First report of in vitro selection of RNA aptamers targeted to recombinant Loxosceles laeta spider toxins

BACKGROUND: Loxoscelism is the envenomation caused by the bite of Loxosceles spp. spiders. It entails severe necrotizing skin lesions, sometimes accompanied by systemic reactions and even death. There are no diagnostic means and treatment is mostly palliative. The main toxin, found in several isoforms in the venom, is sphingomyelinase D (SMD), a phospholipase that has been used to generate antibodies intended for medical applications. Nucleic acid aptamers are a promising alternative to antibodies. Aptamers may be isolated from a combinatorial mixture of oligonucleotides by iterative selection of those that bind to the target. In this work, two Loxosceles laeta SMD isoforms, Ll1 and Ll2, were produced in bacteria and used as targets with the aim of identifying RNA aptamers that inhibit sphingomyelinase activity. RESULTS: Six RNA aptamers capable of eliciting partial but statistically significant inhibitions of the sphingomyelinase activity of recombinant SMD-Ll1 and SMD-Ll2 were obtained: four aptamers exert ~17% inhibition of SMD-Ll1, while two aptamers result in ~25% inhibition of SMD-Ll2 and ~18% cross inhibition of SMD-Ll1. CONCLUSIONS: This work is the first attempt to obtain aptamers with therapeutic and diagnostic potential for loxoscelism and provides an initial platform to undertake the development of novel anti Loxoscelesvenom agents.

Tratamento da DMRI exsudativa: revisão das drogas antiangiogênicas / Wet-amd treatment: a review in the anti-vegf drugs

Degeneração Macular Relacionada à Idade (DMRI) exsudativa é a principal causa de perda visual severa em indivíduos acima de 50 anos nos países desenvolvidos. O fator de crescimento endotelial (VEGF) é considerado um dos mais importantes reguladores da angiogênese e da permeabilidade vascular . Drogas com atividade antiVEGF tem se mostrado eficaz em preservar ou melhorar a acuidade visual (AV) ao inibir a permeabilidade vascular e o crescimento neovascular nos pacientes tratados. Este artigo de revisão descreve o atual uso terapêutico das medicações antiVEGF para DMRI exsudativa e fornece uma visão geral do futuro da terapia antiangiogênica.

Neovascular age-related macular degeneration is the leading cause of severe, irreversible vision loss in individuals over 50 years in developed countries. Vascular endothelial growth factor (VEGF) has been shown to play a role in the regulation of choroidal neovascularization and vascular permeability. Anti-VEGF drugs have been shown to preserve or improve visual acuity by inhibiting vascular permeability and arresting the growth of neovascularization in the vast majority of treated patients. This review describes the current literature on the use of this therapeutic approach in the management of neovascular AMD and gives an overview of the future directions.

Antibodies are challenged.

Studies on antibody were documented as early as in 1890. They are proteins found in blood or other body fluid of vertebrates, and are used by the immune system to identify and neutralize antigens (like foreign objects, pathogens like bacteria and virus etc). Antibodies are dominating the biomedical research field especially detection, imaging and inhibition of biological target molecules, and therapeutics so far. However, recently aptamer has been seen to compete with antibodies in all the above areas. Aptamers are single stranded oligonucleotides or peptides that fold into well defined three dimensional shapes, allowing them to bind their targets with high affinity and specificity. Aptamer technology is relatively new and discovered only in 1990. Because of synthetic origin and similar function as antibodies, they are often termed as chemical antibody. Within 25 years of discovery, the first generation of aptamer drug "Macugen" is already marketed and available for public use. The Global market for aptamer was $236 million in 2010 and is expected to be valued at nearly $1.8 billion by 2014, with a growing compound annual growth rate of 67.5%. Various drugs being on the pipeline for clinical trials this emerging field of medical biotechnology is raising significant interest. This article gives an overview how aptamers are similar yet distinctly different from antibodies in terms of synthesis, handling, and applicability.

Pegaptanib sodium for ocular vascular disease.

Pegaptanib sodium (Macugen) is a selective RNA aptamer that inhibits vascular endothelial growth factor (VEGF) 165 , the VEGF isoform primarily responsible for pathologic ocular neovascularization and vascular permeability, while sparing the physiological isoform VEGF 121 . After more than 10 years in development and preclinical study, pegaptanib was shown in clinical trials to be effective in treating choroidal neovascularization associated with age-related macular degeneration. Its excellent ocular and systemic safety profile has also been confirmed in patients receiving up to three years of therapy. Early, well-controlled studies further suggest that pegaptanib may provide therapeutic benefit for patients with diabetic macular edema, proliferative diabetic retinopathy and retinal vein occlusion. Notably, pegaptanib was the first available aptamer approved for therapeutic use in humans and the first VEGF inhibitor available for the treatment of ocular vascular diseases.

