Striking a Balance between Carbonate/Carbamate Linkage Bond- and Reduction-Sensitive Disulfide Bond-Bearing Linker for Tailored Controlled Release: In Situ Covalent-Albumin-Binding Gemcitabine Prodrugs Promote Bioavailability and Tumor Accumulation

Development of natural product-based targeted protein degraders as anticancer agents

Targeted protein degradation (TPD) has emerged as a powerful approach for eliminating cancer-causing proteins through an "event-driven" pharmacological mode. Proteolysis-targeting chimeras (PROTACs), molecular glues (MGs), and hydrophobic tagging (HyTing) have evolved into three major classes of TPD technologies. Natural products (NPs) are a primary source of anticancer drugs and have played important roles in the development of TPD technology. NPs potentially expand the toolbox of TPD by providing a variety of E3 ligase ligands, protein of interest (POI) warheads, and hydrophobic tags (HyTs). As a promising direction in the TPD field, NP-based degraders have shown great potential for anticancer therapy. In this review, we summarize recent advances in the development of NP-based degraders (PROTACs, MGs and HyTing) with anticancer applications. Moreover, we put forward the challenges while presenting potential opportunities for the advancement of future targeted protein degraders derived from NPs.

A Versatile Platform to Generate Prodrugs with Rapid and Precise Albumin Hitchhiking and High Cargo Loading for Tumor-Targeted Chemotherapy

Due to its tumor homing and long serum half-life, albumin is an ideal drug carrier for chemotherapy. For endogenous albumin hitchhiking with high cargo loading, a trimeric albumin-binding domain (ABD), i.e., ABD-Tri is designed by fusing an ABD with high specificity and affinity for albumin to a self-trimerizing domain (Tri) with an additional cysteine residue. ABD-Tri is highly (40 mg L-1 ) expressed as soluble and trimeric proteins in Escherichia coli (E. coli). Once mixed together, ABD-Tri rapidly and specifically forms a stable complex with albumin under physiological conditions without obviously changing its receptor- and cell-binding and tumor-homing properties. Maleimide-modified prodrugs are highly effectively conjugated to ABD-Tri to produce homogenous ABD-Tri-prodrugs with triple cargo loading under physiological conditions by thiol-maleimide click chemistry. Unlike the maleimide moiety, which can only mediate time- and concentration-dependent albumin binding, ABD-Tri mediated fast (within several minutes) albumin binding of drugs even at extremely low concentrations (µg mL-1 ). Compared to maleimide-modified prodrugs, ABD-Tri-prodrugs exhibit better tumor homing and greater in vivo antitumor effect, indicating that conjugation of chemical drug to ABD-Tri outperforms maleimide modification for endogenous albumin hitchhiking. The results demonstrate that ABD-Tri may serve as a novel platform to produce albumin-binding prodrugs with high cargo-loading capacity for tumor-targeted chemotherapy.

Self-Amplified Cascade Degradation and Oxidative Stress Via Rational pH Regulation of Oxidation-Responsive Poly(ferrocene) Aggregates

Precise activation of polymer nanoparticles at lesion sites is crucial to achieve favorable therapeutic efficacy. However, conventional endogenous stimuli-responsive polymer nanoparticles probably suffer from few triggers to stimulate the polymer degradation and subsequent functions. Here, we describe oxidation-responsive poly(ferrocene) amphiphiles containing phenylboronic acid ester and ferrocene as the repeating backbone units. Upon triggering by hydrogen peroxide inside the tumor cells, the phenylboronic acid ester bonds are broken and poly(ferrocene) units are degraded to afford free ferrocene and noticeable hydroxide ions. The released hydroxide ions can immediately improve the pH value within the poly(ferrocene) aggregates, and the degradation rate of the phenylboronic acid ester backbone is further promoted by the upregulated pH; thereupon, the accelerated degradation can release much more additional hydroxide ions to improve the pH, thus achieving a positive self-amplified cascade degradation of poly(ferrocene) aggregates accompanied by oxidative stress boosting and efficient cargo release. Specifically, the poly(ferrocene) aggregates can be degraded up to ∼90% within 12 h when triggered by H2O2, while ferrocene-free control nanoparticles are degraded by only 30% within 12 days. In addition, the maleimide moieties tethered in the hydrophilic corona can capture blood albumin to form an albumin-rich protein corona and significantly improve favorable tumor accumulation. The current oxidation-responsive poly(ferrocene) amphiphiles can efficiently inhibit tumors in vitro and in vivo. This work provides a proof-of-concept paradigm for self-amplified polymer degradation and concurrent oxidative stress, which is promising in actively regulated precision medicine.

