Evaluation of the Tobacco Heating System 2.2. Part 4: 90-day OECD 413 rat inhalation study with systems toxicology endpoints demonstrates reduced exposure effects compared with cigarette smoke

Comparison of the toxicological potential of two JUUL ENDS products to reference cigarette 3R4F and filtered air in a 90-day nose-only inhalation toxicity study

Electronic nicotine delivery systems (ENDS) are generally recognized as less harmful alternatives for those who would otherwise continue to smoke cigarettes. The potential toxicity of aerosols generated from JUUL Device and Virginia Tobacco (VT3) or Menthol (ME3) JUULpods at 3.0% nicotine concentration was assessed in rats exposed at target aerosol concentrations of 1400 μg/L for up to 6 h/day on a 5 day/week basis for at least 90 days (general accordance with OECD 413). 3R4F reference cigarette smoke (250 μg/L) and Filtered Air were used as comparators. JUUL ENDS product aerosol exposures at >5x the 3R4F cigarette smoke level resulted in greater plasma nicotine and cotinine levels (up to 2x). Notable cigarette smoke related effects included pronounced body weight reductions in male rats, pulmonary inflammation evidenced by elevated lactate dehydrogenase, pro-inflammatory cytokines and neutrophils in bronchoalveolar lavage fluid, increased heart and lung weights, and minimal to marked respiratory tract histopathology. In contrast, ENDS aerosol exposed animals had minimal body weight changes, no measurable inflammatory changes and minimal to mild laryngeal squamous metaplasia. Despite the higher exposure levels, VT3 and ME3 did not result in significant toxicity or appreciable respiratory histopathology relative to 3R4F cigarette smoke following 90 days administration.

Potential Harm of IQOS Smoke to Rat Liver

The Food and Drug Administration has recently classified the IQOS electronic cigarette as a modified-risk tobacco product. However, IQOS cigarettes still release various harmful constituents typical of conventional cigarettes (CCs), although the concentrations are markedly lower. Here, we investigated the damaging effects of IQOS smoking on the liver. Male Sprague Dawley rats were exposed, whole body, 5 days/week for 4 weeks to IQOS smoke (4 sticks/day), and hepatic xenobiotic metabolism, redox homeostasis and lipidomic profile were investigated. IQOS boosted reactive radicals and generated oxidative stress. Exposure decreased cellular reserves of total glutathione (GSH) but not GSH-dependent antioxidant enzymes. Catalase and xanthine oxidase were greater in the exposed group, as were various hepatic CYP-dependent monooxygenases (CYP2B1/2, CYP1A1, CYP2A1, CYP2E1-linked). Respiratory chain activity was unaltered, while the number of liver mitochondria was increased. IQOS exposure had an impact on the hepatic lipid profile. With regard to the expression of some MAP kinases commonly activated by CC smoking, IQOS increased the p-p38/p38 ratio, while erythroid nuclear transcription factor 2 (Nrf2) was negatively affected. Our data suggest that IQOS significantly impairs liver function, supporting the precautionary stance taken by the WHO toward the use of these devices, especially by young people and pregnant women.

Heated Tobacco Products and Chronic Obstructive Pulmonary Disease: A Narrative Review of Peer-Reviewed Publications

An estimated 65 million people worldwide have moderate or severe chronic obstructive pulmonary disease (COPD), an umbrella term used to describe a group of progressive lung diseases that obstruct airflow such as emphysema and chronic bronchitis. Smoking contributes to an estimated 90% of COPD cases, as the harmful chemicals produced during tobacco combustion damage the lungs and airways. Although smoking cessation is the only intervention shown to improve COPD prognosis in smokers, many patients who try to quit continue to smoke. The continued use of conventional cigarettes exacerbates COPD symptoms, and globally more than 3 million people die from the disease every year. The last two decades have seen the introduction of combustion-free nicotine delivery alternatives that produce significantly lower levels of the harmful components in cigarette smoke, and researchers have begun to assess the impact of switching from cigarettes to these products. Several studies have examined how patients with COPD use e-cigarettes as assistance for quitting, but few have examined how heated tobacco products (HTP) may reduce risk. This narrative review summarises results from pre-clinical, clinical, and real-world evidence studies showing possible harm reduction benefits for patients with COPD who switch to HTPs rather than continuing to smoke cigarettes. Epidemiological studies, real-world data analyses, and randomised clinical trials must be conducted to determine whether switching from cigarettes to HTPs can improve health outcomes in patients with COPD who would otherwise continue to smoke combustible cigarettes.

Alpha-Lipoic Acid Modulates the Oxidative and Inflammatory Responses Induced by Traditional and Novel Tobacco Products in Human Liver Epithelial Cells

Smoking has been associated with NAFLD recently, thus might be a contributing factor for liver disease progression. In this study, we identified the modulative action of α-lipoic acid (α-LA), an organosulphur compound, towards heated tobacco product (HTP) and cigarette smoke extract (CSE)-induced oxidative stress and inflammation in human liver HepG2 cells. The cells were pre-treated with α-LA and exposed to tobacco extracts, and cytotoxicity, oxidative response (SOD, CAT activities and GSH, MDA levels), inflammation (nitrite, IL-6, AhR levels), and liver function (AST/ALT) were assessed. According to the results, a notable increase in oxidative response was observed with CSE, whereas GSH depletion and decreased SOD activity were the key toxicological events induced by HTP (p<0.05). The oxidative and inflammatory responses were ameliorated with α-LA treatment, particularly through GSH restoration and IL-6 modulation. To conclude, these findings on α-LA might contribute to the design of novel adjuvant therapies for people exposed to tobacco smoke.

Preliminary toxicological assessment of heated tobacco products: A review of the literature and proposed strategy

Heated tobacco products (HTP) have become increasingly common in many countries worldwide. The principle of heating tobacco, without combustion, to produce a nicotine-containing aerosol with remarkably reduced levels of other known toxins, compared to combusted tobacco cigarettes, is now well established. As these products are intended as alternatives to traditional combusted products, during the early stages of their development, it is important for manufacturers to ensure that the design of the product does not lead to any unintentionally increased or new risk for the consumer, compared to the traditional products that consumers seek to replace. There is limited guidance from tobacco product regulations concerning the requirements for performing such preliminary toxicological assessments. Here, we review the published literature on studies performed on HTPs in the pursuit of such data, outline a proposed approach that is consistent with regulatory requirements, and provide a logical approach to the preliminary toxicological assessment of HTPs.

Chemical and in vitro toxicological comparison of emissions from a heated tobacco product and the 1R6F reference cigarette

It has previously been found that, compared with cigarette smoke, the aerosols generated by heated tobacco products contain fewer and lower harmful and potentially harmful constituents (HPHCs) and elicit lower biological activity in in vitro models and lower smoking-related exposure biomarker levels in clinical studies. It is important to accumulate such scientific evidences for heated tobacco products with a novel heating system, because different heating system may affect the quantitative aspect of the amount of HPHCs and the qualitative aspect of the biological activity of the aerosol generated. Here, the chemical properties of, and toxicological responses to aerosols emitted by DT3.0a, a new heated tobacco product with a novel heating system, and cigarette smoke (CS) were compared, using chemical analyses, in vitro battery (standardized genotoxicity and cytotoxicity) assays, and mechanistic (ToxTracker and two-dimensional cell culture) assays. Regular- and menthol-flavored DT3.0a and standard 1R6F reference cigarettes were tested. Selected HPHC yields were lower in DT3.0a aerosol than 1R6F CS. The genotoxicity-related assays indicated that DT3.0a aerosol was not genotoxic, regardless of metabolic activation. The other biological assays indicated that less cytotoxicity induction and oxidative stress response were elicited by DT3.0a aerosol compared with 1R6F CS. Similar results were found for both regular and menthol DT3.0a. Like previous reports for heated tobacco products with other heating systems, the results of this study indicated that DT3.0a aerosols have chemical and biological properties less likely to be harmful than 1R6F CS.

