Soluble camptothecin derivatives prepared by click cycloaddition chemistry on functional aliphatic polyesters

Synthesis of 4-Arylselanyl-1H-1,2,3-triazoles from Selenium-Containing Carbinols

In this work, we present a simple way to achieve 4-arylselanyl-1H-1,2,3-triazoles from selenium-containing carbinols in a one-pot strategy. The selenium-containing carbinols were used as starting materials to produce a range of selanyl-triazoles in moderate to good yields, including a quinoline and Zidovudine derivatives. One-pot protocols are crucial to the current concerns about waste production and solvent consumption, avoiding the isolation and purification steps of the reactive terminal selanylalkynes. We could also isolate an interesting and unprecedented by-product with one alkynylselenium moiety connected to the triazole.

A Tale of Drug-Carrier Optimization: Controlling Stimuli Sensitivity via Nanoparticle Hydrophobicity through Drug Loading

Interactions between drug molecules, nanocarrier components, and surrounding media influence the properties and therapeutic efficacies of nanomedicines. In this study, we investigate the role that reversible covalent loading of a hydrophobic drug exerts on intra-nanoparticle physical properties and explore the utility of this payload control strategy for tuning the access of active agents and, thereby, the stimuli sensitivity of smart nanomaterials. Glutathione sensitivity was controlled via altering the degree of hydrophobic payload loading of disulfide-linked camptothecin-conjugated sugar-based nanomaterials. Increases in degrees of camptothecin conjugation (f_CPT) decreased aqueous accessibility and reduced glutathione-triggered release. Although the lowest f_CPT gave the fastest camptothecin release, it resulted in the lowest camptothecin concentration. Remarkably, the highest f_CPT resulted in a 5.5-fold improved selectivity against cancer vs noncancerous cells. This work represents an advancement in drug carrier design by demonstrating the importance of controlling the amount of drug loading on the overall payload and its availability.

Synthesis, Molecular Docking, and Preliminary Evaluation of 2-(1,2,3-Triazoyl)benzaldehydes As Multifunctional Agents for the Treatment of Alzheimer's Disease

We described here our results on the use of thiourea as a ligand in the copper catalysed azide-alkyne cycloaddition (CuAAC) of 2-azidobenzaldehyde with alkynes. Reactions were performed reacting 2-azidobenzaldehyde with a range of terminal alkynes using 10 mol % of copper iodide as a catalyst, 20 mol % of thiourea as a ligand, triethylamine as base, DMSO as solvent at 100 °C under nitrogen atmosphere. The corresponding 2-(1H-1,2,3-triazoyl)-benzaldehydes (2-TBH) were obtained in moderated to excellent yields and according our experiments, the use of thiourea decreases the formation of side products. The obtained compounds were screened for their binding affinity with multiple therapeutic targets of AD by molecular docking: β-secretase (BACE), glycogen synthase kinase (GSK-3β) and acetylcholinesterase (AChE). The three compounds with highest affinity, 5 a (2-(4-phenyl-1H-1,2,3-triazol-1-yl)benzaldehyde), 5 b (2-(4-(p-tolyl)-1H-1,2,3-triazol-1-yl)benzaldehyde), and 5 d (2-(4-(4-(tert-butyl)phenyl)-1H-1,2,3-triazol-1-yl)benzaldehyde) were selected and evaluated on its antioxidant effect, in view of select the most promising one to perform the in vivo validation. Due the antioxidant potential ally to the affinity with BACE, GSK-3β and AChE, compound 5 b was evaluated in a mouse model of AD induced by intracerebroventricular injection of streptozotocin (STZ). Our results indicate that 5 b (1 mg/kg) treatment during 20 days is able to reverse the cognitive and memory impairment induced by STZ trough the modulation of AChE activity, amyloid cascade and GSK-3β expression.

A multifunctional biodegradable brush polymer-drug conjugate for paclitaxel/gemcitabine co-delivery and tumor imaging

A multifunctional biodegradable brush polymer-drug conjugate (BPDC) is developed for the co-delivery of hydrophobic paclitaxel (PTX) and hydrophilic gemcitabine (GEM) chemotherapeutics, as well as a tumor imaging agent. A novel ternary copolymer of conventional, acetylenyl-functionalized and allyl-functionalized lactides is prepared to serve as the backbone precursor of BPDC. Acetylenyl groups of the copolymer are then reacted with poly(ethylene glycol) (PEG) side chains and cyanine5.5, a fluorescent probe, via azide-alkyne click reactions. Subsequently, the allyl groups of the yielded PEG-grafted brush polymer are used to covalently link PTX and GEM onto the backbone via thiol-ene click reactions. The resulting BPDC exhibits an average hydrodynamic diameter of 111 nm. Sustained and simultaneous release of PTX and GEM from the BPDC is observed in phosphate buffered saline, with the release of PTX showing sensitivity in mild acidic conditions. In vitro studies using MIA PaCa-2 human pancreatic cancer cells illustrate the cellular uptake and cytotoxicity of the BPDC. In vivo, the BPDC possesses long blood circulation, tumor accumulation, and enables optical tumor imaging. Further development and testing is warranted for multifunctional conjugated brush polymer systems that integrate combination chemotherapies and imaging.

