Catalytic detoxification of mitoxantrone by graphitic carbon nitride (g-C3N4) supported Fe/Pd bimetallic nanoparticles.

The overuse of antibiotics and antitumor drugs has resulted in more and more extensive pollution of water bodies with organic drugs, causing detrimental ecological effects, which have attracted attention towards effective and sustainable methods for antibiotics and antitumor drug degradation. Here, the hybrid nanomaterial (g-C3N4@Fe/Pd) was synthesized and used to remove a kind of both an antibiotic and antitumor drug named mitoxantrone (MTX) with 92.0% removal efficiency, and the MTX removal capacity is 450 mg/g. After exposing to the hybrid material the MTX aqueous solution changed color from dark blue to lighter progressively, and LC-UV results of residual solutions show that a new peak at 3.0 min (MTX: 13.2 min) after removal by g-C3N4@Fe/Pd appears, with the simultaneous detection of intermediate products indicating that g-C3N4@Fe/Pd indeed degrades MTX. Detailed mass spectrometric analysis suggests that the nuclear mass ratio decreased from 445.2 (M+1H) to 126.0 (M+1H), 169.1 (M+1H), 239.2 (M+1H), 267.3 (M+1H), 285.2 (M+1H), 371.4 (M+1H) and 415.2 (M+1H), and the maximum proportion (5.63%) substance of all degradation products (126.0 (M+1H)) is 40-100 times less toxic than MTX. A mechanism for the removal and degradation of mitoxantrone was proposed. Besides, actual water experiments confirmed that the maximum removal capacity of MTX by g-C3N4@Fe/Pd is up to 492.4 mg/g (0.02 g/L, 10 ppm).

Pt/Pd dual-modified porphyrin metal-organic frameworks for NIR-II photothermal-enhanced photodynamic/catalytic therapy.

Photodynamic therapy (PDT) and catalytic therapy were promising treatment modes, but tumor hypoxia and poor catalytic activity severely limited their efficacies. Herein, using a porphyrin metal-organic framework (PCN-224) as nanocarrier, a platinum/palladium (Pt/Pd) dual-modified PCN-224 nanoprobe (PCN-224-Pt@Pd) with strong peroxidase (POD)/catalase (CAT)-like activities was developed, achieving photothermal-promoted PDT/catalytic therapy. Compared with single ultrasmall Pt modifying, CAT-like activity of Pt/Pd dual-modifying increased oxygen concentration from 6.24 to 9.35 mg/L, which improved singlet oxygen (1O2) yield from 63.8 % to 82.9 %. Moreover, POD-like activity of Pt/Pd dual-modifying significantly accelerated hydroxyl radicals (·OH) generation. Importantly, PCN-224-Pt@Pd possessed near-infrared II (NIR-II) photothermal effect with a high efficiency (55.6 %), which further promoted ·OH production. Under combined therapy of PCN-224-Pt@Pd, the cell survival rate greatly reduced to 5.8 %, and the tumors were cured, suggesting NIR-II photothermal-enhanced PDT/catalytic therapy.

Supramolecular palladium complexes based on guanidinium pillar[5]arene for cancer therapy.

The supramolecular palladium complex G-Pd, formed via self-assembly of the Pd-complex of guanidinium pillar[5]arene with Pd2+, was used to encapsulate doxorubicin to form G-Pd@DOX. The nanoparticles exhibit responsiveness to glutathione, controlled drug release, the ability to damage mitochondria, and potent anticancer activity while maintaining low toxicity towards normal cells. This work provides a good example for the application of pillararene-based palladium complexes in cancer therapy and is significant for the discovery of new medicines from supramolecular coordination complexes.

Late-Stage Modification of Peptides with Maleimides through Palladium-Catalyzed ß-C(sp3)-H Alkylation.

