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

Emerging prodrug and nano-drug delivery strategies for the detection and elimination of senescent tumor cells

Tumor cellular senescence, characterized by reversible cell cycle arrest following anti-cancer therapies, presents a complex paradigm in oncology. Given that senescent tumor cells may promote angiogenesis, tumorigenesis, and metastasis, selective killing senescent cells (SCs)-a strategy termed senotherapy-has emerged as a promising approach to improve cancer treatment. However, the clinical implementation of senotherapy faces significant hurdles, including lack of precise methods for SCs identification and the potential for adverse effects associated with highly cytotoxic senolytic agents. In this account, we elucidate recent advancement in developing novel approaches for the detection and selective elimination of SCs, encompassing prodrugs, nanoparticles, and other cutting-edge drug delivery systems such as PROTAC technology and CAR T cell therapy. Furthermore, we explore the paradoxical nature of SCs, which can induce growth arrest in adjacent neoplastic cells and recruit immunomodulatory cells that contribute to tumor suppression. Therefore, we utilize SCs membrane as vehicles to elicit antitumor immunity and potentially augment existing anti-cancer therapies. Finally, the opportunities and challenges are put forward to facilitate the development and clinical transformation of SCs detection, elimination or utilization.

Antioxidants in anti-Alzheimer's disease drug discovery

Oxidative stress is widely recognized as a key contributor to the pathogenesis of Alzheimer's disease (AD). While not the sole factor, it is closely linked to critical pathological features, such as the formation of senile plaques and neurofibrillary tangles. The development of agents with antioxidant properties has become an area of growing interest in AD research. Between 2015 and 2024, several antioxidant-targeted drugs for AD progressed to clinical trials, with increasing attention to the evaluation of antioxidant properties during their development. Oxidative stress plays a pivotal role in linking various AD hypotheses, underscoring its importance in understanding the disease mechanisms. Despite this, comprehensive reviews addressing advancements in AD drug development from the perspective of antioxidant capacity remain limited, hindering the design of novel compounds. This review aims to explore the mechanistic relationship between oxidative stress and AD, summarize methods for assessing antioxidant capacity, and provide an overview of antioxidant compounds with anti-AD properties reported over the past decade. The goal is to offer strategies for identifying effective antioxidant-based therapies for AD and to deepen our understanding of the role of oxidative stress in AD pathology.

Non-covalent binding of non-steroidal anti-inflammatory drugs to antibiotics: preparation, characterization, physicochemical properties and study of single crystals of tolfenamic acid-enrofloxacin drug-drug salt and their antibacterial and anti-inflammatory activities

To improve the physicochemical properties and biological activities of the nonsteroidal anti-inflammatory drug tolfenamic acid (TA) and the fluoroquinolone enrofloxacin (ENR). Based on the previous experience of our group in designing and synthesizing quinolone pharmaceutical co-crystals/salts single crystals by non-covalent bonding to improve their physicochemical properties, a drug-drug salt single crystal of tolfenamic acid-enrofloxacin was prepared for the first time using TA and ENR(TA-ENR, C19H23FN3O3·C14H11ClNO2·C2H3N). Single-crystal X-ray diffraction (SCXRD) analysis indicated that TA and ENR interacted predominantly through charge-assisted hydrogen bonds (CAHBs) within non-covalent bonds to form asymmetric units. Subsequently, the formation of dimers between ENR+ cations in adjacent asymmetric units was promoted, leading to the formation of a stable crystalline structure through C6-H6···O2 and π···π stacking. Solubility experiments demonstrated that the solubility of TA-ENR was notably increased compared to TA. This can be ascribed to the CAHBs formed between TA and ENR, which facilitated the dissociation of TA in the dissolution medium, thereby enhancing TA's affinity for the dissolution medium. Permeability experiments also revealed that the permeability of TA-ENR was significantly improved compared to both TA and ENR. The in vitro antimicrobial activity and anti-inflammatory activity of TA-ENR were also somewhat improved compared to TA and ENR. The success of this work implies that we may provide new ideas for designing and synthesizing solid drugs with better physicochemical properties and bioactivity, as well as for the treatment of septic arthritis, through the formation of drug-drug co-crystals/salts.

Design and Development of a Novel Oral 4'-Fluorouridine Double Prodrug VV261 against SFTSV

4'-Fluorouridine (4'-FU), despite demonstrating potent anti-SFTSV efficacy in vitro and in vivo, faces hindrances in its further development as a promising drug due to its weak chemical stability. Here, we report the discovery and development of VV261, a novel 4'-FU double prodrug with three isobutyryl groups on the ribose moiety and a nicotinoyloxymethyl group linked to the imide-nitrogen on the base moiety, exhibiting notable chemical stability and favorable pharmacokinetic properties. In SFTSV-infected mice, VV261 at 5 mg/kg/d for 7 days demonstrated complete protection against lethal SFTSV infection, prevented weight loss, and even a 2 day treatment significantly reduced both viral RNA copies and infectious virus titers in multiple organs, and notably alleviated splenic tissue lesions. After further preclinical evaluations, VV261, identified as a promising candidate drug for the treatment of SFTS, has entered Phase I clinical trials in China, the first such candidate to reach this stage for SFTS.

Light-Triggered Bioorthogonal Nanozyme Hydrogels for Prodrug Activation and Treatment of Bacterial Biofilms

Bioorthogonal nanozymes offer in situ activation of pro-dyes and prodrugs using abiotic chemical transformations. Bacterial infections, especially biofilm-associated infections, are extremely difficult to treat due to obstacles such as poor antibiotic penetration and the rising threat of antibiotic resistance. Spatiotemporal control of bioorthogonal catalysis provides a strategy for "on-demand" generation of therapeutics, effectively localizing therapeutic action and minimizing side effects. Here, we present the fabrication of visible-light-responsive alginate hydrogel beads embedded with bioorthogonal polyzymes (PZs). Exposure to a 405 nm light induces the reduction of Fe(III) to Fe(II), triggering the dissolution of the PZ-gel beads with concomitant release and activation of the polyzyme. This approach enabled the selective activation of a prodrug of Linezolid, a last-in-line antibiotic for Gram-positive bacterial infections, enabling the targeted eradication of multidrug-resistantStaphylococcus aureus biofilms. Overall, the use of alginate biomaterial along with noninvasive visible light offers a nontoxic platform for spatiotemporal release of antibiotics through bioorthogonal activation.

Formulation Strategy of BCS-II Drugs by Coupling Mechanistic In-Vitro and Nonclinical In-Vivo Data with PBPK: Fundamentals of Absorption-Dissolution to Parameterization of Modelling and Simulation

BCS class II candidates pose challenges in drug development due to their low solubility and permeability. Researchers have explored various techniques; co-amorphous and solid dispersion are major approaches to enhance in-vitro drug solubility and dissolution. However, in-vivo oral bioavailability remains challenging. Physiologically based pharmacokinetic (PBPK) modeling with a detailed understanding of drug absorption, distribution, metabolism, and excretion (ADME) using a mechanistic approach is emerging. This review summarizes the fundamentals of the PBPK, dissolution-absorption models, parameterization of oral absorption for BCS class II drugs, and provides information about newly emerging artificial intelligence/machine learning (AI/ML) linked PBPK approaches with their advantages, disadvantages, challenges and areas of further exploration. Additionally, the fully integrated workflow for formulation design for investigational new drugs (INDs) and virtual bioequivalence for generic molecules falling under BCS-II are discussed.

