Transmembrane diffusion of gemcitabine by a nanoparticulate squalenoyl prodrug: An original drug delivery pathway

Preparation and Cytotoxicity Evaluation of Folic Acid-Modified YF8-OA Self-Assembled Lipid Prodrug Nanoparticles

This study aimed to improve the use of YF8, a matrine derivative obtained through chemical transformation of matrine extracted from Sophora alopecuroides. YF8 has demonstrated improved cytotoxicity compared to matrine, but its hydrophobic nature hinders its application. To overcome this, the lipid prodrug YF8-OA was synthesized by linking oleic acid (OA) to YF8 through an ester bond. Although YF8-OA could self-assemble into unique nanostructures in water, it was not sufficiently stable. To enhance the stability of YF8-OA lipid prodrug nanoparticles (LPs), we employed the strategy of PEGylation using DSPE-mPEG₂₀₀₀ or DSPE-mPEG₂₀₀₀ conjugated with folic acid (FA). This resulted in the formation of uniform spherical nanoparticles with greatly improved stability and a maximum drug load capacity upto 58.63%. Cytotoxicity was evaluated in A549, HeLa, and HepG2 cell lines. The results showed that in HeLa cells, the IC₅₀ value of YF8-OA/LPs with FA-modified PEGylation was significantly lower than that of YF8-OA/LPs modified by PEGylation alone. However, no significant enhancement was observed in A549 and HepG2 cells. In conclusion, the lipid prodrug YF8-OA can form nanoparticles in aqueous solution to address its poor water solubility. Modification with FA resulted in further enhanced cytotoxicity, providing a potential avenue for exerting the antitumor activity of matrine analogs.

Biomimetic Gemcitabine-Lipid Prodrug Nanoparticles for Pancreatic Cancer

Gemcitabine (Gem) is a key drug for pancreatic cancer, yet limited by high systemic toxicity, low bioavailability and poor pharmacokinetic profiles. To overcome these limitations, Gem prodrug amphiphiles were synthesised with oleyl, linoleyl and phytanyl chains. Self-assembly and lyotropic mesophase behaviour of these amphiphiles were examined using polarised optical microscopy and Synchrotron SAXS (SSAXS). Gem-phytanyl was found to form liquid crystalline inverse cubic mesophase. This prodrug was combined with phospholipids and cholesterol to create biomimetic Gem-lipid prodrug nanoparticles (Gem-LPNP), verified by SSAXS and cryo-TEM to form liposomes. In vitro testing of the Gem-LPNP in several pancreatic cancer cell lines showed lower toxicity than Gem. However, in a cell line-derived pancreatic cancer mouse model Gem-LPNP displayed greater tumour growth inhibition than Gem using a fraction (<6 %) of the clinical dose and without any systemic toxicity. The easy production, improved efficacy and low toxicity of Gem-LPNP represents a promising new nanomedicine for pancreatic cancer.

Nucleoside-Lipid-Based Nanoparticles for Phenazine Delivery: A New Therapeutic Strategy to Disrupt Hsp27-eIF4E Interaction in Castration Resistant Prostate Cancer

Heat shock protein 27 (Hsp27) has an established role in tumor progression and chemo-resistance of castration-resistant prostate cancer (CRPC). Hsp27 protects eukaryotic translation initiation factor 4E (eIF4E) from degradation, thereby maintaining survival during treatment. Phenazine derivative compound #14 was demonstrated to specifically disrupt Hsp27/eIF4E interaction and significantly delay castration-resistant tumor progression in prostate cancer xenografts. In the present work, various strategies of encapsulation of phenazine #14 with either DOTAU (N-[5′-(2′,3′-dioleoyl)uridine]-N′,N′,N′-trimethylammonium tosylate) and DOU-PEG₂₀₀₀ (5′-PEG2000-2′,3′-dioleoyluridine) nucleolipids (NLs) were developed in order to improve its solubilization, biological activity, and bioavailability. We observed that NLs-encapsulated phenazine #14-driven Hsp27-eIF4E interaction disruption increased cytotoxic effects on castration-resistant prostate cancer cell line and inhibited tumor growth in castration-resistant prostate cancer cell xenografted mice compared to phenazine #14 and NLs alone. Phenazine #14 NL encapsulation might represent an interesting nanostrategy for CRPC therapy.

(Poly-cyanoacrylate) nanomedicines for cancer and beyond: Lessons learned

This « Magnum Opus » emphasizes that serendipity is a corner stone in research. The paths of discovery and innovation often result from the interdisciplinarity of scientific areas that are a priori disconnected from each other. In the 1970s, fundamental discoveries in cell biology led to unexpected advances in galenic pharmacy with the emergence of nanotechnologies for the intracellular delivery of non diffusing molecules. As well, fluorescein-loaded polyacrylamide nanocapsules were shown to deliver this fluorescent agent precisely into cellular lysosomes which represented a seminal observation. However, due to the lack of biodegradability of this carrier polymer, this approach was still far from therapeutic application. The use of cyanoacrylates as surgical glue inspired us to use this material in the design of the first biodegradable nanoparticles for human use. Capable of transporting compounds with anti-tumor activity, these polyalkylcyanoacrylate nanoparticles demonstrated the unexpected property of overcoming multi-drug resistance. This discovery led to the development of a nanomedicine that has completed phase III clinical trials for the treatment of resistant hepatocarcinoma. Going beyond the state-of-the art, a step ahead in the nanomedicine field was the drug « squalenoylation » technology, which represents a shift from the « physical » to the « chemical » encapsulation paradigm. The bioconjugation of anticancer and other drugs to squalene, a natural and biocompatible lipid, enabled a dramatic increase in drug payload, and eliminated the so-called « burst release » of drug: Two major drawbacks commonly associated with drug nanoencapsulation. The drug « squalenoylation » approach resulted in a generic nanomedicine platform with broad pharmacological applications.

The evolution of nucleosidic analogues: self-assembly of prodrugs into nanoparticles for cancer drug delivery

Nucleoside and nucleotide analogs are essential tools in our limited arsenal in the fight against cancer. However, these structures face severe drawbacks such as rapid plasma degradation or hydrophilicity, limiting their clinical application. Here, different aspects of nucleoside and nucleotide analogs have been exposed, while providing their shortcomings. Aiming to improve their fate in the body and combating their drawbacks, two different approaches have been discussed, the prodrug and nanocarrier technologies. Finally, a novel approach called "PUFAylation" based on both the prodrug and nanocarrier technologies has been introduced, promising to be the supreme method to create a novel nucleoside or nucleotide analog based formulation, with enhanced efficacy and highly reduced toxicity.

Quantitative self-assembly of pure drug cocktails as injectable nanomedicines for synergistic drug delivery and cancer therapy

New strategies to fabricate nanomedicines with high translational capacity are urgently desired. Herein, a new class of self-assembled drug cocktails that addresses the multiple challenges of manufacturing clinically useful cancer nanomedicines was reported.

Methods: With the aid of a molecular targeted agent, dasatinib (DAS), cytotoxic cabazitaxel (CTX) forms nanoassemblies (CD NAs) through one-pot process, with nearly quantitative entrapment efficiency and ultrahigh drug loading of up to 100%.