Transition-metal-catalyzed C-H activation has proven to be a powerful tool for the late-stage modification of peptides. We herein report a method for site-selective alkylation of peptides with maleimides through Pd-catalyzed ß-C(sp3)-H activation. In this protocol, the methionine residues within peptides serve as the directing groups, which circumvented the preinstallation and subsequent removal of the directing groups. This chemistry exhibited broad substrate scope and can be utilized for peptide ligation.

Three-in-One Nanozyme for Radiosensitization of Bladder Cancer.

Purpose: Bladder cancer is a common malignancy of the urinary system and the development of noninvasive therapeutic methods is imperative to avoid radical cystectomy, which results in a poor quality of life for patients. Methods: In this study, ultrasmall copper-palladium nanozymes decorated with cysteamine (CPC) nanoparticles (NPs) were synthesized to enhance the efficacy of radiotherapy (RT) in treating bladder cancer. CPC NPs react with intracellular overexpressed H2O2 in the tumor microenvironment to produce large quantities of reactive oxygen species (ROS) and induce tumor cell apoptosis. Furthermore, the CPC nanozymes can generate ample oxygen within tumors by utilizing H2O2, addressing hypoxia conditions, and mitigating radioresistance. Additionally, CPC facilitates the oxidation of glutathione (GSH) into oxidized glutathione disulfide (GSSG), blocking the self-repair mechanisms of tumor cells post-treatment. Simultaneously, CPC enhances the ionization energy deposition effect on tumor cells. Results: The results demonstrate an increased level of ROS and an elevation in oxygen content at the tumor site. Importantly, tumor growth was restrained without apparent systemic toxicity during the combined treatment. Conclusion: In summary, this study highlights the potential of CPC nanozyme-mediated radiotherapy as a promising avenue for the effective treatment of bladder cancer and demonstrates its potential for future clinical applications in the synergistic therapy of bladder cancer.

Developing a Palladium(II) Agent to Overcome Multidrug Resistance and Metastasis of Liver Tumor by Targeted Multiacting on Tumor Cell, Inactivating Cancer-Associated Fibroblast and Activating Immune Response.

To targeted overcome the multidrug resistance (MDR) and metastasis of liver tumors, we proposed to develop a palladium (Pd) agent based on a specific residue of human serum albumin (HSA) for multiacting on tumor cell and other components in the tumor microenvironment. To this end, a series of Pd(II) 2-acetylpyridine thiosemicarbazone compounds were optimized to obtain a Pd(II) compound (5b) with significant cytotoxicity against HepG2/ADM cells. Subsequently, we constructed a HSA-5b complex delivery system and revealed the structural mechanism of HSA delivering 5b. Importantly, 5b/HSA-5b effectively inhibited the growth and metastasis of multidrug resistant liver tumors, and HSA enhanced the targeting ability of 5b and reduced its side effects in vivo. Furthermore, we confirmed the mechanisms of 5b/HSA-5b integrating to overcome MDR and metastasis of liver tumors: multiacting on cancer cell, activating immune response, and inactivating cancer-associated fibroblasts.

Au@Pd nanozyme-mediated catalytic therapy: a novel strategy for targeting tumor microenvironment in cancer treatment.

BACKGROUND: Breast cancer, with its high morbidity and mortality rates, is a significant global health burden. Traditional treatments-surgery, chemotherapy, and radiotherapy-are widely used but come with drawbacks such as recurrence, metastasis, and significant side effects, including damage to healthy tissues. To address these limitations, new therapeutic strategies are being developed. Peroxidases (POD) can catalyze excess H2O2 in the tumor microenvironment to generate reactive oxygen species (ROS), which induce cancer cell apoptosis by disrupting redox homeostasis and modulating apoptosis-related proteins. However, natural enzymes face challenges like poor stability, high cost, and sensitivity to environmental conditions, limiting their application in breast cancer treatment. Nanozymes, nanomaterials with enzyme-like activity, offer a promising alternative by overcoming these limitations. METHODS: In this study, we successfully prepared Au@Pd nanozymes with peroxidase activity by depositing metallic Pd on Au nanoparticles (Au NPs) synthesized using a trisodium citrate reduction method and ascorbic acid reduction. The in vitro validation was conducted through a series of experiments, including ROS detection, flow cytometry, CCK-8 assay, DNA damage assessment, live/dead cell staining, Western blot (WB), and qPCR. Tumor treatment was performed via tail vein injection of the drug, followed by HE staining of the treated tissues and biochemical analysis of the blood. RESULTS: Au@Pd nanozymes can effectively accumulate at the tumor site through the EPR effect and exert peroxidase-like activity, catalyzing the excess H2O2 in the tumor microenvironment to produce ROS. This triggers apoptosis pathways and DNA damage, leading to the downregulation of the anti-apoptotic protein Bcl-2, upregulation of the pro-apoptotic protein Bax, and induction of apoptosis-related genes, demonstrating strong anti-tumor effects. CONCLUSIONS: This study developed an efficient nanozyme-mediated catalytic therapy strategy targeting the tumor microenvironment for the treatment of breast cancer cells.