Synthesis and In Vitro Profiling of Psilocin Derivatives: Improved Stability and Synthetic Properties

As interest in using psilocybin therapy for treating mental health disorders intensifies, the need for efficient production methods becomes increasingly important. Current medical-grade psilocybin production is inefficient and relies on a complicated multistep synthesis. This study has explored and evaluated psilocin ester prodrugs and psilocin salts as potential alternatives to psilocybin, focusing on their ease of synthesis, chemical stability, and metabolic profiles. A diverse library of 15 psilocin ester prodrugs and six psilocin salts was synthesized and evaluated. The study successfully identified several psilocin ester prodrugs and psilocin salts that exhibited desirable characteristics, including storage and handling stability, rapid metabolic conversion to psilocin, and easy synthesis, with potential advantages over psilocybin. This research introduces viable options through psilocin ester compounds and psilocin salts, offering promising avenues for future development.

Synergistic Cancer Therapy: An NIR-Activated Methylene Blue-Nitrogen Mustard Prodrug for Combined Chemotherapy and Photodynamic Therapy

Nitrogen mustard, a widely used chemotherapeutic agent for more than 70 years, exhibits significant efficacy. However, its clinical applications are severely limited by poor tumor selectivity and severe side effects on normal tissues. To address these limitations, we developed a near-infrared (NIR)-activatable nitrogen mustard prodrug, MBNM. Upon NIR irradiation, the controlled cleavage of the urea bond within MBNM facilitates the simultaneous release of nitrogen mustard and methylene blue (MB), enabling a synergistic approach combining chemotherapy and photodynamic therapy (PDT) for effective tumor suppression. Moreover, the release of MB upon activation enables real-time monitoring of prodrug activation. Notably, MBNM demonstrated significantly improved biosafety compared to free nitrogen mustard. These findings suggest that the photocleavable prodrug MBNM offers a promising strategy for safe and effective combination cancer therapy.

Photocatalytic Regioselective Alkoxycarbonylation/Cyclization of 3-Aza-1,5-dienes: Access to Ester-Containing Pyrrolin-2-ones

A direct alkoxycarbonyl radical-induced cascade reaction of 3-aza-1,5-dienes with alkyl chlorooxoacetates is reported. With this approach, an extensive range of ester-containing pyrrolin-2-ones are synthesized through photocatalyzed alkoxycarbonylation/cyclization with 3-aza-1,5-dienes under mild conditions. Moreover, dehydrogenative aromatization can proceed with the same photocatalytic system.

Synthesis of Ester-Substituted Polycyclic N-Heteroaromatics via Photocatalyzed Alkoxycarbonylation/Tricyclization Reactions of Enediyne in Continuous Flow Conditions

For the first time, a photoredox-catalyzed alkoxycarbonylation/tricyclization reaction was developed by employing readily accessible enediynes and alkyloxalyl chlorides as starting materials, enabling the synthesis of ester-substituted polycyclic N-heteroaromatics under mild conditions through a radical-mediated mechanism. This photocatalytic strategy is notable for its exceptional compatibility with diverse functional groups, scalability, and efficiency in the formation of rings and chemical bonds. Notably, continuous flow photocatalysis technology markedly improved these reactions compared to the equivalent batch reactions, efficiently decreasing the reaction times to merely 40 min.

Immunoproteasome as a Target for Prodrugs

Immunoproteasome (iCP) is a proteasome isoform that is expressed under inflammatory conditions such as cytokine interferon-γ exposure. The iCP has different catalytic subunits other than the standard CP (standard core particle), allowing the production of major histocompatibility complex class I (MHC-I) compatible peptides for eventual T-cell activation. We have previously reported the design of a fluorescent probe that monitors iCP activity in cells called TBZ-1, and we applied TBZ-1's iCP recognition sequence for prodrug release into iCP-active cells. Here, we demonstrate a proof-of-concept of the iCP as a prodrug release enzyme. The "payload" we utilized was a toxic moiety, doxorubicin, and a degrader for transcription factor, BRD4. Both examples show that iCP activity is required to elicit cell death or degradation of BRD4. This report highlights that the iCP is a viable prodrug target, and its activity can be used to release a variety of cargo in cells expressing the iCP.

Current Approaches and Strategies Applied in First-in-class Drug Discovery

First-in-class drug discovery (FICDD) offers novel therapies, new biological targets and mechanisms of action (MOAs) toward targeting various diseases and provides opportunities to understand unexplored biology and to target unmet diseases. Current screening approaches followed in FICDD for discovery of hit and lead molecules can be broadly categorized and discussed under phenotypic drug discovery (PDD) and target-based drug discovery (TBDD). Each category has been further classified and described with suitable examples from the literature outlining the current trends in screening approaches applied in small molecule drug discovery (SMDD). Similarly, recent applications of functional genomics, structural biology, artificial intelligence (AI), machine learning (ML), and other such advanced approaches in FICDD have also been highlighted in the article. Further, some of the current medicinal chemistry strategies applied during discovery of hits and optimization studies such as hit-to-lead (HTL) and lead optimization (LO) have been simultaneously overviewed in this article.

Surface-enhanced Raman spectroscopy as effective tool for detection of sialic acid as cancer biomarker

Sialic acid, a negatively charged nine-carbon monosaccharide, is mainly located at the terminal end of glycan chains on glycoproteins and glycolipids of cell surface and most secreted proteins. Elevated levels of sialylated glycans have been known as a hallmark in numerous cancers. As a result, sialic acid acts as a useful and accessible cancer biomarker for early cancer detection and monitoring the disease development during cancer treatment which is crucial in elevating the survival rate. The detection of sialic acid has been done by many tools including surface-enhanced Raman spectroscopy (SERS) which gained incredible attention due to its high selectivity and sensitivity. However, currently, comprehensive reviews of sialic acid detection and imaging as a cancer biomarker using SERS are still lacking. Here, we present the significant breakthroughs in SERS-based detection of sialic acid levels on cells, tissues, and body fluids due to the presence of cancer, different cancer metastasis stages, and in response to the external stimuli. This review covers the SERS substrate and novel SERS strategies, using lectin, boronic acid, metabolic glycan labelling and label-free methods, for sialic acid detection as cancer biomarker. The remaining challenges to detect sialic acid and prospect of future development of SERS for other carbohydrate-based cancer biomarker, for instance fucose, are also discussed.

Light-mediated activation/deactivation control and in vitro ADME-Tox profiling of a donepezil-like Dual AChE/MAO-B Inhibitor

The possibility to control the effects of drugs in time and space represents an ideal condition for developing safer and more personalized therapies against different disorders. In this context, photopharmacology has paved the way for the use of light in the modulation of drugs activity. Our interest is directed to photo-switchable molecules, capable of interconverting between two different isoforms upon light irradiation. We recently reported 1, a donepezil-like compound based on 2-benzylidenindan-1-one structure, as a dual AChE and MAO-B inhibitor, which can be converted into the E- (active form) and Z- (about tenfold less active form) diastereoisomers by irradiating with UV-vis light. Aiming at identifying compounds with remarkable activity in physiological conditions, we herein report a fine characterization of 1 in PBS solutions. First, we evaluated its ability to act as a photoswitch comparing PBS solution with organic solvents (e.g. methanol), demonstrating that a wavelength in the UV range (330 nm) can convert the E- into the Z-diastereoisomer, while the use of a visible light (400 nm) allows the interconversion from Z to E in both media. Along with its photoinducible behavior, we investigated the passive diffusion across cellular membrane with PAMPA experiments, plasma and microsomal stability, and binding to plasma proteins. Interestingly, the results of such studies suggested that 1 could persist in the blood circulation for a long time, which is desirable for application in photopharmacological therapies. Cytotoxicity studies highlighted the potential of our prototypic compound as a lead photodrug against neurodegenerative disorders, deserving to advance in molecular optimization studies and further in vitro and in vivo characterization.

