Correlation of toxicity and pharmacokinetic properties of a phosphorothioate oligonucleotide designed to inhibit ICAM-1

Drug discovery and development scheme for liver-targeting bridged nucleic acid antisense oligonucleotides

Antisense oligonucleotides (ASOs) containing bridged nucleic acids (BNAs) have been proven to be very powerful. However, ensuring a reliable discovery and translational development scheme for this class of ASOs with wider therapeutic windows remains a fundamental challenge. We here demonstrate the robustness of our scheme in the context of the selection of ASOs having two different BNA chemistries (2,′4′-BNA/locked nucleic acid [LNA] and amido-bridged nucleic acid [AmNA]) targeting human proprotein convertase subtilisin/kexin type 9 (PCSK9). The scheme features a two-step process, including (1) a unique and sensitive in vitro screening approach, called Ca²⁺ enrichment of medium (CEM) transfection, and (2) a ligand-targeted drug delivery approach to better reach target tissues, averting unintended accumulation of ASOs. Using CEM screening, we identified a candidate ASO that shows >70% cholesterol-lowering action in monkeys. An N-acetylgalactosamine (GalNAc) ligand then was appended to the candidate ASO to further broaden the therapeutic margin by altering the molecule’s pharmacokinetics. The GalNAc conjugate, HsPCSK9-1811-LNA, was found to be at least ten times more potent in non-human primates (compared with the unconjugated counterpart), with reduced nephrotoxicity in rats. Overall, we successfully showed that our drug development scheme is better suited for selecting clinically relevant BNA-based ASOs, especially for the treatment of liver-associated diseases.

Targeting STAT3 with Proteolysis Targeting Chimeras and Next-Generation Antisense Oligonucleotides

STAT3 has been recognized for its key role in the progression of cancer, where it is frequently upregulated or constitutively hyperactivated, contributing to tumor cell proliferation, survival, and migration, as well as angiogenesis and suppression of antitumor immunity. Given the ubiquity of dysregulated STAT3 activity in cancer, it has long been considered a highly attractive target for the development of anticancer therapies. Efforts to target STAT3, however, have proven to be especially challenging, perhaps owing to the fact that transcription factors lack targetable enzymatic activity and have historically been considered "undruggable." Small-molecule inhibitors targeting STAT3 have been limited by insufficient selectivity and potency. More recently, therapeutic approaches that selectively target STAT3 protein for degradation have been developed, offering novel strategies that do not rely on inhibition of upstream pathways or direct competitive inhibition of the STAT3 protein. Here, we review these emerging approaches, including the development of STAT3 proteolysis targeting chimera agents, as well as preclinical and clinical studies of chemically stabilized antisense molecules, such as the clinical agent AZD9150. These therapeutic strategies may robustly reduce the cellular activity of oncogenic STAT3 and overcome the historical limitations of less selective small molecules.

Opportunities and challenges for the clinical translation of structured DNA assemblies as gene therapeutic delivery and vaccine vectors

Gene therapeutics including siRNAs, anti-sense oligos, messenger RNAs, and CRISPR ribonucleoprotein complexes offer unmet potential to treat over 7,000 known genetic diseases, as well as cancer, through targeted in vivo modulation of aberrant gene expression and immune cell activation. Compared with viral vectors, nonviral delivery vectors offer controlled immunogenicity and low manufacturing cost, yet suffer from limitations in toxicity, targeting, and transduction efficiency. Structured DNA assemblies fabricated using the principle of scaffolded DNA origami offer a new nonviral delivery vector with intrinsic, yet controllable immunostimulatory properties and virus-like spatial presentation of ligands and immunogens for cell-specific targeting, activation, and control over intracellular trafficking, in addition to low manufacturing cost. However, the relative utilities and limitations of these vectors must clearly be demonstrated in preclinical studies for their clinical potential to be realized. Here, we review the major capabilities, opportunities, and challenges we foresee in translating these next-generation delivery and vaccine vectors to the clinic. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Biology-Inspired Nanomaterials > Nucleic Acid-Based Structures Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Nucleic Acid Nanoparticles at a Crossroads of Vaccines and Immunotherapies

Vaccines and immunotherapies involve a variety of technologies and act through different mechanisms to achieve a common goal, which is to optimize the immune response against an antigen. The antigen could be a molecule expressed on a pathogen (e.g., a disease-causing bacterium, a virus or another microorganism), abnormal or damaged host cells (e.g., cancer cells), environmental agent (e.g., nicotine from a tobacco smoke), or an allergen (e.g., pollen or food protein). Immunogenic vaccines and therapies optimize the immune response to improve the eradication of the pathogen or damaged cells. In contrast, tolerogenic vaccines and therapies retrain or blunt the immune response to antigens, which are recognized by the immune system as harmful to the host. To optimize the immune response to either improve the immunogenicity or induce tolerance, researchers employ different routes of administration, antigen-delivery systems, and adjuvants. Nanocarriers and adjuvants are of particular interest to the fields of vaccines and immunotherapy as they allow for targeted delivery of the antigens and direct the immune response against these antigens in desirable direction (i.e., to either enhance immunogenicity or induce tolerance). Recently, nanoparticles gained particular attention as antigen carriers and adjuvants. This review focuses on a particular subclass of nanoparticles, which are made of nucleic acids, so-called nucleic acid nanoparticles or NANPs. Immunological properties of these novel materials and considerations for their clinical translation are discussed.

Toxicologic evaluation of repetitive 4-week intravenous injections of midkine antisense oligonucleotide nanoliposomes in rats

Midkine antisense oligonucleotide (MK-ASODN) nanoliposomes have previously been shown to have inhibitory activity against hepatocellular carcinoma growth. Herein we report the 4-week sub-chronic toxicity of MK-ASODN nanoliposomes in SD rats. The adverse effects included loss of body weight gain and food consumption, peri-rhinal bleeding, piloerection, peri-anal filth, and kidney, liver, spleen, thymus, lung, and injection site lesions at high doses. Macroscopic changes were observed in the kidneys of the high-dose group, accompanied by a variation in urine protein and white blood cells, blood urea nitrogen, and serum creatinine. The increased spleen and liver coefficient, and the variation in circulating white blood cells, lymphocytes, and eosinophils in the high-dose group demonstrated that inflammation was caused by MK-ASODN nanoliposomes and was consistent with the macroscopic changes in the spleen and liver. The main necropsy findings of the animals that died were macroscopic changes in the lung. No severe toxic effects or mortalities occurred in the low- and medium-dose groups. However, a No Adverse Effect Level (NOAEL) was not identified since there were changes in organs deemed to be adverse at all dose levels. Thus, the maximum tolerated dose of MK-ASODN nanoliposomes for rats was considered to be 6 mg/kg/day.

Mesyl phosphoramidate antisense oligonucleotides as an alternative to phosphorothioates with improved biochemical and biological properties

Forty years of research have shown that antisense oligonucleotides have great potential to target mRNAs of disease-associated genes and noncoding RNAs. Among the vast number of oligonucleotide backbone modifications, phosphorothioate modification is the most widely used in research and the clinic. However, along with their merits are notable drawbacks of phosphorothioate oligonucleotides, including decreased binding affinity to RNA, reduced specificity, and increased toxicity. Here we report the synthesis and in vitro evaluation of the DNA analog mesyl phosphoramidate oligonucleotide. This oligonucleotide type recruits RNase H and shows significant advantages over phosphorothioate in RNA affinity, nuclease stability, and specificity in inhibiting key processes of carcinogenesis. Thus, mesyl phosphoramidate oligonucleotides may be an attractive alternative to phosphorothioates.

