Synthesis and in vitro efficacy of acid-sensitive poly(ethylene glycol) paclitaxel conjugates

Tumor-targeted Drug Delivery by Nanocomposites

BACKGROUND

Tumor-targeted delivery by nanoparticles is a great achievement towards the use of highly effective drug at very low doses. The conventional development of tumor-targeted delivery by nanoparticles is based on enhanced permeability and retention (EPR) effect and endocytosis based on receptor-mediated are very demanding due to the biological and natural complications of tumors as well as the restrictions on the design of the accurate nanoparticle delivery systems.

METHODS

Different tumor environment stimuli are responsible for triggered multistage drug delivery systems (MSDDS) for tumor therapy and imaging. Physicochemical properties, such as size, hydrophobicity and potential transform by MSDDS because of the physiological blood circulation different, intracellular tumor environment. This system accomplishes tumor penetration, cellular uptake improved, discharge of drugs on accurate time, and endosomal discharge.

RESULTS

Maximum drug delivery by MSDDS mechanism to target therapeutic cells and also tumor tissues and sub cellular organism. Poorly soluble compounds and bioavailability issues have been faced by pharmaceutical industries, which are resolved by nanoparticle formulation.

CONCLUSION

In our review, we illustrate different types of triggered moods and stimuli of the tumor environment, which help in smart multistage drug delivery systems by nanoparticles, basically a multi-stimuli sensitive delivery system, and elaborate their function, effects, and diagnosis.

Stimulus-cleavable chemistry in the field of controlled drug delivery

This review comprehensively summarises stimulus-cleavable linkers from various research areas and their cleavage mechanisms, thus provides an insightful guideline to extend their potential applications to controlled drug release from nanomaterials.

Mannose-Decorated Dendritic Polyglycerol Nanocarriers Drive Antiparasitic Drugs To Leishmania infantum-Infected Macrophages

Macrophages are hosts for intracellular pathogens involved in numerous diseases including leishmaniasis. They express surface receptors that may be exploited for specific drug-targeting. Recently, we developed a PEGylated dendritic polyglycerol-based conjugate (PG–PEG) that colocalizes with intracellular parasite. We hereby study the effect of surface decoration with mannose units on the conjugates’ targeting ability toward leishmania intracellular parasites. Murine and human macrophages were exposed to fluorescently labeled mannosylated PG–PEG and uptake was quantified by flow cytometry analysis. Nanocarriers bearing five mannose units showed the highest uptake, which varied between 30 and 88% in the population in human and murine macrophages, respectively. The uptake was found to be dependent on phagocytosis and pinocytosis (80%), as well as clathrin-mediated endocytosis (79%). Confocal microscopy showed that mannosylated PG–PEGs target acidic compartments in macrophages. In addition, when both murine and human macrophages were infected and treated, colocalization between parasites and mannosylated nanoconjugates was observed. Leishmania-infected bone marrow-derived macrophages (BMM) showed avidity by mannosylated PG–PEG whereas non-infected macrophages rarely accumulated conjugates. Moreover, the antileishmanial activity of Amphotericin B was kept upon conjugation to mannosylated PG–PEG through a pH-labile linker. This study demonstrates that leishmania infected macrophages are selectively targeted by mannosylated PEGylated dendritic conjugates.

A Facile, One-Pot, Surfactant-Free Nanoprecipitation Method for the Preparation of Nanogels from Polyglycerol⁻Drug Conjugates that Can Be Freely Assembled for Combination Therapy Applications

A well-established strategy to treat drug resistance is the use of multiple therapeutics. Polymer-based drug delivery systems (DDS) can facilitate a simultaneous delivery of two or more drugs. In this study, we developed and synthesized a dendritic polyglycerol (PG) nanogel (NG) system that allows for free combination of different fixed ratios of active compound conjugates within a single NG particle. As a proof of concept, we synthesized NGs bearing the chemotherapeutic agent doxorubicin (DOX) and paclitaxel (PTX) in different ratios, as well as conjugated dye molecules. Our combination PG NGs were formed by simply mixing PG–drug/dye conjugates bearing free thiol groups with PG-acrylate in an inverse surfactant-free nanoprecipitation method. With this method we obtained PG-NGs in the size range of 110–165 nm with low polydispersity indices. Solubility of hydrophobic PTX was improved without the need for additional solubilizing agents such as polyethylene glycol (PEG). Interestingly, we found that our NGs made from PG-DOX conjugates have a high quenching efficiency for DOX, which could be interesting for theranostic purposes.

