Development of RNAi technology for targeted therapy — A track of siRNA based agents to RNAi therapeutics

A biodistribution study of solid lipid-polyethyleneimine hybrid nanocarrier for cancer RNAi therapy

Solid lipid-polymer hybrid nanocarrier (LPN) was previously reported to achieve high siRNA transfection efficiency and induce sustained RNAi-based chemosensitizing effect at cellular level. In this study, our objectives were to evaluate the in vivo biodistribution of LPNs in a prostate cancer model and determine the factors that potentially affect tumor penetration by LPNs. The LPN formulation with the highest transfection efficiency (64%) and stability was selected for the study. Mice bearing tumors of PC-3Mcells were treated with LPNs labeled with IR780 or AF647-siRNA. Near infrared imaging showed that LPNs achieved favorable in vivo biodistribution with high tumor/low organ ratios. LPN accumulation was also observed in liver metastatic tissue. Result of extravasation study confirmed that encapsulated siRNA molecules were able to escape into the tumor tissue at the extravascular area. When LPN levels in large (volume>750mm³) and small (<500mm³) tumors were compared, no significant difference was observed. However, both docetaxel pretreatment (72hbefore LPN) and concurrent docetaxel treatment significantly enhanced the tumor LPN levels by 3.9- and 3.1-fold, respectively (both p<0.01). In conclusion, LPN is a promising carrier system to deliver RNAi therapy to solid malignancies that also receive chemotherapy.

RNAi mediated IL-6 in vitro knockdown in psoriasis skin model with topical siRNA delivery system based on liquid crystalline phase

Gene therapy by RNA interference (RNAi) is a post-transcriptional silencing process that can suppress the expression of a particular gene and it is a promising therapeutic approach for the treatment of many severe diseases, including cutaneous disorders. However, difficulties related to administration and body distribution limit the clinical use of small interfering RNA (siRNA) molecules. In this study, we proposed to use nanocarriers to enable siRNA application in the topical treatment of skin disorders. A siRNA nanodispersion based on liquid crystalline phase and composed of monoolein (MO), oleic acid (OA) and polyethylenimine (PEI) was developed and its physicochemical properties, efficiency of complexation and carrier/siRNA stability were assessed. Subsequently, cell viability, cellular uptake, in vitro skin irritation test using reconstructed human epidermis (RHE) and in vitro IL-6 knockdown in psoriasis skin model were evaluated. The results showed that the liquid crystalline nanodispersion is a promising topical delivery system for administration of siRNA, being able to overcome the limitations of the route of administration, as well those resulting from the characteristics of siRNA molecules. The formulation was effective at complexing the siRNA, presented high rate of cell uptake (∼90%), increased the skin penetration of siRNA in vitro, and did not cause skin irritation compared with Triton-X (a moderate irritant), resulting in a 4-fold higher viability of reconstructed human epidermis and a 15.6-fold lower release of IL-1α. A single treatment with the liquid crystalline nanodispersion carrying IL-6 siRNA for 6h was able to reduce the extracellular IL-6 levels by 3.3-fold compared with control treatment in psoriasis skin model. Therefore, liquid crystalline nanodispersion is a suitable nanocarrier for siRNA with therapeutic potential to suppress skin disease-specific genes. This study also highlights the applicability of reconstructed skin models in pharmaceutical field to evaluate the performance of delivery systems without the use of animal models.

Optimisation of vectorisation property: A comparative study for a secondary amphipathic peptide

RNA interference provides a powerful technology for specific gene silencing. Therapeutic applications of small interfering RNA (siRNA) however require efficient vehicles for stable complexation and intracellular delivery. In order to enhance their cell delivery, short amphipathic peptides called cell-penetrating peptides (CPPs) have been intensively developed for the last two decades. In this context, the secondary amphipathic peptide CADY has shown to form stable siRNA complexes and to improve their cellular uptake independent of the endosomal pathway. In the present work, we have described the parameters influencing CADY nanoparticle formation (buffers, excipients, presence of serum, etc.), and have followed in details the CPP:siRNA self-assembly. Once optimal conditions were determined, we have compared the ability of seven different CADY analogues to form siRNA-loaded nanoparticles compared to CADY:siRNA. First of all, we were able to show by biophysical methods that structural polymorphism (α-helix) is an important prerequisite for stable nanoparticle formation independently of occurring sequence mutations. Luciferase assays revealed that siRNA complexed to CADY-K (shorter version) shows better knock-down efficiency on Neuro2a-Luc(+) and B16-F10-Luc(+) cells compared to CADY:siRNA. Altogether, CADY-K is an ideal candidate for further application especially with regards to ex vivo or in vivo applications.