Atomic-scale strain engineering of atomically resolved Pt clusters transcending natural enzymes.

Strain engineering plays an important role in tuning electronic structure and improving catalytic capability of biocatalyst, but it is still challenging to modify the atomic-scale strain for specific enzyme-like reactions. Here, we systematically design Pt single atom (Pt1), several Pt atoms (Ptn) and atomically-resolved Pt clusters (Ptc) on PdAu biocatalysts to investigate the correlation between atomic strain and enzyme-like catalytic activity by experimental technology and in-depth Density Functional Theory calculations. It is found that Ptc on PdAu (Ptc-PA) with reasonable atomic strain upshifts the d-band center and exposes high potential surface, indicating the sufficient active sites to achieve superior biocatalytic performances. Besides, the Pd shell and Au core serve as storage layers providing abundant energetic charge carriers. The Ptc-PA exhibits a prominent peroxidase (POD)-like activity with the catalytic efficiency (Kcat/Km) of 1.50 × 109 mM-1 min-1, about four orders of magnitude higher than natural horseradish peroxidase (HRP), while catalase (CAT)-like and superoxide dismutase (SOD)-like activities of Ptc-PA are also comparable to those of natural enzymes. Biological experiments demonstrate that the detection limit of the Ptc-PA-based catalytic detection system exceeds that of visual inspection by 132-fold in clinical cancer diagnosis. Besides, Ptc-PA can reduce multi-organ acute inflammatory damage and mitigate oxidative stress disorder.

A Smartphone-Mediated "All-In-One" Biosensing Chip for Visual and Value-Assisted Detection.

A smartphone-mediated self-powered biosensor is fabricated for miRNA-141 detection based on the CRISPR/Cas12a cross-cutting technique and a highly efficient nanozyme. As a novel nanozyme and a signal-amplified coreaction accelerator, the AuPtPd@GDY nanozyme exhibits an excellent ability to catalyze cascade color reactions and high conductivity to enhance the electrochemical signal for miRNA-141 assays. After CRISPR/Cas12a cross-cutting of S2-glucose oxidase (S2-GOD), the electrochemical signal is weakened, and miRNA-141 is detected by monitoring the decrease in the signal. On the other hand, a cascade reaction among glucose, H2O2, and TMB is catalyzed by GOD and AuPtPd@GDY, respectively, resulting in a color change of the solution, which senses miRNA-141. The self-powered biosensor enables value-assisted and visual detection of miRNA-141 with limits of detection of 3.1 and 15 aM, respectively. Based on the dual-modal self-powered sensing system, a smartphone-mediated "all-in-one" biosensing chip is designed to achieve the real-time and intelligent monitoring of miRNA-141. This work provides a new approach to design multifunctional biosensors to realize the visualization and portable detection of tumor biomarkers.

Non-Medical Applications of Inorganic Medicines. A Switch Based on Mechanistic Knowledge.