Optimizing Triglyceride Prodrugs of a Model Immunomodulator: Conjugation through the Phenol of Mycophenolic Acid (MPA) Markedly Promotes Lymphatic Drug Transport

Enhanced transport of immunomodulators via the lymphatics may increase drug exposure to therapeutic targets in the immune system. Our laboratory has demonstrated a triglyceride (TG) mimetic prodrug approach to enhance the lymphatic delivery of a model immunomodulator, mycophenolic acid (MPA), via conjugation of the carboxylic acid of MPA to a TG backbone, where the so formed prodrug is able to incorporate into intestinal TG deacylation-reacylation and lymph lipoprotein transport pathways (up to 37% of the administered dose being absorbed via the lymphatics). In the current study, another conjugation site in the molecule of MPA, i.e., the phenolic group, was explored for its potential to optimize the lymphatic transport profiles of TG mimetic prodrugs of MPA. This offers an unusual opportunity to directly compare the utility of TG prodrugs formed via conjugation to an acid versus a phenol in the same core molecule, which has not been examined previously for other parent drugs. A series of linkers were examined to connect the MPA moiety with the TG backbone. Lymphatic transport was assessed in mesenteric lymph duct cannulated rats, and drug exposure in the mesenteric lymph nodes was examined following oral administration to mice. Compared to the data observed previously for MPA prodrugs conjugated via the carboxylic acid, the new phenol-conjugated prodrugs showed clearly different profiles in terms of the linker chemistry. Prodrugs with shorter chain alkyl spacers (e.g., C4 and C6) supported minimal lymphatic transport (<3% of the dose recovered in lymph). When the chain lengths were longer (≥C10), the prodrugs demonstrated much higher potential for lymphatic transport (up to approximately 55% of dose). Although effectively promoting lymphatic transport, TG mimetic prodrugs with alkyl chain linkers did not necessarily result in marked increases in the exposure of MPA in the mesenteric lymph nodes in mice. Subsequently a number of self-immolative linkers conjugated via the phenol were explored to promote MPA liberation from the prodrugs, and these constructs demonstrated enhanced lymph node exposure. This study provides further insight into structure-lymphatic transport relationships for lymph-directing lipid mimetic prodrugs.

Polymeric Microspheres with High Mass Fraction of Therapeutics Enabled by the Manipulation of Kinetics Factor During Emulsion Droplet Solidification

High drug‐loaded polymeric microspheres hold promise in biomedical fields due to reduced excipient administration, minimized side effects, and enhanced therapeutical efficacy. Although thermodynamic factors like drug‐carrier material compatibility are well‐known to influence the drug loading capacity of microspheres, they fail to explain the huge difference in drug loading degree observed for polymers and drugs with similar interactions. Here, based on the droplet microfluidic platform, the single droplet solidification process is investigated. The results indicated that amorphous polymers can hinder drug diffusion during droplet solidification compared to crystalline polymers, resulting in a higher drug loading degree. Next, this principle is applied to improve the drug loading capability of crystalline polymers (polycaprolactone (PCL) and poly(L‐lactide) (PLLA)) by random co‐polymerization (poly(caprolactone‐co‐L‐lactide) (PCL‐PLLA)), achieving 6.2–22.2 times increased drug loading degree. Moreover, PCL‐PLLA microspheres with a high content of indomethacin exhibited superior therapeutical efficacy in the treatment of gout arthritis. Overall, these results offer insights into the impact of polymer crystallization on droplet solidification kinetics, which consequently affects the drug loading capacity. These findings provide guidelines for the development of polymers for efficient drug encapsulation.

Design and Syntheses of Proherbicides Targeting 4-Hydroxyphenylpyruvate Dioxygenase

4-Hydroxyphenylpyruvate dioxygenase (HPPD, EC 1.13.11.27) is regarded as a crucial target in the domain of herbicide discovery. Herein, we adopted the proherbicides concept, based on the initially discovered lead compound II-aa. Our group has designed four derivatives by incorporating alkyl, carbonyl ester, sulfonyl ester, and phosphate ester fragments. Although these derivatives did not exhibit very strong inhibitory activity against HPPD in vitro, and in vivo studies demonstrated their efficacy in suppressing HPPD activity. This was demonstrated by a reduction in HPPD protein levels and the emergence of significant bleaching symptoms in treated plants. Among these derivatives, the acetyl (III-ag), cyclopropyl carbonyl (III-ak), and pyridine-sulfonyl (III-bm) substituted derivatives demonstrated herbicidal activity that surpassed that of II-aa, exhibiting complete control over nine weed species at a concentration of 120 g of active ingredient per hectare (g ai/ha). It is worth noting that a dose of 30 g ai/ha was sufficient to achieve complete control of seven weed species. It is worth noting that one compound, III-ay (diethylamino carbonyl), exhibited selective inhibition of the growth of six weed species by over 90% at 30 g ai/ha while demonstrating no adverse effects on the normal growth of crops such as corn, wheat, and peanuts. A structure-activity relationship study demonstrated that carbonyl ester derivatives exhibited reduced herbicidal activity relative to their sulfonyl ester counterparts yet demonstrated enhanced crop tolerance. The results of our research indicate that the proherbicide approach has the potential to significantly enhance the efficacy and selectivity of herbicides. This strategy is poised to play a pivotal role in the advancement of next-generation herbicides.

Dissolving microneedles: A transdermal drug delivery system for the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disorder that impacts around 1% of the global population. Up to 20% of people become disabled within a year, which has a severely negative impact on their health and quality of life. RA has a complicated pathogenic mechanism, which initially affects small joints and progresses to larger ones over time. It can damage the skin, eyes, heart, kidney, and lung. Oral medications, intra-articular injections, and other treatments are being used; nevertheless, they have drawbacks, including low bioavailability, numerous adverse effects, and poor patient compliance. Dissolving microneedles (DMNs) are a safe and painless method for transdermal drug delivery, achieved through their ability to physically penetrate the epidermal barrier. They enable targeted drug delivery, significantly enhancing the bioavailability of medications and improving patient compliance. DMNs are particularly effective in delivering both lipophilic and high molecular weight biomolecules. The superior bioavailability of DMNs is demonstrated by the fact that low-dose DMN administration can achieve up to 25.8 times higher bioavailability compared to oral administration. This paper provides a comprehensive review of recent advancements in the use of DMNs for RA treatment, encompassing various materials (such as hyaluronic acid, chitosan, etc.), fabrication techniques (such as the two-step casting method, photopolymerization), and performance evaluations (including morphology, mechanical properties, skin penetration capability, solubility, and pharmacodynamics). Additionally, a thorough safety assessment has been conducted, revealing that DMNs cause minimal skin irritation and exhibit low cytotoxicity, ensuring their safety for clinical application. DMNs provide a highly effective and promising alternative to oral and injectable drug delivery systems, offering a novel therapeutic approach for RA patients that significantly improves treatment outcomes and enhances their quality of life.

Green Tea: Current Knowledge and Issues

Green tea possesses antioxidant, anti-inflammatory, anticancer, and antimicrobial activities, reduces body weight, and slows down aging. These effects are primarily attributed to catechins contained in green tea leaves, particularly epigallocatechin-3-gallate. However, in humans, the realization of green tea's beneficial effects is limited. In order to summarize and critically analyze the available scientific information about green tea's health benefits and issues related to its use, we conducted an in-depth literature review in scientific databases. A number of in vitro studies reported that green tea catechins modulate various signaling pathways in cells, which is thought to underlie their beneficial effects. However, data on the effects of catechins in humans are scarce, which is partly due to their low stability and oral bioavailability. Furthermore, catechins may also participate in pharmacokinetic interactions when co-administered with certain drugs such as anticancer agents, drugs for cardiovascular diseases, immunosuppressors, etc. As a result, adverse drug reactions or therapy failure may occur. In conclusion, over the years, various approaches have been investigated to optimize catechin intake and to achieve beneficial effects in humans, but to date, the use of catechins for prophylaxis or disease treatment remains limited. Therefore, future studies regarding the possibilities of catechins administration are needed.

