Assay, Purity, and Impurity Profile of Phosphorothioate Oligonucleotide Therapeutics by Ion Pair-HPLC-MS.

The relatively large molecular size, diastereoisomeric nature, and complex impurity profiles of therapeutic phosphorothioate oligonucleotides create significant analytical challenges for the quality control laboratory. To overcome the lack of selectivity inherent to traditional chromatographic approaches, an ion pair liquid chromatography-mass spectrometry (LCMS) method combining ultraviolet and mass spectrometry quantification was developed and validated for >35 different oligonucleotide drug substances and products, including several commercialized drugs. The selection of chromatographic and spectrometric conditions, data acquisition and processing, critical aspects of sample and buffer preparation and instrument maintenance, and results from method validation experiments are discussed.

The complexities of PKCα signaling in cancer.

Protein kinase C α (PKCα) is a ubiquitously expressed member of the PKC family of serine/threonine kinases with diverse functions in normal and neoplastic cells. Early studies identified anti-proliferative and differentiation-inducing functions for PKCα in some normal tissues (e.g., regenerating epithelia) and pro-proliferative effects in others (e.g., cells of the hematopoietic system, smooth muscle cells). Additional well documented roles of PKCα signaling in normal cells include regulation of the cytoskeleton, cell adhesion, and cell migration, and PKCα can function as a survival factor in many contexts. While a majority of tumors lose expression of PKCα, others display aberrant overexpression of the enzyme. Cancer-related mutations in PKCα are uncommon, but rare examples of driver mutations have been detected in certain cancer types (e. g., choroid gliomas). Here we review the role of PKCα in various cancers, describe mechanisms by which PKCα affects cancer-related cell functions, and discuss how the diverse functions of PKCα contribute to tumor suppressive and tumor promoting activities of the enzyme. We end the discussion by addressing mutations and expression of PKCα in tumors and the clinical relevance of these findings.

The Pharmacokinetics of 2'-O-Methyl Phosphorothioate Antisense Oligonucleotides: Experiences from Developing Exon Skipping Therapies for Duchenne Muscular Dystrophy.

Delivery to the target site and adversities related to off-target exposure have made the road to clinical success and approval of antisense oligonucleotide (AON) therapies challenging. Various classes of AONs have distinct chemical features and pharmacological properties. Understanding the similarities and differences in pharmacokinetics (PKs) among AON classes is important to make future development more efficient and may facilitate regulatory guidance of AON development programs. For the class of 2'-O-methyl phosphorothioate (2OMe PS) RNA AONs, most nonclinical and clinical PK data available today are derived from development of exon skipping therapies for Duchenne muscular dystrophy (DMD). While some publications have featured PK aspects of these AONs, no comprehensive overview is available to date. This article presents a detailed review of absorption, distribution, metabolism, and excretion of 2OMe PS AONs, compiled from publicly available data and previously unpublished internal data on drisapersen and related exon skipping candidates in preclinical species and DMD patients. Considerations regarding drug-drug interactions, toxicokinetics, and pharmacodynamics are also discussed. From the data presented, the picture emerges of consistent PK properties within the 2OMe PS class, predictable behavior across species, and a considerable overlap with other single-stranded PS AONs. A level of detail on muscle as a target tissue is provided, which was not previously available. Furthermore, muscle biopsy samples taken in DMD clinical trials allowed confirmation of the applicability of interspecies scaling approaches commonly applied in the absence of clinical target tissue data.

Immune cell trafficking and retention in inflammatory bowel disease: mechanistic insights and therapeutic advances.