Metals have been used in medicine for centuries. However, it was not until much later that the effects of inorganic drugs could be rationalized from a mechanistic point of view. Today, thanks to the technologies available, this approach has been functionally developed and implemented. It has been found that there is probably no single biological target for the pharmacological effects of most inorganic drugs. Herein, we present an overview of some integrated and multi-technique approaches to elucidate the molecular interactions underlying the biological effects of metallodrugs. On this premise, selected examples are used to illustrate how the information obtained on metal-based drugs and their respective mechanisms can become relevant for applications in fields other than medicine. For example, some well-known metallodrugs, which have been shown to bind specific amino acid residues of proteins, can be used to solve problems related to protein structure elucidation in crystallographic studies. Diruthenium tetraacetate can be used to catalyze the conversion of hydroxylamines to nitrones with a high selectivity when bound to lysozyme. Finally, a case study is presented in which an unprecedented palladium/arsenic-mediated catalytic cycle for nitrile hydration was discovered thanks to previous studies on the solution chemistry of the anticancer compound arsenoplatin-1 (AP-1).

Palladium-103 (103Pd/103mRh), a promising Auger-electron emitter for targeted radionuclide therapy of disseminated tumor cells - absorbed doses in single cells and clusters, with comparison to 177Lu and 161Tb.

Early use of targeted radionuclide therapy (TRT) to eradicate disseminated tumor cells (DTCs) might offer cure. Selection of appropriate radionuclides is required. This work highlights the potential of 103Pd (T1/2 = 16.991 d) which decays to 103mRh (T1/2 = 56.12 min) then to stable 103Rh with emission of Auger and conversion electrons. Methods: The Monte Carlo track structure code CELLDOSE was used to assess absorbed doses in single cells (14-µm diameter; 10-µm nucleus) and clusters of 19 cells. The radionuclide was distributed on the cell surface, within the cytoplasm, or in the nucleus. Absorbed doses from 103Pd, 177Lu and 161Tb were compared after energy normalization. The impact of non-uniform cell targeting, and the potential benefit from dual-targeting was investigated. Additional results related to 103mRh, if used directly, are provided. Results: In the single cell, and depending on radionuclide distribution, 103Pd delivered 7- to 10-fold higher nuclear absorbed dose and 9- to 25-fold higher membrane dose than 177Lu. In the 19-cell clusters, 103Pd absorbed doses also largely exceeded 177Lu. In both situations, 161Tb stood in-between 103Pd and 177Lu. Non-uniform targeting, considering four unlabeled cells within the cluster, resulted in moderate-to-severe dose heterogeneity. For example, with intranuclear 103Pd, unlabeled cells received only 14% of the expected nuclear dose. Targeting with two 103Pd-labeled radiopharmaceuticals minimized dose heterogeneity. Conclusion: 103Pd, a next-generation Auger emitter, can deliver substantially higher absorbed doses than 177Lu to single tumor cells and cell clusters. This may open new horizons for the use of TRT in adjuvant or neoadjuvant settings, or for targeting minimal residual disease.

Palladium(II)-Indenyl Complexes Bearing N-Heterocyclic Carbene (NHC) Ligands as Potent and Selective Metallodrugs toward High-Grade Serous Ovarian Cancer Models.

In this study, we synthesized novel Pd(II)-indenyl complexes using various N-heterocyclic carbene (NHC) ligands, including chelating NHC-picolyl, NHC-thioether, and diNHC ligands, and two monodentate NHCs. Transmetalation reactions between a Pd(II)-indenyl precursor and silver-NHC complexes were generally employed, except for chelating diNHC derivatives, which required direct reaction with bisimidazolium salts and potassium carbonate. Characterization included NMR, HRMS analysis, and single-crystal X-ray diffraction. In vitro on five ovarian cancer cell lines showed notable cytotoxicity, with IC50 values in the micro- and submicromolar range. Some compounds exhibited intriguing selectivity for cancer cells due to higher tumor cell uptake. Mechanistic studies revealed that monodentate NHCs induced mitochondrial damage while chelating ligands caused DNA damage. One chelating NHC-picolyl ligand showed promising cytotoxicity and selectivity in high-grade serous ovarian cancer models, supporting its consideration for preclinical study.

