Prodrugs: design and clinical applications. Nat Rev Drug Discov. 2008;7:255-270. [PMID: 18219308 DOI: 10.1038/nrd2468]

Prediction of Aggregation of Biologically-Active Peptides with the UNRES Coarse-Grained Model

The UNited RESidue (UNRES) model of polypeptide chains was applied to study the association of 20 peptides with sizes ranging from 6 to 32 amino-acid residues. Twelve of those were potentially aggregating hexa- or heptapeptides excised from larger proteins, while the remaining eight contained potentially aggregating sequences, functionalized by attaching larger ends rich in charged residues. For 13 peptides, the experimental data of aggregation were used. The remaining seven were synthesized, and their properties were measured in this work. Multiplexed replica-exchange simulations of eight-chain systems were conducted at 12 temperatures from 260 to 370 K at concentrations from 0.421 to 5.78 mM, corresponding to the experimental conditions. The temperature profiles of the fractions of monomers and octamers showed a clear transition corresponding to aggregate dissociation. Low simulated transition temperatures were obtained for the peptides, which did not precipitate after incubation, as well as for the H-GNNQQNY-NH2 prion–protein fragment, which forms small fibrils. A substantial amount of inter-strand β-sheets was found in most of the systems. The results suggest that UNRES simulations can be used to assess peptide aggregation except for glutamine- and asparagine-rich peptides, for which a revision of the UNRES sidechain–sidechain interaction potentials appears necessary.

Glutathione-Mediated Conjugation of Anticancer Drugs: An Overview of Reaction Mechanisms and Biological Significance for Drug Detoxification and Bioactivation

The effectiveness of many anticancer drugs depends on the creation of specific metabolites that may alter their therapeutic or toxic properties. One significant route of biotransformation is a conjugation of electrophilic compounds with reduced glutathione, which can be non-enzymatic and/or catalyzed by glutathione-dependent enzymes. Glutathione usually combines with anticancer drugs and/or their metabolites to form more polar and water-soluble glutathione S-conjugates, readily excreted outside the body. In this regard, glutathione plays a role in detoxification, decreasing the likelihood that a xenobiotic will react with cellular targets. However, some drugs once transformed into thioethers are more active or toxic than the parent compound. Thus, glutathione conjugation may also lead to pharmacological or toxicological effects through bioactivation reactions. My purpose here is to provide a broad overview of the mechanisms of glutathione-mediated conjugation of anticancer drugs. Additionally, I discuss the biological importance of glutathione conjugation to anticancer drug detoxification and bioactivation pathways. I also consider the potential role of glutathione in the metabolism of unsymmetrical bisacridines, a novel prosperous class of anticancer compounds developed in our laboratory. The knowledge on glutathione-mediated conjugation of anticancer drugs presented in this review may be noteworthy for improving cancer therapy and preventing drug resistance in cancers.

Ligand release from silicon phthalocyanine dyes triggered by X-ray irradiation

Ligand release from silicon phthalocyanine (SiPc) dyes triggered by near-infrared (NIR) light is a key photochemical reaction involving caged compounds based on SiPc. Although NIR light is relatively permeable compared with visible light, this light can be attenuated by tissue absorption and scattering; therefore, using light to induce photochemical reactions deep inside the body is difficult. Herein, because X-rays are highly permeable and can produce radicals through the radiolysis of water, we investigated whether the axial ligands of SiPcs can be cleaved using X-ray irradiation. SiPcs with different axial ligands (alkoxy, siloxy, oxycarbonyl, and phenoxy groups) were irradiated with X-rays under hypoxic conditions. We found that the axial ligands were cleaved via reactions with hydrated electrons (e^-_aq), not OH radicals, generated from water in response to X-ray irradiation, and SiPc with alkoxy groups exhibited the highest cleavage efficiency. A quantitative investigation revealed that X-ray-induced axial ligand cleavage proceeds via a radical chain reaction. The reaction is expected to be applicable to the molecular design of X-ray-activatable functional molecules in the future.

Adenosine triphosphate-activated prodrug system for on-demand bacterial inactivation and wound disinfection

The prodrug approach has emerged as a promising solution to combat bacterial resistance and enhance treatment efficacy against bacterial infections. Here, we report an adenosine triphosphate (ATP)-activated prodrug system for on-demand treatment of bacterial infection. The prodrug system benefits from the synergistic action of zeolitic imidazolate framework-8 and polyacrylamide hydrogel microsphere, which simultaneously transports indole-3-acetic acid and horseradish peroxidase in a single carrier while preventing the premature activation of indole-3-acetic acid. The ATP-responsive characteristic of zeolitic imidazolate framework-8 allows the prodrug system to be activated by the ATP secreted by bacteria to generate reactive oxygen species (ROS), displaying exceptional broad-spectrum antimicrobial ability. Upon disruption of the bacterial membrane by ROS, the leaked intracellular ATP from dead bacteria can accelerate the activation of the prodrug system to further enhance antibacterial efficiency. In vivo experiments in a mouse model demonstrates the applicability of the prodrug system for wound disinfection with minimal side effects.

Prodrugs are increasingly promising in tackling bacterial resistance and efficacy of treatment. Here, the authors encapsulated horseradish peroxidase and zeolitic imidazolate framework-8 loaded with indole-3-acetic acid in polyacrylamide hydrogel microspheres for ATP-activated wound disinfection.

Nanozyme-Based Artificial Organelles: An Emerging Direction for Artificial Organelles

Artificial organelles are compartmentalized nanoreactors, in which enzymes or enzyme-mimic catalysts exhibit cascade catalytic activities to mimic the functions of natural organelles. Importantly, research on artificial organelles paves the way for the bottom-up design of synthetic cells. Due to the separation effect of microcompartments, the catalytic reactions of enzymes are performed without the influence of the surrounding medium. The current techniques for synthesizing artificial organelles rely on the strategies of encapsulating enzymes into vesicle-structured materials or reconstituting enzymes onto the microcompartment materials. However, there are still some problems including limited functions, unregulated activities, and difficulty in targeting delivery that hamper the applications of artificial organelles. The emergence of nanozymes (nanomaterials with enzyme-like activities) provides novel ideas for the fabrication of artificial organelles. Compared with natural enzymes, nanozymes are featured with multiple enzymatic activities, higher stability, easier to synthesize, lower cost, and excellent recyclability. Herein, the most recent advances in nanozyme-based artificial organelles are summarized. Moreover, the benefits of compartmental structures for the applications of nanozymes, as well as the functional requirements of microcompartment materials are also introduced. Finally, the potential applications of nanozyme-based artificial organelles in biomedicine and the related challenges are discussed.

