Pharmacokinetic and toxicity profile of a phosphorothioate oligonucleotide following inhalation delivery to lung in mice

Non-coding RNA-directed therapeutics in lung cancer: Delivery technologies and clinical applications

Lung cancer is one of the most aggressive and deadliest health threats. There has been an increasing interest in non-coding RNA (ncRNA) recently, especially in the areas of carcinogenesis and tumour progression. However, ncRNA-directed therapies are still encountering obstacles on their way to the clinic. In the present article, we provide an overview on the potential of targeting ncRNA in the treatment of lung cancer. Then, we discuss the delivery challenges and recent approaches enabling the delivery of ncRNA-directed therapies to the lung cancer cells, where we illuminate some advanced technologies including chemically-modified oligonucleotides, nuclear targeting, and three-dimensional in vitro models. Furthermore, advanced non-viral delivery systems recruiting nanoparticles, biomimetic delivery systems, and extracellular vesicles are also highlighted. Lastly, the challenges limiting the clinical trials on the therapeutic targeting of ncRNAs in lung cancer and future directions to tackle them are explored.

The safety and toxicity profile of SPL84, an inhaled antisense oligonucleotide for treatment of cystic fibrosis patients with the 3849 +10kb C->T mutation, supports a Phase 1/2 clinical study

INTRODUCTION

SPL84 is an inhaled antisense oligonucleotide (ASO) in development for the treatment of cystic fibrosis (CF) patients carrying the 3849 + 10kb C->T (3849) mutation. To support the initiation of the first clinical study, a full battery of safety and toxicology studies were performed.

RESEARCH DESIGN AND METHODS

SPL84 was administered by inhalation to mice and monkeys to determine the no observed adverse effect level (NOAEL) and establish sufficient safety margins for the starting clinical dose.

RESULTS

There were no preclinical safety findings with SPL84; no related clinical signs, nor any effect on body weight, food consumption, or clinical pathology. The microscopic changes in the lungs were regarded as non-adverse and reflected a normal clearance process for inhaled compounds. Systemic exposure in both species was low. The NOAEL for mice and monkeys was the highest administered dose in both species, resulting in safety margins ~ 40X the proposed starting clinical dose.

CONCLUSION

These successful results supported the initiation of a phase 1/2 clinical study of SPL84 (ongoing), assessing the safety, tolerability, and pharmacokinetics of a single ascending dose in healthy subjects to be followed by assessment of safety, tolerability, pharmacokinetics, and preliminary efficacy of multiple ascending doses in CF patients carrying the 3849 mutation.

Antisense Oligonucleotide Therapeutics for Cystic Fibrosis: Recent Developments and Perspectives

Antisense oligonucleotide (ASO) technology has become an attractive therapeutic modality for various diseases, including Mendelian disorders. ASOs can modulate the expression of a target gene by promoting mRNA degradation or changing pre-mRNA splicing, nonsense-mediated mRNA decay, or translation. Advances in medicinal chemistry and a deeper understanding of post-transcriptional mechanisms have led to the approval of several ASO drugs for diseases that had long lacked therapeutic options. For instance, an ASO drug called nusinersen became the first approved drug for spinal muscular atrophy, improving survival and the overall disease course. Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene cause cystic fibrosis (CF). Although Trikafta and other CFTR-modulation therapies benefit most CF patients, there is a significant unmet therapeutic need for a subset of CF patients. In this review, we introduce ASO therapies and their mechanisms of action, describe the opportunities and challenges for ASO therapeutics for CF, and discuss the current state and prospects of ASO therapies for CF.

Gene-specific nonsense-mediated mRNA decay targeting for cystic fibrosis therapy

Low CFTR mRNA expression due to nonsense-mediated mRNA decay (NMD) is a major hurdle in developing a therapy for cystic fibrosis (CF) caused by the W1282X mutation in the CFTR gene. CFTR-W1282X truncated protein retains partial function, so increasing its levels by inhibiting NMD of its mRNA will likely be beneficial. Because NMD regulates the normal expression of many genes, gene-specific stabilization of CFTR-W1282X mRNA expression is more desirable than general NMD inhibition. Synthetic antisense oligonucleotides (ASOs) designed to prevent binding of exon junction complexes (EJC) downstream of premature termination codons (PTCs) attenuate NMD in a gene-specific manner. We describe cocktails of three ASOs that specifically increase the expression of CFTR-W1282X mRNA and CFTR protein upon delivery into human bronchial epithelial cells. This treatment increases the CFTR-mediated chloride current. These results set the stage for clinical development of an allele-specific therapy for CF caused by the W1282X mutation.

The W1282X nonsense mutation in the CFTR gene causes cystic fibrosis by reducing its mRNA and functional protein levels. Here the authors developed antisense-oligonucleotide cocktails that restore CFTR protein function by gene-specific stabilization of CFTR mRNA.

Sustained inhibition of ENaC in CF: Potential RNA-based therapies for mutation-agnostic treatment

Disruption of the equilibrium between ion secretion and absorption processes by the airway epithelium is central to many muco-obstructive lung diseases including cystic fibrosis (CF). Besides correction of defective folding and function of CFTR, inhibition of amiloride-sensitive epithelia sodium channels (ENaC) has emerged as a bona fide therapeutic strategy to improve mucociliary clearance in patients with CF. The short half-life of amiloride-based ENaC blockers and hyperosmotic therapies have led to the development of novel RNA-based interventions for targeted and sustained reduction of ENaC expression and function in preclinical models of CF. This review summarizes the recent advances in RNA therapeutics targeting ENaC for mutation-agnostic treatment of CF.

Exon-skipping antisense oligonucleotides for cystic fibrosis therapy

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene cause cystic fibrosis (CF), and the CFTR-W1282X nonsense mutation causes a severe form of CF. Although Trikafta and other CFTR-modulation therapies benefit most CF patients, targeted therapy for patients with the W1282X mutation is lacking. The CFTR-W1282X protein has residual activity but is expressed at a very low level due to nonsense-mediated messenger RNA (mRNA) decay (NMD). NMD-suppression therapy and read-through therapy are actively being researched for CFTR nonsense mutants. NMD suppression could increase the mutant CFTR mRNA, and read-through therapies may increase the levels of full-length CFTR protein. However, these approaches have limitations and potential side effects: because the NMD machinery also regulates the expression of many normal mRNAs, broad inhibition of the pathway is not desirable, and read-through drugs are inefficient partly because the mutant mRNA template is subject to NMD. To bypass these issues, we pursued an exon-skipping antisense oligonucleotide (ASO) strategy to achieve gene-specific NMD evasion. A cocktail of two splice-site-targeting ASOs induced the expression of CFTR mRNA without the premature-termination-codon-containing exon 23 (CFTR-Δex23), which is an in-frame exon. Treatment of human bronchial epithelial cells with this cocktail of ASOs that target the splice sites flanking exon 23 results in efficient skipping of exon 23 and an increase in CFTR-Δex23 protein. The splice-switching ASO cocktail increases the CFTR-mediated chloride current in human bronchial epithelial cells. Our results set the stage for developing an allele-specific therapy for CF caused by the W1282X mutation.