Here we describe a DNA analog in which the mesyl (methanesulfonyl) phosphoramidate group is substituted for the natural phosphodiester group at each internucleotidic position. The oligomers show significant advantages over the often-used DNA phosphorothioates in RNA-binding affinity, nuclease stability, and specificity of their antisense action, which involves activation of cellular RNase H enzyme for hybridization-directed RNA cleavage. Biological activity of the oligonucleotide analog was demonstrated with respect to pro-oncogenic miR-21. A 22-nt anti–miR-21 mesyl phosphoramidate oligodeoxynucleotide specifically decreased the miR-21 level in melanoma B16 cells, induced apoptosis, reduced proliferation, and impeded migration of tumor cells, showing superiority over isosequential phosphorothioate oligodeoxynucleotide in the specificity of its biological effect. Lower overall toxicity compared with phosphorothioate and more efficient activation of RNase H are the key advantages of mesyl phosphoramidate oligonucleotides, which may represent a promising group of antisense therapeutic agents.

PEGylation of therapeutic oligonucletides: From linear to highly branched PEG architectures

PEGylation, the attachment of poly(ethylene glycol) (PEG), has been adopted to improve the pharmacokinetic properties of oligonucleotide therapeutics for nearly 30 years. Prior efforts mainly focused on the investigation of linear or slightly branched PEG having different molecular weights, terminal functional groups, and possible oligonucleotide sites for functionalization. Recent studies on highly branched PEG (including brush, star, and micellar structures) indicate superior properties in several areas including cellular uptake, gene regulation efficacy, reduction of side effects, and biodistribution. This review focuses on comparing the effects of PEG architecture on the physiochemical and biological properties of the PEGylated oligonucleotide.

Drug-induced Glomerulonephritis: The Spectre of Biotherapeutic and Antisense Oligonucleotide Immune Activation in the Kidney

Prevalence of immune-mediated glomerulonephritis has increased in preclinical toxicity studies, with more frequent use of biotherapeutic agents (especially antigenic humanized molecules) and antisense oligonucleotide (ASO) therapies. Immune complex disease affects a small number of study monkeys, often correlates with antidrug antibody (ADA) titers, and occurs at a dose that favors immune complex formation or impedes clearance. While preclinical glomerulonephritis often fails to correlate with evidence of glomerular or vascular injury in human clinical trials and is not considered predictive, additional animal investigative immunohistochemical work may be performed to substantiate evidence for immune complex pathogenesis. While ADA is most commonly encountered as a predisposing factor with biotherapeutic agents, complement activation may occur without circulating complexes, and other mechanisms of non-ADA immune-mediated glomerulonephritis have been observed including nonendogenous immune aggregates and immunoregulatory pharmacology. Although glomerulonephritis associated with oligonucleotide therapies has been noted occasionally in preclinical studies and more rarely with human patients, pathophysiologic mechanisms involved appear to be different between species and preclinical cases are not considered predictive for humans. ADA is not involved in oligonucleotide-associated cases, and complement fixation plays a more important role in monkeys. Recent screening of ASOs for proinflammatory activity appears to have decreased glomerulonephritis incidence preclinically.

RNA-Targeted Therapeutics

RNA-targeted therapies represent a platform for drug discovery involving chemically modified oligonucleotides, a wide range of cellular RNAs, and a novel target-binding motif, Watson-Crick base pairing. Numerous hurdles considered by many to be impassable have been overcome. Today, four RNA-targeted therapies are approved for commercial use for indications as diverse as Spinal Muscular Atrophy (SMA) and reduction of low-density lipoprotein cholesterol (LDL-C) and by routes of administration including subcutaneous, intravitreal, and intrathecal delivery. The technology is efficient and supports approaching "undruggable" targets. Three additional agents are progressing through registration, and more are in clinical development, representing several chemical and structural classes. Moreover, progress in understanding the molecular mechanisms by which these drugs work has led to steadily better clinical performance and a wide range of mechanisms that may be exploited for therapeutic purposes. Here we summarize the progress, future challenges, and opportunities for this drug discovery platform.

Aptamer Therapeutics in Cancer: Current and Future

Aptamer-related technologies represent a revolutionary advancement in the capacity to rapidly develop new classes of targeting ligands. Structurally distinct RNA and DNA oligonucleotides, aptamers mimic small, protein-binding molecules and exhibit high binding affinity and selectivity. Although their molecular weight is relatively small—approximately one-tenth that of monoclonal antibodies—their complex tertiary folded structures create sufficient recognition surface area for tight interaction with target molecules. Additionally, unlike antibodies, aptamers can be readily chemically synthesized and modified. In addition, aptamers’ long storage period and low immunogenicity are favorable properties for clinical utility. Due to their flexibility of chemical modification, aptamers are conjugated to other chemical entities including chemotherapeutic agents, siRNA, nanoparticles, and solid phase surfaces for therapeutic and diagnostic applications. However, as relatively small sized oligonucleotides, aptamers present several challenges for successful clinical translation. Their short plasma half-lives due to nuclease degradation and rapid renal excretion necessitate further structural modification of aptamers for clinical application. Since the US Food and Drug Administration (FDA) approval of the first aptamer drug, Macugen^® (pegaptanib), which treats wet-age-related macular degeneration, several aptamer therapeutics for oncology have followed and shown promise in pre-clinical models as well as clinical trials. This review discusses the advantages and challenges of aptamers and introduces therapeutic aptamers under investigation and in clinical trials for cancer treatments.

Oligonucleotide-based pharmaceuticals: Non-clinical and clinical safety signals and non-clinical testing strategies

Antisense oligonucleotides, short interfering RNAs (siRNAs) and aptamers are oligonucleotide-based pharmaceuticals with a promising role in targeted therapies. Currently, five oligonucleotide-based pharmaceuticals have achieved marketing authorization in Europe or USA and many more are undergoing clinical testing. However, several safety concerns have been raised in non-clinical and clinical studies. Oligonucleotides share properties with both chemical and biological pharmaceuticals and therefore they pose challenges also from the regulatory point of view. We have analyzed the safety data of oligonucleotides and evaluated the applicability of current non-clinical toxicological guidelines for assessing the safety of oligonucleotide-based pharmaceuticals. Oligonucleotide-based pharmaceuticals display a similar toxicological profile, exerting adverse effects on liver and kidney, evoking hematological alterations, as well as causing immunostimulation and prolonging the coagulation time. It is possible to extrapolate some of these effects from non-clinical studies to humans. However, evaluation strategies for genotoxicity testing of "non-natural" oligonucleotides should be revised. Additionally, the selective use of surrogates and prediction of clinical endpoints for non-clinically observed immunostimulation is complicated by its multiple potential manifestations, demanding improvements in the testing strategies. Utilizing more relevant and mechanistic-based approaches and taking better account of species differences, could possibly improve the prediction of relevant immunological/proinflammatory effects in humans.

E-selectin Targeting PEGylated-thioaptamer Prevents Breast Cancer Metastases

E-selectin is an adhesion molecule expressed on the luminal surface of inflamed blood vessels that mediates hematogenous metastasis by assisting shear-resistant adhesion of circulating tumor cells to the vessel surface under dynamic blood flow. Previously, we developed an E-selectin antagonistic thioaptamer (ESTA) for the prevention of hematogenous metastasis through the blockade of CD44^high breast cancer cells (BCa) adhesion to E-selectin-expressing premetastatic endothelial niche. The current study focuses on developing a PEGylated E-selectin targeting thioaptamer with improved pharmaceutical properties. A serial deletion of stem-loops reveled that loop-1 and -2 (ESTA7) are the minimally effective backbone structure necessary to obtain inhibition of the E-selectin/CD44 interaction and shear resistant adhesion of CD44^high BCa to E-selectin-expressing human endothelial cells (HMVECs) at a level equal to ESTA. Chemical conjugation of methoxy-polyethylene-glycol (PEG) at the sizes of 5 and 10 kDa did not interfere with ESTA7-mediated shear-resistant adhesion. However, in vivo study demonstrated that only 10 kDa PEG-conjugated ESTA7 (ESTA7-p10) retains the activity to inhibit metastases at a level equal to parental ESTA. Additionally, a single intravenous injection of ESTA7-p10 inhibited the development of lung, brain, and bone metastases of MDA-MB-231, through the blockade of E-selectin. Moreover, PEGylation led to an extension of elimination half-life and increase of AUC, resulting in superior inhibition of metastasis development compared to parental ESTA with a longer interval between dosing in a spontaneous metastasis model. Lastly, repeated intravenous administration of ESTA7-p10 was tolerated in mice, highlighting the potential prophylactic application of ESTA7-p10 for metastasis prevention.

