Preclinical efficacy studies of a novel nanoparticle-based formulation of paclitaxel that out-performs Abraxane

Recent Advances in Ovarian Cancer: Therapeutic Strategies, Potential Biomarkers, and Technological Improvements

Aggressive and recurrent gynecological cancers are associated with worse prognosis and a lack of effective therapeutic response. Ovarian cancer (OC) patients are often diagnosed in advanced stages, when drug resistance, angiogenesis, relapse, and metastasis impact survival outcomes. Currently, surgical debulking, radiotherapy, and/or chemotherapy remain the mainstream treatment modalities; however, patients suffer unwanted side effects and drug resistance in the absence of targeted therapies. Hence, it is urgent to decipher the complex disease biology and identify potential biomarkers, which could greatly contribute to making an early diagnosis or predicting the response to specific therapies. This review aims to critically discuss the current therapeutic strategies for OC, novel drug-delivery systems, and potential biomarkers in the context of genetics and molecular research. It emphasizes how the understanding of disease biology is related to the advancement of technology, enabling the exploration of novel biomarkers that may be able to provide more accurate diagnosis and prognosis, which would effectively translate into targeted therapies, ultimately improving patients’ overall survival and quality of life.

Synthesis of Triazine based Dendrimers: A Mini-Review

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Synthesizing s-triazine dendrimers are interesting as they can be synthesized easily, contain diversity in composition, and have a basic potential for molecular recognition. Triazine trichloride is the molecule of choice for synthesizing a novel class of dendrimers as it possesses certain remarkable characteristics like the potential to expand the chemical functionality by nucleophilic aromatic substitution reactions at various temperatures to give the desired dendrimer.

Establishment and characterization of lung co-culture spheroids for paclitaxel loaded Eudragit® RL 100 nanoparticle evaluation

3D cell cultures are regarded as a better and more relevant approach for screening drugs and therapeutics, particularly due to their likeness with the in vivo conditions. Spheroids offer an intermediate platform between in vitro and in vivo models, for conducting tumor-based investigations. In this study, a simple setup was developed for consistent generation of lung co-culture spheroids, which were developed using the cancer cell lines A549, NCI H460, and fibroblast cells WI-38. The potential of these spheroids for evaluating the toxicity of Eudragit® RL 100 nanoparticles (ENP) was explored. Monodisperse ENP, having the size range of 140-200 nm was prepared using the nanoprecipitation method. These were loaded with the poorly water-soluble anticancer drug paclitaxel. The evaluation of toxicity and uptake of drug-loaded ENP revealed that 2D monolayers were more sensitive to treatment than 3D spheroids. Within spheroids, co-cultures were more resistant to the treatment than monocultures. Overall, our findings demonstrated that the lung co-culture spheroids were a suitable model for accelerating the efficacy and toxicity-related investigations of novel drug delivery systems.

Animal Models for the Evaluation of Theranostic Radiopharmaceuticals

BACKGROUND

Theranostic is a new field of medicine that combines diagnosis and patient- specific targeted treatment. In the theranostic approach, it is aimed to detect diseased cells by using targeted molecules using disease-specific biological pathways and then destroy them by cellular irradiation without damaging other tissues. Diagnostic tests guide the use of specific therapeutic agents by demonstrating the presence of the receptor/molecule on the target tissue. As the therapeutic agent is administered to patients who have a positive diagnostic test, the efficacy of treatment in these patients is largely guaranteed. As therapeutic efficacy can be predicted by therapeutic agents, it is also possible to monitor the response to treatment. Many diagnostic and therapeutic procedures in nuclear medicine are classified as theranostic. ¹³¹I treatment and scintigraphy are the best examples of the theranostic application. Likewise, ¹⁷⁷Lu / ⁹⁰Y octreotate for neuroendocrine tumors, ¹⁷⁷Lu PSMA for metastatic or treatment-resistant prostate cancer, ⁹⁰Y SIRT for metastatic liver cancer, and ²²³Ra for bone metastasis of prostate cancer are widely used. Moreover, nanoparticles are one of the most rapidly developing subjects of theranostics. Diagnostic and therapeutic agents that show fluorescent, ultrasonic, magnetic, radioactive, contrast, pharmacological drug or antibody properties are loaded into the nanoparticle to provide theranostic use.