A Phase Ib Open-Label, Multicenter Study of Inhaled DV281, a TLR9 Agonist, in Combination with Nivolumab in Patients with Advanced or Metastatic Non-small Cell Lung Cancer

PURPOSE

Although PD-(L)1 inhibitors have shown efficacy in advanced/metastatic non-small cell lung cancer (NSCLC), many patients do not respond to this treatment and more effective combinations with acceptable toxicities are needed. To assess the potential benefit of combining localized innate immune stimulation with checkpoint blockade, the TLR9 agonist DV281 was combined with nivolumab in a phase Ib study.

PATIENTS AND METHODS

Patients after one or two prior lines of systemic therapy were enrolled in a dose-escalation study with a 3+3 design. DV281 was administered via inhalation in five dose cohorts at 1 to 25 mg; nivolumab 240 mg was administered intravenously every 2 weeks. Safety, tolerability, pharmacodynamics, and response to treatment were assessed.

RESULTS

Twenty-six patients with advanced NSCLC enrolled. Baseline programmed death ligand 1 (PD-L1) expression was present in 16 patients (61.5%); 21 (80.7%) had received previous anti-PD-1/PD-L1. Thirteen patients (50%) had stable disease, nine (34.6%) had progressive disease, and four (15.4%) were not evaluable. Median duration of disease control was 124 days. Adverse events were seen in 16 patients (61.5%), mostly grade 1/2 chills, fatigue, flu-like symptoms, diarrhea, and rash; there was only one grade 3 adverse event (dyspnea). Pharmacodynamic assessment, measured by IFN- inducible gene expression, showed target engagement in all dose cohorts. Systemic pharmacodynamic responses plateaued in the 2 highest dose cohorts.

CONCLUSIONS

DV281 with nivolumab was well tolerated with target engagement observed at every dose. Pharmacodynamic advantages at doses above 10 mg were unclear. The long duration of disease control in 50% of patients suggests clinically relevant activity in this population of heavily pretreated patients.

Overcoming the challenges of tissue delivery for oligonucleotide therapeutics

Synthetic therapeutic oligonucleotides (STO) represent the third bonafide platform for drug discovery in the pharmaceutical industry after small molecule and protein therapeutics. So far, thirteen STOs have been approved by regulatory agencies and over one hundred of them are in different stages of clinical trials. STOs hybridize to their target RNA or DNA in cells via Watson-Crick base pairing to exert their pharmacological effects. This unique class of therapeutic agents has the potential to target genes and gene products that are considered undruggable by other therapeutic platforms. However, STOs must overcome several extracellular and intracellular obstacles to interact with their biological RNA targets inside cells. These obstacles include degradation by extracellular nucleases, scavenging by the reticuloendothelial system, filtration by the kidney, traversing the capillary endothelium to access the tissue interstitium, cell-surface receptor-mediated endocytic uptake, and escape from endolysosomal compartments to access the nuclear and/or cytoplasmic compartments where their targets reside. In this review, we present the recent advances in this field with a specific focus on antisense oligonucleotides (ASOs) and siRNA therapeutics.

BSTP Review of 12 Case Studies Discussing the Challenges, Pathology, Immunogenicity, and Mechanisms of Inhaled Biologics

The inhalation route is a relatively novel drug delivery route for biotherapeutics and, as a result, there is a paucity of published data and experience within the toxicology/pathology community. In recent years, findings arising in toxicology studies with inhaled biologics have provoked concern and regulatory challenges due, in part, to the lack of understanding of the expected pathology, mechanisms, and adversity induced by this mode of delivery. In this manuscript, the authors describe 12 case studies, comprising 18 toxicology studies, using a range of inhaled biotherapeutics (monoclonal antibodies, fragment antigen-binding antibodies, domain antibodies, therapeutic proteins/peptides, and an oligonucleotide) in rodents, nonhuman primates (NHPs), and the rabbit in subacute (1 week) to chronic (26 weeks) toxicology studies. Analysis of the data revealed that many of these molecules were associated with a characteristic pattern of toxicity with high levels of immunogenicity. Microscopic changes in the airways consisted of a predominantly lymphoid perivascular/peribronchiolar (PV/PB) mononuclear inflammatory cell (MIC) infiltrate, whereas changes in the terminal airways/alveoli were characterized by simple ("uncomplicated") increases in macrophages or inflammatory cell infiltrates ranging from mixed inflammatory cell infiltration to inflammation. The PV/PB MIC changes were considered most likely secondary to immunogenicity, whereas simple increases in alveolar macrophages were most likely secondary to clearance mechanisms. Alveolar inflammatory cell infiltrates and inflammation were likely induced by immune modulation or stimulation through pharmacologic effects on target biology or type III hypersensitivity (immune complex disease). Finally, a group of experts provide introductory thoughts regarding the adversity of inhaled biotherapeutics and the basis for reasonable differences of opinion that might arise between toxicologists, pathologists, and regulators.

Considerations for setting occupational exposure limits for novel pharmaceutical modalities

In order to develop new and effective medicines, pharmaceutical companies must be modality agnostic. As science reveals an enhanced understanding of biological processes, new therapeutic modalities are becoming important in developing breakthrough therapies to treat both rare and common diseases. As these new modalities progress, concern and uncertainty arise regarding their safe handling by the researchers developing them, employees manufacturing them and nurses administering them. This manuscript reviews the available literature for emerging modalities (including oligonucleotides, monoclonal antibodies, fusion proteins and bispecific antibodies, antibody-drug conjugates, peptides, vaccines, genetically modified organisms, and several others) and provides considerations for occupational health and safety-oriented hazard identification and risk assessments to enable timely, consistent and well-informed hazard identification, hazard communication and risk-management decisions. This manuscript also points out instances where historical exposure control banding systems may not be applicable (e.g. oncolytic viruses, biologics) and where other occupational exposure limit systems are more applicable (e.g. Biosafety Levels, Biologic Control Categories).