Degradable polyprodrugs: design and therapeutic efficiency

Prodrugs are developed to increase the therapeutic properties of drugs and reduce their side effects. Polyprodrugs emerged as highly efficient prodrugs produced by the polymerization of one or several drug monomers. Polyprodrugs can be gradually degraded to release therapeutic agents. The complete degradation of polyprodrugs is an important factor to guarantee the successful disposal of the drug delivery system from the body. The degradation of polyprodrugs and release rate of the drugs can be controlled by the type of covalent bonds linking the monomer drug units in the polymer structure. Therefore, various types of polyprodrugs have been developed based on polyesters, polyanhydrides, polycarbonates, polyurethanes, polyamides, polyketals, polymetallodrugs, polyphosphazenes, and polyimines. Furthermore, the presence of stimuli-responsive groups, such as redox-responsive linkages (disulfide, boronate ester, metal-complex, and oxalate), pH-responsive linkages (ester, imine, hydrazone, acetal, orthoester, P-O and P-N), light-responsive (metal-complex, o-nitrophenyl groups) and enzyme-responsive linkages (ester, peptides) allow for a selective degradation of the polymer backbone in targeted tumors. We envision that new strategies providing a more efficient synergistic therapy will be developed by combining polyprodrugs with gene delivery segments and targeting moieties.

Synthesis and Biological Evaluation of Novel Fusidic Acid Derivatives as Two-in-One Agent with Potent Antibacterial and Anti-Inflammatory Activity

Fusidic acid (FA), a narrow-spectrum antibiotics, is highly sensitive to various Gram-positive cocci associated with skin infections. It has outstanding antibacterial effects against certain Gram-positive bacteria whilst no cross-resistance with other antibiotics. Two series of FA derivatives were synthesized and their antibacterial activities were tested. A new aromatic side-chain analog, FA-15 exhibited good antibacterial activity with MIC values in the range of 0.781–1.563 µM against three strains of Staphylococcus spp. Furthermore, through the assessment by the kinetic assay, similar characteristics of bacteriostasis by FA and its aromatic derivatives were observed. In addition, anti-inflammatory activities of FA and its aromatic derivatives were evaluated by using a 12-O-tetradecanoylphorbol-13-acetate (TPA) induced mouse ear edema model. The results also indicated that FA and its aromatic derivatives effectively reduced TPA-induced ear edema in a dose-dependent manner. Following, multiform computerized simulation, including homology modeling, molecular docking, molecular dynamic simulation and QSAR was conducted to clarify the mechanism and regularity of activities. Overall, the present work gave vital clues about structural modifications and has profound significance in deeply scouting for bioactive potentials of FA and its derivatives.

Selective chlorination of iminosydnones for fast release of amide, sulfonamide and urea-containing drugs

Herein, we describe a methodology for iminosydnone chlorination and we demonstrate the high beneficial effect of this modification on the reactivity of these mesoionic dipoles in strain-promoted cycloaddition reactions. Exploiting their reaction with cyclooctynes, we used these new iminosydnones for bioorthogonal release of amide, urea and sulfonamide containing drugs. Notably, drugs containing a terminal amide function were released for the first time with good kinetic constants.

A Stimuli-Responsive Small-Molecule Metal-Carrying Prochelator: A Novel Prodrug Design Strategy for Metal Complexes

Selective activation of prodrugs is an important approach to reduce the side effects of disease treatment. We report a prodrug design concept for metal complexes, termed "metal-carrying prochelator", which can co-carry a metal ion and chelator within a single small-molecule compound and remain inert until it undergoes a specifically triggered intramolecular chelation to synthesize a bioactive metal complex in situ for targeted therapy. As a proof-of-concept, we designed a H₂ O₂ -responsive small-molecule prochelator, DPBD, based on the strong chelator diethyldithiocarbamate (DTC) and copper. DPBD can carry Cu²⁺ (DPBD-Cu) and respond to elevated H₂ O₂ levels in tumor cells by releasing DTC, which rapidly chelates Cu²⁺ from DPBD-Cu affording a DTC-copper complex with high cytotoxicity, realizing potent antitumor efficacy with low systemic toxicity. Thus, with its unique intramolecularly triggered activation mechanism, this concept based on a small-molecule metal-carrying prochelator can help in the prodrug design of metal complexes.

Structural Modification in Anesthetic Drug Development for Prodrugs and Soft Drugs

Among the advancements in drug structural modifications, the increased focus on drug metabolic and pharmacokinetic properties in the anesthetic drug design process has led to significant developments. Drug metabolism also plays a key role in optimizing the pharmacokinetics, pharmacodynamics, and safety of drug molecules. Thus, in the field of anesthesiology, the applications of pharmacokinetic strategies are discussed in the context of sedatives, analgesics, and muscle relaxants. In this review, we summarize two approaches for structural optimization to develop anesthetic drugs, by designing prodrugs and soft drugs. Drugs that both failed and succeeded during the developmental stage are highlighted to illustrate how drug metabolism and pharmacokinetic optimization strategies may help improve their physical and chemical properties.

Analogues of Pyrimidine Nucleosides as Mycobacteria Growth Inhibitors

Tuberculosis (TB) is the oldest human infection disease. Mortality from TB significantly decreased in the 20th century, because of vaccination and the widespread use of antibiotics. However, about a third of the world’s population is currently infected with Mycobacterium tuberculosis (Mtb) and the death rate from TB is about 1.4–2 million people per year. In the second half of the 20th century, new extensively multidrug-resistant strains of Mtb were identified, which are steadily increasing among TB patients. Therefore, there is an urgent need to develop new anti-TB drugs, which remains one of the priorities of pharmacology and medicinal chemistry. The antimycobacterial activity of nucleoside derivatives and analogues was revealed not so long ago, and a lot of studies on their antibacterial properties have been published. Despite the fact that there are no clinically used drugs based on nucleoside analogues, some progress has been made in this area. This review summarizes current research in the field of the design and study of inhibitors of mycobacteria, primarily Mtb.

