Synthesis and biological evaluations of a monomethylauristatin E glucuronide prodrug for selective cancer chemotherapy

Balancing Reactivity and Specificity: Fc-Binding O-Acyl Hydroxamate Reagents for Site-Selective Antibody Labeling at Lys248

We report the design and synthesis of O-acyl hydroxamates (OAHs) affinity labels for selective modification of human IgG1 at Lys248 via proximity-driven acylation. Optimized compound 7g exhibits high water stability and >99% site-selective conversion at Lys248 on Trastuzumab using only 3 equiv. Peptide mapping and fluorescence labeling confirm its precision, establishing 7g as a robust platform for efficient and site-selective antibody conjugation.

Dual-Targeting of the HER2 Cancer Receptor with an Antibody-Directed Enzyme and a Nanobody-Guided MMAE Prodrug Scaffold

Antibody-enzyme conjugates have shown potential as tissue-specific prodrug activators by antibody-directed enzyme prodrug therapy (ADEPT), but the approach met challenges clinically due to systemic drug release. Here, we report a novel dual-targeting ADEPT system (DuADEPT) which is based on active cancer receptor targeting of both a trastuzumab-sialidase conjugate (Tz-Sia) and a highly potent sialidase-activated monomethyl auristatin E (MMAE) prodrug scaffold. The scaffold is based on a four-way junction of the artificial nucleic acid analog acyclic (L)-threoninol nucleic acid ((L)-aTNA) which at the ends of its four arms carries one nanobody targeting HER2 and three copies of the prodrug. Dual-targeting of the constructs to two proximal epitopes of HER2 was shown by flow cytometry, and a dual-targeted enzymatic drug release assay revealed cytotoxicity upon prodrug activation specifically for HER2-positive cancer cells. The specific delivery and activation of prodrugs in this way could potentially be used to decrease systemic side effects and increase drug efficacy, and utilization of Tz-Sia provides an opportunity to combine the local chemotherapeutic effect of the DuADEPT with an anticancer immune response.

An Enzyme-Responsive Self-Immolative Recognition Marker for Manipulating Cell-Cell Interactions

The development of innovative strategies for cell membranes engineering is of prime interest to explore and manipulate cell-cell interactions. Herein, an enzyme-sensitive recognition marker that can be introduced on cell surface via bioorthogonal chemistry is designed. Once functionalized in this fashion, the cells gain the ability to assemble with cell partners coated with the complementary marker through non-covalent click chemistry. The artificial cell adhesion induces natural biological processes associated with cell proximity such as inhibiting cancer cell proliferation and migration. On the other hand, the enzymatic activation of the stimuli-responsive marker triggers the disassembly of cells, thereby restoring the tumor cell proliferation and migration rates. Thus, the study shows that the ready-to-use complementary markers are valuable tools for controlling the formation and the breaking of bonds between cells, offering an easy way to investigate biological processes associated to cell proximity.

Design, synthesis of auristatins-glucuronide conjugates targeting the β-glucuronidase in tumor microenvironment

Auristatins-glucuronide conjugates designed targeting the β-Glucuronidase in tumor microenvironment were synthesized and evaluated on stabilities, the release of auristatins and the antitumor activities in this study. Conjugates 20 and 21 showed remarkable stabilities in phosphate buffer and bovine serum solution, and excellent selectivity between the in vitro antiproliferative activities against β-glucuronidase pretreated and untreated cancer cells (IC50 = 5.7 nM ∼ 9.7 nM, IC50 (-Enz) > 1 μM). Furthermore, conjugate 20 showed potent antitumor efficacy in HCT-116 xenograft mouse model without inducing side effects.

Anti-tumor effects of novel alkannin derivatives with potent selectivity on comprehensive analysis

BACKGROUND

Therapeutic approaches based on glycolysis and energy metabolism of tumor cells are new promising strategies for the treatment of cancer. Currently, researches on the inhibition of pyruvate kinase M2, a key rate limiting enzyme in glycolysis, have been corroborated as an effective cancer therapy. Alkannin is a potent pyruvate kinase M2 inhibitor. However, its non-selective cytotoxicity has affected its subsequent clinical application. Thus, it needs to be structurally modified to develop novel derivatives with high selectivity.