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Review of toxicology and pharmacology information for novel therapeutic modalities.

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Identification of occupational hazards associated with novel therapeutic modalities.

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Occupational hazards and exposure risks differ across pharmaceutical modalities.

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Occupational exposure control banding systems are not one size fits all.

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Banding system variations offer benefits while enabling proper exposure controls.

Antisense Oligonucleotides Targeting Jagged 1 Reduce House Dust Mite-induced Goblet Cell Metaplasia in the Adult Murine Lung

Goblet cell metaplasia, excessive mucus production, and inadequate mucus clearance accompany and exacerbate multiple chronic respiratory disorders, such as asthma and chronic obstructive pulmonary disease. Notch signaling plays a central role in controlling the fate of multiple cell types in the lung, including goblet cells. In the present study, we explored the therapeutic potential of modulating the Notch pathway in the adult murine lung using chemically modified antisense oligonucleotides (ASOs). To this end, we designed and characterized ASOs targeting the Notch receptors Notch1, Notch2, and Notch3 and the Notch ligands Jag1 (Jagged 1) and Jag2 (Jagged 2). Pulmonary delivery of ASOs in healthy mice or mice exposed to house dust mite, a commonly used mouse model of asthma, resulted in a significant reduction of the respective mRNAs in the lung. Furthermore, ASO-mediated knockdown of Jag1 or Notch2 in the lungs of healthy adult mice led to the downregulation of the club cell marker Scgb1a1 and the concomitant upregulation of the ciliated cell marker FoxJ1 (forkhead box J1). Similarly, ASO-mediated knockdown of Jag1 or Notch2 in the house dust mite disease model led to reduced goblet cell metaplasia and decreased mucus production. Because goblet cell metaplasia and excessive mucus secretion are a common basis for many lung pathologies, we propose that ASO-mediated inhibition of JAG1 could provide a novel therapeutic path for the treatment of multiple chronic respiratory diseases.

Preclinical development of the TLR9 agonist DV281 as an inhaled aerosolized immunotherapeutic for lung cancer: Pharmacological profile in mice, non-human primates, and human primary cells

CpG-motif-containing oligodeoxynucleotides (CpG-ODN) activate innate immunity through Toll-Like Receptor (TLR) 9 signaling and generate local immune responses when delivered directly to the lung. Herein we describe pharmacological studies in mice, cynomolgus monkeys, and in human primary cells which support the development of DV281, a C-class CpG-ODN, as an inhaled aerosolized immunotherapeutic for lung cancer to be combined with an inhibitor of the anti-programmed cell death protein 1 (PD‑1) immune checkpoint. In vitro, DV281 potently induced Interferon (IFN)‑α from monkey and human peripheral blood mononuclear cells (PBMCs), stimulated interleukin‑6 production and proliferation in human B cells, and induced TLR9-dependent cytokine responses from mouse splenocytes. Intranasal delivery of DV281 to mice led to substantial but transient cytokine and chemokine responses in the lung. Lung responses to repeated intranasal DV281 were partially to fully reversible 2 weeks after the final dose and were absent in TLR9-deficient mice. Single escalating doses of aerosolized DV281 in monkeys induced dose-dependent induction of IFN-regulated genes in bronchoalveolar lavage cells and blood. In a repeat-dose safety study in monkeys, inhaled DV281 was well-tolerated, and findings were mechanism of action-related and non-adverse. Co-culture of human PBMC with DV281 and anti-PD‑1 antibody did not augment cytokine or cellular proliferation responses compared to DV281 alone, indicating that the combination did not lead to dysregulated cytokine responses. These studies support clinical development of inhaled aerosolized DV281 as a combination therapy with anti-PD‑1 antibody for lung cancer immunotherapy.

Knockdown of Z Mutant Alpha-1 Antitrypsin In Vivo Using Modified DNA Antisense Oligonucleotides

Alpha-1 antitrypsin (AAT) is a serum protease inhibitor, mainly expressed in and secreted from hepatocytes, important for regulating neutrophil elastase activity among other proteases. Various mutations in AAT cause alpha-1 antitrypsin deficiency (AATD), a rare hereditary disorder that results in liver disease due to accumulation of AAT aggregates and lung disease from excessive neutrophil elastase activity. PiZ transgenic mice contain the human AAT genomic region harboring the most common AATD mutation, the Glu342Lys (Z) point mutation. These mice effectively recapitulate the liver disease exhibited in AATD patients, including AAT protein aggregates, hepatocyte death, and eventual liver fibrosis. Previously, we demonstrated that modified antisense oligonucleotides (ASOs) can dramatically reduce Z-AAT RNA and protein levels in PiZ mice enabling inhibition, prevention, and reversal of the associated liver disease. Here, we describe in detail usage of AAT-ASOs to knock down Z-AAT in PiZ mice with a focus on preparation and in vivo delivery of ASOs, as well as detailed workflows pertaining to the analysis of Z-AAT mRNA, plasma protein, and soluble/insoluble liver protein levels following ASO administration.

Inhaled ENaC antisense oligonucleotide ameliorates cystic fibrosis-like lung disease in mice

BACKGROUND

Epithelial sodium channel (ENaC, Scnn1) hyperactivity in the lung leads to airway surface dehydration and mucus accumulation in cystic fibrosis (CF) patients and in mice with CF-like lung disease.

METHODS

We identified several potent ENaC specific antisense oligonucleotides (ASOs) and tested them by inhalation in mouse models of CF-like lung disease.

RESULTS

The inhaled ASOs distributed into lung airway epithelial cells and decreased ENaC expression by inducing RNase H1-dependent degradation of the targeted Scnn1a mRNA. Aerosol delivered ENaC ASO down-regulated mucus marker expression and ameliorated goblet cell metaplasia, inflammation, and airway hyper-responsiveness. Lack of systemic activity of ASOs delivered via the aerosol route ensures the safety of this approach.

CONCLUSIONS

Our results demonstrate that antisense inhibition of ENaC in airway epithelial cells could be an effective and safe approach for the prevention and reversal of lung symptoms in CF and potentially other inflammatory diseases of the lung.

