Using albumin to improve the therapeutic properties of diabetes treatments

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.

Gut hormone-based pharmacology: novel formulations and future possibilities for metabolic disease therapy

Glucagon-like peptide-1 (GLP-1) receptor agonists are established pharmaceutical therapies for the treatment of type 2 diabetes and obesity. They mimic the action of GLP-1 to reduce glucose levels through stimulation of insulin secretion and inhibition of glucagon secretion. They also reduce body weight by inducing satiety through central actions. The GLP-1 receptor agonists used clinically are based on exendin-4 and native GLP-1 and are available as formulations for daily or weekly s.c. or oral administration. GLP-1 receptor agonism is also achieved by inhibitors of dipeptidyl peptidase-4 (DPP-4), which prevent the inactivation of GLP-1 and glucose-dependent insulinotropic polypeptide (GIP), thereby prolonging their raised levels after meal ingestion. Other developments in GLP-1 receptor agonism include the formation of small orally available agonists and compounds with the potential to pharmaceutically stimulate GLP-1 secretion from the gut. In addition, GLP-1/glucagon and GLP-1/GIP dual receptor agonists and GLP-1/GIP/glucagon triple receptor agonists have shown the potential to reduce blood glucose levels and body weight through their effects on islets and peripheral tissues, improving beta cell function and stimulating energy expenditure. This review summarises developments in gut hormone-based therapies and presents the future outlook for their use in type 2 diabetes and obesity.

Preclinical pharmacology of RA15127343: In vitro and in vivo activity of a novel ultralong-acting basal insulin

AIM

To report the in vitro and in vivo preclinical pharmacokinetic (PK) and pharmacodynamic (PD) properties of RA15127343, a novel ultralong-acting insulin analogue targeting once-weekly administration, in female Göttingen minipigs.

METHODS

In vitro binding and activation of human insulin receptor isoforms (IR-A/IR-B), glucose uptake in rat myocytes, as well as mitogenic activity of RA15127343 were evaluated. In vivo, the PK and PD activities of RA15127343 were assessed in female, normoglycaemic Göttingen minipigs. The half-life (t_1/2 ) and time to maximum plasma concentration (T_max ) of subcutaneously (SC) administered RA15127343 (10/30/45/60 nmol/kg) were estimated. In vivo blood glucose and endogenous plasma C-peptide concentrations after single SC administration (10/30/45/60 nmol/kg) or repeated dosing (15 nmol/kg) were analysed.

RESULTS

In comparison to human insulin, RA15127343 showed lower in vitro binding affinity (19.9/6.31 μM vs. 1.10/1.14 nM) and activation (2.054 μM/669.6 nM vs. 26.04/18.24 nM) of IR-A/IR-B, lower potency to activate glucose uptake (855.2 vs. 3.37 nM) and lower mitogenic activity (17.92 μM vs. 10.78 nM; proliferation in MCF7 cells). In vivo, the mean t_1/2 and T_max of RA15127343 after SC administration ranged from 48 to 59 and 30 to 39 hours, respectively. Blood glucose and plasma C-peptide concentrations were significantly lower with RA15127343 (single/repeated doses) versus vehicle.

CONCLUSIONS

RA15127343 showed an ultra-long t_1/2 with a slow onset of action. The preclinical pharmacological outcomes suggest RA15127343 could be a potential ultralong-acting insulin analogue with low risk of hypoglycaemia in humans.

Synthesis and Evaluation of the Insulin-Albumin Conjugate with Prolonged Glycemic Control

Engineering therapeutic proteins to improve their half-life so as to sustain physiologically relevant extended activity is the need of the hour in biopharmaceutical research. In this study, insulin and bovine serum albumin (BSA) were independently functionalized rationally and were later conjugated to prolong the half-life of insulin. The thiol functionalization of BSA with 2-imminothiolane in the ratio 1:20 yielded an average of 6-8 thiols/BSA, which then reacted with maleimide-functionalized insulin to form an insulin-albumin conjugate. The bioconjugate was purified by size exclusion chromatography, and the increase in size was confirmed by sodium dodecyl-sulfate polyacrylamide gel electrophoresis. Bioconjugation resulted in a multi-fold increase in the hydrodynamic volume of the insulin-albumin conjugate as measured in DLS when compared to BSA. The glucose uptake assay with 3LT3-L1 cell lines was performed, and the mean fluorescence intensity (MFI) of 16.16 observed for the insulin-albumin conjugate was comparable to insulin (19.42). The blood glucose reducing capacity of the insulin-albumin conjugate in streptozotocin induced diabetic male Wistar rats was well maintained up to 72 h when compared to native insulin. Further, a three-fold increase in plasma insulin concentration was observed in bioconjugate treated animals as against insulin treated animals after 24 h of treatment using ELISA. The histological analysis of different organs of the bioconjugate treated rats indicated that it was non-toxic. This study has paved a way for further detailed studies on similar bioconjugates to develop next-generation biotherapeutics for treating diabetes.