Assessment of inhalation toxicity of cigarette smoke and aerosols from flavor mixtures: 5-week study in A/J mice

Most flavors used in e-liquids are generally recognized as safe for oral consumption, but their potential effects when inhaled are not well characterized. In vivo inhalation studies of flavor ingredients in e-liquids are scarce. A structure-based grouping approach was used to select 38 flavor group representatives (FGR) on the basis of known and in silico-predicted toxicological data. These FGRs were combined to create prototype e-liquid formulations and tested against cigarette smoke (CS) in a 5-week inhalation study. Female A/J mice were whole-body exposed for 6 h/day, 5 days/week, for 5 weeks to air, mainstream CS, or aerosols from (1) test formulations containing propylene glycol (PG), vegetable glycerol (VG), nicotine (N; 2% w/w), and flavor (F) mixtures at low (4.6% w/w), medium (9.3% w/w), or high (18.6% w/w) concentration or (2) base formulation (PG/VG/N). Male A/J mice were exposed to air, PG/VG/N, or PG/VG/N/F-high under the same exposure regimen. There were no significant mortality or in-life clinical findings in the treatment groups, with only transient weight loss during the early exposure adaptation period. While exposure to flavor aerosols did not cause notable lung inflammation, it caused only minimal adaptive changes in the larynx and nasal epithelia. In contrast, exposure to CS resulted in lung inflammation and moderate-to-severe changes in the epithelia of the nose, larynx, and trachea. In summary, the study evaluates an approach for assessing the inhalation toxicity potential of flavor mixtures, thereby informing the selection of flavor exposure concentrations (up to 18.6%) for a future chronic inhalation study.

Should IQOS Emissions Be Considered as Smoke and Harmful to Health? A Review of the Chemical Evidence

The chemical evidence that IQOS emissions fit the definition of both an aerosol and smoke, and that IQOS and potentially other heated tobacco products (HTPs) pose some harmful health threats from the range of compounds released even at somewhat lower concentrations is reviewed. Further, we address the yields of harmful and potentially harmful compounds (HPHCs), including polycyclic aromatic hydrocarbons (PAHs), and the constituents of IQOS emission that are diagnostic of pyrolysis to provide information on the temperatures reached in IQOS tobacco sticks. The HPHCs present in IQOS emissions are the same as in conventional cigarette smoke (CCs), analogous to emissions from earlier generation of HTPs classed as smoke. However, Philip Morris International (PMI) studies have to some degree underestimated IQOS aerosol HPHC yields, which are a factor of between 3.2 and 3.6 higher when expressed on a tobacco rather than an IQOS stick basis compared to the reference 3R4F cigarette. Further, IQOS emissions contain carbon particles, which fit definition of both aerosol and smoke. Continual reheating of deposited tar in the IQOS device will occur with real-life use, likely leading to generation of even higher concentrations of HPHCs and particulate matter. Despite IQOS not exceeding 350 °C, local hot spots could exist, causing formation of species (phenol/cresols, PAHs). It is recommended that the impact of repeated use to determine the levels of black carbon (insoluble organic matter) in the particulate matter, and the extent to which compounds in IQOS emissions are formed by pyrolysis need to be assessed rigorously. To address whether uneven temperature profiles in heat sticks can lead to potential hot spots that could, for example, lead to PAH formation, it is recommended that pyrolysis studies on tobacco and other constituents of HTPs are required in conjunction with more effort on heating tobacco blends under controlled temperature/time conditions.

Discriminating Spontaneous From Cigarette Smoke and THS 2.2 Aerosol Exposure-Related Proliferative Lung Lesions in A/J Mice by Using Gene Expression and Mutation Spectrum Data

Mice, especially A/J mice, have been widely employed to elucidate the underlying mechanisms of lung tumor formation and progression and to derive human-relevant modes of action. Cigarette smoke (CS) exposure induces tumors in the lungs; but, non-exposed A/J mice will also develop lung tumors spontaneously with age, which raises the question of discriminating CS-related lung tumors from spontaneous ones. However, the challenge is that spontaneous tumors are histologically indistinguishable from the tumors occurring in CS-exposed mice. We conducted an 18-month inhalation study in A/J mice to assess the impact of lifetime exposure to Tobacco Heating System (THS) 2.2 aerosol relative to exposure to 3R4F cigarette smoke (CS) on toxicity and carcinogenicity endpoints. To tackle the above challenge, a 13-gene gene signature was developed based on an independent A/J mouse CS exposure study, following by a one-class classifier development based on the current study. Identifying gene signature in one data set and building classifier in another data set addresses the feature/gene selection bias which is a well-known problem in literature. Applied to data from this study, this gene signature classifier distinguished tumors in CS-exposed animals from spontaneous tumors. Lung tumors from THS 2.2 aerosol-exposed mice were significantly different from those of CS-exposed mice but not from spontaneous tumors. The signature was also applied to human lung adenocarcinoma gene expression data (from The Cancer Genome Atlas) and discriminated cancers in never-smokers from those in ever-smokers, suggesting translatability of our signature genes from mice to humans. A possible application of this gene signature is to discriminate lung cancer patients who may benefit from specific treatments (i.e., EGFR tyrosine kinase inhibitors). Mutational spectra from a subset of samples were also utilized for tumor classification, yielding similar results. “Landscaping” the molecular features of A/J mouse lung tumors highlighted, for the first time, a number of events that are also known to play a role in human lung tumorigenesis, such as Lrp1b mutation and Ros1 overexpression. This study shows that omics and computational tools provide useful means of tumor classification where histopathological evaluation alone may be unsatisfactory to distinguish between age- and exposure-related lung tumors.

Effects of cigarette smoke exposure on a mouse model of multiple sclerosis

Multiple sclerosis (MS) is an inflammatory autoimmune disease associated with genetic and environmental factors. Cigarette smoking is harmful to health and may be one of the risk factors for MS. However, there have been no systematic investigations under controlled experimental conditions linking cigarette smoke (CS) and MS. The present study is the first inhalation study to correlate the pre-clinical and pathological manifestations affected by different doses of CS exposure in a mouse experimental autoimmune encephalomyelitis (EAE) model. Female C57BL/6 mice were whole-body exposed to either fresh air (sham) or three concentrations of CS from a reference cigarette (3R4F) for 2 weeks before and 4 weeks after EAE induction. The effects of exposure on body weight, clinical symptoms, spinal cord pathology, and serum biochemicals were then assessed. Exposure to low and medium concentrations of CS exacerbated the severity of symptoms and spinal cord pathology, while the high concentration had no effect relative to sham exposure in mice with EAE. Interestingly, the clinical chemistry parameters for metabolic profile as well as liver and renal function (e.g. triglycerides and creatinine levels, alkaline phosphatase activity) were lower in these mice than in naïve controls. Although the mouse EAE model does not fully recapitulate the pathology or symptoms of MS in humans, these findings largely corroborate previous epidemiological findings that exposure to CS can worsen the symptoms and pathology of MS. Furthermore, the study newly highlights the possible correlation of clinical chemistry findings such as metabolism and liver and renal function between MS patients and EAE mice.

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Multiple sclerosis is an inflammatory autoimmune disease affected by many factors.

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First inhalation study to correlate the different doses of cigarette smoke on MS.

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Findings largely corroborate with previous epidemiological findings on CS exposure.

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High concentration of CS had no observable effect on EAE, contrast to low and medium.

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Potential correlation between MS and EAE model using clinical chemistry parameters.