Effect of structural factors on release profiles of camptothecin from block copolymer conjugates with high load of drug

The aim of the present work was the synthesis and study the kinetics and profiles of camptothecin (CPT) release form block co- and ter-polymer conjugates comprising polylactide (PLA) segments and CPT moieties, structurally diverse by degrees of branching, content of d-PLA units and poly(ethylene glycol) methyl ether methacrylate (PEGMA). Six PLA, non-toxic macroinitiators (MIs), terminated with α-bromoester were synthesized. MIs were subjected to polymerization of CPT methacrylic derivative (CPTMA) with PEGMA at various ratios. The average contents of CPT from elemental analysis, NMR and UV-GPC were approximate to each other. The number of CPT molecules and PEGMA units was in the range of 9-195 and 0-280 per conjugate, respectively. PEGMA units plasticized PLA causing increase of its crystallinity, whereas 7% and more of d-PLA caused material amorphous. PEGMA units decreased thermal stability of conjugates, however it compatibillized the separated phases of PLA and PCPTMA, based on AFM. In vitro release rate of CPT from linear PLA conjugates deposited on injection-molded PLA bars increased by introduction of PEGMA units with zero-order kinetics and Korsmeyer-Peppas model indicating the super case II transport. Branched conjugates revealed some burst release and then the release was rather of first-order-kinetics with respect to CPT with non-Fickian transport.

Preparation and physicochemical characterization of camptothecin conjugated poly amino ester–methyl ether poly ethylene glycol copolymer

In the present study, camptothecin grafted poly amino ester-methyl ether polyethylene glycol (CPT-PEA-MPEG) as a novel copolymer was synthesized by Michael reaction at different ratios of MPEG and CPT (60 : 40 and 80 : 20). The microemulsion was used to prepare nanomicelles, and in vitro cytotoxicity was performed on the HT29 cell line, and cell survival was measured by MTT assay. The syntheses were confirmed by ¹H NMR and FT-IR. Several characterization methods including CMC, particle size, size distribution, and transmission electron microscopy were performed to evaluate features of prepared nanomicelles. Low critical micelle concentration, small particle size and IC₅₀ of 0.1 mg ml⁻¹ at MPEG to CPT ratio of 60 : 40 make this micelle a promising drug delivery carrier. CPT-PAE-MPEG nanomicelles at a MPEG : CPT ratio of 60 : 40 can be a suitable choice to improve the physiochemical properties of CPT and its therapeutic effect, while it can be potentially used as a nano-carrier for other anticancer drugs to purpose a dual drug delivery.

In the present study, camptothecin grafted poly amino ester-methyl ether polyethylene glycol (CPT-PEA-MPEG) as a novel copolymer was synthesized by Michael reaction at different ratios of MPEG and CPT (60 : 40 and 80 : 20).

Radical Copolymerization of Vinyl Ethers and Cyclic Ketene Acetals as a Versatile Platform to Design Functional Polyesters

Free-radical copolymerization of cyclic ketene acetals (CKAs) and vinyl ethers (VEs) was investigated as an efficient yet simple approach for the preparation of functional aliphatic polyesters. The copolymerization of CKA and VE was first predicted to be quasi-ideal by DFT calculations. The theoretical prediction was experimentally confirmed by the copolymerization of 2-methylene-1,3-dioxepane (MDO) and butyl vinyl ether (BVE), leading to r_MDO =0.73 and r_BVE =1.61. We then illustrated the versatility of this approach by preparing different functional polyesters: 1) copolymers functionalized by fluorescent probes; 2) amphiphilic copolymers grafted with poly(ethylene glycol) (PEG) side chains able to self-assemble into PEGylated nanoparticles; 3) antibacterial films active against Gram-positive and Gram-negative bacteria (including a multiresistant strain); and 4) cross-linked bioelastomers with suitable properties for tissue engineering applications.