Anti-Inflammatory Activity of Oxyresveratrol Tetraacetate, an Ester Prodrug of Oxyresveratrol, on Lipopolysaccharide-Stimulated RAW264.7 Macrophage Cells

Oxyresveratrol (OXY) has been reported for its anti-inflammatory activity; however, the pharmaceutical applications of this compound are limited by its physicochemical properties and poor pharmacokinetic profiles. The use of an ester prodrug is a promising strategy to overcome these obstacles. In previous researches, several carboxylate esters of OXY were synthesized and oxyresveratrol tetraacetate (OXY-TAc) was reported to possess anti-melanogenic and anti-skin-aging properties. In this study, in addition to OXY-TAc, two novel ester prodrugs of OXY, oxyresveratrol tetrapropionate (OXY-TPr), and oxyresveratrol tetrabutyrate (OXY-TBu), were synthesized. Results from the Caco-2-permeation assay suggested that synthesized ester prodrugs can improve the membrane-permeation ability of OXY. The OXY-TAc exhibited the most significant profile, then this prodrug was chosen to observe anti-inflammatory activities with lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Our results showed that OXY-Tac significantly alleviated secretion of several pro-inflammatory mediators (nitric oxide (NO), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α)), mitigated expression of enzyme-regulated inflammation (inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2)), and suppressed the MAPK cascades. Interestingly, the observed anti-inflammatory activities of OXY-TAc were more remarkable than those of its parent compound OXY. Taken together, we demonstrated that OXY-TAc improved physicochemical and pharmacokinetic profiles and enhanced the pharmacological effects of OXY. Hence, the results in the present study would strongly support the clinical utilities of OXY-TAc for the treatment of inflammation-related disorders.

Recent advances in the development of EGFR degraders: PROTACs and LYTACs

Epidermal Growth Factor Receptor (EGFR), a transmembrane tyrosine kinase receptor, belongs to the ErbB receptor family, also known as HER1 or ErbB1. Its abnormal expression and activation contribute to tumor development, especially in non-small cell lung cancer (NCSCL). The first-to fourth-generation inhibitors of EGFR were developed to solve mutations at different sites, but the problem of resistance has not been fundamentally addressed. Targeted protein degradation (TPD) technologies, including PROteolysis Targeting Chimeras (PROTACs) and LYsosome Targeting Chimeras (LYTACs), take advantages of protein destruction mechanism in cells, which make up for shortcomings of traditional small molecular occupancy-driven inhibitors. PROTACs based heterobifunctional EGFR degraders were recently developed by making use of wild-type (WT) and mutated EGFR inhibitors. These degraders compared with EGFR inhibitors showed better efficiency in their cellular potency, inhibition and toxicity profiles. In this review, we first introduce the structural properties of EGFR, the inhibitors that have been developed against WT/mutated EGFR, and then mainly focuses on the recent advances of EGFR-targeting degraders along with its limitations and unlimited prospects.

A ROS-Responsive Simvastatin Nano-Prodrug and its Fibronectin-Targeted Co-Delivery System for Atherosclerosis Treatment

Nanoprodrugs with responsive release properties integrate the advantages of stimuli-responsive prodrugs and nanotechnology. They would provide ultimate opportunity in fighting atherosclerosis. In this study, we synthesized a redox-responsive nanoprodrug of simvastatin (TPTS) by conjugating α-tocopherol polyethylene glycol derivative to the pharmacophore of simvastatin with a thioketal linker. TPTS formed nanoparticles and released parent simvastatin in the presence of hydrogen peroxide. Moreover, by taking advantage of the self-assembly behavior of TPTS, we developed a fibronectin-targeted delivery system (TPTS/C/T) to codelivery simvastatin prodrug and ticagrelor. In vitro and in vivo experiments indicated that TPTS and TPTS/C/T had good stability, which could reduce off-target leakage of drugs. They greatly inhibited the M1-type polarization of macrophages; reduced intracellular reactive oxygen species level and inflammatory cytokine; and TNF-α, MCP-1, and IL-1β were secreted by macrophage cells, thus providing enhanced anti-inflammatory and antioxidant effects compared with free simvastatin. TPTS/C/T realized targeted drug release to plaques and synergistic therapeutic effects of simvastatin and ticagrelor on atherosclerosis treatment in an ApoE-/- mouse model, resulting in excellent atherosclerosis therapeutic efficacy and a promising biosafety profile. Therefore, this study provides a new method for manufacturing statin nanodrugs and a new design idea for related responsive drug release nanosystems for atherosclerosis.

A Lysosome-Targeting Self-Condensation Prodrug-Nanoplatform System for Addressing Drug Resistance of Cancer

Lysosome-targeting self-assembling prodrugs had emerged as an attractive approach to overcome the acquisition of resistance to chemotherapeutics by inhibiting lysosomal sequestration. Taking advantage of lysosomal acidification induced intracellular hydrolytic condensation, we developed a lysosomal-targeting self-condensation prodrug-nanoplatform (LTSPN) system for overcoming lysosome-mediated drug resistance. Briefly, the designed hydroxycamptothecine (HCPT)-silane conjugates self-assembled into silane-based nanoparticles, which were taken up into lysosomes by tumor cells. Subsequently, the integrity of the lysosomal membrane was destructed because of the acid-triggered release of alcohol, wherein the nanoparticles self-condensed into silicon particles outside the lysosome through intracellular hydrolytic condensation. Significantly, the LTSPN system reduced the half-maximal inhibitory concentration (IC₅₀) of HCPT by approximately 4 times. Furthermore, the LTSPN system realized improved control of large established tumors and reduced regrowth of residual tumors in several drug-resistant tumor models. Our findings suggested that target destructing the integrity of the lysosomal membrane may improve the therapeutic effects of chemotherapeutics, providing a potent treatment strategy for malignancies.

Biomimetic Exosomes: A New Generation of Drug Delivery System

Most of the naked drugs, including small molecules, inorganic agents, and biomacromolecule agents, cannot be used directly for disease treatment because of their poor stability and undesirable pharmacokinetic behavior. Their shortcomings might seriously affect the exertion of their therapeutic effects. Recently, a variety of exogenous and endogenous nanomaterials have been developed as carriers for drug delivery. Among them, exosomes have attracted great attention due to their excellent biocompatibility, low immunogenicity, low toxicity, and ability to overcome biological barriers. However, exosomes used as drug delivery carriers have significant challenges, such as low yields, complex contents, and poor homogeneity, which limit their application. Engineered exosomes or biomimetic exosomes have been fabricated through a variety of approaches to tackle these drawbacks. We summarized recent advances in biomimetic exosomes over the past decades and addressed the opportunities and challenges of the next-generation drug delivery system.