Toxicity evaluation in rats following 28 days of inhalation exposure to xylitol aerosol

Xylitol has reported to decrease gingival inflammation and nasopharyngeal pneumonia, which indicated that xylitol may have potential application in respiratory diseases. Although some studies have reported the inhalation toxicity of xylitol, however, the longest period tested was only for 14 days. The inhalation toxicity of xylitol is insufficient. This work investigated the potential subacute toxicity of xylitol according to the OECD TG 412. Rats were randomly divided into a control group and different dosage groups (2 g/m3, 3 g/m3, 5 g/m3), and exposed for 6 hours/day, 5 days/week for 28 days. At the end of the exposure or recovery period, clinical signs, mortality, body weight, food consumption, hematology, blood biochemistry, gross pathology, organ weight, and histopathology were examined. Compared with the control group, rats of both sexes in the exposure groups exhibited no significant changes in body weight, organ mass, and food uptake. After the xylitol exposure, aspartate aminotransferase activity in the xylitol group (3 g/m3) was significantly higher than that in the control group, while other blood indicators and pathological changes of liver and the analysis of the recovery group showed no changes, suggesting that xylitol exerted no observable toxic effect on the liver. Finally, other observations including the histopathology of target organs and hematology also showed no alterations. These results indicated that xylitol had no significant inhalation toxicity at doses up to 5 g/m3. These subacute inhalation toxicity results of xylitol showed that its no-observed-adverse-effect concentration (NOAEC) in rats was determined to 5 g/m3.

Reduced Chronic Toxicity and Carcinogenicity in A/J Mice in Response to Life-Time Exposure to Aerosol From a Heated Tobacco Product Compared With Cigarette Smoke

We conducted an inhalation study, in accordance with Organisation for Economic Co-operation and Development Test Guideline 453, exposing A/J mice to tobacco heating system (THS) 2.2 aerosol or 3R4F reference cigarette smoke (CS) for up to 18 months to evaluate chronic toxicity and carcinogenicity. All exposed mice showed lower thymus and spleen weight, blood lymphocyte counts, and serum lipid concentrations than sham mice, most likely because of stress and/or nicotine effects. Unlike THS 2.2 aerosol-exposed mice, CS-exposed mice showed increased heart weight, changes in red blood cell profiles and serum liver function parameters. Similarly, increased pulmonary inflammation, altered lung function, and emphysematous changes were observed only in CS-exposed mice. Histopathological changes in other respiratory tract organs were significantly lower in the THS 2.2 aerosol-exposed groups than in the CS-exposed group. Chronic exposure to THS 2.2 aerosol also did not increase the incidence or multiplicity of bronchioloalveolar adenomas or carcinomas relative to sham, whereas CS exposure did. Male THS 2.2 aerosol-exposed mice had a lower survival rate than sham mice, related to an increased incidence of urogenital issues that appears to be related to congenital factors rather than test item exposure. The lower impact of THS 2.2 aerosol exposure on tumor development and chronic toxicity is consistent with the significantly reduced levels of harmful and potentially harmful constituents in THS 2.2 aerosol relative to CS. The totality of the evidence from this study further supports the risk reduction potential of THS 2.2 for lung diseases in comparison with cigarettes.

Respiratory Effects of Exposure to Aerosol From the Candidate Modified-Risk Tobacco Product THS 2.2 in an 18-Month Systems Toxicology Study With A/J Mice

Smoking cessation is the most effective measure for reducing the risk of smoking-related diseases. However, switching to less harmful products (modified-risk tobacco products [MRTP]) can be an alternative to help reduce the risk for adult smokers who would otherwise continue to smoke. In an 18-month chronic carcinogenicity/toxicity study in A/J mice (OECD Test Guideline 453), we assessed the aerosol of Tobacco Heating System 2.2 (THS 2.2), a candidate MRTP based on the heat-not-burn principle, compared with 3R4F cigarette smoke (CS). To capture toxicity- and disease-relevant mechanisms, we complemented standard toxicology endpoints with in-depth systems toxicology analyses. In this part of our publication series, we report on integrative assessment of the apical and molecular exposure effects on the respiratory tract (nose, larynx, and lungs). Across the respiratory tract, we found changes in inflammatory response following 3R4F CS exposure (eg, antimicrobial peptide response in the nose), with both shared and distinct oxidative and xenobiotic responses. Compared with 3R4F CS, THS 2.2 aerosol exerted far fewer effects on respiratory tract histology, including adaptive tissue changes in nasal and laryngeal epithelium and inflammation and emphysematous changes in the lungs. Integrative analysis of molecular changes confirmed the substantially lower impact of THS 2.2 aerosol than 3R4F CS on toxicologically and disease-relevant molecular processes such as inflammation, oxidative stress responses, and xenobiotic metabolism. In summary, this work exemplifies how apical and molecular endpoints can be combined effectively for toxicology assessment and further supports findings on the reduced respiratory health risks of THS 2.2 aerosol.

Exposure to Heated Tobacco Products and Adverse Health Effects, a Systematic Review

Heated tobacco products (HTP) are a form of nicotine delivery intended to be an alternative to traditional cigarettes. HTP tobacco products are sold to consumers as a less harmful alternative to traditional cigarettes, both for users and bystanders. The actual impact of HTP on the health of users and its overall impact on public health is still not fully known. A systematic search of the literature was carried out to identify relevant studies published in English from 2015 to February 2021. The following databases were used: PubMed, Scopus, Elsevier and ClinicalKey. 25 studies (independent and sponsored by the tobacco industry) were considered. The analysis of exposure biomarkers and cardiovascular and respiratory biomarkers showed differences between smokers and people using heated tobacco products. Improvements in clinically relevant risk markers, especially cholesterol, sICAM-1, 8-epi-PGF2α, 11-DTX-B2, HDL and FEV1, were observed compared to persistent cigarette smokers. On the other hand, exposure to IQOS has been reported to alter mitochondrial function, which may further exaggerate airway inflammation, airway remodeling and lung cancer. These products have the potential to increase oxidative stress and increase respiratory tract infections by increasing microbial adherence to the respiratory tract. Our review suggests that HTP products may be products with a reduced risk of chronic diseases, including respiratory and cardiovascular diseases and cancer compared to traditional smoking, although in the case of non-smokers so far, they may pose a risk of their occurrence. Research seems to be necessary to assess the frequency of HTP use and its potential negative health effects.

Comparison of the chemical composition of aerosols from heated tobacco products, electronic cigarettes and tobacco cigarettes and their toxic impacts on the human bronchial epithelial BEAS-2B cells

The electronic cigarettes (e-cigs) and more recently the heated tobacco products (HTP) provide alternatives for smokers as they are generally perceived to be less harmful than conventional cigarettes. However, it is crucial to compare the health risks of these different emergent devices, in order to determine which product should be preferred to substitute cigarette. The present study aimed to compare the composition of emissions from HTP, e-cigs and conventional cigarettes, regarding selected harmful or potentially harmful compounds, and their toxic impacts on the human bronchial epithelial BEAS-2B cells. The HTP emitted less polycyclic aromatic hydrocarbons and carbonyls than the conventional cigarette. However, amounts of these compounds in HTP aerosols were still higher than in e-cig vapours. Concordantly, HTP aerosol showed reduced cytotoxicity compared to cigarette smoke but higher than e-cig vapours. HTP and e-cig had the potential to increase oxidative stress and inflammatory response, in a manner similar to that of cigarette smoke, but after more intensive exposures. In addition, increasing e-cig power impacted levels of certain toxic compounds and related oxidative stress. This study provides important data necessary for risk assessment by demonstrating that HTP might be less harmful than tobacco cigarette but considerably more harmful than e-cig.

Heat-Not-Burn cigarette induces oxidative stress response in primary rat alveolar epithelial cells

There has been an increase in the usage of heat-not-burn (HNB) cigarette products. However, their effects on alveolar epithelial cells (AECs) remain unknown. AECs are the target cells of conventional cigarette smoking-related respiratory diseases such as chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis and lung cancer whose pathogenesis involves oxidative stress. In this study, primary rat AECs were isolated, cultured and stimulated by HNB cigarette smoke extract (CSE). Our data indicate that rat AECs exposed to HNB CSE induced oxidative stress response genes (e.g. Hmox-1, Gsta1, Gsta3 and Nqo1). We also compared the oxidative stress response between two different types of AECs, alveolar type I-like (ATI-like) cells and type II (ATII) cells, and between two different types of cigarette, HNB cigarettes and conventional cigarettes. The expressions of Gsta1, Gsta3 and Nqo1 were higher in ATII cells than ATI-like cells in response to HNB and conventional cigarettes, but there was no significant difference in their expression levels between HNB cigarette and conventional cigarette. Taken together, our results suggest that HNB cigarettes have the similar potential as conventional cigarette products to induce oxidative stress response in AECs.