Impact of dosing regimen of custirsen, an antisense oligonucleotide, on safety, tolerability and cardiac repolarization in healthy subjects

AIMS

Custirsen (OGX-011/TV-1011), a second-generation antisense oligonucleotide (ASO) that reduces clusterin production, is under investigation with chemotherapy in patients with solid tumours. Custirsen is associated with constitutional symptoms (CS) that may interfere with clinical pharmacology investigations, such as QT interval studies. Experience with other ASOs suggests NSAID premedication may ameliorate CS, but we observed suboptimal outcomes in healthy subjects given custirsen and NSAIDs. We sought to establish a custirsen regimen for future clinical pharmacology studies in healthy subjects.

METHODS

Subjects received custirsen (640 mg intravenously over 120 min) with dexamethasone premedication or increasing doses (320, 480, 640 mg over 6 days) of custirsen with dexamethasone premedication, then one full custirsen dose without premedication on day 8. Incidence/severity of adverse events (AEs) and extensive electrocardiogram readings were evaluated. Pharmacokinetic parameters were estimated.

RESULTS

AEs included CS, elevated transaminases and prolonged activated partial thromboplastin time (aPTT) that were predominantly grade 1/2. Administration of increasing custirsen doses and dexamethasone premedication reduced the incidence of CS associated with full dose custirsen. Transaminase elevation showed a dose-dependent effect (0% at days 2, 4, 27% at day 6) with the highest custirsen doses. Increasing doses of custirsen may have mitigated the severity but not incidence of aPTT prolongation. Neither regimen was associated with cardiac repolarization changes in QT values or concentration-effect analyses. The custirsen pharmacokinetic profile was consistent with previous experience.

CONCLUSION

Escalation of custirsen dose combined with dexamethasone premedication reduced CS associated with full dose custirsen and should be considered in future clinical pharmacology studies of custirsen.

Safety evaluation of intravenously administered mono-thioated aptamer against E-selectin in mice

The medical applications of aptamers have recently emerged. We developed an antagonistic thioaptamer (ESTA) against E-selectin. Previously, we showed that a single injection of ESTA at a dose of 100μg inhibits breast cancer metastasis in mice through the functional blockade of E-selectin. In the present study, we evaluated the safety of different doses of intravenously administered ESTA in single-dose acute and repeat-dose subacute studies in ICR mice. Our data indicated that intravenous administration of up to 500μg ESTA did not result in hematologic abnormality in either study. Additionally, intravenous injection of ESTA did not affect the levels of plasma cytokines (IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, GM-CSF, IFN-γ, and TNF-α) or complement split products (C3a and C5a) in either study. However, repeated injections of ESTA slightly increased plasma ALT and AST activities, in accordance with the appearance of small necrotic areas in the liver. In conclusion, our data demonstrated that intravenous administration of ESTA does not cause overt hematologic, organs, and immunologic responses under the experimental conditions.

Immunological and hematological toxicities challenging clinical translation of nucleic acid-based therapeutics

INTRODUCTION

Nucleic acid-based therapeutics (NATs) are proven agents in correcting disorders caused by gene mutations, as treatments against cancer, microbes and viruses, and as vaccine adjuvants. Although many traditional small molecule NATs have been approved for clinical use, commercialization of macromolecular NATs has been considerably slower, and only a few have successfully reached the market. Preclinical and clinical evaluation of macromolecular NATs has revealed many assorted challenges in immunotoxicity, hematotoxicity, pharmacokinetics (PKs), toxicology and formulation. Extensive review has been given to the PK and toxicological concerns of NATs including approaches designed to overcome these issues. Immunological and hematological issues are a commonly reported side effect of NAT treatment; however, literature exploring the mechanistic background of these effects is sparse.

AREAS COVERED

This review focuses on the immunomodulatory properties of various types of therapeutic nucleic acid concepts. The most commonly observed immunological and hematological toxicities are described for various NAT classes, with citations of how to circumvent these toxicities.

EXPERT OPINION

Although some success with overcoming immunological and hematological toxicities of NATs has been achieved in recent years, immunostimulation remains the main dose-limiting factor challenging clinical translation of these promising therapies. Novel delivery vehicles should be considered to overcome this challenge.

Scientific and Regulatory Policy Committee Points-to-consider Paper*: Drug-induced Vascular Injury Associated with Nonsmall Molecule Therapeutics in Preclinical Development: Part 2. Antisense Oligonucleotides

Drug-induced vascular injury (DIVI) is a recurrent challenge in the development of novel pharmaceutical agents. In recent years, DIVI has been occasionally observed in nonhuman primates given RNA-targeting therapeutics such as antisense oligonucleotide therapies (ASOs) during chronic toxicity studies. While DIVI in laboratory animal species has been well characterized for vasoactive small molecules, and immune-mediated responses against large molecule biotherapeutics have been well described, there is little published information regarding DIVI induced by ASOs to date. Preclinical DIVI findings in monkeys have caused considerable delays in development of promising new ASO therapies, because of the uncertainty about whether DIVI in preclinical studies is predictive of effects in humans, and the lack of robust biomarkers of DIVI. This review of DIVI discusses clinical and microscopic features of vasculitis in monkeys, their pathogenic mechanisms, and points to consider for the toxicologist and pathologist when confronted with ASO-related DIVI. Relevant examples of regulatory feedback are included to provide insight into risk assessment of ASO therapies.

Antisense oligonucleotide therapies: the promise and the challenges from a toxicologic pathologist's perspective

Many antisense oligonucleotides (ASOs) from several classes of molecules are currently in drug development. Despite over 20 years of pharmaceutical research, few ASOs have been marketed due to problems with clinical efficacy or preclinical toxicologic challenges. However, a number of recent developments have renewed interest in this class including the registration of mipomersen, the advent of successful screening strategies to eliminate more toxic molecules, and new understanding of the risks of off-target nucleotide binding and mitigation of potential off-target effects. Recent advances in backbone chemistries, conjugation to other moieties, and new delivery systems have allowed better tissue penetration, enhanced intracellular targeting, and less frequent dosing, resulting in fewer toxicities. While these new developments provide invigorated interest in these platforms, a few lingering challenges and preclinical/clinical toxicity issues remain to be completely resolved, including: (1) proinflammatory effects (vasculitis/inflammatory infiltrates); (2) nephrotoxicity and hepatotoxicity unrelated to lysosomal accumulation; and (3) thrombocytopenia. Recent investigative work by several laboratories have helped elucidate mechanisms for these issues, allowing a better understanding of the clinical relevance and implications of particular toxicities. It is important for toxicologists, pathologists, and regulatory reviewers to be familiar with new developments in the ASO field and their implications, as a greater number of new types of antisense molecules undergo preclinical toxicity testing.

Therapeutic antisense oligonucleotides against cancer: hurdling to the clinic

Under clinical development since the early 90's and with two successfully approved drugs (Fomivirsen and Mipomersen), oligonucleotide-based therapeutics has not yet delivered a clinical drug to the market in the cancer field. Whilst many pre-clinical data has been generated, a lack of understanding still exists on how to efficiently tackle all the different challenges presented for cancer targeting in a clinical setting. Namely, effective drug vectorization, careful choice of target gene or synergistic multi-gene targeting are surely decisive, while caution must be exerted to avoid potential toxic, often misleading off-target-effects. Here a brief overview will be given on the nucleic acid chemistry advances that established oligonucleotide technologies as a promising therapeutic alternative and ongoing cancer related clinical trials. Special attention will be given toward a perspective on the hurdles encountered specifically in the cancer field by this class of therapeutic oligonucleotides and a view on possible avenues for success is presented, with particular focus on the contribution from nanotechnology to the field.

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.