A comparative debate on the various anti-vascular endothelial growth factor drugs: pegaptanib sodium (Macugen), ranibizumab (Lucentis) and bevacizumab (Avastin).

Wet age-related macular degeneration and diabetic retinopathy are pathological consequences of vascular endothelial growth factor (VEGF) release as a reaction to deficiency of oxygen and nutrients in the macular cells. Conventional treatment modalities have been constrained by limited success. Convincing evidence exists that targeting VEGF signaling is a significant approach for the therapy of these ocular angiogenesis-dependent disorders. We have come a long way since the approval of the first angiogenesis inhibitors in medicine. The clinical use of these drugs has provided enormous tempo to clinical and pharmacological research. It has also significantly altered patient outcome and expectations. In the following brief, we will discuss the development and emergence of these drugs as well as the anticipated future course based on evidence.

Tratamento da forma neovascular de degeneração macular relacionada à idade com drogas antiangiogênicas / Treatment of neovascular age-related macular degeneration with antiangiogenic drugs

Degeneração macular relacionada à idade (DRMI) é a principal causa de cegueira no mundo ocidental. Várias formas clínicas foram reconhecidas, e membrana neovascular coroideana (MNSR) representa manifestação importante passível de tratamento. O tratamento de MNSR tem sido um foco importante de pesquisa nas últimas décadas e a primeira terapia estabelecida baseada em evidência foi a fotocoagulação a laser, que reduziu o risco de perda visual em lesões extrafoveais. No fim da década de 90 a terapia fotodinâmica foi estabelecida como método eficiente de tratamento de MNSR predominantemente clássicas e ocultas. Terapias adicionais como a translocação macular, cirurgia submacular, e protrombose mediada por indocianina verde estão atualmente em investigação em ensaios clínicos em larga escala. A biologia molecular permitiu recentemente uma melhor compreensão da patogênese da DMRI e o fator de crescimento vascular endotelial foi reconhecido como um mediador-chave na angiogênese da formação de MNSR. Portanto, a abordagem farmacológica surge como opção terapêutica no tratamento da MNSR. O primeiro agente terapêutico aprovado pelo FDA é o aptâmero pegaptanib sódio (Macugen®), que inativa a isoforma fundamental para a angiogênese intra-ocular: VEGF165. Outros inativadores de VEGF como ranibizumab RhuFab V2 (Lucentis®) e bevacizumab (Avastin®) estão em avaliação em estudos clínicos. Resultados impressionantes de bevacizumab intravítreo foram liberados recentemente. Adicionalmente, o derivado de esteróides acetato de anecortave, assim como o corticosteróide acetato de triancinolona têm sido propostos como métodos no tratamento de DMRI-neovascular. Este artigo apresenta os princípios e resultados iniciais na terapia antiangiogênica farmacológica da MNSR na DMRI.

Age-related macular degeneration (ARMD) remains a leading cause of blindness in the western world. Several clinical forms of the disease are recognized, whereas choroidal neovascularization (CNV) represents an important manifestation suitable for treatment. The treatment of CNV has been a major focus of research in the past decades, and the first evidence-based established therapy was laser photocoagulation, which reduces the risk of visual loss in extrafoveal lesions. In the late 90's photodynamic therapy has been established as an efficient method for the treatment of predominantly classic and occult CNV. Additional therapies such as macular translocation, submacular surgery, and indocyanine-mediated prothrombosis are currently under investigation in large-scale clinical trials. Molecular biology has recently provided a better comprehension of the pathogenesis of ARMD, and vascular endothelial growth factor (VEGF) was recognized as key mediator in the angiogenesis of CNV-formation. Therefore, the pharmacological approach rose as a key research area to treat CNV. The first FDA-approved agent for CNV-therapy is aptamer pegaptanib sodium (Macugen®), which inactivates the key angiogenic isoform VEGF165. Additional VEGF-blockers such as ranibizumab RhuFab V2 (Lucentis®) and bevacizumab (Avastin®) are under evaluation in major clinical studies. Impressive results of intravitreal bevacizumab were released recently. Moreover, the steroid-derived anecortave acetate as well as the corticosteroid triamcinolone acetate have been proposed as methods for treatment of wet-ARMD. This paper presents the rationale and principles of the pharmacologic antiangiogenic therapy for CNV in ARMD.