MDD Washington Editor

A number of themes emerged during Tuesday’s day-long FDA nanotechnology conference, one of which might seem a case of splitting fine hairs. However, this fine hair may have regulatory implications that could affect the status of thousands of products that come to market.

As matters currently stand, the NNI definition of a nanoparticle is a particle that spans 100 nm (nanometers) in length/diameter or less. As a point of perspective, a particle less than 60 nm can slip past most cell membranes and at four nm, the blood-brain barrier is no longer a barrier.

The question of whether size should be the sole, or even primary, criterion was raised in several quarters. Neil Desai, PhD, vice president of research and development at Abraxis Bioscience (Schaumberg, Illinois), argued that a number of journal articles he has seen discussed particles larger than 100 nm in a “nano” context. He added that given the action of many drug-delivery vehicles such as liposomes, a size boundary of 220 nm was probably more relevant.

John Balbus, the senior scientist at the Washington office of Environmental Defense (New York), acknowledged that the definition “is proving to be pretty thorny,” a sentiment drawing no opposition.

The size issue is one that may carry substantial regulatory implications, but the agency is still in an information-gathering mode and not inclined to try to answer the question at present. A lot of comment during the meeting on the effects of drugs delivered via nanoparticles focused on differences in effect based on drug molecule size, raising the prospect that an old drug delivered a new way might require traditional new drug testing.

In the same vein, devices with nanotech components based on a predicate device may have to run the PMA gauntlet if the Center for Devices and Radiological Health decides that the new technology renders a device insufficiently equivalent to qualify for a 510(k) filing.