KRAS-enhanced macropinocytosis and reduced FcRn-mediated recycling sensitize pancreatic cancer to albumin-conjugated drugs

Pancreatic ductal adenocarcinoma (PDAC) is a dominantly (~95%) KRAS-mutant cancer that has extremely poor prognosis, in part this is due to its strong intrinsic resistance towards almost all therapeutic agents. PDAC relies heavily on KRAS-transformed metabolism, including enhanced macropinocytosis and catabolism of extracellular albumin, to maintain its proliferation and progression. However, it has yet to be validated that whether such transformed metabolism could be exploited for the drug delivery to open therapeutic windows of cytotoxic agents in KRAS-mutant PDAC. In this study, we attempt to answer this question by focusing on the impact of two critical regulators of albumin catabolism, KRAS and the neonatal Fc receptor (FcRn), on the sensitivity of PDAC to doxorubicin (DOX, a model cytotoxic agent) and albumin-conjugated doxorubicin (DOX-ALB). Using cell lines and cell-derived xenografts with different KRAS genotypes and FcRn levels, we demonstrated that KRAS-enhanced macropinocytosis and reduced FcRn expression sensitize PDAC to DOX-ALB but not free DOX. In both in vitro and in vivo comparsion, the DOX-ALB demonstrated ~10 times enlarged therapeutic window compared with free DOX, in PDAC with KRAS mutation and reduced FcRn level, two events appear to occur simultaneously in the investigated PDAC. In summary, we conclude that albumin conjugation is an exploitable drug delivery strategy that significantly opens the therapeutic windows of otherwise undevelopable anti-cancer agents for KRAS-mutant PDAC therapy, and creates a new landscape for clinical evaluation and future translation of such compounds.

Novel GLP-1/GLP-2 co-agonists display marked effects on gut volume and improves glycemic control in mice

AIM

Analogues of several gastrointestinal peptide hormones have been developed into effective medicines for treatment of diseases such as type 2 diabetes mellitus (T2DM), obesity and short bowel syndrome (SBS). In this study, we aimed to explore whether the combination of glucagon-like peptide-1 (GLP-1) and glucagon-like peptide-2 (GLP-2) into a potent co-agonist could provide additional benefits compared to existing monotherapies.

METHODS

A short-acting (GUB09-123) and a half-life extended (GUB09-145) GLP-1/GLP-2 co-agonist were generated using solid-phase peptide synthesis and tested for effects on food intake, body weight, glucose homeostasis, and gut proliferation in lean mice and in diabetic db/db mice.

RESULTS

Sub-chronic administration of GUB09-123 to lean mice significantly reduced food intake, improved glucose tolerance, and increased gut volume, superior to monotherapy with the GLP-2 analogue teduglutide. Chronic administration of GUB09-123 to diabetic mice significantly improved glycemic control and showed persistent effects on gastric emptying, superior to monotherapy with the GLP-1 analogue liraglutide. Due to the short-acting nature of the molecule, no effects on body weight were observed, whereas a marked and robust intestinotrophic effect on mainly the small intestine volume and surface area was obtained. In contrast to GUB09-123, sub-chronic administration of a half-life extended GUB09-145 to lean mice caused marked dose-dependent effects on body weight while maintaining its potent intestinotrophic effect.

CONCLUSION

Our data demonstrate that the GLP-1/GLP-2 co-agonists have effects on gut morphometry, showing a marked increase in intestinal volume and mucosal surface area. Furthermore, effects on glucose tolerance and long-term glycemic control are evident. Effects on body weight and gastric emptying are also observed depending on the pharmacokinetic properties of the molecule. We suggest that this novel co-agonistic approach could exemplify a novel concept for treatment of T2DM or SBS.

Cardiovascular Outcome Studies in Diabetes: How Do We Make Sense of These New Data?