Impact of switching to a heat-not-burn tobacco product on CYP1A2 activity

Background

Cigarette smoking induces cytochrome P450 1A2 (CYP1A2) expression and activity, while smoking cessation normalizes the levels of this enzyme. The aim of this publication is to summarize the data on CYP1A2 gene expression and activity in preclinical and clinical studies on the Tobacco Heating System (THS), currently marketed as IQOS® with HEETs®, and to summarize the potential effects on CYP1A2 to be expected upon switching to reduced-risk products (RRPs).

Methods

We summarized PMI’s preclinical and clinical data on the effects of switching from cigarette smoking to THS.

Results

Data from four preclinical mouse and rat studies showed that, upon either cessation of cigarette smoke exposure or switching to THS exposure, the upregulation of CYP1A2 observed with exposure to cigarette smoke reverted close to fresh-air levels. Data from four clinical studies yielded similar results on CYP1A2 activity within a time frame of five days. Furthermore, the effects of switching to THS were similar to those seen after smoking cessation.

Conclusions

Because smoking cessation and switching to either electronic cigarettes or THS seem to have similar effects on CYP1A2 activity, the same measures taken for patients treated with narrow therapeutic index drugs that are metabolized by CYP1A2 and who quit smoking should be recommended for those switching to RRPs.

Cancer potencies and margin of exposure used for comparative risk assessment of heated tobacco products and electronic cigarettes aerosols with cigarette smoke

Health risk associated with the use of combustible cigarettes is well characterized and numerous epidemiological studies have been published for many years. Since more than a decade, innovative non-combusted tobacco products have emerged like heated tobacco products (HTP) or electronic cigarettes (EC). Long-term effects of these new products on health remain, however, unknown and there is a need to characterize associated potential health risks. The time dedicated to epidemiological data generation (at least 20 to 40 years for cancer endpoint), though, is not compatible with innovative development. Surrogates need, therefore, to be developed. In this work, non-cancer and cancer risks were estimated in a range of HTP and commercial combustible cigarettes based upon their harmful and potentially harmful constituent yields in aerosols and smoke, respectively. It appears that mean lifetime cancer risk values were decreased by more than one order of magnitude when comparing HTPs and commercial cigarettes, and significantly higher margin of exposure for non-cancer risk was observed for HTPs when compared to commercial cigarettes. The same approach was applied to two commercial ECs. Similar results were also found for this category of products. Despite uncertainties related to the factors used for the calculations and methodological limitations, this approach is valuable to estimate health risks associated to the use of innovative products. Moreover, it acts as predictive tool in absence of long-term epidemiological data. Furthermore, both cancer and non-cancer risks estimated for HTPs and ECs highlight the potential of reduced risk for non-combusted products when compared to cigarette smoking.

Comparing the preclinical risk profile of inhalable candidate and potential candidate modified risk tobacco products: A bridging use case

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Heated tobacco products tested for reduced exposure and reduced risk properties.

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Bridging opportunities for nonclinical results from two heated tobacco products.

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Similarly reduced impact on apical and molecular endpoints relative to cigarettes.

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Evidence evaluated along a “causal chain of events leading to disease” (CELSD).

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Representative assays along CELSD could support nonclinical substantial equivalence.

Cigarette smoking causes major preventable diseases, morbidity, and mortality worldwide. Smoking cessation and prevention of smoking initiation are the preferred means for reducing these risks. Less harmful tobacco products, termed modified-risk tobacco products (MRTP), are being developed as a potential alternative for current adult smokers who would otherwise continue smoking. According to a regulatory framework issued by the US Food and Drug Administration, a manufacturer must provide comprehensive scientific evidence that the product significantly reduces harm and the risk of tobacco-related diseases, in order to obtain marketing authorization for a new MRTP. For new tobacco products similar to an already approved predicate product, the FDA has foreseen a simplified procedure for assessing “substantial equivalence”. In this article, we present a use case that bridges the nonclinical evidence from previous studies demonstrating the relatively reduced harm potential of two heat-not-burn products based on different tobacco heating principles. The nonclinical evidence was collected along a “causal chain of events leading to disease” (CELSD) to systematically follow the consequences of reduced exposure to toxicants (relative to cigarette smoke) through increasing levels of biological complexity up to disease manifestation in animal models of human disease. This approach leverages the principles of systems biology and toxicology as a basis for further extrapolation to human studies. The experimental results demonstrate a similarly reduced impact of both products on apical and molecular endpoints, no novel effects not seen with cigarette smoke exposure, and an effect of switching from cigarettes to either MRTP that is comparable to that of complete smoking cessation. Ideally, a subset of representative assays from the presented sequence along the CELSD could be sufficient for predicting similarity or substantial equivalence in the nonclinical impact of novel products; this would require further validation, for which the present use case could serve as a starting point.

Evaluation of toxicity of aerosols from flavored e-liquids in Sprague-Dawley rats in a 90-day OECD inhalation study, complemented by transcriptomics analysis

The use of flavoring substances is an important element in the development of reduced-risk products for adult smokers to increase product acceptance and encourage switching from cigarettes. In a first step towards characterizing the sub-chronic inhalation toxicity of neat flavoring substances, a study was conducted using a mixture of the substances in a base solution of e-liquid, where the standard toxicological endpoints of the nebulized aerosols were supplemented with transcriptomics analysis. The flavor mixture was produced by grouping 178 flavors into 26 distinct chemical groups based on structural similarities and potential metabolic and biological effects. Flavoring substances predicted to show the highest toxicological effect from each group were selected as the flavor group representatives (FGR). Following Organization for Economic Cooperation and Development Testing Guideline 413, rats were exposed to three concentrations of the FGR mixture in an e-liquid composed of nicotine (23 µg/L), propylene glycol (1520 µg/L), and vegetable glycerin (1890 µg/L), while non-flavored and no-nicotine mixtures were included as references to identify potential additive or synergistic effects between nicotine and the flavoring substances. The results indicated that the inhalation of an e-liquid containing the mixture of FGRs caused very minimal local and systemic toxic effects. In particular, there were no remarkable clinical (in-life) observations in flavored e-liquid-exposed rats. The biological effects related to exposure to the mixture of neat FGRs were limited and mainly nicotine-mediated, including changes in hematological and blood chemistry parameters and organ weight. These results indicate no significant additive biological changes following inhalation exposure to the nebulized FGR mixture above the nicotine effects measured in this sub-chronic inhalation study. In a subsequent study, e-liquids with FGR mixtures will be aerosolized by thermal treatment and assessed for toxicity.

A 6-month systems toxicology inhalation study in ApoE-/- mice demonstrates reduced cardiovascular effects of E-vapor aerosols compared with cigarette smoke

Smoking cigarettes is harmful to the cardiovascular system. Considerable attention has been paid to the reduced harm potential of alternative nicotine-containing inhalable products such as e-cigarettes. We investigated the effects of E-vapor aerosols or cigarette smoke (CS) on atherosclerosis progression, cardiovascular function, and molecular changes in the heart and aorta of female apolipoprotein E-deficient (ApoE^-/-) mice. The mice were exposed to aerosols from three different E-vapor formulations: 1) carrier (propylene glycol and vegetable glycerol), 2) base (carrier and nicotine), or 3) test (base and flavor) or to CS from 3R4F reference cigarettes for up to 6 mo. Concentrations of CS and base or test aerosols were matched at 35 µg nicotine/L. Exposure to CS, compared with sham-exposed fresh air controls, accelerated atherosclerotic plaque formation, whereas no such effect was seen for any of the three E-vapor aerosols. Molecular changes indicated disease mechanisms related to oxidative stress and inflammation in general, plus changes in calcium regulation, and altered cytoskeletal organization and microtubule dynamics in the left ventricle. While ejection fraction, fractional shortening, cardiac output, and isovolumic contraction time remained unchanged following E-vapor aerosols exposure, the nicotine-containing base and test aerosols caused an increase in isovolumic relaxation time similar to CS. A nicotine-related increase in pulse wave velocity and arterial stiffness was also observed, but it was significantly lower for base and test aerosols than for CS. These results demonstrate that in comparison with CS, E-vapor aerosols induce substantially lower biological responses associated with smoking-related cardiovascular diseases.NEW & NOTEWORTHY Analysis of key urinary oxidative stress markers and proinflammatory cytokines showed an absence of oxidative stress and inflammation in the animals exposed to E-vapor aerosols. Conversely, animals exposed to conventional cigarette smoke had high urinary levels of these markers. When compared with conventional cigarette smoke, E-vapor aerosols induced smaller atherosclerotic plaque surface area and volume. Systolic and diastolic cardiac function, as well as endothelial function, were further significantly less affected by electronic cigarette aerosols than conventional cigarette smoke. Molecular analysis demonstrated that E-vapor aerosols induce significantly smaller transcriptomic dysregulation in the heart and aorta compared with conventional cigarette smoke.

