In situ albumin-binding and esterase-specifically cleaved BRD4-degrading PROTAC for targeted cancer therapy

Proteolysis-targeting chimeras (PROTACs) have recently been of great interest in cancer therapy. However, the bioavailability of PROTACs is considerably restricted due to their high hydrophobicity, poor cell permeability, and thereby low tumor targeting ability. Herein, esterase-cleavable maleimide linker (ECMal)-conjugated bromodomain 4 (BRD4)-degrading PROTAC (ECMal-PROTAC) is newly synthesized to exploit plasma albumin as an 'innate drug carrier' that can be accumulated in targeted tumor tissues. The BRD4-degrading ECMal-PROTAC is spontaneously bound to albumins via the thiol-maleimide click chemistry and its esterase-specific cleavage of ECMal-PROTAC is characterized in physiological conditions. The albumin-bound ECMal-PROTACs (Alb-ECMal-PROTACs) have an average size of 6.99 ± 1.38 nm, which is similar to that of free albumins without denaturation or aggregation. When Alb-ECMal-PROTACs are treated to 4T1 tumor cells, they are actively endocytosed and reach their highest intracellular level within 12 h. Furthermore, the maleimide linkers of Alb-ECMal-PROTACs are cleaved by the esterase to release free BRD-4 degrading PROTACs and the cell-internalized PROTACs successfully catalyze the selective degradation of BRD4 proteins, resulting in BRD4 deficiency-related apoptosis. When ECMal-PROTACs are intravenously injected into tumor-bearing mice, they exhibit a 16.3-fold higher tumor accumulation than free BRD4-PROTAC, due to the shuttling effect of albumin for tumor targeting. Finally, ECMal-PROTACs show 5.3-fold enhanced antitumor efficacy compared to free BRD4-PROTAC, without provoking any severe systemic toxicity. The expression of Bcl-2 and c-Myc, the downstream oncogenic proteins of BRD4, are also effectively suppressed. In summary, the in situ albumin binding of ECMal-PROTAC is proven as a promising strategy that effectively modulates its pharmacokinetics and therapeutic performance with high applicability to other types of PROTACs.

Improving the circulation time and renal therapeutic potency of extracellular vesicles using an endogenous ligand binding strategy

Kidney diseases are a serious health issue worldwide, and novel therapeutics are urgently needed. Extracellular vesicles (EVs) have emerged as potent drug delivery systems (DDSs), but their therapeutic potential is limited by short circulation times and insufficient renal retention. Here, we report that endogenous ligand (albumin, ALB) binding is an efficient modification strategy to improve the therapeutic potency of EV-based DDSs for kidney diseases. Surface albumin-binding peptide (ABP)-displayed EVs (ABP-EVs) were produced by transfecting parent cells with the ABP-Lamp2b fusion plasmid. Compared with unmodified EVs (NC-EVs), ABP-EVs showed increased binding to ALB in vitro and elevated circulation time and multiple organ retention in vivo after systemic (iv) injection. Moreover, ABP-EVs had higher renal retention than NC-EVs in mice with acute kidney injury through a complex mechanism involving microvascular injury and megalin-mediated endocytosis. As a result, delivery of small molecule drugs (e.g., curcumin) or proteins (e.g., hepatocyte growth factor) by ABP-EVs had superior therapeutic (e.g., anti-apoptotic, antioxidant, anti-inflammatory) effects in vitro and in vivo. This study highlights that ABP-EVs are versatile DDSs for kidney diseases and provides insights into the new strategies of engineering EVs for drug delivery.

Albumin-binding tag derived Exendin-4 analogue for treating hyperglycemia and diabetic complications

Current study was conducted to design and screen a long-lasting Exendin-4 analog for treating type 2 diabetes via the novel strategy of albumin binding combined with thrombin enzymolysis. First, a series of fusion peptides, containing different albumin-binding tags, a determinate thrombin-cleavable linker and a native Exendin-4, were prepared via chemosynthesis for in vitro and in vivo characterization. Surface plasmon resonance assay, thrombin cleavage assay and plasma stability test were performed for screening the optimal HEX peptide with enhanced albumin-binding affinity, controlled-release as well as plasma stability. The in vivo anti-diabetic efficacies of the selected candidate were further assessed via both acute and chronic pharmacodynamic evaluation in diabetic model animals. HEX15 exhibited either the highest affinity for human serum albumin or the superior in vitro stability and controlled release of Exendin-4 among 21 HEX peptides. Glucose tolerance test and hypoglycemic duration assay both revealed the notably improved the glucose tolerance and prolonged normoglycemic duration, respectively, of diabetic mice after single treatment of HEX15. Furthermore, chronic dosing of HEX15 significantly ameliorated the manifestations of diabetes in the db/db mice, including body weight, food intake, glycometabolism as well as hyperlipemia. Interestingly, combination therapy of HEX15 and long non-coding RNA-ENST00000411554 notably accelerated the wound healing and improved foot ulcer symptoms in model rats with diabetic foot ulcers. In summary, based on the strategy of linking the heptapeptide tag and thrombin-based sustained release, a long-acting Exendin-4 analog, HEX15, holds potential to be developed as a drug for ameliorating T2D as well as diabetic complications.