Clinical potential of oligonucleotide-based therapeutics in the respiratory system

The discovery of an ever-expanding plethora of coding and non-coding RNAs with nodal and causal roles in the regulation of lung physiology and disease is reinvigorating interest in the clinical utility of the oligonucleotide therapeutic class. This is strongly supported through recent advances in nucleic acids chemistry, synthetic oligonucleotide delivery and viral gene therapy that have succeeded in bringing to market at least three nucleic acid-based drugs. As a consequence, multiple new candidates such as RNA interference modulators, antisense, and splice switching compounds are now progressing through clinical evaluation. Here, manipulation of RNA for the treatment of lung disease is explored, with emphasis on robust pharmacological evidence aligned to the five pillars of drug development: exposure to the appropriate tissue, binding to the desired molecular target, evidence of the expected mode of action, activity in the relevant patient population and commercially viable value proposition.

Pharmacology of Antisense Drugs

Recent studies have led to a greater appreciation of the diverse roles RNAs play in maintaining normal cellular function and how they contribute to disease pathology, broadening the number of potential therapeutic targets. Antisense oligonucleotides are the most direct means to target RNA in a selective manner and have become an established platform technology for drug discovery. There are multiple molecular mechanisms by which antisense oligonucleotides can be used to modulate RNAs in cells, including promoting the degradation of the targeted RNA or modulating RNA function without degradation. Antisense drugs utilizing various antisense mechanisms are demonstrating therapeutic potential for the treatment of a broad variety of diseases. This review focuses on some of the advances that have taken place in translating antisense technology from the bench to the clinic.

Pharmacokinetic Profile and Acute Toxicological Properties of a Novel Radiosensitizer Cytosine-Phosphate-Guanosine Oligodeoxynucleotide 107 in Mice Following Intravenous and Orthotopic Administration

The synthetic cytosine-phosphate-guanosine oligodeoxynucleotide 107 (CpG ODN107) is a novel radiosensitizer for glioma treatment. However, the information related to its pharmacokinetics and toxicity remains unclear. Therefore, the plasma pharmacokinetics, distribution, elimination, and acute toxicity of CpG ODN107 in mice were investigated in the present experiments. The results from the liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay showed that the plasma elimination half-life (t1/2β) of CpG ODN107 in BALB/c mice varied slightly with the dose, and it was 0.65, 0.49, and 0.50 h at the intravenous doses of 2.5, 5, and 10 mg/kg, respectively. CpG ODN107 rapidly and widely distributed in organs/tissues, except the brain and testes. The highest concentrations were found in the liver (28.6% of the administered dose after 0.5 h) and the kidneys (5.7% of the administered dose after 1 h). CpG ODN107 (0.3, 3, and 30 μg/mL) could highly bind to human and mouse plasma proteins in vitro. CpG ODN107 in the forms of prototype was excreted in urine (1.79%) and feces (0.91%), and its shortened metabolites were excreted in urine (2.1%) and feces (2.2%) within the first 24 h. The mice in vivo optical image showed CpG ODN107 labeled with Alexa Fluor 680 fluorochrome (AF680) accumulated in the brain after orthotopic injection, eliminated very slowly, and excreted in urine compared with poly T labeled with AF680. The median lethal dose (LD50) of CpG ODN107 was 75.7 mg/kg for mice; this dose only could produce apparent spleen and liver damage, in line with the distribution features of CpG ODN. In conclusion, our present pharmacokinetic and toxicity investigation will provide helpful information to further pharmacodynamic and pharmacokinetic research of CpG ODN107 and other oligodeoxynucleotide drugs in the future.

Recommendations for safety pharmacology evaluations of oligonucleotide-based therapeutics

This document was prepared by the Safety Pharmacology Subcommittee of the Oligonucleotide Safety Working Group (OSWG), a group of industry and regulatory scientists involved in the development and regulation of therapeutic oligonucleotides. The mission of the Subcommittee was to develop scientific recommendations for the industry regarding the appropriate scope and strategies for safety pharmacology evaluations of oligonucleotides (ONs). These recommendations are the consensus opinion of the Subcommittee and do not necessarily reflect the current expectations of regulatory authorities. 1) Safety pharmacology testing, as described in the International Conference on Harmonisation (ICH) S7 guidance, is as applicable to ONs as it is to small molecule drugs and biotherapeutics. 2) Study design considerations for ONs are similar to those for other classes of drugs. In general, as with other therapeutics, studies should evaluate the drug product administered via the clinical route. Species selection should ideally consider relevance of the model with regard to the endpoints of interest, pharmacological responsiveness, and continuity with the nonclinical development program. 3) Evaluation of potential effects in the core battery (cardiovascular, central nervous, and respiratory systems) is recommended. In general: a. In vitro human ether-a-go-go-related gene (hERG) testing does not provide any specific value and is not warranted. b. Emphasis should be placed on in vivo evaluation of cardiovascular function, typically in nonhuman primates (NHPs). c. Due to the low level of concern, neurologic and respiratory function can be assessed concurrently with cardiovascular safety pharmacology evaluation in NHPs, within repeat-dose toxicity studies, or as stand-alone studies. In the latter case, rodents are most commonly used. 4) Other dedicated safety pharmacology studies, beyond the core battery, may have limited value for ONs. Although ONs can accumulate in the kidney and liver, evaluation of functional changes in these organs, as well as gastrointestinal (GI) and unintended "pro-inflammatory" effects, may be best evaluated during repeat-dose toxicity studies. Broad receptor- or ligand-binding profiling has not historically been informative for most ON subclasses, but may have value for investigative purposes.

Local and systemic tolerability of a 2'O-methoxyethyl antisense oligonucleotide targeting interleukin-4 receptor-α delivery by inhalation in mouse and monkey

Antisense oligonucleotides (ASOs) bind and facilitate degradation of RNA and inhibit protein expression in pathways not easily targeted with small molecules or antibodies. Interleukin (IL)-4 and IL-13 potentiate signaling through the shared IL-4 receptor-α (IL-4Rα) subunit of their receptors. ASO targeting of IL-4Rα mRNA in a mouse model of asthma led to attenuation of airway hyperactivity, demonstrating potential benefit in asthma patients. This study focused on tolerability of inhaled IL-4Rα-targeting ASOs. Toxicity studies were performed with mouse- (ISIS 23189) and human-specific (ISIS 369645) sequences administered by inhalation. Four week (monkey) or 13 week (mouse) repeat doses at levels of up to 15 mg/kg/exposure (exp) and 50 mg/kg/exp, respectively, demonstrated dose-dependent effects limited to increases in macrophage size and number in lung and tracheobronchial lymph nodes. The changes were largely non-specific, reflecting adaptive responses that occur during active exposure and deposition of ASO and other material in the lung. Reversibility was observed at a rate consistent with the kinetics of tissue clearance of ASO. Systemic bioavailability was minimal, and no systemic toxicity was observed at exposure levels appreciably above pharmacological doses and doses proposed for clinical trials.