State-of-the-art methods and devices for the generation, exposure, and collection of aerosols from heat-not-burn tobacco products

Tobacco harm reduction is increasingly recognized as a promising approach to accelerate the decline in smoking prevalence and smoking-related population harm. Potential modified risk tobacco products (MRTPs) must undergo a rigorous premarket toxicological risk assessment. The ability to reproducibly generate, collect, and use aerosols is critical for the characterization, and preclinical assessment of aerosol-based candidate MRTPs (cMRTPs), such as noncombusted cigarettes, also referred to as heated tobacco products, tobacco heating products, or heat-not-burn (HNB) tobacco products. HNB tobacco products generate a nicotine-containing aerosol by heating tobacco instead of burning it. The aerosols generated by HNB products are qualitatively and quantitatively highly different from cigarette smoke (CS). This constitutes technical and experimental challenges comparing the toxicity of HNB aerosols with CS. The methods and experimental setups that have been developed for the study of CS cannot be directly transposed to the study of HNB aerosols. Significant research efforts are dedicated to the development, characterization, and validation of experimental setups and methods suitable for HNB aerosols. They are described in this review, with a particular focus on the Tobacco Heating System version 2.2. This is intended to support further studies, the objective evaluation and verification of existing evidence, and the development of scientifically substantiated HNB MRTPs.

Chemical Analysis and Simulated Pyrolysis of Tobacco Heating System 2.2 Compared to Conventional Cigarettes

Introduction

Tobacco Heating System 2.2 (THS 2.2, marketed as iQOS) is a heat-not-burn (HNB) tobacco product that has been successfully introduced to global markets. Despite its expanding market, few independent and systematic researches into THS 2.2 have been carried out to date.

Methods

We tested a comprehensive list of total particulate matter (TPM), water, tar, nicotine, propylene glycol, glycerin, carbon monoxide, volatile organic compounds, aromatic amines, hydrogen cyanide, ammonia, N-nitrosamines, phenol, and polycyclic aromatic hydrocarbon under both ISO and HCI regimes. We also simulated pyrolysis of THS 2.2 heating sticks and made comparisons with conventional cigarette tobacco fillers using comprehensive gas chromatography-mass spectrometry (GC × GC-MS) to determine whether the specially designed ingredients help reduce harmful constituents.

Results

Other than some carbonyls, ammonia, and N-nitrosoanabasine (NAB), the delivered releases from THS 2.2 were at least 80% lower than those from 3R4F. Tar and nicotine remained almost the same as 3R4F. Interestingly, the normalized yield of THS 2.2 to 3R4F under the HCI regime was lower than that under the ISO regime.

Conclusions

THS 2.2 delivered fewer harmful constituents than the conventional cigarette 3R4F. Simulated pyrolysis results showed that the lower temperature instead of specially designed ingredients contributed to the distinct shift. In particular, if smoking machines are involved to evaluate the HNB products, smoking regimes of heat-not-burn tobacco products should be carefully chosen.

Implications

To our knowledge, few independent studies of HNB products have been published. In this paper, a comprehensive list of chemical releases was tested systematically and compared to those from 3R4F. Although THS 2.2 generates lower levels of harmful constituents, the nicotine and tar levels were almost identical to 3R4F.The results should be discussed carefully in the future when assessing the dual-use with other conventional cigarettes, nicotine dependence of HNB products, etc. This study also suggests that regulatory agencies should pay attention to the smoking regimes that are adopted to evaluate HNB tobacco products.

Modeling drug exposure in rodents using e-cigarettes and other electronic nicotine delivery systems

Smoking tobacco products is the leading cause of preventable death worldwide. Coordinated efforts have successfully reduced tobacco cigarette smoking in the United States; however, electronic cigarettes (e-cigarette) and other electronic nicotine delivery systems (ENDS) recently have replaced traditional cigarettes for many users. While the clinical risks associated with long-term ENDS use remain unclear, advancements in preclinical rodent models will enhance our understanding of their overall health effects. This review examines the peripheral and central effects of ENDS-mediated exposure to nicotine and other drugs of abuse in rodents and evaluates current techniques for implementing ENDS in preclinical research.

Toxicological assessment of Tobacco Heating System 2.2: Findings from an independent peer review

Offering safer alternatives to cigarettes, such as e-cigarettes and heated tobacco products, to smokers who are not willing to quit could reduce the harm caused by smoking. Extensive and rigorous scientific studies are conducted to assess the relative risk of such potentially modified risk tobacco products compared with that of smoking cigarettes. In addition to the peer review of publications reporting individual studies, we aimed to gauge the plausibility of the evidence to the scientific community and appreciate likely necessary additions prior to regulatory submission. Therefore, we sponsored a two-tier peer review organized by an independent third party who identified, recruited, and managed 7 panels of 5-12 experts whose identity remains unknown to us. The reviewers had access to all publications and raw data from preclinical and clinical studies via a web portal. The reviewers were asked questions regarding study design, methods, quality of data, and interpretation of results to judge the validity of the conclusions regarding the relative effects of the Tobacco Heating System 2.2 compared with cigarettes. Once their conclusions were submitted, the experts had the opportunity to participate in an anonymized online debate with their fellow panel members. We present here the results obtained from this innovative peer review effort which revealed supportive or very supportive of the study methods and results, and support the robustness of the studies and validity of the conclusions.

Household Surveys in the General Population and Web-Based Surveys in IQOS Users Registered at the Philip Morris International IQOS User Database: Protocols on the Use of Tobacco- and Nicotine-Containing Products in Germany, Italy, and the United Kingdom (Greater London), 2018-2020

Background

Philip Morris International (PMI) has developed a novel heat-not-burn tobacco product, Tobacco Heating System (THS), which is marketed under the brand name of IQOS with HEETS (IQOS). The aerosol generated by THS has substantially fewer toxicants than combustible cigarette smoke, although the extent of the reduction of harmful and potentially harmful constituents reported varies between studies. To evaluate the potential harm reduction associated with IQOS use, the assessment of the uptake and continued use of IQOS in the context of all other tobacco- and nicotine-containing products is crucial. In March 2018, PMI launched cross-sectional surveys in Germany, Italy, and the United Kingdom (Greater London) to estimate the prevalence and use patterns of IQOS and other tobacco- and nicotine-containing products use in these 3 markets following the commercialization of IQOS. This study describes the protocol of the surveys.

Objective

The objectives of these surveys are to estimate the prevalence of tobacco- and nicotine-containing products use; describe past and current patterns of use; and explore their associations with self-reported health, motivation to use, risk perceptions, and perceived aesthetic changes.

Methods

The overall design of the surveys is similar in all 3 countries. Repeated cross-sectional surveys are being conducted annually over 3 consecutive years (2018 to 2020) and in 2 samples: a representative sample of the general population and a sample of IQOS users. A total of 6085 adults per year will be selected from the general population for each survey through multistage stratified sampling, and participants will respond to face-to-face computer-assisted personal interviews. In addition, 1404, 1384, and 1246 IQOS users per year in Germany, Italy, and Greater London, respectively, will be randomly selected from the PMI IQOS user database and will be invited to complete the Web-based survey using computer-assisted self-interviews. The Smoking Questionnaire is used to assess the tobacco use patterns of the participants.

