Study explores whether reducing smoke toxicant exposure affects biomarkers of biological effect

British American Tobacco has published the protocol for a clinical study designed to determine whether using reduced-toxicant prototype cigarettes that reduce smokers' exposure to smoke toxicants impacts biological effect (ISRCTN81286286).

The study protocol refers to the 'recipe' used to conduct a study, describes what will be done during the study, how this will be done and why it is being done.

This study follows a previous study by researchers at British American Tobacco that showed that it is possible to reduce smokers' exposure to certain smoke toxicants by switching them to novel prototype cigarettes with lower amounts of some toxicants in the smoke (doi:10.1016/j.yrtph.2013.02.007). This was a short-term study, lasting six weeks. Now a second clinical study will assess whether this reduced exposure is maintained over the longer term, and also whether longer term exposure reduction results in detectable changes in biological effect.

The prototype cigarettes used in both studies contained technologies designed to reduce key toxicants in smoke. A resin that removes aldehydes and a nano-porous carbon that traps volatile smoke compounds were added to the filter. An enzyme-treatment was used on the tobacco to remove proteins and polyphenols that become toxicants when burned, and inert calcium carbonate and glycerol were added to dilute the smoke.

BAT combined these technologies into three different prototype cigarettes and showed in a clinical study that there was a reduction in exposure to certain toxicants in smokers who switched to the prototype cigarettes for six weeks.

However, that study was not long enough to explore the potential for a reduction in risk of smoking-related diseases or adverse biological effects. Now a longer-term (six months) study will determine whether use of prototype cigarettes leads to both continued reductions in exposure to toxicants and beneficial changes in the body, as shown by assessment of selected biomarkers. The protocol for this new study has been approved by an independent ethics committee and is published in BioMed Central Public Health.

The six-month single-centre, single-blinded, controlled switching study with periods of clinical confinement is being conducted in Germany. A total of 260 healthy adult subjects were recruited into the study; 140 smokers, 60 former smokers and 60 never-smokers (ISRCTN81286286). The demographically matched non-smokers serve as a comparison group because some toxicant exposure stems from dietary and environmental sources. The non-smokers also provide reference levels for biomarkers of biological effect.

Smokers are randomly assigned to a control or test group. Both groups smoke a control product for two weeks, at which point baseline measurements of biomarker levels are made. Smokers in the control group then continue to smoke the control product for a further 24 weeks, while smokers in the test group switch to the prototype cigarette. Urine, saliva and blood samples are taken from all smokers at 4, 9, 13 and 24 weeks after the switch. Biomarkers of exposure and biological effect are then measured.

Changes in biomarker levels are analysed at baseline, midpoint and end of the study. Levels within individuals are compared before and after switching, while those between individuals are evaluated by comparing smokers who switched with those who didn't.

Data from this study are expected to improve the scientific understanding of tobacco products. Changes in biomarkers of biological effect may add to the body of evidence of the potential of toxicant reducing technologies in reducing disease risk.

"There are already tobacco and nicotine products available, such as snus and e-cigarettes, that are known to pose substantially lower risk than cigarettes. And we don't know whether it will be possible to scientifically prove that reduced toxicant cigarettes reduce health risks,' said Dr David O'Reilly, Group Scientific Director at British American Tobacco. 'But,' he said, 'we believe reducing smokers' exposure to cigarette smoke toxicants continues to be an important research objective, given the numbers of people who smoke and the numbers who are likely to continue to smoke for the foreseeable future.'

Source: R&D at British American Tobacco