Challenges for inhaled drug discovery and development: Induced alveolar macrophage responses

Alveolar macrophage (AM) responses are commonly induced in inhalation toxicology studies, typically being observed as an increase in number or a vacuolated 'foamy' morphology. Discriminating between adaptive AM responses and adverse events during nonclinical and clinical development is a major scientific challenge. When measuring and interpreting induced AM responses, an understanding of macrophage biology is essential; this includes 'sub-types' of AMs with different roles in health and disease and mechanisms of induction/resolution of AM responses to inhalation of pharmaceutical aerosols. In this context, emerging assay techniques, the utility of toxicokinetics and the requirement for new biomarkers are considered. Risk assessment for nonclinical toxicology findings and their translation to effects in humans is discussed from a scientific and regulatory perspective. At present, when apparently adaptive macrophage-only responses to inhaled investigational products are observed in nonclinical studies, this poses a challenge for risk assessment and an improved understanding of induced AM responses to inhaled pharmaceuticals is required.

Anti-tumor activity of CpG-ODN aerosol in mouse lung metastases

Studies in preclinical models have demonstrated the superior anti-tumor effect of CpG oligodeoxynucleotides (CpG-ODN) when administered at the tumor site rather than systemically. We evaluated the effect of aerosolized CpG-ODN on lung metastases in mice injected with immunogenic N202.1A mammary carcinoma cells or weakly immunogenic B16 melanoma cells. Upon reaching the bronchoalveolar space, aerosolized CpG-ODN activated a local immune response, as indicated by production of IL-12p40, IFN-γ and IL-1β and by recruitment and maturation of DC cells in bronchoalveolar lavage fluid of mice. Treatment with aerosolized CpG-ODN induced an expansion of CD4+ cells in lung and was more efficacious than systemic i.p. administration against experimental lung metastases of immunogenic N202.1A mammary carcinoma cells, whereas only i.p. delivery of CpG-ODN provided anti-tumor activity, which correlated with NK cell expansion in the lung, against lung metastases of the poorly immunogenic B16 melanoma. The inefficacy of aerosol therapy to induce NK expansion was related to the presence of immunosuppressive macrophages in B16 tumor-bearing lungs, as mice depleted of these cells by clodronate treatment responded to aerosol CpG-ODN through expansion of the NK cell population and significantly reduced numbers of lung metastases. Our results indicate that tumor immunogenicity and the tumor-induced immunosuppressive environment are critical factors to the success of CpG therapy in the lung, and point to the value of routine sampling of the lung immune environment in defining an optimal immunotherapeutic strategy.

Clinical expert panel on monitoring potential lung toxicity of inhaled oligonucleotides: consensus points and recommendations

Oligonucleotides (ONs) are an emerging class of drugs being developed for the treatment of a wide variety of diseases including the treatment of respiratory diseases by the inhalation route. As a class, their toxicity on human lungs has not been fully characterized, and predictive toxicity biomarkers have not been identified. To that end, identification of sensitive methods and biomarkers that can detect toxicity in humans before any long term and/or irreversible side effects occur would be helpful. In light of the public's greater interests, the Inhalation Subcommittee of the Oligonucleotide Safety Working Group (OSWG) held expert panel discussions focusing on the potential toxicity of inhaled ONs and assessing the strengths and weaknesses of different monitoring techniques for use during the clinical evaluation of inhaled ON candidates. This white paper summarizes the key discussions and captures the panelists' perspectives and recommendations which, we propose, could be used as a framework to guide both industry and regulatory scientists in future clinical research to characterize and monitor the short and long term lung response to inhaled ONs.

Oligonucleotides: a multi-targeted approach for the treatment of respiratory diseases

Reversing inflammatory lung disease remains the foremost challenge in treating respiratory diseases such as asthma and chronic obstructive pulmonary disease. Reducing (or modifying) the underlying inflammatory process with mono-target drugs has proven challenging. The era of designing ‘one target for one disease’ has evolved such that a growing body of evidence suggests a single drug that is capable of specifically targeting multiple targets and pathways would be better at arresting progression of these respiratory diseases and be an important advancement in current therapy. Oligonucleotide-based drugs represent an emerging class of drug candidates. Their properties, a broader range of targets over conventional small-molecule drugs and recent clinical proof-of-concept support their development as novel multi-targeting agents for the treatment of respiratory diseases.

Determination of therapeutic oligonucleotides using capillary gel electrophoresis

Oligonucleotides have developed into highly versatile and selective therapeutics over the past 20 years. More than five discrete mechanisms of action have been reported and more than 10 different chemical modifications have been used to extend their in vivo half-life and reduce their toxicity. Capillary gel electrophoresis (CGE) has been used extensively for the quantitative analysis of oligonucleotide therapeutics in both preclinical and clinical studies since the 1990s. The success of CGE is based on its extraordinary resolving power, which allows for the simultaneous determination of the parent drug and its metabolites. More recently, capillary gel electrophoresis has seen renewed interest with the emergence of replaceable gels with single-base resolving power and new capillary electrophoresis-mass spectrometry interfaces. This review discusses the bioanalysis of therapeutic oligonucleotides showing the evolution of the field over the past two decades leading to the current new approaches. Included in this review are topics such as different gel types, sample introduction modes, sample extraction procedures, separation conditions and detection methods used in CGE, along with discussions of the successes and limitations associated with each.