Results

The recruitment of the general population sample began in March 2018 and that of the IQOS user sample began in April 2018. The data collection is ongoing, and the results of the first year data analysis are expected to be available by June 2019.

Conclusions

As the design of the 3 surveys is similar, the results will allow for cross-countries comparison of the prevalence of IQOS and other tobacco- and nicotine-containing products use as well as patterns of use and associated factors.

International Registered Report Identifier (IRRID)

DERR1-10.2196/12061

Mainstream smoke constituents and in vitro toxicity comparative analysis of 3R4F and 1R6F reference cigarettes

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3R4F Kentucky reference cigarettes stock is depleting.

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3R4F reference cigarettes have been widely used as monitor or comparator.

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1R6F reference cigarettes are a suitable replacement for 3R4F on the basis of smoke chemistry and in vitro assays.

A new Kentucky reference cigarette, 1R6F, has been manufactured to replace the depleting 3R4F reference cigarette. The 3R4F Kentucky reference cigarettes have been widely used as monitor or comparator cigarettes for mainstream smoke analysis and in vitro and in vivo toxicological data of cigarettes and novel tobacco products. Both reference cigarettes were analyzed in the same laboratory during the same period of time with the goal of performing a comparison of 3R4F and 1R6F. On the basis of the results obtained from aerosol chemistry and in vitro assays, we consider that the 1R6F reference cigarette is a suitable replacement for the 3R4F reference cigarette as a comparator/monitor cigarette. Its specific use as a comparator for novel tobacco products was checked on the basis of a comparative test with the Tobacco Heating System 2.2 as an example.

Potential predictors of adoption of the Tobacco Heating System by U.S. adult smokers: An actual use study

Background: This was a pre-market, observational, actual use study with the Tobacco Heating System (THS), a candidate modified risk tobacco product. The main goal of the study was to describe THS adoption within current adult daily smokers by replicating the usage of THS in real-world conditions with participants being able to consume cigarettes, THS, and any other nicotine-containing products (e.g., e-cigarettes, cigars, etc.) ad libitum. Methods: This study assessed self-reported stick-by-stick consumption of THS compared with the use of commercial cigarettes over six weeks. The aim of the analysis was to identify potential predictors for adoption of THS using stepwise logistic regression analysis. Results: By the end of the observational period (in Week 6), 14.6% of participants (n=965) had adopted THS meaning that THS formed 70% or more of their total tobacco consumption. The main predictors of adoption were the liking of the smell, taste, aftertaste, and ease of use of THS. The proportion of adoption was higher in participants aged 44 years and older and in Hispanic or Latino adult smokers. Additionally, adoption of THS was more likely in participants who had never attempted to quit smoking and in participants who smoked up to 10 cigarettes per day. Finally, the adoption of THS was higher in participants who consumed both regular and menthol THS compared with those who consumed only one THS variant. Conclusions: The findings suggest that the introduction of THS in the U.S. has the potential to result in adoption by current adult smokers who would otherwise continue to smoke cigarettes, and that the adoption of THS is unlikely to result in an increase of tobacco consumption. Post-marketing studies will provide further insights on THS adoption and THS use patterns to allow assessment of the impact of the THS at the individual and the overall population level.

Potential predictors of adoption of the Tobacco Heating System by U.S. adult smokers: An actual use study

Background: This was a pre-market actual use study with the Tobacco Heating System (THS), a candidate modified risk tobacco product, conducted with adult smokers in eight cities in the United States. The main goal of the study was to describe THS adoption in a real-world setting. The aim of this analysis was to identify potential predictors for adoption of THS using stepwise logistic regression method. Methods: This actual use study was an observational study assessing self-reported stick-by-stick consumption of the THS product compared with the use of commercial cigarettes over six weeks. The study aimed at replicating the usage of THS in real-world conditions with participants being able to consume cigarettes, THS, and any other nicotine-containing products (e.g., e-cigarettes, cigars, etc.) ad libitum. Results: 14.6% of participants adopted THS, which comprised 70% or more of their total tobacco consumption by the end of the observational period (in Week 6). The main predictors of adoption were the liking of the smell, taste, aftertaste, and ease of use of THS. The proportion of adoption was higher in participants aged 44 years and older and in Hispanic or Latino adult smokers. Additionally, adoption of THS was more likely in participants who had never attempted to quit smoking and in participants who smoked up to 10 cigarettes per day. Finally, the adoption of THS was higher in participants who consumed both regular and menthol THS compared with those who consumed only one THS variant. Conclusions: The main predictors of THS adoption were positive sensory assessment and the ease of use. Socio-demographic characteristics and smoking habits appeared much less important. Post-marketing studies will provide further insights on the impact of the THS at the individual and the overall population level.

[Systematic analysis of the scientific literature on heated tobacco]

INTRODUCTION

The tobacco industry (TI) reports that heated tobacco reduces risk of tobacco use and will replace cigarettes. An analysis of the scientific literature was conducted in order to enlighten professionals and decision-makers.

METHOD

After a Medline query in February 2018, a systematic analysis was conducted.

RESULTS

Of the 100 papers published in 2008-2018, 75 have authors affiliated or linked to TI. Emissions contain gases, droplets and solid particles, so are smokes. The main products are: THS2.2 (Iqos®) which heats mini-cigarettes at 340°C, the THP1.0 (Glo®) which heats at 240°C sticks delivering about half as much nicotine, Ploom® which uses reconstituted tobacco microcapsules heated at 180°C. Under the experimental conditions, there is a reduction of toxic emissions and biological effects, but the expected risk reduction is not demonstrated. Symptoms related to passive smoking are described. The 4 epidemiological articles report that heated tobacco is used in 10 to 45% of cases by non-smokers and demonstrate the effectiveness of TI promotion campaigns. Thus, the THS2.2 is more a gateway to smoking (20%) than an exit door (11%); moreover, it is not expected risk reduction among the 69% who are mixed users.

CONCLUSIONS

While reducing emissions is documented, reducing the risk to the smoker who switches to heated-tobacco remains to be demonstrated. On the other hand, the worsening of the global tobacco risk related to the promotion of the products by the TI is anticipated, justifying that the authorities take the appropriate measures to control the promotion of heated tobacco.

IQOSTM vs. e-Cigarette vs. Tobacco Cigarette: A Direct Comparison of Short-Term Effects after Overnight-Abstinence

Introduction: Research from Philip Morris International's science division on its Heat-not-Burn product IQOSTM focused on its chemical, toxicological, clinical, and behavioral aspects. Independent research on the experiences and behavioral aspects of using IQOSTM, and how it compares to e-cigarettes, is largely lacking. The current randomized, cross-over behavioral trial tried to bridge the latter gaps. Methods: Participants (n = 30) came to the lab on three consecutive days after being overnight smoking abstinent. During each session, participants used one of three products (cigarette, e-cigarette, or IQOSTM) for five minutes. Exhaled CO (eCO) measurements and questionnaires were repeatedly administered throughout the session. Results: Smoking a cigarette for five minutes resulted in a significant increase of eCO, whereas using an IQOSTM resulted in a small but reliable increase (0.3 ppm). Vaping did not affect eCO. Cigarette craving reduced significantly after product use, with the decline being stronger for smoking than for e-cigarettes or IQOSTM. Withdrawal symptoms declined immediately after smoking or using IQOSTM, and with some delay after vaping. IQOSTM scored higher in terms of subjective reward/satisfaction and was slightly preferred to the e-cigarette. Discussion: Short-term use of IQOSTM has a minimal impact on eCO, is equally effective in reducing cigarette craving and withdrawal symptoms as an e-cigarette, and is slightly preferred.

