Novel Silyl Ether-Based Acid-Cleavable Antibody-MMAE Conjugates with Appropriate Stability and Efficacy

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.

Macrophage-derived CD36 + exosome subpopulations as novel biomarkers of Candida albicans infection

Invasive candidiasis (IC) is a notable healthcare-associated fungal infection, characterized by high morbidity, mortality, and substantial treatment costs. Candida albicans emerges as a principal pathogen in this context. Recent academic advancements have shed light on the critical role of exosomes in key biological processes, such as immune responses and antigen presentation. This burgeoning body of research underscores the potential of exosomes in the realm of medical diagnostics and therapeutics, particularly in relation to fungal infections like IC. The exploration of exosomal functions in the pathophysiology of IC not only enhances our understanding of the disease but also opens new avenues for innovative therapeutic interventions. In this investigation, we focus on exosomes (Exos) secreted by macrophages, both uninfected and those infected with C. albicans. Our objective is to extract and analyze these exosomes, delving into the nuances of their protein compositions and subgroups. To achieve this, we employ an innovative technique known as Proximity Barcoding Assay (PBA). This methodology is pivotal in our quest to identify novel biological targets, which could significantly enhance the diagnostic and therapeutic approaches for C. albicans infection. The comparative analysis of exosomal contents from these two distinct cellular states promises to yield insightful data, potentially leading to breakthroughs in understanding and treating this invasive fungal infection. In our study, we analyzed differentially expressed proteins in exosomes from macrophages and C. albicans -infected macrophages, focusing on proteins such as ACE2, CD36, CAV1, LAMP2, CD27, and MPO. We also examined exosome subpopulations, finding a dominant expression of MPO in the most prevalent subgroup, and a distinct expression of CD36 in cluster14. These findings are crucial for understanding the host response to C. albicans and may inform targeted diagnostic and therapeutic approaches. Our study leads us to infer that MPO and CD36 proteins may play roles in the immune escape mechanisms of C. albicans. Additionally, the CD36 exosome subpopulations, identified through our analysis, could serve as potential biomarkers and therapeutic targets for C. albicans infection. This insight opens new avenues for understanding the infection's pathology and developing targeted treatments.

Temozolomide nano-in-nanofiber delivery system with sustained release and enhanced cellular uptake by U87MG cells

OBJECTIVE

The study was aimed at formulating temozolomide (TMZ) loaded gelatin nanoparticles (GNPs) encapsulated into polyvinyl alcohol (PVA) nanofibers (TMZ-GNPs-PVA NFs) as the nano-in-nanofiber delivery system. The secondary objective was to explore the sustained releasing ability of this system and to assess its enhanced cellular uptake against U87MG glioma cells in vitro.

SIGNIFICANCE

Nano-in-nanofibers are the emerging drug delivery systems for treating a wide range of diseases including cancers as they overcome the challenges experienced by nanoparticles and nanofibers alone.

METHODS

The drug-loaded GNPs were formulated by one-step desolvation method. The Design of Experiments (DoE) was used to optimize nanoparticle size and entrapment efficiency. The optimized drug-loaded nanoparticles were then encapsulated within nanofibers using blend electrospinning technique. The U87MG glioma cells were used to investigate the uptake of the formulation.

RESULTS

A 32 factorial design was used to optimize the mean particle size (145.7 nm) and entrapment efficiency (87.6%) of the TMZ-loaded GNPs which were subsequently ingrained into PVA nanofibers by electrospinning technique. The delivery system achieved a sustained drug release for up to seven days (in vitro). The SEM results ensured that the expected nano-in-nanofiber delivery system was achieved. The uptake of TMZ-GNPs-PVA NFs by cells was increased by a factor of 1.964 compared to that of the pure drug.

CONCLUSION

The nano-in-nanofiber drug delivery system is a potentially useful therapeutic strategy for the management of glioblastoma multiforme.

Bispecific antibody drug conjugates: Making 1+1>2

Bispecific antibody‒drug conjugates (BsADCs) represent an innovative therapeutic category amalgamating the merits of antibody‒drug conjugates (ADCs) and bispecific antibodies (BsAbs). Positioned as the next-generation ADC approach, BsADCs hold promise for ameliorating extant clinical challenges associated with ADCs, particularly pertaining to issues such as poor internalization, off-target toxicity, and drug resistance. Presently, ten BsADCs are undergoing clinical trials, and initial findings underscore the imperative for ongoing refinement. This review initially delves into specific design considerations for BsADCs, encompassing target selection, antibody formats, and the linker-payload complex. Subsequent sections delineate the extant progress and challenges encountered by BsADCs, illustrated through pertinent case studies. The amalgamation of BsAbs with ADCs offers a prospective solution to prevailing clinical limitations of ADCs. Nevertheless, the symbiotic interplay among BsAb, linker, and payload necessitates further optimizations and coordination beyond a simplistic "1 + 1" to effectively surmount the extant challenges facing the BsADC domain.