Species-specific inflammatory responses as a primary component for the development of glomerular lesions in mice and monkeys following chronic administration of a second-generation antisense oligonucleotide

Chronic administration of drisapersen, a 2'-OMe phosphorothioate antisense oligonucleotide (AON) to mice and monkeys resulted in renal tubular accumulation, with secondary tubular degeneration. Glomerulopathy occurred in both species with species-specific characteristics. Glomerular lesions in mice were characterized by progressive hyaline matrix accumulation, accompanied by the presence of renal amyloid and with subsequent papillary necrosis. Early changes involved glomerular endothelial hypertrophy and degeneration, but the chronic glomerular amyloid and hyaline alterations in mice appeared to be species specific. An immune-mediated mechanism for the glomerular lesions in mice was supported by early inflammatory changes including increased expression of inflammatory cytokines and other immunomodulatory genes within the renal cortex, increased stimulation of CD68 protein, and systemic elevation of monocyte chemotactic protein 1. In contrast, kidneys from monkeys given drisapersen chronically showed less severe glomerular changes characterized by increased mesangial and inflammatory cells, endothelial cell hypertrophy, and subepithelial and membranous electron-dense deposits, with ultrastructural and immunohistochemical characteristics of complement and complement-related fragments. Lesions in monkeys resembled typical features of C3 glomerulopathy, a condition described in man and experimental animals to be linked to dysregulation of the alternative complement pathway. Thus, inflammatory/immune mechanisms appear critical to glomerular injury with species-specific sensitivities for mouse and monkey. The lower observed proinflammatory activity in humans as compared to mice and monkeys may reflect a lower risk of glomerular injury in patients receiving AON therapy.

Antisense oligonucleotides on neurobehavior, respiratory, and cardiovascular function, and hERG channel current studies

INTRODUCTION

Safety Pharmacology studies were conducted in mouse, rat, and non-human primate to determine in vivo effects of antisense oligonucleotides (ASOs) on the central nervous system, respiratory system, and cardiovascular system. Effects on the hERG potassium channel current was evaluated in vitro.

METHODS

ASOs contained terminal 2'-O-methoxyethyl nucleotides, central deoxy nucleotides, and a phosphorothioate backbone. Neurobehavior was evaluated by Functional Observatory Battery in rodents. Respiratory function was directly measured in rodents by plethysmograph; respiratory rate and blood gases were measured in monkey. Basic cardiovascular endpoints were measured in rat; cardiovascular evaluation in monkey involved implanted telemetry units. In single and repeat dose studies ASOs were administered by subcutaneous injection at up to 300 mg/kg, 250 mg/kg, and 40 mg/kg in mouse, rat, or monkey, respectively. Assays were performed in HEK293 or CHO-K1 cells, stably transfected with hERG cDNA, at ASO concentrations of up to 300 μM.

RESULTS

No apparent effects were noted for respiratory or CNS function. Continuous monitoring of the cardiovascular system in monkey demonstrated no ASO-related changes in blood pressures, heart rate, or ECG and associated parameters (i.e., QRS duration). Specific assessment of the hERG potassium channel indicated no potential for actions on ventricular repolarization or modest effects only at excessive concentrations.

DISCUSSION

The absence of direct actions on neurobehavior and respiratory function associated with the administration of ASOs in safety pharmacology core battery studies is consistent with published toxicology studies. The combination of in vitro hERG studies and in vivo studies in rat and monkey are consistent with no direct actions by ASOs on cardiac cell function or electrical conduction at relevant concentrations and dose levels. Taken as a whole, dedicated studies focused on the safety pharmacology of specific organ systems do not appear to add significant data for interpretation of potential adverse effects. The need for dedicated studies for future ASOs in the same class is questionable, as a more encompassing data set can be collected in repeat dose and longer-term toxicology studies.

Acute kidney injury during therapy with an antisense oligonucleotide directed against PCSK9

Antisense oligonucleotides have been explored widely in clinical trials and generally are considered to be nontoxic for the kidney, even at high concentrations. We report a case of toxic acute tubular injury in a healthy 56-year-old female volunteer after a pharmacologically active dose of a locked nucleic acid antisense oligonucleotide was administered. The patient received 3 weekly subcutaneous doses of experimental drug SPC5001, an antisense oligonucleotide directed against PCSK9 (proprotein convertase subtilisin/kexin type 9) that is under investigation as an agent to reduce low-density lipoprotein cholesterol levels. Five days after the last dose, the patient's serum creatinine level increased from 0.81 mg/dL at baseline (corresponding to an estimated glomerular filtration rate [eGFR] of 78 mL/min/1.73 m(2)) to 2.67 mg/dL (eGFR, 20 mL/min/1.73 m(2)), and this increase coincided with the presence of white blood cells, granular casts, and minimal hematuria on urine microscopy. The patient's serum creatinine level peaked at 3.81 mg/dL (eGFR, 13 mL/min/1.73 m(2)) 1 week after the last oligonucleotide dose. Kidney biopsy showed multifocal tubular necrosis and signs of oligonucleotide accumulation. Upon conservative treatment, the patient's serum creatinine level gradually decreased and reached her baseline level 44 days after the last oligonucleotide was administered. The patient recovered fully and kidney function was normal at every follow-up visit.

Inhibition of selective adhesion molecules in treatment of inflammatory bowel disease

Lymphocyte infiltration into the intestinal tract in inflammatory bowel disease (IBD) is mediated by interaction between α4 integrin and its specific ligands. Development of monoclonal antibodies against α4 integrin allowed targeting of lymphocyte trafficking into the intestine as a novel therapeutic intervention. Natalizumab, vedolizumab, alicaforsen AJM300, rhuMAb β7, CCX282-B, and PF-00547,659 are few of monoclonal antibodies that have shown high promise in trials with the potential for more attractive benefit:risk ratio than currently available therapies. In this review, an attempt is made to underline the therapeutic potential and the safety of anti-adhesion molecule treatment in IBD.

Proliferative and nonproliferative lesions of the rat and mouse urinary system

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying lesions observed in the urinary tract of rats and mice. The standardized nomenclature of urinary tract lesions presented in this document is also available electronically on the Internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous developmental and aging lesions as well as those induced by exposure to test materials. A widely accepted and utilized international harmonization of nomenclature for urinary tract lesions in laboratory animals will decrease confusion among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists.

A locked nucleic acid oligonucleotide targeting microRNA 122 is well-tolerated in cynomolgus monkeys

MicroRNA 122 (miR-122) is liver specific, fine-tunes lipid metabolism, and is required for hepatitis C virus (HCV) abundance. Miravirsen, an oligonucleotide with locked nucleic acid, binds to miR-122, potently inhibiting its activity. We aimed at determining the safety of the miR-122 antagonism in vivo in 6 to 10 cynomolgus monkeys/group intravenously treated with a range of dose levels twice weekly for 4 weeks. Survival, body weights, clinical signs, and cardiovascular and ophthalmologic parameters were unaffected. Anticipated hypolipidemia due to the inhibition of miR-122 was observed in all treated animals. Only the highest dose level produced distinct transient prolongations of clotting times, slight alternative complement pathway activation, and a reversible increase of hepatic transaminases. Distribution half-life was 10-20 minutes, and accumulation was mainly in the kidney and liver with slow elimination. Microscopic examinations revealed granulated Kupffer cells and lymph node macrophages, cytoplasmic vacuolation in proximal renal tubules, and hepatocytes. The granules were most likely phagolysosomes containing miravirsen. A slightly increased incidence of hepatocyte apoptosis was observed in some monkeys given the highest dose; otherwise, there was no evidence of treatment-related degenerative changes in any organ. In conclusion, the maximal inhibition of miR-122 was associated with limited phenotypic changes, indicating that the clinical assessment of miravirsen as host factor antagonist for treatment of HCV infections is warranted.