Identification and characterization of modified antisense oligonucleotides targeting DMPK in mice and nonhuman primates for the treatment of myotonic dystrophy type 1

Myotonic dystrophy type 1 (DM1) is the most common form of muscular dystrophy in adults. DM1 is caused by an expanded CTG repeat in the 3'-untranslated region of DMPK, the gene encoding dystrophia myotonica protein kinase (DMPK). Antisense oligonucleotides (ASOs) containing 2',4'-constrained ethyl-modified (cEt) residues exhibit a significantly increased RNA binding affinity and in vivo potency relative to those modified with other 2'-chemistries, which we speculated could translate to enhanced activity in extrahepatic tissues, such as muscle. Here, we describe the design and characterization of a cEt gapmer DMPK ASO (ISIS 486178), with potent activity in vitro and in vivo against mouse, monkey, and human DMPK. Systemic delivery of unformulated ISIS 486718 to wild-type mice decreased DMPK mRNA levels by up to 90% in liver and skeletal muscle. Similarly, treatment of either human DMPK transgenic mice or cynomolgus monkeys with ISIS 486178 led to up to 70% inhibition of DMPK in multiple skeletal muscles and ∼50% in cardiac muscle in both species. Importantly, inhibition of DMPK was well tolerated and was not associated with any skeletal muscle or cardiac toxicity. Also interesting was the demonstration that the inhibition of DMPK mRNA levels in muscle was maintained for up to 16 and 13 weeks post-treatment in mice and monkeys, respectively. These results demonstrate that cEt-modified ASOs show potent activity in skeletal muscle, and that this attractive therapeutic approach warrants further clinical investigation to inhibit the gain-of-function toxic RNA underlying the pathogenesis of DM1.

Harnessing the microRNA pathway for cardiac regeneration

Mounting evidence over the last few years has indicated that the rate of cardiomyocyte proliferation, and thus the extent of cardiac renewal, is under the control of the microRNA network. Several microRNAs (e.g. miR-1) regulate expansion of the cardiomyocyte pool and its terminal differentiation during the embryonic life; some not only promote cardiomyocyte proliferation but also their de-differentiation towards an embryonic cell phenotype (e.g. the miR-302/367 cluster); a few others are involved in the repression of cardiomyocyte proliferation occurring suddenly after birth (e.g. the miR-15 family); others again are not physiologically involved in the regulation of cardiomyocyte turnover, but nevertheless are able to promote cardiomyocyte proliferation and cardiac regeneration when delivered exogenously (e.g. miR-199a-3p). With a few exceptions, the molecular mechanisms underlying the pro-proliferative effect of these microRNAs, most of which appear to act at the level of already differentiated cardiomyocytes, remain to be thoroughly elucidated. The possibility of harnessing the miRNA network to achieve cardiac regeneration paves the way to exciting therapeutic applications. This could be achieved by either administering miRNA mimics or inhibitors, or transducing the heart with viral vectors expressing miRNA-encoding genes.

RNA Viruses and RNAi: Quasispecies Implications for Viral Escape

Due to high mutation rates, populations of RNA viruses exist as a collection of closely related mutants known as a quasispecies. A consequence of error-prone replication is the potential for rapid adaptation of RNA viruses when a selective pressure is applied, including host immune systems and antiviral drugs. RNA interference (RNAi) acts to inhibit protein synthesis by targeting specific mRNAs for degradation and this process has been developed to target RNA viruses, exhibiting their potential as a therapeutic against infections. However, viruses containing mutations conferring resistance to RNAi were isolated in nearly all cases, underlining the problems of rapid viral evolution. Thus, while promising, the use of RNAi in treating or preventing viral diseases remains fraught with the typical complications that result from high specificity of the target, as seen in other antiviral regimens.