Synthesis of Enantiostructured Triacylglycerol Prodrugs Constituting an Active Drug Located at Terminal sn-1 and sn-3 Positions of the Glycerol Backbone

The current paper reports the asymmetric synthesis of a focused library of enantiostructured triacylglycerols (TAGs) constituting a potent drug of the NSAID type (ibuprofen or naproxen) along with a pure bioactive n-3 polyunsaturated fatty acid (PUFA) intended as a novel type of prodrug. In this second category, a TAG prodrug of the terminal sn-1 or sn-3 position of the glycerol skeleton is acylated with a single saturated medium-chain fatty acid (C6, C8, C10, or C12), and another with the drug entity; the PUFA (EPA or DHA) is located in the sn-2 position. This was accomplished by a six-step chemoenzymatic approach, two of which were promoted by a lipase, starting from enantiopure (R)- and (S)-solketals. The highly regioselective immobilized Candida antarctica lipase (CAL-B) played a crucial role in the regiocontrol of the synthesis. The most challenging key step involved the incorporation of the drugs that were activated as oxime esters by the lipase exclusively in the terminal position of glycerol that is protected as a benzyl ether. All combinations, a total of 32 such prodrug TAGs, were prepared, isolated, and fully characterized, along with 24 acylglycerol intermediates, obtained in very-high-to-excellent yields in the majority of cases.

An oral tricyclic STING agonist suppresses tumor growth through remodeling of the immune microenvironment

Stimulator of interferon genes (STING) agonists could overcome immunosuppressive microenvironment to improve cancer immunotherapy. However, it is challenging to develop oral STING agonists to achieve systemic immunity. In this study, we discovered ZSA-51 as a potent oral STING agonist with distinct benzo[4,5]thieno[2,3-c]pyrrole-1,3-dione scaffold through tricyclic scaffold screening. ZSA-51, as a prodrug, exhibited nanomolar in vitro STING activation activity and potent in vivo antitumor efficacy in both colon and pancreatic cancer models. The specificity of ZSA-51 in activating STING was confirmed using STING knockout cells and a structurally similar but negative control compound. Moreover, ZSA-51 demonstrated superior oral pharmacokinetic (PK) properties with low toxicity. Importantly, ZSA-51 remodeled immune microenvironment both in tumor and lymph node. Our data suggest that ZSA-51 is a potent oral STING agonist with robust anticancer efficacy, superior PK properties, and low toxicity, holding potential for future development for cancer immunotherapy.

Carbon Monoxide and Alkoxycarbonyl Radical Enabled Migration Strategy for the Carbonylative Functionalization of Unactivated Alkenes

Herein we report a "carbonylative migration" strategy for the acylation-esterification type double functionalization of unactivated alkenes using alkyloxalkyl chlorides and CO as the reagents. The transformation is proceeded by the alkoxycarbonyl radical addition to unactivated alkenes, followed by the insertion of carbon monoxide to induce intramolecular migration of heteroaryl groups, which is different from the traditional reaction modes. The reaction conditions were mild and well tolerated with varieties of functional groups. A variety of 1,4-dicarbonyl compounds with different ester groups were produced easily which has high potential applications in biology, medicine, and other fields.

Prodrugging fungicidal amphotericin B significantly decreases its toxic effects

Amphotericin B (AmB) is one of the most effective antifungal drugs, with a strong, dose-dependent activity against most Candida and Aspergillus species responsible for life-threatening infections. However, AmB is severely toxic, which hinders its broad use. In this proof-of-concept study, we demonstrate that prodrugging AmB considerably decreases AmB toxicity without affecting its fungicidal activity. For this purpose, we modified the AmB structure by attaching a designer phosphate promoiety, thereby switching off its mode of action and preventing its toxic effects. The original fungicidal activity of AmB was then restored upon prodrug activation by host plasma enzymes. These AmB prodrugs showed a safer toxicity profile than commercial AmB deoxycholate in Candida and Aspergillus species and significantly prolonged larval survival of infected Galleria mellonella larvae. Based on these findings, prodrugging toxic antifungals may be a viable strategy for broadening the antifungal arsenal, opening up opportunities for targeted prodrug design.

Current Trends in Clinical Trials of Prodrugs

The development of new drugs is a lengthy and complex process regarding its conception and ideation, passing through in silico studies, synthesis, in vivo studies, clinical trials, approval, and commercialization, with an exceptionally low success rate. The lack of efficacy, safety, and suboptimal pharmacokinetic parameters are commonly identified as significant challenges in the discovery of new drugs. To help address these challenges, various approaches have been explored in medicinal chemistry, including the use of prodrug strategies. As a well-established approach, prodrug design remains the best option for improving physicochemical properties, reducing toxicity, and increasing selectivity, all while minimizing costs and saving on biological studies. This review article aims to analyze the current advances using the prodrug approach that has allowed the advance of drug candidates to clinical trials in the last 10 years. The approaches presented here aim to inspire further molecular optimization processes and highlight the potential of this strategy to facilitate the advancement of new compounds to clinical study phases.

Nanoparticle-enabled In Situ drug potency activation for enhanced tumor-specific therapy

Cancer treatment faces significant challenges including inadequate tumor specificity, drug resistance, and severe side effects, often resulting in unsatisfactory patient outcomes. Nanomedicines offer a transformative platform for tumor-targeted drug delivery and antitumor potency activation, providing an indispensable strategy for overcoming the severe damage to normal tissues caused by the inherent "always-on" cytotoxicity of conventional therapeutic agents. This review focuses on the emerging concept of "nanoparticle-enabled in situ drug potency activation", where inactive or minimally toxic agents are selectively activated within tumors to enhance the therapeutic efficacy and minimize the adverse effects. We systematically analyzed literature from PubMed and Web of Science databases spanning the last two decades, emphasizing experimental evidence supporting this in situ drug potency activation concept. Key strategies including stimuli-responsive prodrug nanoparticles, metal-induced activation, and bioorthogonal reactions are critically evaluated for their potential to overcome limitations in current cancer therapies. The findings highlight the potential of in situ potency activation as a promising alternative to conventional therapeutics, with far-reaching implications for advancing effective and safe cancer treatments.

Development and preclinical testing of a naloxone prodrug depot for extended protection against opioid overdose

The opioid crisis, driven by synthetic opioids like fentanyl, demands innovative solutions. The opioid antidote naloxone has a short action ( ~ 1 hour), requiring repeated doses. To address this, we present a new and simple naloxone prodrug delivery system repurposing a hydrophilic derivative of acoramidis, a potent transthyretin ligand. When the fully soluble prodrug solution is administered subcutaneously, the prodrug forms a zwitterionic depot at physiological pH, enabling extended naloxone release. This non-polymeric depot-forming approach is rare and employs carboxylesterase 2 for selective bioactivation, ensuring controlled drug release. In male rats and cynomolgus monkeys, a single subcutaneous dose provides steady naloxone release over several days, reducing blood-brain barrier diffusion, withdrawal symptoms, and CNS toxicity. Preclinical studies demonstrated efficacy in rat overdose models and achieved monkey naloxone levels matching effective human therapeutic levels. Although monkey efficacy was not assessed, combined rat efficacy and monkey pharmacokinetics suggest strong potential for successful human translation.

