RESUMO
Preclinical characterization of novel nanotechnology-based formulations is often challenged by physicochemical characteristics, sterility/sterilization issues, safety and efficacy. Such challenges are not unique to nanomedicine, as they are common in the development of small and macromolecular drugs. However, due to the lack of a general consensus on critical characterization parameters, a shortage of harmonized protocols to support testing, and the vast variety of engineered nanomaterials, the translation of nanomedicines into clinic is particularly complex. Understanding the immune compatibility of nanoformulations has been identified as one of the important factors in (pre)clinical development and requires reliable in vitro and in vivo immunotoxicity tests. The generally low sensitivity of standard in vivo toxicity tests to immunotoxicities, inter-species variability in the structure and function of the immune system, high costs and relatively low throughput of in vivo tests, and ethical concerns about animal use underscore the need for trustworthy in vitro assays. Here, we consider the correlation (or lack thereof) between in vitro and in vivo immunotoxicity tests as a mean to identify useful in vitro assays. We review literature examples and case studies from the experience of the NCI Nanotechnology Characterization Lab, and highlight assays where predictability has been demonstrated for a variety of nanomaterials and assays with high potential for predictability in vivo.
Assuntos
Testes Imunológicos de Citotoxicidade/métodos , Nanoestruturas/toxicidade , Animais , Ativação do Complemento/efeitos dos fármacos , Citocinas/imunologia , Avaliação Pré-Clínica de Medicamentos/métodos , Humanos , Nanomedicina/métodos , Fagocitose/efeitos dos fármacos , Trombose/induzido quimicamenteRESUMO
There are many important considerations during preclinical development of cancer nanomedicines, including: 1) unique aspects of animal study design; 2) the difficulties in evaluating biological potency, especially for complex formulations; 3) the importance of analytical methods that can determine platform stability in vivo, and differentiate bound and free active pharmaceutical ingredient (API) in biological matrices; and 4) the appropriateness of current dose scaling techniques for estimation of clinical first-in-man dose from preclinical data. Biologics share many commonalities with nanotechnology products with regard to complexity and biological attributes, and can, in some cases, provide context for dealing with these preclinical issues. In other instances, such as the case of in vivo stability analysis, new approaches are required. This paper will discuss the significance of these preclinical issues, and present examples of current methods and best practices for addressing them. Where possible, these recommendations are justified using the existing regulatory guidance literature.
Assuntos
Antineoplásicos/administração & dosagem , Antineoplásicos/farmacocinética , Avaliação Pré-Clínica de Medicamentos/métodos , Nanomedicina , Nanoestruturas/administração & dosagem , Neoplasias/tratamento farmacológico , Animais , Humanos , Modelos Biológicos , Coelhos , Ratos , Ratos Sprague-DawleyRESUMO
Nanoparticles have unique physicochemical properties which make them promising platforms for drug delivery. However, immune cells in the bloodstream (such as monocytes, platelets, leukocytes, and dendritic cells) and in tissues (such as resident phagocytes) have a propensity to engulf and eliminate certain nanoparticles. A nanoparticle's interaction with plasma proteins (opsonins) and blood components (via hemolysis, thrombogenicity and complement activation) may influence uptake and clearance and hence potentially affect distribution and delivery to the intended target sites. Nanoparticle uptake by the immune cells is influenced by many factors. Different nanoparticles have been shown to act on different pathways, while various characteristics/properties also affect which pathway is employed for particle internalization. Nanoparticle protein binding occurs almost instantaneously once the particle enters biological medium, and the physical properties of such a particle-protein complex are often different than those of the formulated particle. These new properties can contribute to different biological responses and change nanoparticle biodistribution. Therefore, in the situation when specific delivery to immune cells is not desired, the ideal nanoparticle platform is the one whose integrity is not disturbed in the complex biological environment, which provides extended circulation in the blood to maximize delivery to the target site, is not toxic to blood cellular components, and is "invisible" to the immune cells which can remove it from circulation. This review discusses the most recent data on nanoparticle interactions with blood components and how particle size and surface charge define their hematocompatibility. This includes properties which determine particle interaction with plasma proteins and uptake by macrophages. We will also provide an overview of in vitro methods useful in identifying interactions with components of the immune system and the potential effects of such interaction on particle distribution to tissues.