Results: Surprisingly, self-assembled CD NAs show aggregation-induced emission, enabling particle trafficking and drug release in living cells. In preclinical models of human cancer, including a patient-derived melanoma xenograft, CD NAs demonstrated striking therapeutic synergy to produce a durable recession in tumor growth. Impressively, CD NAs alleviated the toxicity of the parent CTX agent and showed negligible immunotoxicity in animals.

Conclusions: Overall, this approach does not require any carrier matrices, offering a scalable and cost-effective methodology to create a new generation of nanomedicines for the safe and efficient delivery of drug combinations.

Self-assembling a natural small molecular inhibitor that shows aggregation-induced emission and potentiates antitumor efficacy

Targeted therapy using small molecular inhibitors has been developed to rewire key signaling pathways in tumor cells, but these inhibitors have had mixed success in the clinic due to their poor pharmaceutical properties and suboptimal intratumoral concentrations. Here, we developed a "self-assembling natural molecular inhibitor" strategy to test the efficacy and feasibility of the water-insoluble agent dasatinib (DAS), a tyrosine kinase inhibitor, for cancer therapy. By exploiting a facile reprecipitation protocol, the DAS inhibitor self-assembled into soluble supramolecular nanoparticles (termed sDNPs) in aqueous solution, without an exogenous excipient. This strategy is applicable for generating systemically injectable and colloid-stable therapeutic nanoparticles of hydrophobic small-molecule inhibitors. Concurrently, during this process, we observed aggregation-induced emission (AIE) of fluorescence for this self-assembled DAS, which makes sDNPs suitable for bioimaging and tracing of cellular trafficking. Notably, in an orthotopic model of breast cancer, administration of sDNPs induced a durable inhibition of primary tumors and reduced the metastatic tumor burden, significantly surpassing the effects of the free DAS inhibitor after oral delivery. In addition, low toxicity was observed for this platform, with effective avoidance of immunotoxicity. To the best of our knowledge, our studies provide the first successful demonstration of self-assembling natural molecular inhibitors with AIE and highlight the feasibility of this approach for the preparation of therapeutic nanoparticles for highly lethal human cancers and many other diseases.

Enhancing efficacy of gemcitabine in pancreatic patient-derived xenograft mouse models

Gemcitabine (Gem), a nucleoside analog, is a preferred choice of treatment for pancreatic cancer (PCa) and often used in combination therapy against wide range of solid tumors. It is known to be rapidly inactivated in blood by cytidine deaminase. The objective of the study was to improve the systemic stability and anticancer activity of modified Gem termed 4-N-stearoylGem (4NSG) In this study, the IC50 values of 4NSG treated MiaPaCa-2 and primary pancreatic cancer (PPCL-46) cultures were significantly lower when compared with gemcitabine hydrochloride (GemHCl) treated cultures. In acute toxicity study, liver enzyme level of aspartate aminotransferase (AST) of the control mice was not significantly different from AST levels of 4NSG and GemHCl treated mice. However, alanine aminotransferase (ALT) level of control mice (67 ± 5 mUnits/mL) was significantly lower compared with ALT levels of GemHCl (232 ± 28 mUnits/mL) and that of 4NSG (172 ± 22 mUnits/mL) (p < 0.0001). More importantly, ALT level of 4NSG was lower than ALT level of GemHCl (p < 0.05). Although ALT levels were elevated, pathological images of liver and kidney tissues of control, GemHCl and 4NSG treated mice revealed no architectural changes and no significant change in mice weight was observed during treatment. The bioavailability (AUC) of 4NSG was 3-fold high and significantly inhibited the tumor growth as compared with equivalent dose of GemHCl. Immunohistochemical staining revealed that 4NSG significantly inhibited the expression vascular endothelial growth factor (VEGF) receptor. The study is unique because it established, for the first time, enhanced anticancer activity of 4NSG against pancreatic patient-derived xenograft (PDX) mouse model and PPCL-46 cells compared with Gem. 4SGN enhanced pharmacokinetic profile and improved the therapeutic efficacy of the standard-of-care Gem. Lastly, 4GSN showed a remarkable tumor growth inhibition and revealed significant antiangiogenic activity in 4GSN treated pancreatic PDX tumor.

Squalenoyl-gemcitabine/edelfosine nanoassemblies: Anticancer activity in pediatric cancer cells and pharmacokinetic profile in mice

Despite the great advances accomplished in the treatment of pediatric cancers, recurrences and metastases still exacerbate prognosis in some aggressive solid tumors such as neuroblastoma and osteosarcoma. In view of the poor efficacy and toxicity of current chemotherapeutic treatments, we propose a single multitherapeutic nanotechnology-based strategy by co-assembling in the same nanodevice two amphiphilic antitumor agents: squalenoyl-gemcitabine and edelfosine. Homogeneous batches of nanoassemblies were easily formulated by the nanoprecipitation method. Their anticancer activity was tested in pediatric cancer cell lines and pharmacokinetic studies were performed in mice. In vitro assays revealed a synergistic effect when gemcitabine was co-administered with edelfosine. Squalenoyl-gemcitabine/edelfosine nanoassemblies were found to be capable of intracellular translocation in patient-derived metastatic pediatric osteosarcoma cells and showed a better antitumor profile than squalenoyl-gemcitabine nanoassemblies alone. The intravenous administration of this combinatorial nanomedicine in mice exhibited a controlled release behavior of gemcitabine and diminished edelfosine plasma peak concentrations. These findings make it a suitable pre-clinical candidate for childhood cancer therapy.

Self-Assembled Gemcitabine Prodrug Nanoparticles Show Enhanced Efficacy against Patient-Derived Pancreatic Ductal Adenocarcinoma

Effective new therapies for pancreatic ductal adenocarcinoma (PDAC) are desperately needed as the prognosis of PDAC patients is dismal and treatment remains a major challenge. Gemcitabine (GEM) is commonly used to treat PDAC; however, the clinical use of GEM has been greatly compromised by its low delivery efficacy and drug resistance. Here, we describe a very simple yet cost-effective approach that synergistically combines drug reconstitution, supramolecular nanoassembly, and tumor-specific targeting to address the multiple challenges posed by the delivery of the chemotherapeutic drug GEM. Using our developed PUFAylation technology, the GEM prodrug was able to spontaneously self-assemble into colloidal stable nanoparticles with sub-100 nm size on covalent attachment of hydrophobic linoleic acid via amide linkage. The prodrug nanoassemblies could be further refined by PEGylation and PDAC-specific peptide ligand for preclinical studies. In vitro cell-based assays showed that not only were GEM nanoparticles superior to free GEM but also the decoration with PDAC-homing peptide facilitated the intracellular uptake of nanoparticles and thereby augmented the cytotoxic activity. In two separate xenograft models of human PDAC, one of which was a patient-derived xenograft model, the administration of targeted nanoparticles resulted in marked inhibition of tumor progression as well as alleviated systemic toxicity. Together, these data unequivocally confirm that the hydrophilic and rapidly metabolized drug GEM can be feasibly transformed into a pharmacologically efficient nanomedicine through exploiting the PUFAylation technology. This strategy could also potentially be applied to rescue many other therapeutics that show unfavorable outcomes in the preclinical studies because of pharmacologic obstacles.