Using an RNAi Signature Assay To Guide the Design of Three-Drug-Conjugated Nanoparticles with Validated Mechanisms, In Vivo Efficacy, and Low Toxicity

Single-nanoparticle (NP) combination chemotherapeutics are quickly emerging as attractive alternatives to traditional chemotherapy due to their ability to increase drug solubility, reduce off-target toxicity, enhance blood circulation lifetime, and increase the amount of drug delivered to tumors. In the case of NP-bound drugs, that is, NP-prodrugs, the current standard of practice is to assume that the subcellular mechanism of action for each drug released from the NP mirrors that of the unbound, free-drug. Here, we use an RNAi signature assay for the first time to examine the mechanism of action of multidrug-conjugated NP prodrugs relative to their small molecule prodrugs and native drug mechanisms of action. Additionally, the effective additive contribution of three different drugs in a single-NP platform is characterized. The results indicate that some platinum(IV) cisplatin prodrugs, although cytotoxic, may not have the expected mechanism of action for cisplatin. This insight was utilized to develop a novel platinum(IV) oxaliplatin prodrug and incorporate it into a three-drug-conjugated NP, where each drug's mechanism of action is preserved, to treat tumor-bearing mice with otherwise lethal levels of chemotherapy.

Phenylselanyl-1H-1,2,3-triazole-4-carbonitriles: synthesis, antioxidant properties and use as precursors to highly functionalized tetrazoles

We describe herein our results on the synthesis, antioxidant properties and chemical diversification of phenylselanyl-1H-1,2,3-triazole-4-carbonitriles.

The Sequence-Specific Cellular Uptake of Spherical Nucleic Acid Nanoparticle Conjugates

The sequence-dependent cellular uptake of spherical nucleic acid nanoparticle conjugates (SNAs) is investigated. This process occurs by interaction with class A scavenger receptors (SR-A) and caveolae-mediated endocytosis. It is known that linear poly(guanine) (poly G) is a natural ligand for SR-A, and it has been proposed that interaction of poly G with SR-A is dependent on the formation of G-quadruplexes. Since G-rich oligonucleotides are known to interact strongly with SR-A, it is hypothesized that SNAs with higher G contents would be able to enter cells in larger amounts than SNAs composed of other nucleotides, and as such, cellular internalization of SNAs is measured as a function of constituent oligonucleotide sequence. Indeed, SNAs with enriched G content show the highest cellular uptake. Using this hypothesis, a small molecule (camptothecin) is chemically conjugated with SNAs to create drug-SNA conjugates and it is observed that poly G SNAs deliver the most camptothecin to cells and have the highest cytotoxicity in cancer cells. Our data elucidate important design considerations for enhancing the intracellular delivery of spherical nucleic acids.

Well-defined diblock brush polymer–drug conjugates for sustained delivery of paclitaxel

The synthesis, characterization and property studies of paclitaxel (PTXL)-containing brush polymer–drug conjugates (BPDCs) are presented and the influence of grafting structures of BPDCs on their assembly behaviour, drug release profile and therapeutic effects is discussed in this article.

A degradable brush polymer–drug conjugate for pH-responsive release of doxorubicin

We report the synthesis, characterization andin vitroassessment of a degradable brush polymer–drug conjugate which can enable acid-triggered release of doxorubicin (DOX).

Polylactide-graft-doxorubicin nanoparticles with precisely controlled drug loading for pH-triggered drug delivery

Nanoparticles (NPs) with high drug loading and pH-responsivity were prepared by nanoprecipitation of a hydrophobic polymer-drug conjugate (PDC). The PDC, polylactide-graft-doxorubicin (PLA-g-DOX), was synthesized by azide-alkyne click reaction to transform acetylene-functionalized PLA into PLA-graft-aldehyde (PLA-g-ALD), followed by DOX conjugation to form acid-sensitive Schiff base linkage between drug moieties and polymer scaffold. The DOX loading amount in PLA-g-DOX PDC was determined to be 32 wt % by (1)H NMR and UV-vis spectroscopies. PLA-g-DOX PDC was further used to prepare NPs with precisely controlled drug loading by nanoprecipitation in the presence of a PEGylated surfactant. The effects of organic solvent, PLA-g-DOX PDC concentration and PLA-g-DOX/surfactant mass ratio on size and size distribution of NPs were systematically examined based on analysis by dynamic light scattering (DLS) and transmission electron microscopy (TEM). NPs prepared under the optimal conditions exhibited well-defined spherical morphology with volume-average hydrodynamic diameter (Dh) around 100 nm. Due to the Schiff base conjugation linkage in PLA-g-DOX PDC, acid-sensitive drug release behavior of the NPs was observed. In vitro studies against MCF-7 breast cancer cells showed that the NPs can be readily taken up and result in enhanced therapeutic efficiency as compared to DOX·HCl, indicating their promising potential applications as anticancer nanomedicines.

