Pharmacokinetic and pharmacodynamic properties of the novel basal insulin Fc (insulin efsitora alfa), an insulin fusion protein in development for once-weekly dosing for the treatment of patients with diabetes

Understanding the Pharmacokinetics and Glucodynamics of Once Weekly Basal Insulins to Inform Dosing Principles: An Introduction to Clinicians

OBJECTIVE

A new generation of basal insulin analogs enabling once-weekly administration is currently under development. Weekly basal insulins have the potential to overcome limitations exhibited by current daily basal insulins. The pharmacokinetic and glucodynamic characteristics differ significantly between weekly and daily basal insulins and will require paradigm shifts in how basal insulins are dosed.

METHODS

An overview of pharmacokinetic and glucodynamic principles of basal insulins is presented. Specifically, the pharmacokinetic and glucodynamic properties of daily basal insulins and how these differ for the new weekly basal insulins are discussed. Finally, models and simulations are used to describe the impact of weekly insulin properties on dosing.

RESULTS

Two approaches have been used to extend the half-lives of these insulins, creating fusion proteins with reduced clearance and reduced receptor-mediated degradation of the insulin. The resulting prolonged exposure-response profiles affect dosing and the impact of dosing errors. Specifically, the impact of loading doses, missed doses, and double doses, and the effect on glycemic variability of a once weekly basal insulin option are demonstrated using pharmacokinetic/glucodynamic models and simulations.

CONCLUSIONS

The transition from daily to weekly basal insulin dosing requires an understanding of the implications of the prolonged exposure-response profiles to effectively and confidently incorporate these weekly basal insulins into clinical practice. By reviewing the application of pharmacokinetic and glucodynamic principles to daily basal insulin analogs, the differences with weekly basal insulins, and the impact of these properties on dosing, this review intends to explain the principles behind weekly basal insulin dosing.

Diabetes Technology Meeting 2023

Diabetes Technology Society hosted its annual Diabetes Technology Meeting from November 1 to November 4, 2023. Meeting topics included digital health; metrics of glycemia; the integration of glucose and insulin data into the electronic health record; technologies for insulin pumps, blood glucose monitors, and continuous glucose monitors; diabetes drugs and analytes; skin physiology; regulation of diabetes devices and drugs; and data science, artificial intelligence, and machine learning. A live demonstration of a personalized carbohydrate dispenser for people with diabetes was presented.

Once-weekly insulins: a promising approach to reduce the treatment burden in people with diabetes

Despite the availability of new classes of glucose-lowering drugs that improve glycaemic levels and minimise long-term complications, at least 20-25% of people with type 2 diabetes require insulin therapy. Moreover, a substantial proportion of these individuals do not achieve adequate metabolic control following insulin initiation. This is due to several factors: therapeutic inertia, fear of hypoglycaemia and/or weight gain, poor communication, complexity of insulin titration, and the number of injections needed, with the associated reduced adherence to insulin therapy. Once-weekly insulins provide a unique opportunity to simplify basal insulin therapy and to allow good glycaemic control with a low risk of hypoglycaemia. Several approaches to developing a stable and effective once-weekly insulin have been proposed, but, to date, insulin icodec and basal insulin Fc (insulin efsitora alfa) are the only two formulations for which clinical studies have been reported. The results of Phase I and II studies emphasise both efficacy (in term of glucose levels) and potential risks and adverse events. Phase III studies involving insulin icodec are reassuring regarding the risk of hypoglycaemia compared with daily basal insulin analogues. Despite some concerns raised in ongoing clinical trials, the available data suggest that weekly insulins may also be an option for individuals with type 1 diabetes, especially when adherence is suboptimal. For the first time there is an opportunity to make an important breakthrough in basal insulin therapy, particularly in people with type 2 diabetes, and to improve not only the quality of life of people with diabetes, but also the practice of diabetologists.

Frequency and Severity of Hypoglycemia Under Conditions of Increased Hypoglycemic Risk with Insulin Efsitora Alfa Versus Insulin Glargine Treatment in Participants with Type 2 Diabetes

INTRODUCTION

Insulin efsitora alfa (efsitora) is a basal insulin with a flat pharmacokinetic profile and long half-life, enabling weekly dosing. These attributes may provide stable glucose levels. This exploratory phase 1 study aimed to assess the hypoglycemic risk during experimental conditions that mimic situations encountered in daily life.