Co-targeting the tumor endothelium and P-selectin-expressing glioblastoma cells leads to a remarkable therapeutic outcome

Glioblastoma is a highly aggressive brain tumor. Current standard-of-care results in a marginal therapeutic outcome, partly due to acquirement of resistance and insufficient blood-brain barrier (BBB) penetration of chemotherapeutics. To circumvent these limitations, we conjugated the chemotherapy paclitaxel (PTX) to a dendritic polyglycerol sulfate (dPGS) nanocarrier. dPGS is able to cross the BBB, bind to P/L-selectins and accumulate selectively in intracranial tumors. We show that dPGS has dual targeting properties, as we found that P-selectin is not only expressed on tumor endothelium but also on glioblastoma cells. We delivered dPGS-PTX in combination with a peptidomimetic of the anti-angiogenic protein thrombospondin-1 (TSP-1 PM). This combination resulted in a remarkable synergistic anticancer effect on intracranial human and murine glioblastoma via induction of Fas and Fas-L, with no side effects compared to free PTX or temozolomide. This study shows that our unique therapeutic approach offers a viable alternative for the treatment of glioblastoma.

Integrin-targeted nano-sized polymeric systems for paclitaxel conjugation: a comparative study

The generation of rationally designed polymer therapeutics via the conjugation of low molecular weight anti-cancer drugs to water-soluble polymeric nanocarriers aims to improve the therapeutic index. Here, we focus on applying polymer therapeutics to target two cell compartments simultaneously - tumour cells and angiogenic endothelial cells. Comparing different polymeric backbones carrying the same therapeutic agent and targeting moiety may shed light on any correlation between the choice of polymer and the anti-cancer activity of the conjugate. Here, we compared three paclitaxel (PTX)-bound conjugates with poly-l-glutamic acid (PGA, 4.9 mol%), 2-hydroxypropylmethacrylamide (HPMA, 1.2 mol%) copolymer, or polyethyleneglycol (PEG, 1:1 conjugate). PGA and HPMA copolymers are multivalent polymers that allow the conjugation of multiple compounds within the same polymer backbone, while PEG is a bivalent commercially available Food and Drug Administration (FDA)-approved polymer. We further conjugated PGA-PTX and PEG-PTX with the integrin α_vβ₃-targeting moiety RGD (5.5 mol% and 1:1 conjugate, respectively). We based our selection on the overexpression of integrin α_vβ₃ on angiogenic endothelial cells and several types of cancer cells. Our findings suggest that the polymer structure has major effect on the conjugate's activity on different tumour compartments. A multivalent PGA-PTX-E-[c(RGDfK)₂] conjugate displayed a stronger inhibitory effect on the endothelial compartment, showing a 50% inhibition of the migration of human umbilical vein endothelial cell cells, while a PTX-PEG-E-[c(RGDfK)₂] conjugate possessed enhanced anti-cancer activity on MDA-MB-231 tumour cells (IC₅₀ = 20 nM versus IC₅₀ 300 nM for the PGA conjugate).

Designing Smart Materials with Recombinant Proteins

Recombinant protein design allows modular protein domains with different functionalities and responsive behaviors to be easily combined. Inclusion of these protein domains can enable recombinant proteins to have complex responses to their environment (e.g., temperature-triggered aggregation followed by enzyme-mediated cleavage for drug delivery or pH-triggered conformational change and self-assembly leading to structural stabilization by adjacent complementary residues). These "smart" behaviors can be tuned by amino acid identity and sequence, chemical modifications, and addition of other components. A wide variety of domains and peptides have smart behavior. This review focuses on protein designs for self-assembly or conformational changes due to stimuli such as shifts in temperature or pH.

