Antibody-drug conjugates: What drives their progress?

Recent doxorubicin-conjugates in cancer drug delivery: Exploring conjugation strategies for enhanced efficacy and reduced toxicity

Doxorubicin is a first-line treatment of cancer that works on the mechanism of DNA intercalation and topoisomerase II poisoning. Since the 20th century, Doxorubicin has been used as a promising drug to treat several types of cancer, both solid or metastatic, including breast, thyroid, bladder, ovarian, or gastric cancer, etc. Even though it shows promising effects on cancer cells, it also shows its effects on healthy cells with cancerous cells, which leads to several severe side effects, such as cardiomyopathy, phlebitis, congestive heart failure (CHF), etc., which limits its usage in chemotherapy. Several research has focused on the targeted delivery of doxorubicin to cancerous cells to reduce side effects and improve efficacy. To optimize its anticancer potential, scientists have recently been developing nano-formulations and investigating various conjugations. The structure of doxorubicin consists of two primary functional groups that can be employed for conjugation with a variety of biomolecules, The first is the primary amine group in a sugar moiety, and the other one is the primary hydroxyl group in the aliphatic chain ring. In this paper, we have mentioned several conjugations of doxorubicin such as antibodies, nanoparticles, polymers, and phytochemical conjugations. Different studies regarding these conjugations are also mentioned, which represent promising strategies to optimize cancer treatment by minimizing side effects.

Clinical strategies with antibody-drug conjugates as potential modifications for virotherapy

The ability to selectively target cancer cells makes antibody-drug conjugates (ADCs) promising therapeutic options. They have been tested in clinical trials as a vehicle for tumor-specific delivery of cytotoxic payloads for a range of cancers. However, systemic administration of oncolytic virotherapy is challenging, because only a small portion of injected viruses reach the target. Despite the approval of higher viral doses, most viruses still end up in the liver, potentially causing toxicity in that organ. Integrating ADCs with virotherapy in the form of antibody-virus conjugates or virus-drug conjugates can potentially overcome these challenges and improve therapeutic outcomes.

Recent Advances in Targeted Cancer Therapy: Are PDCs the Next Generation of ADCs?

Antibody-drug conjugates (ADCs) comprise antibodies, cytotoxic payloads, and linkers, which can integrate the advantages of antibodies and small molecule drugs to achieve targeted cancer treatment. However, ADCs also have some shortcomings, such as non-negligible drug resistance, a low therapeutic index, and payload-related toxicity. Many studies have focused on changing the composition of ADCs, and some have even further extended the concept and types of targeted conjugated drugs by replacing the targeted antibodies in ADCs with peptides, revolutionarily introducing peptide-drug conjugates (PDCs). This Perspective summarizes the current research status of ADCs and PDCs and highlights the structural innovations of ADC components. In particular, PDCs are regarded as the next generation of potential targeted drugs after ADCs, and the current challenges of PDCs are analyzed. Our aim is to offer fresh insights for the efficient design and expedited development of innovative targeted conjugated drugs.

Antibody-Drug Conjugates-Evolution and Perspectives

Antineoplastic therapy is one of the main research themes of this century. Modern approaches have been implemented to target and heighten the effect of cytostatic drugs on tumors and diminish their general/unspecific toxicity. In this context, antibody-drug conjugates (ADCs) represent a promising and successful strategy. The aim of this review was to assess different aspects regarding ADCs. They were presented from a chemical and a pharmacological perspective and aspects like structure, conjugation and development particularities alongside effects, clinical trials, safety issues and perspectives and challenges for future use of these drugs were discussed. Representative examples include but are not limited to the following main structural components of ADCs: monoclonal antibodies (trastuzumab, brentuximab), linkers (pH-sensitive, reduction-sensitive, peptide-based, phosphate-based, and others), and payloads (doxorubicin, emtansine, ravtansine, calicheamicin). Regarding pharmacotherapy success, the high effectiveness expectation associated with ADC treatment is supported by the large number of ongoing clinical trials. Major aspects such as development strategies are first discussed, advantages and disadvantages, safety and efficacy, offering a retrospective insight on the subject. The second part of the review is prospective, focusing on various plans to overcome the previously identified difficulties.

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.