PURPOSE

Our study aimed to ameliorate the toxicity of alkannin through structural modification and elucidate the mechanism of the superior derivative 23 in lung cancer therapy.

METHODS

On the basis of the principle of collocation, different amino acids and oxygen-containing heterocycles were introduced into the hydroxyl group of the alkannin side chain. We examined the cell viability of all derivatives on three tumor cells (HepG2, A549 and HCT116) and two normal cells (L02 and MDCK) by MTT assay. Besides, the effect of derivative 23 on the morphology of A549 cells as observed by Giemsa and DAPI staining, respectively. Flow cytometry was performed to assess the effects of derivative 23 on apoptosis and cell cycle arrest. To further assess the effect of derivative 23 on the Pyruvate kinase M2 in glycolysis, an enzyme activity assay and western blot assay were performed. Finally, in vivo the antitumor activity and safety of the derivative 23 were evaluated by using Lewis mouse lung cancer xenograft model.

RESULTS

Twenty-three novel alkannin derivatives were designed and synthesized to improve the cytotoxicity selectivity. Among these derivatives, derivative 23 showed the highest cytotoxicity selectivity between cancer and normal cells. The anti-proliferative activity of derivative 23 on A549 cells (IC₅₀ = 1.67 ± 0.34 μM) was 10-fold higher than L02 cells (IC₅₀ = 16.77 ± 1.44 μM) and 5-fold higher than MDCK cells (IC₅₀ = 9.23 ± 0.29 μM) respectively. Subsequently, fluorescent staining and flow cytometric analysis showed that derivative 23 was able to induce apoptosis of A549 cells and arrest the cell cycle in the G0/G1 phase. In addition, the mechanistic studies suggested derivative 23 was an inhibitor of pyruvate kinase; it could regulate glycolysis by inhibiting the activation of the phosphorylation of PKM2/STAT3 signaling pathway. Furthermore, studies in vivo demonstrated derivative 23 significantly inhibited the growth of xenograft tumor.

CONCLUSION

In this study, alkannin selectivity is reported to be significantly improved following structural modification, and derivative 23 is first shown to be able to inhibit lung cancer growth via the PKM2/STAT3 phosphorylation signaling pathway in vitro, indicating the potential value of derivative 23 in treating lung cancer.

A Novel Antibody-Drug Conjugate Targeting Nectin-2 Suppresses Ovarian Cancer Progression in Mouse Xenograft Models

Ovarian cancer is the fifth leading cause of cancer, followed by front line is mostly platinum agents and PARP inhibitors, and very limited option in later lines. Therefore, there is a need for alternative therapeutic options. Nectin-2, which is overexpressed in ovarian cancer, is a known immune checkpoint that deregulates immune cell function. In this study, we generated a novel anti-nectin-2 antibody (chimeric 12G1, c12G1), and further characterized it using epitope mapping, enzyme-linked immunosorbent assay, surface plasmon resonance, fluorescence-activated cell sorting, and internalization assays. The c12G1 antibody specifically bound to the C2 domain of human nectin-2 with high affinity (K_D = 2.90 × 10^-10 M), but not to mouse nectin-2. We then generated an antibody-drug conjugate comprising the c12G1 antibody conjugated to DM1 and investigated its cytotoxic effects against cancer cells in vitro and in vivo. c12G1-DM1 induced cell cycle arrest at the mitotic phase in nectin-2-positive ovarian cancer cells, but not in nectin-2-negative cancer cells. c12G1-DM1 induced ~100-fold cytotoxicity in ovarian cancer cells, with an IC₅₀ in the range of 0.1 nM~7.4 nM, compared to normal IgG-DM1. In addition, c12G1-DM1 showed ~91% tumor growth inhibition in mouse xenograft models transplanted with OV-90 cells. These results suggest that c12G1-DM1 could be used as a potential therapeutic agent against nectin-2-positive ovarian cancers.