Current Multistage Drug Delivery Systems Based on the Tumor Microenvironment

The development of traditional tumor-targeted drug delivery systems based on EPR effect and receptor-mediated endocytosis is very challenging probably because of the biological complexity of tumors as well as the limitations in the design of the functional nano-sized delivery systems. Recently, multistage drug delivery systems (Ms-DDS) triggered by various specific tumor microenvironment stimuli have emerged for tumor therapy and imaging. In response to the differences in the physiological blood circulation, tumor microenvironment, and intracellular environment, Ms-DDS can change their physicochemical properties (such as size, hydrophobicity, or zeta potential) to achieve deeper tumor penetration, enhanced cellular uptake, timely drug release, as well as effective endosomal escape. Based on these mechanisms, Ms-DDS could deliver maximum quantity of drugs to the therapeutic targets including tumor tissues, cells, and subcellular organelles and eventually exhibit the highest therapeutic efficacy. In this review, we expatiate on various responsive modes triggered by the tumor microenvironment stimuli, introduce recent advances in multistage nanoparticle systems, especially the multi-stimuli responsive delivery systems, and discuss their functions, effects, and prospects.

Design, synthesis, and evaluation of water-soluble morpholino-decorated paclitaxel prodrugs with remarkably decreased toxicity

Novel water-soluble paclitaxel prodrugs were designed and synthesized by introducing morpholino groups through different linkers. These derivatives showed 400-20,000-times greater water solubility than paclitaxel as well as comparable activity in MCF-7 and HeLa cell lines. The prodrug PM4 was tested in the S-180 tumor mouse model, with paclitaxel as the positive control. The results showed that PM4 had comparable antitumor activity as paclitaxel, with tumor inhibition of 54% versus 56%, and remarkably decreased toxicity. The survival rate of treated mice was 8/8 in the PM4 group, compared to 3/8 in the paclitaxel group.

Mechanisms and biomaterials in pH-responsive tumour targeted drug delivery: A review

As the mainstay in the treatment of various cancers, chemotherapy plays a vital role, but still faces many challenges, such as poor tumour selectivity and multidrug resistance (MDR). Targeted drug delivery using nanotechnology has provided a new strategy for addressing the limitations of the conventional chemotherapy. In the last decade, the volume of research published in this area has increased tremendously, especially with functional nano drug delivery systems (nanocarriers). Coupling a specific stimuli-triggered drug release mechanism with these delivery systems is one of the most prevalent approaches for improving therapeutic outcomes. Among the various stimuli, pH triggered delivery is regarded as the most general strategy, targeting the acidic extracellular microenvironment and intracellular organelles of solid tumours. In this review, we discuss recent advances in the development of pH-sensitive nanocarriers for tumour-targeted drug delivery. The review focuses on the chemical design of pH-sensitive biomaterials, which are used to fabricate nanocarriers for extracellular and/or intracellular tumour site-specific drug release. The pH-responsive biomaterials bring forth conformational changes in these nanocarriers through various mechanisms such as protonation, charge reversal or cleavage of a chemical bond, facilitating tumour specific cell uptake or drug release. A greater understanding of these mechanisms will help to design more efficient drug delivery systems to address the challenges encountered in conventional chemotherapy.

From solution to in-cell study of the chemical reactivity of acid sensitive functional groups: a rational approach towards improved cleavable linkers for biospecific endosomal release

pH-Sensitive linkers designed to undergo selective hydrolysis at acidic pH compared to physiological pH can be used for the selective release of therapeutics at their site of action.

Synthesis and biological evaluation of new nanosized aromatic polyamides containing amido- and sulfonamidopyrimidines pendant structures

Background

Antibiotics are biocides or products that inhibit the growth of microorganisms in the living cells and there are extensive works directed to develop efficient antimicrobial agents. The sulfonamide-containing polymers have great potential to resist gram-positive or gram-negative bacterial and fungal attacks. As a therapeutic agent, the sulfonamides have been reported as antitumor and antimicrobial agents against bacteria, being more potent against gram positive rather than gram negative strains. Design of new classes of inhibitors bearing fluorescent tails, as therapeutic and imaging agents, is currently an active area of research. Here, we describe the synthesis of a new family of polyamides based on chlorophenyl-3,5-diaminobenzamides, methyl substituted pyrimidinoamido-3,5-diamino- benzamides and methyl substituted pyrimidinosulfonamido-3,5-diaminobenzamides and evaluation of their thermal, optical and antimicrobial properties.