Targeting host E-selectin expression by antisense oligodeoxynucleotides as potential antiendotoxin therapy in vivo

This study sought to determine if antisense oligodeoxynucleotides would inhibit E-selectin expression, which mediates leukocyte adhesion on endothelial cells, otherwise induced by in vivo endotoxin challenge. Six antisense phosphorothioate oligodeoxynucleotides calculated to bind porcine E-selectin mRNA were tested in porcine aortic endothelial cells. One, ISIS9481, exerted significant inhibition of E-selectin expression induced by tumor necrosis factor-α + endotoxin [lipopolysaccharide (LPS)]. Pigs were challenged with LPS (10 μg/kg) and treated with ISIS9481 (10 mg/kg) (n = 6). Two control groups were used, an antisense inactive in porcine aortic endothelial cells (n = 6) and saline (n = 5), and were combined as control (C = 11). Control pigs challenged with LPS expressed E-selectin in heart, lung, kidneys, and liver, whereas antisense-treated pigs expressed little E-selectin in these tissues. Cardiovascular data indicated that antisense treatment attenuated pathophysiological alterations induced by LPS. Specifically, in control pigs, LPS reduced cardiac output 32% from baseline, increased pulmonary (+116%) and systemic vascular resistances (+16%), and generated neutropenia (from 51,000 at basal to 18,000 polymorphonuclear neutrophils (PMN)/μL after LPS). In antisense-treated pigs, cardiac output decreased only 18%, pulmonary vascular resistance remained unchanged, whereas systemic vascular resistance decreased compared with basal values (-37%). PMN counts remained at 45,000-54,000/μL at 3-4 hours after LPS. These data demonstrate that antisense oligodeoxynucleotides, designed and tested in vitro to interact with 1 gene product, can be developed as either therapeutics or experimental tools in vivo.

Antisense oligonucleotide pharmacokinetics and metabolism

BACKGROUND

The use of oligonucleotides as therapeutic agents has elicited a great deal of interest. Basic understanding and evaluation of the pharmacokinetic properties of oligonucleotides is foundational to their appropriate design and application.

OBJECTIVE

To review the primary pharmacokinetic properties that drive successful use and delivery of oligonucleotides.

METHODS

The primary data set available in the published literature for summarizing the pharmacokinetic properties of oligonucleotides exists for single strand phosphorothioate antisense oligonucleotides and their chimeric chemical modifications (second generation). Where possible, data from other classes of compounds are contrasted with this base class.

RESULTS/CONCLUSION

Although there are several different classes of oligonucleotides being developed as therapeutic agents, their pharmacokinetic properties by class are primarily a function of their backbone chemistry and the resulting chemical relationship to biological stability and plasma protein binding properties.

Emerging oligonucleotide therapies for asthma and chronic obstructive pulmonary disease

Chronic respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD) are disorders of the airways largely related to the presence of persistent inflammation. The approval of inhaled corticosteroids in the early 1970s pioneered a new age of therapy in treating chronic inflammatory airway diseases. This was the first time that an anti-inflammatory product was available to reduce the characteristic lung inflammation in airways and the associated obstruction, inflammation and hyper-responsiveness. Fast forward 40 years: corticosteroids are still an important therapeutic intervention; however, they exhibit limited use in moderate to severe asthma and COPD. Oligonucleotide therapies are an emerging class which include the antisense, the RNAi (siRNA and miRNA), the immunomodulatory, the aptamer and the decoy approaches. As these approaches are rather recent in the respiratory field, most are still early in development. Nevertheless, with limitations of current small molecule therapies and the hurdles faced with biologics, the use of oligonucleotides is relevant and the door is open to the development of this category of therapeutics. This review focuses on the major classes of oligonucleotides that are currently in late stage preclinical or clinical development for the treatment of asthma and COPD, and discusses the implications for their use as therapies for respiratory diseases.

Advantageous toxicity profile of inhaled antisense oligonucleotides following chronic dosing in non-human primates

TPI ASM8 and TPI 1100 are two products containing modified phosphorothioate antisense oligonucleotides (AONs), which are undergoing development for the treatment of asthma and chronic obstructive pulmonary disease (COPD), respectively. TPI ASM8 is comprised of two AONs, one targeting the human chemokine receptor 3 (CCR3) and the other targeting the common beta-chain of the IL-3/IL-5/GM-CSF receptors. TPI 1100 is also a dual-AON compound targeting the phosphodiesterase (PDE) 4 and 7 isotypes. For both products, the AONs are present in a 1:1 ratio by weight. Both products will be administered by inhalation to patients, and TPI ASM8 is currently undergoing Phase 2 clinical trials. As part of the safety assessment of both products, the toxicity and disposition (i.e., pharmacokinetics of the AON components in plasma and tissues) were investigated in 14-day inhalation studies in monkeys at doses ranging from 0.05 to 2.5mg/kg/day. Results indicated that both products were safe and well tolerated at all dose levels. Reversible treatment-related alterations were only observed at the high dose levels tested and were limited to changes in the respiratory tract which were characterized primarily by the presence of alveolar macrophages in the absence of a generalized inflammatory response. Plasma pharmacokinetic profiles showed very low plasma concentrations, and no plasma accumulation was observed after repeated doses. While significant amounts of the AONs of both TPI ASM8 and TPI 1100 were measured in trachea and lung, only limited amounts of the AONs could be measured in kidney and liver, which, in combination with the low plasma level data, is indicative of very low systemic exposure. Taken together, these results demonstrate that these two new AON-based products are safe and that delivery via the inhaled route achieves localized deposition in the pulmonary tract with very limited systemic exposure and reduced toxicity compared to other routes of AON administration.

Inhaled CD86 antisense oligonucleotide suppresses pulmonary inflammation and airway hyper-responsiveness in allergic mice

The B7-family molecule CD86, expressed on the surface of pulmonary and thoracic lymph node antigen-presenting cells, delivers essential costimulatory signals for T-cell activation in response to inhaled allergens. CD86-CD28 signaling is involved in priming allergen-specific T cells, but it is unclear whether these interactions play a role in coordinating memory T-helper 2 cell responses. In the ovalbumin (OVA)-induced mouse model of asthma, administration of CD86-specific antibody before systemic sensitization suppresses inhaled OVA-induced pulmonary inflammation and airway hyper-responsiveness (AHR). In previously OVA-sensitized mice, systemic and intranasal coadministration of CD86 antibody is required to produce these effects. To directly assess the importance of pulmonary CD86 expression in secondary immune responses to inhaled allergens, mice were sensitized and locally challenged with nebulized OVA before treatment with an inhaled aerosolized CD86 antisense oligonucleotide (ASO). CD86 ASO treatment suppressed OVA-induced up-regulation of CD86 protein expression on pulmonary dendritic cells and macrophages as well as on recruited eosinophils. Suppression of CD86 protein expression correlated with decreased methacholine-induced AHR, airway inflammation, and mucus production following rechallenge with inhaled OVA. CD86 ASO treatment reduced BAL eotaxin levels, but it did not reduce CD86 protein on cells in the draining lymph nodes of the lung, and it had no effect on serum IgE levels, suggesting a local and not a systemic effect. These results demonstrate that CD86 expression on pulmonary antigen-presenting cells plays a vital role in regulating pulmonary secondary immune responses and suggest that treatment with an inhaled CD86 ASO may have utility in asthma and other chronic inflammatory lung conditions.