Drug conjugates for the treatment of lung cancer: from drug discovery to clinical practice

A drug conjugate consists of a cytotoxic drug bound via a linker to a targeted ligand, allowing the targeted delivery of the drug to one or more tumor sites. This approach simultaneously reduces drug toxicity and increases efficacy, with a powerful combination of efficient killing and precise targeting. Antibody‒drug conjugates (ADCs) are the best-known type of drug conjugate, combining the specificity of antibodies with the cytotoxicity of chemotherapeutic drugs to reduce adverse reactions by preferentially targeting the payload to the tumor. The structure of ADCs has also provided inspiration for the development of additional drug conjugates. In recent years, drug conjugates such as ADCs, peptide‒drug conjugates (PDCs) and radionuclide drug conjugates (RDCs) have been approved by the Food and Drug Administration (FDA). The scope and application of drug conjugates have been expanding, including combination therapy and precise drug delivery, and a variety of new conjugation technology concepts have emerged. Additionally, new conjugation technology-based drugs have been developed in industry. In addition to chemotherapy, targeted therapy and immunotherapy, drug conjugate therapy has undergone continuous development and made significant progress in treating lung cancer in recent years, offering a promising strategy for the treatment of this disease. In this review, we discuss recent advances in the use of drug conjugates for lung cancer treatment, including structure-based drug design, mechanisms of action, clinical trials, and side effects. Furthermore, challenges, potential approaches and future prospects are presented.

Targeted Therapeutic Strategies for the Treatment of Cancer

Extensive research is underway to develop new therapeutic strategies to counteract therapy resistance in cancers. This review presents various strategies to achieve this objective. First, we discuss different vectorization platforms capable of releasing drugs in cancer cells. Second, we delve into multitarget therapies using drug combinations and dual anticancer agents. This section will describe examples of multitarget therapies that have been used to treat solid tumors.

Therapeutic Oligonucleotides: An Outlook on Chemical Strategies to Improve Endosomal Trafficking

The potential of oligonucleotide therapeutics is undeniable as more than 15 drugs have been approved to treat various diseases in the liver, central nervous system (CNS), and muscles. However, achieving effective delivery of oligonucleotide therapeutics to specific tissues still remains a major challenge, limiting their widespread use. Chemical modifications play a crucial role to overcome biological barriers to enable efficient oligonucleotide delivery to the tissues/cells of interest. They provide oligonucleotide metabolic stability and confer favourable pharmacokinetic/pharmacodynamic properties. This review focuses on the various chemical approaches implicated in mitigating the delivery problem of oligonucleotides and their limitations. It highlights the importance of linkers in designing oligonucleotide conjugates and discusses their potential role in escaping the endosomal barrier, a bottleneck in the development of oligonucleotide therapeutics.

A Novel Dual-Payload ADC for the Treatment of HER2+ Breast and Colon Cancer

Antibody-drug conjugates (ADCs) have demonstrated a great therapeutic potential against cancer due to their target specificity and cytotoxicity. To exert a maximum therapeutic effect on cancerous cells, we have conjugated two different payloads to different amino acids, cysteines (cys) and lysines (lys), on trastuzumab, which is a humanised anti-HER2 monoclonal antibody. First, trastuzumab was conjugated with monomethyl auristatin E (MMAE), an antimitotic agent, through a cleavable linker (Val-Cit) to prepare ADC (Tmab-VcMMAE). Then, the ADC (Tmab-VcMMAE) was conjugated with a second antimitotic agent, Mertansine (DM1), via a non-cleavable linker Succinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC) to form a dual conjugate (Tmab-VcMMAE-SMCC-DM1). Our results indicated that the dual-payload conjugate, Tmab-VcMMAE-SMCC-DM1, had a synergistic and superior cytotoxic effect compared to trastuzumab alone. Ultimately employing a dual conjugation approach has the potential to overcome treatment-resistance and tumour recurrences and could pave the way to employ other payloads to construct dual (or multiple) payload complexes.

