Introduction
Diabetes accounts for a substantial health and economic burden in the UK, with over 4.7 million people living with the disease and over 12.3 million people at an increased risk of developing the disease in 2018 [
1]. Diabetes-related healthcare expenditure (expressed in pounds sterling [GBP]) was estimated to be over GBP 10 billion in 2018, accounting for 10% of the entire National Health Service (NHS) budget [
1]. An estimated 80% of diabetes-related expenditure in the UK is associated with the treatment of long-term complications, with a more than twofold increase in risk of myocardial infarction, heart failure and stroke in people with type 2 diabetes versus those without the disease [
1]. Interventions that are cost-effective, offering clinical benefits while providing value for money, are becoming vital as healthcare payers’ budgets come under increasing pressure.
Improvements in glycated haemoglobin (HbA1c) and blood pressure have long been associated with reductions in long-term diabetes-related complications, as demonstrated in the landmark United Kingdom Prospective Diabetes Study (UKPDS), and more recent evidence has suggested that reductions in other parameters, such as body weight, can provide further benefits [
2‐
5]. Clinical guidelines published by the National Institute for Health and Care Excellence (NICE) in the UK recommend an individualised approach for the treatment of each patient that incorporates personal preferences and comorbidities [
6]. Moreover, the most recent guidelines released by the European Association for the Study of Diabetes (EASD) and the American Diabetes Association (ADA) recommend a more holistic approach to diabetes treatment, rather than a sole focus on glycaemic control [
7]. In particular, updated recommendations for people with type 2 diabetes with established cardiovascular disease or for those who are overweight or obese or have a high risk of hypoglycaemia now consider the effects of therapies on cardiovascular disease, body weight and hypoglycaemia risk alongside reductions in HbA1c [
7].
Glucagon-like peptide-1 (GLP-1) receptor agonists represent a highly efficacious class of interventions for the treatment of type 2 diabetes, with the injectable GLP-1 analogue once-weekly semaglutide shown to be both efficacious and cost-effective versus a variety of therapies [
8‐
11]. However, until recently, GLP-1 receptor agonists have only been available in injectable formulations, which may have been a barrier to patient use compared with other modern treatment options such as sodium-glucose cotransporter-2 (SGLT2) inhibitors and dipeptidyl peptidase-4 (DPP-4) inhibitors, which are administered orally. Indeed, in the UK, injectable GLP-1 receptor agonists are only recommended as an intensification step for patients with inadequate glycaemic control following a triple therapy combination of metformin plus a DPP-4 inhibitor with a sulfonylurea, pioglitazone or an SGLT2 inhibitor, for whom insulin therapy would have significant occupational implications or weight loss would benefit other obesity-related comorbidities [
6]. Given the efficacy benefits GLP-1 receptor agonists appear to offer, earlier intensification to such medications could overcome the documented and substantial therapeutic inertia in people with type 2 diabetes [
8‐
12].
Oral semaglutide is a novel formulation of the GLP-1 analogue semaglutide developed for once-daily oral administration, in which the absorption enhancer sodium
N-(8-[2-hydroxybenzoyl]amino) caprylate facilitates absorption across the gastric mucosa. The efficacy and safety of oral semaglutide has been assessed in the PIONEER clinical trial programme, with once-daily oral semaglutide 14 mg compared with once-daily SGLT2 inhibitor empagliflozin 25 mg in PIONEER 2, with once-daily DPP-4 inhibitor sitagliptin 100 mg in PIONEER 3 and with once-daily injectable GLP-1 receptor agonist liraglutide 1.8 mg in PIONEER 4 [
13‐
15].
The aim of the present analysis was to assess the long-term cost-effectiveness of oral semaglutide 14 mg versus empagliflozin 25 mg, sitagliptin 100 mg and liraglutide 1.8 mg in the UK setting, based on the results of the PIONEER 2, 3 and 4 studies, respectively.
