Albiglutide: A once-weekly glucagon-like peptide-1 receptor agonist for type 2 diabetes mellitus

Engineering a "three-in-one" hirudin prodrug to reduce bleeding risk: A proof-of-concept study

An ideal anticoagulant should have at least three properties including targeted delivery to the thrombosis site, local activation or releasing to centralize the anti-thrombosis effects and thus reduce the bleeding risks, and long persistence in circulation to avoid repeated administration. In the present study, we sought to test a "three-in-one" strategy to design new protein anticoagulants. Based on these criteria, we constructed two hirudin prodrugs, R824-HV-ABD and ABD-HV-R824. The R824 peptide can bind phosphatidylserine on the surface of the procoagulant platelets and thus guide the prodrug to the thrombosis sites; albumin-binding domain (ABDs) can bind the prodrug to albumin, and thereby increase its persistence in circulation; the hirudin (HV) core in the prodrug is flanked by factor Xa recognition sites, thus factor Xa at the thrombosis site can cleave the fusion proteins and release the activated hirudin locally. Hirudin prodrugs were able to bind with procoagulant platelets and human serum albumin in vitro with high affinity, targeted concentrated and prevented the formation of occlusive thrombi in rat carotid artery injury model. Their effective time was significantly extended compared to native hirudin, and R824-HV-ABD showed a significantly improved half-life of about 24 h in rats. The bleeding time of prodrug-treated mice was much shorter than that of hirudin-treated mice. The results from the proof-of-concept studies, for the first time, demonstrate that "three-in-one" prodrug strategy may be a good solution for protein or peptide anticoagulants to reduce their bleeding risks.

Improving long circulation and procoagulant platelet targeting by engineering of hirudin prodrug

To reduce systemic bleeding risks during anticoagulant treatment, a new concept named "precise anticoagulation" was proposed to localize the effects of anticoagulants via the targeted delivery of prodrugs to the coagulation site. In this study, the fusion protein Annexin V-hirudin 3-ABD (hAvHA) was constructed to achieve the prolonged circulation and targeted delivery of hirudin to coagulation sites. hAvHA was inactive as a prodrug, and it could bind to albumin during circulation. The drug was quickly activated via factor Xa-mediated cleavage once coagulation occurred, and hirudin was efficiently released to exert antithrombin activity in vitro. The hAvHA protein could be activated in mouse blood and exert significant anticoagulation effects. The results of FITC labeling illustrated that hAvHA bound to procoagulant platelets, suggesting the Annexin V modification permits targeted delivery to sites of thrombosis. hAvHA bound to albumin in vitro with an equilibrium dissociation constant of 8 pM, suggesting the ABD modification permitted prolonged circulation in vivo. Moreover, the bleeding time was much shorter in hAvHA-treated mice than in hirudin-treated mice. Therefore, our results suggested that that hAvHA is a potential and promising anticoagulant in vivo.

Recent Advances in Half-life Extension Strategies for Therapeutic Peptides and Proteins

Peptides and proteins are two classes of molecules with attractive possibilities for therapeutic applications. However, the bottleneck for the therapeutic application of many peptides and proteins is their short halflives in vivo, typically just a few minutes to hours. Half-life extension strategies have been extensively studied and many of them have been proven to be effective in the generation of long-acting therapeutics with improved pharmacokinetic and pharmacodynamic properties. In this review, we summarize the recent advances in half-life extension strategies, illustrate their potential applications and give some examples, highlighting the strategies that have been used in approved drugs and for drugs in clinical trials. Meanwhile, several novel strategies that are still in the process of discovery or at a preclinical stage are also introduced. In these strategies, the two most frequently used half-life extension methods are the reduction in the rate of renal clearance or the exploitation of the recycling mechanism of FcRn by binding to the albumin or IgG-Fc. Here, we discuss half-life extension strategies of recombinant therapeutic protein via genetic fusion, rather than chemical conjugation such as PEGylation. With the rapid development of genetic engineering and protein engineering, novel strategies for half-life extension have been emerged consistently. Some of these will be evaluated in clinical trials and may become viable alternatives to current strategies for making next-generation biodrugs.

C-terminal site-specific PEGylated Exendin-4 analog: A long-acting glucagon like Peptide-1 receptor agonist, on glycemic control and beta cell function in diabetic db/db mice

PEG modification is a common clinical strategy for prolonging the half-life of therapeutic proteins or polypeptides. In a previous work, we have successfully synthesized PEG-modified Exendin-4 (PE) by conjugating a 20 kDa PEG to the C-terminal of Exendin-4. Then, we introduced an integrative characterization for PE to evaluate its hypoglycemic activity and pharmacokinetic properties. The normoglycemic efficacies and therapeutic activity of PE were investigated in db/db mice. The hypoglycemic time after single administration of PE on db/db mice was prolonged from 8.4 h to 54.9 h. In multiple treatment with PE, the fasting blood glucose in various PE dosages (50, 150, and 250 nmol/kg) were remarkably reduced, and the glycosylated hemoglobin level was decreased to 2.0%. When the in vivo single- and multiple-dose pharmacokinetics of PE were examined in Sprague-Dawley rats, the half-life was prolonged to 31.7 h, and no accumulation effect was observed. Overall, this study provided a novel promising therapeutic approach to improving glucose-controlling ability and extending half-life without accumulation in vivo for long-acting treatment of type-2 diabetes.

Systematic Design of Trypsin Cleavage Site Mutated Exendin4-Cysteine 1, an Orally Bioavailable Glucagon-Like Peptide-1 Receptor Agonist

Exendin-4 is a strong therapeutic candidate for the treatment of metabolic syndrome. Related receptor agonist drugs have been on the market since 2005. However, technical limitations and the pain caused by subcutaneous injection have severely limited patient compliance. The goal of the study is to investigate a biologically active exendin-4 analog could be administered orally. Using intraperitoneal glucose tolerance tests, we discovered that exendin4-cysteine administered by oral gavage had a distinct hypoglycemic effect in C57BL/6J mice. Using Rosetta Design and Amber, we designed and screened a series of exendin4-cysteine analogs to identify those that retained biological activity while resisting trypsin digestion. Trypsin Cleavage Site Mutated Exendin4-cysteine 1 (TSME-1), an analog whose bioactivity was similar to exendin-4 and was almost completely resistant to trypsin, was screened out. In addition, TSME-1 significantly normalized the blood glucose levels and the availability of TSME-1 was significantly higher than that of exendin-4 and exendin4-cysteine. Collectively orally administered TSME-1, a trypsin-resistant exendin-4 analog obtained by the system, is a strong candidate for future treatments of type 2 diabetes.