Introduction of magnetic and supermagnetic nanoparticles in new approach of targeting drug delivery and cancer therapy application

In this article, the recent applications of different types of magnetic nanoparticles such as α-Fe₂O₃ (hematite), γ-Fe₂O₃ (maghemite), Fe₃O₄ (magnetite), hexagonal (MFe₁₂O₁₉), garnet (M₃Fe₅O₁₂) and spinel (MFe₂O₄), where M represents one or more bivalent transition metals (Mn, Fe, Co, Ni, Ba, Sr, Cu, and Zn), and different materials for coating the surface of magnetic nanoparticles like poly lactic acid (PLA), doxorubicin hydrophobic (DOX-HCL), paclitaxel (PTX), EPPT-FITC, oleic acid, tannin, 3-Aminopropyltriethoxysilane (APTES), multi-wall carbon nanotubes (CNTs), polyethylenimine (PEI) and polyarabic acid in drug delivery, biomedicine and treatment of cancer, specially chemotherapy, are reviewed. MNPs possess large surface area to volume ratios because of their nano-size, low surface charge at physiological pH and they aggregate easily in solution due to their essential magnetic nature. These materials are widely used in biology and medicine in many cases. One targeted delivery technique that has gained prominence in recent years is the use of magnetic nanoparticles. In these systems, therapeutic compounds are attached to biocompatible magnetic nanoparticles and magnetic fields generated outside the body are focused on specific targets in vivo. The fields capture the particle complex, resulting in enhanced delivery to the target site. Also, the application of brand new supermagnetic nanoparticles, like Ba,SrFe₁₂O₁₉, is considered and studied in this paper.

From poly(alkyl cyanoacrylate) to squalene as core material for the design of nanomedicines

This review article covers the most important steps of the pioneering work of Patrick Couvreur and tries to shed light on his outstanding career that has been a source of inspiration for many decades. His discovery of biodegradable poly(alkyl cyanoacrylate) (PACA) nanoparticles (NPs) has opened large perspectives in nanomedicine. Indeed, NPs made from various types of alkyl cyanoacrylate monomers have been used in different applications, such as the treatment of intracellular infections or the treatment of multidrug resistant hepatocarcinoma. This latest application led to the Phase III clinical trial of Livatag^®, a PACA nanoparticulate formulation of doxorubicin. Despite the success of PACA NPs, the development of a novel type of NP with higher drug loadings and lower burst release was tackled by the discovery of squalene-based nanomedicines where the drug is covalently linked to the lipid derivative and the resulting conjugate is self-assembled into NPs. This pioneering work was accompanied by a wide range of novel applications which mainly dealt with the management of unmet medical needs (e.g. pancreatic cancer, brain ischaemia and spinal cord injury).

Dihydroartemisinin increases gemcitabine therapeutic efficacy in ovarian cancer by inducing reactive oxygen species

Ovarian cancer is the major cause of death in women gynecological malignancy and gemcitabine (GEM) is commonly used in related chemotherapy. However, more than 90% GEM is catalyzed into an inactive metabolite 2'-deoxy-2',2'-difluorouridine by stromal and cellular cytidine deaminase (CDA). Dihydroartemisinin (DHA), which possesses an intramolecular endoperoxide bridge, could be activated by heme or ferrous iron to produce reactive oxygen species (ROS). The excess ROS generation will excite expression of heme oxygenase-1 and suppress CDA expression. Under low CDA expression, the inactivation of GEM is decreased in turn to exert excellent therapeutic efficiency. Herein, we first studied the ROS generation by DHA in vitro with A2780 cells by means of flow cytometry and confocal laser scanning microscopy. Furthermore, cytotoxicity assay in vitro showed that DHA + GEM had synergistic effect, with molar ratio of DHA and GEM at 10. Eventually, in A2780 ovarian cancer xenograft tumor model, DHA + GEM exhibited significant antitumor efficiency with lower blood toxicity than GEM alone. Noteworthy, the combination treatment group completely eliminated the tumors on day 14.

A Scalable Method for Squalenoylation and Assembly of Multifunctional 64Cu-Labeled Squalenoylated Gemcitabine Nanoparticles

Squalenoylation of gemcitabine, a front-line therapy for pancreatic cancer, allows for improved cellular-level and system-wide drug delivery. The established methods to conjugate squalene to gemcitabine and to form nanoparticles (NPs) with the squalenoylated gemcitabine (SqGem) conjugate are cumbersome, time-consuming and can be difficult to reliably replicate. Further, the creation of multi-functional SqGem-based NP theranostics would facilitate characterization of in vivo pharmacokinetics and efficacy.

Methods: Squalenoylation conjugation chemistry was enhanced to improve reliability and scalability using tert-butyldimethylsilyl (TBDMS) protecting groups. We then optimized a scalable microfluidic mixing platform to produce SqGem-based NPs and evaluated the stability and morphology of select NP formulations using dynamic light scattering (DLS) and transmission electron microscopy (TEM). Cytotoxicity was evaluated in both PANC-1 and KPC (Kras^LSL-G12D/+; Trp53^LSL-R172H/+; Pdx-Cre) pancreatic cancer cell lines. A ⁶⁴Cu chelator (2-S-(4-aminobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid, NOTA) was squalenoylated and used with positron emission tomography (PET) imaging to monitor the in vivo fate of SqGem-based NPs.

Results: Squalenoylation yields of gemcitabine increased from 15% to 63%. Cholesterol-PEG-2k inclusion was required to form SqGem-based NPs using our technique, and additional cholesterol inclusion increased particle stability at room temperature; after 1 week the PDI of SqGem NPs with cholesterol was ~ 0.2 while the PDI of SqGem NPs lacking cholesterol was ~ 0.5. Similar or superior cytotoxicity was achieved for SqGem-based NPs compared to gemcitabine or Abraxane® when evaluated at a concentration of 10 µM. Squalenoylation of NOTA enabled in vivo monitoring of SqGem-based NP pharmacokinetics and biodistribution.

Conclusion: We present a scalable technique for fabricating efficacious squalenoylated-gemcitabine nanoparticles and confirm their pharmacokinetic profile using a novel multifunctional ⁶⁴Cu-SqNOTA-SqGem NP.

In Vivo FRET Imaging to Predict the Risk Associated with Hepatic Accumulation of Squalene-Based Prodrug Nanoparticles

Förster resonance energy transfer (FRET) is used here for the first time to monitor the in vivo fate of nanoparticles made of the squalene-gemcitabine prodrug and two novel derivatives of squalene with the cyanine dyes 5.5 and 7.5, which behave as efficient FRET pair in the NIR region. Following intravenous administration, nanoparticles initially accumulate in the liver, then they show loss of their integrity within 2 h and clearance of the squalene bioconjugates is observed within 24 h. Such awareness is a key prerequisite before introduction into clinical settings.