Methods
Modelling Approach
Long-term projections of clinical and cost outcomes were performed from a healthcare payer perspective using the IQVIA CORE Diabetes Model (version 9.0), a proprietary, validated, internet-based, interactive computer model developed to determine the long-term health outcomes and economic consequences of implementing interventions in the treatment of type 1 and type 2 diabetes mellitus (accessible at
http://www.core-diabetes.com) [
16,
17]. The architecture, assumptions, features and capabilities of the model have been previously published [
16]. Validation studies of the model have been published both in 2004 and more recently in 2014 [
17,
18].
Model outputs include time to onset and cumulative incidence of complications, life expectancy, quality-adjusted life expectancy (QALE; expressed in quality-adjusted life years [QALYs]), direct costs and, where required, incremental cost-effectiveness ratios (ICERs), which describe the cost per additional unit of effectiveness gained for the intervention versus the comparator. In comparisons where an intervention is associated with cost savings while providing greater clinical benefits, no calculation of an ICER is required and the intervention is considered to be dominant versus the comparator.
Analyses were performed over patient lifetimes (up to 50 years), as recommended in the guidelines for the cost-effectiveness assessment of interventions for type 2 diabetes, to ensure all relevant diabetes-related complications and their impact on clinical and cost outcomes were captured [
19]. The UKPDS 68 risk equations were applied to predict model outcomes. Background mortality was captured based on UK-specific life tables published by the World Health Organisation (Electronic Supplementary Material [ESM] Table S1) [
20]. Health-state utilities and event disutilities were based on published sources (ESM Table S2) [
21‐
27].
This article is based on previously conducted studies and does not contain any studies with human participants or animals performed by any of the authors.
Clinical Data
Baseline cohort characteristics and treatment effects were sourced from the PIONEER 2, 3 and 4 trials for comparisons of oral semaglutide 14 mg with empagliflozin 25 mg, sitagliptin 100 mg and liraglutide 1.8 mg, respectively (ESM Table S3; Table
1). PIONEER 2 enrolled people with type 2 diabetes with HbA1c values between 7.0 and 10.5% (53–91 mmol/mol) who were receiving metformin; PIONEER 3 enrolled people with type 2 diabetes with HbA1c values between 7.0 and 10.5% who were receiving metformin with or without a sulfonylurea; and PIONEER 4 enrolled people with type 2 diabetes with HbA1c values between 7.0 and 9.5% (53–80 mmol/mol) who were receiving metformin with or without an SGLT2 inhibitor. The PIONEER trial programme used two estimands, namely the treatment policy estimand and the trial product estimand, to address two different efficacy questions. The treatment policy estimand reflected the intention-to-treat principle by including all study participants randomly assigned to each treatment, using data regardless of discontinuation of study medications and/or use of additional anti-diabetic medications during the trial [
28,
29]. In contrast, the trial product estimand assessed treatment effects under the assumption that patients received the study drug for the duration of the trial and did not receive any additional anti-diabetic medications, aiming to reflect the effects of the study medications without the confounding effects of rescue medication or any other changes in glucose-lowering medication [
28]. To match the annual cycle length of the model, and to avoid the confounding impact of additional anti-diabetic medications on clinical and cost outcomes, the analyses were performed using the 52-week data evaluated by the trial product estimand. The impact of using data evaluated by the treatment policy estimand was explored in a sensitivity analysis.