Sustained-release nanocapsule based on a 3D COF for long-term enzyme prodrug therapy of cancer

A well-designed three-dimensional (3D) covalent organic framework (COF) was constructed as a nanocapsule for the encapsulation of horseradish peroxidase (HRP), which could realize sustained release of HRP to prolong the duration of the therapeutic agents and promote long-term enzyme prodrug therapy.

Synthesis and In-Vivo Evaluation of Benzoxazole Derivatives as Promising Anti-Psoriatic Drugs for Clinical Use

2-(4-Chlorophenyl)-5-benzoxazoleacetic acid (CBA) and its ester, methyl-2-(4-chloro-phenyl)-5-benzoxazoleacetate (MCBA), were synthesized, and their structures were confirmed by 1HNMR, IR, and mass spectrophotometry. The anti-psoriatic activities of CBA and MCBA were tested using an imiquimod (IMQ)-induced psoriatic mouse model, in which mice were treated both topically (1% w/w) and orally (125 mg/kg) for 14 days. The erythema intensity, thickness, and desquamation of psoriasis were scored by calculating the psoriasis area severity index (PASI). The study also included the determination of histopathological alterations in the skin tissues of treated mice. Topical and oral administration of CBA and MCBA led to a reduction in erythema intensity, thickness, and desquamation, which was demonstrated by a significant decrease in the PASI value. In addition, skin tissues of mice treated with CBA and MCBA showed less evidence of psoriatic alterations, such as hyperkeratosis, parakeratosis, scale crust, edema, psoriasiform, and hyperplasia. After administration of either topical or oral dosing, the anti-psoriatic effects were found to be stronger in MCBA-treated than in CBA-treated mice. These effects were comparable to those produced by Clobetasol propionate, the reference drug. This drug discovery could be translated into a potential new drug for future clinical use in psoriasis treatment.

Galactosylated Prodrugs: A Strategy to Improve the Profile of Nonsteroidal Anti-Inflammatory Drugs

Carbohydrates are one of the most abundant and important classes of biomolecules. The variety in their structures makes them valuable carriers that can improve the pharmaceutical phase, pharmacokinetics and pharmacodynamics of well-known drugs. D-galactose is a simple, naturally occurring monosaccharide sugar that has been extensively studied for use as a carrier and has proven to be valuable in this role. With the aim of validating the galactose-prodrug approach, we have investigated the galactosylated prodrugs ibuprofen, ketoprofen, flurbiprofen and indomethacin, which we have named IbuGAL, OkyGAL, FluGAL and IndoGAL, respectively. Their physicochemical profiles in terms of lipophilicity, solubility and chemical stability have been evaluated at different physiological pH values, as have human serum stability and serum protein binding. Ex vivo intestinal permeation experiments were performed to provide preliminary insights into the oral bioavailability of the galactosylated prodrugs. Finally, their anti-inflammatory, analgesic and ulcerogenic activities were investigated in vivo in mice after oral treatment. The present results, taken together with those of previous studies, undoubtedly validate the galactosylated prodrug strategy as a problem-solving technique that can overcome the disadvantages of NSAIDs.

Prodrugs of pyrophosphates and bisphosphonates: disguising phosphorus oxyanions

Pyrophosphates have important functions in living systems and thus pyrophosphate-containing molecules and their more stable bisphosphonate analogues have the potential to be used as drugs for treating many diseases including cancer and viral infections. Both pyrophosphates and bisphosphonates are polyanionic at physiological pH and, whilst this is essential for their biological activity, it also limits their use as therapeutic agents. In particular, the high negative charge density of these compounds prohibits cell entry other than by endocytosis, prevents transcellular oral absorption and causes sequestration to bone. Therefore, prodrug strategies have been developed to temporarily disguise the charges of these compounds. This review examines the various systems that have been used to mask the phosphorus-containing moieties of pyrophosphates and bisphosphonates and also illustrates the utility of such prodrugs.

Supramolecular nanomedicines through rational design of self-assembling prodrugs

Advancements in the development of nanomaterials have led to the creation of a plethora of functional constructs as drug delivery vehicles to address many dire medical needs. The emerging prodrug strategy provides an alternative solution to create nanomedicines of extreme simplicity by directly using the therapeutic agents as molecular building blocks. This Review outlines different prodrug-based drug delivery systems, highlights the advantages of the prodrug strategy for therapeutic delivery, and demonstrates how combinations of different functionalities - such as stimuli responsiveness, targeting propensity, and multidrug conjugation - can be incorporated into designed prodrug delivery systems. Furthermore, we discuss the opportunities and challenges facing this rapidly growing field.

Stimulus-responsive self-assembled prodrugs in cancer therapy

Small-molecule prodrugs have become the main toolbox to improve the unfavorable physicochemical properties of potential therapeutic compounds in contemporary anti-cancer drug development. Many approved small-molecule prodrugs, however, still face key challenges in their pharmacokinetic (PK) and pharmacodynamic (PD) properties, thus severely restricting their further clinical applications. Self-assembled prodrugs thus emerged as they could take advantage of key benefits in both prodrug design and nanomedicine, so as to maximize drug loading, reduce premature leakage, and improve PK/PD parameters and targeting ability. Notably, temporally and spatially controlled release of drugs at cancerous sites could be achieved by encoding various activable linkers that are sensitive to chemical or biological stimuli in the tumor microenvironment (TME). In this review, we have comprehensively summarized the recent progress made in the development of single/multiple-stimulus-responsive self-assembled prodrugs for mono- and combinatorial therapy. A special focus was placed on various prodrug conjugation strategies (polymer-drug conjugates, drug-drug conjugates, etc.) that facilitated the engineering of self-assembled prodrugs, and various linker chemistries that enabled selective controlled release of active drugs at tumor sites. Furthermore, some polymeric nano-prodrugs that entered clinical trials have also been elaborated here. Finally, we have discussed the bottlenecks in the field of prodrug nanoassembly and offered potential solutions to overcome them. We believe that this review will provide a comprehensive reference for the rational design of effective prodrug nanoassemblies that have clinic translation potential.

Development of Fluorophosphoramidate as a New Biocompatible Transformable Functional Group and its Application as a Phosphate Prodrug for Nucleoside Analogs

Synthetic phosphate-derived functional groups are important for controlling the function of bioactive molecules in vivo . Herein we describe the development of a new type of biocompatible phosphate analog, a fluorophosphoramidate (FPA) functional group that has characteristic P-F and P-N bonds. We found that FPA with a primary amino group was relatively unstable in aqueous solution and was converted to a monophosphate, while FPA with a secondary amino group was stable. Furthermore, by improving the molecular design of FPA, we developed a reaction in which a secondary amino group is converted to a primary amino group in the intracellular environment, and clarified that the FPA group functions as a phosphate prodrug of nucleoside. Various FPA-gemcitabine derivatives were synthesized and their anticancer activities were evaluated. One of the FPA-gemcitabine derivatives showed superior anticancer activity compared with gemcitabine and its ProTide prodrug, which methodology is widely used in various nucleoside analogs, including anti-cancer and anti-virus drugs.