Bioinspired Nanocomplexes Comprising Phenolic Acid Derivative and Human Serum Albumin for Cancer Therapy

Inspired by the natural phenomenon of phenolic-protein interactions, we translate this "naturally evolved interaction" to a "phenolic acid derivative based albumin bound" technology, through the synthesis of phenolic acid derivatives comprising a therapeutic cargo linked to a phenolic motif. Phenolic acid derivatives can bind to albumin and form nanocomplexes after microfluidic mixing. This strategy has been successfully applied to different types of anticancer drugs, including taxanes, anthraquinones, etoposides, and terpenoids. Paclitaxel was selected as a model drug for an in-depth study. Three novel paclitaxel-phenolic acid conjugates have been synthesized. Molecular dynamics simulations provide insights into the self-assembled mechanisms of phenolic-protein nanocomplexes. The nanocomplexes show improved pharmacokinetics, elevated tolerability, decreased neurotoxicity, and enhanced anticancer efficacies in multiple murine xenograft models of breast cancer, in comparison with two clinically approved formulations, Taxol (polyoxyethylated castor oil-formulated paclitaxel) and Abraxane (nab-paclitaxel). Such a robust system provides a broadly applicable platform for the development of albumin-based nanomedicines and has great potential for clinical translation.

Design, synthesis and antitumor activity study of a gemcitabine prodrug conjugated with a HDAC6 inhibitor

Gemcitabine, as a first-line antitumor drug, has attracted extensive attention. However the occurrence of drug resistance limits its clinical utilization. In this paper, a gemcitabine prodrug GZ was designed and synthesized by conjugation of gemcitabine with a newly reported HDAC6 selective inhibitor pentadecanoic acid. GZ displayed high cytotoxicity to nine cancer cell lines with IC₅₀ values in the low micromolar range. In vivo, GZ displayed superior antitumor activity to gemcitabine in a 4T1 tumor xenograft model without obvious pathological damage to important organs of mice. Our study showed that compound GZ is a potential gemcitabine prodrug, which is worthy of further antitumor activity exploration.

Novel 5-Fluorouracil Carbonate-Loaded Liposome: Preparation, In Vitro, and In Vivo Evaluation as an Antitumor Agent

5-Fluorouracil (5-FU) is a chemotherapeutic drug against many types of cancers, especially colorectal cancer. However, its short plasma half-life and serious adverse reactions limit its wide clinical applications. To overcome these shortcomings, a novel lipophilic 5-FU carbonate [XL-01, (5-fluoro-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl) methyl tetradecyl carbonate] was designed, synthesized, and encapsulated into liposome (LipoXL-01) by a thin-film dispersion method through formulation screening and optimization. LipoXL-01 was characterized by a particle size of around 100 nm, polydispersity index of 0.200, ζ-potential value of -41 mV, encapsulation efficiency of 93.9%, and drug-loading efficiency of 11.6%. The cellular uptake of LipoXL-01 was increased in a concentration-dependent manner on HCT15 cells. LipoXL-01 could enhance the induction of cell apoptosis and the inhibition of cell migration and arrest the ability of the cell cycle at the S-phase on HCT15 cells better than 5-FU. Additionally, LipoXL-01 exhibited a slow drug release profile with a cumulative release rate of 12% in 8 h. The results of pharmacokinetic and biodistribution studies revealed that LipoXL-01 had a long plasma half-life (7.21 h) and a high tumor accumulation (733 nmol/g at 8 h). The in vivo antitumor effect study also showed that LipoXL-01 had more potent efficacy than 5-FU (65 vs 48% of the tumor-inhibition rate). Simultaneously, negligible systemic toxicity was observed via analyzing the body weight as well as hematological and pathological parameters in the tested mice. The current study suggested that LipoXL-01 might be a promising nanocandidate for chemotherapy of colorectal cancer.