Table 1Treatment effects and adverse event rates sourced from the PIONEER 2, 3 and 4 trials that were applied in the analyses
Physiological parameters applied in the first year of the analysis, mean (SE) |
HbA1c (%) | − 1.30 (0.05)* | − 0.79 (0.05) | − 1.25 (0.05)* | − 0.52 (0.05) | − 1.19 (0.06)* | − 0.92 (0.06) |
Systolic blood pressure (mmHg) | − 4.85 (0.65) | − 4.34 (0.63) | − 3.13 (0.63)* | − 0.82 (0.61) | − 3.36 (0.75) | − 2.86 (0.74) |
Diastolic blood pressure (mmHg) | − 2.27 (0.45) | − 2.67 (0.44) | − 1.07 (0.39) | − 0.92 (0.38) | − 1.10 (0.45) | − 1.05 (0.44) |
Total cholesterol (mg/dL)a | − 5.08 (1.62)* | 4.74 (1.57) | − 3.66 (1.50)* | 1.02 (0.57) | − 5.47 (2.07) | − 5.36 (2.05) |
HDL cholesterol (mg/dL)a | 0.73 (0.35)* | 3.11 (0.34) | 0.54 (0.34) | 0.20 (0.35) | 1.17 (0.41) | 0.23 (0.41) |
BMI (kg/m2) | − 1.73 (0.10)* | − 1.37 (0.09) | − 1.36 (0.07)* | − 0.32 (0.07) | − 1.82 (0.11)* | − 1.11 (0.11) |
Hypoglycaemic event rates applied while patients received treatment |
Non-severe hypoglycaemic event rate (events per 100 patient-years)b | 2.25 | 1.90 | 12.12 | 11.99 | 0.71 | 3.16 |
Severe hypoglycaemic event rate (events per 100 patient-years)b | 0.25 | 0.24 | 0.24 | 0.90 | 0.00 | 0.00 |
Proportion of non-severe hypoglycaemic events that are nocturnalb | 0.11 | 0.13 | 0.14 | 0.13 | 0.00 | 0.11 |
Proportion of severe hypoglycaemic events that are nocturnalb | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
Treatment Switching and Long-Term Parameter Progression
Following application of the treatment effects in the first year of the analysis, HbA1c was modelled to follow the UKPDS progression equation, and patients were assumed to receive oral semaglutide or comparator treatment until HbA1c exceeded 7.5% (58 mmol/mol), which is the threshold for treatment intensification defined in the NICE guidelines [
6]. At this stage, treatment with oral semaglutide or the comparator was discontinued, and patients were assumed to intensify treatment to basal insulin, with a reduction in HbA1c based on an insulin-naïve population derived from the “Core” multivariate equations estimated by Willis et al. [
30]. HbA1c was subsequently modelled to follow the UKPDS progression equation for the remainder of patient lifetimes. This approach was chosen to mirror the HbA1c progression used by NICE for evaluating SGLT2 inhibitors as monotherapy in the UK and to reflect common clinical practice in which, due to the progressive nature of type 2 diabetes, glycaemic control cannot be maintained indefinitely by the addition of one medication [
7,
31]. Variations in the thresholds for treatment switching and further treatment intensification to basal–bolus insulin were explored in sensitivity analyses.
Body mass index (BMI) benefits were assumed to persist while patients received either oral semaglutide or comparator treatment, before reverting to baseline following intensification to basal insulin therapy. Therefore, no difference in BMI was seen between the patient arms following treatment intensification with basal insulin.
Changes in blood pressure and serum lipids were assumed to follow the natural progression algorithms built into the IQVIA CORE Diabetes Model in all arms, based on the UKPDS or Framingham data (as described by Palmer et al. [
16]), following application of the treatment effects in the first year of the analysis. Hypoglycaemia rates following treatment intensification were based on published data, with non-severe and severe hypoglycaemic events projected to increase to 4.08 and 0.10 events per patient per year, respectively [
32].