5-Aminolevulinic Acid-Squalene Nanoassemblies for Tumor Photodetection and Therapy: In Vitro Studies

Protoporphyrin IX (PpIX) as natural photosensitizer derived from administration of 5-aminolevulinic acid (5-ALA) has found clinical use for photodiagnosis and photodynamic therapy of several cancers. However, broader use of 5-ALA in oncology is hampered by its charge and polarity that result in its reduced capacity for passing biological barriers and reaching the tumor tissue. Advanced drug delivery platforms are needed to improve the biodistribution of 5-ALA. Here, we report a new approach for the delivery of 5-ALA. Squalenoylation strategy was used to covalently conjugate 5-ALA to squalene, a natural precursor of cholesterol. 5-ALA-SQ nanoassemblies were formed by self-assembly in water. The nanoassemblies were monodisperse with average size of 70 nm, polydispersity index of 0.12, and ζ-potential of + 36 mV. They showed good stability over several weeks. The drug loading of 5-ALA was very high at 26%. In human prostate cancer cells PC3 and human glioblastoma cells U87MG, PpIX production was monitored in vitro upon the incubation with nanoassemblies. They were more efficient in generating PpIX-induced fluorescence in cancer cells compared to 5-ALA-Hex at 1.0 to 3.3 mM at short and long incubation times. Compared to 5-ALA, they showed superior fluorescence performance at 4 h which was diminished at 24 h. 5-ALA-SQ presents a novel nano-delivery platform with great potential for the systemic administration of 5-ALA.

Poly-isoprenylated ifosfamide analogs: Preactivated antitumor agents as free formulation or nanoassemblies

Oxazaphosphorines including cyclophosphamide, trofosfamide and ifosfamide (IFO) belong to the alkylating agent class and are indicated in the treatment of numerous cancers. However, IFO is subject to limiting side-effects in high-dose protocols. To circumvent IFO drawbacks in clinical practices, preactivated IFO analogs were designed to by-pass the toxic metabolic pathway. Among these IFO analogs, some of them showed the ability to self-assemble due to the use of a poly-isoprenyloxy chain as preactivating moiety. We present here, the in vitro activity of the nanoassembly formulations of preactivated IFO derivatives with a C-4 geranyloxy, farnesyloxy and squalenoxy substituent on a large panel of tumor cell lines. The chemical and colloidal stabilities of the geranyloxy-IFO (G-IFO), farnesyloxy-IFO (F-IFO) and squalenoxy-IFO (SQ-IFO) NAs were further evaluated in comparison to their free formulation. Finally, pharmacokinetic parameters and maximal tolerated dose of the most potent preactivated IFO analog (G-IFO) were determined and compared to IFO, paving the way to in vivo studies.

Circulating Lipoproteins: A Trojan Horse Guiding Squalenoylated Drugs to LDL-Accumulating Cancer Cells

Selective delivery of anticancer drugs to rapidly growing cancer cells can be achieved by taking advantage of their high receptor-mediated uptake of low-density lipoproteins (LDLs). Indeed, we have recently discovered that nanoparticles made of the squalene derivative of the anticancer agent gemcitabine (SQGem) strongly interacted with the LDLs in the human blood. In the present study, we showed both in vitro and in vivo that such interaction led to the preferential accumulation of SQGem in cancer cells (MDA-MB-231) with high LDL receptor expression. As a result, an improved pharmacological activity has been observed in MDA-MB-231 tumor-bearing mice, an experimental model with a low sensitivity to gemcitabine. Accordingly, we proved that the use of squalene moieties not only induced the gemcitabine insertion into lipoproteins, but that it could also be exploited to indirectly target cancer cells in vivo.

Conjugation of squalene to gemcitabine as unique approach exploiting endogenous lipoproteins for drug delivery

Once introduced in the organism, the interaction of nanoparticles with various biomolecules strongly impacts their fate. Here we show that nanoparticles made of the squalene derivative of gemcitabine (SQGem) interact with lipoproteins (LPs), indirectly enabling the targeting of cancer cells with high LP receptors expression. In vitro and in vivo experiments reveal preeminent affinity of the squalene-gemcitabine bioconjugates towards LP particles with the highest cholesterol content and in silico simulations further display their incorporation into the hydrophobic core of LPs. To the best of our knowledge, the use of squalene to induce drug insertion into LPs for indirect cancer cell targeting is a novel concept in drug delivery. Interestingly, not only SQGem but also other squalene derivatives interact similarly with lipoproteins while such interaction is not observed with liposomes. The conjugation to squalene represents a versatile platform that would enable efficient drug delivery by simply exploiting endogenous lipoproteins.

The interaction of nanoparticles with a range of biomolecules once they have been injected within the body can affect their performance. Here, the authors demonstrate that squalene nanomaterials conjugated with anticancer drugs can interact with lipoproteins and can be used to target cancer cells.

Cellular uptake and anti-tumor activity of gemcitabine conjugated with new amphiphilic cell penetrating peptides

Gemcitabine (Gem) is used as a single agent or in combination with other anticancer agents to treat many types of solid tumors. However, it has many limitations such as a short plasma half-life, dose-limiting toxicities and drug resistance. Cell-penetrating peptides (CPPs) are short peptides which may deliver a large variety of cargo molecules into the cancerous cells. The current study was designed to evaluate the antiproliferative activity of gemcitabine chemically conjugated to CPPs. The peptides were synthesized using solid phase synthesis procedure. The uptake efficiency of CPPs into cells was examined by flow cytometry and fluorescent microscopy. The synthesized peptides were chemically conjugated to Gem and the in vitro cytotoxicity of conjugates was tested by MTT assay on A594 cell line. According to the obtained results, cellular uptake was increased with increasing the concentration of CPPs. On the other hand the coupling of Gem with peptides containing block sequence of arginine (R5W3R4) and some alternating sequences (i.e. [RW]6 and [RW]3) exhibited improved antitumor activity of the drug. The findings in this study support the advantages of using cell-penetrating peptides for improving intracellular delivery of Gem into tumor as well as its activity.

Nanotechnology for delivery of gemcitabine to treat pancreatic cancer

Pancreatic cancer (PC) is one of the most deadly and quickly fatal human cancers with a 5-year mortality rate close to 100%. Its prognosis is very poor, mainly because of its hostile biological behavior and late onset of symptoms for clinical diagnosis; these bring limitations on therapeutic interventions. Factors contributing for the difficulties in treating PC include: high rate of drug resistance, fast metastasis to different organs, poor prognosis and relapse of the tumor after therapy. After being approved by US FDA 1997, Gemcitabine (Gem) is the first line and the gold standard drug for all stages of advanced PC till now. However, its efficacy is unsatisfactory, mainly due to; its chemical instability and poor cellular uptake, resulting in an extremely short half-life and low bioavailability. To solve this drawbacks and increase the therapeutic outcome important progress has been achieved in the field of nanotechnology and offers a promising and effective alternative. This review mainly focus on the most commonly investigated nanoparticle (NP) delivery systems of Gem for PC treatment and the latest progresses achieved. Novel nanocarriers with better tumor targeting efficiencies and maximum treatment outcome to treat this deadly due are given much attention.

