabine) for residual triple-negative breast cancer

Patients with early-stage triple-negative breast cancer (TNBC) with residual invasive disease after neoadjuvant therapy have a high risk of recurrence even with neoadjuvant and adjuvant treatment with pembrolizumab. Sacituzumab govitecan, a Trop-2-directed antibody-drug conjugate with a topoisomerase I inhibitor payload, improved progression-free survival (PFS) and overall survival (OS) versus chemotherapy in patients with pre-treated metastatic TNBC. Moreover, preclinical data suggest that topoisomerase I inhibitors may enhance the effects of immune checkpoint inhibitors through activation of the cGAS-STING pathway. Here we describe the international randomized phase III AFT-65/ASCENT-05/OptimICE-RD trial, which evaluates the efficacy and safety of sacituzumab govitecan plus pembrolizumab versus treatment of physician's choice (pembrolizumab ± capecitabine) among patients with early-stage TNBC with residual invasive disease after neoadjuvant therapy.Clinical Trial Registration: NCT05633654 (ClinicalTrials.gov)Other Study ID Number(s): Gilead Study ID: GS-US-595-6184Registration date: 1 December 2022Study start date: 12 December 2022Recruitment status: Recruiting.

Contemporary Approaches to Immunotherapy of Solid Tumors

In recent years, the arrival of the immunotherapy industry has introduced the possibility of providing transformative, durable, and potentially curative outcomes for various forms of malignancies. However, further research has shown that there are a number of issues that significantly reduce the effectiveness of immunotherapy, especially in solid tumors. First of all, these problems are related to the protective mechanisms of the tumor and its microenvironment. Currently, major efforts are focused on overcoming protective mechanisms by using different adoptive cell therapy variants and modifications of genetically engineered constructs. In addition, a complex workforce is required to develop and implement these treatments. To overcome these significant challenges, innovative strategies and approaches are necessary to engineer more powerful variations of immunotherapy with improved antitumor activity and decreased toxicity. In this review, we discuss recent innovations in immunotherapy aimed at improving clinical efficacy in solid tumors, as well as strategies to overcome the limitations of various immunotherapies.

Antibody and siRNA Nanocarriers to Suppress Wnt Signaling, Tumor Growth, and Lung Metastasis in Triple-Negative Breast Cancer

The paucity of targeted therapies for triple-negative breast cancer (TNBC) causes patients with this aggressive disease to suffer a poor clinical prognosis. A promising target for therapeutic intervention is the Wnt signaling pathway, which is activated in TNBC cells when extracellular Wnt ligands bind overexpressed Frizzled7 (FZD7) transmembrane receptors. This stabilizes intracellular β-catenin proteins that in turn promote transcription of oncogenes that drive tumor growth and metastasis. To suppress Wnt signaling in TNBC cells, we developed therapeutic nanoparticles (NPs) functionalized with FZD7 antibodies and β-catenin small interfering RNAs (siRNAs). The antibodies enable TNBC cell-specific binding and inhibit Wnt signaling by locking FZD7 receptors in a ligand unresponsive state, while the siRNAs suppress β-catenin through RNA interference. Compared to NPs coated with antibodies or siRNAs individually, NPs coated with both agents more potently reduce the expression of several Wnt related genes in TNBC cells, leading to greater inhibition of cell proliferation, migration, and spheroid formation. In two murine models of metastatic TNBC, the dual antibody/siRNA nanocarriers outperformed controls in terms of inhibiting tumor growth, metastasis, and recurrence. These findings demonstrate suppressing Wnt signaling at both the receptor and mRNA levels via antibody/siRNA nanocarriers is a promising approach to combat TNBC.

Quantifying payloads of antibody‒drug conjugates using a postcolumn infused-internal standard strategy with LC‒MS

BACKGROUND

Antibody‒drug conjugates (ADCs) are innovative biopharmaceutics consisting of a monoclonal antibody, linkers, and cytotoxic payloads. Monitoring circulating payload concentrations has the potential to identify ADC toxicity; however, accurate quantification faces challenges, including low plasma concentrations, severe matrix effects, and the absence of stable isotope-labeled internal standards (SIL-IS) for payloads and their derivatives. Previous studies used structural analogs as internal standards, but different retention times between structural analogs and target analytes may hinder effective matrix correction. Therefore, a more flexible approach is required for precise payload quantification.

RESULTS

We developed an LC‒MS/MS method incorporating a postcolumn-infused internal standard (PCI-IS) strategy for quantifying payloads and their derivatives of trastuzumab emtansine, trastuzumab deruxtecan, and sacituzumab govitecan, including DM1, MCC-DM1, DXd, SN-38, and SN-38G. Structural analogs (maytansine, Lys-MCC-DM1, and exatecan) were selected as PCI-IS candidates, and their accuracy performance was evaluated based on the percentage of samples within 80%-120% quantification accuracy. Compared to the approach without PCI-IS correction, exatecan enhanced the accuracy performance from 30-40%-100% for SN-38 and DXd, while maytansine and Lys-MCC-DM1 showed comparable accuracy for DM1 and MCC-DM1. This validated PCI-IS analytical method showed superior normalization of matrix effect in all analytes compared to the conventional internal standard approach. The clinical application of this approach showed pronounced differences in DXd and SN-38 concentrations before and after PCI-IS correction. Moreover, only DXd concentrations after PCI-IS correction were significantly higher in patients with thrombocytopenia (p = 0.037).

SIGNIFICANCE

This approach effectively addressed the issue of unavailability of SIL-IS for novel ADC payloads and provided more accurate quantification, potentially yielding more robust statistical outcomes for understanding the exposure-toxicity relationship in ADCs. It is anticipated that this PCI-IS strategy may be extrapolated to quantify payloads and derivatives in diverse ADCs, thereby providing invaluable insights into drug toxicity and fortifying patient safety in ADC usage.