Cost Data
Costs were accounted from a UK healthcare payer perspective. Captured direct costs included pharmacy costs, costs associated with diabetes-related complications and patient management costs (ESM Tables S4, S5). The annual acquisition cost of oral semaglutide was assumed to be the same as that of once-weekly semaglutide, based on the similar level of pricing seen between the GLP-1 analogues in the US market. Costs of other included medications and consumables were based on published list prices (sourced in July 2019), while costs of diabetes-related complications were identified through a 2017 literature review and updated or inflated where necessary to the most recent costs available (2018 GBP) using published NHS diagnosis-related groups and the healthcare inflation index published by the Personal Social Services Research Unit [
33‐
42]. No self-monitoring of blood glucose (SMBG) testing costs were associated with oral semaglutide, empagliflozin, sitagliptin or liraglutide, as all these interventions are associated with low rates of hypoglycaemia and, consequently, little to no SMBG testing would be required. No needles were required for the administration of oral semaglutide, empagliflozin or sitagliptin as these medications are administered orally, but one needle per day was required for the administration of liraglutide. Following treatment intensification to basal insulin (assumed to be insulin Abasaglar
®, the most widely used biosimilar of insulin glargine in the UK), patients were assumed to require one SMBG test per day and to use one needle per day for the administration of basal insulin.
Sensitivity Analyses
The extrapolation of clinical results by modelling the long-term consequences is associated with uncertainty. Sensitivity analyses were therefore performed on key parameters in the modelling analysis to assess the robustness of the base case findings. Sensitivity analyses conducted for all comparisons included: applying only statistically significant differences between the treatment arms; shortening the time horizon of the analyses to 35, 20 and 10 years (for which it should be noted that some patients were still alive at the end of the modelling period and, therefore, not all costs and consequences were captured); applying discount rates of 0 and 6% in separate analyses; applying the upper and lower limits of the 95% confidence intervals for the estimated treatment differences in HbA1c and BMI in separate analyses; maintaining BMI treatment effects for patient lifetimes; altering the HbA1c threshold for treatment intensification to 7.0% (53 mmol/mol) and 8.0% (64 mmol/mol); applying a second treatment intensification step to basal–bolus insulin at an HbA1c threshold of 7.5% (58 mmol/mol); exploring the effect of applying alternative basal insulin costs (insulin neutral protamine Hagedorn [NPH], Semglee
® [Mylan, biosimilar of insulin glargine] and Lantus
® [insulin glargine]) following treatment intensification; increasing and decreasing the annual acquisition cost of oral semaglutide by 5% in separate analyses; application of the liraglutide 1.2 mg price in the liraglutide arm of PIONEER 4; increasing and decreasing the costs of complications by 10% in separate analyses; applying an alternative cost of stroke in the year of the event and in subsequent years, based on a publication by Patel et al. [
43]; applying the UKPDS 82 risk equations to predict model outcomes; application of alternative disutilities for increases in BMI (based on a publication by Lee et al. [
26]) and hypoglycaemic events (based on publications by Currie et al. [
44] and Lauridsen et al. [
45]); application of the 26-week clinical data; and application of data evaluated by the treatment policy estimand from the PIONEER 2, 3 and 4 clinical trials [
13‐
15].
Probabilistic sensitivity analyses (PSA) were also performed using a second-order Monte Carlo approach. Cohort characteristics, treatment effects and complication costs and utilities were sampled from distributions, with cohorts of 1000 patients run through the model 1000 times.
Discussion
Based on long-term projections of clinical and cost outcomes, oral semaglutide 14 mg offers a cost-effective treatment option versus other modern treatments for type 2 diabetes, including empagliflozin 25 mg, sitagliptin 100 mg and liraglutide 1.8 mg. The observed clinical benefits were the result of a reduced incidence and delayed time to onset of long-term diabetes-related complications with oral semaglutide. Diabetes-related complications were fewer with oral semaglutide 14 mg, which yielded cost savings that partially offset its higher treatment costs versus empagliflozin and sitagliptin. Oral semaglutide was associated with lower treatment costs versus liraglutide, with further cost savings achieved through a reduced incidence of diabetes-related complications. Oral semaglutide 14 mg was therefore associated with ICERs of GBP 11,006 and GBP 4930 per QALY gained versus empagliflozin 25 mg and sitagliptin 100 mg, respectively, and was considered to be cost effective based on a willingness-to-pay threshold of GBP 20,000 per QALY gained. With improved clinical outcomes and reduced costs, oral semaglutide 14 mg was considered to be dominant versus liraglutide 1.8 mg.