Biodistribution of Self-Assembling Polymer-Gemcitabine Conjugate after Systemic Administration into Orthotopic Pancreatic Tumor Bearing Mice

Therapeutic efficacy of gemcitabine (GEM) is severely limited due to its rapid metabolism by enzymatic deamination in vivo. We recently determined its therapeutic efficacy before (F-GEM) and after conjugation to poly(ethylene glycol)-block-poly(2-methyl-2-carboxyl-propylene carbonate) (mPEG-b-PCC-g-GEM-g-DC, abbreviated as P-GEM) in subcutaneous and orthotopic pancreatic tumor bearing mice. In this study, pharmacokinetic (PK) parameters and biodistribution profiles of F-GEM and P-GEM were determined after intravenous injection into orthotopic pancreatic tumor bearing NSG mice. To assess the short-term toxicity, the levels of hematological, hepatic, and renal injury markers were measured after 24 h postadministration into these mice. P-GEM was distributed to all the major organs, with higher accumulation in the liver, spleen, and tumor compared to F-GEM. Area under the curve (AUC), elimination half-life (t_1/2), and mean residence time (MRT) of P-GEM treated group were significantly higher compared to those of F-GEM treated group: 246,425 ± 1605 vs 83,591 ± 1844 ng/mL × h as AUC, 5.77 ± 2.02 vs 1.99 ± 0.09 h as t_1/2, and 4.45 ± 0.15 vs 1.12 ± 0.13 h as MRT. Further, P-GEM exhibited negligible systemic toxicity as evidenced by almost similar alanine aminotransferase (ALT) and aspartate aminotransferase (AST) values for both P-GEM and F-GEM. These results suggest that P-GEM protects GEM from degradation and provides sustained drug release, resulting in enhanced GEM delivery to the tumor by more than 2.5-fold compared to F-GEM. Hence, P-GEM is a promising gemcitabine conjugated polymeric micelle for treating pancreatic cancer.

Recent advances in drug delivery strategies for improved therapeutic efficacy of gemcitabine

Gemcitabine (2',2'-difluoro-2'-deoxycytidine; dFdC) is an efficacious anticancer agent acting against a wide range of solid tumors, including pancreatic, non-small cell lung, bladder, breast, ovarian, thyroid and multiple myelomas. However, short plasma half-life due to metabolism by cytidine deaminase necessitates administration of high dose, which limits its medical applicability. Further, due to its hydrophilic nature, it cannot traverse cell membranes by passive diffusion and, therefore, enters via nucleoside transporters that may lead to drug resistance. To circumvent these limitations, macromolecular prodrugs and nanocarrier-based formulations of Gemcitabine are gaining wide recognition. The nanoformulations based approaches by virtue of their controlled release and targeted delivery have proved to improve bioavailability, increase therapeutic efficacy and reduce adverse effects of the drug. Furthermore, the combination of Gemcitabine with other anticancer agents as well as siRNAs using nanocarriers has also been investigated in order to enhance its therapeutic potential. This review deals with challenges and recent advances in the delivery of Gemcitabine with particular emphasis on macromolecular prodrugs and nanomedicines.

PEGylated squalenoyl-gemcitabine nanoparticles for the treatment of glioblastoma

New treatments for glioblastoma multiforme (GBM) are desperately needed, as GBM prognosis remains poor, mainly due to treatment resistance, poor distribution of therapeutics in the tumor tissue, and fast metabolism of chemotherapeutic drugs in the brain extracellular space. Convection-enhanced delivery (CED) of nanoparticles (NPs) has been shown to improve the delivery of chemotherapeutic drugs to the tumor bed, providing sustained release, and enhancing survival of animals with intracranial tumors. Here we administered gemcitabine, a nucleoside analog used as a first line treatment for a wide variety of extracranial solid tumors, within squalene-based NPs using CED, to overcome the above-mentioned challenges of GBM treatment. Small percentages of poly(ethylene) glycol (PEG) dramatically enhanced the distribution of squalene-gemcitabine nanoparticles (SQ-Gem NPs) in healthy animals and tumor-bearing animals after administration by CED. When tested in an orthotopic model of GBM, SQ-Gem-PEG NPs demonstrated significantly improved therapeutic efficacy compared to free gemcitabine, both as a chemotherapeutic drug and as a radiosensitizer. Furthermore, MR contrast agents were incorporated into the SQ-Gem-PEG NP formulation, providing a way to non-invasively track the NPs during infusion.

Micelle Mixtures for Coadministration of Gemcitabine and GDC-0449 To Treat Pancreatic Cancer

Hedgehog (Hh) signaling plays an important role in the development and metastasis of pancreatic ductal adenocarcinoma (PDAC). Although gemcitabine (GEM) has been used as a first-line therapy for PDAC, its rapid metabolism and short plasma half-life restrict its use as a single chemotherapy. Combination therapy with more than one drug is a promising approach for treating cancer. Herein, we report the use of methoxy poly(ethylene glycol)-block-poly(2-methyl-2-carboxyl-propylene carbonate)-graft-dodecanol (mPEG-b-PCC-g-DC) copolymer for conjugating GEM and encapsulating a Hh inhibitor, vismodegib (GDC-0449), into its hydrophobic core for treating PDAC. Our objective was to determine whether the micelle mixtures of these two drugs could show better response in inhibiting Hh signaling pathway and restraining the proliferation and metastasis of pancreatic cancer. The in vivo stability of GEM significantly increased after conjugation, which resulted in its increased antitumor efficacy. Almost 80% of encapsulated GDC-0449 and 19% conjugated GEM were released in vitro at pH 5.5 in 48 h in a sustained manner. The invasion, migration, and colony forming features of MIA PaCa-2 cells were significantly inhibited by micelle mixture carrying GEM and GDC-0449. Remarkable increase in PARP cleavage and Bax proved increased apoptosis by this combination formulation compared to individual micelles. This combination therapy efficiently inhibited tumor growth, increased apoptosis, reduced Hh ligands PTCH-1 and Gli-1, and lowered EMT-activator ZEB-1 when injected to athymic nude mice bearing subcutaneous tumor generated using MIA PaCa-2 cells compared to monotherapy as observed from immunohistochemical analysis. In conclusion, micelle mixtures carrying GEM and GDC-0449 have the potential to treat pancreatic cancer.

How can nanomedicines overcome cellular-based anticancer drug resistance?

This review discusses the mechanisms of anticancer drug resistance according to its cellular level of action and outlines the nanomedicine-based strategies adopted to overcome it.

An in vitro and in vivo study of gemcitabine-loaded albumin nanoparticles in a pancreatic cancer cell line

BACKGROUND AND OBJECTIVES

Gemcitabine (Gem) is far from satisfactory as the first-line regimen for pancreatic cancer, and the emergence of albumin nanoparticles offers new hope for the delivery of Gem. In this study, Gem-loaded human serum albumin nanoparticles (Gem-HSA-NPs) were successfully synthesized, characterized, and tested on a BxPC-3 cell line both in vitro and in vivo.