A simple and highly sensitive LC-MS workflow for characterization and quantification of ADC cleavable payloads

Antibody-drug conjugates (ADC) payloads are cleavable drugs that act as the warhead to exert an ADC's cytotoxic effects on cancer cells intracellularly. A simple and highly sensitive workflow is developed and validated for the simultaneous quantification of six ADC payloads, namely SN-38, MTX, DXd, MMAE, MMAF and Calicheamicin (CM). The workflow consists of a short and simple sample extraction using a methanol-ethanol mixture, followed by a fast liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. The results showed that well-validated linear response ranges of 0.4-100 nM for SN38, MTX and DXd, 0.04-100 nM for MMAE and MMAF, 0.4-1000 nM for CM were achieved in mouse serum. Recoveries for all six payloads at three different concentrations (low, medium and high) were more than 85%. An ultra-low sample volume of only 5 µL of serum is required due to the high sensitivity of the method. This validated method was successfully applied to a pharmacokinetic study to quantify MMAE in mouse serum samples.

Antibody-Drug Conjugates in the Treatment of Genitourinary Cancers: An Updated Review of Data

The treatment landscape of genitourinary cancers has significantly evolved over the past few years. Renal cell carcinoma, bladder cancer, and prostate cancer are the most common genitourinary malignancies. Recent advancements have produced new targeted therapies, particularly antibody-drug conjugates (ADCs), due to a better understanding of the underlying oncogenic factors and molecular mechanisms involved. ADCs function as a 'drug delivery into the tumor' system. They are composed of an antigen-directed antibody linked to a cytotoxic drug that releases cytotoxic components after binding to the tumor cell's surface antigen. ADCs have been proven to be extremely promising in the treatment of several cancer types. For GU cancers, this novel treatment has only benefited patients with metastatic urothelial cancer (mUC). The rest of the GU cancer paradigm does not have any FDA-approved ADC treatment options available yet. In this study, we have thoroughly completed a narrative review of the current literature and summarized preclinical studies and clinical trials that evaluated the utility, activity, and toxicity of ADCs in GU cancers, the prospects of ADC development, and the ongoing clinical trials. Prospective clinical trials, retrospective studies, case reports, and scoping reviews were included.

Antibody-drug conjugates targeting HER2 for the treatment of urothelial carcinoma: potential therapies for HER2-positive urothelial carcinoma

Urothelial carcinoma (UC) is a common cancer characterized by high morbidity and mortality rates. Despite advancements in treatment, challenges such as recurrence and low response rates persist. Antibody-drug conjugates (ADCs) have emerged as a promising therapeutic approach for various cancers, although their application in UC is currently limited. This review focuses on recent research regarding ADCs designed to treat UC by targeting human epidermal growth factor receptor 2 (HER2), a surface antigen expressed on tumor cells. ADCs comprise three main components: an antibody, a linker, and a cytotoxic payload. The antibody selectively binds to tumor cell surface antigens, facilitating targeted delivery of the cytotoxic drug, while linkers play a crucial role in ensuring stability and controlled release of the payload. Cleavable linkers release the drug within tumor cells, while non-cleavable linkers ensure stability during circulation. The cytotoxic payload exerts its antitumor effect by disrupting cellular pathways. HER2 is commonly overexpressed in UCs, making it a potential therapeutic target. Several ADCs targeting HER2 have been approved for cancer treatment, but their use in UC is still being tested. Numerous HER2 ADCs have demonstrated significant growth inhibition and induction of apoptosis in translational models of HER2-overexpressing bladder cancer. Ongoing clinical trials are assessing the efficacy and safety of ADCs targeting HER2 in UC, with the aim of determining tumor response and the potential of ADCs as a treatment option for UC patients. The development of effective therapies with improved response rates and long-term effectiveness is crucial for advanced and metastatic UC. ADCs targeting HER2 show promise in this regard and merit further investigation for UC treatment.

Antibody-drug conjugates in urothelial carcinoma: scientometric analysis and clinical trials analysis

In 2020, bladder cancer, which commonly presents as urothelial carcinoma, became the 10th most common malignancy. For patients with metastatic urothelial carcinoma, the standard first-line treatment remains platinum-based chemotherapy, with immunotherapy serving as an alternative in cases of programmed death ligand 1 expression. However, treatment options become limited upon resistance to platinum and programmed death 1 or programmed death ligand 1 agents. Since the FDA's approval of Enfortumab Vedotin and Sacituzumab Govitecan, the therapeutic landscape has expanded, heralding a shift towards antibody-drug conjugates as potential first-line therapies. Our review employed a robust scientometric approach to assess 475 publications on antibody-drug conjugates in urothelial carcinoma, revealing a surge in related studies since 2018, predominantly led by U.S. institutions. Moreover, 89 clinical trials were examined, with 36 in Phase II and 13 in Phase III, exploring antibody-drug conjugates as both monotherapies and in combination with other agents. Promisingly, novel targets like HER-2 and EpCAM exhibit substantial therapeutic potential. These findings affirm the increasing significance of antibody-drug conjugates in urothelial carcinoma treatment, transitioning them from posterior-line to frontline therapies. Future research is poised to focus on new therapeutic targets, combination therapy optimization, treatment personalization, exploration of double antibody-coupled drugs, and strategies to overcome drug resistance.

Streptavidin-drug conjugates streamline optimization of antibody-based conditioning for hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) conditioning using antibody-drug conjugates (ADC) is a promising alternative to conventional chemotherapy- and irradiation-based conditioning regimens. The drug payload bound to an ADC is a key contributor to its efficacy and potential toxicities; however, a comparison of HSCT conditioning ADCs produced with different toxic payloads has not been performed. Indeed, ADC optimization studies in general are hampered by the inability to produce and screen multiple combinations of antibody and drug payload in a rapid, cost-effective manner. Herein, we used Click chemistry to covalently conjugate four different small molecule payloads to streptavidin; these streptavidin-drug conjugates can then be joined to any biotinylated antibody to produce stable, indirectly conjugated ADCs. Evaluating CD45-targeted ADCs produced with this system, we found the pyrrolobenzodiazepine (PBD) dimer SGD-1882 was the most effective payload for targeting mouse and human hematopoietic stem cells (HSCs) and acute myeloid leukemia cells. In murine syngeneic HSCT studies, a single dose of CD45-PBD enabled near-complete conversion to donor hematopoiesis. Finally, human CD45-PBD provided significant antitumor benefit in a patient-derived xenograft model of acute myeloid leukemia. As our streptavidin-drug conjugates were generated in-house with readily accessible equipment, reagents, and routine molecular biology techniques, we anticipate this flexible platform will facilitate the evaluation and optimization of ADCs for myriad targeting applications.