Oral semaglutide is the first GLP-1 receptor agonist available for oral administration. Offering patients the benefits of a GLP-1 receptor agonist in a once-daily tablet could overcome some of the obstacles that lead to therapeutic inertia, as evidence suggests that patient concerns over potential side effects of therapies, including hypoglycaemia and weight gain, as well as fear of injections, often lead to delayed intensification of treatment, despite poor glycaemic control [
12,
46‐
48]. The PIONEER clinical trial programme enrolled patients receiving differing background therapies, with PIONEER 2 enrolling patients with inadequate glycaemic control on metformin, PIONEER 3 enrolling patients with inadequate glycaemic control on metformin with or without a sulfonylurea, and PIONEER 4 enrolling patients with inadequate glycaemic control on metformin with or without an SGLT2 inhibitor [
13‐
15]. As shown in the present study, oral semaglutide represents a cost-effective treatment option in all of these patient populations. Moreover, while the lower 1.2 mg dose of liraglutide is commonly recommended in the UK for the majority of patients, the present study has demonstrated that oral semaglutide remains more effective and less costly versus the more efficacious 1.8 mg dose of liraglutide when the lower 1.2 mg price is applied.
The present analysis used a clinically-relevant approach for HbA1c progression and treatment intensification, which is in line with recent publications and cost-effectiveness assessments of GLP-1 receptor agonists and SGLT2 inhibitors [
10,
31]. This strategy is representative of clinical practice in a real-world population with type 2 diabetes, with patients contining treatments while they remain within their glycaemic target, intensification becoming necessary as the disease progresses and glycaemic control becoming increasingly challenging over the long term. Indeed, the latest EASD/ADA guidelines recommend that patients are evaluated every 3–6 months to ensure treatments are performing effectively, and clinical guidelines published by NICE in the UK recommend treatment intensification at a 7.5% (58 mmol/mol) HbA1c threshold [
6,
7]. The use of the multivariate equations published by Willis et al. [
30] to estimate changes in HbA1c on the initiation of basal insulin therapy also represents a key strength of the present analysis. These equations are informed by a variety of sources captured in a literature review, allowing the analyses to avoid the use of specific treatment effects designed to artificially improve model outcomes. Therefore, the present study offers a highly relevant approach to real-world practice, where glycaemic control cannot be maintained indefinitely with one medication. However, a potential limitation of this approach is the use of the UKPDS equations for HbA1c progression, as these are based on data from 20 years ago and as such may no longer be as applicable in modern clinical practice. Nonetheless, there are no readily available long-term type 2 diabetes studies equivalent in length to the UKPDS to test this.
When evaluating the clinical and cost outcomes associated with the interventions included in the present analysis, it is important to consider the impact of differential treatment switching occurring due to the 7.5% (58 mmol/mol) HbA1c threshold. In the long-term projections based on PIONEER 2, patients received empagliflozin 25 mg for 2 years and oral semaglutide 14 mg for 3 years, while in the projections based on PIONEER 3, patients received sitagliptin 100 mg for 1 year and oral semaglutide 14 mg for 3 years. This improved glycaemic control resulted in initial treatment costs being maintained for 1 additional year in the analyses based on PIONEER 2 and for 2 additional years in the analyses based on PIONEER 3. However, alternative HbA1c thresholds were tested, including adding a further treatment intensification step to basal–bolus insulin, and these analyses did not change the conclusion that oral semaglutide is cost-effective.
A limitation inherent in all long-term health economic analyses is the reliance on short-term clinical trial data to project outcomes over patient lifetimes. However, this is an essential tenet of all long-term diabetes modelling and arguably represents the best source of evidence for decision-making in the absence of long-term clinical trial data. The use of 52-week data from the PIONEER trials, matching the annual cycle length of the model, also represents a strength of the analysis. Moreover, the variety of sensitivity analyses performed with different treatment switching assumptions and time horizons did not change the conclusion that oral semaglutide is cost-effective.