Intestinal immune cell trafficking has been identified as a central event in the pathogenesis of inflammatory bowel diseases (IBD). Intensive research on different aspects of the immune mechanisms controlling and controlled by T cell trafficking and retention has led to the approval of the anti-α4ß7 antibody vedolizumab, the ongoing development of a number of further anti-trafficking agents (ATAs) such as the anti-ß7 antibody etrolizumab or the anti-MAdCAM-1 antibody ontamalimab and the identification of potential future targets like G-protein coupled receptor 15. However, several aspects of the biology of immune cell trafficking and regarding the mechanism of action of ATAs are still unclear, for example, which impact these compounds have on the trafficking of non-lymphocyte populations like monocytes and how precisely these therapies differ with regard to their effect on immune cell subpopulations. This review will summarise recent advances of basic science in the field of intestinal immune cell trafficking and discuss these findings with regard to different pharmacological approaches from a translational perspective.

Chemical modification of PS-ASO therapeutics reduces cellular protein-binding and improves the therapeutic index.

The molecular mechanisms of toxicity of chemically modified phosphorothioate antisense oligonucleotides (PS-ASOs) are not fully understood. Here, we report that toxic gapmer PS-ASOs containing modifications such as constrained ethyl (cEt), locked nucleic acid (LNA) and 2'-O-methoxyethyl (2'-MOE) bind many cellular proteins with high avidity, altering their function, localization and stability. We show that RNase H1-dependent delocalization of paraspeckle proteins to nucleoli is an early event in PS-ASO toxicity, followed by nucleolar stress, p53 activation and apoptotic cell death. Introduction of a single 2'-O-methyl (2'-OMe) modification at gap position 2 reduced protein-binding, substantially decreasing hepatotoxicity and improving the therapeutic index with minimal impairment of antisense activity. We validated the ability of this modification to generally mitigate PS-ASO toxicity with more than 300 sequences. Our findings will guide the design of PS-ASOs with optimal therapeutic profiles.

Past, Present and Future of Therapeutic Interventions Targeting Leukocyte Trafficking in Inflammatory Bowel Disease.

Studies in the 1990s using animal models of intestinal inflammation delineated the crucial molecules involved in leukocyte attraction and retention to the inflamed gut and associated lymphoid tissues. The first drug targeting leukocyte trafficking tested in inflammatory bowel diseases was the anti-ICAM-1 antisense oligonucleotide alicaforsen, showing only modest efficacy. Subsequently, the anti-α4 monoclonal antibody natalizumab proved efficacious for induction and maintenance of remission in Crohn's disease, but was associated with progressive multifocal leukoencephalopathy due to its ability to interfere with both α4ß1 and α4ß7 function. Later developments in this area took advantage of the fairly selective expression of MAdCAM-1 in the digestive organs, showing that vedolizumab, a more specific monoclonal antibody selectively blocking MAdCAM-1 binding to integrin α4ß7, was efficacious for induction and maintenance of remission in ulcerative colitis and Crohn's disease, and it was not associated with neurological complications. Currently, other drugs targeting the ß7 subunit, immunoglobulin superfamily molecules expressed on the endothelium, as well as blockade of lymphocyte recirculation in lymph nodes through modulation of sphingosine 1-phosphate receptors are under development. The potential use and risks of combined anti-trafficking therapy will be examined in this review.

Unlocking P(V): Reagents for chiral phosphorothioate synthesis.

Phosphorothioate nucleotides have emerged as powerful pharmacological substitutes of their native phosphodiester analogs with important translational applications in antisense oligonucleotide (ASO) therapeutics and cyclic dinucleotide (CDN) synthesis. Stereocontrolled installation of this chiral motif has long been hampered by the systemic use of phosphorus(III) [P(III)]-based reagent systems as the sole practical means of oligonucleotide assembly. A fundamentally different approach is described herein: the invention of a P(V)-based reagent platform for programmable, traceless, diastereoselective phosphorus-sulfur incorporation. The power of this reagent system is demonstrated through the robust and stereocontrolled synthesis of various nucleotidic architectures, including ASOs and CDNs, via an efficient, inexpensive, and operationally simple protocol.

Modulation of the tumor microenvironment by intratumoral administration of IMO-2125, a novel TLR9 agonist, for cancer immunotherapy.

