Public Health Impact of FDA's Request for Additional Safety Data on Cytisine for Tobacco Cessation.

Importance: No new tobacco cessation medication has been licensed in the US since 2006. Cytisine, a plant-based partial agonist of nicotinic acetylcholine receptors, has demonstrated safety and efficacy in several randomized clinical trials and is currently available in many countries. However, the drug is not commercially available in the US. A New Drug Application to license cytisine as a smoking cessation medication in the US is being prepared for review by the US Food and Drug Administration, whose request for additional safety data will delay submission of the application by approximately 1 year. Objective: To project the potential public health impact of cytisine, and delays in its availability, as a smoking cessation aid in the US. Design, Setting, and Participants: This mathematical model estimated life expectancy gains from smoking cessation for people aged 18 to 99 years in the US, reflecting the civilian, noninstitutionalized population. The model also accounted for cytisine uptake and effectiveness, as well as potential relapse among people who stop smoking. Exposure: Cytisine availability as a tobacco cessation treatment immediately or after 1 year. Main Outcomes and Measures: The main outcomes were the number of adults able to stop smoking and sustain long-term abstinence and aggregate life-years gained. Results: The base case includes an estimated 29.4 million US civilian noninstitutionalized adults who smoke cigarettes (age distribution, 18-24 years: 5.5%; 25-44 years: 37.3%; 45-64 years: 41.8%; ≥65 years: 15.5%). With a conservative assumption that 3.8% of these individuals would use cytisine in the first year of availability, immediate cytisine availability could lead 71 000 more people to quit smoking over 1 year and maintain long-term abstinence. This would produce more than 500 000 additional life-years compared to the status quo in which cytisine is unavailable and fewer people stop smoking. Each additional year of delay in the availability of cytisine might reduce population-level life expectancy by 10 000 years. The model results were most sensitive to changes in cytisine uptake and effectiveness. Conclusions and Relevance: Smoking cessation generates large gains in life expectancy. This mathematical model demonstrated that immediate cytisine availability, even if used successfully by only a small fraction of people who smoke, could produce major public health benefits. Given the need for new tobacco cessation pharmacotherapy options, the magnitude of cytisine's potential public health benefits, and the morbidity and mortality associated with delay in its availability, a timely review of cytisine for approval in the US is warranted.

Tobacco smoking, smoking cessation and life expectancy among people with HIV on antiretroviral therapy in South Africa: a simulation modelling study.

INTRODUCTION: As access to effective antiretroviral therapy (ART) has improved globally, tobacco-related illnesses, including cardiovascular disease, cancer and chronic respiratory conditions, account for a growing proportion of deaths among people with HIV (PWH). We estimated the impact of tobacco smoking and smoking cessation on life expectancy among PWH in South Africa. METHODS: In a microsimulation model, we simulated 18 cohorts of PWH with virologic suppression, each homogenous by sex, initial age (35y/45y/55y) and smoking status (current/former/never). Input parameters were from data sources published between 2008 and 2022. We used South African data to estimate age-stratified mortality hazard ratios: 1.2-2.3 (females)/1.1-1.9 (males) for people with current versus never smoking status; and 1.0-1.3 (females)/1.0-1.5 (males) for people with former versus never smoking status, depending on age at cessation. We assumed smoking status remains unchanged during the simulation; people who formerly smoked quit at model start. Simulated PWH face a monthly probability of disengagement from care and virologic non-suppression. In sensitivity analysis, we varied smoking-associated and HIV-associated mortality risks. Additionally, we estimated the total life-years gained if a proportion of all virologically suppressed PWH stopped smoking. RESULTS: Forty-five-year-old females/males with HIV with virologic suppression who smoke lose 5.3/3.7 life-years compared to PWH who never smoke. Smoking cessation at age 45y adds 3.4/2.4 life-years. Simulated PWH who continue smoking lose more life-years from smoking than from HIV (females, 5.3 vs. 3.0 life-years; males, 3.7 vs. 2.6 life-years). The impact of smoking and smoking cessation increase as smoking-associated mortality risks increase and HIV-associated mortality risks, including disengagement from care, decrease. Model results are most sensitive to the smoking-associated mortality hazard ratio; varying this parameter results in 1.0-5.1 life-years gained from cessation at age 45y. If 10-25% of virologically suppressed PWH aged 30-59y in South Africa stopped smoking now, 190,000-460,000 life-years would be gained. CONCLUSIONS: Among virologically suppressed PWH in South Africa, tobacco smoking decreases life expectancy more than HIV. Integrating tobacco cessation interventions into HIV care, as endorsed by the World Health Organization, could substantially improve life expectancy.

