A province-by-province cost-effectiveness analysis and budget impact analysis of one-time birth cohort screening of hepatitis C virus (HCV) infection in Canada.

Managing chronic hepatitis C is challenging, as the majority of those infected are asymptomatic. Therefore, to ensure treatments are administered before the onset of severe complications, screening is important. In Canada, uncertainty regarding the cost-effectiveness and budget impact of screening has led to conflicting recommendations. The objective of this study is to estimate the cost-effectiveness and budget-impact of one-time HCV screening. A state-transition model was developed to evaluate the cost-effectiveness and budget-impact between a risk-based screening strategy (current-practice) and a one-time screening strategy on three different birth-cohorts. Cost and prevalence data were obtained from administrative data. Progression and utility data were based on recent systematic reviews. We used a provincial payer-perspective, life-time time-horizon and a 1.5% discount rate for the cost-effectiveness analysis, and used a 10-year time-horizon and no discounting for the budget-impact analysis. One-time screening strategy would cost more and provide more health benefits than the risk-based screening for all birth cohorts. For those born after 1964, the incremental-cost-effectiveness-ratio (ICER) per quality-adjusted-life-year (QALY) of screening versus current-practice varied from $27,422/QALY to $42,191/QALY across different provinces. One-time screening of the cohort would cost an additional $2 million to $236 million across different provinces. For those born 1945-1964, the ICER of screening versus current-practice varied from $35,217/QALY to $48,197/QALY across different provinces. For the cohort born before 1945, the ICER of screening versus current-practice was not cost-effective at a willingness-to-pay threshold of $50,000/QALY across all provinces. Our cost-effectiveness analysis suggests that a one-time HCV screening program for those born after 1945 is cost-effective. Considering the budget impact relative to other funded recommended health services and technologies, HCV screening could be considered affordable.

Model-Based Assessment of the Contribution of Monocytes and Macrophages to the Pharmacokinetics of Monoclonal Antibodies.

PURPOSE: We have hypothesized that a high concentration of circulating monocytes and macrophages may contribute to the fast weight-based clearance of monoclonal antibodies (mAbs) in young children. Exploring this hypothesis, this work uses modeling to clarify the role of monocytes and macrophages in the elimination of mAbs. METHODS: Leveraging pre-clinical data from mice, a minimal physiologically-based pharmacokinetic model was developed to characterize mAb uptake and FcRn-mediated recycling in circulating monocytes, macrophages, and endothelial cells. The model characterized IgG disposition in complex scenarios of site-specific FcRn deletion and variable endogenous IgG levels. Evaluation was performed for predicting IgG disposition with co-administration of high dose IVIG. A one-at-a-time sensitivity analysis quantified the role of relevant cellular parameters on IgG elimination in various scenarios. RESULTS: The plasma AUC of mAbs was highly sensitive to endothelial cell parameters, but had near-nil sensitivity to monocyte and macrophage parameters, even in scenarios with 90% loss of FcRn expression/activity. In mice with normal FcRn expression, simulations suggest that less than 2% of an IV dose is eliminated in macrophages, while endothelial cells are predicted to dominate mAb elimination. CONCLUSIONS: The model suggests that the role of monocytes and macrophages in IgG homeostasis includes extensive uptake and highly efficient FcRn-mediated protection, but not appreciable degradation when FcRn is present. Therefore, it is very unlikely that a high concentration of circulating monocytes can contribute to explaining the fast weight-based clearance of mAbs in very young children, even if FcRn expression/activity was 90% lower in children than in adults.

Assessment of Vehicle Volatility and Deposition Layer Thickness in Skin Penetration Models.