METHODS

This article reviewed general aspects of preclinical models for theranostic research, and presented examples from the literature.

CONCLUSION

To achieve successful results in rapidly accelerating personalized treatment research of today, the first step is to conduct appropriate preclinical studies.

Genetically Encoded Stealth Nanoparticles of a Zwitterionic Polypeptide-Paclitaxel Conjugate Have a Wider Therapeutic Window than Abraxane in Multiple Tumor Models

Small-molecule therapeutics demonstrate suboptimal pharmacokinetics and bioavailability due to their hydrophobicity and size. One way to overcome these limitations-and improve their efficacy-is to use "stealth" macromolecular carriers that evade uptake by the reticuloendothelial system. Although unstructured polypeptides are of increasing interest as macromolecular drug carriers, current recombinant polypeptides in the clinical pipeline typically lack stealth properties. We address this challenge by developing new unstructured polypeptides, called zwitterionic polypeptides (ZIPPs), that exhibit "stealth" behavior in vivo. We show that conjugating paclitaxel to a ZIPP imparts amphiphilicity to the polypeptide chain that is sufficient to drive its self-assembly into micelles. This in turn increases the half-life of paclitaxel by 17-fold compared to free paclitaxel, and by 1.6-fold compared to the nonstealth control, i.e., ELP-paclitaxel. Treatment of mice bearing highly aggressive prostate or colon cancer with a single dose of ZIPP-paclitaxel nanoparticles leads to near-complete eradication of the tumor, and these nanoparticles have a wider therapeutic window than Abraxane, an FDA-approved taxane nanoformulation.

Nanoscale drug delivery strategies for therapy of ovarian cancer: conventional vs targeted

Ovarian cancer is the second most common gynaecological malignancy. It usually occurs in women older than 50 years, and because 75% of cases are diagnosed at stage III or IV it is associated with poor diagnosis. Despite the chemosensitivity of intraperitoneal chemotherapy, the majority of patients is relapsed and eventually dies. In addition to the challenge of early detection, its treatment presents several challenges like the route of administration, resistance to therapy with recurrence and specific targeting of cancer to reduce cytotoxicity and side effects. In ovarian cancer therapy, nanocarriers help overcome problems of poor aqueous solubility of chemotherapeutic drugs and enhance their delivery to the tumour sites either by passive or active targeting, and thus reducing adverse side effects to the healthy tissues. Moreover, the bioavailability to the tumour site is increased by the enhanced permeability and retention (EPR) mechanism. The present review aims to describe the current conventional treatment with special reference to passively and actively targeted drug delivery systems (DDSs) towards specific receptors designed against ovarian cancer to overcome the drawbacks of conventional delivery. Conclusively, targeted nanocarriers would optimise the intra-tumour distribution, followed by drug delivery into the intracellular compartment. These features may contribute to greater therapeutic effect.

A Micelle Self-Assembled from Doxorubicin-Arabinoxylan Conjugates with pH-Cleavable Bond for Synergistic Antitumor Therapy

Nanomedicine offers new hope to overcome the low solubility and high side toxicity to normal tissue appeared in traditional chemotherapy. The biocompatibility and intracellular drug accumulation is still a big challenge for the nano-based formulations. Herein, a medical-used biocompatible arabinoxylan (AX) is used to develop to delivery chemodrug doxorubicin (DOX). The solubility of DOX is obviously enhanced via the hydrogen bond formed with AX which results in an amphiphilic AX-DOX. A micelle with pH-cleavable bond is thus self-assembled from such AX-DOX with DOX core and AX shell. The inner DOX can be easily released out at low intracellular pH, which obviously enhanced its in vitro cytotoxicity against breast cancer cells (MCF-7). Interestingly, an unexpected apoptosis is evoked except for the proliferation inhibition. Moreover, the therapeutic effects are further synergistically promoted by the enhanced permeability and retention (EPR) and intracellular pH-triggered drug release. Consequently, the in vivo intratumor accumulation of DOX, the tumor inhibition was significantly promoted after intravenous administration to the Balb/c nude mice bearing MCF-7 tumors. These in vitro/vivo results indicated that the AX-DOX micellular formulation holds high potential in cancer therapy.