Late-Stage Glycosylation of Peptides by Methionine-Directed ß-C(sp3)-H Functionalization with 1-Iodoglycals.

Using l-methionine (Met) as the endogenous directing group, we developed Pd-catalyzed ß-C(sp3)-H glycosylation of peptides with 1-iodoglycals. A wide range of tri- to hexapeptides containing the Ala-Met motifs underwent Ala C-H glycosylation under the standard conditions to give the glycopeptides smoothly. 15 proteinogenic amino acids (with easily removable protecting groups) were well tolerated. Control experiments indicated that Met acted as a N,S-bidentate directing group and exhibited an effect superior to other amino acid residues such as l-aspartic acid (Asp), l-asparagine (Asn), and S-protected l-cysteine (Cys). In addition, further transformation by HFIP-promoted 1,4-elimination furnished another type of glycopeptide with the 1,3-diene motif, which provides a handle for further derivatization.

Non-benzenoid N-aryl oxalamide: synthesis of troponyl-oxalamide peptides by Pd(II)-catalyzed C(sp3)-H functionalization of glycinamides.

Aryl oxalamides are constituents of various promising drug-like molecules. Their aryl groups are derived from the benzenoid aromatic moiety. However, non-benzenoid aromatic molecules, troponoids, are found in various bioactive natural products. It would be thought-provoking to explore non-benzenoid aryl oxalamide derivatives. This report describes the synthesis of N-troponyl-oxalamide peptides by Pd(II)-catalyzed C(sp3)-H functionalization of N-troponyl glycinate peptides. This is the first instance of ß-hydride elimination at the palladium complex of N-troponyl glycinates that generates imine in situ, rendering the synthesis of oxalamides. Importantly, the crystal structures of representative oxalamide derivatives form distinctive foldameric structures, such as ß-sheet type structures, owing to the presence of additional troponyl carbonyl groups. Hence, these non-benzenoid oxalamides are potential scaffolds for tuning the structure and function of N-troponyl peptides, which could provide innovative avenues of research in the development of emerging structural and functional peptides.

Controlled Reversible N-Terminal Modification of Peptides and Proteins.

A reversible modification strategy enables a switchable cage/decage process of proteins with an array of applications for protein function research. However, general N-terminal selective reversible modification strategies which present site selectivity are specifically limited. Herein, we report a general reversible modification strategy compatible with 20 canonical amino acids at the N-terminal site by the palladium-catalyzed cinnamylation of native peptides and proteins under biologically relevant conditions. This approach broadens the substrate adaptability of N-terminal modification of proteins and shows a potential impact on the more challenging protein substrates such as antibodies. In the presence of 1,3-dimethylbarbituric acid, palladium-catalyzed deconjugation released native peptides and proteins efficiently. Harnessing the reversible nature of this protocol, practical applications were demonstrated by precise function modulation of antibodies and traceless enrichment of the protein-of-interest for proteomics analysis. This novel on/off strategy working on the N-terminus will provide new opportunities in chemical biology and medicinal research.

Hypoxia Reversion and STING Pathway Activation through Large Mesoporous Nanozyme for Near-Infrared-II Light Amplified Tumor Polymetallic-Immunotherapy.