Recoverable Cu/SiO2 composite-catalysed click synthesis of 1,2,3-triazoles in water media

An eco-friendly multicomponent reaction for the synthesis of 1,2,3-triazoles using a recoverable and recyclable Cu/SiO₂ composite as the catalyst is reported.

Designing PEGylated therapeutic molecules: advantages in ADMET properties

BACKGROUND

PEGylation, association of poly(ethylene glycol) (PEG) to drug molecules or drug-bearing particles, is one of the most promising techniques on the way to improve the pharmacokinetic features of a drug which, in turn, leads to pharmacodynamic improvements.

OBJECTIVE

The aim of this review is to describe PEGylation as a procedure for alteration of drug molecular structure with the main emphasis on its pharmacokinetic consequences.

METHODS

After a brief but concise overview of the history and chemistry of PEGylation, the boundary of this literature survey is confined to the findings and reports on the impact of PEGylation on biodistribution and bioelimination of therapeutic molecules.

CONCLUSION

It is concluded, based on the whole body of the data in literature, that the main results of PEGylation on pharmacokinetic properties of the drug include prolongation of lifespan in circulation, alterations in drug elimination pathway(s) and changes in drug biodistribution profile, among others, which all are derived from the structural changes that occur in the drug molecule, mainly reversible attachment of a large polymeric moiety to parent drug.

SiO₂ nanoparticles as platform for delivery of nucleoside triphosphate analogues into cells

A system for delivery of analogues of 2'-deoxyribonucleoside triphosphate (dNTP) based on SiO(2) nanoparticles was proposed. A simple and versatile method was developed for the preparation of SiO(2)-dNTP conjugates using the 'click'-reaction between premodified nanoparticles containing the azido groups and dNTP containing the alkyne-modified γ-phosphate group. The substrate properties of SiO(2)-dNTP were tested using Klenow fragment and HIV reverse transcriptase. Nucleoside triphosphates being a part of the SiO(2)-dNTP nanocomposites were shown to be incorporated into the growing DNA chain. The rate of polymerization with the use of SiO(2)-dNTP or common dNTP in case of HIV reverse transcriptase differed insignificantly. It was shown by confocal microscopy that the proposed SiO(2)-dNTP nanocomposites bearing the fluorescent label penetrate into cells and even into cellular nuclei.

Well-defined degradable brush polymer-drug conjugates for sustained delivery of Paclitaxel

To achieve a conjugated drug delivery system with high drug loading but minimal long-term side effects, a degradable brush polymer-drug conjugate (BPDC) was synthesized through azide-alkyne click reaction of acetylene-functionalized polylactide (PLA) with azide-functionalized paclitaxel (PTXL) and poly(ethylene glycol) (PEG). Well-controlled structures of the resulting BPDC and its precursors were verified by (1)H NMR and gel permeation chromatography (GPC) characterizations. With nearly quantitative click efficiency, drug loading amount of the BPDC reached 23.2 wt %. Both dynamic light scattering (DLS) analysis and transmission electron microscopy (TEM) imaging indicated that the BPDC had a nanoscopic size around 10-30 nm. The significant hydrolytic degradability of the PLA backbone of the BPDC was confirmed by GPC analysis of its incubated solution. Drug release study showed that PTXL moieties can be released through the cleavage of the hydrolyzable conjugation linkage in pH 7.4 at 37 °C, with 50% release in about 22 h. As illustrated by cytotoxicity study, while the polymeric scaffold of the BPDC is nontoxic, the BPDC exhibited higher therapeutic efficacy toward MCF-7 cancer cells than free PTXL at 0.1 and 1 μg/mL. Using Nile red as encapsulated fluorescence probe, cell uptake study showed effective internalization of the BPDC into the cells.

Synthesis of water-soluble camptothecin-polyoxetane conjugates via click chemistry

Water-soluble camptothecin (CPT)-polyoxetane conjugates were synthesized using a clickable polymeric platform P(EAMO) that was made by polymerization of acetylene-functionalized 3-ethyl-3-(hydroxymethyl)oxetane (i.e., EAMO). CPT was first modified with a linker 6-azidohexanoic acid via an ester linkage to yield CPT-azide. CPT-azide was then click coupled to P(EAMO) in dichloromethane using bromotris(triphenylphosphine)copper(I)/N,N-diisopropylethylamine. For water solubility and cytocompatibility improvement, methoxypolyethylene glycol azide (mPEG-azide) was synthesized from mPEG 750 g mol(-1) and click grafted using copper(II) sulfate and sodium ascorbate to P(EAMO)-g-CPT. (1)H NMR spectroscopy confirmed synthesis of all intermediates and the final product P(EAMO)-g-CPT/PEG. CPT was found to retain its therapeutically active lactone form. The resulting P(EAMO)-g-CPT/PEG conjugates were water-soluble and produced dose-dependent cytotoxicity to human glioma cells and increased γ-H2AX foci formation, indicating extensive cell cycle-dependent DNA damage. Altogether, we have synthesized CPT-polymer conjugates able to induce controlled toxicity to human cancer cells.