Virological, serological and clinical outcomes in chronic hepatitis B virus infection: development and validation of the HEPA-B simulation model.

OBJECTIVES: Detailed simulation models are needed to assess strategies for prevention and treatment of hepatitis B virus (HBV) infection, the world's leading cause of liver disease. We sought to develop and validate a simulation model of chronic HBV that incorporates virological, serological and clinical outcomes. METHODS: We developed a novel Monte Carlo simulation model (the HEPA-B Model) detailing the natural history of chronic HBV. We parameterised the model with epidemiological data from the Western Pacific and sub-Saharan Africa. We simulated the evolution of HBV DNA, 'e' antigen (HBeAg) and surface antigen (HBsAg). We projected incidence of HBeAg loss, HBsAg loss, cirrhosis, hepatocellular carcinoma (HCC) and death over 10-year and lifetime horizons. We stratified outcomes by five HBV DNA categories at the time of HBeAg loss, ranging from HBV DNA<300 copies/mL to >106 copies/mL. We tested goodness of fit using intraclass coefficients (ICC). RESULTS: Model-projected incidence of HBeAg loss was 5.18% per year over lifetime (ICC, 0.969 (95% CI: 0.728 to 0.990)). For people in HBeAg-negative phases of infection, model-projected HBsAg loss ranged from 0.78% to 3.34% per year depending on HBV DNA level (ICC, 0.889 (95% CI: 0.542 to 0.959)). Model-projected incidence of cirrhosis was 0.29-2.09% per year (ICC, 0.965 (95% CI: 0.942 to 0.979)) and HCC incidence was 0.06-1.65% per year (ICC, 0.977 (95% CI: 0.962 to 0.986)). Over a lifetime simulation of HBV disease, mortality rates were higher for people with older age, higher HBV DNA level and liver-related complications, consistent with observational studies. CONCLUSIONS: We simulated HBV DNA-stratified clinical outcomes with the novel HEPA-B Model and validated them to observational data. This model can be used to examine strategies of HBV prevention and management.

Variability in life expectancy among people with HIV in Brazil by gender and sexual orientation

Abstract Introduction In Brazil, though Antiretroviral Therapy (ART) is available to all, the benefits may not be experienced uniformly. We projected Life Expectancy (LE) for People Living with HIV (PLHIV) in care as currently observed and estimated the impact of guideline-concordant care. Methods Using a microsimulation model, we projected LE for a cohort of PLHIV and for four population groups: cisgender Men who have Sex with Men (MSM), cisgender Men who have Sex with Women (MSW), Cisgender Women (CGW), and Transgender Women (TGW). Cohort data from Evandro Chagas National Institute of Infectious Diseases/Oswaldo Cruz Foundation (INI/Fiocruz) informed model parameters. We modeled five scenarios: 1) Current care: ART initiation, adherence, and retention in care as currently observed, 2) Guideline-concordant care: immediate ART initiation, full adherence to treatment, and consistent retention in care, 3) Immediate ART initiation with observed adherence to treatment and retention in care, 4) Full adherence to treatment with observed timing of ART initiation and retention in care, and 5) Consistent retention in care with observed timing of ART initiation and adherence. Results With current care, LE from age 15 would be 45.9, 44.4, 54.2, and 42.3 years, for MSM, MSW, CGW, and TGW. With guideline-concordant care, LE would be 54.2, 54.4, 63.1, and 53.2 years, for MSM, MSW, CGW and TGW, with TGW experiencing the greatest potential increase in LE (10.9 years). When investigating the components of care separately, MSW and CGW would gain most LE with immediate ART initiation, whereas for MSM and TGW consistent retention in care would be most impactful. Conclusions In settings like INI/Fiocruz, MSW and CGW would benefit most from interventions focused on earlier diagnosis and linkage to care, whereas TGW and MSM would benefit from interventions to sustain engagement in care. Assessment of the HIV care continuum for specific populations should inform care priorities.