Redox-responsive self-assembled polymeric nanoprodrug for delivery of gemcitabine in B-cell lymphoma therapy

Gemcitabine, as a standard and classic strategy for B-cell lymphoma in the clinic, is limited by its poor pharmacodynamics. Although stimuli-responsive polymeric nanodelivery systems have been widely investigated in the past decade, issues such as complicated procedures, low loading capacity, and uncontrollable release kinetics still hinder their clinical translation. In view of the above considerations, we attempt to construct hyperbranched polyprodrug micelles with considerable drug loading via simple procedures and make use of the particularity of the tumor microenvironment to ensure that the micelles are "inactivated" in normal tissues and "activated" in the tumor microenvironment. Hence, in this work, a redox-responsive polymeric gemcitabine-prodrug (GEM-S-S-PEG) was one-pot synthesized via facile esterification and acylation. The self-assembled subsize (< 100 nm) GEM-S-S-PEG (GSP NPs) with considerable loading capacity (≈ 24.6%) exhibited on-demand and accurate control of gemcitabine release under a simulated tumor microenvironment and thus significantly induced the apoptosis of B-cell lymphoma in vitro. Moreover, in the A20 tumor xenograft murine model, GSP NPs efficiently decreased the expansion of tumor tissues with minimal systemic toxicity. In summary, these redox-responsive and self-assembling GSP NPs with a facile one-pot synthesis procedure may hold great potency in clinical translation for enhanced chemotherapy of B-cell lymphoma. STATEMENT OF SIGNIFICANCE: A redox-responsive polymeric gemcitabine-prodrug (GEM-S-S-PEG) was one-pot synthesized via facile esterification and acylation. The self-assembled subsize (< 100 nm) GEM-S-S-PEG (GSP NPs) exhibited significant tumor therapeutic effects in vitro and in vivo. The polyprodrug GEM-S-S-PEG prepared in this study shows the great potential of redox-responsive nanodrugs for antitumor activity, which provides a reference value for the optimization of the design of functional polyprodrugs.

Emerging Albumin-Binding Anticancer Drugs for Tumor-Targeted Drug Delivery: Current Understandings and Clinical Translation

Albumin has shown remarkable promise as a natural drug carrier by improving pharmacokinetic (PK) profiles of anticancer drugs for tumor-targeted delivery. The exogenous or endogenous albumin enhances the circulatory half-lives of anticancer drugs and passively target the tumors by the enhanced permeability and retention (EPR) effect. Thus, the albumin-based drug delivery leads to a potent antitumor efficacy in various preclinical models, and several candidates have been evaluated clinically. The most successful example is Abraxane, an exogenous human serum albumin (HSA)-bound paclitaxel formulation approved by the FDA and used to treat locally advanced or metastatic tumors. However, additional clinical translation of exogenous albumin formulations has not been approved to date because of their unexpectedly low delivery efficiency, which can increase the risk of systemic toxicity. To overcome these limitations, several prodrugs binding endogenous albumin covalently have been investigated owing to distinct advantages for a safe and more effective drug delivery. In this review, we give account of the different albumin-based drug delivery systems, from laboratory investigations to clinical applications, and their potential challenges, and the outlook for clinical translation is discussed. In addition, recent advances and progress of albumin-binding drugs to move more closely to the clinical settings are outlined.

