Aniruddha Roy

Factors controlling the pharmacokinetics, biodistribution and intratumoral penetration of nanoparticles.

Nanoparticle drug delivery to the tumor is impacted by multiple factors: nanoparticles must evade clearance by renal filtration and the reticuloendothelial system, extravasate through the enlarged endothelial gaps in tumors, penetrate through dense stroma in the tumor microenvironment to reach the tumor cells, remain in the tumor tissue for a prolonged period of time, and finally release the active agent to induce pharmacological effect. The physicochemical properties of nanoparticles such as size, shape, surface charge, surface chemistry (PEGylation, ligand conjugation) and composition affect the pharmacokinetics, biodistribution, intratumoral penetration and tumor bioavailability. On the other hand, tumor biology (blood flow, perfusion, permeability, interstitial fluid pressure and stroma content) and patient characteristics (age, gender, tumor type, tumor location, body composition and prior treatments) also have impact on drug delivery by nanoparticles. It is now believed that both nanoparticles and the tumor microenvironment have to be optimized or adjusted for optimal delivery. This review provides a comprehensive summary of how these nanoparticle and biological factors impact nanoparticle delivery to tumors, with discussion on how the tumor microenvironment can be adjusted and how patients can be stratified by imaging methods to receive the maximal benefit of nanomedicine. Perspectives and future directions are also provided.

Combined chemo-immunotherapy as a prospective strategy to combat cancer: a nanoparticle based approach.

The prime objective of this study was to develop a combined chemo-immunotherapeutic formulation which could directly kill cancer cells as well as activate the immunosuppressed tumor microenvironment to mount a robust antitumor immune response. Paclitaxel (PTX) and SP-LPS (nontoxic derivative of lipopolysaccharide) were selected as anticancer drug and immunostimulant respectively. Poly(lactic-co-glycolic acid) (PLGA) based PTX and SP-LPS containing nanoparticles (TLNP) were prepared by the double-emulsion method (w/o/w) and characterized in terms of size, zeta potential and transmission electron microscopy (TEM). The release behavior of PTX and SP-LPS from the TLNP exhibited a biphasic pattern characterized by an initial burst followed by slow continuous release. In vitro anticancer activity of TLNP was found to be higher compared to PTX when studied in a tumor cell-splenocyte coculture system. TLNP activated murine monocytes induced the secretion of various proinflammatory cytokines. After iv administration of TLNP in tumor bearing C57BL/6 mice, the amount of PTX in the tumor mass was found to be higher in TLNP treated mice as compared to commercial Taxol group at all time points studied. In vitro studies suggest that nanoparticles containing PTX and SP-LPS have both direct cytotoxicity and immunostimulatory activity. Hence this might have potential as a chemo-immunotherapeutic formulation against cancer with advantage over present day chemotherapy with Taxol, in terms of tumor targeting, less toxicity and immunostimulation.

Nanoparticle mediated co-delivery of paclitaxel and a TLR-4 agonist results in tumor regression and enhanced immune response in the tumor microenvironment of a mouse model.

Inefficiency of cancer chemotherapy to improve life expectancy in majority of patients raises serious concern and warrants development of novel therapeutic strategies. Immunotherapy in combination with chemotherapy has shown promising outcomes in recent years. Herein, we report better tumor regression and enhancement of antitumor immune response at the tumor microenvironment by co-delivery of paclitaxel and a TLR4 agonist through a PLGA based nanoparticle preparation (TLNP). Particle characterization showed high encapsulation of both components and retention of their biological activities. In vivo tumor regression studies demonstrated clear benefit of TLNP over the paclitaxel. The mean tumor volume of the TLNP treated animals was found to be 40% less than that of the Paclitaxel treated animals. Flow cytometric analysis of tumor infiltrating immune cells indicated activation of antigen presenting cells and T-cells providing evidence of Th1 immune response. In vivo results are promising and could pave way for novel chemo-immunotherapeutic treatment modality.

Docetaxel-carboxymethylcellulose nanoparticles target cells via a SPARC and albumin dependent mechanism.