Results

We report the synthesis of a new series of nanosized polyamides containing bioactive pendent structures. The spherical nanosized polymer particles are soluble in many organic solvents and exhibited emissions ranging from blue to orange wavelength depending on the nature of the signaling unit. Pyrimidine- and p-chloroaromatic containing polymers exhibited higher bioactivity than that contain the sulfonamide group. The amidopyrimidine polymers exhibited remarkable antifungal and antibacterial activity and thus, these types of polymers are promising candidates for biomedical applications.

Conclusions

The SEM analysis indicated that most of the polyamides were organized as well defined nano sized spheres, but in certain derivatives small amount of aggregated nanospheres were also observed. Thermal analyses were studied up to 700 °C and results showed comparable thermal behavior. The optical results revealed that polymeric series (A) exhibited orange emission, series (B) showed green emission while series (C) exhibited yellow and blue emissions. Benzene/pyridine structure interchange resulted in red shifted peaks attributed to the localized lone pair of electrons on a nitrogen atom which offer a greater electron affinity and better electron-transporting properties. The amido- and sulfonamide pyrimidine containing polymers exhibited the most potent antimicrobial activity. Relative to the reference Gentamicin, the polymer 54 exhibited comparable antibacterial activity against gram negative bacteria. Analogues 52 and 57 exhibited remarkable antibacterial activities compared to the references used. Thus, these polyamides are likely to be promising broad spectrum antibacterial agents and deserve further investigation at the molecular level.Graphical abstract:

Elastin-like polypeptide for improved drug delivery for anticancer therapy: preclinical studies and future applications

INTRODUCTION

Despite their poor specificity, small molecule drugs are considered more powerful and effective than other current chemotherapies. A promising method for targeting these anticancer drugs to tumors, elastin-like polypeptides (ELP), has recently emerged. When an anticancer drug that has been conjugated to an ELP is administered, and focal hyperthermia applied, the thermoresponsive properties and enhanced permeability and retention effects of the ELP facilitate drug aggregation within tumor tissues. By incorporating a cell penetrating peptide onto this ELP-chemotherapeutic construct, even greater drug uptake into tumor cells can be achieved.

AREAS COVERED

The review explores the preclinical study progress of ELP-based drug delivery technology and discusses its potential in cancer therapy. Recent experimental work has shown that a delivery construct consisting of an ELP-therapeutic peptide (e.g., the c-Myc-inhibitory peptide, or the p21(WAF1/CIP1)-derived peptide), as well as ELP-small molecule drugs (e.g., doxorubicin, paclitaxel), can be thermally targeted to accumulate in tumors and diminish their growth.

EXPERT OPINION

ELP drug delivery technology is complementary and synergistic to current drug delivery modalities and based on existing hyperthermia technology. By using this technology to achieve chemotherapeutic targeting, efficacy can be improved and side effects reduced in comparison with current regimens, providing treatment alternatives and/or augmenting current therapies for cancer treatment.

Analogue-based drug discovery: Contributions to medicinal chemistry principles and drug design strategies. Microtubule stabilizers as a case in point (Special Topic Article)

The benefits of utilizing marketed drugs as starting points to discover new therapeutic agents have been well documented within the IUPAC series of books that bear the title Analogue-based Drug Discovery (ABDD). Not as clearly demonstrated, however, is that ABDD also contributes to the elaboration of new basic principles and alternative drug design strategies that are useful to the field of medicinal chemistry in general. After reviewing the ABDD programs that have evolved around the area of microtubule-stabilizing chemo-therapeutic agents, the present article delineates the associated research activities that additionally contributed to general strategies that can be useful for prodrug design, identifying pharmacophores, circumventing multidrug resistance (MDR), and achieving targeted drug distribution.

Targeted therapy for cancer using pH-responsive nanocarrier systems

Most of the conventional chemotherapeutic agents used against cancer have poor efficacy. An approach to improve the efficacy of cancer chemotherapy is the development of carrier systems that can be triggered to release the anticancer drug in response to extracellular or intracellular chemical stimuli. To this end, pH-responsive nanocarriers have been developed to target drugs either to the slightly acidic extracellular fluids of tumor tissue or, after endocytosis, to the endosomes or lysosomes within cancer cells. These systems can release the drug by specific processes after accumulation in tumor tissues via the enhanced permeability and retention (EPR) effect or they can release the drugs in endosomes or lysosomes by pH-controlled hydrolysis after they are taken up by the cell via the endocytic pathway. This strategy facilitates the specific delivery of the drug while reducing systemic side-effects with high potential for improving the efficacy of cancer chemotherapy.