Recent advances in nanotechnology for Parkinson's disease: diagnosis, treatment, and future perspectives

Parkinson's disease is a progressive neurodegenerative disease that destroys substantia nigra dopaminergic neurons, causing tremors, bradykinesia, rigidity, and postural instability. Current treatment approaches primarily focus on symptom management, employing pharmacological, non-pharmacological, and surgical methods. However, these treatments often result in fluctuating symptoms, side effects, and disease progression. Here, the authors have reviewed the emerging field of nanomedicine as a promising path for Parkinson's disease treatment, emphasizing its potential to overcome the limitations of traditional therapies. Nanomedicine utilizes nanoparticles for targeted drug delivery, leveraging their small size and high surface area to volume ratio to cross the blood-brain barrier and deliver therapeutic agents directly to affected brain regions. Various nanoparticles, including lipid-based, polymeric, metallic, and carbon-based, have shown potential in Parkinson's disease treatment. Additionally, nanocarrier systems like liposomes, nanogels, dendrimers, and solid lipid nanoparticles offer controlled and sustained release of therapeutic agents, enhancing their bioavailability and reducing side effects. This review provides insights into the pathophysiology of Parkinson's disease, highlighting the mechanisms of neurodegeneration, the role of alpha-synuclein, and the disruption of dopaminergic pathways. It further discusses the application of gene therapy in conjunction with nanomedicine for targeted therapeutic interventions.

Resveratrol-A Promising Therapeutic Agent with Problematic Properties

Resveratrol is a natural polyphenol (stilbenoid), which can be found in grape skin, red wine, blueberries, peanuts and others. The biological properties of resveratrol, in particular antioxidant, anti-inflammatory, anticancer, estrogenic, vasorelaxant and cardioprotective activity, are the main reason for its importance in medicine and pharmacy. Despite all of its advantages, however, there are many problems related to this polyphenolic substance, such as low stability, water insolubility, poor bioavailability and fast metabolism. For this reason, scientists are currently searching for different approaches to dealing with these problematic properties and improving the therapeutic usage of resveratrol. This review summarizes the mechanisms of the biological effects of resveratrol, determined in vitro and in vivo, and the main limitations of the drug. The article emphasizes new approaches for the improvement of resveratrol delivery, in particular nanoencapsulation, formation of nanocrystals, prodrugs and structure analogues.

Integrated phase I pharmacokinetics and pharmacodynamics of epinephrine administered through sublingual film, autoinjector, or manual injection

BACKGROUND

Epinephrine is the first-line treatment for anaphylaxis and is administered through intramuscular or subcutaneous injection. AQST-109, a sublingual film containing the prodrug epinephrine, was developed as an alternative delivery method for treating severe allergic reactions, including anaphylaxis.

OBJECTIVE

To compare the pharmacokinetics (PK) and pharmacodynamics (PD) of epinephrine after the administration of AQST-109 with those of epinephrine delivered by manual intramuscular injection and epinephrine autoinjectors.

METHODS

Data were integrated from 2 randomized, open-label, phase I crossover trials that evaluated the PK and PD of epinephrine in 54 healthy volunteers. They had no previous medical conditions and were delivered either AQST-109 12 mg or 0.3 mg EpiPen, 0.3 mg generic EpiPen, 0.3 mg Auvi-Q, and 0.3 mg manual intramuscular injection.

RESULTS

AQST-109 yielded comparable epinephrine PK and exposure to both manual intramuscular injections and epinephrine autoinjectors. The median time to maximum concentration (Tmax) for AQST-109 was 15 minutes, compared with EpiPen (10 minutes), generic EpiPen (15 minutes), Auvi-Q (30 minutes), and manual intramuscular injection (50 minutes). There was also an early, rapid, and consistent increase in systolic blood pressure, diastolic blood pressure, and heart rate after the administration of AQST-109.

CONCLUSION

AQST-109 delivered epinephrine with PK and PD results within the bracketed range of approved intramuscular products. AQST-109 has promise as an innovative, needle-free, nondevice, portable, and orally delivered alternative for first-line treatment of type I allergic reactions, including anaphylaxis.

Molecular Matchmakers: Bioconjugation Techniques Enhance Prodrug Potency for Immunotherapy

Cancer patients suffer greatly from the severe off-target side effects of small molecule drugs, chemotherapy, and radiotherapy─therapies that offer little protection following remission. Engineered immunotherapies─including cytokines, immune checkpoint blockade, monoclonal antibodies, and CAR-T cells─provide better targeting and future tumor growth prevention. Still, issues such as ineffective activation, immunogenicity, and off-target effects remain primary concerns. "Prodrug" therapies─classified as therapies administered as inactive and then selectively activated to control the time and area of release─hold significant promise in overcoming these concerns. Bioconjugation techniques (e.g., natural linker conjugation, bioorthogonal reactions, and noncanonical amino acid incorporation) enable the rapid and homogeneous synthesis of prodrugs and offer selective loading of immunotherapeutic agents to carrier molecules and protecting groups to prevent off-target effects after administration. Several prodrug activation mechanisms have been highlighted for cancer therapeutics, including endogenous activation by hypoxic or acidic conditions common in tumors, exogenous activation by targeted bioorthogonal cleavage, or stimuli-responsive light activation, and dual-stimuli activation, which adds specificity by combining these mechanisms. This review will explore modern prodrug conjugation and activation options, focusing on how these strategies can enhance immunotherapy responses and improve patient outcomes. We will also discuss the implications of computational methodology for therapy design and recommend procedures to determine how and where to conjugate carrier systems and "prodrug" groups onto therapeutic agents to enhance the safety and control of these delivery platforms.

Improving oral absorption of a rapidly crystallizing parent drug using prodrug strategy: Comparison of phosphate versus glycine based prodrugs

With an increasing number of Biopharmaceutical Classification System (BCS) II/IV pipeline compounds, solubilizing and supersaturating formulation strategies are becoming prevalent. Beyond formulation and solid form strategies, prodrugs are also employed to overcome solubility-limited absorption of poorly water-soluble compounds. Prodrugs can potentially yield supersaturated systems upon conversion to the parent drug intraluminally and thus enhance absorption. However, supersaturation also increases the driving force for crystallization, resulting in low solution concentrations, which can potentially negate the advantage of prodrugs. In this work, two unique solubility-enhancing prodrugs, phosphate and glycine esters, were investigated for a rapidly crystallizing parent drug. Ex vivo absorption studies using rat tissue and in vivo studies in dogs were performed. Conversion rate of the phosphate prodrug to the parent was dependent on the milieu and increased ∼24-fold in the presence of intestinal contents as medium and tissue relative to neat buffer. In contrast, conversion of the glycine prodrug was minimal under any conditions tested, suggesting that the conversion occurs after absorption into the enterocytes. Phosphate prodrug showed a non-linear increase in parent drug absorptive flux across rat intestinal tissue with concentration when intestinal contents were used as donor media. This was attributed to rapid conversion and high supersaturation of the parent drug which subsequently resulted in crystallization at high doses in the donor chamber. Glycine prodrug did not undergo complete conversion at high doses and was absorbed unchanged on the basolateral side, indicating saturation of the converting enzymes in the enterocytes. The combined flux (parent drug and glycine) showed a linear increase with dose and crystallization was not observed. Under physiological conditions, glycine prodrug that is absorbed unchanged from the intestine can potentially undergo complete conversion in hepatocytes after absorption and make the parent drug systemically available. Thus, glycine prodrug provided overall higher absorption compared to phosphate prodrug. The observed flux levels for both the prodrugs were higher compared to the parent drug alone, highlighting an advantage to use of a prodrug strategy to improve absorption of such compounds. Oral dosing in a dog PK study revealed that the bioavailability using the phosphate prodrug was ∼50% whereas, it was ∼100% with glycine prodrug, supporting the in vitro observations.