cGAS/STING pathway, which is highly related to tumor hypoxia, is considered as a potential target for remodeling the immunosuppressive microenvironment of solid tumors. Metal ions, such as Mn2+, activate the cGAS/STING pathway, but their efficacy in cancer therapy is limited by insufficient effect on immunogenic tumor cell death of a single ion. Here, we evaluate the association between tumor hypoxia and cGAS/STING inhibition and report a polymetallic-immunotherapy strategy based on large mesoporous trimetal-based nanozyme (AuPdRh) coordinated with Mn2+ (Mn2+@AuPdRh) to activate cGAS/STING signaling for robust adaptive antitumor immunity. Specifically, the inherent CAT-like activity of this polymetallic Mn2+@AuPdRh nanozyme decomposes the endogenous H2O2 into O2 to relieve tumor hypoxia induced suppression of cGAS/STING signaling. Moreover, the Mn2+@AuPdRh nanozyme displays a potent near-infrared-II photothermal effect and strong POD-mimic activity; and the generated hyperthermia and •OH radicals synergistically trigger immunogenic cell death in tumors, releasing abundant dsDNA, while the delivered Mn2+ augments the sensitivity of cGAS to dsDNA and activates the cGAS-STING pathway, thereby triggering downstream immunostimulatory signals to kill primary and distant metastatic tumors. Our study demonstrates the potential of metal-based nanozyme for STING-mediated tumor polymetallic-immunotherapy and may inspire the development of more effective strategies for cancer immunotherapy.

Controlled bioorthogonal activation of Bromodomain-containing protein 4 degrader by co-delivery of PROTAC and Pd-catalyst for tumor-specific therapy.

The precise and safe treatment of bioorthogonal prodrug system is hindered by separate administration of prodrug and its activator, which often results in poor therapeutic effects and severe side effects. To address above issues, we herein construct a single bioorthogonal-activated co-delivery system for simultaneous PROTAC prodrug (proPROTAC) delivery and controlled, site-specific activation for tumor-specific treatment. In this co-delivery system (termed AuPLs), prodrug (proPROTAC) and water-soluble Pd-catalyst are first encapsulated by gold nanocubes (AuNCs), which are further coated with a layer of phase-change material (lauric acid/stearic acid, LA/SA). Below 39 °C, the solid state of LA/SA prevents the activation of Pd-mediated bioorthogonal reaction due to the solidification of Pd-catalyst and proPROTAC. Nevertheless, once over 42 °C, the phase change of LA/SA into liquid state, enabled by the photothermal effect of AuNCs, triggers the simultaneous release of proPROTAC and Pd-catalyst and initiates the in situ bioorthogonal reaction for proPROTAC activation. In the tumor-bearing mouse models, the systemic administration of AuPLs results in the accumulation in tumor region, where the photothermal effect activates and controls the tumor-specific bioorthogonal reaction to degrade BRD4 protein, leading to anti-tumor effects with minimized side effects. Overall, the co-delivery proPROTAC and Pd-catalyst and controlled activation by photothermal effects provide a precise way for biorthogonal-based anticancer prodrugs.

Point-of-care testing of Pseudomonas aeruginosa using PCN-222(Pt) prepared by nanoconfinement-guided protocol to catalyze gas generation reaction.

BACKGROUND: Pathogenic bacteria are keeping threatening global public health since they can cause many infectious diseases. The traditional microorganism identification and molecular diagnostic techniques are insufficiently sensitive, time-consuming, or expensive. Thus it is of great interest to establish pressure signal-based sensing platforms for point-of-care testing of pathogenic bacteria to achieve timely diagnosis of infectious diseases. Rational design and synthesis of nano-sized probes with high peroxidase-mimicking activity have been a long-term cherished goal for improving the sensitivity of pressure signal-based sensing methods. RESULTS: Guided by nanoconfinement effect, PCN-222(Pt) was prepared by confining Pt clusters within the channels of a zirconium porphyrin MOFs material termed as PCN-222. In comparison to regular platinum nanoparticles, palladium@platinum core-shell nanodendrites, and platinum-coated gold nanoparticles, the prepared PCN-222(Pt) displayed superior peroxidase-mimicking activity with outstanding efficiency for catalyzing the decay of H2O2 to produce O2. Thus it was used as a pressure signal probe to establish a sensitive method on a hydrogel pellets platform for analyzing Pseudomonas aeruginosa (P. aeruginosa), for which polymyxin B and a phage termed as JZ1 were used as recognition agents for the target pathogen. P. aeruginosa was quantified with a handheld pressure meter within a broad range of 2.2 × 102-2.2 × 107 cfu mL-1. This method was used to quantify P. aeruginosa in various biological and food samples with acceptable accuracy and reliability. SIGNIFICANCE: The proposed nanoconfinement-guided protocol provides a novel approach for rational design and preparation of nano-sized probes with high peroxidase-mimicking activity for catalyzing gas-generation reaction. Thus this study opens an avenue for establishment of sensitive pressure signal-based sensing methods for pathogenic bacteria, which shows broad application prospects in medical diagnosis of infectious diseases.