Hydrotropic polymer-based paclitaxel-loaded self-assembled nanoparticles: preparation and biological evaluation

Hydrotropic polymer-based paclitaxel-loaded self-assembled nanoparticles: preparation and biological evaluation.

Developing Precisely Defined Drug-Loaded Nanoparticles by Ring-Opening Polymerization of a Paclitaxel Prodrug

Nanoparticles with high paclitaxel (PTX) loading and low systemic toxicity are prepared in scalable and versatile manner via one-step ring-opening polymerization of a prodrug monomer consisting of PTX that is appended to a cyclic carbonate through a hydrolysable ester linker. Initiating this monomer from a hydrophilic macroinitiator results in an amphiphilic diblock copolymer that spontaneously self-assembles into well-defined nanoparticles with tunable size.

Poly (l-γ-glutamylglutamine) Polymer Enhances Doxorubicin Accumulation in Multidrug Resistant Breast Cancer Cells

Background: Drug resistance is one of the bottlenecks of cancer chemotherapy in the clinic. Polymeric nanomedicine is one of the most promising strategies for overcoming poor chemotherapy responses due to the multidrug resistance (MDR). Methods: In this study, a new polymer-based drug delivery system, poly (l-γ-glutamylglutamine)-doxorubicin (PGG-Dox) conjugate, was studied in both drug-induced resistant human breast cancer MDA-MB-231/MDR cells and their parent human breast cancer MDA-MB-231 cells. The effect of PGG on facilitating the growth inhibition of Dox against multidrug resistant cells were investigated by evaluating the cytotoxicity of PGG-Dox conjugate, PGG/Dox unconjugated complex and free Dox on both cells. The underlying mechanisms in resistant cells were further studied via the intracellular traffic studies. Results: Both conjugated and unconjugated PGG significantly increased Dox uptake, prolonged Dox retention and reduced Dox efflux in the MDA-MB-231/MDR cells. The PGG-Dox conjugate is taken up by tumor cells mainly by pinocytosis pathway, in which PGG-Dox conjugate-containing vesicles are formed and enter the cells. Conclusions: This study indicated that both polymer-drug conjugate and unconjugated complex are promising strategies of overcoming resistance of anti-tumor drugs.

Nanotechnology-based strategies for combating toxicity and resistance in melanoma therapy

Drug toxicity and resistance remain formidable challenges in cancer treatment and represent an area of increasing attention in the case of melanoma. Nanotechnology represents a paradigm-shifting field with the potential to mitigate drug resistance while improving drug delivery and minimizing toxicity. Recent clinical and pre-clinical studies have demonstrated how a diverse array of nanoparticles may be harnessed to circumvent known mechanisms of drug resistance in melanoma to improve therapeutic efficacy. In this review, we discuss known mechanisms of resistance to various melanoma therapies and possible nanotechnology-based strategies that could be used to overcome these barriers and improve the pharmacologic arsenal available to combat advanced stage melanoma.

pH-Sensitive Biocompatible Nanoparticles of Paclitaxel-Conjugated Poly(styrene-co-maleic acid) for Anticancer Drug Delivery in Solid Tumors of Syngeneic Mice