Living virus-based nanohybrids for biomedical applications

Living viruses characterized by distinctive biological functions including specific targeting, gene invasion, immune modulation, and so forth have been receiving intensive attention from researchers worldwide owing to their promising potential for producing numerous theranostic modalities against diverse pathological conditions. Nevertheless, concerns during applications, such as rapid immune clearance, altering immune activation modes, insufficient gene transduction efficiency, and so forth, highlight the crucial issues of excessive therapeutic doses and the associated biosafety risks. To address these concerns, synthetic nanomaterials featuring unique physical/chemical properties are frequently exploited as efficient drug delivery vehicles or treatments in biomedical domains. By constant endeavor, researchers nowadays can create adaptable living virus-based nanohybrids (LVN) that not only overcome the limitations of virotherapy, but also combine the benefits of natural substances and nanotechnology to produce novel and promising therapeutic and diagnostic agents. In this review, we discuss the fundamental physiochemical properties of the viruses, and briefly outline the basic construction methodologies of LVN. We then emphasize their distinct diagnostic and therapeutic performances for various diseases. Furthermore, we survey the foreseeable challenges and future perspectives in this interdisciplinary area to offer insights. This article is categorized under: Biology-Inspired Nanomaterials > Protein and Virus-Based Structures Therapeutic Approaches and Drug Discovery > Emerging Technologies.

A novel antibody-KSP inhibitor conjugate improves KSP inhibitor efficacy in vitro and in vivo

Many clinical trials of kinesin spindle protein (KSP) inhibitors have failed due to issues such as high toxicity and a short circulation half-life in vivo. To address the limitations of current KSP inhibitors and thus broad its use in antitumor therapy, this study applied antibody-drug conjugate (ADC) technology to the KSP inhibitor SB-743921, which was coupled with the HER2-specific antibody trastuzumab using a cathepsin B-dependent valine-alanine (Val-Ala, VA) dipeptide-type linker to generate H2-921. Ex vivo and in vivo analyses of H2-921 showed an increased half-life of SB-743921 and prolonged contact time with tumor cells. Furthermore, H2-921 induced apoptosis and incomplete autophagy in HER2-positive cells. In the in vivo analyses, H2-921 had significant tumor-targeting properties, and tumor inhibition by H2-921 was greater than that by traditional KSP inhibitors but similar to that by the positive control drug T-DM1. In conclusion, this study describes a novel application of ADC technology that enhances the antitumor effects of a KSP inhibitor and thus may effectively address the poor clinical efficacy of KSP inhibitors.

Combination of Targeted Therapies for Colorectal Cancer Treatment

The design of innovative therapeutic strategies enabling the selective destruction of tumor cells while sparing healthy tissues remains highly challenging in cancer therapy. Here, we show that the combination of two targeted therapies, including bevacizumab (Bev), and a β-glucuronidase-responsive albumin-binding prodrug of monomethyl auristatin E (MMAE), is efficient for the treatment of colorectal cancer implanted in mice. This combined therapy produces a therapeutic activity superior to that of the association of FOLFOX and Bev currently used to treat patients with this pathology. The increased anticancer efficacy is due to either a synergistic or an additive effect between Bev and MMAE selectively released from the glucuronide prodrug in the tumor microenvironment. Since numerous drug delivery systems such as antibody-drug conjugates employ MMAE as a cytotoxic payload, this finding may be of great interest for improving their therapeutic index by combining them with Bev, particularly for the therapy of colorectal cancer.

Current and preclinical treatment options for Merkel cell carcinoma

INTRODUCTION

Merkel cell carcinoma (MCC) is a rare, highly aggressive form of skin cancer with neuroendocrine features. The origin of this cancer is still unclear, but research in the last 15 years has demonstrated that MCC arises via two distinct etiologic pathways, i.e. virus and UV-induced. Considering the high mortality rate and the limited therapeutic options available, this review aims to highlight the significance of MCC research and the need for advancement in MCC treatment.

AREAS COVERED

With the advent of the immune checkpoint inhibitor therapies, we now have treatment options providing a survival benefit for patients with advanced MCC. However, the issue of primary and acquired resistance to these therapies remains a significant concern. Therefore, ongoing efforts seeking additional therapeutic targets and approaches for MCC therapy are a necessity. Through a comprehensive literature search, we provide an overview on recent preclinical and clinical studies with respect to MCC therapy.

EXPERT OPINION

Currently, the only evidence-based therapy for MCC is immune checkpoint blockade with anti-PD-1/PD-L1 for advanced patients. Neoadjuvant, adjuvant and combined immune checkpoint blockade are promising treatment options.

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.

Detection and Characterization of In Vitro Payload-Containing Catabolites of Noncleavable Antibody-Drug Conjugates by High-Resolution Mass Spectrometry and Multiple Data Mining Tools