METHODS

This was a single-site, open-label, two-period, fixed-sequence study in participants with type 2 diabetes (T2D) previously treated with basal insulin. The incidence, duration, and nadir glucose of hypoglycemia were assessed after treatment with efsitora versus insulin glargine (glargine) during three provocation conditions: 24-h prolonged fasting, prolonged fasting with exercise, and double dosing of study insulin.

RESULTS

The 54 enrolled adults (BMI 21.8-39.7 kg/m2, HbA1c 6.5-9.4%) achieved stable fasting glucose before undergoing provocation. Most hypoglycemic events were level 1 (≥ 54 to < 70 mg/dL) and resolved spontaneously or after oral glucose. The incidences of level 1 hypoglycemia for efsitora and glargine were not significantly different: for prolonged fasting, the incidences were 44.7 vs. 42.6% and the difference in proportion was 2.1% (95% CI: - 17.2, 21.4); for prolonged fasting with exercise, the corresponding values were 65.9 vs. 50.0% and 15.9% (- 3.0, 34.8); for double dosing, the corresponding values were 68.1 vs. 61.7% and 6.4% (- 12.8, 25.6). Level 2 hypoglycemia (< 54 mg/dL) was infrequent during both treatments and all provocations. No severe hypoglycemia was observed. Mean nadir glucose (range 62.8-66.3 mg/dL) and hypoglycemia duration (range 76.6-115.2 min) were also similar for the two treatments, depending on the provocation.

CONCLUSION

Overall, weekly efsitora did not increase the incidence, duration, or severity of hypoglycemia compared to daily glargine during provocation periods in patients with T2D.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT04957914.

Predicting human half-life for insulin analogs: An inter-drug approach

An inter-drug approach, applying pharmacokinetic information for insulin analogs in different animal species, rat, dog and pig, performed better compared to allometric scaling for human translation of intra-venous half-life and only required data from a single animal species for reliable predictions. Average fold error (AFE) between 1.2-1.7 were determined for all species and for multispecies allometric scaling AFE was 1.9. A slightly larger prediction error for human half-life was determined from in vitro human insulin receptor affinity data (AFE on 2.3-2.6). The requirements for the inter-drug approach were shown to be a span of at least 2 orders of magnitude in half-life for the included drugs and a shared clearance mechanism. The insulin analogs in this study were the five fatty acid protracted analogs: Insulin degludec, insulin icodec, insulin 320, insulin 338 and insulin 362, as well as the non-acylated analog insulin aspart.

Once-weekly insulin efsitora alfa: Design and rationale for the QWINT phase 3 clinical development programme

AIMS

Insulin efsitora alfa (efsitora) is a once-weekly basal insulin. This review describes the study design and rationale of the efsitora phase 3 Once Weekly (QW) Insulin Therapy (QWINT) clinical development programme, including the five trials, QWINT-1 through QWINT-5.

MATERIALS AND METHODS

The five trials included insulin-naïve adults (QWINT-1 and -2) with type 2 diabetes (T2D), adults with T2D previously treated with basal insulin (QWINT-3 and -4), and QWINT-5 in adults with type 1 diabetes. All five trials were designed as multicentre, randomized, controlled, open-label, treat-to-target studies to investigate the efficacy and safety of efsitora versus active once-daily basal insulin comparators (insulin glargine U100 or insulin degludec U100). The primary objective of each trial is to compare the change in HbA1c from baseline to week 26 or 52 between efsitora and the active comparator. The key secondary objectives include change in fasting glucose, insulin dose and continuous glucose monitoring variables, and patient-reported outcome questionnaires.

CONCLUSIONS

The QWINT development programme includes a racially and geographically diverse population to provide important information regarding the efficacy and safety of efsitora and its clinical management of people with diabetes.

Toward once-monthly insulin therapy via synergy in two pharmacokinetic protractors: Fc-conjugation and fatty acid acylation

Pharmacokinetic properties and duration of therapeutic action of a pharmaceutical agent can be significantly extended through the combination of two distinct strategies aimed at increasing plasma half-life: fatty acid acylation and Fc-conjugation. Using insulin as a case study, we demonstrate that a doubly protracted insulin analog produces a substantial prolongation of pharmacodynamic effect to lower blood glucose in STZ-treated mice when compared to the Fc-only counterparts. This enhancement is further corroborated by direct pharmacokinetic measurements in rat and dog models, demonstrating the potential for once-monthly insulin therapy. The results suggest that this approach might have broad application across a diverse spectrum of peptide- and protein-based therapeutics.

