Background Philip Morris International (PMI) currently claims that its heated tobacco product, IQOS, reduces health risk by reducing users’ exposure to harmful and potentially harmful constituents present in tobacco smoke. Given the tobacco industry’s long history of misrepresenting and obfuscating research, independent assessment of PMI’s claims is important. Analysis of Accord, a failed but strikingly similar precursor to IQOS, may help contextualise PMI’s claims in its Modified Risk Tobacco Product (MRTP) application.

Methods We analysed previously secret internal Philip Morris (PM) and PMI documents, public communications and MRTP application.

Results PM marketed Accord as a ‘cleaner’ tobacco product in an attempt to address smokers’ growing health concerns without making explicit health claims. While PM communications asserted that Accord reduced users’ exposure to harmful constituents, company scientists and executives consistently stressed to both regulators and the public that such reductions did not render Accord safer. IQOS’s design and marketing are similar to Accord’s. On the basis of aerosol chemistry data, IQOS reduces user exposure to some compounds compared with Accord but raises them for others.

Discussion IQOS appears to be a variant of Accord without consistent improvements in exposure to aerosol toxic compounds. In contrast to PM’s past claims for Accord, PMI now claims in its MRTP application that IQOS reduces health risk. This shift in stance is likely not the result of any toxicological difference between Accord and IQOS, but rather a change in the social and regulatory landscape permitting these claims.