In the present study, we have synthesized poly(styrene-co-maleic anhydride), a biocompatible copolymer that was further conjugated with paclitaxel (PTX) via ester linkage and self-assembled to form poly(styrene-co-maleic acid)-paclitaxel (PSMAC-PTX) nanoparticles (NPs). The in vitro release of PTX from PSMAC-PTX NPs showed a higher release at lower pH than at the physiological pH of 7.4, confirming its pH-dependent release. The cell viability of PSMAC-PTX nanoparticles was evaluated using MTT assay. IC50 values of 9.05-18.43 ng/mL of PTX equivalent were observed in various cancer cell lines after 72 h of incubation. Confocal microscopy, Western blotting, and Flow cytometry results further supported that the cellular uptake and apoptosis of cancer cells with PSMAC-PTX NPs. Pharmacokinetic studies revealed that the conjugation of PTX to the PSMAC co-polymer not only increased the plasma and tumor C(max) of PTX but also prolonged its plasma half-life and retention in tumor via enhanced permeability and retention (EPR) effect. Administration of PSMAC-PTX NPs showed significant tumor growth inhibition with improved apoptosis effects in vivo on Ehrlich Ascites Tumor (EAT)-bearing BALB/c syngeneic mice in comparison with Taxol, without showing any cytotoxicity. On the basis of preliminary results, no subacute toxicity was observed in major organs, tissues and hematological system up to a dosage of 60 mg/kg body weight in mice. Therefore, PSMAC-PTX NPs may be considered as an alternative nanodrug delivery system for the delivery of PTX in solid tumors.

Preclinical Murine Models for Lung Cancer: Clinical Trial Applications

Murine models for the study of lung cancer have historically been the backbone of preliminary preclinical data to support early human clinical trials. However, the availability of multiple experimental systems leads to debate concerning which model, if any, is best suited for a particular therapeutic strategy. It is imperative that these models accurately predict clinical benefit of therapy. This review provides an overview of the current murine models used to study lung cancer and the advantages and limitations of each model, as well as a retrospective evaluation of the uses of each model with respect to accuracy in predicting clinical benefit of therapy. A better understanding of murine models and their uses, as well as their limitations may aid future research concerning the development and implementation of new targeted therapies and chemotherapeutic agents for lung cancer.

Targeted poly (L-γ-glutamyl glutamine) nanoparticles of docetaxel against folate over-expressed breast cancer cells

A novel folate (FA) conjugated poly(l-γ-glutamyl glutamine) (PGG) nanoparticle loaded with docetaxel (DTX) was prepared to take advantage of both targeted drug delivery in breast cancer and reducing the overall side effects due to the adjuvant free formulation in comparison with Taxotere(®). Nanoprecipitation method was employed to prepare nanoparticles (NPs). The chemical structure of PGG synthesized polymers and PGG-FA conjugates and polymeric nanoparticles were characterized by H NMR, FTIR spectroscopy, field emission scanning electron microscopy, and laser scanning confocal microscopy. The average size of optimized nanoparticles with the aid of Box-Behnken experimental design was 131.96 ± 5.34(nm) with polydispersity of 0.089 ± 0.019, zeta potential of -25.8 ± 2.21(mV), and entrapment efficiency of 67.83 ± 3.29(%). In vitro cytotoxicity of the designed NPs was investigated by MTT assay against three chosen cell lines of MCF7, 4T1, and A549 based on their folate receptor expression capacity and was compared with Taxotere(®). Moreover, PGG-FOL NPs were loaded with 6-coumarin for cellular uptake investigation. In order to assess the antitumor efficacy and biodistribution of targeted NPs, 4T1 murine breast tumors were established on the balb/c mice and in vivo studies were performed. The obtained results showed that the novel designed system was highly effective against tumor cells and successfully localized in the tumor site.

Nano polymeric carrier fabrication technologies for advanced antitumor therapy

Comparing with the traditional therapeutic methods, newly developed cancer therapy based on the nanoparticulates attracted extensively interest due to its unique advantages. However, there are still some drawbacks such as the unfavorable in vivo performance for nanomedicine and undesirable tumor escape from the immunotherapy. While as we know that the in vivo performance strongly depended on the nanocarrier structural properties, thus, the big gap between in vitro and in vivo can be overcome by nanocarrier's structural tailoring by fine chemical design and microstructural tuning. In addition, this fine nanocarrier's engineering can also provide practical solution to solve the problems in traditional cancer immunotherapy. In this paper, we review the latest development in nanomedicine, cancer therapy, and nanoimmunotherapy. We then give an explanation why fine nanocanrrie's engineering with special focus on the unique pathology of tumor microenvironments and properties of immunocells can obviously promote the in vivo performance and improve the therapeutic index of nanoimmunotherapy.

