Quantitative systems pharmacology analysis of drug combination and scaling to humans: the interaction between noradrenaline and vasopressin in vasoconstriction.

BACKGROUND AND PURPOSE: Development of combination therapies has received significant interest in recent years. Previously, a two-receptor one-transducer (2R-1T) model was proposed to characterize drug interactions with two receptors that lead to the same phenotypic response through a common transducer pathway. We applied, for the first time, the 2R-1T model to characterize the interaction of noradrenaline and arginine-vasopressin on vasoconstriction and performed inter-species scaling to humans using this mechanism-based model. EXPERIMENTAL APPROACH: Contractile data were obtained from in vitro rat small mesenteric arteries after exposure to single or combined challenges of noradrenaline and arginine-vasopressin with or without pretreatment with the irreversible α-adrenoceptor antagonist, phenoxybenzamine. Data were analysed using the 2R-1T model to characterize the observed exposure-response relationships and drug-drug interaction. The model was then scaled to humans by accounting for differences in receptor density. KEY RESULTS: With receptor affinities set to published values, the 2R-1T model satisfactorily characterized the interaction between noradrenaline and arginine-vasopressin in rat small mesenteric arteries (relative standard error ≤20%), as well as the effect of phenoxybenzamine. Furthermore, after scaling the model to human vascular tissue, the model also adequately predicted the interaction between both agents on human renal arteries. CONCLUSIONS AND IMPLICATIONS: The 2R-1T model can be of relevance to quantitatively characterize the interaction between two drugs that interact via different receptors and a common transducer pathway. Its mechanistic properties are valuable for scaling the model across species. This approach is therefore of significant value to rationally optimize novel combination treatments.

Abatacept or infliximab for patients with rheumatoid arthritis and inadequate response to methotrexate: an Italian trial-based and real-life cost-consequence analysis.

OBJECTIVES: In the 1-year, double-blind, placebo-controlled ATTEST trial, efficacy of abatacept or infliximab versus placebo was reported in patients with rheumatoid arthritis (RA) and an inadequate response to methotrexate (MTX). The current study estimated trial-based and real-life costs of abatacept and infliximab for achieving pre-defined remission or low disease activity state (LDAS). METHODS: Quantity of drug, serious adverse event (SAE) rates and time (months) in remission or LDAS were taken from ATTEST for the trial-based calculation to derive a cost per remitting/LDAS patient and a cost per patient-month in remission/LDAS. Trial-based and real-life scenarios were performed. RESULTS: The annual trial-based costs per remitting/LDAS patient were €70.238/€37.208 for abatacept and €85.565/€46.602 for infliximab. In the first 6 months of the ATTEST trial, costs per patient-month in remission/LDAS were higher for abatacept (€11.024 and €6.018, respectively), relative to infliximab (€8.347 and €4.174, respectively). Over the full 12-month trial period cost per month in remission/LDAS estimates were only slightly in favour of infliximab (€6.959/€3.625) relative to abatacept (€7.297/€3.909). Assuming extension of treatment under real life conditions the cost per month in remission/LDAS turned substantially in favour of abatacept (€5.321/€2.819), as compared to infliximab (€7.189/€3.916). The higher initiation cost for abatacept to achieve remission/LDAS would be offset after a total 14.6 and 16.1 months of treatment, respectively, if treatment extended beyond 6 months under real-life conditions. These results proved to be robust when it was assumed that the (i) sharing of vials across patients completely averted infliximab wastage, (ii) AE risks were similar and (iii) onset of response was slower for abatacept. CONCLUSIONS: Our findings suggest a lower cost-consequence for abatacept during real-life treatment.

Economic evaluation of posaconazole versus fluconazole prophylaxis in patients with graft-versus-host disease (GVHD) in the Netherlands.

The objective of this study was to evaluate the cost-effectiveness of posaconazole versus fluconazole for the prevention of invasive fungal infections (IFI) in graft-versus-host disease (GVHD) patients in the Netherlands. A decision analytic model was developed based on a double-blind randomized trial that compared posaconazole with fluconazole antifungal prophylaxis in recipients of allogeneic HSCT with GVHD who were receiving immunosuppressive therapy (Ullmann et al., N Engl J Med 356:335-347, 2007). Clinical events were modeled with chance nodes reflecting probabilities of IFIs, IFI-related death, and death from other causes. Data on life expectancy, quality-of-life, medical resource consumption, and costs were obtained from the literature. The total cost with posaconazole amounted to 9,428 (95% uncertainty interval 7,743-11,388), which is 4,566 (2,460-6,854) more than those with fluconazole. Posaconazole prophylaxis resulted in 0.17 (0.02-0.36) quality adjusted life year (QALY) gained compared to fluconazole prophylaxis, corresponding to an incremental cost effectiveness ratio (ICER) of 26,225 per QALY gained. A scenario analysis demonstrated that at an increased background IFI risk (from 9% to 15%) the ICER was 13,462 per QALY. Given the underlying data and assumptions, posaconazole prophylaxis is expected to be cost-effective relative to fluconazole in recipients of allogeneic HSCT developing GVHD in the Netherlands. The cost-effectiveness of posaconazole depends on the IFI risk, which can vary by hospital.