The JAVELIN Bladder Medley trial: avelumab-based combinations as first-line maintenance in advanced urothelial carcinoma

Results from JAVELIN Bladder 100 established avelumab (anti-PD-L1) first-line maintenance as the standard-of-care treatment for patients with advanced urothelial carcinoma (UC) that has not progressed with first-line platinum-based chemotherapy. We describe the design of JAVELIN Bladder Medley (NCT05327530), an ongoing phase II, multicenter, randomized, open-label, parallel-arm, umbrella trial. Overall, 252 patients with advanced UC who are progression-free following first-line platinum-based chemotherapy will be randomized 1:2:2:2 to receive maintenance therapy with avelumab alone (control group) or combined with sacituzumab govitecan (anti-Trop-2/topoisomerase inhibitor conjugate), M6223 (anti-TIGIT) or NKTR-255 (recombinant human IL-15). Primary end points are progression-free survival per investigator and safety/tolerability of the combination regimens. Secondary end points include overall survival, objective response and duration of response per investigator, and pharmacokinetics.

Development of a Targeted SN-38-Conjugate for the Treatment of Glioblastoma

Glioblastoma (GBM) is the most aggressive and fatal brain tumor, with approximately 10,000 people diagnosed every year in the United States alone. The typical survival period for individuals with glioblastoma ranges from 12 to 18 months, with significant recurrence rates. Common therapeutic modalities for brain tumors are chemotherapy and radiotherapy. The main challenges with chemotherapy for the treatment of glioblastoma are high toxicity, poor selectivity, and limited accumulation of therapeutic anticancer agents in brain tumors as a result of the presence of the blood-brain barrier. To overcome these challenges, researchers have explored strategies involving the combination of targeting peptides possessing a specific affinity for overexpressed cell-surface receptors with conventional chemotherapy agents via the prodrug approach. This approach results in the creation of peptide drug conjugates (PDCs), which facilitate traversal across the blood-brain barrier (BBB), enable preferential accumulation of chemotherapy within the neoplastic microenvironment, and selectively target cancerous cells. This approach increases accumulation in tumors, thereby improving therapeutic efficiency and minimizing toxicity. Leveraging the affinity of the HAIYPRH (T7) peptide for the transferrin receptor (TfR) overexpressed on the blood-brain barrier and glioma cells, a novel T7-SN-38 peptide drug conjugate was developed. The T7-SN-38 peptide drug conjugate demonstrates about a 2-fold reduction in glide score (binding affinity) compared to T7 while maintaining a comparable orientation within the TfR target site using Schrödinger-2022-3 Maestro 13.3 for ligand preparation and Glide SP-Peptide docking. Additionally, SN-38 extends into a solvent-accessible region, enhancing its susceptibility to protease hydrolysis at the cathepsin B (Cat B) cleavable site. The SN-38-ether-peptide drug conjugate displayed high stability in buffer at physiological pH, and cleavage of the conjugate to release free cytotoxic SN-38 was observed in the presence of exogenous cathepsin B. The synthesized peptide drug conjugate exhibited potent cytotoxic activities in cellular models of glioblastoma in vitro. In addition, blocking transferrin receptors using the free T7 peptide resulted in a notable inhibition of cytotoxicity of the conjugate, which was reversed when exogenous cathepsin B was added to cells. This work demonstrates the potential for targeted drug delivery to the brain in the treatment of glioblastoma using the transferrin receptor-targeted T7-SN-38 conjugate.

CT109-SN-38, a Novel Antibody-drug Conjugate with Dual Specificity for CEACAM5 and 6, Elicits Potent Killing of Pancreatic Cancer Cells

BACKGROUND

CEACAM5 and CEACAM6 are glycosylphosphatidylinositol (GPI)- linked members of the carcinoembryonic antigen-related cell adhesion molecule (CEACAM) family, which are frequently upregulated in epithelial cancers where they contribute to invasion, metastasis, immune evasion, and resistance to anoikis. CT109 is a novel antibody with dual specificity to both CEACAM5 and 6.

OBJECTIVES

In this study, we aimed to perform the preclinical characterization of CT109 and antibody- drug conjugate (ADCs) derivatives of CT109, focusing on CT109-SN-38.

METHODS

CT109's cognate epitope was characterized by scanning mutagenesis. CT109 specificity and internalization kinetics were assessed by immunoblot and flow cytometry, respectively. Cognate antigen expression prevalence in colorectal cancer and normal tissue arrays was determined by immunohistochemistry. CT109 conjugations were generated by the reaction of reduced CT109 cysteines with maleimide-functionalized payload linkers. In vitro cytotoxic activity of CT109 ADCs was characterized on antigen-positive and negative pancreatic ductal adenocarcinoma cell (PDAC) lines using a luminometric viability assay. In vivo efficacy of CT109-SN-38 was assessed on a PDAC tumor xenograft model at 10 and 25 mg/kg concentrations.

RESULTS

CT109 was shown to bind a glycoepitope centered on N309. CT109 is internalized in the CEACAM5+/CEACAM6+ double-positive PDAC line, BxPC-3, with a t1/2 of 2.3 hours. CT109 ADCs elicit a dose and antigen-dependent cytotoxic effect, with CT109-SN-38 exhibiting an IC50 value of 21 nM in BxPC-3 cells. In a BxPC-3 tumor xenograft model, CT109-SN-38 reduced tumor growth and induced regression in 3/10 mice at a concentration 25 mg/kg.

CONCLUSION

These data suggest that further preclinical and clinical development of CT109-SN-38 is warranted.

Enfortumab vedotin as a salvage option as 5th line therapy for metastatic urothelial bladder cancer

A 67-year-old female patient with a muscle-invasive, non-metastatic urothelial bladder cancer (UC) (pT2 G3 cN0 cM0) developed metachronous metastases within 6 months after radical cystectomy with ileal conduit urinary diversion. After a good primary response to platinum-based chemotherapy, treatment was switched to the immune checkpoint inhibitor (ICI) pembrolizumab due to progressive disease. Subsequently the patient underwent selective internal radiotherapy (SIRT) of the liver and received vinflunine as well as a re-challenge with pembrolizumab. Two years after the initial diagnosis, rapid disease progression ultimately led to a switch to 5th line therapy with enfortumab vedotin (EV), which had only been approved in the United States at that time. The antibody-drug conjugate was well tolerated by the patient after dose reduction to 1.0 mg/ kg body weight. Simultaneous irradiation of newly occurring precardiac, hepatic and cerebral metastases were necessary. After 10 months of therapy with EV, tumour regression was observed accompanied with good symptom control. The presented case illustrates the efficacy and tolerability of EV in a heavily pre-treated patient with metastatic UC (mUC).

