We have conducted a study that addresses the first part of the IOM's definition of a PREP by analyzing biomarkers of exposure (BoE) in smokers switched to prototype cigarettes which produced lower levels of some smoke toxicants compared to conventional cigarettes.

The 6-week study involved short periods of clinical confinement. One hundred smokers of 6mg ISO tar cigarettes were recruited. After 2 weeks smoking a commercial 6mg ISO tar yield product, 50 were switched to a 6mg ISO tar Reduced Toxicant Prototype (RTP) cigarette containing diluent sheet in the blend, and a high activity charcoal filter. In addition, 150 smokers of 1mg ISO tar commercial cigarettes were also recruited. 50 of these subjects were switched to a 1mg ISO tar yield RTP containing the diluent sheet, and a three stage filter containing high activity carbon and an amine functionalized resin material; 50 to an RTP containing tobacco treated to reduce polyphenols and proteins, and the same three stage filter.

BoE, mouth level exposure to tar and nicotine were measured, and the sensory response to the product scored. The study found that switching to RTPs at both tar yields reduced levels of BoE for several smoke toxicants compared to conventional cigarettes. The reductions in BoE correlated well with machine measured reductions in smoke toxicant levels.

The next stage of RTP prototype testing is in planning and will include biomarkers of biological effect (BoBE) and an extended switching period of 6 months, to allow time for changes in these biomarkers to occur. The primary objective will be to determine whether longer term use of an RTP results in continued exposure reduction and a reduction in BoBE.