Redefining Precision Management of r/r Large B-Cell Lymphoma: Novel Antibodies Take on CART and BMT in the Quest for Future Treatment Strategies

The treatment paradigms for patients with relapsed large B-cell lymphoma are expanding. Chimeric antigen receptor technology (CAR-T) has revolutionized the management of these patients. Novel bispecific antibodies and antibody-drug conjugates, used as chemotherapy-free single agents or in combination with other novel therapeutics, have been quickly introduced into the real-world setting. With such a paradigm shift, patients have an improved chance of better outcomes with unpredictable complete remission rates. Additionally, the excellent tolerance of new antibodies targeting B-cell lymphomas is another motivation to broaden its use in relapsed and refractory patients. With the increasing number of approved therapy approaches, future research needs to focus on optimizing the sequence and developing new combination strategies for these antibodies, both among themselves and with other agents. Clinical, pathological, and genetic risk profiling can assist in identifying which patients are most likely to benefit from these costly therapeutic options. However, new combinations may lead to new side effects, which we must learn to deal with. This review provides a comprehensive overview of the current state of research on several innovative antibodies for the precision management of large B-cell lymphoma. It explores various treatment strategies, such as CAR-T vs. ASCT, naked antibodies, antibody-drug conjugates, bispecific antibodies, and bispecific T-cell engagers, as well as discussing the challenges and future perspectives of novel treatment strategies. We also delve into resistance mechanisms and factors that may affect decision making. Moreover, each section provides a detailed analysis of the available literature and ongoing clinical trials.

The Dawn of a New Era: Targeting the "Undruggables" with Antibody-Based Therapeutics

The high selectivity and affinity of antibodies toward their antigens have made them a highly valuable tool in disease therapy, diagnosis, and basic research. A plethora of chemical and genetic approaches have been devised to make antibodies accessible to more "undruggable" targets and equipped with new functions of illustrating or regulating biological processes more precisely. In this Review, in addition to introducing how naked antibodies and various antibody conjugates (such as antibody-drug conjugates, antibody-oligonucleotide conjugates, antibody-enzyme conjugates, etc.) work in therapeutic applications, special attention has been paid to how chemistry tools have helped to optimize the therapeutic outcome (i.e., with enhanced efficacy and reduced side effects) or facilitate the multifunctionalization of antibodies, with a focus on emerging fields such as targeted protein degradation, real-time live-cell imaging, catalytic labeling or decaging with spatiotemporal control as well as the engagement of antibodies inside cells. With advances in modern chemistry and biotechnology, well-designed antibodies and their derivatives via size miniaturization or multifunctionalization together with efficient delivery systems have emerged, which have gradually improved our understanding of important biological processes and paved the way to pursue novel targets for potential treatments of various diseases.

pH-triggered cancer-targeting polymers: From extracellular accumulation to intracellular release

Stimuli-responsive polymers are promising to achieve targeted delivery, improved stability during circulation, and controlled release of therapeutic and diagnostic agents. Among them, pH-responsive polymeric nanocarriers have attracted significant attention as pH varies in different body fluids (e.g., stomach, intestine, and colon) and intracellular organelles (e.g., endosome, lysosome, and mitochondria) to maintain homeostasis, while distinctive pH changes are also found in certain pathological states. For example, the extracellular environment of the tumor is acidic, which can be employed to drive selective delivery. During the internalization process, since most nanocarriers enter cells upon endocytosis where a drop of pH from 6.5 to 5.0 can occur from endosome to lysosome, pH-sensitive groups have been developed for enhanced cargo release. In this review, both non-covalent and covalent interactions responsive to pH changes are introduced, with a focus on the structure-property relationship and their applications in cancer targeting and endosomal escape.

Synchronous intracellular delivery of EGFR-targeted antibody-drug conjugates by p38-mediated non-canonical endocytosis

Monoclonal antibodies targeting the epidermal growth factor receptor (EGFR), including cetuximab and panitumumab, have been used in clinic settings to treat cancer. They have also recently been applied to antibody–drug conjugates (ADCs); however, their clinical efficacy is limited by several issues, including lower internalization efficiency. The binding of cetuximab to the extracellular domain of EGFR suppresses ligand-induced events; therefore, we focus on ligand-independent non-canonical EGFR endocytosis for the delivery of ADCs into cells. Tumor necrosis factor-α (TNF-α) strongly induces the endocytosis of the cetuximab-EGFR complex within 15 min via the p38 phosphorylation of EGFR in a tyrosine kinase-independent manner. A secondary antibody conjugated with saporin, a ribosome-inactivating protein, also undergoes internalization with the complex and enhances its anti-proliferative activity. Anti-cancer agents, including cisplatin and temozolomide, also induce the p38-mediated internalization. The results of the present study demonstrate that synchronous non-canonical EGFR endocytosis may be a feasible strategy for promoting the therapeutic efficacy of EGFR-targeting ADCs in clinical settings.

