Jill Wechsler
|
Nanotechnology is a highly promising approach to improving the design and manufacture of more targeted and less toxic therapies.
Nanomaterials—any material that is less than 100-millionths of a millimeter in size—are being used in many consumer and industry
products, including a growing number of drugs and diagnostics. Such tiny particles can increase product stability and enhance
absorption and elimination. Most important, the ability of nanoparticles to pass more easily through cellular membranes and
tissues is raising high hopes for developing cancer therapies capable of delivering drugs to targeted tumor cells, with less
damage to healthy tissues and fewer toxic side effects.
As part of its Critical Path Initiative, launched in 2004, the US Food and Drug Administration is encouraging public-private
collaborations to more fully explore the physical and chemical characteristics of nanoparticles. The goal is to develop new
test methods, characterization protocols, and standards that will help manufacturers move nanoproducts from preclinical testing
to commercialization.
GREAT POTENTIAL
The federal government spends more than $1 billion a year on its National Nanotechnology Initiative, established in 2001.
Some of this funding supports the National Institutes of Health Roadmap Initiative, launched in September 2003, to discover
how nanotechnology can enhance our basic understanding of biological concepts and cellular processes. National Cancer Institute
officials are particularly enthusiastic about the great potential of nanotechnology to detect cancer at very early stages.
Such methods could enable clinical trials to assess efficacy in anticancer therapies much earlier. And "smart" nanotherapeutics
could time the release of a drug or deliver multiple drugs sequentially, as well as provide sustained therapy for chronic
cancers.
Biomedical nanoscience strategies may facilitate gene therapy development, which has been stymied by difficulties in finding
suitable transport agents to carry nucleic acid to the diseased target cell. New nanoscale structures designed to bind and
neutralize anthrax toxins may protect people from infectious diseases. Researchers at Montana State University are using disarmed
viruses and protein "cage" technology to deliver therapeutic and imaging agents to specific tissues, an approach that may
have multiple applications for carrying antibodies, peptides, and other therapies to cells.
FDA has approved nanoscale liposomes and microemulsions, as well as magnetic resonance imaging agents and targeting agents.
A treatment for metastatic breast cancer, Abraxane, (Abraxis BioScience,
http://www.abraxisbio.com/) uses human albumin to create nanoparticles of Taxol (paclitaxel); the resulting injectable suspension does not require any
solvent and thus reduces serious side effects and permits a higher doses for patients. Similarly, Cell Therapeutics of Seattle,
WA (
http://www.celltherapeutics.com/) is testing a nanotherapy for lung cancer (Xyotax) that binds Taxol to a polyglutamate polymer, to more efficiently deliver
the drug to tumor cells.
REGULATORY CONCERNS
These developments are expected to yield more combination products with multiple components, including a delivery system,
therapy, and imaging agent. Such complex therapies will challenge FDA's Office of Combination Products in determining the
primary mode of action, of which the FDA center has primary regulatory oversight. FDA's Office of Science and Health Coordination
oversees nanotechnology activities throughout the agency, including its participation on government-wide nanotechnology committees.
Call for papers
|
As more nanotherapies and diagnostics move from laboratories to commercial development, FDA officials recognize the need for
more guidance for manufacturers and added scrutiny of related safety issues. Such concerns have emerged with the appearance
of multiple sunscreen products featuring nanoformulations that render them transparent and more easily absorbed by the skin.
A coalition of environmental and health organizations, led by Center for Technology Assessment, considers these products to
be dangerous. The group filed a petition with FDA in May 2006, calling for the agency to pull all over-the-counter nanosunscreens
off the market until manufacturers can prove they are safe. The petition seeks new regulations for drugs containing nanoparticles,
along with changes in FDA's 1999 sunscreen monograph to require additional analysis of nanoparticles in these products and
labeling all nanoingredients.