Nanomicelle with long-term circulation and enhanced stability of camptothecin based on mPEGylated alpha,beta-poly (L-aspartic acid)-camptothecin conjugate

To enhance the stability and long-term circulation of camptothecin (CPT), mPEGylated alpha,beta-poly (L-aspartic acid)-CPT conjugates were synthesized, and used to fabricate nanomicelle. Firstly, alpha,beta-poly (L-aspartic acid) derivative (PAA-der) containing alkyne groups was synthesized via the ring-opening of PSI with propargyl amine. And then, azide-functionalized CPT derivatives (CPT-N(3)) and azide-terminated poly (ethylene glycol) methyl ether (mPEG-N(3)) were conjugated with PAA-der by click cycloaddition to give mPEG-graft-PAA-CPT conjugates. The formation of mPEG-graft-PAA-CPT nanomicelles was confirmed by fluorescence spectrophotoscopy and particle size measurements. It was found that all the nanomicelles showed spherical shapes with size about 178 nm. MPEG-graft-PAA-CPT nanomicelles showed good storage stability, even incubation at 37 degrees C for 60 days, and improved the stability of CPT lactone form in aqueous media. A steady release rate of CPT was kept for 72h, suggested the great potential of mPEG-graft-PAA-CPT nanomicelles as polymer prodrug of CPT.

Cancer therapies utilizing the camptothecins: a review of the in vivo literature

This review summarizes the in vivo assessment-preliminary, preclinical, and clinical-of chemotherapeutics derived from camptothecin or a derivative. Camptothecin is a naturally occurring, pentacyclic quinoline alkaloid that possesses high cytotoxic activity in a variety of cell lines. Major limitations of the drug, including poor solubility and hydrolysis under physiological conditions, prevent full clinical utilization. Camptothecin remains at equilibrium in an active lactone form and inactive hydrolyzed carboxylate form. The active lactone binds to DNA topoisomerase I cleavage complex, believed to be the single site of activity. Binding inhibits DNA religation, resulting in apoptosis. A series of small molecule camptothecin derivatives have been developed that increase solubility, lactone stability and bioavailability to varying levels of success. A number of macromolecular agents have also been described wherein camptothecin(s) are covalently appended or noncovalently associated with the goal of improving solubility and lactone stability, while taking advantage of the tumor physiology to deliver larger doses of drug to the tumor with lower systemic toxicity. With the increasing interest in drug delivery and polymer therapeutics, additional constructs are anticipated. The goal of this review is to summarize the relevant literature for others interested in the field of camptothecin-based therapeutics, specifically in the context of biodistribution, dosing regimens, and pharmacokinetics with the desire of providing a useful source of comparative data. To this end, only constructs where in vivo data is available are reported. The review includes published reports in English through mid-2009.

Polymeric phosphorylcholine-camptothecin conjugates prepared by controlled free radical polymerization and click chemistry

Novel polymer-drug conjugates, consisting of zwitterionic poly(methacryloyloxyethyl phosphorylcholine) (polyMPC) as the polymer component, and camptothecin (CPT) as the drug, were prepared by two methods. In one case, CPT was transformed by acylation into a functional initiator for copper catalyzed atom transfer radical polymerization (ATRP), and polyMPC was grown from this therapeutic initiator. In the other case, a one-pot ATRP-"click" conjugation strategy was employed to synthesize novel polyMPC structures containing multiple copies of the drug pendant to the zwitterionic polymer chain. The latter method allows polyMPC-graft-CPT conjugates to be prepared with a high weight percent drug loading (up to 14% CPT) with excellent solubility in pure water (>250 mg/mL). The linkage chemistry chosen between the polyMPC backbone and the pendant drugs proved critically important for assuring drug release within a time frame reasonable to consider these structures as a platform for injectable cancer therapeutics. Liberation of the drug from the polymer backbone was monitored by high-performance liquid chromatography, using size-exclusion and reverse-phase columns, and the toxicity of the polymer-drug conjugates was examined in cell culture against breast (MCF7), ovarian (OVCAR-3), and colorectal (COLO 205) cancer cell lines.