MATERIALS AND METHODS

4-N-myristoyl-gemcitabine (Gem-C14) was obtained first by coupling myristoyl with the 4-amino group of Gem. The Gem-HSA-NPs were then prepared by nanoparticle albumin-bound technology and characterized for particle size, zeta potential, morphology, encapsulation efficiency, drug-loading efficiency, and release characteristics. Using both in vitro and in vivo studies, Gem-C14 and Gem-HSA-NPs were tested on the human pancreatic cancer cell line BxPC-3.

RESULTS

Gem-HSA-NPs showed an average particle size of 150±27 nm, and with an encapsulation rate of 82.99%±3.5% and a drug-loading rate of 10.42%±3.5%, they exhibited a favorable controlled- and sustained-release nature. In in vitro, Gem-C14 was equivalent in cytotoxicity to Gem. In in vivo, the Gem-HSA-NPs exhibited the strongest inhibitory effect on tumor growth but the lowest toxicity among the four groups.

CONCLUSION

The enhanced in vivo efficacy of Gem-HSA-NPs toward the pancreatic cancer cell line suggests their potential role for use in the clinical field.

An efficient system for intracellular delivery of beta-lactam antibiotics to overcome bacterial resistance

The "Golden era" of antibiotics is definitely an old story and this is especially true for intracellular bacterial infections. The poor intracellular bioavailability of antibiotics reduces the efficency of many treatments and thereby promotes resistances. Therefore, the development of nanodevices coupled with antibiotics that are capable of targeting and releasing the drug into the infected-cells appears to be a promising solution to circumvent these complications. Here, we took advantage of two natural terpenes (farnesyl and geranyl) to design nanodevices for an efficient intracellular delivery of penicillin G. The covalent linkage between the terpene moieties and the antibiotic leads to formation of prodrugs that self-assemble to form nanoparticles with a high drug payload between 55-63%. Futhermore, the addition of an environmentally-sensitive bond between the antibiotic and the terpene led to an efficient antibacterial activity against the intracellular pathogen Staphylococcus aureus with reduced intracellular replication of about 99.9% compared to untreated infected cells. Using HPLC analysis, we demonstrated and quantified the intracellular release of PenG when this sensitive-bond (SB) was present on the prodrug, showing the success of this technology to deliver antibiotics directly into cells.

The role of solvent swelling in the self-assembly of squalene based nanomedicines

Squalene based nanoparticles obtained via nanoprecipitation are promising candidates as efficient anti-cancer drugs. In order to highlight their preparation process and to facilitate further clinical translation, the present study enlightens the paramount role of the solvent in the formation of these nanomedicines. Three different squalene-based nanoparticles, i.e. squalenic acid, deoxycytidine squalene and gemcitabine squalene, have been investigated before and after organic solvent evaporation. Size and structural analysis by Small Angle Neutron Scattering revealed that droplets' size was uniquely controlled by the solvent composition (ethanol-water), which evolved during their gradual formation. The particles were preferably swollen by water and the swelling increased when less ethanol was present. Either coalescence or fragmentation was observed depending on the increase or decrease of the ethanol content, supporting an equilibrium control of the size. Moreover, a high water swelling was observed for the three local organization of the nanodroplets (hexagonal for gemcitabine squalene, cubic for deoxycytidine and not structured for squalenic acid) and could be the source of the previously reported efficiency of related anti-cancer squalene based nanomedicines.

Enhanced cellular uptake and intracellular drug controlled release of VESylated gemcitabine prodrug nanocapsules

Gemcitabine, 2',2'-difluoro-2'-deoxycytidine (dFdC), is the first-line antitumor agent in the treatment of pancreatic tumors. However, it possesses certain drawbacks, such as poor biological half-life resulted from rapid metabolism and the induction of resistance, leading to its restricted therapeutic potential. With the purpose of overcoming the above drawbacks, we developed a novel VESylated gemcitabine (VES-dFdC) prodrug by coupling the N4-amino group of the pyrimidine ring of dFdC to the carboxylic group of vitamin E succinate (VES). The resulting amphiphilic compound could protect the N4-amino group of the pyrimidine ring of dFdC from being degraded by cytidine deaminase. What is more, the prodrug was able to form nanocapsules in aqueous media (similar to the structure of cytomembrane), confirmed by transmission electron microscope (TEM). Their average particle size is about 107 nm with zeta potential of -33.4 mV measured by dynamic light scattering (DLS). VES-dFdC nanocapsules showed accelerated accumulative drug release profile in simulated lysosome environment (sodium acetate buffer pH 5+cathepsin B, an enzyme in lysosome), due to the easily hydrolyzed property of amide bond by cathepsin B, while rather stable in PBS (pH 7.4) or sodium acetate buffer (pH 5.0) without cathepsin B, indicating their enhanced intracellular drug controlled release manner. Besides, VES-dFdC prodrug nanocapsules showed enhanced cellular uptake ability, and the amount of cellular uptake of the nanocapsules by the pancreatic cancer cell line BxPC-3 is seventy times higher than that of native gemcitabine in the first 1.5 h. Compared with free gemcitabine, VES-dFdC nanocapsules showed essentially increased growth inhibition activity against BxPC-3 cells, indicating its great potential as prodrug for pancreatic tumor therapy with improved antitumor activity.

Gemcitabine-based therapy for pancreatic cancer using the squalenoyl nucleoside monophosphate nanoassemblies

Gemcitabine is currently the most effective agent against advanced pancreatic cancer. However, the major therapeutic hurdles using gemcitabine include rapid inactivation by blood deaminases and fast development of cell chemoresistance, induced by down-regulation of deoxycytidine kinase or nucleoside transporters. To overcome the above drawbacks we designed recently a novel nanomedicine strategy based on squalenoyl prodrug of 5'-monophosphate gemcitabine (SQdFdC-MP). This amphiphilic conjugate self-organized in water into unilamellar vesicles with a mean diameter of 100 nm. In this study the antitumor efficacy of SQdFdC-MP nanoassemblies (NAs) on chemoresistant and chemosensitive pancreatic adenocarcinoma models have been investigated. Cell viability assays showed that SQdFdC-MP NAs displayed higher antiproliferative and cytotoxic effects, particularly in chemoresistant pancreatic tumor cells. In in vivo studies, SQdFdC-MP NAs decreased significantly the growth (∼70%) of human MiaPaCa2 xenografts, also preventing tumor cell invasion, whereas native dFdC did not display any anticancer activity when tumor growth inhibition was only 35% with SQdFdC NAs. These results correlated with a reduction of Ki-67 antigen and the induction of apoptosis mediated by caspase-3 activation in tumor cells. These findings demonstrated the feasibility of utilizing SQdFdC-MP NAs to make tumor cells more sensitive to gemcitabine and thus providing an efficient new therapeutic alternative for pancreatic adenocarcinoma.