Towards the development of a targeted albumin-binding radioligand: Synthesis, radiolabelling and preliminary in vivo studies

INTRODUCTION

The compound named 4-[10-(4-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)butanamido)decyl]-11-[10-(β,d-glucopyranos-1-yl)-1-oxodecyl]-1,4,8,11-tetraazacyclotetradecane-1,8-diacetic acid is a newly synthesised molecule capable of binding in vivo to albumin to form a bioconjugate. This compound was given the name, GluCAB(glucose-chelator-albumin-binder)-maleimide-1. Radiolabelled GluCAB-maleimide-1 and subsequent bioconjugate is proposed for prospective oncological applications and works on the theoretical dual-targeting principle of tumour localization through the "enhanced permeability and retention (EPR) effect" and glucose metabolism.

METHODS

The precursor, GluCAB-amine-2, and subsequent GluCAB-maleimide-1 was synthesised via sequential regioselective, distal N-functionalisation of a cyclam template with a tether containing a synthetically-derived β-glucoside followed by a second linker to incorporate a maleimide moiety for albumin-binding. GluCAB-amine-2 was radiolabelled with [64Cu]CuCl2 in 0.1 M NH4OAc (pH 3.5, 90 °C, 30 min), purified and converted post-labeling in 0.01 M PBS to [64Cu]Cu-GluCAB-maleimide-1. Serum stability and protein binding studies were completed according to described methods. Healthy BALB/c ice (three groups of n = 5) were injected intravenously with [64Cu]Cu-TETA, [64Cu]Cu-GluCAB-amine-2 or [64Cu]Cu-GluCAB-maleimide-1 and imaged using microPET/CT at 1, 2, 4, 8 and 24 h post-injection. Biodistribution of the compounds were determined ex vivo after 24 h using gamma counting.

RESULTS

GluCAB-maleimide-1 was synthesised in five consecutive steps with an overall yield of 11%. [64Cu]Cu-GluCAB-amine-2 (97% labelling efficiency) was converted to [64Cu]Cu-GluCAB-maleimide-1 (93% conversion; 90% radiochemical purity). Biodistribution analysis indicated that the control compounds were rapidly and almost completely excreted as compared to [64Cu]Cu-GluCAB-maleimide-1 that exhibited a prolonged biological half-life (6-8 h). Both, [64Cu]Cu-GluCAB-maleimide-1 and -amine-2 were excreted through the hepatobiliary system but a higher hepatic presence of the albumin-bound compound was noted. CONCLUSIONS, ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE: This initial evaluation paves the way for further investigation into the tumour targeting potential of [64Cu]Cu-GluCAB-maleimide-1. An efficient targeted radioligand will allow for further development of a prospective theranostic agent for more personalized patient treatment which potentially improves overall patient prognosis, outcome and health care.

S3-2, a novel long-lasting oxyntomodulin derivative, exerts improvement on diabesity and renal injury through activating GLP-1 and glucagon receptors

AIMS

To prolong the short lifespan of oxyntomodulin (OXM) for treating obesity and diabetes, we designed a novel fused OXM analog, containing an albumin-binding sequence, a protease cleavable tetrapeptide, and a mutated OXM.

MAIN METHODS

We screened two albumin-binding sequences (S3 and S6) to construct OXM derivatives, termed S3-2 (with two cysteines) and S6-0 (without cysteine). After peptides were synthesized, isothermal titration calorimetry (ITC) was applied to assess binding-affinity for HSA. Further in vivo acute efficacies evaluation and candidate selection were performed in diabetic db/db mice via oral glucose tolerance test (OGTT) and glucose-lowering duration test. Chronic efficacy test of selected candidate was also performed in diabetic mice.