Applications of nanotechnology for melanoma treatment, diagnosis, and theranostics

Melanoma is the most aggressive type of skin cancer and has very high rates of mortality. An early stage melanoma can be surgically removed, with a survival rate of 99%. However, metastasized melanoma is difficult to cure. The 5-year survival rates for patients with metastasized melanoma are still below 20%. Metastasized melanoma is currently treated by chemotherapy, targeted therapy, immunotherapy and radiotherapy. The outcome of most of the current therapies is far from optimistic. Although melanoma patients with a mutation in the oncogene v-Raf murine sarcoma viral oncogene homolog B1 (BRAF) have an initially higher positive response rate to targeted therapy, the majority develop acquired drug resistance after 6 months of the therapy. To increase treatment efficacy, early diagnosis, more potent pharmacological agents, and more effective delivery systems are urgently needed. Nanotechnology has been extensively studied for melanoma treatment and diagnosis, to decrease drug resistance, increase therapeutic efficacy, and reduce side effects. In this review, we summarize the recent progress on the development of various nanoparticles for melanoma treatment and diagnosis. Several common nanoparticles, including liposome, polymersomes, dendrimers, carbon-based nanoparticles, and human albumin, have been used to deliver chemotherapeutic agents, and small interfering ribonucleic acids (siRNAs) against signaling molecules have also been tested for the treatment of melanoma. Indeed, several nanoparticle-delivered drugs have been approved by the US Food and Drug Administration and are currently in clinical trials. The application of nanoparticles could produce side effects, which will need to be reduced so that nanoparticle-delivered drugs can be safely applied in the clinical setting.

In vitro activity of Paclitaxel-loaded polymeric expansile nanoparticles in breast cancer cells

Through a series of in vitro studies, the essential steps for intracellular drug delivery of paclitaxel using a pH-responsive nanoparticle system have been investigated in breast cancer cells. We successfully encapsulated paclitaxel within polymeric expansile nanoparticles (Pax-eNPs) at 5% loading via a miniemulsion polymerization procedure. Fluorescently tagged eNPs were readily taken up by MDA-MB-231 breast cancer cells grown in culture as confirmed by confocal microscopy and flow cytometry. The ability of the encapsulated paclitaxel to reach the cytoplasm was also observed using confocal microscopy and fluorescently labeled paclitaxel. Pax-eNPs were shown to be efficacious against three in vitro human breast adenocarcinoma cell lines (MDA-MB-231, MCF-7, and SK-BR-3) as well as cells isolated from the pleural effusions of two different breast cancer patients. Lastly, macropinocytosis was identified as the major cellular pathway responsible for eNP uptake, as confirmed using temperature-sensitive metabolic reduction, pharmacologic inhibitors, and fluid-phase marker colocalization.

Paclitaxel Nano-Delivery Systems: A Comprehensive Review

Paclitaxel is one of the most effective chemotherapeutic drugs ever developed and is active against a broad range of cancers, such as lung, ovarian, and breast cancers. Due to its low water solubility, paclitaxel is formulated in a mixture of Cremophor EL and dehydrated ethanol (50:50, v/v) a combination known as Taxol. However, Taxol has some severe side effects related to Cremophor EL and ethanol. Therefore, there is an urgent need for the development of alternative Taxol formulations. The encapsulation of paclitaxel in biodegradable and non-toxic nano-delivery systems can protect the drug from degradation during circulation and in-turn protect the body from toxic side effects of the drug thereby lowering its toxicity, increasing its circulation half-life, exhibiting improved pharmacokinetic profiles, and demonstrating better patient compliance. Also, nanoparticle-based delivery systems can take advantage of the enhanced permeability and retention (EPR) effect for passive tumor targeting, therefore, they are promising carriers to improve the therapeutic index and decrease the side effects of paclitaxel. To date, paclitaxel albumin-bound nanoparticles (Abraxane®) have been approved by the FDA for the treatment of metastatic breast cancer and non-small cell lung cancer (NSCLC). In addition, there are a number of novel paclitaxel nanoparticle formulations in clinical trials. In this comprehensive review, several types of developed paclitaxel nano-delivery systems will be covered and discussed, such as polymeric nanoparticles, lipid-based formulations, polymer conjugates, inorganic nanoparticles, carbon nanotubes, nanocrystals, and cyclodextrin nanoparticles.