Recent Development of Prodrugs of Gemcitabine

Gemcitabine is a nucleoside analog that has been used widely as an anticancer drug for the treatment of a variety of conditions, including ovarian, bladder, non-small-cell lung, pancreatic, and breast cancer. However, enzymatic deamination, fast systemic clearance, and the emergence of chemoresistance have limited its efficacy. Different prodrug strategies have been explored in recent years, seeking to obtain better pharmacokinetic properties, efficacy, and safety. Different drug delivery strategies have also been employed, seeking to transform gemcitabine into a targeted medicine. This review will provide an overview of the recent developments in gemcitabine prodrugs and their effectiveness in treating cancerous tumors.

Emerging pro-drug and nano-drug strategies for gemcitabine-based cancer therapy

Gemcitabine has been extensively applied in treating various solid tumors. Nonetheless, the clinical performance of gemcitabine is severely restricted by its unsatisfactory pharmacokinetic parameters and easy deactivation mainly because of its rapid deamination, deficiencies in deoxycytidine kinase (DCK), and alterations in nucleoside transporter. On this account, repeated injections with a high concentration of gemcitabine are adopted, leading to severe systemic toxicity to healthy cells. Accordingly, it is highly crucial to fabricate efficient gemcitabine delivery systems to obtain improved therapeutic efficacy of gemcitabine. A large number of gemcitabine pro-drugs were synthesized by chemical modification of gemcitabine to improve its biostability and bioavailability. Besides, gemcitabine-loaded nano-drugs were prepared to improve the delivery efficiency. In this review article, we introduced different strategies for improving the therapeutic performance of gemcitabine by the fabrication of pro-drugs and nano-drugs. We hope this review will provide new insight into the rational design of gemcitabine-based delivery strategies for enhanced cancer therapy.

Honokiol Prodrug Nanoparticles Based on In Situ Albumin Binding for Long Circulation and High Tumor Uptake

Honokiol (HK) has antiproliferation effects against numerous cancer cells, but its low solubility and bioavailability impede its application. In this study, a prodrug of HK (HP) featuring a maleimide group was synthesized and then mixed with tocopherol polyethylene glycol succinate to prepare prodrug nanoparticles (HP-NPs). In vitro albumin binding experiments showed that HP rapidly reacted with the cysteine thiols of albumin to form a covalent conjugate that released HK slowly in the LLC tumor cell line. In vitro cell apoptosis and uptake assays showed that the cellular uptake of the HK increased into the LLC cells as the albumin concentration increased. Strikingly, in vivo pharmacokinetics and pharmacodynamics measurements demonstrated that the HP-NPs significantly prolonged the circulation and increased tumor accumulation. Taken together, our study demonstrated, both in vitro and in vivo, that the albumin-based HP-NPs delivery system holds significant potential toward the treatment of lung cancer in clinical studies.

Nanoparticulation of Prodrug into Medicines for Cancer Therapy

This article provides a broad spectrum about the nanoprodrug fabrication advances co-driven by prodrug and nanotechnology development to potentiate cancer treatment. The nanoprodrug inherits the features of both prodrug concept and nanomedicine know-how, attempts to solve underexploited challenge in cancer treatment cooperatively. Prodrugs can release bioactive drugs on-demand at specific sites to reduce systemic toxicity, this is done by using the special properties of the tumor microenvironment, such as pH value, glutathione concentration, and specific overexpressed enzymes; or by using exogenous stimulation, such as light, heat, and ultrasound. The nanotechnology, manipulating the matter within nanoscale, has high relevance to certain biological conditions, and has been widely utilized in cancer therapy. Together, the marriage of prodrug strategy which shield the side effects of parent drug and nanotechnology with pinpoint delivery capability has conceived highly camouflaged Trojan horse to maneuver cancerous threats.