Vascular endothelial function is impaired by aerosol from a single IQOS HeatStick to the same extent as by cigarette smoke

BACKGROUND

Heated tobacco products (also called 'heat-not-burn' products) heat tobacco at temperatures below that of combustion, causing nicotine and other compounds to aerosolise. One such product, IQOS from Philip Morris International, is being marketed internationally with claims of harm reduction. We sought to determine whether exposure to IQOS aerosol impairs arterial flow-mediated dilation (FMD), a measure of vascular endothelial function that is impaired by tobacco smoke.

METHODS

We exposed anaesthetised rats (n=8/group) via nose cone to IQOS aerosol from single HeatSticks, mainstream smoke from single Marlboro Red cigarettes or clean air for a series of consecutive 30 s cycles over 1.5-5 min. Each cycle consisted of 15 or 5 s of exposure followed by removal from the nose cone. We measured pre-exposure and postexposure FMD, and postexposure serum nicotine and cotinine.

RESULTS

FMD was impaired comparably by ten 15 s exposures and ten 5 s exposures to IQOS aerosol and to cigarette smoke, but not by clean air. Serum nicotine levels were similar to plasma levels after humans have smoked one cigarette, confirming that exposure conditions had real-world relevance. Postexposure nicotine levels were ~4.5-fold higher in rats exposed to IQOS than to cigarettes, despite nicotine being measured in the IQOS aerosol at ~63% the amount measured in smoke. When IQOS exposure was briefer, leading to comparable serum nicotine levels to the cigarette group, FMD was still comparably impaired.

CONCLUSIONS

Acute exposures to IQOS aerosol impairs FMD in rats. IQOS use does not necessarily avoid the adverse cardiovascular effects of smoking cigarettes.

Cytotoxic effects of heated tobacco products (HTP) on human bronchial epithelial cells

BACKGROUND

Heated tobacco product(s) (HTP), also called heat-not-burn products, are a re-emerging class of tobacco products that purport to reduce health risk compared with smoking combustible tobacco products. This study examined the potential toxic effects of inhaling emissions from an HTP in comparison with electronic and combustible tobacco cigarettes.

METHODS

Inhalation toxicity of HTP (IQOS; tobacco flavour), e-cigarette (MarkTen; tobacco flavour) and tobacco cigarette (Marlboro Red) was examined in vitro using an air-liquid interface with human bronchial epithelial cells (H292). Cells were exposed directly to 55 puffs from the e-cigarette, 12 puffs from the HTP and 8 puffs from the tobacco cigarette to equilibrate nicotine delivery to the cells across products. Cytotoxicity was measured using neutral red uptake and trypan blue assays. Cytotoxic effects of each tested product (HTP, e-cigarette and tobacco cigarette) were compared with an air control. Release of inflammatory markers (cytokines) was measured using ELISA.

RESULTS

The HTP showed higher cytotoxicity compared with the air controls using the neutral red assay. The HTP also showed higher cytotoxicity than the e-cigarette, but lower cytotoxicity than the combustible cigarettes using the same assay. A significant increase in cytokines levels, compared with air controls, was observed postexposure to tobacco smoke but not to emissions from HTP or e-cigarette aerosol.

DISCUSSION

Using limited cytotoxic measures, the HTP showed reduced cytotoxicity relative to a combustible cigarette but higher toxicity than an e-cigarette. More comprehensive testing is needed to determine long-term effects of inhaling emissions from HTP.

Assessment of industry data on pulmonary and immunosuppressive effects of IQOS

Introduction

Heated tobacco products are being touted as novel reduced-harm tobacco products by tobacco companies. In the USA, Philip Morris International submitted a modified risk tobacco product (MRTP) application to the US Food and Drug Administration in 2016 in which it purports that its heated tobacco product, I-Quit-Ordinary-Smoking (IQOS), is associated with reduced harm compared with conventional cigarettes.

Methods

We reviewed Philip Morris International’s MRTP application to assess the pulmonary and immune toxicities associated with IQOS use in both animal and human studies.

Results

Among rats exposed to IQOS, there was evidence of pulmonary inflammation and immunomodulation. In human users, there was no evidence of improvement in pulmonary inflammation or pulmonary function in cigarette smokers who were switched to IQOS.

Conclusion

IQOS is associated with significant pulmonary and immunomodulatory toxicities with no detectable differences between conventional cigarette smokers and those who were switched to IQOS in Philip Morris International’s studies. Philip Morris International also failed to consider how dual use and secondhand aerosol exposure may further impact, and likely increase, the harms associated with these products.

A 90-day OECD TG 413 rat inhalation study with systems toxicology endpoints demonstrates reduced exposure effects of the aerosol from the carbon heated tobacco product version 1.2 (CHTP1.2) compared with cigarette smoke. I. Inhalation exposure, clinical pathology and histopathology

Within the framework of a systems toxicology approach, the inhalation toxicity of aerosol from a novel tobacco-heating potentially modified risk tobacco product (MRTP), the carbon-heated tobacco product (CHTP) 1.2, was characterized and compared with that of mainstream smoke (CS) from the 3R4F reference cigarette in a 90-day nose-only rat inhalation study in general accordance with OECD TG 413. CHTP1.2 is a heat-not-burn product using a carbon heat source to produce an aerosol that contains nicotine and tobacco flavor. At equal or twice the nicotine concentration in the test atmospheres, inhalation of CHTP1.2 aerosol led to a significantly lower exposure to harmful constituents and induced less respiratory tract irritation, systemic, and pathological effects compared with CS. Nasal epithelial changes were less pronounced in the CHTP1.2- than in the CS-exposed groups and reverted in the nicotine concentration-matched group after a recovery period. Lung inflammation was minimal in the CHTP1.2-treated groups compared with the moderate extent seen in the 3R4F groups. Many other toxicological endpoints evaluated did not show CHTP1.2 aerosol exposure-related effects, and no effects not seen for 3R4F were observed. These observations were consistent with findings from previous studies in which rats were exposed to MRTP aerosols containing similar nicotine concentrations.

Mechanisms of toxicity and biomarkers of flavoring and flavor enhancing chemicals in emerging tobacco and non-tobacco products

Tobacco products containing flavorings, such as electronic nicotine delivery devices (ENDS) or e-cigarettes, cigars/cigarillos, waterpipes, and heat-not-burn devices (iQOS) are continuously evolving. In addition to increasing the exposure of teenagers and adults to nicotine containing flavoring products and flavoring enhancers, chances of nicotine addiction through chronic use and abuse also increase. These flavorings are believed to be safe for ingestion, but little information is available about their effects on the lungs. In this review, we have discussed the in vitro and in vivo data on toxicity of flavoring chemicals in lung cells. We have further discussed the common flavoring agents, such as diacetyl and menthol, currently available detection methods, and the toxicological mechanisms associated with oxidative stress, inflammation, mucociliary clearance, and DNA damage in cells, mice, and humans. Finally, we present potential biomarkers that could be utilized for future risk assessment. This review provides crucial parameters important for evaluation of risk associated with flavoring agents and flavoring enhancers used in tobacco products and ENDS. Future studies can be designed to address the potential toxicity of inhaled flavorings and their biomarkers in users as well as in chronic exposure studies.

Assessment of mitochondrial function following short- and long-term exposure of human bronchial epithelial cells to total particulate matter from a candidate modified-risk tobacco product and reference cigarettes

Mitochondrial dysfunction caused by cigarette smoke is involved in the oxidative stress-induced pathology of airway diseases. Reducing the levels of harmful and potentially harmful constituents by heating rather than combusting tobacco may reduce mitochondrial changes that contribute to oxidative stress and cell damage. We evaluated mitochondrial function and oxidative stress in human bronchial epithelial cells (BEAS 2B) following 1- and 12-week exposures to total particulate matter (TPM) from the aerosol of a candidate modified-risk tobacco product, the Tobacco Heating System 2.2 (THS2.2), in comparison with TPM from the 3R4F reference cigarette. After 1-week exposure, 3R4F TPM had a strong inhibitory effect on mitochondrial basal and maximal oxygen consumption rates compared to TPM from THS2.2. Alterations in oxidative phosphorylation were accompanied by increased mitochondrial superoxide levels and increased levels of oxidatively damaged proteins in cells exposed to 7.5 μg/mL of 3R4F TPM or 150 μg/mL of THS2.2 TPM, while cytosolic levels of reactive oxygen species were not affected. In contrast, the 12-week exposure indicated adaptation of BEAS-2B cells to long-term stress. Together, the findings indicate that 3R4F TPM had a stronger effect on oxidative phosphorylation, gene expression and proteins involved in oxidative stress than TPM from the candidate modified-risk tobacco product THS2.2.