Controlled Intracellular Polymerization for Cancer Treatment

Numerous prodrugs have been developed and used for cancer treatments to reduce side effects and promote efficacy. In this work, we have developed a new photoactivatable prodrug system based on intracellular photoinduced electron transfer-reversible addition-fragmentation chain-transfer (PET-RAFT) polymerization. This unique polymerization process provided a platform for the synthesis of structure-predictable polymers with well-defined structures in living cells. The intracellularly generated poly(N,N-dimethylacrylamide)s were found to induce cell cycle arrest, apoptosis, and necroptosis, inhibit cell proliferation, and reduce cancer cell motilities. This polymerization-based "prodrug" system efficiently inhibits tumor growth and metastasis both in vitro and in vivo and will promote the development of targeted and directed cancer chemotherapy.

Acacetin as a Potential Protective Compound against Cardiovascular Diseases

Acacetin (5,7-dihydroxy-4′-methoxyflavone) is the major bioactive component of the traditional Chinese medicine “Snow lotus”. As a natural flavonoid compound, it has been shown to have good pharmacological effects such as anti-inflammatory, anticancer, and anti-obesity. Among them, its prominent role in cardiovascular diseases (CVD) has received extensive attention from scholars in recent years. In this review, the protective effects of acacetin on a variety of cardiovascular diseases, as well as the existing problems and prospects, are discussed and summarized. This review also highlights the great potential of acacetin, a natural-derived Chinese medicine, as a cardiovascular agent candidate.

Particulate levodopa nose-to-brain delivery targets dopamine to the brain with no plasma exposure

Levodopa (L-DOPA) is an oral Parkinson's Disease drug that generates the active metabolite - dopamine (DA) in vivo. However, oral L-DOPA exhibits low oral bioavailability, limited brain uptake, peripheral DA-mediated side effects and its poor brain bioavailability can lead to long-term complications. Here we show that L-DOPA forms stable (for at least 5 months) 300 nm nanoparticles when encapsulated within N-palmitoyl-N-monomethyl-N,N-dimethyl-N,N,N-trimethyl-6-O-glycolchitosan (GCPQ). A nano-in-microparticle GCPQ-L-DOPA formulation (D₅₀ = 7.2 µm), prepared by spray-drying, was stable for one month when stored at room and refrigeration temperatures and was capable of producing the original GCPQ-L-DOPA nanoparticles upon aqueous reconstitution. Nasal administration of reconstituted GCPQ-L-DOPA nanoparticles to rats resulted in significantly higher DA levels in the brain (C_max of 94 ng g^-1 above baseline levels 2 h post-dosing) when compared to nasal administration of L-DOPA alone, with DA being undetectable in the brain with the latter. Furthermore, nasal GCPQ-L-DOPA resulted in higher levels of L-DOPA in the plasma (a 17-fold increase in the Cmax, when compared to L-DOPA alone) with DA undetectable in the plasma from both formulations. These data provide evidence of effective delivery of DA to the brain with the GCPQ-L-DOPA formulation.

Photoresponsive prodrug‐dye nanoassembly for in‐situ monitorable cancer therapy

Photocleavable prodrugs enable controllable drug delivery to target sites modulated by light irradiation. However, the in vivo utility is usually hindered by their insolubility and inefficient delivery. In this study, we report a simple strategy of co‐assembling boron‐dipyrromethene‐chlorambucil prodrug and near‐infrared dye IR783 to fabricate photoresponsive nanoassemblies, which achieved both high prodrug loading capacity (~99%) and efficient light‐triggered prodrug activation. The incorporated IR783 dye not only stabilized the nanoparticles and contributed tumor targeting as usual, but also exhibited degradation after light irradiation and in‐situ monitoring of nanoparticle dissociation by fluorescent imaging. Systemic administration of the nanoparticles and localized light irradiation at tumor sites enabled monitorable and efficient drug release in vivo. Our results demonstrate that such prodrug‐dye co‐assembled nanomedicine is a promising formulation for photoresponsive drug delivery, which would advance the translation of photoresponsive nanomedicines.

Programmable siRNA pro-drugs that activate RNAi activity in response to specific cellular RNA biomarkers

Since Paul Ehrlich's introduction of the "magic bullet" concept in 1908, drug developers have been seeking new ways to target drug activity to diseased cells while limiting effects on normal tissues. In recent years, it has been proposed that coupling riboswitches capable of detecting RNA biomarkers to small interfering RNAs (siRNAs) to create siRNA pro-drugs could selectively activate RNA interference (RNAi) activity in specific cells. However, this concept has not been achieved previously. We report here that we have accomplished this goal, validating a simple and programmable new design that functions reliably in mammalian cells. We show that these conditionally activated siRNAs (Cond-siRNAs) can switch RNAi activity against different targets between clearly distinguished OFF and ON states in response to different cellular RNA biomarkers. Notably, in a rat cardiomyocyte cell line (H9C2), one version of our construct demonstrated biologically meaningful inhibition of a heart-disease-related target gene protein phosphatase 3 catalytic subunit alpha (PPP3CA) in response to increased expression of the pathological marker atrial natriuretic peptide (NPPA) messenger RNA (mRNA). Our results demonstrate the ability of synthetic riboswitches to regulate gene expression in mammalian cells, opening a new path for development of programmable siRNA pro-drugs.

Light-Triggered Polymersome-Based Anticancer Therapeutics Delivery

Polymersomes are biomimetic cell membrane-like model structures that are self-assembled stepwise from amphiphilic copolymers. These polymeric (nano)carriers have gained the scientific community’s attention due to their biocompatibility, versatility, and higher stability than liposomes. Their tunable properties, such as composition, size, shape, and surface functional groups, extend encapsulation possibilities to either hydrophilic or hydrophobic cargoes (or both) and their site-specific delivery. Besides, polymersomes can disassemble in response to different stimuli, including light, for controlling the “on-demand” release of cargo that may also respond to light as photosensitizers and plasmonic nanostructures. Thus, polymersomes can be spatiotemporally stimulated by light of a wide wavelength range, whose exogenous response may activate light-stimulable moieties, enhance the drug efficacy, decrease side effects, and, thus, be broadly employed in photoinduced therapy. This review describes current light-responsive polymersomes evaluated for anticancer therapy. It includes light-activable moieties’ features and polymersomes’ composition and release behavior, focusing on recent advances and applications in cancer therapy, current trends, and photosensitive polymersomes’ perspectives.