Folate-Guided Protein Degradation by Immunomodulatory Imide Drug-Based Molecular Glues and Proteolysis Targeting Chimeras

Molecular glues and proteolysis targeting chimeras (PROTACs) are promising new therapeutic modalities. However, the lack of specificity for molecular glue- or PROTAC-mediated proteolysis in cancer cells versus normal cells raises potential toxicity concerns that will likely limit their clinical applications. Here, we developed a general strategy to deliver immunomodulatory imide drug (IMiD)-based molecular glues and PROTACs to folate receptor α (FOLR1)-positive cancer cells. Specifically, we designed a folate-caged pomalidomide prodrug, FA-S2-POMA, by incorporating a folate group as a caging and guiding element and validated its degradation effect on its neo-substrates in FOLR1-positive cancer cells in a FOLR1-dependent manner. We also developed a folate-caged pomalidomide-based anaplastic lymphoma kinase (ALK) PROTAC, FA-S2-MS4048, which effectively degraded ALK fusion proteins in cancer cells, again in a FOLR1-dependent manner. This novel approach provides a generalizable platform for the targeted delivery of IMiD-based molecular glues and PROTACs to FOLR1-expressing cancer cells with the potential to ameliorate toxicity.

Construction of 2-alkynyl aza-spiro[4,5]indole scaffolds via sequential C-H activations for modular click chemistry libraries

Herein, we have developed a strategy of sequential C-H activations of indole to construct novel 2-alkynyl aza-spiro[4,5]indole scaffolds, which incorporated both alkyne and spiro-units into indole. Gram-scale synthesis and a one-pot, three-step synthesis demonstrated the utility of this protocol. Hybrid conjugates with an oseltamivir derivative further offered a powerful tool for the construction of a versatile spiroindole-containing library via click chemistry.

Design of a Thiol-Responsive, Traceless Prodrug with Rapid Self-Immolation for Cancer Chemotherapy

Prodrugs can be formed by chemical modification of the existing active pharmaceutical ingredients (APIs); however, this often sacrifices their functional efficacy. Self-immolative linkers have recently attracted attention, as they can be designed to release pristine APIs. Herein, we report a strategy to generate a self-immolative prodrug (SIP) that can release pristine doxorubicin (DOX). Compared to conventional linkers, the key SIP DOX (KSIP-DOX) developed here can rapidly and quantitatively release the API due to its strong leaving group after reduction by thiol groups, which are present in tumors. KSIP-DOX has enhanced cellular uptake and improved anticancer efficacy, demonstrating its utility for cancer treatment.

Reduction-responsive dehydroepiandrosterone prodrug nanoparticles loaded with camptothecin for cancer therapy by enhancing oxidation therapy and cell replication inhibition

The pentose phosphate pathway (PPP) plays a critical role by providing ribulose-5-phosphate (Ru5P) and NADPH for nucleotide synthesis and reduction energy, respectively. Accordingly, blocking the PPP process may be an effective strategy for enhancing oxidation therapy and inhibiting cell replication. Here, we designed a novel reduction-responsive PEGylated prodrug and constructed nanoparticles PsD@CPT to simultaneously deliver a PPP blocker, dehydroepiandrosterone (DHEA), and chemotherapeutic camptothecin (CPT) to integrate amplification of oxidation therapy and enhance cell replication inhibition. Following cellular uptake, DHEA and CPT were released from PsD@CPT in the presence of high glutathione (GSH) levels. As expected, DHEA-mediated reduction level decreases and CPT-induced oxidation level increases synergistically, breaking the redox balance to aggravate cancer oxidative stress. In addition, suppressing nucleotide synthesis by DHEA through the reduction of Ru5P and blocking DNA replication by CPT further motivates a synergistic inhibition effect on tumor cell proliferation. The results showed that PsD@CPT featuring multimodal treatment has satisfactory antitumor activity both in vitro and in vivo. This study provides a new tumor treatment strategy, which combines the amplification of oxidative stress and enhancement of inhibition of cell proliferation based on inhibition of the PPP process.