Trends in the Development of Antibody-Drug Conjugates for Cancer Therapy

In cancer treatment, the first-generation, cytotoxic drugs, though effective against cancer cells, also harmed healthy ones. The second-generation targeted cancer cells precisely to inhibit their growth. Enter the third-generation, consisting of immuno-oncology drugs, designed to combat drug resistance and bolster the immune system's defenses. These advanced therapies operate by obstructing the uncontrolled growth and spread of cancer cells through the body, ultimately eliminating them effectively. Within the arsenal of cancer treatment, monoclonal antibodies offer several advantages, including inducing cancer cell apoptosis, precise targeting, prolonged presence in the body, and minimal side effects. A recent development in cancer therapy is Antibody-Drug Conjugates (ADCs), initially developed in the mid-20th century. The second generation of ADCs addressed this issue through innovative antibody modification techniques, such as DAR regulation, amino acid substitutions, incorporation of non-natural amino acids, and enzymatic drug attachment. Currently, a third generation of ADCs is in development. This study presents an overview of 12 available ADCs, reviews 71 recent research papers, and analyzes 128 clinical trial reports. The overarching objective is to gain insights into the prevailing trends in ADC research and development, with a particular focus on emerging frontiers like potential targets, linkers, and drug payloads within the realm of cancer treatment.

Bambu and its applications in the discovery of active molecules against melanoma

PURPOSE OR OBJECTIVE

Melanoma is one of the most dangerous forms of skin cancer and the discovery of novel drugs is an ongoing effort. Quantitative Structure Activity Relationship (QSAR) is a computational method that allows the estimation of the properties of a molecule, including its biological activity. QSAR models have been widely employed in the search for potential drug candidates, but also for agrochemicals and other molecules with applications in different branches of the industry. Here we present Bambu, a simple command line tool to generate QSAR models from high-throughput screening bioassays datasets.

METHODS

The tool was developed using the Python programming language and relies mainly on RDKit for molecule data manipulation, FLAML for automated machine learning and the PubChem REST API for data retrieval. As a proof-of-concept we have employed the tool to generate QSAR models for melanoma cell growth inhibition based on HTS data and used them to screen libraries of FDA-approved drugs and natural compounds. Additionally, Bambu was compared to QSAR-Co, another automated tool for QSAR model generation.

RESULTS

based on the developed tool we were able to produce QSAR models and identify a wide variety of molecules with potential melanoma cell growth inhibitors, many of which with anti-tumoral activity already described. The QSAR models are available through the URL http://caramel.ufpel.edu.br, and all data and code used to generate its models are available at Zenodo (https://doi.org/10.5281/zenodo.7495214). Bambu source code is available at GitHub (https://github.com/omixlab/bambu-v2). In the benchmark, Bambu was able to produce models with higher accuracy, recall, F1 and ROC AUC when compared to QSAR-Co for the selected datasets.

CONCLUSIONS

Bambu is an free and open source tool which facilitates the creation of QSAR models and can be futurely applied in a wide variety of drug discovery projects.

Development of a Cytotoxic Antibody-Drug Conjugate Targeting Membrane Immunoglobulin E-Positive Cells

High numbers of membrane immunoglobulin E (IgE)-positive cells are characteristic of allergic conditions, atopic dermatitis, or IgE myeloma. Antibodies targeting the extracellular membrane-proximal domain of the membranous IgE-B-cell receptor (BCR) fragment can be used for specific depletion of IgE-BCR-positive cells. In this study, we derivatized such an antibody with a toxin and developed an antibody-drug conjugate (ADC) that showed strong cytotoxicity for an IgE-positive target cell line. Site-specific conjugation with maleimidocaproyl-valine-citrulline-p-aminobenzoyloxycarbonyl-monomethyl-auristatin E via a newly introduced single cysteine residue was used to prepare a compound with a drug-antibody ratio of 2 and favorable biophysical properties. The antibody was rapidly taken up by the target cells, showing almost complete internalization after 4 h of treatment. Its cytotoxic effect was potentiated upon cross-linking mediated by an anti-human IgG F(ab')2 fragment. Because of its fast internalization and strict target specificity, this antibody-drug conjugate presents a valuable starting point for the further development of an anti-IgE cell-depleting agent, operating by the combined action of receptor cross-linking and toxin-mediated cytotoxicity.

Antibody-Drug Conjugates: A Review of Approved Drugs and Their Clinical Level of Evidence

Antibody-drug conjugates (ADCs) are an innovative family of agents assembled through linking cytotoxic drugs (payloads) covalently to monoclonal antibodies (mAbs) to be delivered to tumor tissue that express their particular antigen, with the theoretical advantage of an augmented therapeutic ratio. As of June 2023, eleven ADCs have been approved by the Food and Drug Administration (FDA) and are on the market. These drugs have been added to the therapeutic armamentarium of acute myeloblastic and lymphoblastic leukemias, various types of lymphoma, breast, gastric or gastroesophageal junction, lung, urothelial, cervical, and ovarian cancers. They have proven to deliver more potent and effective anti-tumor activities than standard practice in a wide variety of indications. In addition to targeting antigen-expressing tumor cells, bystander effects have been engineered to extend cytotoxic killing to low-antigen-expressing or negative tumor cells in the heterogenous tumor milieu. Inevitably, myelosuppression is a common side effect with most of the ADCs due to the effects of the cytotoxic payload. Also, other unique side effects are specific to the tissue antigen that is targeted for, such as the cardiac toxicity with Her-2 targeting ADCs, and the hemorrhagic side effects with the tissue factor (TF) targeting Tisotumab vedotin. Further exciting developments are centered in the strategies to improve the tolerability and efficacy of the ADCs to improve the therapeutic window; as well as the development of novel payloads including (1) peptide-drug conjugates (PDCs), with the peptide replacing the monoclonal antibody, rendering greater tumor penetration; (2) immune-stimulating antibody conjugates (ISACs), which upon conjugation of the antigen, cause an influx of pro-inflammatory cytokines to activate dendritic cells and harness an anti-tumor T-cell response; and (3) the use of radioactive isotopes as a payload to enhance cytotoxic activity.