The formation and accumulation of payload-containing catabolites (PCCs) from a noncleavable antibody-drug conjugate (ADC) in targeted and normal tissues are directly associated with the therapeutic effect and toxicity of the ADC, respectively. Understanding the PCC formation is important for supporting the payload design and facilitating preclinical evaluation of ADCs. However, detection and identification of PCCs of a noncleavable ADC are challenging due to their low concentrations and unknown structures. The main objective of this study was to develop and apply a generic liquid chromatography-high-resolution mass spectrometry (LC-HRMS) method for profiling PCCs in vitro. Noncleavable ADCs, ado-trastuzumab emtansine (T-DM1) and ADC-1, were incubated in liver lysosomes, liver S9, and/or cancer cells followed by data acquisition using LC-HRMS. Profiling PCCs mainly relied on processing LC-HRMS datasets using untargeted precise and thorough background subtraction (PATBS) processing and targeted product ion filtering (PIF). As a result, 12 PCCs of T-DM1 were detected and structurally characterized in human liver lysosomal incubation, a majority of which consisted of 4-[N-maleimidomethyl]cyclohexane-1-carboxylate (MCC)-DM1 and a few amino acids. Additionally, the incubation of ADC-1 in human, rat, and monkey liver S9 and cancer cells generated one major and three very minor PCCs, verifying the payload design. The results demonstrate that PATBS enabled the comprehensive profiling of PCCs regardless of their molecular weights, charge states, and fragmentations. As a complementary tool, PIF detected specific PCCs with superior sensitivity. The combination of the in vitro metabolism systems and the LC-HRMS method is a useful approach to profiling in vitro PCCs of noncleavable ADCs in support of drug discovery programs. SIGNIFICANCE STATEMENT: Profiling in vitro payload-containing catabolites (PCCs) of a noncleavable antibody-drug conjugate (ADC) is important for optimization of the payload design and preclinical evaluation of ADC. However, currently used analytical approaches often fail to quickly provide reliable PCC profiling results. The work introduces a new liquid chromatography high resolution mass spectrometry method for comprehensive and rapid detection and characterization of PCCs released from a noncleavable ADC in liver lysosomes and S9 incubations.

Generation of DAR1 Antibody-Drug Conjugates for Ultrapotent Payloads Using Tailored GlycoConnect Technology

GlycoConnect technology can be readily adapted to provide different drug-to-antibody ratios (DARs) and is currently also evaluated in various clinical programs, including ADCT-601 (DAR2), MRG004a (DAR4), and XMT-1660 (DAR6). While antibody-drug conjugates (ADCs) typically feature a DAR2-8, it has become clear that ADCs with ultrapotent payloads (e.g., PBD dimers and calicheamicin) can only be administered to patients at low doses (<0.5 mg/kg), which may compromise effective biodistribution and may be insufficient to reach target receptor saturation in the tumor. Here, we show that GlycoConnect technology can be readily extended to DAR1 ADCs without the need of antibody re-engineering. We demonstrate that various ultrapotent, cytotoxic payloads are amenable to this methodology. In a follow-up experiment, HCC-1954 tumor spheroids were treated with either an AlexaFluor647-labeled DAR1 or DAR2 PBD-based ADC to study the effect on tumor penetration. Significant improvement of tumor spheroid penetration was observed for the DAR1 ADC compared to the DAR2 ADC at an equal payload dose, underlining the potential of a lower DAR for ADCs bearing ultrapotent payloads.

The Chemistry of Creating Chemically Programmed Antibodies (cPAbs): Site-Specific Bioconjugation of Small Molecules

Small-molecule drugs have been employed for years as therapeutics in the pharmaceutical industry. However, small-molecule drugs typically have short in vivo half-lives which is one of the largest impediments to the success of many potentially valuable pharmacologically active small molecules. The undesirable pharmacokinetics and pharmacology associated with some small molecules have led to the development of a new class of bioconjugates known as chemically programmed antibodies (cPAbs). cPAbs are bioconjugates in which antibodies are used to augment small molecules with effector functions and prolonged pharmacokinetic profiles, where the pharmacophore of the small molecule is harnessed for target binding and therefore biological targeting. Many different small molecules can be conjugated to large proteins such as full monoclonal antibodies (IgG), fragment crystallizable regions (Fc), or fragment antigen binding regions (Fab). In order to successfully and site-specifically conjugate small molecules to any class of antibodies (IgG, Fc, or Fab), the molecules must be derivatized with a functional group for ease of conjugation without altering the pharmacology of the small molecules. In this Review, we summarize the different synthetic or biological methods that have been employed to produce cPAbs. These unique chemistries have potential to be applied to other fields of antibody modification such as antibody drug conjugates, radioimmunoconjugates, and fluorophore-tagged antibodies.

Glucuronides: From biological waste to bio-nanomedical applications

Long considered as no more than biological waste meant to be eliminated in urine, glucuronides have recently contributed to tremendous developments in the biomedical field, particularly against cancer. While glucuronide prodrugs monotherapy and antibody-directed enzyme prodrug therapy have been around for some time, new facets have emerged that combine the unique properties of glucuronides notably in the fields of antibody-drug conjugates and nanomedicine. In both cases, glucuronides are utilized as a vector to improve pharmacokinetics and confer localized activation of potent drugs at tumor sites while also decreasing systemic toxicity. Here we will discuss some of the most promising strategies using glucuronides to promote successful anti-tumor therapeutic treatments.