Background: In addition to smoking cessation (SC) programs, tobacco harm reduction strategies include switching from cigarettes to reduced-risk alternatives in smokers who wish to continue to smoke. The Carbon Heated Tobacco Product (CHTP) 1.2, similar in appearance to a cigarette, replicates the smoking ritual while generating a nicotine-containing aerosol by heating tobacco instead of burning it and is currently being assessed for its harm reduction potential compared with cigarettes. Methods: We conducted a randomized, controlled, open-label, two-arm parallel group study in 120 healthy adult European smokers who either switched from cigarette smoking to CHTP 1.2 (CHTP 1.2 group; N=80) or continued to smoke cigarettes (cigarette group; N=40) for five days in a confined setting followed by 85 days in an ambulatory setting. The study aimed to demonstrate reduction in the exposure to 14 harmful and potentially harmful constituents and to evaluate the effects on clinical risk endpoints (CRE) indicative of mechanistic pathways underlying the development of smokingrelated diseases and the safety profile between the two groups. Results: Significant reductions in all biomarkers of exposure (BoExp) were observed in the CHTP 1.2 group on Day 5 (40.2% to 94.9%) and sustained throughout the 85-day ambulatory period (36.3% to 92.9%) when compared with the cigarette group. In addition, changes in CREs involved in lipid metabolism, inflammation, endothelial dysfunction, and platelet activation were favorable in the CTHP 1.2 group, consistent with those observed in the literature upon SC. Lung function parameters exhibited no differences between the two groups, as lung function changes require a longer period. CHTP 1.2 was well accepted and delivered satisfactory nicotine levels. Most of the adverse events were assessed as mild or moderate; none led to discontinuation of the randomized subjects. Conclusions: Switching from cigarettes to CHTP 1.2 resulted in significant reductions in BoExp levels that were associated with favorable changes in some CREs. These results provide evidence that CHTP 1.2 likely reduces the risk of developing smoking-related diseases compared with cigarettes.