Near-Infrared-Activatable PROTAC Nanocages for Controllable Target Protein Degradation and On-Demand Antitumor Therapy

Nano-PROTACs: state of the art and perspectives

PROteolysis TArgeting Chimeras (PROTACs), as a recently identified technique in the field of new drug development, provide new concepts for disease treatment and are expected to revolutionize drug discovery. With high specificity and flexibility, PROTACs serve as an innovative research tool to target and degrade disease-relevant proteins that are not currently pharmaceutically vulnerable to eliminating their functions by hijacking the ubiquitin-proteasome system. To date, PROTACs still face the challenges of low solubility, poor permeability, off-target effects, and metabolic instability. The combination of nanotechnology and PROTACs has been explored to enhance the in vivo performance of PROTACs regarding overcoming these challenging hurdles. In this review, we summarize the latest advancements in the building-block design of PROTAC prodrug nanoparticles and provide an overview of existing/potential delivery systems and loading approaches for PROTAC drugs. Furthermore, we discuss the current status and prospects of the split-and-mix approach for PROTAC drug optimization. Additionally, the advantages and translational potentials of carrier-free nano-PROTACs and their combinational therapeutic effects are highlighted. This review aims to foster a deeper understanding of this rapidly evolving field and facilitate the progress of nano-PROTACs that will continue to push the boundaries of achieving selectivity and controlled release of PROTAC drugs.

A PROTAC Augmenter for Photo-Driven Pyroptosis in Breast Cancer

Proteolysis targeting chimera (PROTAC) has recently emerged as a promising strategy for inducing post-translational knockdown of target proteins in disease treatment. The degradation of bromodomain-containing protein 4 (BRD4), an essential nuclear protein for gene transcription, induced by PROTAC is proposed as an epigenetic approach to treat breast cancer. However, the poor membrane permeability and indiscriminate distribution of PROTAC in vivo results in low bioavailability, limiting its development and application. Herein, a nano "targeting chimera" (abbreviated as L@NBMZ) consisting of BRD4-PROTAC combined with a photosensitizer, to serve as the first augmenter for photo-driven pyroptosis in breast cancer, is developed. With excellent BRD4 degradation ability, high biosafety, and biocompatibility, L@NBMZ blocks gene transcription by degrading BRD4 through proteasomes in vivo, and surprisingly, induces the cleavage of caspase-3. This type of caspase-3 cleavage is synergistically amplified by light irradiation in the presence of photosensitizers, leading to efficient photo-driven pyroptosis. Both in vitro and in vivo outcomes demonstrate the remarkable anti-cancer efficacy of this augmenter, which significantly inhibits the lung metastasis of breast cancer in vivo. Thus, the photo-PROTAC "targeting chimera" augmenter construction strategy may pave a new way for expanding PROTAC applications within anti-cancer paradigms.

Designer Nanoreactors for Bioorthogonal Catalysis

ConspectusThe evolutionary complexity of compartmentalized biostructures (such as cells and organelles) endows life-sustaining multistep chemical cascades and intricate living functionalities. Relatively, within a very short time span, a synthetic paradigm has resulted in tremendous growth in controlling the materials at different length scales (molecular, nano, micro, and macro), improving mechanistic understanding and setting the design principals toward different compositions, configurations, and structures, and in turn fine-tuning their optoelectronic and catalytic properties for targeted applications. Bioorthogonal catalysis offers a highly versatile toolkit for biochemical modulation and the capability to perform new-to-nature reactions inside living systems, endowing augmented functions. However, conventional catalysts have limitations to control the reactions under physiological conditions due to the hostile bioenvironment. The present account details the development of bioapplicable multicomponent designer nanoreactors (NRs), where the compositions, morphologies, interfacial active sites, and microenvironments around different metal nanocatalysts can be precisely controlled by novel nanospace-confined chemistries. Different architectures of porous, hollow, and open-mouth silica-based nano-housings facilitate the accommodation, protection, and selective access of different nanoscale metal-based catalytic sites. The modular porosity/composition, optical transparency, thermal insulation, and nontoxicity of silica are highly useful. Moreover, large macropores or cavities can also be occupied by enzymes (for chemoenzymatic cascades) and selectivity enhancers (for stimuli-responsive gating) along with the metal nanocatalysts. Further, it is crucial to selectively activate and control catalytic reactions by a remotely operable biocompatible energy source. Integration of highly coupled plasmonic (Au) components having few-nanometer structural features (gaps, cavities, and junctions as electromagnetic hot-spots) endows an opportunity to efficiently harness low-power NIR light and selectively supply energy to the interfacial catalytic sites through localized photothermal and electronic effects. Different plasmonically integrated NRs with customizable plasmonic-catalytic components, cavities inside bilayer nanospaces, and metal-laminated nanocrystals inside hollow silica can perform NIR-/light-induced catalytic reactions in complex media including living cells. In addition, magnetothermia-induced NRs by selective growth of catalytic metals on a pre-installed superparamagnetic iron-oxide core inside a hollow-porous silica shell endowed the opportunity to apply AMF as a bioorthogonal stimulus to promote catalytic reactions. By combining "plasmonic-catalytic" and "magnetic-catalytic" components within a single NR, two distinct reaction steps can be desirably controlled by two energy sources (NIR light and AMF) of distinct energy regimes. The capability to perform multistep organic molecular transformations in harmony with the natural living system will reveal novel reaction schemes for in cellulo synthesis of active drug and bioimaging probes. Well-designed nanoscale discrete architectures of NRs can facilitate spatiotemporal control over abiotic chemical synthesis without adversely affecting the cell viability. However, in-depth understanding of heterogeneous surface catalytic reactions, rate induction mechanisms, selectivity control pathways, and targeted nanobio interactions is necessary. The broad field of biomedical engineering can hugely benefit from the aid of novel nanomaterials with chemistry-based designs and the synthesis of engineered NRs performing unique bioorthogonal chemistry functions.