Poorly controlled diabetes is characterized by premature cardiovascular mortality and morbidity. The mechanisms linking hyperglycemia with accelerated atherosclerotic disease have not been fully elucidated; however, are thought to be mediated through vascular inflammation, oxidative stress and endothelial dysfunction. The advent of incretin-based therapy, whether by increasing endogenous glucagon-like peptide (GLP)-1 and glucose-dependent inhibitory polypeptide by inhibition of their breakdown using di-peptidyl peptidase 4 inhibitors, or augmenting GLP-1 activity using either exendin-4-based drugs or synthetic GLP-1 analogs promised not just improvements in glycemic control, but improvements in endothelial function, lipid profiles and markers of vascular inflammation. As such, it was anticipated they would demonstrate cardiovascular benefit in those with diabetes, indeed early meta-analyses suggested cardiovascular events would be reduced. To date, however, this benefit has failed to materialize, indeed the cardiovascular outcome trials, whilst meeting their primary endpoint of cardiovascular safety, have failed to demonstrate any improvements in stroke or myocardial infarction. This review will explore the data and attempt to answer the question: what went wrong?

Cross-linked human serum albumin dimer has the potential for use as a plasma-retaining agent for the fatty acid-conjugated antidiabetic drugs

Objectives

The half-life of fatty acid-conjugated antidiabetic drugs are prolonged through binding to albumin, but this may not occur in diabetic patients with nephropathy complicated with hypoalbuminemia. We previously showed that human serum albumin (HSA) dimerized at the protein's Cys34 by 1,6-bis(maleimido)hexane has longer half-life than the monomer under high permeability conditions. The aim of this study was to investigate the superior ability of this HSA dimer as a plasma-retaining agent for fatty acid conjugated antidiabetic drugs.

Methods

The diabetic nephropathy rat model was prepared by administering a single injection of streptozotocin (STZ) intravenously, and the pharmacokinetic properties of HSA monomer and dimer were evaluated. Site-specific fluorescent probe displacement experiments were performed using warfarin and dansylsarcosine as site I and site II specific fluorescent probes, respectively.

Key findings

The half-life of the HSA dimer in STZ-induced diabetic nephropathy model rats was 1.5 times longer than the HSA monomer. The fluorescent probe displacement experiment results for HSA monomer and dimer were similar, where fatty acid-conjugated antidiabetic drugs displaced dansylsarcosine but not warfarin in a concentration-dependent manner.

Conclusions

The HSA dimer shows potential for use as a plasma-retaining agent for antidiabetic drugs due to its favourable pharmacokinetic properties.

Insulin degludec as an ultralong-acting basal insulin once a day: a systematic review

BACKGROUND

Insulin degludec (IDeg) is a neutral, ultralong-acting new generation basal insulin analog developed by NovoNordisk currently in Phase III clinical development. IDeg offers a duration of action of more than 42 hours in adults, much longer than current basal insulin formulations.

OBJECTIVE

The aim of this review is to assess the efficacy and safety data of IDeg in the treatment of type 1 and type 2 diabetes mellitus.

METHODS

Relevant English language articles from 2010 to 2012 were identified through MEDLINE, PubMed, EMBASE, Scopus, BIOSIS, and Google Scholar. Online conference proceedings of the 71st ADA Scientific Sessions and the 47th EASD Annual Meeting were reviewed. Studies were compared in terms of their study designs, primary and secondary efficacy parameters, and tolerability data.

RESULTS

There are a total of nine published trials investigating the clinical efficacy and safety of IDeg in over 3000 subjects with type 1 and 2 diabetes. Only three trials were published in full. All were open-label, randomized multicenter trials with durations of 16 to 52 weeks. IDeg and coformulations of IDeg with insulin aspart (IAsp) were compared to insulin glargine (IGlar), detemir, and biphasic IAsp 30 (BIAsp 30).

CONCLUSION

Based upon the available evidence, there appear to be no reported differences between IDeg and IGlar, detemir, or BIAsp 30 in the reduction of the primary efficacy end-points of HbA(1c) and mean fasting plasma glucose (FPG) concentrations. Only flexible dosing of IDeg provided a significant reduction in FPG compared to IGlar. IDeg demonstrated a significant reduction in nocturnal hypoglycemia in type 1 diabetes. In type 2 diabetes, IDeg reduced the incidence of hypoglycemia by 18% and 58% compared to IGlar and BIAsp 30, respectively.