Cyclodextrin mediated delivery of NF-κB and SRF siRNA reduces the invasion potential of prostate cancer cells in vitro

Prostate cancer is the most common cancer in men of the western world. To date, no effective treatment exists for metastatic prostate cancer and consequently, there is an urgent need to develop new and improved therapeutics. In recent years, the therapeutic potential of RNA interference (RNAi) has been extensively explored in a wide range of diseases including prostate cancer using numerous gene delivery vectors. The aims of this study were to investigate the ability of a non-viral modified cyclodextrin (CD) vector to deliver siRNA to the highly metastatic PC-3 prostate cancer cell line, to quantify the resulting knockdown of the two target genes (RelA and SRF) and to study the effects of the silencing on metastasis. Data from a Matrigel in vitro invasion assay indicated that the silencing of the target genes achieved by the CD vector resulted in significant reductions (P=0.0001) in the metastatic potential of these cells. As the silencing of these target genes was shown not to have a negative impact on cell viability, we hypothesise that the mechanism of invasion inhibition is due, in part, to the significant reduction observed (P⩽0.0001) in the level of pro-inflammatory cytokine, MMP9, which is known to be implicated in the metastasis of prostate cancer.

Expression of a single siRNA against a conserved region of NP gene strongly inhibits in vitro replication of different Influenza A virus strains of avian and swine origin

Influenza A virus is the principal agent responsible of the respiratory tract's infections in humans. Every year, highly pathogenic and infectious strains with new antigenic assets appear, making ineffective vaccines so far developed. The discovery of RNA interference (RNAi) opened the way to the progress of new promising drugs against Influenza A virus and also to the introduction of disease resistance traits in genetically modified animals. In this paper, we show that Madin-Darby Canine Kidney (MDCK) cell line expressing short hairpin RNAs (shRNAs) cassette, designed on a specific conserved region of the nucleoprotein (NP) viral genome, can strongly inhibit the viral replication of four viral strains sharing the target sequence, reducing the viral mRNA respectively to 2.5×10(-4), 7.5×10(-5), 1.7×10(-3), 1.9×10(-4) compared to the control, as assessed by real-time PCR. Moreover, we demonstrate that during the challenge with a viral strain bearing a single mismatch on the target sequence, although a weaker inhibition is observed, viral mRNA is still lowered down to 1.2×10(-3) folds in the shRNA-expressing clone compared to the control, indicating a broad potential use of this approach. In addition, we developed a highly predictive and fast screening test of siRNA sequences based on dual-luciferase assay, useful for the in vitro prediction of the potential effect of viral inhibition. In conclusion, these findings reveal new siRNA sequences able to inhibit Influenza A virus replication and provide a basis for the development of siRNAs as prophylaxis and therapy for influenza infection both in humans and animals.

Emerging drugs for the treatment of cervical cancer

INTRODUCTION

Worldwide, most cervical cancer (CC) patients require the use of drug therapy either adjuvant, concurrent with radiation or palliative.

AREAS COVERED

This review briefly discusses the current achievements in treating CC with an emphasis in emerging agents.

EXPERT OPINION

Concurrent cisplatin with radiation and lately, gemcitabine-cisplatin chemoradiation has resulted in small but significant improvements in the treatment of locally advanced and high-risk early-stage patients. So far, only antiangiogenic therapy with bevacizumab added to cisplatin chemoradiation has demonstrated safety and encouraging results in a Phase II study. In advanced disease, cisplatin doublets yield median survival rates not exceeding 14 months. The first Phase III study of bevacizumab, added to standard chemotherapy cisplatin- or non-cisplatin-containing doublet, has shown significant increase in both overall survival and progression-free survival. Further studies are needed before bevacizumab plus chemotherapy can be considered the standard of care for advanced disease. The characterization of the mutational landscape of CC and developments of novel targeted therapies may result in more effective and individualized treatments for CC. The potential efficacy of knocking down the key alterations in CC, E6 and E7 human papilloma virus oncoproteins must not be overlooked.

Gold-installed biostable nanocomplexes for tumor-targeted siRNA delivery in vivo

Biostable nanocomplexes, composed of gold-installed polyethyleneimine/siRNA complexes with a corona of PEGylated hyaluronic acid, have potential as a siRNA carrier for tumor-targeted therapy.