New Technologies Bloom Together for Bettering Cancer Drug Conjugates

Drug conjugates, including antibody-drug conjugates, are a step toward realizing Paul Ehrlich's idea from over 100 years ago of a "magic bullet" for cancer treatment. Through balancing selective targeting molecules with highly potent payloads, drug conjugates can target specific tumor microenvironments and kill tumor cells. A drug conjugate consists of three parts: a targeting agent, a linker, and a payload. In some conjugates, monoclonal antibodies act as the targeting agent, but new strategies for targeting include antibody derivatives, peptides, and even small molecules. Linkers are responsible for connecting the payload to the targeting agent. Payloads impact vital cellular processes to kill tumor cells. At present, there are 12 antibody-drug conjugates on the market for different types of cancers. Research on drug conjugates is increasing year by year to solve problems encountered in conjugate design, such as tumor heterogeneity, poor circulation, low drug loading, low tumor uptake, and heterogenous expression of target antigens. This review highlights some important preclinical research on drug conjugates in recent years. We focus on three significant areas: improvement of antibody-drug conjugates, identification of new conjugate targets, and development of new types of drug conjugates, including nanotechnology. We close by highlighting the critical barriers to clinical translation and the open questions going forward. SIGNIFICANCE STATEMENT: The development of anticancer drug conjugates is now focused in three broad areas: improvements to existing antibody drug conjugates, identification of new targets, and development of new conjugate forms. This article focuses on the exciting preclinical studies in these three areas and advances in the technology that improves preclinical development.

Development of applicable thiol-linked antibody-drug conjugates with improved stability and therapeutic index

Maleimides are typically applicable for coupling with reactive thiol moieties of antibodies in antibody–drug conjugates (ADCs) via the thiol-Michael click chemistry. Even so, the thiosuccinimide group produced in ADCs is unstable under physiological conditions, which is a unresolved issue in the ADC industry that can cause serious off-target toxicity. Committed to solving the stability defects of traditional thiosuccinimide-containing ADCs, we explored a series of linkers based on the ring-opening hydrolysates of thiosuccinimide. Meanwhile, a type of linkers based on maleamic methyl ester were used to conjugate the popular monomethyl auristatin E to an anti-HER2 antibody to generate the target ADCs, which enhances the stability and do not need to change the structure of the ideal stable metabolite of traditional ADCs. In vivo studies demonstrate that our preferred ADC mil40-12b not only has better efficacy than traditional ADCs but also exhibits better safety parameters in mice. For example, complete tumor regression can still be achieved even when the dose is halved (2.5 mg/kg), and the maximum tolerable dose is increased by 40 mg/kg. This strategy is expected to provide an applicable tool for the construction of thiol-linked ADCs with improved therapeutic index.

Highly Efficient Synthesis of Poly(silylether)s: Access to Degradable Polymers from Renewable Resources

The design of new materials with tunable properties and intrinsic recyclability, derived from biomass under mild conditions, stands as a gold standard in polymer chemistry. Reported herein are platinum complexes which catalyze the formation of poly(silylether)s (PSEs) at low catalyst loadings. These polymers are directly obtained from dual-functional biobased building blocks such as 5-hydroxymethylfurfural (HMF) or vanillin, coupled with various dihydrosilanes. Access to different types of copolymer architectures (statistical or alternating) is highlighted by several synthetic strategies. The materials obtained were then characterized as low T_g materials (ranging from -60 to 29 °C), stable upon heating (T_-5% up to 301 °C) and resistant towards uncatalyzed methanolysis. Additionally, quantitative chemical recycling of several PSEs could be triggered by acid-catalyzed hydrolysis or methanolysis. These results emphasize the interest of biobased poly(silylether)s as sustainable materials with high recycling potential.

Antibody-drug conjugates: Recent advances in linker chemistry

Antibody–drug conjugates (ADCs) are gradually revolutionizing clinical cancer therapy. The antibody–drug conjugate linker molecule determines both the efficacy and the adverse effects, and so has a major influence on the fate of ADCs. An ideal linker should be stable in the circulatory system and release the cytotoxic payload specifically in the tumor. However, existing linkers often release payloads nonspecifically and inevitably lead to off-target toxicity. This defect is becoming an increasingly important factor that restricts the development of ADCs. The pursuit of ADCs with optimal therapeutic windows has resulted in remarkable progress in the discovery and development of novel linkers. The present review summarizes the advance of the chemical trigger, linker‒antibody attachment and linker‒payload attachment over the last 5 years, and describes the ADMET properties of ADCs. This work also helps clarify future developmental directions for the linkers.