The reaction of cyanoacetylhydrazine with omega-bromo(4-methyl)acetophenone: synthesis of heterocyclic derivatives with antitumor activity

New approaches for the synthesis of hydrazide-hydrazone derivatives were demonstrated as well as some heterocyclizations of such derivatives to afford 1,3,4-triazine, pyridine and 1,3,4-oxadiazine derivatives. The antitumor evaluation of the newly synthesized products against three cancer cell lines, namely breast adenocarcinoma (MCF-7), non-small cell lung cancer (NCI-H460) and CNS cancer (SF-268) were recorded. Most of the synthesized compounds showed high inhibitory effects.

Polymeric micelles for the pH-dependent controlled, continuous low dose release of paclitaxel

Poly(ethylene glycol)-block-poly(aspartate-hydrazide) (PEG-p(Asp-Hyd)) was modified using either levulinic acid (LEV) or 4-acetyl benzoic acid (4AB) attached via hydrazone bonds. Paclitaxel (PTX) conjugated to the linkers formed PEG-p(Asp-Hyd-LEV-PTX) and PEG-p(Asp-Hyd-4AB-PTX). PEG-p(Asp-Hyd-LEV-PTX) and PEG-p(Asp-Hyd-4AB-PTX) assemble into unimodal polymeric micelles with diameters of 42 nm and 137 nm, respectively. PEG-p(Asp-Hyd-LEV-PTX) and PEG-p(Asp-Hyd-4AB-PTX) at a 1:1 and 1:5 molar ratio assemble into unimodal mixed polymeric micelles with diameters of 85 and 113 nm, respectively. PEG-p(Asp-Hyd-LEV-PTX) micelles release LEV-PTX faster at pH 5.0 than at pH 7.4 over 24 h. At pH 7.4 mixed polymeric micelles at 1:5 ratio show no difference in LEV-PTX release from PEG-p(Asp-Hyd-LEV-PTX) micelles. Mixed polymeric micelles at 1:5 molar ratio gradually release LEV-PTX at pH 5.0, with no release of 4AB-PTX. PEG-p(Asp-Hyd-LEV-PTX) micelles and mixed polymeric micelles exert comparable cytotoxicity against SK-OV-3 and MCF-7 cancer cell lines. In summary, mixed polymeric micelles based on PEG-p(Asp-Hyd-LEV-PTX) and PEG-p(Asp-Hyd-4AB-PTX) offer prospects for pH-dependent release of PTX, offering a novel prodrug strategy for adjusting its pharmacokinetic and pharmacodynamic properties for cancer therapy. If successful this delivery system offers an alternative new mode of delivery for paclitaxel with a new scope for its efficacy along with a minimal synthetic framework needed to accomplish this.

A multivalent approach to drug discovery for novel antibiotics

The design, synthesis and antibacterial activity of novel glycopeptide/beta-lactam heterodimers is reported. Employing a multivalent approach to drug discovery, vancomycin and cephalosporin synthons, A and B respectively, were chemically linked to yield heterodimer antibiotics. These novel compounds were designed to inhibit Gram-positive bacterial cell wall biosynthesis by simultaneously targeting the principal cellular targets of both glycopeptides and beta-lactams. The antibiotics 8a-f displayed remarkable potency against a wide range of Gram-positive organisms including methicillin-resistant Staphylococcus aureus (MRSA). Compound 8e demonstrated excellent bactericidal activity against MRSA (ATCC 33591) and initial evidence supports a multivalent mechanism of action for this important new class of antibiotic.

Exploring the positional attachment of glycopeptide/beta-lactam heterodimers

Further investigations towards novel glycopeptide/beta-lactam heterodimers are reported. Employing a multivalent approach to drug discovery, vancomycin and cephalosporin synthons, 4, 2, 5 and 10, 18, 25 respectively, were chemically linked to yield heterodimer antibiotics. These novel compounds were designed to inhibit Gram-positive bacterial cell wall biosynthesis by simultaneously targeting the principal cellular targets of both glycopeptides and beta-lactams. The positional attachment of both the vancomycin and the cephalosporin central cores has been explored and the SAR is reported. This novel class of bifunctional antibiotics 28-36 all displayed remarkable potency against a wide range of Gram-positive organisms, including methicillin-resistant Staphylococcus aureus (MRSA). A subset of compounds, 29, 31 and 35 demonstrated excellent bactericidal activity against MRSA (ATCC 33591) and 31 and 35 also exhibited superb in vivo efficacy in a mouse model of MRSA infection. As a result of this work compound 35 was selected as a clinical candidate, TD-1792.

