An Experimental Analytical and In Vitro Approach to Bridge Between Different Heated Tobacco Product Variants

Summary Tobacco heating products (THPs) have reduced toxicant emissions relative to cigarettes. THPs are continually evolving, but safety and efficacy studies on each new variant involve considerable resources. As employed by the pharmaceutical industry, a “bridging” process could be used to demonstrate product equivalence. Therefore, we investigated the feasibility of a bridging approach by evaluating aerosol emissions and in vitro cytotoxicity of five variant THPs in relation to a base product. All products were compared to a reference cigarette and a commercial benchmark. Relative to smoke, chemical reductions in THP aerosols were comparable among the THPs at 94–97%. The aerosols showed similar cytotoxicity in human lung tissues exposed at the air-liquid interface (p = 0.8378) but were significantly less toxic than smoke (p = 0.04). Relative to the THP benchmark, variant THPs showed lower cytotoxicity (p = 0.0141). Emissions and cytotoxicity data demonstrated that the variant THPs were comparable to the base THP, irrespective of consumable format or flavour. This dataset demonstrates the feasibility of a bridging approach and can inform an evidence-based strategy in developing sufficient data to predict similarity against an already established dataset. Therefore, avoiding repetition of vast data generation could ease authorisation requirements of newer products. Finally, we propose that more work is required to understand chemical, biological (in vitro), human consumption, and clinical data before the equivalence of these products (and others) can be definitively demonstrated. Future studies maybe needed to assess additional chemical and biological outputs and all data will need to be contextualised against human consumption data in terms of a bridging framework.