Fabrication of thiosemicarbazone-based Pd(II) complexes: structural elucidations, catalytic activity towards Suzuki-Miyaura coupling reaction and antitumor activity against TNBC cells.

Currently, there are many uses of metal complexes, especially in the fields of medicinal chemistry and catalysis. Thus, fabrication of new complexes which perform as a catalyst and chemotherapeutic drug is always a beneficial addition to the literature. Herein, we report three heterocyclic thiosemicarbazone-based Pd(II) complexes [Pd(HL1)Cl] (C1), [Pd(L2)(PPh3)] (C2) and [Pd(L3)(PPh3)]Cl (C3) having coligands Cl and PPh3. Thiosemicarbazone ligands (H2L1, H2L2 and HL3) and the complexes (C1-C3) were characterized methodically using several spectroscopic techniques. Single-crystal X-ray diffraction methods reveal that the structural environment around the metal center of C2 is square planar, while for C1 and C3 it is a slighty distorted square plane. The supramolecular network of compounds was built via hydrogen bonds, C-H⋯π and π⋯π interactions. Density functional theory (DFT) study of the structure of the complexes supports experimental findings. The application of these complexes as catalysts toward Suzuki-Miyaura coupling reactions has been examined with various aryl halides and phenyl boronic acid in PEG 400 solvent. The complexes displayed good biomolecular interactions with DNA/protein, with a binding constant value of the order of 105 M-1. C3 showed greater binding efficacy toward these biomolecules than the other complexes, which might be due to the cationic nature of C3. Furthermore, antitumor activity of the complexes was studied against the human triple-negative breast cancer (TNBC) cell line MDA-MB-231. It was found that C3 was more toxic (IC50 = 10 ± 2.90 µM) toward MDA-MB-231 cells than the other complexes. A known chemotherapeutic drug, 5-fluorouracil, was included as positive control. The programmed cell death mechanism of C3 was confirmed. Additionally, complex-induced apoptosis was confirmed and occurred via a mitochondria-dependent (intrinsic) pathway.

Site-Specific Antibody Prodrugs via S-Arylation: a Bioconjugation Approach Toward Masked Tyrosine Analogues.

The utility of antibody therapeutics is hampered by potential cross-reactivity with healthy tissue. Over the past decade, significant advances have been made in the design of activatable antibodies, which increase, or create altogether, the therapeutic window of a parent antibody. Of these, antibody prodrugs (pro-antibodies) are masked antibodies that have advanced the most for therapeutic use. They are designed to reveal the active, parent antibody only when encountering proteases upregulated in the microenvironment of the targeted disease tissue, thereby minimizing off-target activity. However, current pro-antibody designs are relegated to fusion proteins that append masking groups restricted to the use of only canonical amino acids, offering excellent control of the site of introduction, but with no authority over where the masking group is installed other than the N-terminus of the antibody. Here, we present a palladium-based bioconjugation approach for the site-specific introduction of a masked tyrosine mimic in the complementary determining region of the FDA approved antibody therapeutic ipilimumab used as a model system. The approach enables the introduction of a protease cleavable group tethered to noncanonical polymers (polyethylene glycol (PEG)) resulting in 47-fold weaker binding to cells expressing CTLA-4, the target antigen of ipilimumab. Upon exposure to tumor-associated proteases, the masking group is cleaved, unveiling a tyrosine-mimic (dubbed hydroxyphenyl cysteine (HPC)) that restores (>90% restoration) binding affinity to its target antigen.