Apoptotic body-mediated intercellular delivery for enhanced drug penetration and whole tumor destruction

Chemotherapeutic nanomedicines can exploit the neighboring effect to increase tumor penetration. However, the neighboring effect is limited, likely by the consumption of chemotherapeutic agents and resistance of internal hypoxic tumor cells. Here, we first propose and demonstrate that apoptotic bodies (ApoBDs) could carry the remaining drugs to neighboring tumor cells after apoptosis. To enhance the ApoBD-based neighboring effect, we fabricated disulfide-linked prodrug nanoparticles consisting of camptothecin (CPT) and hypoxia-activated prodrug PR104A. CPT kills external normoxic tumor cells to produce ApoBDs, while PR104A remains inactive. The remaining drugs could be effectively delivered into internal tumor cells via ApoBDs. Although CPT exhibits low toxicity to internal hypoxic tumor cells, PR104A could be activated to exert strong cytotoxicity, which further facilitates deep penetration of the remaining drugs. Such a synergic approach could overcome the limitations of the neighboring effect to penetrate deep into solid tumors for whole tumor destruction.

Small Molecular Gemcitabine Prodrugs for Cancer Therapy

Gemcitabine as a pyrimidine nucleoside analog anticancer drug has high efficacy for a broad spectrum of solid tumors. Gemcitabine is activated within tumor cells by sequential phosphorylation carried out by deoxycytidine kinase to mono-, di-, and triphosphate nucleotides with the last one as the active form. But the instability, drug resistance and toxicity severely limited its utilization in clinics. In the field of medicinal chemistry, prodrugs have proven to be a very effective means for elevating drug stability and decrease undesirable side effects including the nucleoside anticancer drug such as gemcitabine. Many works have been accomplished in design and synthesis of gemcitabine prodrugs, majority of which were summarized in this review.

A traceless linker for aliphatic amines that rapidly and quantitatively fragments after reduction

Reduction sensitive linkers (RSLs) have the potential to transform the field of drug delivery due to their ease of use and selective cleavage in intracellular environments. However, despite their compelling attributes, developing reduction sensitive self-immolative linkers for aliphatic amines has been challenging due to their poor leaving group ability and high pK_a values. Here a traceless self-immolative linker composed of a dithiol-ethyl carbonate connected to a benzyl carbamate (DEC) is presented, which can modify aliphatic amines and release them rapidly and quantitatively after disulfide reduction. DEC was able to reversibly modify the lysine residues on CRISPR–Cas9 with either PEG, the cell penetrating peptide Arg₁₀, or donor DNA, and generated Cas9 conjugates with significantly improved biological properties. In particular, Cas9–DEC–PEG was able to diffuse through brain tissue significantly better than unmodified Cas9, making it a more suitable candidate for genome editing in animals. Furthermore, conjugation of Arg₁₀ to Cas9 with DEC was able to generate a self-delivering Cas9 RNP that could edit cells without transfection reagents. Finally, conjugation of donor DNA to Cas9 with DEC increased the homology directed DNA repair (HDR) rate of the Cas9 RNP by 50% in HEK 293T cell line. We anticipate that DEC will have numerous applications in biotechnology, given the ubiquitous presence of aliphatic amines on small molecule and protein therapeutics.

Reduction sensitive linkers (RSLs) have the potential to transform the field of drug delivery due to their ease of use and selective cleavage in intracellular environments.

Toward multifunctional anticancer therapeutics: post-synthetic carbonate functionalisation of asymmetric Au(i) bis-N-heterocyclic carbenes

A post-synthetic strategy is reported that allows for functionalisation of Au(i)-bis NHCs via carbonate formation. The scope of this methodology was explored using both aromatic and aliphatic alcohols. As a demonstration of potential utility, the fluorescent Au(i)-bis NHC conjugate 5 was prepared; it was found to have enhanced stability when formulated with bovine serum albumin, localise within the mitochondria of A549 cells and do so without compromising the high cytotoxicity seen for the parent Au(i)-bis NHC system.