Advancements in Systemic Therapy for Pancreatic Cancer

Outcomes for patients with advanced pancreatic cancer have improved in the past 12 years, mainly because of progress made in systemic therapies. New treatment strategies for advanced pancreatic cancer include switch maintenance with cytotoxic therapies, induction maintenance, and the utilization of targeted agents for patients with actionable variants, as well as ongoing development of cytotoxic regimens, such as NALIRIFOX. The activity of immunotherapy has been disappointing to date, but novel combinations and identifying appropriate patient populations may further unlock its potential.

Antibody drug conjugates as targeted cancer therapy: past development, present challenges and future opportunities

Antibody drug conjugates (ADCs) are promising cancer therapeutics with minimal toxicity as compared to small cytotoxic molecules alone and have shown the evidence to overcome resistance against tumor and prevent relapse of cancer. The ADC has a potential to change the paradigm of cancer chemotherapeutic treatment. At present, 13 ADCs have been approved by USFDA for the treatment of various types of solid tumor and haematological malignancies. This review covers the three structural components of an ADC-antibody, linker, and cytotoxic payload-along with their respective structure, chemistry, mechanism of action, and influence on the activity of ADCs. It covers comprehensive insight on structural role of linker towards efficacy, stability & toxicity of ADCs, different types of linkers & various conjugation techniques. A brief overview of various analytical techniques used for the qualitative and quantitative analysis of ADC is summarized. The current challenges of ADCs, such as heterogeneity, bystander effect, protein aggregation, inefficient internalization or poor penetration into tumor cells, narrow therapeutic index, emergence of resistance, etc., are outlined along with recent advances and future opportunities for the development of more promising next-generation ADCs.

Directional conjugation of Trop2 antibody to black phosphorus nanosheets for phototherapy in orthotopic gastric carcinoma

Tumor-associated calcium signal transducer 2 (Trop2) highly specific expression in gastric carcinoma (GC). The combination of Trop2 antibody and phototherapy agents could exhibit synergetic antitumor activity. Black phosphorus nanosheets (BP) are covalently modified with Trop2 IgG antibodies via heterobifunctional linker of polyethylene glycol (PEG). Then the Trop2 antibody was directionally conjugated to BP via Schiff base reaction between aldehyde group from oxidized Trop2 antibody and amino group of PEG. The Trop2-funcationalzied BP can significantly increase the endocytosis of BP in Trop2-positive GC cells exhibiting a reinforced antitumor activity under near infrared (NIR) irradiation. More importantly, a murine orthotopic GC model demonstrates that Trop2 antibody modification can significantly promote the accumulation of BP at tumor tissues and strengthen antitumoral activity of phototherapy. Directional conjugation of Trop2 antibody to BP facilitates the BP with superior stability, tumor targeting ability and excellent anti-tumor activity under NIR irradiation without systemic toxicity.

Synthesis and biological evaluation of theranostic Trastuzumab–SN38 conjugate for Near-IR fluorescence imaging and targeted therapy of HER2+ breast cancer

Here, we report on the design, synthesis, and biological evaluation of a new theranostic antibody drug conjugate (ADC), Cy5-Ab-SS-SN38, that consists of the HER2-specific antibody trastuzumab (Ab) connected to the near infrared (NIR) pentamethine cyanine dye Cy5 and SN38, which is a bioactive metabolite of the anticancer drug irinotecan. SN38 is bound to an antibody through a glutathione-responsive self-immolative disulfide carbamate linker. For the first time, we explored this linker in ADC and found that it to reduce the drug release rate, which is important for safe drug delivery. The developed ADC exhibited specific accumulation and nanomolar anti-breast cancer activity on HER2-positive (HER2+) cell lines but no effect on HER2-. Animals treated with this ADC exhibited good tolerance. In vivo studies have shown that the ADC had good targeting ability for HER2+ tumors with much higher anticancer potency than trastuzumab itself or a mixture of trastuzumab with SN38. Side-by-side HER2+/HER2-xenograft at the 10 mg/kg dose exhibited specific accumulation and reduction of HER2+ tumor but not accumulation or growth inhibition of HER2-counterpart. The self-immolative disulfide linker implemented in this study was proven to be successful, broadening its utilization with other antibodies for targeted anticancer therapy in general. We believe that the theranostic ADCs comprising the glutathione-responsive self-immolative disulfide carbamate linker are applicable for the treatment and fluorescent monitoring of malignancies and anticancer drug delivery.

Interaction of Camptothecin Anticancer Drugs with Ribosomal Proteins L15 and L11: A Molecular Docking Study

The antitumor drug topotecan (TPT) is a potent inhibitor of topoisomerase I, triggering DNA breaks lethal for proliferating cancer cells. The mechanism is common to camptothecins SN38 (the active metabolite of irinotecan) and belotecan (BLT). Recently, TPT was shown to bind the ribosomal protein L15, inducing an antitumor immune activation independent of topoisomerase I. We have modeled the interaction of four camptothecins with RPL15 derived from the 80S human ribosome. Two potential drug-binding sites were identified at Ile135 and Phe129. SN38 can form robust RPL15 complexes at both sites, whereas BLT essentially gave stable complexes with site Ile135. The empirical energy of interaction (ΔE) for SN38 binding to RPL15 is similar to that determined for TPT binding to the topoisomerase I-DNA complex. Molecular models with the ribosomal protein L11 sensitive to topoisomerase inhibitors show that SN38 can form a robust complex at a single site (Cys25), much more stable than those with TPT and BLT. The main camptothecin structural elements implicated in the ribosomal protein interaction are the lactone moiety, the aromatic system and the 10-hydroxyl group. The study provides guidance to the design of modulators of ribosomal proteins L11 and L15, both considered anticancer targets.