The objective of cancer immunotherapy is to prime the host's immune system to recognize and attack malignant tumor cells. IMO­2125, a Toll­like receptor 9 (TLR9) agonist, exhibited potent antitumor effects in the murine syngeneic A20 lymphoma and the CT26 colon carcinoma models. IMO­2125 exhibited superior A20 antitumor activity when injected intratumorally (i.t.) compared with equivalent subcutaneous doses. In mice bearing dual CT26 grafts, the i.t. injection of right flank tumors elicited infiltration of cluster of differentiation (CD)3+ T lymphocytes into tumors, resulting in the regression of injected and uninjected left flank tumors. Depletion of CD8+, but not CD4+, T­cells abrogated the IMO­2125­mediated antitumor response, suggesting that CD8+ lymphocytes are required for the antitumor activity. In mice harboring right flank CT26 and left flank ß­galactosidase (ß­gal)­expressing CT26.CL25 grafts, the i.t. administration of IMO­2125 to the CT26 graft resulted in potent and dose­dependent antitumor activity against the two grafts. Splenic T­cells isolated from these mice responded to AH1 antigen (present in the two tumors) and ß­gal antigen (present only in CT26.CL25) in an interferon γ enzyme­linked immunospot assay, suggesting the clonal expansion of T­cells directed against antigens from the two tumors. Mice with ablated CT26 tumors by previous IMO­2125 treatment rejected re­implanted CT26 tumor cells, but not A20 tumor cells, demonstrating that the initial IMO­2125 treatment created a long­lived tumor­specific immune memory of CT26 antigens. A quantitative increase in CD3+ T lymphocytes in injected A20 tumors and an upregulation of selected checkpoint genes, including indoleamine 2,3­dioxygenase (IDO)­1, IDO­2, programmed cell death protein-1 (PD-1); programmed cell death protein ligand 1 (PD-L1), carcinoembryonic antigen­related cell adhesion molecule 1, tumor necrosis factor receptor superfamily member 4 (OX40), OX40 ligand, T­cell immunoglobulin and mucin­domain­containing 3 protein, lymphocyte­activation gene 3, cytotoxic T­lymphocyte­associated protein 4, were observed following IMO­2125 treatment. IMO­2125 also increased immune checkpoint gene expression in injected and uninjected contralateral CT26 tumors, suggesting that the co­administration of anti­CTLA­4, anti­PD­1 or anti­PD­L1 therapies with IMO­2125 may provide additional therapeutic efficacy.

Targeting Endothelial Ligands: ICAM-1/alicaforsen, MAdCAM-1.

Specific blockade of the endothelial ligands intercellular adhesion molecule-1 [ICAM-1] and mucosal addressin cell adhesion molecule [MAdCAM] involved in leukocyte recruitment to the site of inflammation as therapeutic targets in inflammatory bowel disease [IBD] has been recognized from their overexpression in the inflamed mucosa and successful intervention based on these ligands in preclinical animal models. Interventions to target ICAM-1 in human IBD are confined to the ICAM-1 anti-sense oligonucleotide alicaforsen. While results with parenteral formulations of alicaforsen in Crohn's disease have largely been negative, efficacy signals derived from studies with an enema formulation in ulcerative colitis and pouchitis are promising and have led to a Food and Drug Administration Fast-Track designation for the latter. A large phase III programme in pouchitis is underway. Phase II studies with the anti-MAdCAM-1 antibody [SHP647] delivered positive results in ulcerative colitis and anti-inflammatory signals in Crohn's disease. Furthermore, it was shown that SHP647 does not affect the number and composition of cells in cerebrospinal fluid, suggesting that the compound is not affecting immune surveillance in the central nervous system. In addition, both alicaforsen and SHP647 are promising compounds based on the clear safety profile observed so far.