Contributions of Cathepsin A and Carboxylesterase 1 to the Hydrolysis of Tenofovir Alafenamide in the Human Liver, and the Effect of CES1 Genetic Variation on Tenofovir Alafenamide Hydrolysis

The prodrug tenofovir alafenamide (TAF) is a first-line antiviral agent for the treatment of chronic hepatitis B infection. TAF activation involves multiple steps, and the first step is an ester hydrolysis reaction catalyzed by hydrolases. This study was to determine the contributions of carboxylesterase 1 (CES1) and cathepsin A (CatA) to TAF hydrolysis in the human liver. Our in vitro incubation studies showed that both CatA and CES1 catalyzed TAF hydrolysis in a pH-dependent manner. At their physiologic pH environment, the activity of CatA (pH 5.2) was approximately 1,000-fold higher than that of CES1 (pH 7.2). Given that the hepatic protein expression of CatA was approximately 200-fold lower than that of CES1, the contribution of CatA to TAF hydrolysis in the human liver was estimated to be much greater than that of CES1, which is contrary to the previous perception that CES1 is the primary hepatic enzyme hydrolyzing TAF. The findings were further supported by a TAF incubation study with the CatA inhibitor telaprevir and the CES1 inhibitor bis-(p-nitrophenyl) phosphate. Moreover, an in vitro study revealed that the CES1 variant G143E (rs71647871) is a loss-of-function variant for CES1-mediated TAF hydrolysis. In summary, our results suggest that CatA may play a more important role in the hepatic activation of TAF than CES1. Additionally, TAF activation in the liver could be affected by CES1 genetic variation, but the magnitude of impact appears to be limited due to the major contribution of CatA to hepatic TAF activation. SIGNIFICANCE STATEMENT: Contrary to the general perception that carboxylesterase 1 (CES1) is the major enzyme responsible for tenofovir alafenamide (TAF) hydrolysis in the human liver, the present study demonstrated that cathepsin A may play a more significant role in TAF hepatic hydrolysis. Furthermore, the CES1 variant G143E (rs71647871) was found to be a loss-of-function variant for CES1-mediated TAF hydrolysis.

Computational Investigation of the Bisphenolic Drug Metabolism by Cytochrome P450: What Factors Favor Intramolecular Phenol Coupling

Intramolecular phenol coupling reactions of alkaloids can lead to active metabolites catalyzed by the mammalian cytochrome P450 enzyme (P450); however, the mechanistic knowledge of such an "unusual" process is lacking. This work performs density functional theory computations to reveal the P450-mediated metabolic pathway leading from R-reticuline to the morphine precursor salutaridine by exploring possible intramolecular phenol coupling mechanisms involving diradical coupling, radical addition, and electron transfer. The computed results show that the outer-sphere electron transfer with a high barrier (>20.0 kcal/mol) is unlikely to happen. However, for inter-sphere intramolecular phenol coupling, it reveals that intramolecular phenol coupling of R-reticuline proceeds via the diradical mechanism consecutively by compound I and protonated compound II of P450 rather than the radical addition mechanism. The existence of a much higher radical rebound barrier than that of H-abstraction in the quartet high-spin state can endow the R-reticuline phenoxy radical with a sufficient lifetime to enable intramolecular phenol coupling, while the H-abstraction/radical rebound mode with a negligible rebound barrier leading to phenol hydroxylation can only happen in the doublet low-spin state. Therefore, the ratio [coupling]/[hydroxylation] can be approximately reflected by the relative yield of the high-spin and low-spin H-abstraction by P450, which thus can provide a theoretical ratio of 16:1 for R-reticuline, which is in accordance with previous experimental results. Especially, the high rebound barrier of the phenoxy radical derived from the weak electron-donating ability of the phenoxy radical is revealed as an intrinsic nature. Therefore, the revealed intramolecular phenol coupling mechanism can be potentially extended to several other bisphenolic drugs to infer groups of unexpected metabolites in organisms.

Elastase-Activated Antimicrobial Peptide for a Safer Pulmonary Treatment of Cystic Fibrosis Infections

As bioactive small proteins with antimicrobial and immunomodulatory activities that are naturally produced by all living organisms, antimicrobial peptides (AMPs) have a marked potential as next-generation antibiotics. However, their development as antibacterial agents is limited by low stability and cytotoxicity. D-BMAP18, a membrane-permeabilizing antimicrobial peptide composed of D-amino acids, has shown good antibacterial and anti-inflammatory activities but also a non-negligible cytotoxicity against eukaryotic cell lines. In this study, a prodrug has been developed that extends the peptide with a negatively charged, inactivating sequence containing the cleavage site for neutrophil elastase (NE). The ultimate goal was to allow the activation of D-BMAP18 by endogenous elastase only at the site of infection/inflammation, enabling a slow and targeted release of the pharmacologically active peptide. In vitro activation of Pro-D-BMAP18 was confirmed using purified NE. Its antimicrobial and cytotoxic activities were tested in the presence and absence of elastase and compared to those of the parental form. The prodrug had minimal activity in the absence of elastase, while its proteolysis product retained an appreciable antimicrobial activity but lower cytotoxicity. Moreover, Pro-D-BMAP18 was found to be correctly converted to D-BMAP18 in the presence of CF sputum as a model of the lung environment and showed good antimicrobial activity under these conditions.

Prodrug Therapies for Infectious and Neurodegenerative Diseases

Prodrugs are bioreversible drug derivatives which are metabolized into a pharmacologically active drug following chemical or enzymatic modification. This approach is designed to overcome several obstacles that are faced by the parent drug in physiological conditions that include rapid drug metabolism, poor solubility, permeability, and suboptimal pharmacokinetic and pharmacodynamic profiles. These suboptimal physicochemical features can lead to rapid drug elimination, systemic toxicities, and limited drug-targeting to disease-affected tissue. Improving upon these properties can be accomplished by a prodrug design that includes the careful choosing of the promoiety, the linker, the prodrug synthesis, and targeting decorations. We now provide an overview of recent developments and applications of prodrugs for treating neurodegenerative, inflammatory, and infectious diseases. Disease interplay reflects that microbial infections and consequent inflammation affects neurodegenerative diseases and vice versa, independent of aging. Given the high prevalence, personal, social, and economic burden of both infectious and neurodegenerative disorders, therapeutic improvements are immediately needed. Prodrugs are an important, and might be said a critical tool, in providing an avenue for effective drug therapy.

