Changes in Biomarkers of Exposure on Switching From a Conventional Cigarette to the glo Tobacco Heating Product: A Randomized, Controlled Ambulatory Study

Nicotine Tob Res. 2021 Feb 16;23(3):584-591. doi: 10.1093/ntr/ntaa135.


Introduction: Tobacco heating products (THPs) generate lower machine yields of toxicants compared to those found in conventional cigarette smoke. During use, these products are likely to expose users to lower levels of particulate matter and harmful and potentially harmful compounds compared with smoking cigarettes.

Aims and methods: This randomized, controlled study is investigating whether biomarkers of exposure (BoE) to smoke toxicants are reduced when smokers switch from smoking cigarettes to using the glo THP in a naturalistic, ambulatory setting. Control groups include smokers who are abstaining from cigarette smoking and never-smokers. At a baseline study visit, 24-hour urine samples and spot blood samples were taken for BoE analysis, and exhaled carbon monoxide was also measured. N-(2-cyanoethyl) valine (CEVal) was used as a marker of compliance in subjects asked to refrain from combustible cigarette smoking. Subjects are being followed up at periodic intervals for 360 days; this article presents data following a planned interim analysis at day 90.

Results: In continuing smokers, BoE remained stable between baseline (day 1) and day 90. In both per-protocol and CEVal-compliant analysis populations, reductions in BoE were observed in subjects switching to using glo or undergoing smoking cessation. These reductions were statistically significant for a number of BoE when switching to glo was compared with continued smoking. Furthermore, in both populations, reductions observed in subjects switching to using glo were comparable to those seen with smoking cessation and were also to levels similar to those seen in never-smokers.

Conclusion: glo is a reduced-exposure tobacco product.

Implications: This clinical study builds on a previous 5-day confinement study and demonstrates that when smokers switched from smoking combustible cigarettes to using the glo THP in a naturalistic, ambulatory setting, their exposure to tobacco smoke toxicants was significantly decreased. For most BoE examined, this was to the same extent as that seen when a control group of smokers ceased cigarette smoking, or even to levels seen in never-smoker controls. This indicates that glo is a reduced-exposure product with the potential to be a reduced-risk tobacco product, when used by smokers whose cigarette consumption is displaced completely.

Clinical trial registration: ISRCTN81075760.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Biomarkers / analysis*
  • Cigarette Smoking / blood*
  • Cigarette Smoking / epidemiology
  • Cigarette Smoking / psychology
  • Cigarette Smoking / urine*
  • Exhalation
  • Female
  • Hazardous Substances / adverse effects
  • Heating / adverse effects*
  • Humans
  • Male
  • Middle Aged
  • Smokers / psychology*
  • Tobacco Products / adverse effects
  • Tobacco Products / analysis*
  • United Kingdom / epidemiology
  • Young Adult


  • Biomarkers
  • Hazardous Substances

Associated data

  • ISRCTN/ISRCTN81075760