Advances in colon-targeted drug technologies

PURPOSE OF REVIEW

Herein, we present an overview of innovative oral technologies utilized in colonic drug delivery systems that have made significant translational and clinical advancements to treat inflammatory bowel disease (IBD) in recent years.

RECENT FINDINGS

The colon is home to distinct physiological conditions, such as pH and microbiota, that have been exploited in the development of colonic drug delivery systems for the treatment of local and systemic diseases. However, given the intra and interindividual variability in the gastrointestinal tract of both healthy and diseased states, various systems have shown inconsistencies in targeted drug release to the colon. Recent breakthroughs have led to systems that incorporate multiple independent trigger mechanisms, ensuring drug release even if one mechanism fails due to physiological variability. Such advanced platforms have bolstered the development of oral biologics delivery, an especially promising direction given the lack of commercially available oral antibody medications for IBD. These concepts can be further enhanced by employing 3D printing which enables the personalisation of medicines.

SUMMARY

Leveraging these novel technologies can accurately deliver therapeutics to the colon, allowing for treatments beyond gastrointestinal tract diseases. To realize the full potential of colonic drug delivery, it is paramount that research focuses on the clinical translatability and scalability of novel concepts.

Therapeutic advantage of combinatorial chimeric antigen receptor T cell and chemotherapies

Chimeric antigen receptor (CAR) T cell therapies have transformed outcomes for many patients with hematological malignancies. However, some patients do not respond to CAR T cell treatment, and adapting CAR T cells for treatment of solid and brain tumors has been met with many challenges, including a hostile tumor microenvironment and poor CAR T cell persistence. Thus, it is unlikely that CAR T cell therapy alone will be sufficient for consistent, complete tumor clearance across patients with cancer. Combinatorial therapies of CAR T cells and chemotherapeutics are a promising approach for overcoming this because chemotherapeutics could augment CAR T cells for improved antitumor activity or work in tandem with CAR T cells to clear tumors. Herein, we review efforts toward achieving successful CAR T cell and chemical drug combination therapies. We focus on combination therapies with approved chemotherapeutics because these will be more easily translated to the clinic but also review nonapproved chemotherapeutics and drug screens designed to reveal promising new CAR T cell and chemical drug combinations. Overall, this review highlights the promise of CAR T cell and chemotherapy combinations with a specific focus on how combinatorial therapy overcomes challenges faced by either monotherapy and supports the potential of this therapeutic strategy to improve outcomes for patients with cancer. SIGNIFICANCE STATEMENT: Improving currently available CAR T cell products via combinatorial therapy with chemotherapeutics has the potential to drastically expand the types of cancers and number of patients that could benefit from these therapies when neither alone has been sufficient to achieve tumor clearance. Herein, we provide a thorough review of the current efforts toward studying CAR T and chemotherapy combinatorial therapies and offer perspectives on optimal ways to identify new and effective combinations moving forward.

Near-Infrared Activatable Copper Nanoplatforms Synergize with the 5-Azacytidine Prodrug to Potentiate Cuproptosis

Cuproptosis, a newly discovered cell death modality, is gaining recognition for its crucial role in antitumor therapy. Here, we demonstrated that Ferredoxin 1 (FDX1), a key gene involved in cuproptosis, is negatively correlated with malignancy and T-cell exhaustion in head and neck squamous cell carcinoma (HNSCC). Based on these findings, we developed near-infrared (NIR) light-controlled nanoparticles (NPs), CuD@PM, which can selectively deliver copper to HNSCC cells and induce cuproptosis in the presence of microneedles loaded with triacetylated azacitidine (TAc-AzaC) and 808 nm laser irradiation. Intravenous administration of these NPs significantly suppressed tumor growth in HNSCC animal models and enhanced the antitumor immune response. The NIR-controlled activation of cuproptosis offers great potential as a safe, targeted, and image-guided antitumor therapy for HNSCC.

Drug Delivery Across the Blood-Brain Barrier: A New Strategy for the Treatment of Neurological Diseases

The blood-brain barrier (BBB) serves as a highly selective barrier between the blood and the central nervous system (CNS), and its main function is to protect the brain from foreign substances. This physiological property plays a crucial role in maintaining CNS homeostasis, but at the same time greatly limits the delivery of drug molecules to the CNS, thus posing a major challenge for the treatment of neurological diseases. Given that the high incidence and low cure rate of neurological diseases have become a global public health problem, the development of effective BBB penetration technologies is important for enhancing the efficiency of CNS drug delivery, reducing systemic toxicity, and improving the therapeutic outcomes of neurological diseases. This review describes the physiological and pathological properties of the BBB, as well as the current challenges of trans-BBB drug delivery, detailing the structural basis of the BBB and its role in CNS protection. Secondly, this paper reviews the drug delivery strategies for the BBB in recent years, including physical, biological and chemical approaches, as well as nanoparticle-based delivery technologies, and provides a comprehensive assessment of the effectiveness, advantages and limitations of these delivery strategies. It is hoped that the review in this paper will provide valuable references and inspiration for future researchers in therapeutic studies of neurological diseases.

Cell-Permeable Nicotinamide Adenine Dinucleotides for Exploration of Cellular Protein ADP-Ribosylation

Posttranslational modifications (PTMs) greatly enhance the functional diversity of proteins, surpassing the number of gene-encoded variations. One intriguing PTM is ADP-ribosylation, which utilizes nicotinamide adenine dinucleotide (NAD+) as a substrate and is essential in cell signaling pathways regulating cellular responses. Here, we report the first cell-permeable NAD+ analogs and demonstrate their utility for investigating cellular ADP-ribosylation. Using a desthiobiotin-labelled analog for affinity enrichment of proteins that are ADP-ribosylated in living cells under oxidative stress, we identified protein targets associated with host-virus interactions, DNA damage and repair, protein biosynthesis, and ribosome biogenesis. Most of these targets have been noted in various literature sources, highlighting the potential of our probes for cellular ADP-ribosylome studies.

Applying molecular hybridization to design a new class of pyrazolo[3,4-d]pyrimidines as Src inhibitors active in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common type of liver solid tumor and the second leading cause of cancer-related deaths worldwide. Although new treatment options have been recently approved, the development of tumor resistance and the poor prognosis for advanced HCC make the current standard of care unsatisfying. In this scenario, the non-receptor tyrosine kinase (TK) c-Src emerged as a promising target for developing new anti-HCC agents. Our group reported a large library of pyrazolo[3,4-d]pyrimidines active as potent c-Src inhibitors. Starting from these data, we applied a molecular hybridization approach to combine the in-house pyrazolo[3,4-d]pyrimidine SI192 with the approved TK inhibitor (TKI) dasatinib, with the aim of identifying a new generation of Src inhibitors. Enzymatic results prompted us to design second-generation compounds with a better binding profile based on a hit optimization protocol comprised of molecular modeling and on-paper rational design. This investigation led to the identification of a few nanomolar Src inhibitors active toward two HCC cell lines (HepG2 and HUH-7) selected according to their high and low c-Src expression, respectively. In particular, 7e showed an IC50 value of 0.7 nM toward Src and a relevant antiproliferative efficacy on HepG2 cells after 72h (IC50 = 2.47 μM). Furthermore, 7e exhibited a cytotoxic profile better than dasatinib. The ADME profile suggested that 7e deserves further investigation as a promising TKI in cancer therapies. Finally, 7e's ability to inhibit HepG2 cell proliferation, elicit an irreversible cytotoxic effect, arrest cellular migration, and induce apoptotic-mediated cell death was assessed.

