Setting the framework
The US Food and Drug Administration has not established its own formal definition of nanotechnology, although the agency participated in a definition of nanotechnology set by the National Nanotechnology Initiative (NNI). The NNI is a federal research and development (R&D) program established to coordinate the multiagency efforts in nanoscale science, engineering, and technology. FDA and 22 other federal agencies participate. The NNI defines nanotechnology to involve all of the following criteria:
Nanodrugs in action
Although the regulatory framework for nanotechnology in pharmaceutical applications and its exact definition are under consideration, in the context of technology platforms, a broader term of nanodrugs may be used. These nanomedicines are drugs that use platforms based on nanotechnology and related approaches. The technology evolution of nanodrugs can be seen when evaluating commercial products and clinical and preclinical candidates.
"In the current nanotechnology drug market, the strategy is largely on product-life extension by formulating existing drugs to enhance their half-lives, improve their oral bioavailability, or efficacy," says Lee Jia, senior project officer of the Developmental Therapeutics Program for the National Cancer Institute at the National Institutes of Health, who spoke at the 2008 American Association of Pharmaceutical Scientists annual meeting. Advanced nanotechnology systems such as dendrimers and carbon nanotubes are not yet represented in the list of approved nanodrugs. Unlike the majority of clinical and preclinical nanodrugs, only 25% of currently marketed nanodrugs are directed toward cancer treatment (3).
When examining the nanodrugs in clinical development, more advanced systems are used, and there is a greater emphasis on anticancer therapeutics (2). Although liposomal and polymeric-based platforms are still represented, more complex systems such as nanocrystals, nanoemulsions, drugs formulated with gold nanoparticles, and dendrimers are used. Gold nanoparticles, for example, use the leaky vasculatures of tumors to target delivery of pharmaceutically active compounds to the tumor. Dendrimers, which have high loading power and specific targeting units, can deliver more active compounds to specific organs and tissues. There are at least 27 nanodrugs in clinical trials, and approximately 60% of them are for cancer treatment (3).
The value-added focus on nanotechnology in drug development is pushed further in preclinical drug candidates. There are at least 23 nanodrugs in preclinical development, and 78% of them are anticancer agents. New formulations involve the use of dendrimers and metallic, ceramic, and virus-based nanoparticles (3).