Small molecules targeting selected histone methyltransferases (HMTs) for cancer treatment: Current progress and novel strategies

Histone methyltransferases (HMTs) play a critical role in gene post-translational regulation and diverse physiological processes, and are implicated in a plethora of human diseases, especially cancer. Increasing evidences demonstrate that HMTs may serve as a potential therapeutic target for cancer treatment. Thus, the development of HMTs inhibitor have been pursued with steadily increasing interest over the past decade. However, the disadvantages such as insufficient clinical efficacy, moderate selectivity, and propensity for acquired resistance have hindered the development of conventional HMT inhibitors. New technologies and methods are imperative to enhance the anticancer activity of HMT inhibitors. In this review, we first review the structure and biological functions of the several essential HMTs, such as EZH2, G9a, PRMT5, and DOT1L. The internal relationship between these HMTs and cancer is also expounded. Next, we mainly focus on the latest progress in the development of HMT modulators encompassing dual-target inhibitors, targeted protein degraders and covalent inhibitors from perspectives such as rational design, pharmacodynamics, pharmacokinetics, and clinical status. Lastly, we also discuss the challenges and future directions for HMT-based drug discovery for cancer therapy.

Current advances and development strategies of orally bioavailable PROTACs

Proteolysis-targeting chimeras (PROTACs) have been an area of intensive research with the potential to extend drug space not target to traditional molecules. In the last half decade, we have witnessed several PROTACs initiated phase I/II/III clinical trials, which inspired us a lot. However, the structure of PROTACs beyond "rule of 5" resulted in developing PROTACs with acceptable oral pharmacokinetic (PK) properties remain one of the biggest bottleneck tasks. Many reports have demonstrated that it is possible to access orally bioavailable PROTACs through rational ligand and linker modifications. In this review, we systematically reviewed and highlighted the most recent advances in orally bioavailable PROTACs development, especially focused on the medicinal chemistry campaign of discovery process and in vivo oral PK properties. Moreover, the constructive strategies for developing oral PROTACs were proposed comprehensively. Collectively, we believe that the strategies summarized here may provide references for further development of oral PROTACs.

Recent Advances in Optically Controlled PROTAC

Proteolysis-targeting chimera (PROTAC) technology is a groundbreaking therapeutic approach with significant clinical potential for degrading disease-inducing proteins within targeted cells. However, challenges related to insufficient target selectivity raise concerns about PROTAC toxicity toward normal cells. To address this issue, researchers are modifying PROTACs using various approaches to enhance their target specificity. This review highlights innovative optically controlled PROTACs as anti-cancer therapies currently used in clinical practice and explores the challenges associated with their efficacy and safety. The development of optically controlled PROTACs holds the potential to significantly expand the clinical applicability of PROTAC-based technology within the realm of drug discovery.

Targeted Strategies for Degradation of Key Transmembrane Proteins in Cancer

Targeted protein degradation is an attractive technology for cancer treatment due to its ability to overcome the unpredictability of the small molecule inhibitors that cause resistance mutations. In recent years, various targeted protein degradation strategies have been developed based on the ubiquitin-proteasome system in the cytoplasm or the autophagy-lysosomal system during endocytosis. In this review, we describe and compare technologies for the targeted inhibition and targeted degradation of the epidermal growth factor receptor (EGFR), one of the major proteins responsible for the onset and progression of many types of cancer. In addition, we develop an alternative strategy, called alloAUTO, based on the binding of new heterocyclic compounds to an allosteric site located in close proximity to the EGFR catalytic site. These compounds cause the targeted degradation of the transmembrane receptor, simultaneously activating both systems of protein degradation in cells. Damage to the EGFR signaling pathways promotes the inactivation of Bim sensor protein phosphorylation, which leads to the disintegration of the cytoskeleton, followed by the detachment of cancer cells from the extracellular matrix, and, ultimately, to cancer cell death. This hallmark of targeted cancer cell death suggests an advantage over other targeted protein degradation strategies, namely, the fewer cancer cells that survive mean fewer chemotherapy-resistant mutants appear.

Recent Studies and Progress in the Intratumoral Administration of Nano-Sized Drug Delivery Systems

Over the last 30 years, diverse types of nano-sized drug delivery systems (nanoDDSs) have been intensively explored for cancer therapy, exploiting their passive tumor targetability with an enhanced permeability and retention effect. However, their systemic administration has aroused some unavoidable complications, including insufficient tumor-targeting efficiency, side effects due to their undesirable biodistribution, and carrier-associated toxicity. In this review, the recent studies and advancements in intratumoral nanoDDS administration are generally summarized. After identifying the factors to be considered to enhance the therapeutic efficacy of intratumoral nanoDDS administration, the experimental results on the application of intratumoral nanoDDS administration to various types of cancer therapies are discussed. Subsequently, the reports on clinical studies of intratumoral nanoDDS administration are addressed in short. Intratumoral nanoDDS administration is proven with its versatility to enhance the tumor-specific accumulation and retention of therapeutic agents for various therapeutic modalities. Specifically, it can improve the efficacy of therapeutic agents with poor bioavailability by increasing their intratumoral concentration, while minimizing the side effect of highly toxic agents by restricting their delivery to normal tissues. Intratumoral administration of nanoDDS is considered to expand its application area due to its potent ability to improve therapeutic effects and relieve the systemic toxicities of nanoDDSs.