Positron Emission Tomography Imaging of Cathepsin B in Tumors with Activable Small Molecule Tracers

Cathepsin B (CTB) is overexpressed in several types of tumors, and precise evaluation of the CTB activity can offer a promising method for the early diagnosis of tumors. In this study, two CTB-activated positron emission tomography (PET) tracers, [68Ga]NOTA-SFCVM and [68Ga]NOTA-SFCVHEM, were developed for sensitive and specific detection of CTB. Both tracers undergo a click condensation between 2-cyano-6-aminobenzothiazole (CBT) and cysteine (Cys) to form a cyclization product, thereby enhancing and prolonging the PET signal in tumors. In vitro cellular experiments showed that the tracers could differentiate tumor cells with different expression levels of CTB. In vivo PET imaging further revealed that the tracers selectively accumulated in the CTB-positive tumors. Compared with [68Ga]NOTA-SFCVM, [68Ga]NOTA-SFCVHEM containing a morpholine group and a histidine-glutamate-histidine-glutamate-histidine-glutamate sequence exhibited faster catalytic efficiency toward CTB, higher tumor uptake, and reduced liver uptake. These findings suggest that [68Ga]NOTA-SFCVHEM holds potential for clinical use in the early diagnosis of CTB-related tumors.

Synthesis of Enantiostructured Triacylglycerols Possessing a Saturated Fatty Acid, a Polyunsaturated Fatty Acid and an Active Drug Intended as Novel Prodrugs

This report describes the asymmetric synthesis of a focused library of enantiopure structured triacylglycerols (TAGs) comprised of a single saturated fatty acid (C6, C8, C10, C12, C14 or C16), a pure bioactive n-3 polyunsaturated fatty acid (EPA or DHA) and a potent drug (ibuprofen or naproxen) intended as a novel type of prodrug. One of the terminal sn-1 or sn-3 positions of the glycerol backbone is occupied with a saturated fatty, the remaining one with a PUFA, and the drug entity is present in the sn-2 position. This was accomplished by a six-step chemoenzymatic approach starting from enantiopure (R)- and (S)-solketals. The highly regioselective immobilized Candida antarctica lipase (CAL-B) played a crucial role in the regiocontrol of the synthesis. All combinations, a total of 48 such prodrug TAGs, were prepared, isolated and fully characterized, along with 60 acylglycerol intermediates, obtained in very high to excellent yields.

Innovative medicinal chemistry strategies for enhancing drug solubility

Drug candidates with poor solubility have been recognized as the cause of many drug development failures, owing to the fact that low solubility is unfavorable for physicochemical, pharmacokinetic (PK) and pharmacodynamic (PD) properties. Given the imperative role of solubility during drug development, we herein summarize various strategies for solubility optimizations from a medicinal chemistry perspective, including introduction of polar group, salt formation, structural simplification, disruption of molecular planarity and symmetry, optimizations on the solvent exposed region as well as prodrug design. In addition, methods for solubility assessment and prediction are reviewed. Besides, we have deeply discussed the strategies for solubility improvement. This paper is expected to be beneficial for the development of drug-like molecules with good solubility.

Recent advances in targeted drug delivery systems for multiple myeloma

Despite significant therapeutic advances, multiple myeloma (MM) remains a challenging, incurable, hematological malignancy. The efficacy of traditional chemotherapy and currently available anti-MM agents is in part limited by their adverse effects, which restrict their therapeutic potential. Nanotherapeutics is an emerging field of cancer therapy that can overcome the biological and chemical barriers of existing anticancer drugs. This review presents an overview of recent advancements in nanoparticle- and immunotherapy-based drug delivery systems for MM treatment. It further delves into the targeting strategies, mechanism of controlled drug release, and challenges associated with the development of drug delivery systems for the treatment of MM.

Bioorthogonal Janus microparticles for photothermal and chemo-therapy

Bioorthogonal chemistry, recognized as a highly efficient tool in chemical biology, has shown significant value in cancer treatment. The primary objective is to develop efficient delivery strategies to achieve enhanced bioorthogonal drug treatment for tumors. Here, Janus microparticles (JMs) loaded with cyclooctene-modified doxorubicin prodrug (TCO-DOX) and tetrazine-modified indocyanine green (Tz-ICG) triggers are reported. Besides activating TCO-DOX, Tz-ICG is also a photothermal agent used in photothermal therapy (PTT), enabling the simultaneous use of biorthogonal chemotherapy and PTT. Additionally, the DOX could be significantly reduced in systemic toxicity with the modification of cyclooctene. Thus, the developed drug-carrying JMs system exhibits effective tumor cell killing in vitro and effectively inhibits tumor local progress and distant lung metastasis after postoperative treatment with good safety. These results demonstrate that the prepared JMs provide a paradigm for bioorthogonal prodrug activation and localized delivery, and hold great promise for cancer therapy as well as other related applications.

Nanotechnology in Drug Delivery: Anatomy and Molecular Insight into the Self-Assembly of Peptide-Based Hydrogels

The bioavailability, release, and stability of pharmaceuticals under physicochemical conditions is the major cause of drug candidates failing during their clinical trials. Therefore, extensive efforts have been invested in the development of novel drug delivery systems that are able to transport drugs to a desired site and improve bioavailability. Hydrogels, and peptide hydrogels in particular, have been extensively investigated due to their excellent biocompatibility and biodegradability properties. However, peptide hydrogels often have weak mechanical strength, which limits their therapeutic efficacy. Therefore, a number of methods for improving their rheological properties have been established. This review will cover the broad area of drug delivery, focusing on the recent developments in this research field. We will discuss the variety of different types of nanocarrier drug delivery systems and then, more specifically, the significance and perspectives of peptide-based hydrogels. In particular, the interplay of intermolecular forces that govern the self-assembly of peptide hydrogels, progress made in understanding the distinct morphologies of hydrogels, and applications of non-canonical amino acids in hydrogel design will be discussed in more detail.

The fall of the mycobacterial cell wall: interrogating peptidoglycan synthesis for novel anti-TB agents

Tuberculosis (TB) caused by Mycobacterium tuberculosis has been a threat to human health for thousands of years and still leads to millions of deaths each year. TB is a disease that is refractory to treatment, partially due to its capacity for in-host persistence. The cell wall of mycobacteria, rich in mycolic acid, is broadly associated with bacterial persistence together with antimicrobial and immunological resistance. Enzymes for the biosynthesis of bacterial peptidoglycan, an essential component of the cell wall, have been addressed and considered as appealing drug targets in pathogens. Significant effort has been dedicated to finding inhibitors that hinder peptidoglycan biosynthesis, many with demonstrated enzymatic inhibition in vitro being published. One family of critical biosynthetic enzymes are the Mur enzymes, with many enzyme specific inhibitors having been reported. However, a lesser developed strategy which may have positive clinical implications is to take advantage of the common structural and catalytic characteristics among Mur enzymes and to allow simultaneous, multiple Mur inhibition, and avert the development of drug resistance. M. tuberculosis relies on these essential Mur enzymes, with the best-known subset being Mur ligases, but also utilizes unique functions of atypical transpeptidases resulting in peptidoglycan peptide cross-linking beneficial to the bacteria's capacity for chronic persistence in humans. A systematic review is now needed, with an emphasis on M. tuberculosis. The urgent development of novel anti-TB agents to counter rapidly developing drug resistance requires a revisit of the literature, past successes and failures, in an attempt to reveal liabilities in critical cellular functions and drive innovation.