Metabolism, pharmacokinetics, tissue distribution, and stability studies of the prodrug analog of an anti-hepatitis B virus dinucleoside phosphorothioate

The alkoxycarbonyloxy dinucleotide prodrug R(p), S(p)-2 is an orally bioavailable anti-hepatitis B virus agent. The compound is efficiently metabolized to the active dinucleoside phosphorothioate R(p), S(p)-1 by human liver microsomes and S9 fraction without cytochrome P450-mediated oxidation or conjugation. The conversion of R(p), S(p)-2 to R(p), S(p)-1 appears to be mediated by liver esterases, occurs in a stereospecific manner, and is consistent with our earlier reported studies of serum-mediated hydrolytic conversion of R(p), S(p)-2 to R(p), S(p)-1. However, further metabolism of R(p), S(p)-1 does not occur. The presence of a minor metabolite, the desulfurized product 10 was noted. The prodrug R(p), S(p)-2 was quite stable in simulated gastric fluid, whereas the active R(p), S(p)-1 had a half-life of <15 min. In simulated intestinal fluid, the prodrug 2 was fully converted to 1 in approximately 3 h, whereas 1 remained stable. To ascertain the tissue distribution of the prodrug 2 in rats, the synthesis of (35)S-labeled R(p), S(p)-2 was undertaken. Tissue distribution studies of orally and intravenously administered radiolabeled [(35)S]2 demonstrated that the radioactivity concentrates in the liver, with the highest liver/plasma ratio in the intravenous group at 1 h being 3.89 (females) and in the oral group at 1 h being 2.86 (males). The preferential distribution of the dinucleotide 1 and its prodrug 2 into liver may be attributed to the presence of nucleoside phosphorothioate backbone because phosphorothioate oligonucleotides also reveal a similar tissue distribution profile upon intravenous administration.

Chemical and mechanistic toxicology evaluation of exon skipping phosphorodiamidate morpholino oligomers in mdx mice

AVI-4658 is a phosphorodiamidate morpholino oligomer (PMO) designed to induce skipping of dystrophin exon 51 and restore its expression in patients with Duchenne muscular dystrophy (DMD). Preclinically, restoration of dystrophin in the dystrophic mdx mouse model requires skipping of exon 23, achieved with the mouse-specific PMO, AVI-4225. Herein, we report the potential toxicological consequences of exon skipping and dystrophin restoration in mdx mice using AVI-4225. We also evaluated the toxicological effects of AVI-4658 in both mdx and wild-type mice. In both studies, animals were dosed once weekly for 12 weeks up to the maximum feasible dose of 960 mg/kg per injection. Both AVI-4658 and AVI-4225 were well-tolerated at all doses. Findings in AVI-4225-treated animals were generally limited to mild renal tubular basophilia/vacuolation, without any significant changes in renal function and with evidence of reversing. No toxicity associated with the mechanism of action of AVI-4225 in a dystrophic animal was observed.

Repeat-dose toxicology evaluation in cynomolgus monkeys of AVI-4658, a phosphorodiamidate morpholino oligomer (PMO) drug for the treatment of duchenne muscular dystrophy

AVI-4658 is a phosphorodiamidate morpholino oligomer (PMO) drug designed to restore dystrophin expression in a subset of patients with Duchenne muscular dystrophy (DMD). Previous reports demonstrated this clinical proof-of-principle in patients with DMD following intramuscular injection of AVI-4658. This preclinical study evaluated the toxicity and toxicokinetic profile of AVI-4658 when administered either intravenously (IV) or subcutaneously (SC) to cynomolgus monkeys once weekly over 12 weeks, at doses up to the maximum feasible dose of 320 mg/kg per injection. No drug-related effects were noted on survival, clinical observations, body weight, food consumption, opthalmoscopic or electrocardiographic evaluations, hematology, clinical chemistry, urinalysis, organ weights, and macroscopic evaluations. Drug-related microscopic renal effects were dose-dependent, apparently reversible, and included basophilic granules (minimal), basophilic tubules (minimal to moderate), and tubular vacuolation (minimal to mild). These data establish the tolerability of AVI-4658 at doses up to and including the maximum feasible dose of 320 mg/kg by IV bolus or SC injection.

Rapid, cell-based toxicity screen of potentially therapeutic post-transcriptional gene silencing agents

Post-transcriptional gene silencing (PTGS) agents such as antisense, ribozymes and RNA interference (RNAi) have great potential as therapeutics for a variety of eye diseases including retinal and macular degenerations, glaucoma, corneal degenerations, inflammatory and viral conditions. Despite their great potential and over thirty years of academic and corporate research only a single PTGS agent is currently approved for human therapy for a single disease. Substantial challenges exist to achieving both efficacious and safe PTGS agents. Efficacy, as measured in specific target mRNA and protein knockdown, depends upon a number of complex factors including the identification of rare regions of target mRNA accessibility, cellular co-localization of the PTGS agent in sufficient concentration with the target mRNA, and stability of the PTGS agent in the target cells in which it is delivered or expressed. Safety is commonly measured by lack of cytotoxicity or other deleterious cellular responses in cells in which the PTGS agent is delivered or expressed. To relieve major bottlenecks in RNA drug discovery novel, efficient, inexpensive, and rapid tools are needed to facilitate lead identification of the most efficacious PTGS agent, rational optimization of efficacy of the lead agent, and lead agent safety determinations. We have developed a technological platform using cell culture expression systems that permits lead identification and efficacy optimization of PTGS agents against arbitrary disease target mRNAs under relatively high throughput conditions. Here, we extend the technology platform to include PTGS safety determinations in cultured human cells that are expected to represent the common cellular housekeeping microenvironment. We developed a high throughput screening (HTS) cytotoxicity assay in 96-well plate format based around the SYTOX Green dye which is excluded from healthy viable cells and becomes substantially fluorescent only after entering cells and binding to nuclear DNA. In this format we can test a number of PTGS agents for cellular toxicity relative to control elements. We also developed an HTS 96-well plate assay that allows us to assess the impact of any given PTGS agent on stimulating a variety of common cellular stress signaling pathways (e.g. CRE, SRE, AP-1, NFκB, Myc, and NFAT) that could indicate possible deleterious effects of PTGS agents either dependent or independent of base pairing complementarity with target mRNAs. To this end we exploited the secreted alkaline phosphatase (SEAP) Pathway Profiling System where the expression of the secreted reporter protein is coupled to transcriptional activation of a variety of promoter elements involved in common cell signaling pathways. We found that a variety of lead hammerhead ribozyme (hhRz) and short hairpin (shRNA) expression constructs did not exert cytotoxicity in human cells when driven by highly active RNA Pol-III promoters. We also found that most of the cell signaling pathways tested (CRE, SRE, Myc, and NFAT) did not significantly couple through upregulation to expression of the set of PTGS agents tested. AP-1 and NFκB upregulation both appear to couple to the expression of some PTGS agents which likely reflect the known properties of these pathways to be stimulated by abundant small structured RNAs.

Review of Continuing Education Course on Hemostasis

The continuing education course “Hemostasis” provided a comprehensive review of hemostasis and selected perturbations of the underlying processes as well as an assessment of hemostasis in animal models and preclinical testing environments. The session began with a review of the current state of understanding of hemostasis and how the waterfall or cascade of activation has transformed to the current cell-based, membrane-associated sequence of highly regulated events. The specific mechanisms of drug-induced thrombocytopenia were then presented, followed by a discussion of the relationships of coagulation and platelets in inflammation and cancer metastasis and platelet activity. Evaluation of hemostasis and platelet function in animals and especially in the environment of the contract research facility concluded the session.

Allele-selective inhibition of mutant huntingtin expression with antisense oligonucleotides targeting the expanded CAG repeat

Huntington's disease (HD) is a currently incurable neurodegenerative disease caused by the expansion of a CAG trinucleotide repeat within the huntingtin (HTT) gene. Therapeutic approaches include selectively inhibiting the expression of the mutated HTT allele while conserving function of the normal allele. We have evaluated a series of antisense oligonucleotides (ASOs) targeted to the expanded CAG repeat within HTT mRNA for their ability to selectively inhibit expression of mutant HTT protein. Several ASOs incorporating a variety of modifications, including bridged nucleic acids and phosphorothioate internucleotide linkages, exhibited allele-selective silencing in patient-derived fibroblasts. Allele-selective ASOs did not affect the expression of other CAG repeat-containing genes and selectivity was observed in cell lines containing minimal CAG repeat lengths representative of most HD patients. Allele-selective ASOs left HTT mRNA intact and did not support ribonuclease H activity in vitro. We observed cooperative binding of multiple ASO molecules to CAG repeat-containing HTT mRNA transcripts in vitro. These results are consistent with a mechanism involving inhibition at the level of translation. ASOs targeted to the CAG repeat of HTT provide a starting point for the development of oligonucleotide-based therapeutics that can inhibit gene expression with allelic discrimination in patients with HD.