Alicaforsen, an Antisense Inhibitor of Intercellular Adhesion Molecule-1, in the Treatment for Left-Sided Ulcerative Colitis and Ulcerative Proctitis.

BACKGROUND: Data on the efficacy of intercellular adhesion molecule-1 antisense oligonucleotide alicaforsen in ulcerative colitis (UC) is inconsistent. METHODS: All patients, who had received at least one dose of alicaforsen, were analyzed retrospectively. Alicaforsen's efficacy was assessed in patients treated for left-sided UC and proctitis by comparing clinical and (if applicable) endoscopic disease activity before/after treatment. RESULTS: Twelve patients were treated for left-sided UC or proctitis. Eleven patients received a 6-week course of a once-daily 240 mg alicaforsen enema formulation. In 1 patient, treatment was discontinued, because it was found to be inefficient. Disease activity measured by the partial Mayo score and 6-point symptom score was significantly reduced after treatment (6.0 vs. 2.4, p = 0.011 and 3.7 vs. 1.4, p = 0.008). Faecal calprotectin showed a trend towards reduction (484.4 vs. 179.5 µg/g, p = 0.063). Clinical improvement was achieved in 10 patients (83.3%). In 7 patients, a relapse occurred (70%). Median duration of clinical improvement was 18.0 weeks (range 1-112). Three patients showed an ongoing improvement of >9 months. No adverse events were reported. CONCLUSIONS: A 6-week course of alicaforsen seemed to be safe and efficacious in inducing clinical improvement in patients with left-sided UC and proctitis. Prolonged clinical improvement was observed in many but not all patients.

Alicaforsen in the treatment of pouchitis.

Alicaforsen is a 20-base antisense oligonucleotide inhibiting ICAM-1 production, which is an important adhesion molecule involved in leukocyte migration and trafficking to the site of inflammation. Hitherto, alicaforsen has been granted orphan drug designation and is prescribed as an unlicensed medicine in accordance with international regulation for the treatment of pouchitis and left-sided ulcerative colitis. Given the positive results evolving from one open-label trial and one case series in patients with chronic refractory pouchitis, US FDA has agreed to a rolling submission for a license application for the treatment of pouchitis, which has been recently initiated. Whether alicaforsen leads to higher endoscopic and clinical remission rates as placebo and whether the response can be maintained in the long-term in larger studies is yet unknown. An ongoing multicenter international Phase III trial will definitely address these unanswered questions.

Monitoramento do horizonte tecnológico: Medicamentos em desenvolvimento para o tratamento da polineuropatia amiloidótica familiar associada à transtirretina (PAF-TTR)Juvenil (AIJ) / Monitoring the technological horizon: Drugs in development for the treatment of juvenile transthyretin-associated familial amyloid polyneuropathy (TTR-FAP) (JIA)