Peptide-functionalized nanoparticles for selective targeting of pancreatic tumor

Chemotherapy for pancreatic cancer is hampered by the tumor's physio-pathological complexity. Here we show a targeted nanomedicine using a new ligand, the CKAAKN peptide, which had been identified by phage display, as an efficient homing device within the pancreatic pathological microenvironment. Taking advantage of the squalenoylation platform, the CKAAKN peptide was conjugated to squalene (SQCKAAKN) and then co-nanoprecipitated with the squalenoyl prodrug of gemcitabine (SQdFdC) giving near monodisperse nanoparticles (NPs) for safe intravenous injection. By interacting with a novel target pathway, the Wnt-2, the CKAAKN functionalization enabled nanoparticles: (i) to specifically interact with both tumor cells and angiogenic vessels and (ii) to simultaneously promote pericyte coverage, thus leading to the normalization of the vasculature likely improving the tumor accessibility for therapy. All together, this approach represents a unique targeted nanoparticle design with remarkable selectivity towards pancreatic cancer and multiple mechanisms of action.

Self-assembly of polyisoprenoyl gemcitabine conjugates: influence of supramolecular organization on their biological activity

An amphiphilic prodrug of gemcitabine, a cytidine analogue used clinically against various tumors, had been previously synthesized by covalent coupling to squalene, a natural isoprenoid chain. The resulting bioconjugate self-assembled spontaneously in water as nanoparticles, displaying an impressive activity both in vitro and in vivo. The aim of the present study was to determine the influence of the length of the isoprene moiety on the structure of the nanoparticles, in an attempt to establish a relationship between the chemical structure of the prodrug, its supramolecular organization, and its pharmacological activity. Remarkably, gemcitabine-squalene and gemcitabine-5-isoprenes, which differ only in the position of two methyl groups on the hydrophobic chain, displayed different supramolecular organizations and different anticancer activities on some cell lines. This difference in activity was related to the ability of nanoparticles to be internalized by cells.

Interactions of anticancer drugs with biomembranes: what can we learn from model membranes?

The interactions of anticancer drugs with cell membranes are of primary importance for drug transport, accumulation and activity. However, these interactions are very difficult to investigate because of the complexity of biological membranes. Lipid model membranes have therefore been built to gain insight into the collective role of lipids in drug-membrane interactions. Membranes can act as a barrier for drug molecules, sequester them or conversely may allow them to freely diffuse, thereby modulating the accumulation of drugs into cells. Lipid membranes also affect the ability of the efflux pump Pgp to bind and efflux anticancer drugs from cells. On the other hand, anticancer drugs can alter the structure and properties of lipid membranes, which are expected to influence the functioning of embedded proteins. The relevance of lipid model membranes to assess interactions between anticancer drugs and biomembranes is evidenced.

Synthesis, characterization and mechanistic-insight into the anti-proliferative potential of PLGA-gemcitabine conjugate

Gemcitabine, a nucleoside analogue, is used in the treatment of various solid tumors, however, its efficacy is limited by rapid metabolism by cytidine deaminase and fast kidney excretion. In this study, a polymeric conjugate of gemcitabine was prepared by covalent coupling with poly(lactic-co-glycolic) acid (PLGA), in order to improve anticancer efficacy of the drug. The prepared conjugate was characterized by various analytical techniques including FTIR, NMR and mass spectroscopic analysis. The stability study indicated that the polymeric conjugate was more stable in plasma as compared to native gemcitabine. Further, in vitro cytotoxicity determined in a panel of cell lines including pancreatic cancer (MIAPaCa-2), breast cancer (MCF-7) and colon cancer (HCT-116), indicated that the cytotoxic activity of gemcitabine was retained following conjugation with polymeric carrier. In the nucleoside transportation inhibition assay, it was found that the prepared conjugate was not dependent on nucleoside transporter for entering into the cells and this, in turn, reflecting potential implication of this conjugate in the therapy of transporter- deficient resistance cancer. Further, the cell cycle analysis showed that the sub-G1 (G0) apoptotic population was 46.6% and 60.6% for gemcitabine and PLGA gemcitabine conjugate, respectively. The conjugate produced remarkable decrease in mitochondrial membrane potential, a marker of apoptosis. In addition, there was a marked increase in PARP cleavage and P-H2AX expression with PLGA gemcitabine conjugate as compared to native gemcitabine indicating improved apoptotic activity. The findings demonstrated the potential of PLGA gemcitabine conjugate to improve clinical outcome of gemcitabine based chemotherapy of cancer.

Preparation, optimization and in vitro characterization of stearoyl-gemcitabine polymeric micelles: a comparison with its self-assembled nanoparticles

Although gemcitabine (Gem) constitutes first-line therapy for pancreatic cancer, its clinical outcome suffers from rapid metabolism and acquired drug resistance. To overcome its limitations, several lipophilic prodrugs including 4-(N)-stearoyl Gem (GemC18) have been studied for their efficacy over Gem. Herein, we aimed to prepare and characterize the GemC18-loaded poly(ethylene glycol)-poly(d,l-lactide) (PEG-PLA) polymeric micelles (PMs) as well as its self-assembled nanoparticles (NPs). A D-optimal design was also utilized to investigate the effects of formulation variables, namely initial drug/polymer ratio, total solid content, and the type of organic solvent on properties of GemC18-loaded PMs. The optimized formulation showed a particle size of about 120 nm, encapsulation efficiency >90%, and a sustained release behavior of the drug. Alternatively, the prodrug NPs were harvested in larger size (∼300 nm) and more negative zeta potential, but less chemical stability compared to the optimized PMs. In Panc-1 and AsPC-1 cell lines, both GemC18-loaded PMs and NPs were significantly more cytotoxic than GemC18 solution. Chiefly, they could effectively reduce the viability of Gem high-resistant AsPC-1 cells in culture, whereas the molar equivalent doses of Gem did not show any acceptable cytotoxicity. Thus, these results suggest a promising direction for alternative Gem delivery systems for future therapeutic applications.

Therapeutic modalities of squalenoyl nanocomposites in colon cancer: an ongoing search for improved efficacy

Drug delivery of combined cytotoxic and antivascular chemotherapies in multidrug nanoassemblies may represent an attractive way to improve the treatment of experimental cancers. Here we made the proof of concept of this approach on the experimental LS174-T human colon carcinoma xenograft nude mice model. Briefly, we have nanoprecipitated the anticancer compound gemcitabine conjugated with squalene (SQ-gem) together with isocombretastatin A-4 (isoCA-4), a new isomer of the antivascular combretastatin A-4 (CA-4). It was found that these molecules spontaneously self-assembled as stable nanoparticles (SQ-gem/isoCA-4 NAs) of ca. 142 nm in a surfactant-free aqueous solution. Cell culture viability tests and apoptosis assays showed that SQ-gem/isoCA-4 NAs displayed comparable antiproliferative and cytotoxic effects than those of the native gemcitabine or the mixtures of free gemcitabine with isoCA-4. Surprisingly, it was observed by confocal microscopy that the nanocomposites made of SQ-gem/isoCA-4 distributed intracellularly as intact nanoparticles whereas the SQ-gem nanoparticles remained localized onto the cell membrane. When used to deliver these combined chemotherapeutics to human colon cancer model, SQ-gem/isoCA-4 nanocomposites induced complete tumor regression (by 93%) and were found superior to all the other treatments, whereas the overall tolerance was better than the free drug treatments. This approach could be applied to other pairs of squalenoylated nanoassemblies with other non-water-soluble drugs, thus broadening the application of the "squalenoylation" concept in oncology.