Challenges and opportunities in the advancement of nanomedicines

Nanomedicine-based approaches to cancer treatment face several challenges that differ from those encountered by conventional medicines during clinical development. A systematic exploration of these issues has led us to identify the following needs and opportunities for further development: (1) robust and general methods for the accurate characterization of nanoparticle size, shape, and composition; (2) scalable approaches for producing nanomedicines with optimized bioavailability and excretion profiles; (3) particle engineering for maintaining low levels of nonspecific cytotoxicity and sufficient stability during storage; (4) optimization of surface chemistries for maximum targeted delivery and minimum nonspecific adsorption; (5) practical methods for quantifying ligand density and distributions on multivalent nanocarriers; and (6) the design of multifunctional nanomedicines for novel combination therapies with supportable levels of bioaccumulation.

Triazine dendrimers as drug delivery systems: from synthesis to therapy

The use of triazine dendrimers as drug delivery systems benefits from their synthetic versatility and well-defined structure. Triazine dendrimers can be designed and readily synthesized to display orthogonally functional surfaces that facilitate post-synthetic manipulation such as attachment of drug, PEGylation, and/or the installation of ligands or reporting groups. The synthesis is scalable, and large generations can be accessed. To date, triazine dendrimers have been probed for a variety of medicinal applications including drug delivery with an emphasis on cancer, nonviral DNA and RNA delivery systems, in sensing applications, and as bioactive materials. Specifically, triazine adducts with paclitaxel, camptothecin, brefeldin A, and desferrioxamine have been prepared and assessed. Paclitaxel constructs show promising activity in vivo. The use of these materials in fluorescence-based glucose sensors is being pursued. Glycosylated triazine dendrimers interfere with signal transduction in the Toll-4 receptor pathway.

Synthesis, characterization, and in vivo efficacy evaluation of PGG-docetaxel conjugate for potential cancer chemotherapy

Aim

This work is intended to develop and evaluate a biopolymeric poly(L-γ-glutamylglutamine) (PGG)–docetaxel (DTX) conjugate that can spontaneously self-assemble in aqueous solutions to become nanoparticles.

Methods

DTX was covalently attached to hydrophilic PGG by direct esterification, and the conjugate was characterized by proton nuclear magnetic resonance spectroscopy, molecular weight gel permeation chromatography, solubility, size distribution and morphology, and hemolysis. Conjugated DTX was found to have 2000 times improved water solubility compared with free DTX. Dynamic light scattering, transmission electron microscopy, and atomic force microscopy revealed the particle size, distribution and morphology of the PGG–DTX conjugate. In addition, the conjugate was further tested for in vitro cytotoxicity and in vivo antitumor efficacy on the human non-small cell lung cancer cell line NCI-H460.

Results

Conjugated DTX was found to have 2000 times improved water solubility compared with free DTX. The conjugate formed nanoparticles with an average diameter of 30 nm in spherical shape and unimodal particle size distribution. The conjugate exhibited about 2% hemolysis at 10 mg/mL, compared with 56% for Tween 80^® at 0.4 mg/mL, and 33% for Cremophor EL^® at 10 mg/mL. In addition, the conjugate was further tested for in vitro cytotoxicity and in vivo antitumor efficacy on the human non-small cell lung cancer cell line NCI-H460. As expected, conjugated DTX exhibited lower cytotoxicity compared to that of free DTX, in concentration-dependent manner. However, PGG–DTX showed better antitumor activity in NCI-H460 lung cancer-bearing mice with minimal weight loss compared to that of free DTX.

Conclusion

The PGG–DTX conjugate may be considered as an attractive and promising polymeric DTX conjugate for non-small cell lung cancer treatment.