DOENÇA: A Polineuropatia Amiloidótica Familiar (PAF) associada à Transtirretina (PAF-TTR) é uma doença rara, autossômica dominante e uma das formas de manifestação da amiloidose transtirretina. A amiloidose transtirretina decorre da deposição extracelular de fibrilas amiloides compostas por transtirretina (TTR) (ANDO et al., 2013), uma proteína plasmática que transporta tiroxina e retinol, além de participar de processos relacionados ao crescimento axonal e à regeneração dos nervos (VIEIRA; SARAIVA, 2014). Mutações no gene codificador da transtirretina podem resultar na produção de uma proteína mutante que tem o potencial de se dissociar de sua forma nativa tetramérica, sofrer misfolding ("mal enovelamento") e agregar-se em fibrilas amiloides que se acumulam em diversos órgãos e tecidos, causando disfunção progressiva (ANDO et al., 2013). Dentre as mutações relacionadas à PAF, a mais prevalente é a p.Val30Met, na qual o aminoácido valina é substituído por metionina na posição 30 da transtirretina (SOARES et al., 2004). TRATAMENTO FARMACOLÓGICO: Atualmente, o tratamento farmacológico da polineuropatia amiloidótica familiar é limitado (ANDO et al., 2013), sendo que apenas um medicamento, o tafamidis, possui registro de comercialização no mundo. A empresa detentora do registro do medicamento no Brasil submeteu em fevereiro de 2017 uma proposta para incorporação do tafamidis no SUS para o tratamento de pacientes com amiloidose associada à transtirretina em pacientes adultos com polineuropatia sintomática, em estágio inicial, com vistas a postergar o comprometimento neurológico periférico. A proposta está em análise pela CONITEC ("CONITEC - Tecnologias demandadas", 2017). ESTRATÉGIA DE BUSCA: Para localizar os medicamentos em fase de pesquisa clínica para a PAF-TTR, consultou-se o sítio eletrônico do ClinicalTrials.gov (CLINICAL TRIALS, 2017), utilizando-se os termos "transthyretin amyloid polyneuropathy". Consideraram-se as tecnologias a partir da fase II de pesquisa clínica, com a PAF-TTR como alvo e sem registro para essa indicação terapêutica no Brasil. As tecnologias doxiciclina + ácido tauroursodexocólico e revusiran não serão abordadas neste documento porque seus estudos clínicos alocaram pacientes com manifestações outras que não especificamente a polineuropatia (e.g. cardiomiopatia) ou a pacientes submetidos a transplante hepático. Assim, foram identificados quatro medicamentos: diflunisal, SOM0226, ALN-TTR02 e ISIS-TTRRx. Posteriormente, utilizando-se os códigos de registro no ClinicalTrials.gov referentes aos estudos clínicos com os medicamentos identificados na etapa descrita nos parágrafos anteriores e aos nomes de cada uma dessas tecnologias, realizou-se uma busca na base de dados MEDLINE via PubMed para a pesquisa de resultados publicados dos estudos clínicos. Além disso, uma busca complementar por resultados desses estudos publicados em anais de congressos científicos também foi realizada. MEDICAMENTOS EM DESENVOLVIMENTO: Estabilizadores de transtirretina: Diflunisal (Dolobid®). SOM0226 (Tolcapona, Tasmar®). Silenciadores gênicos: ALN-TTR02 (Patisiran®). ISIS-TTR Rx (oligonucleotídeo fosfotiorato específico da transtirretina; Inotersen®; ISIS 420915; ISIS-GSK1Rx). CONCLUSÕES: A perspectiva para o tratamento farmacológico da PAF-TTR melhorou significativamente na última década. Há apenas um medicamento registrado no Brasil para a doença, o tafamidis, que realiza a estabilização de transtirretina. De acordo com o monitoramento do horizonte tecnológico realizado, outras quatro tecnologias estão em fase mais avançada de desenvolvimento clínico. Dois desses medicamentos, o diflunisal e o SOM0226, têm mecanismo de ação semelhante ao tafamidis. Por outro lado, as tecnologias ALN-TTR02 e ISI TTR Rx são baseadas em silenciamento gênico e poderiam ser aplicáveis a formas mais graves da doença. Todas as quatro tecnologias não possuem registro no Brasil ou no mundo para o tratamento da PAF-TTR, no entanto, o diflunisal está registrado no FDA para outra indicação, bem como a tolcapona na Anvisa e em outras agências reguladoras internacionais. Além disso, o perfil de segurança e eficácia dessas tecnologias precisam ser confirmadas por meio de mais estudos clínicos. Desta forma, verifica-se que há no horizonte tecnológico potenciais tecnologias em desenvolvimento e que futuramente poderão ser utilizadas no tratamento da PAF-TTR.

Alicaforsen for the treatment of inflammatory bowel disease.