Design, synthesis and applications of hyaluronic acid-paclitaxel bioconjugates

Paclitaxel (1a), a well known antitumor agent adopted mainly for the treatment of breast and ovarian cancer, suffers from significant disadvantages such as low solubility, certain toxicity and specific drug-resistance of some tumor cells. To overcome these problems extensive research has been carried out. Among the various proposed strategies, the conjugation of paclitaxel (1a) to a biocompatible polymer, such as hyaluronic acid (HA, 2), has also been considered. Coupling a bioactive compound to a biocompatible polymer offers, in general, many advantages such as better drug solubilization, better stabilization, specific localization and controlled release. Hereafter the design, synthesis and applications of hyaluronic acid-paclitaxel bioconjugates are reviewed. An overview of HA-paclitaxel combinations is also given.

Polycefin, a new prototype of a multifunctional nanoconjugate based on poly(beta-L-malic acid) for drug delivery

A new prototype of nanoconjugate, Polycefin, was synthesized for targeted delivery of antisense oligonucleotides and monoclonal antibodies to brain tumors. The macromolecular carrier contains: 1. biodegradable, nonimmunogenic, nontoxic beta-poly(L-malic acid) of microbial origin; 2. Morpholino antisense oligonucleotides targeting laminin alpha4 and beta1 chains of laminin-8, which is specifically overexpressed in glial brain tumors; 3. monoclonal anti-transferrin receptor antibody for specific tissue targeting; 4. oligonucleotide releasing disulfide units; 5. L-valine containing, pH-sensitive membrane disrupting unit(s), 6. protective poly(ethylene glycol); 7. a fluorescent dye (optional). Highly purified modules were conjugated directly with N-hydroxysuccinimidyl ester-activated beta-poly(L-malic acid) at pendant carboxyl groups or at thiol containing spacers via thioether and disulfide bonds. Products were chemically validated by physical, chemical, and functional tests. In vitro experiments using two human glioma cell lines U87MG and T98G demonstrated that Polycefin was delivered into the tumor cells by a receptor-mediated endocytosis mechanism and was able to inhibit the synthesis of laminin-8 alpha4 and beta1 chains at the same time. Inhibition of laminin-8 expression was in agreement with the designed endosomal membrane disruption and drug releasing activity. In vivo imaging showed the accumulation of intravenously injected Polycefin in brain tumor tissue via the antibody-targeted transferrin receptor-mediated endosomal pathway in addition to a less efficient mechanism known for high molecular mass biopolymers as enhanced permeability and retention effect. Polycefin was nontoxic to normal and tumor astrocytes in a wide range of concentrations, accumulated in brain tumor, and could be used for specific targeting of several biomarkers simultaneously.

Correlation of the acid-sensitivity of polyethylene glycol daunorubicin conjugates with their in vitro antiproliferative activity

Polyethylene glycol conjugates with linkers of varying acid-sensitivity were prepared by reacting five maleimide derivatives of daunorubicin containing an amide bond (1) or acid-sensitive carboxylic hydrazone bonds (2-5) with alpha-methoxy-poly(ethylene glycol)-thiopropionic acid amide (MW 20000) or alpha,omega-bis-thiopropionic acid amide poly(ethylene glycol) (MW 20000). The polymer drug derivatives were designed to release daunorubicin inside the tumor cell by acid-cleavage of the hydrazone bond after uptake of the conjugate by endocytosis. In subsequent cell culture experiments, the order of antitumor activity of the PEG daunorubicin conjugates correlated with their acid-sensitivity as determined by HPLC (cell lines: BXF T24 bladder carcinoma and LXFL 529L lung cancer cell line; assay: propidium iodide fluorescence assay). The acid-sensitivity of the link between PEG and daunorubicin is therefore an important parameter for in vitro efficacy.