Antisense approaches for inhibiting respiratory syncytial virus

Respiratory syncytial virus (RSV) continues as an emerging infectious disease not only among infants and children, but also for the immune-suppressed, hospitalised and the elderly. To date, ribavirin (Virazole, ICN Pharmaceuticals, Inc.) remains the only therapeutic agent approved for the treatment of RSV. However, its clinical benefits are small and occur only in a fraction of RSV-infected patients. The prophylactic administration of palivizumab (Synagis, MedImmune, Inc.) is problematic and costly and, therefore, only recommended for use in high-risk infants. Clearly, the need for an effective and safe drug remains high. This review discusses several different antisense approaches and compares them with traditional strategies, such as RSV-targeting antibodies and antivirals, as well as developments in vaccine research.

Inefficient cationic lipid-mediated siRNA and antisense oligonucleotide transfer to airway epithelial cells in vivo

BACKGROUND

The cationic lipid Genzyme lipid (GL) 67 is the current "gold-standard" for in vivo lung gene transfer. Here, we assessed, if GL67 mediated uptake of siRNAs and asODNs into airway epithelium in vivo.

METHODS

Anti-lacZ and ENaC (epithelial sodium channel) siRNA and asODN were complexed to GL67 and administered to the mouse airway epithelium in vivo Transfection efficiency and efficacy were assessed using real-time RT-PCR as well as through protein expression and functional studies. In parallel in vitro experiments were carried out to select the most efficient oligonucleotides.

RESULTS

In vitro, GL67 efficiently complexed asODNs and siRNAs, and both were stable in exhaled breath condensate. Importantly, during in vitro selection of functional siRNA and asODN we noted that asODNs accumulated rapidly in the nuclei of transfected cells, whereas siRNAs remained in the cytoplasm, a pattern consistent with their presumed site of action. Following in vivo lung transfection siRNAs were only visible in alveolar macrophages, whereas asODN also transfected alveolar epithelial cells, but no significant uptake into conducting airway epithelial cells was seen. SiRNAs and asODNs targeted to beta-galactosidase reduced betagal mRNA levels in the airway epithelium of K18-lacZ mice by 30% and 60%, respectively. However, this was insufficient to reduce protein expression. In an attempt to increase transfection efficiency of the airway epithelium, we increased contact time of siRNA and asODN using the in vivo mouse nose model. Although highly variable and inefficient, transfection of airway epithelium with asODN, but not siRNA, was now seen. As asODNs more effectively transfected nasal airway epithelial cells, we assessed the effect of asODN against ENaC, a potential therapeutic target in cystic fibrosis; no decrease in ENaC mRNA levels or function was detected.

CONCLUSION

This study suggests that although siRNAs and asODNs can be developed to inhibit gene expression in culture systems and certain organs in vivo, barriers to nucleic acid transfer in airway epithelial cells seen with large DNA molecules may also affect the efficiency of in vivo uptake of small nucleic acid molecules.

Biodistribution and metabolism of immunostimulatory oligodeoxynucleotide CPG 7909 in mouse and rat tissues following subcutaneous administration

To evaluate pharmacokinetics (PK) and biodistribution, CPG 7909, a 24-mer immunostimulatory fully phosphorothioated oligodeoxynucleotide (PS-ODN), was administered by subcutaneous injection at 2, 5 and 12.5mg/kg to mice and at 9mg/kg to rats. Parent compound and metabolites were isolated from plasma and tissues and quantified by capillary gel electrophoresis with UV detection (CGE-UV) and molecular masses were determined by matrix-assisted-laser-desorption-ionization time of flight detection (MALDI-TOF). An established method for PS-ODN isolation from plasma and tissue was modified to prevent oxidation of the phosphorothioate bonds during the extraction process, significantly increasing sensitivity in the subsequent MALDI-TOF analysis. Concentrations of CPG 7909 and metabolites were highest at the injection site (>600mg/kg at 4h). Maximal concentrations in local (draining) lymph nodes (LLN), kidney and liver were 10-15% of that at the injection site. The highest total amount of PS-ODN (percentage of administered dose) was found in the liver (32% at 4h), followed closely by the injection site (23% at 4h). Only very low levels of CPG 7909 and metabolites were found in plasma and only during the first hours. Metabolites identified by MALDI-TOF were similar for both species and all analyzed tissues, although the relative amounts of the different metabolites varied with tissue and over time. Degradation of CPG 7909 in vivo occurred predominantly by 3'exonucleases with additional cleavage by endonucleases.

Antisense oligonucleotide blockade of alpha 4 integrin prevents and reverses clinical symptoms in murine experimental autoimmune encephalomyelitis

We investigated the use of an antisense oligonucleotide (ASO) specific for mRNA of the alpha chain (CD49d) of mouse VLA-4 to down-regulate VLA-4 expression and alter central nervous system (CNS) inflammation. ISIS 17044 potently and specifically reduced CD49d mRNA and protein in cell lines and in ex-vivo-treated primary mouse T cells. When administered prophylactically or therapeutically, ISIS 17044 reduced the incidence and severity of paralytic symptoms in a model of experimental autoimmune encephalomyelitis (EAE). This was accompanied by a significant decrease in the number of VLA-4+ cells, CD4(+) T cells, and macrophages present in spinal cord white matter of EAE mice. ISIS 17044 was found to accumulate in lymphoid tissue of mice, and oligonucleotide was also detected in endothelial cells and macrophage-like cells in the CNS, apparently due to disruption of the blood-brain barrier during EAE. These results demonstrate the potential utility of systemically administered antisense oligonucleotides for the treatment of central nervous system inflammation.