De novo GTP synthesis is a metabolic vulnerability for the interception of brain metastases

Patients with brain metastases (BM) face a 90% mortality rate within one year of diagnosis and the current standard of care is palliative. Targeting BM-initiating cells (BMICs) is a feasible strategy to treat BM, but druggable targets are limited. Here, we apply Connectivity Map analysis to lung-, breast-, and melanoma-pre-metastatic BMIC gene expression signatures and identify inosine monophosphate dehydrogenase (IMPDH), the rate-limiting enzyme in the de novo GTP synthesis pathway, as a target for BM. We show that pharmacological and genetic perturbation of IMPDH attenuates BMIC proliferation in vitro and the formation of BM in vivo. Metabolomic analyses and CRISPR knockout studies confirm that de novo GTP synthesis is a potent metabolic vulnerability in BM. Overall, our work employs a phenotype-guided therapeutic strategy to uncover IMPDH as a relevant target for attenuating BM outgrowth, which may provide an alternative treatment strategy for patients who are otherwise limited to palliation.

Fluorescent probes for investigating the internalisation and action of bioorthogonal ruthenium catalysts within Gram-positive bacteria

Bioorthogonal reactions are extremely useful for the chemical modification of biomolecules, and are already well studied in mammalian cells. In contrast, very little attention has been given to the feasibility of such reactions in bacteria. Herein we report modified coumarin dyes for monitoring the internalisation and activity of bioorthogonal catalysts in the Gram-positive bacterial species Bacillus subtilis. Two fluorophores based on 7-aminocoumarin were synthesised and characterised to establish their luminescence properties. The introduction of an allyl carbamate (R2N-COOR') group onto the nitrogen atom of two 7-aminocoumarin derivatives with different solubility led to decreased fluorescence emission intensities and remarkable blue-shifts of the emission maxima. Importantly, this allyl carbamate group could be uncaged by the bioorthogonal, organometallic ruthenium catalyst investigated in this work, to yield the fluorescent product under biologically-relevant conditions. The internalisation of this catalyst was confirmed and quantified by ICP-OES analysis. Investigation of the bacterial cytoplasm and extracellular fractions separately, following incubation of the bacteria with the two caged dyes, facilitated their localisation, as well as that of their uncaged form by catalyst addition. In fact, significant differences were observed, as only the more lipophilic dye was located inside the cells and importantly remained there, seemingly avoiding efflux mechanisms. However, the uncaged form of this dye is not retained, and was found predominantly in the extracellular space. Finally, a range of siderophore-conjugated derivatives of the catalyst were investigated for the same transformations. Even though uptake was observed, albeit less significant than for the non-conjugated version, the fact that similar intracellular reaction rates were observed regardless of the iron content of the medium supports the notion that their uptake is independent of the iron transporters utilised by Gram-positive Bacillus subtilis cells.

Mammalian Esterase Activity: Implications for Peptide Prodrugs

As a traceless, bioreversible modification, the esterification of carboxyl groups in peptides and proteins has the potential to increase their clinical utility. An impediment is the lack of strategies to quantify esterase-catalyzed hydrolysis rates for esters in esterified biologics. We have developed a continuous Förster resonance energy transfer (FRET) assay for esterase activity based on a peptidic substrate and a protease, Glu-C, that cleaves a glutamyl peptide bond only if the glutamyl side chain is a free acid. Using pig liver esterase (PLE) and human carboxylesterases, we validated the assay with substrates containing simple esters (e.g., ethyl) and esters designed to be released by self-immolation upon quinone methide elimination. We found that simple esters were not cleaved by esterases, likely for steric reasons. To account for the relatively low rate of quinone methide elimination, we extended the mathematics of the traditional Michaelis-Menten model to conclude with a first-order intermediate decay step. By exploring two regimes of our substrate → intermediate → product (SIP) model, we evaluated the rate constants for the PLE-catalyzed cleavage of an ester on a glutamyl side chain (kcat/KM = 1.63 × 103 M-1 s-1) and subsequent spontaneous quinone methide elimination to regenerate the unmodified peptide (kI = 0.00325 s-1; t1/2 = 3.55 min). The detection of esterase activity was also feasible in the human intestinal S9 fraction. Our assay and SIP model increase the understanding of the release kinetics of esterified biologics and facilitate the rational design of efficacious peptide prodrugs.

Lactyllysine Esterification Enables Efficient Lactylprotein Expression via Genetic Code Expansion and Supports Functional Proteomics Studies

Lysine lactylation has recently been discovered and demonstrated to be an essential player in immunity, cancer and neurodegenerative diseases. Genetic code expansion (GCE) technique is powerful in uncovering lactylation functions, since it allows site-specific incorporation of lactyllysine (Klac) into proteins of interest (POIs) in living cells. However, the inefficient uptake of Klac into cells, due to its high hydrophilicity, results in limited expression of lactylated POIs. To address this challenge, here we designed esterified Klac derivatives, exemplified by ethylated Klac (KlacOEt), to enhance Klac's lipophilicity and improve its cellular uptake. The expression level of site-specifically lactylated POIs was doubled using KlacOEt in both Escherichia coli and HEK293T cells. Immunoprecipitation mass spectrometry analysis verified the significantly increased yield of the precisely lactylated fructose-bisphosphate aldolase A using KlacOEt. Furthermore, in conjunction with the Target Responsive Accessibility Profiling approach, we found that lactylation at ALDOA-K147 altered the protein's conformation, which may explain the lactylation-induced reduction in enzyme activity. Together, we demonstrate that, through enhancing the yield of lactylated proteins with Klac esters via GCE, we are able to site-specifically reveal the effects of lactylation on POIs' interactions, conformations and activities using a suite of functional proteomics and biochemical tools.

Synthetic Approaches, Properties, and Applications of Acylals in Preparative and Medicinal Chemistry

Diesters of geminal diols (R-CH(O-CO-R')2, RR'C(OCOR″)2, etc. with R = H, aryl or alkyl) are termed acylals according to IUPAC recommendations (Rule P-65.6.3.6 Acylals) if the acids involved are carboxylic acids. Similar condensation products can be obtained from various other acidic structures as well, but these related "non-classical acylals", as one might call them, differ in various aspects from classical acylals and will not be discussed in this article. Carboxylic acid diesters of geminal diols play a prominent role in organic chemistry, not only in their application as protective groups for aldehydes and ketones but also as precursors in the total synthesis of natural compounds and in a variety of organic reactions. What is more, acylals are useful as a key structural motif in clinically validated prodrug approaches. In this review, we summarise the syntheses and chemical properties of such classical acylals and show what potentially under-explored possibilities exist in the field of drug design, especially prodrugs, and classify this functional group in medicinal chemistry.

Locally unlocks prodrugs by radiopharmaceutical in tumor for cancer therapy

Chemotherapy is the first-line treatment for cancer, but its systemic toxicity can be severe. Tumor-selective prodrug activation offers promising opportunities to reduce systemic toxicity. Here, we present a strategy for activating prodrugs using radiopharmaceuticals. This strategy enables the targeted release of chemotherapeutic agents due to the high tumor-targeting capability of radiopharmaceuticals. [18F]FDG (2-[18F]-fluoro-2-deoxy-D-glucose), one of the most widely used radiopharmaceuticals in clinics, can trigger Pt(IV) complex for controlled release of axial ligands in tumors, it might be mediated by hydrated electrons generated by water radiolysis resulting from the decay of radionuclide 18F. Its application offers the controlled release of fluorogenic probes and prodrugs in living cells and tumor-bearing mice. Of note, an OxaliPt(IV) linker is designed to construct an [18F]FDG-activated antibody-drug conjugate (Pt-ADC). Sequential injection of Pt-ADC and [18F]FDG efficiently releases the toxin in the tumor and remarkably suppresses the tumor growth. Radiotherapy is booming as a perturbing tool for prodrug activation, and we find that [18F]FDG is capable of deprotecting various radiotherapy-removable protecting groups (RPGs). Our results suggest that tumor-selective radiopharmaceutical may function as a trigger, for developing innovative prodrug activation strategies with enhanced tumor selectivity.