INTRODUCTION: Intracellular adhesion molecule-1 (ICAM-1), is a transmembrane glycoprotein of the immunoglobulin family, constitutively expressed on vascular endothelial cells and upregulated in inflamed colonic tissue. Alicaforsen, a 20 base ICAM-1 anti-sense oligonucleotide and highly selective ICAM-1 inhibitor, down-regulates ICAM-1 mRNA. Areas covered: We review mechanism of action, pharmacokinetics, pre-clinical, clinical and safety data of alicaforsen for the treatment of ulcerative colitis (UC), pouchitis and Crohn's disease (CD). Expert opinion: After 6 weeks of treatment, topical alicaforsen was significantly more effective than placebo in inducing remission in patients with moderate-severe distal UC, with treatment effects lasting up to 30 weeks. No difference was observed in head-head comparison with mesalamine topical enema, although alicaforsen appeared to have more durable treatment effect. Clinical trials of an intravenous formulation in Crohn's disease showed no significant treatment effect compared to placebo. An open-label trial in alicaforsen for pouchitis demonstrated encouraging results, now being assessed in a multi-national phase 3 trial. No major safety signals have been observed in UC patients treated with alicaforsen enemas. The potential as a novel therapy for pouchitis has led to orphan designation for this indication by the FDA and European Medicines Agency.

Considerations for the Characterization and Interpretation of Results Related to Alternative Complement Activation in Monkeys Associated with Oligonucleotide-Based Therapeutics.

This article provides an overview of the discussions held by the Immunomodulatory Subcommittee of the Oligonucleotide Safety Working Group on complement activation induced by oligonucleotides, most notably the phosphorothioate-containing oligonucleotides. Alternative complement pathway activation in monkeys is a common effect of single-stranded phosphorothioate backbone oligonucleotides in toxicology studies. This article discusses the mechanism for activation, general investigational strategy, and the impact of various chemical modifications. The goal is to provide the best practice approach to characterizing this effect, understanding the implication of the species specificity, and the interpretation of clinical relevance.

Antisense approach to inflammatory bowel disease: prospects and challenges.

Despite the great success of anti-tumour necrosis factor-based therapies, the treatment of Crohn's disease (CD) and ulcerative colitis (UC) still remains a challenge for clinicians, as these drugs are not effective in all patients, their efficacy may wane with time, and their use can increase the risk of adverse events and be associated with the development of new immune-mediated diseases. Therefore, new therapeutic targets are currently being investigated both in pre-clinical studies and in clinical trials. Among the technologies used to build new therapeutic compounds, the antisense oligonucleotide (ASO) approach is slowly gaining space in the field of inflammatory bowel diseases (IBDs), and three ASOs have been investigated in clinical trials. Systemic administration of alicaforsen targeting intercellular adhesion molecule-1, a protein involved in the recruitment of leukocytes to inflamed intestine, was not effective in CD, even though the same compound was of benefit when given as an enema to UC patients. DIMS0150, targeting nuclear factor (NF) κB-p65, a transcription factor that promotes pro-inflammatory responses, was very promising in pre-clinical studies and is currently being tested in clinical trials. Oral mongersen, targeting Smad7, an intracellular protein that inhibits transforming growth factor (TGF)-ß1 activity, was safe and well tolerated by CD patients, and the results of a phase II clinical trial showed the efficacy of the drug in inducing clinical remission in patients with active disease. In this leading article, we review the rationale and the clinical data available regarding these three agents, and we discuss the challenge of using ASOs in IBD.

Phosphorothioates, essential components of therapeutic oligonucleotides.

Phosphorothioates have found their usefulness in the general area of oligonucleotide therapeutic applications. Initially this modification was introduced into the antisense methodology because of the nuclease resistance of the phosphorothioate linkage in comparison with that of the phosphate linkage. However, as experimental data accumulated, it was detected that this chemical modification also facilitates cellular uptake and bioavailibity in vivo. Thus, today the majority of therapeutic oligonucleotides contain this modification. This review will discuss the historical development of this modification and present some of its chemical properties where they differ from those of the phosphate group. The antisense application will be discussed in the original context with cleavage of the target mRNA, but other target RNAs such as microRNAs and long noncoding RNAs will also be covered. It continues with applications where the target RNA should not be cleaved. A brief presentation of decoy oligonucleotides will be included, as well as some miscellaneous applications. Cellular uptake is a crucial step for oligonucleotides to reach their target and will be briefly reviewed. Lastly, a most surprising recent observation is the presence of phosphorothioate groups in bacterial DNA where functions still remain to be fully determined.