Preclinical toxicity and toxicokinetics of GTI-2040, a phosphorothioate oligonucleotide targeting ribonucleotide reductase R2

PURPOSE

GTI-2040, a 20-mer phosphorothioate oligonucleotide, was designed to hybridize to the mRNA sequence of human ribonucleotide reductase R2. GTI-2040 has been shown to inhibit human cancer cell proliferation by downregulation of R2 expression in vitro and to significantly inhibit tumor growth in xenograft models of human cancer in mice. As part of the safety evaluation for human clinical trials, the toxicity and toxicokinetics of GTI-2040 were determined in Sprague-Dawley rats and rhesus monkeys.

METHODS

GTI-2040 was administered to rats at 2, 10, and 50 mg/kg/day by bolus intravenous injection every second day for 21 days with a 21-day recovery. In monkeys, an acute study was performed with single, escalating doses of GTI-2040 ranging from 10 to 80 mg/kg given as a 24-h continuous intravenous infusion. As well, a 21-day, continuous intravenous infusion study with GTI-2040 was conducted in monkeys at 2, 10, and 50 mg/kg/day, with a 3-week recovery. Blood sampling was done to measure GTI-2040 plasma concentrations, metabolites, and pharmacokinetic parameters, and tissues were collected to assess the distribution of GTI-2040 and/or metabolites.

RESULTS

The toxicities of GTI-2040 in both rats and monkeys were typical for the phosphorothioate oligonucleotide class of compounds. In monkeys, there was a dose-related increase in GTI-2040 plasma levels with concomitant increase in complement activation and prolongation of activated partial thromboplastin time. In both rats and monkeys, the tissues having the highest concentrations of GTI-2040 (kidney, liver, spleen) had the largest dose-related toxic effects. Adverse effects were diminished or absent in the recovery animals.

CONCLUSIONS

GTI-2040 was well tolerated when infused over 24 h at doses up to 80 mg/kg in monkeys. In rats and monkeys, GTI-2040 was reasonably well tolerated and showed reversible toxicities when administered at doses up to 50 mg/kg/day for 21 days. The no observed adverse effect dose level for GTI-2040 in both animal species was 2 mg/kg/day. There were no apparent sequence-specific effects related to the interaction of GTI-2040 with the R2 component of the mRNA expressing ribonucleotide reductase.

CpG and Non-CpG oligodeoxynucleotides induce differential proinflammatory gene expression profiles in liver and peripheral blood leukocytes in mice

Proinflammatory effects caused by oligodeoxynucleotides (ODN) include cytokine production, splenomegaly and infiltration of mononuclear cells into tissues. Presence of one or more CpG motifs in an ODN sequence confers potency for proinflammatory properties. The objective of this research was to characterize the proinflammatory effects produced by CpG containing ODN as compared to non-CpG ODN using gene array analysis. Female CD-1 mice were administered equipotent dose regimens of a CpG ODN (ISIS 12449, 4 mg/kg sc, single or repeat dose for 7 d) or a non-CpG ODN (ISIS 2302, 50 mg/kg sc, q2d for 1 or 3 weeks) and tissues (liver and peripheral blood leukocytes) were harvested for immunohistochemical analysis or gene array analysis. Splenomegaly, a marker of ODN-induced inflammation, was greatest (3-fold above control) with ISIS 12449 when given at multiple doses. Immunohistochemical staining identified mainly monocytes/macrophages as the immune cell infiltrates in the liver following ISIS 12449 or ISIS 2302 treatment. Gene analysis of liver tissue indicated enhanced expression of chemokines (MIG, MIP-2beta, MCP-1, IL-1beta, CCR3), cell surface markers (CD14, CD18, CD86, CD11c, P-selectin), intracellular markers (NF-kappaBp65, MyD88, Survivin) and markers of cell proliferation (PCNA, Ki-67, CD71) was produced with ISIS 12449 or ISIS 2302. Although CpG and non-CpG containing ODN produced similar gene expression profiles, notable differences were observed to suggest that their mechanisms of immune modulation are not completely overlapping. MIG and MIP 1beta were identified as potential biomarker for immune stimulation that may be used to further study the species specificity, sequence/structure dependence and time course of proinflammatory ODN and antisense inhibitors used as therapeutics.

Advances in antisense oligonucleotide development for target identification, validation, and as novel therapeutics

Antisense oligonucleotides (As-ODNs) are single stranded, synthetically prepared strands of deoxynucleotide sequences, usually 18–21 nucleotides in length, complementary to the mRNA sequence of the target gene. As-ODNs are able to selectively bind cognate mRNA sequences by sequence-specific hybridization. This results in cleavage or disablement of the mRNA and, thus, inhibits the expression of the target gene. The specificity of the As approach is based on the probability that, in the human genome, any sequence longer than a minimal number of nucleotides (nt), 13 for RNA and 17 for DNA, normally occurs only once. The potential applications of As-ODNs are numerous because mRNA is ubiquitous and is more accessible to manipulation than DNA. With the publication of the human genome sequence, it has become theoretically possible to inhibit mRNA of almost any gene by As-ODNs, in order to get a better understanding of gene function, investigate its role in disease pathology and to study novel therapeutic targets for the diseases caused by dysregulated gene expression. The conceptual simplicity, the availability of gene sequence information from the human genome, the inexpensive availability of synthetic oligonucleotides and the possibility of rational drug design makes As-ODNs powerful tools for target identification, validation and therapeutic intervention. In this review we discuss the latest developments in antisense oligonucleotide design, delivery, pharmacokinetics and potential side effects, as well as its uses in target identification and validation, and finally focus on the current developments of antisense oligonucleotides in therapeutic intervention in various diseases.

Comparing transfection efficiency and safety for antisense oligodeoxyribonucleotide between phospholipids-based microbubbles and liposomes

OBJECTIVE

To compare transfection efficiency and safety for antisense oligodeoxynucleotides (AS-ODNs) between two type of phospholipids-based vectors.

METHODS

An AS-ODNs sequence HA824 combined with luciferase reporter plasmid was used. Under low intensity ultrasound (US), a breast cancer cell line SK-BR-3 was exposed to different concentration of microbubbles and liposomes. Transfection efficiency was detected by fluorescence microscopy. Cell viability was verified by propidium iodide assay. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the inhibitory effect of HA824 on HER-2 expression at mRNA level. Atomic force microscopy (AFM) scanning techniques was employed to observe the change of membrane pore size.

RESULTS

AS-ODNs transfection efficiency showed an increasing tend with microbubble concentration, but not with liposome concentration. Maximum transfection efficiency with minimum cell viability was achieved under 2% microbubble concentration. Too strong sonoporation activity would enlarge membrane pores significantly and cause low cell viability.

CONCLUSION

US-mediated AS-ODNs transfection enhanced by phospholipids-based microbubbles represents an effective and safe avenue.