Inhibition of WNT signaling by conjugated microRNA nano-carriers: A new therapeutic approach for treating triple-negative breast cancer a perspective review

Triple-Negative Breast Cancer is the most aggressive form and accounts the 15%-25% of all breast cancer. Receptors are absent in triple-negative breast cancer, which makes them unresponsive to the current hormonal therapies. The patients with TNBC are left with the option of cytotoxic chemotherapy. The Wnt pathways are connected to cancer, and when activated, they result in mammary hyperplasia and tumors. The tumor suppressor microRNAs can block tumor cell proliferation, invasion, and migration, lead to cancer cell death, and are also known to down-regulate the WNT signaling. Nanoparticles with microRNA have been seen to be more effective when compared with their single release. In this review, we have tried to understand how Wnt signaling plays a crucial role in TNBC, EMT, metastasis, anti-drug resistance, and regulation of Wnt by microRNA. The role of nano-carriers in delivering micro-RNA. The clinical biomarkers, including the present state-of-the-art, involve novel pathways of Wnt.

NAV-001, a high-efficacy antibody-drug conjugate targeting mesothelin with improved delivery of a potent payload by counteracting MUC16/CA125 inhibitory effects

Subsets of tumor-produced cell surface and secreted proteins can bind to IgG1 type antibodies and suppress their immune-effector activities. As they affect antibody and complement-mediated immunity, we call these proteins humoral immuno-oncology (HIO) factors. Antibody-drug conjugates (ADCs) use antibody targeting to bind cell surface antigens, internalize into the cell, then kill target cells upon liberation of the cytotoxic payload. Binding of the ADC antibody component by a HIO factor may potentially hamper ADC efficacy due to reduced internalization. To determine the potential effects of HIO factor ADC suppression, we evaluated the efficacy of a HIO-refractory, mesothelin-directed ADC (NAV-001) and a HIO-bound, mesothelin-directed ADC (SS1). The HIO factor MUC16/CA125 binding to SS1 ADC was shown to have a negative effect on internalization and tumor cell killing. The MUC16/CA125 refractory NAV-001 ADC was shown to have robust killing of MUC16/CA125 expressing and non-expressing tumor cells in vitro and in vivo at single, sub-mg/kg dosing. Moreover, NAV-001-PNU, which contains the PNU-159682 topoisomerase II inhibitor, demonstrated good stability in vitro and in vivo as well as robust bystander activity of resident cells while maintaining a tolerable safety profile in vivo. Single-dose NAV-001-PNU demonstrated robust tumor regression of a number of patient-derived xenografts from different tumor types regardless of MUC16/CA125 expression. These findings suggest that identification of HIO-refractory antibodies to be used in ADC format may improve therapeutic efficacy as observed by NAV-001 and warrants NAV-001-PNU's advancement to human clinical trials as a monotherapy to treat mesothelin-positive cancers.

Antibody drug conjugates, targeting cancer-expressed EGFR, exhibit potent and specific antitumor activity

The monoclonal antibody '40H3' binds to EGFRvIII and to full-length EGFR when it is overexpressed on cancer cells. To generate candidate cytotoxic antibody-drug conjugates (ADCs), 40H3 was modified by the addition of small molecular weight payloads that included two tubulin-modifying agents, two topoisomerase inhibitors and a pyrrolobenzodiazepine (PBD) dimer. Conjugates retained antigen binding activity comparable to the unmodified 40H3 antibody. The cytotoxicity of five distinct ADCs was evaluated on a variety of EGFR-expressing cells including three triple negative breast cancer (TNBC) lines. Generally, the 40H3 conjugate with the PBD dimer (40H3-Tesirine) was the most active killing agent. The killing of EGFR-positive cells by 40H3-Tesirine correlated with the number of surface binding sites for 40H3. However, bystander killing was also evident in experiments with antigen-negative cells. In vivo tumor xenograft experiments were conducted on two TNBC tumor lines. Three treatments with the 40H3-Tesirine ADC at 1 mg/kg were sufficient to achieve complete remissions without evidence of mouse toxicity. Data support the development of ADCs derived from the 40H3 antibody for the treatment of cancers that express EGFRvIII or high levels of EGFR.

Exploration of the antibody-drug conjugate clinical landscape

The antibody-drug conjugate (ADC) field has undergone a renaissance, with substantial recent developmental investment and subsequent drug approvals over the past 6 y. In November 2022, ElahereTM became the latest ADC to be approved by the US Food and Drug Administration (FDA). To date, over 260 ADCs have been tested in the clinic against various oncology indications. Here, we review the clinical landscape of ADCs that are currently FDA approved (11), agents currently in clinical trials but not yet approved (164), and candidates discontinued following clinical testing (92). These clinically tested ADCs are further analyzed by their targeting tumor antigen(s), linker, payload choices, and highest clinical stage achieved, highlighting limitations associated with the discontinued drug candidates. Lastly, we discuss biologic engineering modifications preclinically demonstrated to improve the therapeutic index that if incorporated may increase the proportion of molecules that successfully transition to regulatory approval.

Targeted Therapy for Locally Advanced or Metastatic Urothelial Cancer (mUC): Therapeutic Potential of Sacituzumab Govitecan

Urothelial carcinoma is the second most frequent genitourinary malignancy. Despite the poor prognosis, new treatment options have emerged and have expanded the therapeutic landscape for the disease. Although major improvements have been achieved, many patients experience rapid disease progression and low responses in subsequent lines of therapy. Sacituzumab govitecan is an ADC that targets Trop-2, which is highly expressed in urothelial cancers. Promising results in early clinical trials have led to further drug development which confirmed encouraging efficacy. Sacituzumab govitecan has been given accelerated approval in 2021 for patients with locally advanced and metastatic urothelial cancer who previously received a platinum containing chemotherapy and either a programmed death receptor-1 or programmed death ligand inhibitor. The results are promising, with encouraging efficacy and safety, however responses are not universal. There is a growing comprehension of mechanisms of resistance and predictive biomarkers that are crucial to improving outcomes. In this review, we summarize the current knowledge on antibody-drug conjugates and the clinical findings that led to the approval of Sacituzumab govitecan and discuss the therapeutic potential of new combinations, mechanisms of resistance and predictive biomarkers.