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.

Quiescent B Cells Acquire Sensitivity to Cell Cycle Arresting Agents by B Cell Receptor Stimulation

For the treatment of autoimmune diseases, depletion of B cells specific for auto-antigens is important because they will be a source of plasmablasts/plasma cells to produce autoantibodies. However, because some types of B cells like naïve B cells and memory B cells are at quiescent phase, they are insensitive to anticancer drugs which exert cytotoxicity by arresting the cell cycle. Here we show that B cell receptor (BCR) stimulation increases the sensitivity of anticancer drugs by promoting the proliferation of quiescent B cells. The BCR stimulation to primary naïve B cells enhanced sensitivity to several anticancer drugs which arrest the cell cycle through different mechanisms. The present results indicated that combination of the BCR stimulation and anticancer drugs is a promising strategy for the antigen-specific depletion of pathogenic quiescent B cells.

Glycosidase activated prodrugs for targeted cancer therapy

In this review glycosidase activated prodrugs that target cancer cells are discussed.

Stimulus-cleavable chemistry in the field of controlled drug delivery

Stimulus-cleavable nanoscale drug delivery systems are receiving significant attention owing to their capability of achieving exquisite control over drug release via the exposure to specific stimuli. Central to the construction of such systems is the integration of cleavable linkers showing susceptibility to one stimulus or several stimuli with drugs, prodrugs or fluorogenic probes on the one hand, and nanocarriers on the other hand. This review summarises recent advances in stimulus-cleavable linkers from various research areas and the corresponding mechanisms of linker cleavage and biological applications. The feasibility of extending their applications to the majority of nanoscale drug carriers including nanomaterials, polymers and antibodies are further highlighted and discussed. This review also provides general design guidelines to incorporate stimulus-cleavable linkers into nanocarrier-based drug delivery systems, which will hopefully spark new ideas and applications.

Introduction of an Aldehyde Handle on Nanobodies by Affinity-Guided Labeling

Chemically modified antigen-binding proteins are widely applied for their targeting abilities in the fields of biotechnology, medicine, and diagnostics. However, the production of site-selectively modified proteins remains a challenge. Here, we have designed a chemical probe for the introduction of a reactive aldehyde on nanobodies by metal-complex-guided conjugation. The probe design allows for purification of the conjugates, and the aldehyde constitutes an efficient handle for further modification of the nanobodies. In vitro experiments confirmed the binding activity and selectivity of fluorescent conjugates toward the native antigen. Furthermore, the modification strategy allowed for production of a nanobody-drug conjugate that was active in vitro.

Development of an embedded multimodality imaging platform for onco-pharmacology using a smart anticancer prodrug as an example

Increasingly, in vivo imaging holds a strategic position in bio-pharmaceutical innovation. We will present the implementation of an integrated multimodal imaging setup enabling the assessment of multiple, complementary parameters. The system allows the fusion of information provided by: Near infrared fluorescent biomarkers, bioluminescence (for tumor proliferation status), Photoacoustic and Ultrasound imaging. We will study representative applications to the development of a smart prodrug, delivering a highly cytotoxic chemotherapeutic agent to cancer tumors. The results realized the ability of this embedded, multimodality imaging platform to firstly detect bioluminescent and fluorescent signals, and secondly, record ultrasound and photoacoustic data from the same animal. This study demonstrated that the prodrug was effective in three different models of hypoxia in human cancers compared to the parental cytotoxic agent and the vehicle groups. Monitoring by photoacoustic imaging during the treatments revealed that the prodrug exhibits an intrinsic capability to prevent the progression of tumor hypoxia. It is essential for onco-pharmacology studies to precisely document the hypoxic status of tumors both before and during the time course of treatments. This approach opens new perspectives for exploitation of preclinical mouse models of cancer, especially when considering associations between hypoxia, neoangiogenesis and antitumor activity.