Dual MMP7-proximity-activated and folate receptor-targeted nanoparticles for siRNA delivery

A dual-targeted siRNA nanocarrier has been synthesized and validated that is selectively activated in environments where there is colocalization of two breast cancer hallmarks, elevated matrix metalloproteinase (MMP) activity and folate receptor overexpression. This siRNA nanocarrier is self-assembled from two polymers containing the same pH-responsive, endosomolytic core-forming block but varying hydrophilic, corona-forming blocks. The corona block of one polymer consists of a 2 kDa PEG attached to a terminal folic acid (FA); the second polymer contains a larger (Y-shaped, 20 kDa) PEG attached to the core block by a proximity-activated targeting (PAT), MMP7-cleavable peptide. In mixed micelle smart polymer nanoparticles (SPNs) formed from the FA- and PAT-based polymers, the proteolytically removable PEG on the PAT polymers shields nonspecific SPN interactions with cells or proteins. When the PAT element is cleaved within an MMP-rich environment, the PEG shielding is removed, exposing the underlying FA and making it accessible for folate receptor-mediated SPN uptake. Characterization of mixed micelles prepared from these two polymers revealed that uptake and siRNA knockdown bioactivity of a 50% FA/50% PAT formulation was dependent on both proteolytic activation and FA receptor engagement. MMP activation and delivery of this formulation to breast cancer cells expressing the FA receptor achieved greater than 50% protein-level knockdown of a model gene with undetectable cytotoxicity. This modular nanoparticle design represents a new paradigm in cell-selective siRNA delivery and allows for stoichiometric tuning of dual-targeting components to achieve superior targeting specificity.

New molecular targets against cervical cancer

Cervical cancer is the third most commonly diagnosed cancer worldwide and the fourth leading cause of cancer death in women. Major advances but still insufficient achievements in the treatment of locally advanced and high-risk early stage patients have occurred in the last decade with the incorporation of concurrent cisplatin with radiation and, lately, gemcitabine added to cisplatin chemoradiation. Despite a number of clinical studies incorporating molecular-targeted therapy as radiosensitizers being in progress, so far, only antiangiogenic therapy with bevacizumab added to cisplatin chemoradiation has demonstrated safety and shown encouraging results in a Phase II study. In advanced disease, cisplatin doublets do not have a great impact on the natural history of the disease with median survival rates not exceeding 13 months. The first Phase III study of bevacizumab, added to cisplatin or a non-cisplatin-containing doublet, showed significant increase in both overall survival and progression-free survival. Further studies are needed before bevacizumab plus chemotherapy can be considered the standard of care for advanced disease. Characterization of the mutational landscape of cervical cancer has already been initiated, indicating that, for now, few of these targetable alterations match with available agents. Progress in both the mutational landscape knowledge and developments of novel targeted therapies may result in more effective and individualized treatments for cervical cancer. The potential efficacy of knocking down the key alterations in cervical cancer - E6 and E7 human papillomavirus oncoproteins - must not be overlooked.

Cancer immunotherapy: nanodelivery approaches for immune cell targeting and tracking

Cancer is one of the most common diseases afflicting people globally. New therapeutic approaches are needed due to the complexity of cancer as a disease. Many current treatments are very toxic and have modest efficacy at best. Increased understanding of tumor biology and immunology has allowed the development of specific immunotherapies with minimal toxicity. It is important to highlight the performance of monoclonal antibodies, immune adjuvants, vaccines and cell-based treatments. Although these approaches have shown varying degrees of clinical efficacy, they illustrate the potential to develop new strategies. Targeted immunotherapy is being explored to overcome the heterogeneity of malignant cells and the immune suppression induced by both the tumor and its microenvironment. Nanodelivery strategies seek to minimize systemic exposure to target therapy to malignant tissue and cells. Intracellular penetration has been examined through the use of functionalized particulates. These nano-particulate associated medicines are being developed for use in imaging, diagnostics and cancer targeting. Although nano-particulates are inherently complex medicines, the ability to confer, at least in principle, different types of functionality allows for the plausible consideration these nanodelivery strategies can be exploited for use as combination medicines. The development of targeted nanodelivery systems in which therapeutic and imaging agents are merged into a single platform is an attractive strategy. Currently, several nanoplatform-based formulations, such as polymeric nanoparticles, micelles, liposomes and dendrimers are in preclinical and clinical stages of development. Herein, nanodelivery strategies presently investigated for cancer immunotherapy, cancer targeting mechanisms and nanocarrier functionalization methods will be described. We also intend to discuss the emerging nano-based approaches suitable to be used as imaging techniques and as cancer treatment options.