Advances and Limitations of Antibody Drug Conjugates for Cancer

The popularity of antibody drug conjugates (ADCs) has increased in recent years, mainly due to their unrivalled efficacy and specificity over chemotherapy agents. The success of the ADC is partly based on the stability and successful cleavage of selective linkers for the delivery of the payload. The current research focuses on overcoming intrinsic shortcomings that impact the successful development of ADCs. This review summarizes marketed and recently approved ADCs, compares the features of various linker designs and payloads commonly used for ADC conjugation, and outlines cancer specific ADCs that are currently in late-stage clinical trials for the treatment of cancer. In addition, it addresses the issues surrounding drug resistance and strategies to overcome resistance, the impact of a narrow therapeutic index on treatment outcomes, the impact of drug-antibody ratio (DAR) and hydrophobicity on ADC clearance and protein aggregation.

Stimulus-cleavable chemistry in the field of controlled drug delivery

This review comprehensively summarises stimulus-cleavable linkers from various research areas and their cleavage mechanisms, thus provides an insightful guideline to extend their potential applications to controlled drug release from nanomaterials.

Development of HER2-Specific Aptamer-Drug Conjugate for Breast Cancer Therapy

In this study, HER2 RNA aptamers were conjugated to mertansine (DM1) and the anti-cancer effectiveness of the conjugate was evaluated in HER2-overexpressing breast cancer models. The conjugate of HER2 aptamer and anticancer drug DM1 (aptamer-drug conjugate, ApDC) was prepared and analyzed using HPLC and mass spectrometry. The cell-binding affinity and cytotoxicity of the conjugate were determined using confocal microscopy and WST-1 assay. The in vivo anti-tumoral efficacy of ApDC was also evaluated in mice carrying BT-474 breast tumors overexpressing HER2. The synthesized HER2-specific RNA aptamers were able to specifically and efficiently bind to HER-positive BT-474 breast cancer cells, but not to HER2-negative MDA-MB-231 breast cancer cells. Also, the HER2-specific ApDC showed strong toxicity to the target cells, BT-474, but not to MDA-MB-231 cells. According to the in vivo analyses drawn from the mouse xenografts of BT-747 tumor, the ApDC was able to more effectively inhibit the tumor growth. Compared to the control group, the mice treated with the ApDC showed a significant reduction of tumor growth. Besides, any significant body weight losses or hepatic toxicities were monitored in the ApDC-treated mice. This research suggests the HER2 aptamer-DM1 conjugate as a target-specific anti-cancer modality and provides experimental evidence supporting its enhanced effectiveness for HER2-overexpressing target tumors. This type of aptamer-conjugated anticancer drug would be utilized as a platform structure for the development of versatile targeted high-performance anticancer drugs by adopting the easy deformability and high affinity of aptamers.

Antibody-Drug Conjugate Using Ionized Cys-Linker-MMAE as the Potent Payload Shows Optimal Therapeutic Safety

Monomethyl auristatin E (MMAE) is the most popular and widely used cytotoxin in the development of antibody-drug conjugates (ADCs). However, current MMAE-based ADCs are all constructed using cleavable linkers, and this design concept still has insurmountable drawbacks. Their potential instabilities and lipophilic MMAE-induced “bystander effect” inevitably increase the toxicity to normal tissues. Herein, we overturn previous negative views of MMAE-based ADCs with non-cleavable linkers and propose using ionized L-Cysteine (Cys)-linker-MMAE as a novel payload, which can ingeniously enrich and enter tumor cells through receptor-mediated endocytosis of antibodies while its lower permeability helps to avoid further off-target toxicity. We demonstrate that Cys-linker-MMAE maintains high potency similar to free MMAE at the tubulin molecular level and can also be efficiently released in target cells. As a result, the preferred ADC (mil40-15) not only exhibits ideal plasma stability and maintains potent cytotoxicity as MMAE (IC₅₀: 10⁻¹¹ M), but also shows improved safety with lower bystander toxicity (IC₅₀: 10⁻⁹ M), its maximum tolerated dose approaching the level of the naked antibody (160 mg/kg). This study indicated that Cys-linker-MMAE has the potential as a potent payload for ADCs, which is expected to provide novel strategies for the development of MMAE-based ADCs.