Preclinical assessments and clinical studies have shown significant reductions in toxicants in tobacco heating product (THP) aerosols compared to smoke from conventional cigarettes. Further studies to assess if these toxicant reductions translate to reductions in smoking-related health risks are being carried out. As these designs tend to be ambulatory in nature with the subjects visiting the clinic at specific timepoints, the potential for non-compliance, where the subject smokes conventional cigarettes and not the assigned THP, is high.

In our current study examining health effect indicators when a smoker switches to using a THP in the U.K. (ISRCTN81075760) we employed a biomarker of compliance, the haemoglobin adduct of acrylonitrile cyano-ethyl valine (CEVal). This paper presents data from the cessation arm, where subjects have ceased all tobacco and nicotine use except for being allowed nicotine replacement therapy (NRT), and the never smoker arm over a period of 90 days.

This study was approved by a local research ethics committee and run in accordance with ICH-GCP. Subjects were of either gender (aged 23-55 years) and comprised of regular smokers who intended to quit and were provided with assistance with quitting (NRT/varenicline/counselling) or were participants who have never smoked. At the 90-day stage of this study, subjects had attended a total of four non-residential clinic visits plus a screening visit. Blood samples were taken at baseline, and days 30, 60 and 90 for the cessation arm, whereas never smokers’ samples were taken at baseline and day 90. The haemoglobin adduct CEVal was measured in all blood samples and showed reductions in levels in the cessation arm between baseline and day 90. Whereas there was no change in CEVal levels in the never smokers.

This data shows that CEVal has the potential to be a long-term biomarker of compliance in potentially reduced-risk product (PRRP) switching studies.