Cellax, a polymer-docetaxel (DTX) conjugate that self-assembled into 120 nm particles, displayed significant enhancements in safety and efficacy over native DTX across a number of primary and metastatic tumor models. Despite these exciting preclinical data, the underlying mechanism of delivery of Cellax remains elusive. Herein, we demonstrated that serum albumin efficiently adsorbed onto the Cellax particles with a 4-fold increased avidity compared to native DTX, and the uptake of Cellax by cells was primarily driven by an albumin and SPARC (secreted protein acidic and rich in cysteine, an albumin binder) dependent internalization mechanism. In the SPARC-positive cells, a >2-fold increase in cellular internalization of Cellax was observed in the presence of albumin. In the SPARC-negative cells, no difference in Cellax internalization was observed in the presence or absence of albumin. Evaluation of the internalization mechanism using endocytotic inhibitors revealed that Cellax was internalized predominantly via a clathrin-mediated endocytotic mechanism. Upon internalization, it was demonstrated that Cellax was entrapped within the endo-lysosomal and autophagosomal compartments. Analysis of the tumor SPARC level with tumor growth inhibition of Cellax in a panel of tumor models revealed a positive and linear correlation (R(2) > 0.9). Thus, this albumin and SPARC-dependent pathway for Cellax delivery to tumors was confirmed both in vitro and in vivo.

Carboxymethylcellulose-Based and Docetaxel-Loaded Nanoparticles Circumvent P-Glycoprotein-Mediated Multidrug Resistance

Taxanes are a class of anticancer agents with a broad spectrum and have been widely used to treat a variety of cancer. However, its long-term use has been hampered by accumulating toxicity and development of drug resistance. The most extensively reported mechanism of resistance is the overexpression of P-glycoprotein (Pgp). We have developed a PEGylated carboxymethylcellulose conjugate of docetaxel (Cellax), which condenses into ∼120 nm nanoparticles. Here we demonstrated that Cellax therapy did not upregulate Pgp expression in MDA-MB-231 and EMT-6 breast tumor cells, whereas a significant increase in Pgp expression was measured with native docetaxel (DTX) treatment. Treatment with DTX led to 4-7-fold higher Pgp mRNA expression and 2-fold higher Pgp protein expression compared with Cellax treatment in the in vitro and in vivo system, respectively. Cellax also exhibited significantly increased efficacy compared with that of DTX in a taxane-resistant breast tumor model. Against the highly Pgp expressing EMT6/AR1 cells, Cellax exhibited a 6.5 times lower IC50 compared with that of native DTX, and in the in vivo model, Cellax exhibited 90% tumor growth inhibition, while native DTX had no significant antitumor activity.

Anticancer and Immunostimulatory Activity by Conjugate of Paclitaxel and Non-toxic Derivative of LPS for Combined Chemo-immunotherapy

ABSTRACTPurposeCancer is a multifactorial syndrome; hence, multidimensional therapy with a chemo-immunotherapeutic conjugate could be more effective in curing the disease.MethodsWe used SP-LPS, a bio-polymer having potent immunostimulatory activity, for conjugation with paclitaxel to make a chemo-immunotherapeutic conjugate. Its physicochemical characterization was done by HPLC, NMR and IR spectra. Stability was measured at different pH, temperature and in tissue homogenates. Chemotherapeutic and immunostimulatory activity was evaluated in vitro and also in tumor microenvironment.ResultsThe conjugate self assembled into nanoparticulate structure, probably due to micelle formation. Stability was pH and temperature dependent. The conjugate exhibited chemotherapeutic and immunotherapeutic activity in vitro. In vivo antitumor activity was significantly higher and a higher percentage of activated immune cells were found in the tumor microenvironment of the conjugate-treated mice as compared to Taxol®-treated group.ConclusionsThis conjugate is a potential chemo-immunotherapeutic compound for the treatment of cancer with advantages over present day chemotherapy with Taxol in terms of higher anticancer activity, less toxicity and ease of delivery.

Recent progress in the development of polysaccharide conjugates of docetaxel and paclitaxel

UNLABELLED Taxanes are one of the most potent and broadest spectrum chemotherapeutics used clinically, but also induce significant side effects. Different strategies have been developed to produce a safer taxane formulation. Development of polysaccharide drug conjugates has increased in the recent years because of the demonstrated biocompatibility, biodegradability, safety, and low cost of the biopolymers. This review focuses on polysaccharide-taxane conjugates and provides an overview on various conjugation strategies and their effect on the efficacy. Detailed analyses on the designing factors of an effective polysaccharide-drug conjugate are provided with a discussion on the future direction of this field. For further resources related to this article, please visit the WIREs website. CONFLICT OF INTEREST The authors have declared no conflicts of interest for this article.