Monitoring glycosidase activity for clustered sugar substrates, a study on β-glucuronidase

Enzymatically-triggered probes to determine glucuronidase hydrolysis kinetics for clustered substrates.

Prodrugs in medicinal chemistry and enzyme prodrug therapies

Prodrugs are cunning derivatives of therapeutic agents designed to improve the pharmacokinetics profile of the drug. Within a prodrug, pharmacological activity of the drug is masked and is recovered within the human body upon bioconversion of the prodrug, a process that is typically mediated by enzymes. This concept is highly successful and a significant fraction of marketed therapeutic formulations is based on prodrugs. An advanced subset of prodrugs can be engineered such as to achieve site-specific bioconversion of the prodrug - to comprise the highly advantageous "enzyme prodrug therapy", EPT. Design of prodrugs for EPT is similar to the prodrugs in general medicinal use in that the pharmacological activity of the drug is masked, but differs significantly in that site-specific bioconversion is a prime consideration, and the enzymes typically used for EPT are non-mammalian and/or with low systemic abundance in the human body. This review focuses on the design of prodrugs for EPT in terms of the choice of an enzyme and the corresponding prodrug for bioconversion. We also discuss the recent success of "self immolative linkers" which significantly empower and diversify the prodrug design, and present methodologies for the design of prodrugs with extended blood residence time. The review aims to be of specific interest for medicinal chemists, biomedical engineers, and pharmaceutical scientists.

Targeting the tumour microenvironment with an enzyme-responsive drug delivery system for the efficient therapy of breast and pancreatic cancers

The development of novel therapeutic strategies allowing the destruction of tumour cells while sparing healthy tissues is one of the main challenges of cancer chemotherapy. Here, we report on the design and antitumour activity of a low-molecular-weight drug delivery system programmed for the selective release of the potent monomethylauristatin E in the tumour microenvironment of solid tumours. After intravenous administration, this compound binds covalently to plasmatic albumin through Michael addition, thereby enabling its passive accumulation in tumours where extracellular β-glucuronidase initiates the selective release of the drug. This targeting device produces outstanding therapeutic efficacy on orthotopic triple-negative mammary and pancreatic tumours in mice (50% and 33% of mice with the respective tumours cured), leading to impressive reduction or even disappearance of tumours without inducing side effects.

Antineoplastic agents. 600. From the South Pacific Ocean to the silstatins

The recent advances in the development of antibody and other drug conjugates for targeted cancer treatment have further increased the need for powerful cancer cell growth inhibitors. Toward that objective we have extended our earlier discovery of the remarkable anticancer bacillistatins 1 and 2 from Bacillus silvestris to SAR and other structural modifications such as availability of a free hydroxy group for antibody-drug conjugate (ADC) and other prodrug linkage. That direction has resulted in seven structural modifications designated silstatins 1-8 (7a, 8a, 8b, 14a, 15a, 15b, 18a, and 18b), where the exceptional cancer cell growth inhibition of some of them are in the range GI50 10(-3)-10(-4) μM/mL. Silstatin 7 (18a) was converted to a glucuronic conjugate (28) that displayed an impressive reduction in toxicity during transport.

β-Glucuronidase-responsive prodrugs for selective cancer chemotherapy: an update

The design of novel antitumor agents allowing the destruction of malignant cells while sparing healthy tissues is one of the major challenges in medicinal chemistry. In this context, the use of non-toxic prodrugs programmed to be selectively activated by beta-glucuronidase present at high concentration in the microenvironment of most solid tumors has attracted considerable attention. This review summarizes the major progresses that have been realized in this field over the past ten years. This includes the new prodrugs that have been designed to target a wide variety of anticancer drugs, the prodrugs employed in the course of a combined therapy, the dendritic glucuronide prodrugs and the concept of β-glucuronidase-responsive albumin binding prodrugs.

The Escherichia coli glucuronylsynthase promoted synthesis of steroid glucuronides: improved practicality and broader scope

Steroid glucuronides can be quickly and conveniently prepared on the milligram scale using theE. coliglucuronylsynthase enzyme followed by purification with solid-phase extraction.