The Basis for Weekly Insulin Therapy: Evolving Evidence With Insulin Icodec and Insulin Efsitora Alfa

Basal insulin continues to be a vital part of therapy for many people with diabetes. First attempts to prolong the duration of insulin formulations were through the development of suspensions that required homogenization prior to injection. These insulins, which required once- or twice-daily injections, introduced wide variations in insulin exposure contributing to unpredictable effects on glycemia. Advances over the last 2 decades have resulted in long-acting, soluble basal insulin analogues with prolonged and less variable pharmacokinetic exposure, improving their efficacy and safety, notably by reducing nocturnal hypoglycemia. However, adherence and persistence with once-daily basal insulin treatment remains low for many reasons including hypoglycemia concerns and treatment burden. A soluble basal insulin with a longer and flatter exposure profile could reduce pharmacodynamic variability, potentially reducing hypoglycemia, have similar efficacy to once-daily basal insulins, simplify dosing regimens, and improve treatment adherence. Insulin icodec (Novo Nordisk) and insulin efsitora alfa (basal insulin Fc [BIF], Eli Lilly and Company) are 2 such insulins designed for once-weekly administration, which have the potential to provide a further advance in basal insulin replacement. Icodec and efsitora phase 2 clinical trials, as well as data from the phase 3 icodec program indicate that once-weekly insulins provide comparable glycemic control to once-daily analogues, with a similar risk of hypoglycemia. This manuscript details the technology used in the development of once-weekly basal insulins. It highlights the clinical rationale and potential benefits of these weekly insulins while also discussing the limitations and challenges these molecules could pose in clinical practice.

Pharmacokinetic and pharmacodynamic properties of once-weekly insulin icodec in individuals with type 1 diabetes

AIMS

To investigate the pharmacokinetic/pharmacodynamic properties of once-weekly insulin icodec in individuals with type 1 diabetes (T1D).

MATERIALS AND METHODS

In this randomized, open-label, two-period crossover trial, 66 individuals with T1D (age 18-64 years; glycated haemoglobin ≤75 mmol/mol [≤ 9%]) were to receive once-weekly icodec (8 weeks) and once-daily insulin glargine U100 (2 weeks) at individualized fixed equimolar total weekly doses established during up to 10 weeks' run-in with glargine U100 titrated to pre-breakfast plasma glucose (PG) of 4.4-7.2 mmol/L (80-130 mg/dL). Insulin aspart was used as bolus insulin. Blood sampling for icodec pharmacokinetics was performed from the first icodec dose until 35 days after the last dose. The glucose infusion rate at steady state was assessed in glucose clamps (target 6.7 mmol/L [120 mg/dL]) at 16-52 h and 138-168 h after the last icodec dose and 0-24 h after the last glargine U100 dose. Icodec pharmacodynamics during 1 week were predicted by pharmacokinetic-pharmacodynamic modelling. Hypoglycaemia was recorded during the treatment periods based on self-measured PG.

RESULTS

Icodec reached pharmacokinetic steady state on average within 2-3 weeks. At steady state, model-predicted daily proportions of glucose infusion rate during the 1-week dosing interval were 14.3%, 19.6%, 18.3%, 15.7%, 13.1%, 10.6% and 8.4%, respectively. Rates and duration of Level 2 hypoglycaemic episodes (PG <3.0 mmol/L [54 mg/dL]) were 32.8 versus 23.9 episodes per participant-year of exposure and 33 ± 25 versus 30 ± 18 min (mean ± SD) for icodec versus glargine U100.

CONCLUSIONS

The pharmacokinetic/pharmacodynamic properties of icodec suggest its potential to provide basal coverage in a basal-bolus insulin regimen in people with T1D.