Lymphocyte homing antagonists in the treatment of inflammatory bowel diseases.

Lymphocyte homing antagonists represent promising therapeutic agents for the treatment of idiopathic inflammatory bowel disease (IBD). Several critical molecules involved in the recruitment of inflammatory cells in the intestine, including integrins and chemokine receptors, have been successfully targeted for the treatment of IBD. These agents have shown great promise for the induction and maintenance of remission for both Crohn disease and ulcerative colitis. This article discusses currently approved prototypic agents for the treatment of IBD (natalizumab, anti-α4 integrin; vedolizumab, anti-α4ß7 integrin), and several other agents in the same class currently under development.

In vitro and in vivo protection against enterovirus 71 by an antisense phosphorothioate oligonucleotide.

Enterovirus 71 (EV71) is a highly infectious virus that is a major cause of hand, foot, and mouth disease (HFMD), which can lead to severe neurological complications. Currently, there is no effective therapy against EV71. Five antisense oligodeoxynucleotides targeting the 5'-terminal conserved domain of the viral genome were designed using a method based on multiple predicted target mRNA structures. They were then screened for anti-EV71 activity in vitro based on their ability to inhibit an EV71-induced cytopathic effect (CPE). A novel antisense oligonucleotide (EV5) was tested both in rhabdomyosarcoma (RD) cells and in vivo using a mouse model, with a random oligonucleotide (EV5R) of EV5 as a control. EV5 was identified as having significant anti-EV71 activity in vitro and in vivo without significant cytotoxicity. Treatment of RD and Vero cells with antisense oligodeoxynucleotide EV5 significantly and specifically alleviated the cytopathic effect of EV71 in vitro. The inhibitory effect was dose dependent and specific, with a corresponding decrease in viral RNA and viral protein levels. In vivo, EV5 was specifically effective against EV71 virus in preventing death, decreasing weight reduction and reducing the viral RNA copy number and the level of viral proteins in the lungs, intestines and muscles. These results demonstrate the potential and feasibility of using antisense oligodeoxynucleotides specific for the 5'-terminal conserved domain of the viral genome as an antiviral therapy for EV71 disease.

Phosphorothioate oligonucleotides: effectiveness and toxicity.

BACKGROUND: Many experimental and clinical studies have focused on the antisense strategy. In this context phosphorothioate oligonucleotides are compounds addressed to hybridize to a targeted mRNA inducing a variety of effects including inhibition of the expression of proteins involved in different pathological processes and preventing translation. METHODS: In this review, we provide an update on clinical efficacy and toxicological profile of phosphorothioate oligonucleotides used in experimental and clinical studies, also focusing on the use of the antisense strategy in the context of Duchenne muscular dystrophy which is a key pathology to study different aspects of this therapy. Pubmed/Medline was searched using the keyword "Phosphorotioate" combined with "Antisense", "Oligonucleotide" and "Duchenne muscular dystrophy". CONCLUSIONS: Phosphorothioate oligonucleotide transient activation of the complement cascade represents the most evident toxicological response, as showed by in vivo studies. It is also known that many of these compounds induce a prolongation of activated partial thromboplastin time, a reaction which is often highly transient and proportional to the oligonucleotide plasma concentrations, making that effect clinically insignificant for the current treatment regimens. In summary, current evidence shows limited untoward effects and reversibility of the damage induced, at least for some of those compounds, with promising effectiveness for treatment of various pathologies.