Delivery of Drugs into Cancer Cells Using Antibody-Drug Conjugates Based on Receptor-Mediated Endocytosis and the Enhanced Permeability and Retention Effect

Innumerable people worldwide die of cancer every year, although pharmaceutical therapy has actualized many benefits in human health. For background, anti-cancer drug development is difficult due to the multifactorial pathogenesis and complicated pathology of cancers. Cancer cells excrete hydrophobic low-molecular anti-cancer drugs by overexpressed efflux transporters such as multiple drug resistance 1 (MDR1) at the apical membrane. Mutation-driven drug resistance is also developed in cancer. Moreover, the poor distribution of drug to cancer cells is a serious problem, because patients suffer from off-target side effects. Thus, highly selective and effective drug delivery into solid cancer cells across the membrane should be established. It is known that substances (10-100 nm in diameter) such as monoclonal antibodies (mAbs) (approximately 14.2 nm in diameter) or nanoparticles spontaneously gather in solid tumor stroma or parenchyma through the capillary endothelial fenestration, ranging from 200-2000 nm, in neovasculatures due to the enhanced permeability and retention (EPR) effect. Furthermore, cancer antigens, such as HER2, Nectin-4, or TROP2, highly selectively expressed on the surface of cancer cells act as a receptor for receptor-mediated endocytosis (RME) using mAbs against such antigens. Thus, antibody-drug conjugates (ADCs) are promising anti-cancer pharmaceutical agents that fulfill accurate distribution due to the EPR effect and due to antibody-antigen binding and membrane permeability owing to RME. In this review, I introduce the implementation and possibility of highly selective anti-cancer drug delivery into solid cancer cells based on the EPR effect and RME using anti-cancer antigens ADCs with payloads through suitable linkers.

Downregulation of MACC1 facilitates the reversal effect of verapamil on the chemoresistance to active metabolite of irinotecan in human colon cancer cells

The aim of this study is to investigate the reversal effect of verapamil (VER) on chemoresistance to irinotecan (CPT-11) in human colon cancer cells and relevant mechanisms. Cell counting kit-8 (CCK-8) test and colony-forming unit (CFU) experiment results show that VER strengthens the sensitivity of human colon cancer cell line HT29 to CPT-11 but has a small effect on SW480 cells. High-throughput transcriptome sequencing, RT-PCR, and Western blot results show that the inhibition of metastasis-associated in colon cancer-1 (MACC1) expression by VER is the key factor for reversal effect on chemoresistance to CPT-11. Transfection experiments further show that VER can reverse the resistance of human colon cancer cells to SN-38, the active metabolite of CPT-11, when MACC1 is overexpressed. The nude mouse transplantation tumor experiment provides an in vivo proof that VER can strengthen sensitivity to CPT-11 in drug-resistant human colon cancer cells, and the effect might be related to the inhibited expression of MACC1. In summary, VER might strengthen the reversal effect of VER on chemoresistance to CPT-11 in human colon cancer cells and facilitate the apoptosis of human colon cancer cells by downregulating MACC1 expression.

Role of sacituzumab govitecan in solid tumors

OBJECTIVE

To evaluate the antibody-drug conjugate- sacituzumab govitecan, its pharmacological properties, toxicity, data supporting efficacy against a wide variety of solid tumors beyond breast cancer, and potential future uses.

DATA SOURCES

Articles in MEDLINE/PubMed databases and the National Institutes of Health Clinical Trials Registry (http://www. clinicaltrials.gov) between January 1, 2015, and July 1, 2021 using MeSH terms sacituzumab govitecan(- hziy) and solid tumors were reviewed.

DATA SUMMARY

Antibody-drug conjugates (ADC's) are a subclass of emerging cancer therapeutics which combines chemotherapy with targeted antibodies. Sacituzumab govitecan (SG) is a novel antibody drug conjugate that has recently been approved by the Food and Drug Administration (FDA) in adult patients for the treatment of unresectable locally advanced or metastatic triple-negative breast cancer (mTNBC) who have received two or more prior systemic therapies, at least one of them for metastatic disease. The approval of sacituzumab govitecan provides a new option for solid tumors that need to be further explored. In this review article, we discussed the pharmacokinetics, pharmacodynamics, safety profile of sacituzumab govitecan and various ongoing clinical trials on sacituzumab govitecan.

CONCLUSION

Sacituzumab is a significant advancement made in cancer therapy. SG has showed significantly improved Health-related quality of life (HRQoL) in addition to prolonged progression free survival and Over all survival in addition to maintaining a good safety profile. Multiple clinical trials on SG are ongoing to evaluate the potential use of SG as neoadjuvant therapy in triple negative breast cancer, as an Adjuvant therapy, in combination with immunotherapy, and also for various solid tumors.

Trophoblast Cell Surface Antigen 2 (TROP2) as a Predictive Bio-Marker for the Therapeutic Efficacy of Sacituzumab Govitecan in Adenocarcinoma of the Esophagus

INTRODUCTION

The Trophoblast cell surface antigen 2 (TROP2) is expressed in many carcinomas and may represent a target for treatment. Sacituzumab govitecan (SG) is a TROP2-directed antibody-drug conjugate (ADC). Nearly nothing is known about the biological effectiveness of SG in esophageal adenocarcinoma (EAC).

MATERIAL AND METHODS

We determined the TROP2 expression in nearly 600 human EAC. In addition, we used the EAC cell lines (ESO-26, OACM5.1C, and FLO-1) and a xenograft mouse model to investigate this relationship.

RESULTS

Of 598 human EACs analyzed, 88% showed varying degrees of TROP2 positivity. High TROP2 positive ESO-26 and low TROP2 positive OACM5.1C showed high sensitivity to SG in contrast to negative FLO-1. In vivo, the ESO-26 tumor shows a significantly better response to SG than the TROP2-negative FLO-1 tumor. ESO-26 vital tumor cells show similar TROP2 expression on all carcinoma cells as before therapy initiation, FLO-1 is persistently negative.

DISCUSSION

Our data suggest that sacituzumab govitecan is a new therapy option in esophageal adenocarcinoma and the TROP2 expression in irinotecan-naïve EAC correlates with the extent of treatment response by sacituzumab govitecan. TROP2 is emerging as a predictive biomarker in completely TROP2-negative tumors. This should be considered in future clinical trials.