Economic evaluation of posaconazole vs. standard azole prophylaxis in high risk neutropenic patients in the Netherlands.

BACKGROUND: Acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) patients experience prolonged neutropenia after treatment with intensive chemotherapy, leading to a high risk of invasive fungal infections (IFI). The present study evaluates the cost effectiveness of posaconazole vs. standard azoles for the prevention of IFIs in neutropenic patients in the Netherlands. METHODS: A decision-tree model was developed using data from a randomized trial that compared posaconazole and standard azole (fluconazole or itraconazole) prophylaxis in neutropenic patients receiving remission-induction chemotherapy for AML/MDS (Cornely et al., N Engl J Med 2007;356:348-359). Following initiation of prophylaxis, clinical events are modeled with chance nodes reflecting probabilities of IFIs, IFI-related death, and death from other causes. Patients surviving the prophylaxis are assumed to have a life expectancy according to the underlying condition. This allows translation of the trial outcomes to a lifetime horizon. Data on life expectancy, quality of life, medical resource consumption and costs were obtained from the literature. Model outcomes include cost per life year (LY) gained and cost per quality adjusted life year (QALY) gained. RESULTS: The total cost (treatment of breakthrough IFI + prophylaxis) for posaconazole amounted to 4412 euros (95% uncertainty interval 3403 euros - 5666 euros), which is -183 euros (-1985 euros to 1564 euros) less than costs with standard azoles. Posaconazole prophylaxis resulted in 0.08 (0.02-0.15) QALYs gained in comparison with prophylaxis with standard azoles. Results from a probabilistic sensitivity analysis indicate that there is a 90% probability that the cost per QALY gained with posaconazole is below 20,000 euros. Additional scenario analyzes with different assumptions confirmed these findings. CONCLUSION: Given the underlying data and assumptions, the economic evaluation demonstrated that posaconazole prophylaxis is expected to be cost-effective compared with fluconazole/itraconazole in neutropenic AML/MDS patients after intensive chemotherapy.

Economic evaluation of caspofungin versus liposomal amphotericin B for empiric antifungal treatment in patients with neutropenic fever in Italy.

OBJECTIVE: To evaluate the cost-effectiveness of caspofungin versus liposomal amphotericin B as empiric antifungal treatment in patients with neutropenic fever in Italy. METHODS: The cost-effectiveness of caspofungin versus liposomal amphotericin B was evaluated using a decision-tree model. Patients were stratified by presence or absence of baseline infection. Model outcomes included success in terms of resolution of fever, resolution of baseline infection, absence of breakthrough infection, survival, and quality-adjusted life years (QALYs) saved. Discontinuation because of nephrotoxicity or other adverse events were included in the model. Efficacy and safety data were based on a randomized, double-blind, multinational trial of caspofungin compared to liposomal amphotericin B (Walsh 2004). Information on life expectancy, quality of life, medical resource consumption, and costs was obtained from the literature. RESULTS: The caspofungin estimated total treatment cost amounted to 8351 euros (95% uncertainty interval 7801 euros-8903 euros), which is 3470 euros (2575 euros-4382 euros) less than with liposomal amphotericin B. Treatment with caspofungin resulted in 0.25 (-0.11; 0.59) QALYs saved in comparison to treatment with liposomal amphotericin B. Probabilistic sensitivity analysis demonstrated a 93% probability that caspofungin was economically dominant, i.e., cost and QALY saving, and a probability of more than 99% that the costs per QALY saved were below 20,000 euros, a commonly accepted threshold for cost-effectiveness. Additional analyses with alternative doses of liposomal amphotericin B confirmed these findings. CONCLUSION: Given the underlying assumptions, our economic evaluation demonstrated that caspofungin is cost-effective compared to liposomal amphotericin B in empiric antifungal treatment of patients with neutropenic fever in Italy.