Oligodeoxynucleotide CpG 7909 Delivered as Intravenous Infusion Demonstrates Immunologic Modulation in Patients With Previously Treated Non-Hodgkin Lymphoma

Oligodeoxynucleotides containing CpG motifs (CpG ODN) can alter various immune cell subsets important in antibody therapy of malignancy. We undertook a phase I trial of CPG 7909 (also known as PF-3512676) in patients with previously treated lymphoma with the primary objective of evaluating safety across a range of doses, and secondary objectives of evaluating immunomodulatory effects and clinical effects. Twenty-three patients with previously treated non-Hodgkin lymphoma received up to 3 weekly 2-hour intravenous (IV) infusions of CPG ODN 7909 at dose levels 0.01 to 0.64 mg/kg. Evaluation of immunologic parameters and clinical endpoints occurred for 6 weeks. Infusion-related toxicity included grade 1 nausea, hypotension, and IV catheter discomfort. Serious adverse hematologic events observed more than once included anemia (2=Gr3, 2=Gr4), thrombocytopenia (4=Gr3), and neutropenia (2=Gr3), and were largely judged owing to progressive disease. Immunologic observations included: (1) The mean ratio of NK-cell concentrations compared with pretreatment at day 2 was 1.44 (95% CI=0.94-1.94) and at day 42 was 1.53 (95% CI=1.14-1.91); (2) NK activity generally increased in subjects; and (3) Antibody-dependent cellular cytotoxicity activity increased in select cohorts. No clinical responses were documented radiographically at day 42. Two subjects demonstrated late response. We conclude CpG 7909 can be safely given as a 2-hour IV infusion to patients with previously treated non-Hodgkin lymphoma at doses that have immunomodulatory effects.

Biodistribution of 68Ga-labelled phosphodiester, phosphorothioate, and 2'-O-methyl phosphodiester oligonucleotides in normal rats

Antisense oligonucleotides may hybridise with high selectivity to mRNA sequences allowing monitoring of gene expression or inhibition of the manifestation of altered genes inducing diseases. As part of the development of positron emission tomography methods, 17-mer antisense phosphodiester (PO), phosphorothioate (PS) and 2'-O-methyl phosphodiester (OMe) oligonucleotides specific for point mutationally activated human K-ras oncogene were labelled with 68Ga radionuclide via a chelator coupled to the probe. Hybridisation in solution and non-denaturing polyacrylamide gel electrophoresis (PAGE) with a subsequent exposure of the gels was performed to verify the hybridisation ability after labelling. The biodistribution was studied in male Sprague-Dawley rats by injecting 2MBq of 68Ga-oligonucleotides via the tail vein and measuring the organ radioactivity concentration after 20, 60 and 120 min or using whole-body autoradiography with 10 MBq 68Ga-oligonucleotide and 20 min incubation time. Control experiments were performed with 68GaCl3 and 68Ga-chelator complex. The results revealed that 68Ga-labelling did not change the hybridisation abilities of the oligonucleotides. The biodistribution pattern depended on the nature of the oligonucleotide backbone. Bone marrow, kidney, liver, spleen and urinary bladder were the five organs of highest uptake with each oligonucleotide. The PO accumulated highly in the liver, whereas high kidney uptake dominated the PS and OMe patterns. Intact PS and OMe were detected in plasma samples taken 20 and 60 min after injection. This study supplies a base for the further development of 68Ga-labelled oligonucleotides as pharmacokinetic tools and a potential future use for in vivo imaging of gene expression.

Effects of phosphorothioate oligodeoxynucleotide on hemoglobin-induced damage to intestinal mucosa

Some "blood substitutes," such as human diaspirin cross-linked hemoglobin DBBF-Hb, can damage the intestinal mucosa. This response may be due to release of free iron from Hb leading to production of reactive oxygen species (ROS). Phosphorothioate oligodeoxynucleotides can bind and sequester iron. Therefore experiments were performed to test whether PS-ODN, composed of ten consecutive cytidines "C-10," reduces Hb-induced ROS generation and damage in the mucosa. Anesthetized Sprague-Dawley rats (4-6 per group) were injected arterially with 1 mg C-10, followed two minutes later by 50 mg DBBF-Hb. The positive controls received only DBBF-Hb and the negative controls either saline or PS-ODN followed by saline. Either ROS formation was monitored using a fluorescence technique, or the intestine was fixed for microscopy after 8 or 30 min. Sixty villi per rat were assigned an epithelial integrity index (EI), ranging from 1 (intact) to 3 (some cell-cell and cell-basement membrane separation). Pretreatment with PS-ODN significantly exacerbated DBBF-Hb-induced ROS formation, and PS-ODN groups showed significantly more epithelial damage near Peyer's patches, (EI of 1.93 +/- 0.06 (SEM) at 8 minutes and 1.31 +/- 0.04 at thirty minutes), than the negative controls, (1.11 +/- 0.02 at both 8 and 30 minutes), or the positive controls (1.43 +/- 0.05 at 8 minutes and 1.20 +/- 0.03 at 30 minutes) (p < 0.05). However, mast cell degranulation, eosinophil accumulation and goblet cell secretion were significantly reduced in the DBBF-Hb groups pre-treated with PS-ODN. Thus, PS-ODN, although an iron chelator, can significantly enhance epithelial damage caused by DBBF-Hb in the rat intestinal mucosa near Peyer's patches, possibly by formation of the ferryl component of the hemoglobin.

Hybridisation of [76Br]-labelled antisense oligonucleotides to Chromogranin A mRNA verified by RT-PCR

Methods have been developed to label oligonucleotides (ODNs) in the 5'-position with (76)Br via a prosthetic group on a hexylamino-linker. The purpose of the study was to explore whether the labelling procedure would prevent specific hybridisation by using reverse transcription-polymerase chain reaction (RT-PCR) followed by sequencing of the PCR product. Antisense ODNs (30 mer, specific for rat Chromogranin A [CgA] mRNA) with phosphodiester (O-ODN) or phosphothioate (S-ODN) backbone, either unlabelled or labelled with (76)Br, served as one of the primers in individual PCR reactions. Using O-ODN as a primer, irrespective of being labelled or not, a selected 225-bp PCR fragment was successfully amplified. However, no amplification was obtained using S-ODN as a primer. The proper PCR products were only detected in the sample prepared from the adrenal gland, but not in that from the heart, liver or kidney. Autoradiographic recording of the gel, after gel electrophoresis, revealed radioactive signals corresponding to the amplified PCR products. The sequence of the PCR product matched the rat CgA mRNA sequence obtained from the EMBL database. RT-PCR is an attractive method to identify the selective binding of modified ODNs to target mRNA. This method confirmed that the labelling with (76)Br did not change the hybridisation ability of antisense O-ODN.

Antitumor effects of radioiodinated antisense oligonuclide mediated by VIP receptor

A 15-mer phosphorothioate antisense oligonuclide (ASON) complementary to the translation start region of the C-myc oncogene mRNA was radioiodinated to enhance its antitumor activity, and vasoactive intestinal peptide bound covalently polylysine (VIP-polylysine) was used as a carrier to deliver the oligonucleotide into VIP receptor-positive tumor cells. The antitumor activity of radioiodinated ASON conjugated to VIP-polylysine(VIP-131I-ASON) was investigated in athymic mice bearing HT29 tumor xenografts in comparison with unconjugated radioiodinated ASON(131I-ASON), unlabelled ASON (VIP-ASON) and scrambled oligonucleotide (VIP-131I-MON) conjugated to VIP-polylysine. Conjugation 125I-ASON to VIP-polylysine resulted in a 5.6-fold decrease in the plasma clearance and a 3.4-fold increase in tumor uptake of the radiopharmaceutical. Athymic mice bearing HT29 tumor xenografts were treated with 4 weekly doses of VIP-131I-ASON and the antitumor effects were assessed by use of the slope of the tumor growth curve. VIP-131I-ASON exhibited strong antitumor effects against HT29 xenografts, decreasing tumor growth rate 9.67-, 7.90-fold more effectively than 131I-ASON and VIP-ASON at equivalent doses of ASON. Conversely, 131I-ASON, VIP-ASON or VIP-131I-MON caused no significant effect compared with the normal saline. These data indicated that use of a VIP-polylysine carrier greatly increased HT29 tumor uptake of ASON and treatment with the VIP-131I-ASON complexes resulted in tumor growth delay in human colon cancer xenograft.