Antitumor activity and molecular dynamics simulations of paclitaxel-laden triazine dendrimers

The antitumor activities of triazine dendrimers bearing paclitaxel, a well-known mitotic inhibitor, are evaluated in SCID mice bearing human prostate cancer xenografts. To increase the activity of a first generation prodrug 1 that contained twelve paclitaxel molecules tethered via an ester linkage, the new construct described here, prodrug 2, tethers paclitaxel with linkers containing both an ester and disulfide. While PEGylation is necessary for solubility, and may improve biocompatibility and increase plasma half-life, it increases the heterogeneity of the sample with an average of eight to nine PEG chains (2 kDa each) incorporated. The heterogeneous population of PEGylated materials was used without fractionation based on models obtained from molecular dynamics simulations. Three models were examined; hexaPEGylated, nonaPEGylated, and dodecaPEGylated constructs. Intravenous delivery of prodrug 2 was performed by single, double or triple dosing regimes with doses spaced by one week. The doses varied from 50 mg of paclitaxel/kg to 200 mg of paclitaxel/kg. Tumor growth arrest and regression was observed over the 10-week treatment period without mortality for mice treated with the 50 mg of paclitaxel/kg treated three times.

Physicochemical properties and biocompatibility of a polymer-paclitaxel conjugate for cancer treatment

Background

Poly(L-γ-glutamylglutamine) paclitaxel (PGG-PTX) conjugate is a non-diblock polymeric drug nanoparticle intended to improve the therapeutic index of paclitaxel. The purpose of the present study was to elucidate further the physicochemical properties of PGG-PTX in order to proceed with its clinical development.

Methods and results

PGG-PTX was designed by integration of a hydrophobic paclitaxel conjugate through an added hydrophilic glutamic acid onto poly(L-glutamic acid). The addition of a flexible glutamic linker between PGA and paclitaxel resulted in spontaneous self-assembly of a PGG-PTX conjugate into nanoparticles. The PGG-PTX conjugate was stable as a lyophilized solid form. An in vitro viability experiment showed that PGG-PTX was effective after a longer incubation period, the same trend as Taxol. In vitro studies using NCI-H460 and B16F0 cancer cells demonstrated significantly high cellular uptake after 30 minutes of incubation. The in vivo biocompatibility of PGG-PTX conjugate was evaluated in the NCI-H460 tumor model, the assessment of tissue seemed to be normal after 21 days of treatment.

Conclusion

These results are encouraging for further development of non-block polymeric paclitaxel nanoparticles for treatment of cancer.

Novel free paclitaxel-loaded poly(L-γ-glutamylglutamine)-paclitaxel nanoparticles

The purpose of this study was to develop a novel formulation of paclitaxel (PTX) that would improve its therapeutic index. Here, we combined a concept of polymer–PTX drug conjugate with a concept of polymeric micelle drug delivery to form novel free PTX-loaded poly(L-γ-glutamylglutamine) (PGG)–PTX conjugate nanoparticles. The significance of this drug formulation emphasizes the simplicity, novelty, and flexibility of the method of forming nanoparticles that contain free PTX and conjugated PTX in the same drug delivery system. The results of effectively inhibiting tumor growth in mouse models demonstrated the feasibility of the nanoparticle formulation. The versatility and potential of this dual PTX drug delivery system can be explored with different drugs for different indications. Novel and simple formulations of PTX-loaded PGG–PTX nanoparticles could have important implications in translational medicines.

Clinically relevant anticancer polymer Paclitaxel therapeutics

The concept of utilizing polymers in drug delivery has been extensively explored for improving the therapeutic index of small molecule drugs. In general, polymers can be used as polymer-drug conjugates or polymeric micelles. Each unique application mandates its own chemistry and controlled release of active drugs. Each polymer exhibits its own intrinsic issues providing the advantage of flexibility. However, none have as yet been approved by the U.S. Food and Drug Administration. General aspects of polymer and nano-particle therapeutics have been reviewed. Here we focus this review on specific clinically relevant anticancer polymer paclitaxel therapeutics. We emphasize their chemistry and formulation, in vitro activity on some human cancer cell lines, plasma pharmacokinetics and tumor accumulation, in vivo efficacy, and clinical outcomes. Furthermore, we include a short review of our recent developments of a novel poly(L-g-glutamylglutamine)-paclitaxel nano-conjugate (PGG-PTX). PGG-PTX has its own unique property of forming nano-particles. It has also been shown to possess a favorable profile of pharmacokinetics and to exhibit efficacious potency. This review might shed light on designing new and better polymer paclitaxel therapeutics for potential anticancer applications in the clinic.