Pharmacokinetics and biodistribution of polymeric micelles of paclitaxel with Pluronic P123

AIM

To investigate the preparation, in vitro release, in vivo pharmacokinetics and tissue distribution of a novel polymeric micellar formulation of paclitaxel (PTX) with Pluronic P123.

METHODS

The polymeric micelles of paclitaxel with Pluronic P123 were prepared by a solid dispersion method. The characteristics of micelles including particle size distribution, morphology and in vitro release of PTX from micelles were carried out. PTX-loaded micellar solutions were administered through the tail vein to healthy Sprague-Dawley rats and Kunming strain mice to assess the pharmacokinetics and tissue distribution of PTX, respectively. Taxol, the commercially available intravenous formulation of PTX, was also administered as control.

RESULTS

By using a dynamic light scattering sizer and a transmission electron microscopy, it was shown that the PTX-loaded micelles had a mean size of approximately 25 nm with narrow size distribution and a spherical shape. PTX was continuously released from Pluronic P123 micelles in release medium containing 1 mol/L sodium salicylate for 24 h at 37 centigrade degree. In the pharmacokinetic assessment, t(1/2beta) and AUC of micelle formulation were 2.3 and 2.9-fold higher than that of Taxol injection. And the PTX-loaded micelles increased the uptake of PTX in the plasma, ovary and uterus, lung, and kidney, but decreased uptake in the liver and brain in the biodistribution study.

CONCLUSION

Polymeric micelles using Pluronic P123 can effectively solubilize PTX, prolong blood circulation time and modify the biodistribution of PTX.

Release from polymeric prodrugs: linkages and their degradation

Polymeric prodrugs have evolved into a very useful class of drug delivery agents. Numerous polymeric prodrugs have been prepared for applications ranging from passive drug targeting to controlled release. The mechanistic aspects of the release processes, however, have not been clearly delineated. This review highlights the salient features of the chemical reactions that are responsible for drug release from these systems. The mechanisms of release from polymeric prodrugs employing various chemical linkages, esters, carbonates, carbamates, C=N linkage and amides, are discussed.

A Folate Receptor?Targeted Lipid Nanoparticle Formulation for a Lipophilic Paclitaxel Prodrug

PURPOSE

The anticancer drug paclitaxel has poor aqueous solubility and is difficult to formulate in a lipid-based formulation due to its limited lipid solubility. Paclitaxel-7-carbonyl-cholesterol (Tax-Chol), a prodrug of paclitaxel with increased lipophilicity, was therefore synthesized and evaluated for incorporation into a lipid nanoparticle (LN) formulation, which also contained folate-polyethylene glycolcholesterol (f-PEG-Chol) as a ligand that targets the tumor marker folate receptor (FR). This novel formulation was designed for prolonged systemic circulation and selective targeting of tumor cells with amplified FR expression.

METHODS

Tax-Chol was synthesized. FR-targeted LNs, composed of distearoyl phosphatidylcholine (DSPC)/triolein/Chol oleate/PEG-Chol/f-PEG-Chol (40:40:18:2.0:0.5, mole/mole), were then prepared by solvent dilution followed by diafiltration. FR-targeted LNs containing Tax-Chol were then evaluated for cytotoxicity in KB, a human oral carcinoma cell line, and M109, a murine lung carcinoma cell line, both of which are FR(+) and in FR(-) Chinese hamster ovary (CHO) cells. Furthermore, tumor growth inhibition and animal survival in response to treatment with FR-targeted LNs and control formulations were evaluated in BALB/c mice bearing subcutaneously engrafted M109 tumors.

RESULTS

The LNs had a mean diameter of 130 nm and Tax-Chol incoporation efficiency of greater than 90% and exhibited excellent colloidal stability. FR-targeted LNs showed greater uptake and cytotoxicity in FR(+) KB and M109 cells than nontargeted LNs. Furthermore, treatment of mice bearing M109 tumors with FR-targeted LNs resulted in significantly greater tumor growth inhibition and animal survival compared to treatment with nontargeted LNs or paclitaxel formulated in Cremophor EL.

CONCLUSION

FR-targeted LNs containing Tax-Chol are a promising novel formulation for the treatment of FR(+) tumors and further preclinical studies are warranted.