What Is the Role of Basal Weekly Insulin in Clinical Practice? The State of the Art

Despite the advent of innovative therapies in the treatment of diabetes, ever-increasing awareness is still directed to the role of insulin since it has continued to be at the centre of diabetes therapy for decades, as a therapeutic integration of innovative agents in type 2 diabetes mellitus (T2DM), as the only replacement therapy in type 1 diabetes mellitus (T1DM) and also in gestational diabetes. In this context, the study of molecules such as weekly basal insulins, both for their technological and pharmacodynamic innovation and their manageability and undoubted benefits in compliance with drug therapy, can only be a turning point in diabetes and for all its phenotypes. This review aims to provide insight into the knowledge of basal weekly insulins and their use in type 1 and 2 diabetes mellitus by examining their safety, efficacy, manageability and increased therapeutic compliance.

Current barriers to initiating insulin therapy in individuals with type 2 diabetes

Insulin is an essential drug in the treatment of diabetes, often necessary for managing hyperglycemia in type 2 diabetes mellitus (T2DM). It should be considered in cases of severe hyperglycemia requiring hospitalization, after the failure of other treatments, in advanced chronic kidney disease, liver cirrhosis, post-transplant diabetes, or during pregnancy. Moreover, in specific patient subgroups, early initiation of insulin is crucial for hyperglycemia control and prevention of chronic complications. Clinical guidelines recommend initiating insulin when other treatments fail, although there are barriers that may delay its initiation. The timing of initiation depends on individual patient characteristics. Typically, insulinization starts by adding basal insulin to the patient's existing treatment and, if necessary, progresses by gradually introducing prandial insulin. Several barriers have been identified that hinder the initiation of insulin, including fear of hypoglycemia, lack of adherence, the need for glucose monitoring, the injection method of insulin administration, social rejection associated with the stigma of injections, weight gain, a sense of therapeutic failure at initiation, lack of experience among some healthcare professionals, and the delayed and reactive positioning of insulin in recent clinical guidelines. These barriers contribute, among other factors, to therapeutic inertia in initiating and intensifying insulin treatment and to patients' non-adherence. In this context, the development of once-weekly insulin formulations could improve initial acceptance, adherence, treatment satisfaction, and consequently, the quality of life for patients. Currently, two once-weekly basal insulins, insulin icodec and basal insulin BIF, which are in different stages of clinical development, may help. Their longer half-life translates to lower variability and reduced risk of hypoglycemia. This review addresses the need for insulin in T2DM, its positioning in clinical guidelines under specific circumstances, the current barriers to initiating and intensifying insulin treatment, and the potential role of once-weekly insulin formulations as a potential solution to facilitate timely initiation of insulinization, which would reduce therapeutic inertia and achieve better early control in people with T2DM.

Research Advances in Fusion Protein-Based Drugs for Diabetes Treatment

Diabetes mellitus (DM) is a chronic metabolic disease characterized by elevated blood glucose levels, resulting in multi-organ dysfunction and various complications. Fusion proteins can form multifunctional complexes by combining the target proteins with partner proteins. It has significant advantages in improving the performance of the target proteins, extending their biological half-life, and enhancing patient drug compliance. Fusion protein-based drugs have emerged as promising new drugs in diabetes therapeutics. However, there has not been a systematic review of fusion protein-based drugs for diabetes therapeutics. Hence, we conducted a comprehensive review of published literature on diabetic fusion protein-based drugs for diabetes, with a primary focus on immunoglobulin G (IgG) fragment crystallizable (Fc) region, albumin, and transferrin (TF). This review aims to provide a reference for the subsequent development and clinical application of fusion protein-based drugs in diabetes therapeutics.

Efficacy and safety of once-weekly basal insulin versus once-daily basal insulin in patients with type 2 diabetes: A systematic review and meta-analysis

BACKGROUND

Once-weekly insulin is expected to improve treatment compliance and durability and lead to better glycemic control. Several clinical trials on once-weekly insulin have recently been published. We conducted a systematic review and meta-analysis to investigate the efficacy and safety of once-weekly insulin versus once-daily insulin in type 2 diabetes (T2D).

METHODS

The following databases were searched for studies: PubMed, EMBASE, and Cochrane library (From January 1, 1946 to May 9, 2023). All randomized trials comparing weekly versus daily insulin in T2D were eligible for inclusion. Data analysis was performed using STATA 17.0 software (Stata Corporation, College Station, TX). The main outcomes and indexes included reduction in Hemoglobin A1c (HbA1c), fasting plasma glucose and bodyweight, proportion of patients achieving HbA1c < 7%, time-in-range 70 to 180 mg/dL and adverse events.