A 90-day OECD TG 413 rat inhalation study with systems toxicology endpoints demonstrates reduced exposure effects of the aerosol from the carbon heated tobacco product version 1.2 (CHTP1.2) compared with cigarette smoke. II. Systems toxicology assessment

Modified risk tobacco products (MRTPs) have the potential to reduce smoking-related health risks. The Carbon Heated Tobacco Product 1.2 (CHTP1.2) is a potential MRTP that uses a pressed carbon heat source to generate an aerosol by heating tobacco. Here, we report the results from the systems toxicology arm of a 90-day rat inhalation study (OECD test guideline 413) to assess the effects of CHTP1.2 aerosol compared with cigarette smoke (CS). Transcriptomics, proteomics, and lipidomics analyses complemented the standard endpoints. In the respiratory nasal epithelium, CS induced an adaptive tissue and inflammatory response, which was much weaker after CHTP1.2 aerosol exposure, mostly limited to the highest CHTP1.2 concentration (at twice the 3R4F CS concentration: 50 vs. 23 μg nicotine/L), in female rats. In the lungs, the effects of CS exposure included inflammatory and cellular stress responses, which were absent or much lower after CHTP1.2 aerosol exposure. Outside of the respiratory tract, CS and CHTP1.2 aerosol induced effects that were previously associated with exposure to any nicotine-containing aerosol, e.g., lower lipid concentrations in serum. Overall, this systems toxicology analysis complements and confirms the results from classical toxicological endpoints and further suggests potentially reduced respiratory health risks of CHTP1.2.

iQOS: evidence of pyrolysis and release of a toxicant from plastic

OBJECTIVE

To evaluate performance of the I quit original smoking (iQOS) heat-not-burn system as a function of cleaning and puffing topography, investigate the validity of manufacturer's claims that this device does not burn tobacco and determine if the polymer-film filter is potentially harmful.

METHODS

iQOS performance was evaluated using five running conditions incorporating two different cleaning protocols. Heatsticks were visually and stereomicroscopically inspected preuse and postuse to determine the extent of tobacco plug charring (from pyrolysis) and polymer-film filter melting, and to elucidate the effects of cleaning on charring. Gas chromatography-mass spectrometry headspace analysis was conducted on unused polymer-film filters to determine if potentially toxic chemicals are emitted from the filter during heating.

RESULTS

For all testing protocols, pressure drop decreased as puff number increased. Changes in testing protocols did not affect aerosol density. Charring due to pyrolysis (a form of organic matter thermochemical decomposition) was observed in the tobacco plug after use. When the manufacturer's cleaning instructions were followed, both charring of the tobacco plug and melting of the polymer-film filter increased. Headspace analysis of the polymer-film filter revealed the release of formaldehyde cyanohydrin at 90°C, which is well below the maximum temperature reached during normal usage.

DISCUSSION

Device usage limitations may contribute to decreases in interpuff intervals, potentially increasing user's intake of nicotine and other harmful chemicals. This study found that the tobacco plug does char and that charring increases when the device is not cleaned between heatsticks. Release of formaldehyde cyanohydrin is a concern as it is highly toxic at very low concentrations.

Indoor air quality (IAQ) evaluation of a Novel Tobacco Vapor (NTV) product

The impact of using a Novel Tobacco Vapor (NTV) product on indoor air quality (IAQ) was simulated using an environmentally-controlled chamber. Three environmental simulations were examined; two non-smoking areas (conference room and dining room) and one ventilated smoking area (smoking lounge). IAQ was evaluated by (i) measuring constituents in the mainstream NTV product emissions, (ii) and by determining classical environmental tobacco smoke (ETS) and representative air quality markers. Analysis of the mainstream emissions revealed that vapor from the NTV product is chemically simpler than cigarette smoke. ETS markers (RSP, UVPM, FPM, solanesol, nicotine, 3-ethenylpyridine), volatile organic compound (toluene), carbon monoxide, propylene glycol, glycerol, and triacetin were below the limit of detection or the limit of quantification in both the non-smoking and smoking environments after using the NTV product. The concentrations of ammonia, carbonyls (formaldehyde, acetaldehyde, and acetone), and total volatile organic compounds were the same levels found in the chamber without NTV use. There was no significant increase in the levels of formaldehyde, acetone or ammonia in exhaled breath following NTV use. In summary, under the simulations tested, the NTV product had no measurable effect on the IAQ, in either non-smoking or smoking areas.

Toxicity of the main electronic cigarette components, propylene glycol, glycerin, and nicotine, in Sprague-Dawley rats in a 90-day OECD inhalation study complemented by molecular endpoints

While the toxicity of the main constituents of electronic cigarette (ECIG) liquids, nicotine, propylene glycol (PG), and vegetable glycerin (VG), has been assessed individually in separate studies, limited data on the inhalation toxicity of them is available when in mixtures. In this 90-day subchronic inhalation study, Sprague-Dawley rats were nose-only exposed to filtered air, nebulized vehicle (saline), or three concentrations of PG/VG mixtures, with and without nicotine. Standard toxicological endpoints were complemented by molecular analyses using transcriptomics, proteomics, and lipidomics. Compared with vehicle exposure, the PG/VG aerosols showed only very limited biological effects with no signs of toxicity. Addition of nicotine to the PG/VG aerosols resulted in effects in line with nicotine effects observed in previous studies, including up-regulation of xenobiotic enzymes (Cyp1a1/Fmo3) in the lung and metabolic effects, such as reduced serum lipid concentrations and expression changes of hepatic metabolic enzymes. No toxicologically relevant effects of PG/VG aerosols (up to 1.520  mg PG/L + 1.890 mg VG/L) were observed, and no adverse effects for PG/VG/nicotine were observed up to 438/544/6.6 mg/kg/day. This study demonstrates how complementary systems toxicology analyses can reveal, even in the absence of observable adverse effects, subtoxic and adaptive responses to pharmacologically active compounds such as nicotine.

Evaluation of the Tobacco Heating System 2.2 (THS2.2). Part 5: microRNA expression from a 90-day rat inhalation study indicates that exposure to THS2.2 aerosol causes reduced effects on lung tissue compared with cigarette smoke

Modified-risk tobacco products (MRTP) are designed to reduce the individual risk of tobacco-related disease as well as population harm compared to smoking cigarettes. Experimental proof of their benefit needs to be provided at multiple levels in research fields. Here, we examined microRNA (miRNA) levels in the lungs of rats exposed to a candidate modified-risk tobacco product, the Tobacco Heating System 2.2 (THS2.2) in a 90-day OECD TG-413 inhalation study. Our aim was to assess the miRNA response to THS2.2 aerosol compared with the response to combustible cigarettes (CC) smoke from the reference cigarette 3R4F. CC smoke exposure, but not THS2.2 aerosol exposure, caused global miRNA downregulation, which may be explained by the interference of CC smoke constituents with the miRNA processing machinery. Upregulation of specific miRNA species, such as miR-146a/b and miR-182, indicated that they are causal elements in the inflammatory response in CC-exposed lungs, but they were reduced after THS2.2 aerosol exposure. Transforming transcriptomic data into protein activity based on corresponding downstream gene expression, we identified potential mechanisms for miR-146a/b and miR-182 that were activated by CC smoke but not by THS2.2 aerosol and possibly involved in the regulation of those miRNAs. The inclusion of miRNA profiling in systems toxicology approaches increases the mechanistic understanding of the complex exposure responses.