A Simple and Improved Active Loading Method to Efficiently Encapsulate Staurosporine into Lipid-Based Nanoparticles for Enhanced Therapy of Multidrug Resistant Cancer

PurposeThis study was aimed at developing a new active loading method to stably encapsulate staurosporine (STS), a water insoluble drug, into lipid-based nanoparticles (LNPs) for drug targeting to tumors.MethodsA limited amount of DMSO was included during the active loading process to prevent precipitation and facilitate the loading of insoluble STS into the aqueous core of a LNP. The drug loading kinetics under various conditions was studied and the STS-LNPs were characterized by size, drug-to-lipid ratio, drug release kinetics and in vitro potency. The antitumor efficacy of the STS-LNPs was compared with free STS in a mouse model.ResultsThe drug loading efficiency reached 100% within 15 min of incubation at a drug-to-lipid ratio of 0.31 (mol) via an ammonium gradient. STS formed nano-aggregates inside the aqueous core of the LNPs and was stably retained upon storage and in the presence of serum. A 3-fold higher dose of the STS-LNPs could be tolerated by BALB/c mice compared with free STS, leading to nearly complete growth inhibition of a multidrug resistant breast tumor, while free STS only exhibited moderate activity.ConclusionThis simple and efficient drug loading method produced a stable LNP formulation for STS that was effective for cancer treatment.

Comparison of Tumor Penetration of Podophyllotoxin–Carboxymethylcellulose Conjugates with Various Chemical Compositions in Tumor Spheroid Culture and In Vivo Solid Tumor

Polymer conjugation is an attractive approach for delivering insoluble and highly toxic drugs to tumors. However, most reports in the literature only disclose the optimal composition without emphasizing rational design or composition optimization to achieve maximized biological effects. In this study, we aimed to demonstrate that composition of a polymer conjugate would determine its physiochemical characteristics, tumor penetration, and, ultimately, the in vivo efficacy. We also aimed to examine whether the tumor spheroid model could generate comparable results with the in vivo tumor model in terms of tumor penetration and efficacy of the various polymer conjugates. We have designed a polymer conjugate delivery system for a chemotherapeutic drug podophyllotoxin (PPT) by covalently conjugating PPT and polyethylene glycol (PEG) with acetylated carboxymethyl cellulose to yield conjugates containing various amounts of PPT and PEG. Depending on the composition, these conjugates self-assembled into nanoparticles (NPs) with different physicochemical properties. Conjugates with an increased PPT content formed particles with an increased diameter. In the present study, we selected three conjugates representing compositions containing high, medium, and low drug content, and compared their particle formation, drug release kinetics, their ability to penetrate tumor spheroid and in vivo s.c. tumor, and finally their antitumor efficacy in spheroid culture and an in vivo s.c. tumor model. We found that the low drug content conjugate formed smaller NPs (20 nm) compared to the high drug content conjugates (30-120 nm), and displayed faster drug release kinetics (5%/day vs 1-3%/day), improved tumor penetration, and enhanced antitumor efficacy in both the spheroid model and s.c. tumor model. In particular, the low drug content conjugate preferentially accumulated in the hypovascular region within the tumor, inducing complete regression of s.c. tumors and the metastasis to the lungs. Our data indicate composition optimization is needed to select the optimal conjugate, and tumor spheroid culture is a robust screening tool to help select the optimal formulation.

Synthesis of a Gemcitabine Prodrug for Remote Loading into Liposomes and Improved Therapeutic Effect

The chemotherapeutic gemcitabine was actively and stably loaded into lipid nanoparticles through the formation of a prodrug. Gemcitabine was chemically modified to increase the lipophilicity and introduce a weak base moiety for remote loading. Several derivatives were synthesized and screened for their potential to be good liposomal drug candidates for remote loading by studying their solubility, stability, cytotoxicity, and loading efficiency. Two morpholino derivatives of GEM (22 and 23) were chosen as the preferred prodrugs for this purpose as they possessed the best loading efficiencies (100% for drug-to-lipid ratio of 0.36 w/w). This is a considerable improvement over a passive loading strategy where typical loading efficiencies are on the order of ∼10-20% for a drug-to-lipid ratio of ∼0.01. Liposomes loaded with these two prodrugs were studied in an s.c. tumor model in vivo and showed improved therapeutic effect over free GEM (∼2-fold) and saline control (8- to 10-fold). This work demonstrates how chemical modification of a known hydrophilic drug can lead to improved loading, stability, and drug delivery in vivo.