Nanocarriers for antibiotics: a promising solution to treat intracellular bacterial infections

In the field of antibiotherapy, intracellular infections remain difficult to eradicate mainly due to the poor intracellular penetration of most of the commonly used antibiotics. Bacteria have quickly understood that their intracellular localisation allows them to be protected from the host immune system, but also from the action of antimicrobial agents. In addition, in most cases pathogens nestle in professional phagocytic cells, and can even use them as a 'Trojan horse' to induce a secondary site of infection thereby causing persistent or recurrent infections. Thus, new strategies had to be considered in order to counteract these problems. Amongst them, nanocarriers loaded with antibiotics represent a promising approach. Nowadays, it is possible to encapsulate, incorporate or even conjugate biologically active molecules into different families of nanocarriers such as liposomes or nanoparticles in order to deliver antibiotics intracellularly and hence to treat infections. This review gives an overview of the variety of nanocarriers developed to deliver antibiotics directly into infected cells.

Advances in the development of nucleoside and nucleotide analogues for cancer and viral diseases

Nucleoside analogues have been in clinical use for almost 50 years and have become cornerstones of treatment for patients with cancer or viral infections. The approval of several additional drugs over the past decade demonstrates that this family still possesses strong potential. Here, we review new nucleoside analogues and associated compounds that are currently in preclinical or clinical development for the treatment of cancer and viral infections, and that aim to provide increased response rates and reduced side effects. We also highlight the different approaches used in the development of these drugs and the potential of personalized therapy.

Advances in the development of nucleoside and nucleotide analogues for cancer and viral diseases

Nucleoside analogues have been in clinical use for almost 50 years and have become cornerstones of treatment for patients with cancer or viral infections. The approval of several additional drugs over the past decade demonstrates that this family still possesses strong potential. Here, we review new nucleoside analogues and associated compounds that are currently in preclinical or clinical development for the treatment of cancer and viral infections, and that aim to provide increased response rates and reduced side effects. We also highlight the different approaches used in the development of these drugs and the potential of personalized therapy.

Gemcitabine-loaded albumin nanospheres (GEM-ANPs) inhibit PANC-1 cells in vitro and in vivo

With the development of nanotechnology, special attention has been given to the nanomaterial application in tumor treatment. Here, a modified desolvation-cross-linking method was successfully applied to fabricate gemcitabine-loaded albumin nanospheres (GEM-ANPs), with 110 and 406 nm of mean diameter, respectively. The aim of this study was to assess the drug distribution, side effects, and antitumor activity of GEM-ANPs in vivo. The metabolic viability and flow cytometry analysis revealed that both GEM-ANPs, especially 406-nm GEM-ANPs, could effectively inhibit the metabolism and proliferation and promote the apoptosis of human pancreatic carcinoma (PANC-1) in vitro. Intravenous injection of 406-nm GEM-ANPs exhibited a significant increase of gemcitabine in the pancreas, liver, and spleen of Sprague-Dawley rats (p < 0.05). Moreover, no signs of toxic side effects analyzed by blood parameter changes were observed after 3 weeks of administration although a high dose (200 mg/kg) of GEM-ANPs were used. Additionally, in PANC-1-induced tumor mice, intravenous injection of 406-nm GEM-ANPs also could effectively reduce the tumor volume by comparison with free gemcitabine. With these findings, albumin nanosphere-loading approach might be efficacious to improve the antitumor activity of gemcitabine, and the efficacy is associated with the size of GEM-ANPs.

Synergistic targeting/prodrug strategies for intravesical drug delivery--lectin-modified PLGA microparticles enhance cytotoxicity of stearoyl gemcitabine by contact-dependent transfer

The direct access to the urothelial tissue via intravesical therapy has emerged as a promising means for reducing the high recurrence rate of bladder cancer. However, few advanced delivery concepts have so far been evaluated to overcome critical inherent efficacy limitations imposed by short exposure times, low tissue permeability, and extensive washout. This study reports on a novel strategy to enhance gemcitabine treatment impact on urothelial cells by combining a pharmacologically advantageous prodrug approach with the pharmacokinetic benefits of a glycan-targeted carrier system. The conversion of gemcitabine to its 4-(N)-stearoyl derivative (GEM-C₁₈) allowed for stable, homogeneous incorporation into PLGA microparticles (MP) without compromising intracellular drug activation. Fluorescence-labeled GEM-C₁₈-PLGA-MP were surface-functionalized with wheat germ agglutinin (WGA) or human serum albumin (HSA) to assess in direct comparison the impact of biorecognitive interaction on binding rate and anchoring stability. MP adhesion on urothelial cells of non-malignant origin (SV-HUC-1), and low- (5637) or high-grade (HT-1376) carcinoma was correlated to the resultant antiproliferative and antimetabolic effect in BrdU and XTT assays. More extensive and durable binding of the WGA-GEM-C₁₈-PLGA-MP induced a change in the pharmacological profile and substantially higher cytotoxicity, allowing for maximum response within the temporal restrictions of instillative administration (120 min). Mechanistically, a direct, contact-dependent transfer of stearoyl derivatives from the particle matrix to the urothelial membrane was found to account for this effect. With versatile options for future application, our results highlight the potential offered by the synergistic implementation of targeting/prodrug strategies in delivery systems tailored to the intravesical route.

Just getting into cells is not enough: mechanisms underlying 4-(N)-stearoyl gemcitabine solid lipid nanoparticle's ability to overcome gemcitabine resistance caused by RRM1 overexpression

Gemcitabine is a deoxycytidine analog that is widely used in the chemotherapy of many solid tumors. However, acquired tumor cell resistance often limits its use. Previously, we discovered that 4-(N)-stearoyl gemcitabine solid lipid nanoparticles (4-(N)-GemC18-SLNs) can overcome multiple acquired gemcitabine resistance mechanisms, including RRM1 overexpression. The present study was designed to elucidate the mechanisms underlying the 4-(N)-GemC18-SLNs' ability to overcome gemcitabine resistance. The 4-(N)-GemC18 in the 4-(N)-GemC18-SLNs entered tumor cells due to clathrin-mediated endocytosis of the 4-(N)-GemC18-SLNs into the lysosomes of the cells, whereas the 4-(N)-GemC18 alone in solution entered cells by diffusion. We substantiated that it is the way the 4-(N)-GemC18-SLNs deliver the 4-(N)-GemC18 into tumor cells that allows the gemcitabine hydrolyzed from the 4-(N)-GemC18 to be more efficiently converted into its active metabolite, gemcitabine triphosphate (dFdCTP), and thus more potent against gemcitabine-resistant tumor cells than 4-(N)-GemC18 or gemcitabine alone. Moreover, we also showed that the RRM1-overexpressing tumor cells were also cross-resistant to cytarabine, another nucleoside analog commonly used in cancer therapy, and 4-(N)-stearoyl cytarabine carried by solid lipid nanoparticles can also overcome the resistance. Therefore, formulating the long-chain fatty acid amide derivatives of nucleoside analogs into solid lipid nanoparticles may represent a platform technology to increase the antitumor activity of the nucleoside analogs and to overcome tumor cell resistance to them.