Inhaled p38alpha mitogen-activated protein kinase antisense oligonucleotide attenuates asthma in mice

The p38 mitogen-activated protein kinase (MAPK) plays a critical role in the activation of inflammatory cells. Therefore, we investigated the antiinflammatory effects of a respirable p38alpha MAPK antisense oligonucleotide (p38alpha-ASO) in a mouse asthma model. A potent and selective p38alpha-ASO was characterized in vitro. Inhalation of aerosolized p38alpha-ASO using an aerosol chamber dosing system produced measurable lung deposition of ASO and significant reduction of ovalbumin (OVA-)-induced increases in total cells, eosinophils, and interleukin 4 (IL-4), IL-5, and IL-13 levels in bronchoalveolar lavage fluid, and dose-dependent inhibition of airway hyperresponsiveness in allergen-challenged mice. Furthermore, inhaled p38alpha-ASO markedly inhibited OVA-induced lung tissue eosinophilia and airway mucus hypersecretion. Quantitative polymerase chain reaction analysis of bronchoalveolar lavage fluid cells and peribronchial lymph node cells showed that p38alpha-ASO significantly reduced p38alpha MAPK mRNA expression. Nose-only aerosol exposure of mice verified the p38alpha-ASO-induced inhibition of OVA-induced pulmonary eosinophilia, mucus hypersecretion, and airway hyperresponsiveness. None of the effects of the p38alpha-ASO were produced by a six-base mismatched control oligonucleotide. These findings demonstrate antisense pharmacodynamic activity in the airways after aerosol delivery and suggest that a p38alpha MAPK ASO approach may have therapeutic potential for asthma and other inflammatory lung diseases.

Progress in antisense technology

Antisense technology exploits oligonucleotide analogs to bind to target RNAs via Watson-Crick hybridization. Once bound, the antisense agent either disables or induces the degradation of the target RNA. Antisense agents can also alter splicing. During the past decade, much has been learned about the basic mechanisms of antisense, the medicinal chemistry, and the pharmacologic, pharmacokinetic, and toxicologic properties of antisense molecules. Antisense technology has proven valuable in gene functionalization and target validation. With one drug marketed, Vitravenetm, and approximately 20 antisense drugs in clinical development, it appears that antisense drugs may prove important in the treatment of a wide range of diseases.

Progress in the delivery of therapeutic oligonucleotides: organ/cellular distribution and targeted delivery of oligonucleotides in vivo

Oligonucleotide (ODN) therapy is a powerful tool for modulation of gene expression in vivo. With advances in ODN chemistry and progress in formulation development, ODNs are becoming widely acceptable drugs. This review summarizes the current status and future trend of the in vivo application of ODN therapeutics, especially antisense ODNs. Here, we review the current understanding of the tissue/organ distribution and cellular uptake of ODN drugs administered parenterally or nonparenterally to intact animals. The problems and advantages inherent in the use of different delivery methods for the treatment of particular diseases are discussed in detail. Emphasis is placed on the most widely studied ODN analogs, the phosphorothioates (PS). Lessons learned from antisense PS studies have broad implications for ODN therapeutics in general.

Inhalation delivery of anticancer agents via HFA-based metered dose inhaler using methotrexate as a model drug

In the present study, the feasibility of delivering anticancer drugs via metered dose inhaler (MDI) was demonstrated using methotrexate (MTX) as a model anticancer drug. MDI formulations of MTX were prepared using hydrofluoroalkane-134a containing 0.67% MTX and 10% ethyl alcohol. The particle size of MTX was reduced by cryo milling with or without a surfactant (Pluronic F77) and the milled drug was employed for MDI formulations, which were subsequently evaluated for their medication delivery, mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD). Further, the efficacy of aerosolized MTX was evaluated by determining the in-vitro cytotoxicity of MTX against HL-60 cells using a six-stage viable impactor and the induction of apoptosis in HL-60 cells by acridine orange staining. Our results indicate that MTX aerosols having an MMAD varying between 2.2 and 3.2 microm (GSD 2.6-3.7) with a respirable fraction varying between 14.2 and 17.1% could be obtained by using MTX, which was cryo milled either alone or in combination with Pluronic F77. Exposure of HL-60 cells plated in third, fourth, fifth, and sixth stages of viable impactor to two actuations of MDI showed a cell kill of greater than 50%. Further, aerosolized MTX was found to induce apoptosis in HL-60 cells, as assessed by the morphological examination of the cells with fluorescent and confocal microscopy. Our results demonstrate that it is possible to deliver cytotoxic concentrations of MTX in an in vitro system simulating the lower respiratory tract (by using a six-stage viable impactor) via MDI and the cytotoxicity of the aerosolized MTX could be further improved by the optimization of the aerodynamic size.

Efficiency of antisense oligonucleotide drug discovery

The costs for discovering and developing new drugs continue to escalate, with current estimates that the average cost is more than $800 million for each new drug brought to the market. Pharmaceutical companies are under enormous pressure to increase their efficiency for bringing new drugs to the market by third-party payers, shareholders, and their patients, and at the same time regulators are placing increased demands on the industry. To be successful in the future, pharmaceutical companies must change how they discover and develop new drugs. So far, new technologies have done little to increase overall efficiency of the industry and have added additional costs. Platform technologies such as monoclonal antibodies and antisense oligonucleotides have the potential of reducing costs for discovery of new drugs, in that many of the steps required for traditional small molecules can be skipped or streamlined. Additionally the success of identifying a drug candidate is much higher with platform technologies compared to small molecule drugs. This review will highlight some of the efficiencies of antisense oligonucleotide drug discovery compared to traditional drugs and will point out some of the current limitations of the technology.

Discovery and development of respirable antisense therapeutics for asthma

Respirable antisense oligonucleotides (RASONs) represent a novel class of respiratory therapeutic molecules with the potential to specifically address the challenges posed by the successes of the Human Genome Program, namely, the need to rapidly identify the critical pulmonary disease-relevant drugable targets from the vast pool of 30,000-40,000 human genes and to discover and develop drugs that specifically attack these targets. We have shown that EPI-2010, a RASON targeting the adenosine A1 receptor, a G-protein coupled receptor that has been implicated in the regulation of three major determinants of asthma, can be delivered directly to the target disease tissue as an aerosol formulation. In vivo efficacy, absorption, distribution, metabolism, and excretion (ADME), and safety studies of inhaled EPI-2010 employing animal models of human asthma suggest that the RASON approach enables the specific delivery of efficacious, safe, and long-acting doses of phosphorothioate oligonucleotides to the respiratory tract. Moreover, these data indicate that RASONs truly have the potential to address the respiratory drug discovery bottleneck of the postgenomic era, that is, the ability to rapidly validate disease targets and develop pulmonary disease therapeutics for these validated targets.