Tumor microenvironment responsive drug delivery systems

Conventional tumor-targeted drug delivery systems (DDSs) face challenges, such as unsatisfied systemic circulation, low targeting efficiency, poor tumoral penetration, and uncontrolled drug release. Recently, tumor cellular molecules-triggered DDSs have aroused great interests in addressing such dilemmas. With the introduction of several additional functionalities, the properties of these smart DDSs including size, surface charge and ligand exposure can response to different tumor microenvironments for a more efficient tumor targeting, and eventually achieve desired drug release for an optimized therapeutic efficiency. This review highlights the recent research progresses on smart tumor environment responsive drug delivery systems for targeted drug delivery. Dynamic targeting strategies and functional moieties sensitive to a variety of tumor cellular stimuli, including pH, glutathione, adenosine-triphosphate, reactive oxygen species, enzyme and inflammatory factors are summarized. Special emphasis of this review is placed on their responsive mechanisms, drug loading models, drawbacks and merits. Several typical multi-stimuli responsive DDSs are listed. And the main challenges and potential future development are discussed.

Emerging well-tailored nanoparticulate delivery system based on in situ regulation of the protein corona

The protein corona significantly changes the nanoparticle (NP) identity both physicochemically and biologically, and in situ regulation of specific plasma protein adsorption on NP surfaces has emerged as a promising strategy for disease-targeting therapy. In the past decade, great progress in protein corona regulation has been achieved via surface chemistry-based nanomedicine development. This review first outlines the latest advances in bio-nano interactions, with special attention to factors that influence the protein corona, including NP physicochemical properties, the biological environment and the duration time. Second, NP surface chemistry strategies designed to inhibit and regulate protein corona formation are highlighted, with special emphasis on albumin, transferrin, apolipoprotein (apo) E, vascular endothelial growth factor (VEGF) and retinol binding protein 4 (RBP4). Finally, the current techniques used to characterize the protein corona are briefly discussed.

Overview of Recent Strategic Advances in Medicinal Chemistry

Introducing novel strategies, concepts, and technologies that speed up drug discovery and the drug development cycle is of great importance both in the highly competitive pharmaceutical industry as well as in academia. This Perspective aims to present a "big-picture" overview of recent strategic innovations in medicinal chemistry and drug discovery.

In vitro and in vivo evaluation of a novel mitomycin nanomicelle delivery system

Mitomycin C (MMC), naturally synthesized by Streptomyces caespitosus, is a potent antineoplastic antibiotic for the treatment of various solid tumors. However, the defects of conventional MMC injections have greatly limited its clinical application due to its toxic side effects and non-specific interactions. To solve this problem, the PEG_2k-Fmoc-Ibuprofen (PEG-FIbu) micellar nanocarrier was synthesized and the MMC-loaded micelles (PEG-FIbu/MMC) were prepared by thin film hydration method and characterized. Ibuprofen was used as a hydrophobic domain of PEG-FIbu nanocarrier, and we expect it to synergize with codelivered MMC in the overall antitumor activity. The in vitro release of PEG-FIbu/MMC was examined by dialysis method using MMC injection as a control. Our data suggested that PEG-FIbu/MMC micelles presented appropriate particle size, low CMC value, good stability, high drug loading efficiency and sustained release properties. In vitro cytotoxicity studies with several tumor cell lines showed that the carrier was effective in mediating intracellular delivery of MMC to tumor cells. In vivo pharmacokinetics, tissue distribution and therapeutic study proved that PEG-FIbu/MMC micelles prolonged blood circulation, significantly improved the tumor accumulation and therapeutic efficacy, and reduced undesirable side effect on normal tissues compared to MMC injection. In general, PEG-FIbu/MMC micelles represented an effective strategy to improve the performance for the delivery of MMC and safety of medication.

The introduction of a micellar delivery system of MMC increase efficiency, reduce toxicity and enhance specific interactions in tumor.