The main goal of this exploratory study is to evaluate the pharmacokinetic profile of nicotine for the candidate modified risk tobacco product THS 2.1 and for conventional cigarettes (CC).

This 2-period 2-sequence cross-over clinical study intends to explore the profile of nicotine uptake (rate and extent of nicotine absorbed and associated variability) in healthy smokers switching from (CC) to THS 2.1 (single or ad libitum use) compared to smokers continuing to use CC, as a comparator. This study will serve to optimize blood sampling schedules and sample size estimation for further studies. This study will also provide preliminary information on the relationship between nicotine absorption and urge to smoke/withdrawal symptoms when using THS 2.1 as compared to CC, as well as the safety profile, which is related to the use of THS 2.1.

After screening, enrolled subjects will be admitted to the clinic for 8 days. This study duration includes 2 consecutive periods. Each period consists of 1 day for single use of the product preceded by a 24-hour nicotine deprivation, and 1 day for ad libitum product use. After leaving the clinic, the subjects will be followed up for safety over a period of 7 days.

This clinical study will be conducted in compliance with International Conference on Harmonisation of technical requirements for registration of pharmaceuticals for human use (ICH Good Clinical Practice), the Declaration of Helsinki as amended in 2008, and the applicable regulatory requirements.

Inclusion Criteria:

• Subject has signed an informed consent form before commencement of study procedures
• Healthy Caucasian aged between 23 to 65 years
• Subject is current smoker for at least 3 years (based on self-reporting and biochemically verified), who, for the last 4 weeks, had smoked at least 10 commercially available non-mentholated CC per day, and is not planning to make a quit attempt within the next 3 months

Exclusion Criteria:

• As per Investigator judgment, the subject should not participate in the study for any reason (e.g. medical, psychiatric and/or social reason)
• The subject has a medical condition requiring smoking cessation, or has a clinically relevant disease / condition which could interfere with the study participation and/or study results
• The subject has participated in a clinical study within 3 months prior to the Screening Visit
• Pregnant or lactating woman, and for woman of childbearing potential, absence / refusal to use an acceptable method of effective contraception