Synthesis, characterization, and biological evaluation of poly(L-γ-glutamyl-glutamine)- paclitaxel nanoconjugate

The purpose of this study was to develop a novel, highly water-soluble poly(L-γ-glutamyl-glutamine)-paclitaxel nanoconjugate (PGG-PTX) that would improve the therapeutic index of paclitaxel (PTX). PGG-PTX is a modification of poly(L-glutamic acid)- paclitaxel conjugate (PGA-PTX) in which an additional glutamic acid has been added to each glutamic side chain in the polymer. PGG-PTX has higher water-solubility and faster dissolution than PGA-PTX. Unlike PGA-PTX, PGG-PTX self-assembles into nanoparticles, whose size remains in the range of 12-15 nm over the concentration range from 25 to 2,000 μg/mL in saline. Its critical micellar concentration in saline was found to be ~25 μg/mL. The potency of PGG-PTX when tested in vitro against the human lung cancer H460 cell line was comparable to other known polymer-PTX conjugates. However, PGG-PTX possesses lower toxicity compared with PGA-PTX in mice. The maximum tolerated dose of PGG-PTX was found to be 350 mg PTX/kg, which is 2.2-fold higher than the maximum tolerated dose of 160 mg PTX/kg reported for the PGA-PTX. This result indicates that PGG-PTX was substantially less toxic in vivo than PGA-PTX.

Biological assessment of triazine dendrimer: toxicological profiles, solution behavior, biodistribution, drug release and efficacy in a PEGylated, paclitaxel construct

The physicochemical characteristics, in vitro properties, and in vivo toxicity and efficacy of a third generation triazine dendrimer bearing approximately nine 2 kDa polyethylene glycol chains and twelve ester linked paclitaxel groups are reported. The hydrodynamic diameter of the neutral construct varies slightly with aqueous solvent ranging from 15.6 to 19.4 nm. Mass spectrometry and light scattering suggest radically different molecular weights with the former approximately 40 kDa mass consistent with expectation, and the latter 400 kDa mass consistent with a decameric structure and the observed hydrodynamic radii. HPLC can be used to assess purity as well as paclitaxel release, which is insignificant in organic solvents or aqueous solutions at neutral and low pH. Paclitaxel release occurs in vitro in human, rat, and mouse plasma and is nonlinear, ranging from 7 to 20% cumulative release over a 48 h incubation period. The construct is 2-3 orders of magnitude less toxic than Taxol by weight in human hepatocarcinoma (Hep G2), porcine renal proximal tubule (LLC-PK1), and human colon carcinoma (LS174T) cells, but shows similar cytotoxicity to Abraxane in LS174T cells. Both Taxol and the construct appear to induce caspase 3-dependent apoptosis. The construct shows a low level of endotoxin, is not hemolytic and does not induce platelet aggregation in vitro, but does appear to reduce collagen-induced platelet aggregation in vitro. Furthermore, the dendrimer formulation slightly activates the complement system in vitro due most likely to the presence of trace amounts (<1%) of free paclitaxel. An animal study provided insight into the maximum tolerated dose (MTD) wherein 10, 25, 50, and 100 mg of paclitaxel/kg of construct or Abraxane were administered once per week for three consecutive weeks to non tumor bearing athymic nude mice. The construct showed in vivo toxicity comparable to that of Abraxane. Both formulations were found to be nontoxic at the administered doses, and the dendrimer had an acute MTD greater than the highest dose administered. In a prostate tumor model (PC-3-h-luc), efficacy was observed over 70 days with an arrest of tumor growth and lack of luciferase activity observed in the twice treated cohort.