RESULTS

This systematic review and meta-analysis included 7 randomized controlled studies involving 2391 patients (1347 receiving 1-week insulin and 1044 receiving 1-day insulin). Once-weekly insulin was not inferior to once-daily insulin in HbA1c change [estimated treatment difference (ETD) = -0.05; 95% confidence intervals (CI): -0.14 to 0.04), HbA1c  < 7% (odds ratio = 1.14; 95% CI: 0.87-1.50), fasting plasma glucose (ETD = 0.09; 95% CI: -0.19 to 0.36) and body weight loss (ETD = 0.27; 95% CI: -0.36 to 0.91). In terms of time-in-range 70 to 180 mg/dL, weekly insulin was superior to daily insulin (MTD = 3.84; 95% CI: 1.55-6.08). Icodec was associated with higher incidence of all adverse events (odds ratio = 1.20; 95% CI: 1.03-1.48; P = .024), but did not result in high risk of serious and severe adverse events. Moreover, icodec and Basal Insulin Fc did not result in higher incidence of hypoglycemia compared with insulin daily.

CONCLUSION

Our meta-analysis found that insulin weekly was well tolerated and effective for glycemic control. Once-weekly insulin was not inferior to once-daily insulin in both efficacy and safety in T2D.

Pharmacokinetic and pharmacodynamic properties of once-weekly insulin icodec in individuals with type 2 diabetes

AIMS

To characterize the pharmacokinetic and pharmacodynamic properties of once-weekly insulin icodec in type 2 diabetes (T2D).

MATERIALS AND METHODS

In an open-label trial, 46 individuals with T2D (18-75 years; body mass index 18.0-38.0 kg/m2 ; glycated haemoglobin ≤75 mmol/mol [≤9%]; basal insulin-treated) received subcutaneous once-weekly icodec for ≥8 weeks at individualized doses, aiming at a pre-breakfast plasma glucose concentration of 4.4 to 7.0 mmol/L (80-126 mg/dL) on the last three mornings of each weekly dosing interval. Frequent blood sampling to assess total serum icodec concentration (ie, albumin-bound and unbound) occurred from first icodec dose until 35 days after last dose. Icodec trough concentrations following initiation of once-weekly dosing were predicted by pharmacokinetic modelling. During the final 3 weeks of icodec treatment, while at steady state, the icodec glucose-lowering effect was assessed in three glucose clamps (target 7.5 mmol/L [135 mg/dL]): 0 to 36, 40 to 64 and 144 to 168 h post-dose, thus covering the initial, middle and last part of the 1-week dosing interval. Glucose-lowering effect during a complete dosing interval was predicted by pharmacokinetic-pharmacodynamic modelling.

RESULTS

Model-predicted icodec steady state was attained after 3 to 4 weeks. At steady state, model-predicted daily proportions of glucose-lowering effect on days 1 to 7 of the 1-week dosing interval were 14.1%, 16.1%, 15.8%, 15.0%, 14.0%, 13.0% and 12.0%, respectively. Icodec duration of action was at least 1 week in all participants. Once-weekly icodec was overall safe and well tolerated in the current trial.

CONCLUSIONS

The pharmacokinetic and pharmacodynamic characteristics of icodec in individuals with T2D support its potential as a once-weekly basal insulin.

Efficacy and safety of once-weekly versus once-daily basal insulin analogues in the treatment of type 2 diabetes mellitus: A systematic review and meta-analysis

AIM

To summarize the evidence of recently published randomized controlled trials (RCTs) studying efficacy, in terms of glycaemic control, and safety of the newly developed once-weekly basal insulin analogues.

METHODS

A systematic literature search was conducted through Medline (via PubMed), Cochrane Library and Google Scholar until June 30, 2023. Double-independent study selection, data extraction and quality assessment were performed. Results were summarized with random-effects meta-analysis.