Potential of atelocollagen-mediated systemic antisense therapeutics for inflammatory disease

To study the possibility of using atelocollagen as an oligonucleotide (ODN) delivery carrier in vivo, the activity of formulated antisense ODN targeted against the intercellular adhesion molecule-1 (ICAM-1) mRNA was investigated in an allergic dermatitis model in mice. The allergic dermatitis was elicited in one ear of animals sensitized by treatment with 2,4-dinitrofluorobenzene. Antisense ODN was given to the animals as a single intravenous injection of formulation containing atelocollagen. Antisense activity was determined by measurement of ear thickness, histopathology, and immunohistochemistry 24 hr after the initiation of the dermatitis. Antisense activity was found to increase according to the concentration of atelocollagen in the formulation. The effect mediated by the ODN formulated with 0.05% atelocollagen was more than 50 times greater than that provided by ODN infusion, although the levels of ODN formulated with atelocollagen dropped below that of the 24-hr infusion group within 30 min. The formulated ODN could suppress inflammatory progression by treatment at 8 hr after the ear challenge when inflammation had already commenced at the challenged site. Moreover, antisense activity was noted even when the formulated ODN was injected 3 days before the initiation of inflammation. These data demonstrate that atelocollagen can enhance antisense activity remarkably and that the sustainable antisense activity mediated by the formulation of ODN with atelocollagen could completely change the strategy of antisense therapeutics.

How do glucocorticoids compare to oligo decoys as inhibitors of collagen synthesis and potential toxicity of these therapeutics?

This article demonstrates how glucocorticoids decrease collagen synthesis. The parameters used to assess procollagen synthesis in our laboratory will be compared to those used by others. This article will note all the pertinent literature on the molecular mechanisms of this down regulation of procollagen synthesis. For example, what are the effects of glucocorticoids at the levels of transcription and translation of collagen mRNAs? Finally, we will define a molecular mechanism to inhibit Type I collagen synthesis by decreasing the binding of the TGF-beta activator protein complex to the TGF-beta element in the distal promoter of the proalpha1 Type I collagen gene, preventing the 2:1 ratio of alpha1 to alpha2 chains in the processed Type I collagen molecule. We will next ask "How do sense oligo decoys decrease Type I collagen synthesis at the in vivo and at the cell levels?" In primary fibrotic cell culture, the double-stranded phosphorothioate oligodeoxynucleotide decoys were more effective than their sense single-stranded counterparts. The molecular mechanism for the decrease in Type I collagen synthesis is the same as glucocorticoids, that is by decreasing the binding of the TGF-beta activator protein complex to the TGF-beta element in the distal promoter of the proalpha1 Type I collagen gene for the transcription of the proalpha1 mRNAs. The reason for using sense oligo decoys as anti-fibrotic agents as compared to the anti-fibrotic glucocorticoids, is that presently marketed and FDA approved glucocorticoids have many untoward side effects which the sense oligo decoys do not have.

Oxetane modified, conformationally constrained, antisense oligodeoxyribonucleotides function efficiently as gene silencing molecules

Incorporation of nucleosides with novel base-constraining oxetane (OXE) modifications [oxetane, 1-(1',3'-O-anhydro-beta-d-psicofuranosyl nucleosides)] into antisense (AS) oligodeoxyribonucleotides (ODNs) should greatly improve the gene silencing efficiency of these molecules. This is because OXE modified bases provide nuclease protection to the natural backbone ODNs, can impart T(m) values similar to those predicted for RNA-RNA hybrids, and not only permit but also accelerate RNase H mediated catalytic activity. We tested this assumption in living cells by directly comparing the ability of OXE and phosphorothioate (PS) ODNs to target c-myb gene expression. The ODNs were targeted to two different sites within the c-myb mRNA. One site was chosen arbitrarily. The other was a 'rational' choice based on predicted hybridization accessibility after physical mapping with self-quenching reporter molecules (SQRM). The Myb mRNA and protein levels were equally diminished by OXE and PS ODNs, but the latter were delivered to cells with approximately six times greater efficiency, suggesting that OXE modified ODNs were more potent on a molar basis. The rationally targeted molecules demonstrated greater silencing efficiency than those directed to an arbitrarily chosen mRNA sequence. We conclude that rationally targeted, OXE modified ODNs, can function efficiently as gene silencing agents, and hypothesize that they will prove useful for therapeutic purposes.

Safety of CpG oligodeoxynucleotides in veterinary species

Bacterial DNA and synthetic oligodeoxynucleotides (ODNs) containing unmethylated CpG motifs in particular sequence contexts (CpG ODN) are recognized as a danger signal by the innate immune system of vertebrates. For this reason, CpG ODNs have a potential application as both an adjuvant and nonspecific immune modulator and are currently being evaluated in a number of human and veterinary clinical trials. Given their potent immunostimulatory activity, CpG ODNs could possibly induce adverse reactions. As all adjuvants and immune modulators must be nontoxic to meet safety requirements, it was essential to address the safety aspects of CpG ODNs. The current review summarizes experiments carried out to date to establish the safety of CpG ODNs in animals.

Fast and accurate determination of sites along the FUT2 in vitro transcript that are accessible to antisense oligonucleotides by application of secondary structure predictions and RNase H in combination with MALDI-TOF mass spectrometry

Alteration of gene expression by use of antisense oligonucleotides has considerable potential for therapeutic purposes and scientific studies. Although applied for almost 25 years, this technique is still associated with difficulties in finding antisense-effective regions along the target mRNA. This is mainly due to strong secondary structures preventing binding of antisense oligonucleotides and RNase H, playing a major role in antisense-mediated degradation of the mRNA. These difficulties make empirical testing of a large number of sequences complementary to various sites in the target mRNA a very lengthy and troublesome procedure. To overcome this problem, more recent strategies to find efficient antisense sites are based on secondary structure prediction and RNase H-dependent mechanisms. We were the first who directly combined these two strategies; antisense oligonucleotides complementary to predicted unpaired target mRNA regions were designed and hybridized to the corresponding RNAs. Incubation with RNase H led to cleavage of the RNA at the respective hybridization sites. Analysis of the RNA fragments by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, which has not been used in this context before, allowed exact determination of the cleavage site. Thus the technique described here is very promising when searching for effective antisense sites.

Targeted delivery system for antisense oligonucleotides: a novel experimental strategy for neuroblastoma treatment

Neuroblastoma (NB) is the most common neuroectoderma derived solid tumour of paediatric age. Since conventional treatments are often inefficient, novel therapeutic interventions are required. Among these, the use of antisense oligonucleotides (asODNs) as therapeutic antineoplastic agents has been recently investigated. Oligonucleotide in vivo applicability is impaired from their high sensitivity to cellular nuclease degradation. Encapsulating them within liposomes could nevertheless increase their stability. C-myb gene expression has been reported in several solid tumours of different embryonic origin, including NB, where it is linked to cell proliferation and/or differentiation. We performed a new technique to encapsulate c-myb antisense oligonucleotides within lipid particles. Liposomes resulting from this technique were called coated cationic liposomes (CCLs), since they were made up of a central core of a cationic phospholipid bound to myb-asODNs, and an outer shell of neutral lipids. A monoclonal antibody (mAb) specific for the neuroectoderma antigen disialoganglioside GD(2), has been covalently coupled to their external surface. The resulting anti-GD(2)-targeted CCLs showed high loading efficiency for the asODNs, small particle size and good stability. In vitro, they were able to deliver myb-asODNs selectively to GD(2)-positive NB cell lines more efficiently than non-targeted liposomes or free asODNs. Consequently, targeted formulations showed greater inhibition of cell proliferation than non-targeted formulations or free asODNs. Furthermore, we demonstrated that the inhibition of cell proliferation was dependent on the down-modulation of c-myb protein expression. Pharmacokinetic studies showed that these targeted liposomal formulations were long circulating in blood. Biodistribution studies presented differences between the free and the encapsulated myb-as ODN profiles, as well. While free myb-as ODNs are widely distributed (mainly liver, kidney and spleen) even after 30 min post-injection, myb-as ODN entrapped into CCL or anti-GD(2)-CCL presents only an accumulation in the spleen after 24 h. Future studies will be performed to evaluate the antitumour efficacy of the above formulations in animal models.