Cysteine Donor-Based Brain-Targeting Prodrug: Opportunities and Challenges

Overcoming blood-brain barrier (BBB) to improve brain bioavailability of therapeutic drug remains an ongoing concern. Prodrug is one of the most reliable approaches for delivering agents with low-level BBB permeability into the brain. The well-known antioxidant capacities of cysteine (Cys) and its vital role in glutathione (GSH) synthesis indicate that Cys-based prodrug could potentiate therapeutic drugs against oxidative stress-related neurodegenerative disorders. Moreover, prodrug with Cys moiety could be recognized by the excitatory amino acid transporter 3 (EAAT3) that is highly expressed at the BBB and transports drug into the brain. In this review, we summarized the strategies of crossing BBB, properties of EAAT3 and its natural substrates, Cys and its donors, and Cys donor-based brain-targeting prodrugs by referring to recent investigations. Moreover, the challenges that we are faced with and future research orientations were also addressed and proposed. It is hoped that present review will provide evidence for the pursuit of novel Cys donor-based brain-targeting prodrug.

Recent advances in the surfactant and controlled release polymer-based solid dispersion

The oral route is the most preferred delivery route for drug administration due to its advantages such as lower cost, improved patient compliance, no need for trained personnel and the drug reactions are generally less severe. The major problem with new molecules in the drug discovery pipeline is poor solubility and dissolution rate that ultimately results in low oral bioavailability. Numerous techniques are available for solubility and bioavailability (BA) enhancement, but out of all, solid dispersion (SD) is proven to be the most feasible due to the least issues in manufacturing, processing, storage, and transportation. In the past few years, SD had been extensively applied to reinforce the common issues of insoluble drugs. Currently, many hydrophobic and hydrophilic polymers are used to prepare either immediate release or controlled release SDs. Therefore, the biological behavior of the SDs is contingent upon the use of appropriate polymeric carriers and methods of preparation. The exploration of novel carriers and methodologies in SD technology leads to improved BA and therapeutic effectiveness. Moreover, the clinical applicability of SD-based formulations has been increased with the discovery of novel polymeric carriers. In this review, emphasis is laid down on the present status of recent generations of SDs (i.e., surfactant and controlled release polymer-based SD) and their application in modifying the physical properties of the drug and modulation of pharmacological response in different ailments.

The microbiome and precision oncology: an emerging paradigm in anticancer therapy

Understanding the host-microbiome interactions has emerged as an essential factor in improving human health and disease. Recent advances in understanding the intimate relationship of microbes with the host have uncovered various previously unknown underlying causes of disease development, progression, and treatment failure. The dynamic behaviour of the microbiome confers the heterogeneity in treatment response by modulating the immune response and inflammation in various diseases, including cancer. The growing insights into the microbial modulation of cancer through immunoregulation, xenometabolism, and increase in toxicity open a new era of personalised medicine. In the current review, we discuss the essential roles played by the microbiome in modulating the efficacy and toxicity of anticancer therapies (immunotherapy, chemotherapy, and radiotherapy). We also outline the current state of personalised medicine in the context of cancer and microbiome modulation. The knowledge about the role of cancer-microbiome communication will lead to designing other precise microbial modulation strategies for cancer treatment through enhanced efficacy and decreased toxicity.

Cathepsin B - A Neuronal Death Mediator in Alzheimer’s Disease Leads to Neurodegeneration

Abstract:

The lysosomal cysteine protease enzyme, named Cathepsin B, mainly degrades the protein and manages its average turnover in our body. The Cathepsin B active form is mostly present inside the lysosomal part at a cellular level, providing the slightly acidic medium for its activation. Multiple findings on Cathepsin B reveal its involvement in neurons' degeneration and a possible role as a neuronal death mediator in several neurodegenerative diseases. In this review article, we highlight the participation of Cathepsin B in the etiology/progress of AD, along with various other factors. The enzyme is involved in producing neurotoxic Aβ amyloid in the AD brain by acting as the β-secretase enzyme in the regulated secretory pathways responsible for APP processing. Aβ amyloid accumulation and amyloid plaque formation lead to neuronal degeneration, one of the prominent pathological hallmarks of AD. Cathepsin B is also involved in the production of PGlu-Aβ, which is a truncated and highly neurotoxic form of Aβ. Some of the findings also revealed that Cathepsin B specific gene deletion decreases the level of PGlu-Aβ inside the brain of experimental mice. Therefore, neurotoxicity might be considered a new pathological indication of AD due to the involvement of Cathepsin B. It also damages neurons present in the CNS region by producing inflammatory responses and generating mitochondrial ROS. However, Cathepsin B inhibitors, i.e., CA-074, can prevent neuronal death in AD patients. The other natural inhibitors are also equally effective against neuronal damage with higher selectivity. Its synthetic inhibitors are specific for their target; however, they lose their selectivity in the presence of quite a few reducing agents. Therefore, a humanized monoclonal antibody is used as a selective Cathepsin B inhibitor to overcome the problem experienced. The use of Cathepsin B for the treatment of AD and other neurodegenerative diseases could be considered a rational therapeutic target.

Nanodiscs: a versatile nanocarrier platform for cancer diagnosis and treatment

Cancer therapy is a significant challenge due to insufficient drug delivery to the cancer cells and non-selective killing of healthy cells by most chemotherapy agents. Nano-formulations have shown great promise for targeted drug delivery with improved efficiency. The shape and size of nanocarriers significantly affect their transport inside the body and internalization into the cancer cells. Non-spherical nanoparticles have shown prolonged blood circulation half-lives and higher cellular internalization frequency than spherical ones. Nanodiscs are desirable nano-formulations that demonstrate enhanced anisotropic character and versatile functionalization potential. Here, we review the recent development of theranostic nanodiscs for cancer mitigation ranging from traditional lipid nanodiscs encased by membrane scaffold proteins to newer nanodiscs where either the membrane scaffold proteins or the lipid bilayers themselves are replaced with their synthetic analogues. We first discuss early cancer detection enabled by nanodiscs. We then explain different strategies that have been explored to carry a wide range of payloads for chemotherapy, cancer gene therapy, and cancer vaccines. Finally, we discuss recent progress on organic-inorganic hybrid nanodiscs and polymer nanodiscs that have the potential to overcome the inherent instability problem of lipid nanodiscs.