RESULTS

A total of 3962 patients with type 2 diabetes mellitus (T2DM) among nine RCTs were analysed. All RCTs had low risk of bias according to the Cochrane Collaboration risk-of-bias tool (RoB2). Once-weekly insulins demonstrated better efficacy in glycated haemoglobin (HbA1c) reduction (mean difference [MD] -0.13%, 95% confidence interval [CI] -0.23, -0.03; P = 0.08) and a significantly greater time in range compared with once-daily insulin analogues (MD 3.54%, 95% CI 1.56, 5.53; P = 0.005). Based on subgroup analyses, the reduction in HbA1c and the odds of achieving an end-of-treatment HbA1c <6.5% were significantly greater for icodec compared to the once-daily insulin (MD -0.18%, 95% CI -0.27, -0.09 [P < 0.001] and odds ratio [OR] 1.75, 95% CI 1.34, 2.29 [P < 0.001], respectively). Once-weekly insulins were associated with higher odds of level 1 hypoglycaemia during the 24-hour period (OR 1.3, 95% CI 1.04, 1.64; P = 0.02) but were safer in terms of level 2 or 3 nocturnal hypoglycaemic events (OR 0.74, 95% CI 0.56, 0.97; P = 0.03). No difference was observed regarding serious adverse events between the two groups.

CONCLUSION

The once-weekly basal insulin analogues seem to be at least equally efficient in glycaemic management and safe compared to once-daily injections in people with T2DM. Phase 4 RCTs are expected to shed further light on the effectiveness and safety of once-weekly insulin therapy over the long term.

A competitive ligand binding assay for detection of neutralizing antibodies against an insulin analog

Biotherapeutics have the potential to trigger undesired immune responses in the patients. For therapeutic proteins, immunogenicity is manifested as anti-drug antibodies (ADA). Because ADA could compromise pharmacokinetics, efficacy, and safety, regulatory agencies require immunogenicity assessment during clinical development. A tiered bioanalytical approach is recommended to monitor clinical immunogenicity, and neutralizing antibodies (NAb) are studied in Tier 4 if the molecule is immunogenic. Although cell-based assays, which reflect the pharmacological mechanism of action, are in some cases the preferred assay format for detecting NAbs, they are associated with operational complexity and sometimes suboptimal assay performance. Alternatively, non-cell-based assays have also been developed and implemented. In our current study, a competitive ligand binding assay (CLBA) was developed to detect NAbs for insulin efsitora alfa (efsitora, basal insulin Fc, LY3209590), a novel fusion protein being studied for the treatment of Type 1 diabetes and Type 2 diabetes. The CLBA demonstrated acceptable sensitivity, drug tolerance, precision, and robustness, and thus provides a suitable approach for detecting NAbs against efsitora.

Therapeutic Fusion Proteins

Therapeutic fusion proteins are a class of hybrid constructs that combine distinct biomolecules into a single platform with the additive effects of the components. The ability to fuse two unrelated proteins provides a means to localize mechanisms to better treat a range of diseases. Fusion proteins can be designed to impart diverse functions, including increasing half-life, providing targeting, and enabling sustained signaling. Of these, half-life extenders, which are fused to a therapeutic protein to increase exposure, are the most established group of fusion proteins, with many clinical successes. Rapid advances in antibody and antibody-derivative technology have enabled the fusion of targeting domains with therapeutic proteins. An emerging group of therapeutic fusion proteins has two separate active functions. Although most research for therapeutic fusion proteins focuses on cancer, prior successes provide a foundation for studies into other diseases as well. The exponential emergence of biopharmaceuticals gives precedence for increased research into therapeutic fusion proteins for a multitude of diseases.

Current Status of Weekly Insulin Analogs and Their Pharmacokinetic/Pharmacodynamic Evaluation by the Euglycemic Clamp Technique

Diabetes mellitus represents a significant global health threat characterized by hyperglycemia caused by inadequate insulin secretion and/or insulin resistance. Exogenous insulin supplements had been recognized as a crucial treatment for achieving successful glycemic control in patients with Type 1 and most patients with Type 2 diabetes. Over the past century, substantial progress has been made in the development of novel insulin formulations, including the super-fast-acting and long-acting basal insulin analogs, of which the latter is indispensable for the management of nocturnal fasting and intraprandial blood glucose within the normal physiological range. Recently, combining chemical and genetic engineering with drug optimization have resulted in a formidable evolution in ultra-long-acting weekly insulin. Here, the current state of once-weekly insulin analogs and the euglycemic clamp technique used in the early clinical development to elucidate the pharmacokinetics and pharmacodynamics of this type of novel weekly insulin analogs were systematically overviewed.