Current Analytical Strategies for Antibody-Drug Conjugates in Biomatrices

Antibody-drug conjugates (ADCs) are a new class of biotherapeutics, consisting of a cytotoxic payload covalently bound to an antibody by a linker. Ligand-binding assay (LBA) and liquid chromatography-mass spectrometry (LC-MS) are the favored techniques for the analysis of ADCs in biomatrices. The goal of our review is to provide current strategies related to a series of bioanalytical assays for pharmacokinetics (PK) and anti-drug antibody (ADA) assessments. Furthermore, the strengths and limitations of LBA and LC-MS platforms are compared. Finally, potential factors that affect the performance of the developed assays are also provided. It is hoped that the review can provide valuable insights to bioanalytical scientists on the use of an integrated analytical strategy involving LBA and LC-MS for the bioanalysis of ADCs and related immunogenicity evaluation.

Triple negative breast cancer: approved treatment options and their mechanisms of action

PURPOSE

Breast cancer, the most prevalent cancer worldwide, consists of 4 main subtypes, namely, Luminal A, Luminal B, HER2-positive, and Triple-negative breast cancer (TNBC). Triple-negative breast tumors, which do not express estrogen, progesterone, and HER2 receptors, account for approximately 15-20% of breast cancer cases. The lack of traditional receptor targets contributes to the heterogenous, aggressive, and refractory nature of these tumors, resulting in limited therapeutic strategies.

METHODS

Chemotherapeutics such as taxanes and anthracyclines have been the traditional go to treatment regimens for TNBC patients. Paclitaxel, docetaxel, doxorubicin, and epirubicin have been longstanding, Food and Drug Administration (FDA)-approved therapies against TNBC. Additionally, the FDA approved PARP inhibitors such as olaparib and atezolizumab to be used in combination with chemotherapies, primarily to improve their efficiency and reduce adverse patient outcomes. The immunotherapeutic Keytruda was the latest addition to the FDA-approved list of drugs used to treat TNBC.

RESULTS

The following review aims to elucidate current FDA-approved therapeutics and their mechanisms of action, shedding a light on the various strategies currently used to circumvent the treatment-resistant nature of TNBC cases.

CONCLUSION

The recent approval and use of therapies such as Trodelvy, olaparib and Keytruda has its roots in the development of an understanding of signaling pathways that drive tumour growth. In the future, the emergence of novel drug delivery methods may help increase the efficiency of these therapies whiel also reducing adverse side effects.

The Potential of Topoisomerase Inhibitor-Based Antibody–Drug Conjugates

DNA topoisomerases are essential enzymes that stabilize DNA supercoiling and resolve entanglements. Topoisomerase inhibitors have been widely used as anti-cancer drugs for the past 20 years. Due to their selectivity as topoisomerase I (TOP1) inhibitors that trap TOP1 cleavage complexes, camptothecin and its derivatives are promising anti-cancer drugs. To increase accumulation of TOP1 inhibitors in cancer cells through the targeting of tumors, TOP1 inhibitor antibody–drug conjugates (TOP1-ADC) have been developed and marketed. Some TOP1-ADCs have shown enhanced therapeutic efficacy compared to prototypical anti-cancer ADCs, such as T-DM1. Here, we review various types of camptothecin-based TOP1 inhibitors and recent developments in TOP1-ADCs. We then propose key points for the design and construction of TOP1-ADCs. Finally, we discuss promising combinatorial strategies, including newly developed approaches to maximizing the therapeutic potential of TOP1-ADCs.

The pathological and clinical landscape of refractory metastatic triple negative breast cancer: a narrative review

Background and Objective

Triple negative breast cancer (TNBC) refers to a special subtype of breast cancer that is negative for the estrogen receptor, the progesterone receptors, and human epidermal growth factor receptor 2. As a group of diseases, it has strong heterogeneity. Refractory metastatic triple negative breast cancer (mTNBC) has even greater heterogeneity, more susceptibility to drug resistance, and faster progression, which makes it more difficult to treat effectively and significantly reduces a patient's overall survival. Therefore, in order to overcome this difficulty in clinical practice, we need to deeply understand the special subgroup by analyzing definition and prognostic factors of refractory mTNBC and describing the therapeutic status and future treatment directions.

Methods

Recent domestic and foreign guidelines, as well as clinical studies related to refractory mTNBC on PubMed and the China National Knowledge Infrastructure (CNKI) databases were retrospectively analyzed. The six keywords we selected were used for literature search. Two authors performed database searches independently, and disagreements over the results were mediated by a third reviewer.

Key Content and Findings

According to the guidelines, refractory mTNBC has not been clearly defined. Related studies indicated that tumor heterogeneity may be one of the main mechanisms of early relapse or drug resistance in refractory mTNBC. The clinical treatment options for refractory mTNBC are very limited. Although chemotherapy is the standard treatment, it is limited by poor efficacy and intolerance in the clinical stage. Therefore, in recent years, many studies have explored novel treatment options. Both immunotherapy and poly(ADP-ribose) polymerase (PARP) inhibitors have been selected as first-line treatment in clinical studies, but gained limited benefits. Indeed, clinical studies have shown good efficacy with novel ADCs, which may be promising in the clinical treatment of refractory mTNBC.

Conclusions

Currently, improving the survival time and quality of life of refractory mTNBC are major challenges for clinicians. Novel therapies including immunosuppressive agents, PARP inhibitors, and ADCs rather than chemotherapy alone have achieved good results in the exploration of first-line treatment for refractory TNBC patients, but this warrants further research and investigation.

Designing antibodies as therapeutics

Antibody therapeutics are a large and rapidly expanding drug class providing major health benefits. We provide a snapshot of current antibody therapeutics including their formats, common targets, therapeutic areas, and routes of administration. Our focus is on selected emerging directions in antibody design where progress may provide a broad benefit. These topics include enhancing antibodies for cancer, antibody delivery to organs such as the brain, gastrointestinal tract, and lungs, plus antibody developability challenges including immunogenicity risk assessment and mitigation and subcutaneous delivery. Machine learning has the potential, albeit as yet largely unrealized, for a transformative future impact on antibody discovery and engineering.