Systemic disposition of dermally applied chemicals is often formulation-dependent. Rapid evaporation of the vehicle can result in crystallization of active compounds, limiting their degree of skin penetration. In addition, the choice of vehicle can affect the permeant's degree of penetration into the stratum corneum. The aim of this study is to build a predictive, mechanistic, dermal absorption model that accounts for vehicle-specific effects on the kinetics of permeant transport into skin. An existing skin penetration model is extended to explicitly include the effect of vehicle volatility over time. Using in vitro measurements of skin penetration by chemicals applied in both a saline and an ethanol solvent, the model is optimized to learn two vehicle-specific quantities: the solvent evaporation rate and the extent of permeant deposition into the upper stratum corneum immediately following application. The dermal disposition estimates of the trained model are subsequently compared against those of the original model using further in vitro measurements. The trained model showed a 1.5-fold improvement and a 19-fold improvement in overall goodness of fit among compounds tested in saline and ethanol solvents, respectively. The proposed model structure can thus form a basis for in vitro to in vivo extrapolations of dermal disposition for skin formulations containing volatile components.

Cost-effectiveness analysis of sofosbuvir and velpatasvir in chronic hepatitis C patients with decompensated cirrhosis.

BACKGROUND: Current literature indicates that direct-acting antivirals (DAAs) are cost-effective to treat compensated cirrhotic patients with hepatitis C. Although already funded by public payers, it is unknown whether it is economical to reimburse DAAs within the more advanced decompensated cirrhosis population. METHODS: A state-transition model was developed to conduct a cost-utility analysis of sofosbuvir-velpatasvir (SOF/VEL) plus ribavirin regimen for 12 weeks. The evaluated cohort had a mean age of 58 years and Child-Turcotte-Pugh (CTP) class B cirrhosis with decompensated symptoms. A scenario analysis was performed on CTP C patients. We used a payer perspective, a lifetime time horizon and a 1.5% annual discount rate. RESULTS: While SOF/VEL plus ribavirin treatment for 12 weeks increased costs by $156 676, it provided an extra 4.00 quality-adjusted life years (QALYs) compared to best supportive care (no DAA therapy). With an incremental cost-effectiveness ratio of $39 169 per QALY, SOF/VEL plus ribavirin was determined to be cost-effective at a willingness to pay of $50 000 per QALY. SOF/VEL reduced liver-related deaths and reduced progression to CTP C cirrhosis by 20.4% and 21.9%, respectively. On the contrary, SOF/VEL regimen resulted in increases in liver transplants and hepatocellular carcinoma (HCC) by 54.0% and 42.5%, respectively. Similar results were found for CTP C patients. CONCLUSION: This analysis informs payers that SOF/VEL should continue to be reimbursed in decompensated hepatitis C patients. It also supports the recommendations by the American Association for the Study of Liver Diseases to continue screening for HCC in decompensated cirrhotic patients who have achieved sustained virologic response.

Population PBPK modelling of trastuzumab: a framework for quantifying and predicting inter-individual variability.

In this work we proposed a population physiologically-based pharmacokinetic (popPBPK) framework for quantifying and predicting inter-individual pharmacokinetic variability using the anti-HER2 monoclonal antibody (mAb) trastuzumab as an example. First, a PBPK model was developed to account for the possible mechanistic sources of variability. Within the model, five key factors that contribute to variability were identified and the nature of their contribution was quantified with local and global sensitivity analyses. The five key factors were the concentration of membrane-bound HER2 ([Formula: see text]), the convective flow rate of mAb through vascular pores ([Formula: see text]), the endocytic transport rate of mAb through vascular endothelium ([Formula: see text]), the degradation rate of mAb-HER2 complexes ([Formula: see text]) and the concentration of shed HER2 extracellular domain in circulation ([Formula: see text]). [Formula: see text] was the most important parameter governing trastuzumab distribution into tissues and primarily affected variability in the first 500 h post-administration. [Formula: see text] was the most significant contributor to variability in clearance. These findings were used together with population generation methods to accurately predict the observed variability in four experimental trials with trastuzumab. To explore anthropometric sources of variability, virtual populations were created to represent participants in the four experimental trials. Using populations with only their expected anthropometric diversity resulted in under-prediction of the observed inter-individual variability. Adapting the populations to include literature-based variability around the five key parameters enabled accurate predictions of the variability in the four trials. The successful application of this framework demonstrates the utility of popPBPK methods to understand the mechanistic underpinnings of pharmacokinetic variability.