Drug/Lead Compound Hydroxymethylation as a Simple Approach to Enhance Pharmacodynamic and Pharmacokinetic Properties

Hydroxymethylation is a simple chemical reaction, in which the introduction of the hydroxymethyl group can lead to physical–chemical property changes and offer several therapeutic advantages, contributing to the improved biological activity of drugs. There are many examples in the literature of the pharmaceutical, pharmacokinetic, and pharmacodynamic benefits, which the hydroxymethyl group can confer to drugs, prodrugs, drug metabolites, and other therapeutic compounds. It is worth noting that this group can enhance the drug’s interaction with the active site, and it can be employed as an intermediary in synthesizing other therapeutic agents. In addition, the hydroxymethyl derivative can result in more active compounds than the parent drug as well as increase the water solubility of poorly soluble drugs. Taking this into consideration, this review aims to discuss different applications of hydroxymethyl derived from biological agents and its influence on the pharmacological effects of drugs, prodrugs, active metabolites, and compounds of natural origin. Finally, we report a successful compound synthesized by our research group and used for the treatment of neglected diseases, which is created from the hydroxymethylation of its parent drug.

Applications of the ROS-Responsive Thioketal Linker for the Production of Smart Nanomedicines

Reactive oxygen species (ROS)-sensitive drug delivery systems (DDS) specifically responding to altered levels of ROS in the pathological microenvironment have emerged as an effective means to enhance the pharmaceutical efficacy of conventional nanomedicines, while simultaneously reducing side effects. In particular, the use of the biocompatible, biodegradable, and non-toxic ROS-responsive thioketal (TK) functional group in the design of smart DDS has grown exponentially in recent years. In the design of TK-based DDS, different technological uses of TK have been proposed to overcome the major limitations of conventional DDS counterparts including uncontrolled drug release and off-target effects. This review will focus on the different technological uses of TK-based biomaterials in smart nanomedicines by using it as a linker to connect a drug on the surface of nanoparticles, form prodrugs, as a core component of the DDS to directly control its structure, to control the opening of drug-releasing gates or to change the conformation of the nano-systems. A comprehensive view of the various uses of TK may allow researchers to exploit this reactive linker more consciously while designing nanomedicines to be more effective with improved disease-targeting ability, providing novel therapeutic opportunities in the treatment of many diseases.

Paclitaxel Drug Delivery Systems: Focus on Nanocrystals' Surface Modifications

Paclitaxel (PTX) is a chemotherapeutic agent that belongs to the taxane family and which was approved to treat various kinds of cancers including breast cancer, ovarian cancer, advanced non-small-cell lung cancer, and acquired immunodeficiency syndrome (AIDS)-related Kaposi’s sarcoma. Several delivery systems for PTX have been developed to enhance its solubility and pharmacological properties involving liposomes, nanoparticles, microparticles, micelles, cosolvent methods, and the complexation with cyclodextrins and other materials that are summarized in this article. Specifically, this review discusses deeply the developed paclitaxel nanocrystal formulations. As PTX is a hydrophobic drug with inferior water solubility properties, which are improved a lot by nanocrystal formulation. Based on that, many studies employed nano-crystallization techniques not only to improve the oral delivery of PTX, but IV, intraperitoneal (IP), and local and intertumoral delivery systems were also developed. Additionally, superior and interesting properties of PTX NCs were achieved by performing additional modifications to the NCs, such as stabilization with surfactants and coating with polymers. This review summarizes these delivery systems by shedding light on their route of administration, the methods used in the preparation and modifications, the in vitro or in vivo models used, and the advantages obtained based on the developed formulations.

Synthesis and Preliminary Evaluation of the Cytotoxicity of Potential Metabolites of Quinoline Glycoconjugates

The design of prodrugs is one of the important strategies for selective anti-cancer therapies. When designing prodrugs, attention is paid to the possibility of their targeting tumor-specific markers such as proteins responsible for glucose uptake. That is why glycoconjugation of biologically active compounds is a frequently used strategy. Glycoconjugates consisting of three basic building blocks: a sugar unit, a linker containing a 1,2,3-triazole ring, and an 8-hydroxyquinoline fragment was described earlier. It is not known whether their cytotoxicity is due to whole glycoconjugates action or their metabolites. To check the biological activity of products that can be released from glycoconjugates under the action of hydrolytic enzymes, the synthetically obtained potential metabolites were tested in vitro for the inhibition of proliferation of HCT-116, MCF-7, and NHDF-Neo cell lines using the MTT assay. Research shows that for the full activity of glycoconjugates, the presence of all three building blocks in the structure of a potential drug is necessary. For selected derivatives, additional tests of targeted drug delivery to tumor cells were carried out using polymer nanocarriers in which they are encapsulated. This approach significantly lowered the determined IC₅₀ values of the tested compounds and improved their selectivity and effectiveness.

Engineering of small-molecule lipidic prodrugs as novel nanomedicines for enhanced drug delivery

A widely established prodrug strategy can effectively optimize the unappealing properties of therapeutic agents in cancer treatment. Among them, lipidic prodrugs extremely uplift the physicochemical properties, site-specificity, and antitumor activities of therapeutic agents while reducing systemic toxicity. Although great perspectives have been summarized in the progress of prodrug-based nanoplatforms, no attention has been paid to emphasizing the rational design of small-molecule lipidic prodrugs (SLPs). With the aim of outlining the prospect of the SLPs approach, the review will first provide an overview of conjugation strategies that are amenable to SLPs fabrication. Then, the rational design of SLPs in response to the physiological barriers of chemotherapeutic agents is highlighted. Finally, their biomedical applications are also emphasized with special functions, followed by a brief introduction of the promising opportunities and potential challenges of SLPs-based drug delivery systems (DDSs) in clinical application.

Graphical Abstract

Synthesis of Ester-Substituted Indolo[2,1-a]isoquinolines via Photocatalyzed Alkoxycarbonylation/Cyclization Reactions

A direct alkoxycarbonylation/cyclization reaction is accomplished under visible light-induced photoredox catalysis. With this approach, a variety of ester-substituted indolo[2,1-a]isoquinolines are prepared in good to excellent yields. It is worth noting that this method not only can afford the synthesis of indolo[2,1-a]isoquinolines but also can provide an alternative route for generating complex target structures bearing carboxylic esters.