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WHY NANOTECHNOLOGY AND NANOMEDICINE?

The application of nanotechnology to treat diseases is known as nanomedicine. The US Food and Drug Administration has approved some nanoparticulate formulations and numerous others are under development in various clinical stages. Table 6.1 summarizes some of these nanoparticle formulations [3—6]. Nanoparticulate systems could play a vital role in drug delivery, imaging, and even in surgery as they have a size range similar to that of biological molecules such as proteins, receptors, DNA, and RNA [7]. Nanoparticulate systems are relatively small in size compared to cells but are bigger than most “small molecule”—type drugs, which could improve their retention time in circulation without the risk of clogging the blood vessels, which in turn can improve the bioavailability and pharmacokinetic profile of various drugs. Nanoparticles can utilize a natural process called endocytosis to penetrate cells, which presents a particular advantage in situations where normal entry into cells would be challenging for a given molecule [8]. This feature is also helpful in targeting specific organelles inside the cells such as nuclei in case of gene knockdown using small interfering RNAs (siRNAs) [9—12]. Another interesting feature of nanoparticulate systems is their high surface area-to-volume ratio, which provides a large substrate for attachment of specific moieties for active targeting [13]. Nanoparticles can be surface modified with specific antibodies or peptides to achieve tissue targeting, which reduces the likelihood of nonspecific off-target toxicity [14,15]. The surface properties ofnanotherapeutics can be modified according to therapeutic and diagnostic needs, including imparting stealth properties to evade elimination by the reticuloendothelial system, which improves the circulation time and increases drug concentration at the site of action [5,16].

Nanoparticulate technology has opened up potential new avenues in the early detection and treatment of various cancers, biodetection of pathogens, and in the preparation of fluorescent biological labels as they encompass both imaging and therapeutic capabilities. Nanoparticulate technology is also helpful in addressing solubility and stability issues of poorly soluble drugs and in altering their pharmacokinetic profiles to achieve prolonged plasma half-life. Since 1980s, the healthcare community has encountered clinical challenges where resistance has developed against antibiotics and select other traditional therapeutics. It is possible that these issues can be addressed by using nanoparticulate drug delivery systems [4,17]. However, despite the projected therapeutic benefits, there are limitations and challenges with nanotechnology that need to be addressed to improve the odds for success, including the development of better characterization techniques, achieving batch-to-batch consistency, reducing developmental costs and the clinical translation of theoretical design to clinical/therapeutic efficacy [18—20]. Several experimental nanoparticulate systems are known to cause nonspecific inflammatory responses and to possess immunomodulatory properties [21,22]. Other challenges include the detachment of the active targeting moieties before reaching the site of action

Table 6.1 Examples of FDA-approved nanoparticulate formulations

Drug product

Active ingredient

Manufacturer

Indications

FDA approval date

Abraxane

Albumin-bound paclitaxel

Abraxis Bioscience, Astra Zeneca, Celgene

Metastatic

adenocarcinoma

2013

Non—small cell lung cancer

2012

Breast cancer

2005

Ferumoxytol

Marqibo

Iron oxide nanoparticles Vincristine

Talon Therapeutics

Iron deficiency

2009

Philadelphia chromosomenegative lymphoblastic leukemia

2012

Oncaspar

PEGasparaginase injectable solution

Enzon

Acute lymphoblastic leukemia

2006

Rapamune

Nanocrystals

2002

Myocet

Liposome-encapsulated

doxorubicin

Elan/Sopherion

therapeutics

Breast cancer

2000, approved in Europe and Canada

DepoCyt

Liposomal cytarabine

Skye Pharma, Enzon

Lymphomatous meningitis

1999

Ontak

Diphtheria toxin

Seragen

Cutaneous T-cell

1999

AmBisome

Liposomal amphotericin B

Astellas

Fungal infections

1997

Feridex

Iron oxide nanoparticles, injectable solution

AMAG Pharma

Contrast agent for MRI

1996

DaunoXome

Daunorubicin citrate liposomes

Gilead Sciences

HIV-related Kaposi

sarcoma

1996

Doxil

PEGylated liposome of doxorubicin hydrochloride

Ortho Biotech

Ovarian cancer

1995

ThermoDox

Heat-activated liposomal doxorubicin

Celsion

Breast cancer, primary liver cancer

2013

Resovist

Iron oxide nanoparticles coated with carboxydextran

Bayer Schering Pharma AG

Liver/spleen lesion imaging

2001, approved in Europe

Endorem

Iron oxide nanoparticles coated with dextran

Guerbet

Liver/spleen lesion imaging

2001, approved in Europe

Genexal-PM

Paclitaxel-loaded polymeric micelle

Samyang

Breast cancer/small cell lung cancer

Marketed in Europe, Korea

FDA, US Food and Drug Administration; HIV, human immunodeficiency virus; MRI, magnetic resonance imaging; PEG, polyethylene glycol.

(pretarget release), which could lead to exaggerated toxicity, and concerns about safety and manufacturability. Moreover, it is acknowledged that nanoparticulate systems are not mainstream in crossing the barrier of regulatory approval [20].

 
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