RESULTS

Firstly, S3-2 and S6-0 with purity over 99% were prepared. ITC measurements demonstrated that S3-2 and S6-0 associate with HSA with high-affinity (K_d = 12.81 ± 1.11 nM and 26.98 ± 2.39 nM, respectively). Then hypoglycemic efficacies showed deoxidation S3-2 (S3-2re) showed longer hypoglycemic duration than the oxidation one (S3-2ox), and better blood glucose level (BGL) control effect than S6-0. OGTTs in diabetic mice revealed the glucose-lowering efficacies of S3-2re were similar to Liraglutide. The protracted antidiabetic effects of S3-2re were further confirmed by multiple OGTTs in db/db mice. Furthermore, twice weekly injection of S3-2re to db/db mice achieved beneficial effects on body weight gain, glucose tolerance, postprandial BGL and obesity. Moreover, S3-2 produces significantly protective effects on the impaired renal functions of the diabetic mice.

CONCLUSION

S3-2re exhibits outstanding therapeutical potential as a candidate drug for treating the obesity and diabetes.

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.

In vitro and in silico study of the biological activity of manganese(III) inverse-[9-MC-3]-metallacrowns and manganese(II) complexes with the anti-inflammatory drugs diclofenac or indomethacin

In the present contribution, the biological properties of four manganese complexes with the non-steroidal anti-inflammatory drugs sodium diclofenac (Nadicl) or indomethacin (Hindo) in the presence or absence of salicylaldoxime (Η₂sao), i.e. [Μn₆(O)₂(dicl)₂(sao)₆(CH₃OH)₆] 1, [Μn₆(O)₂(indo)₂(sao)₆(H₂O)₄], 2, [Μn(dicl)₂(CH₃OH)₄], 3, and [Μn(indo)₂(CH₃OH)₄], 4 are presented. More specifically, the in vitro cytotoxic effects of the complexes were evaluated against three cancer cell lines (HeLa, MCF-7 and A549 cells) as well as their combinatory activity with the well-known chemotherapeutic drugs irinotecan, cisplatin, paclitaxel and 5-fluorouracil. The biological activity of the complexes was investigated in vitro by studying their affinity to calf-thymus DNA and their binding towards bovine or human serum albumin (HSA). Molecular docking simulations on the crystal structure of HSA and human estrogen receptor alpha (hERa) were employed in order to study in silico the ability of the studied complexes to bind to these proteins.

Engineering a novel protease-based Exendin-4 derivative for type 2 antidiabetic therapeutics

To develop an effective long-acting antidiabetic agent, we designed a novel Exendin-4 derivative (termed LEx4) containing an albumin-binding domain (ABD), a protease-cleavable linker and a native Exendin-4. Here, we present the LEx4 with balanced glucoregulatory activity and prolonged in vivo activity. As a first step, the LEx4 with purity more than 99% was prepared. Microscale thermophoresis (MST) results demonstrated that LEx4 associates with rat and monkey serum albumin with high-affinity (K_a = 1.26 × 10⁶ M^-1 and 1.52 × 10⁶ M^-1, respectively). Then the stability test in vitro showed the enhanced antiproteolytic ability of LEx4 in rat and human plasma compared to native Exendin-4. Oral glucose tolerance test (OGTT) in type 2 diabetic mice showed the glucose-lowering efficacy of LEx4 was clearly dosage-dependent within 25-250 nmol/kg. In addition, the protracted antidiabetic effects of LEx4 were further confirmed by both multiple OGTTs and hypoglycemic efficacies test in type 2 diabetic mice. In Sprague Dawley (SD) rats, LEx4 also showed 3.3-fold longer elimination half-life (t_1/2) than native Exendin-4. Furthermore, once daily injection of LEx4 to db/db mice achieved long-term beneficial effects on body weight, blood biochemical values, glucose tolerance and pancreatic tissue. We believe LEx4 has superior pharmaceutical potential as a therapeutic drug to against type-2 diabetes mellitus (T2DM) based on these results. This strategy of albumin binding is also applicable to other bioactive peptides for development of long-acting therapeutic drugs.

Nonclinical pharmacokinetic and pharmacodynamic characterisation of somapacitan: A reversible non-covalent albumin-binding growth hormone

OBJECTIVE

Somapacitan is an albumin-binding growth hormone derivative intended for once weekly administration, currently in clinical development for treatment of adult as well as juvenile GH deficiency. Nonclinical in vivo pharmacological characterisation of somapacitan was performed to support the clinical trials. Here we present the pharmacokinetic and pharmacodynamic effects of somapacitan in rats, minipigs, and cynomolgus monkeys.

METHODS

Pharmacokinetic studies investigating exposure, absorption, clearance, and bioavailability after single intravenous (i.v.) and subcutaneous (s.c.) administration were performed in all species. A dose-response study with five dose levels and a multiple dose pharmacodynamic study with four once weekly doses was performed in hypophysectomised rats to evaluate the effect of somapacitan on growth and IGF-I production.

RESULTS

Pharmacokinetic profiles indicated first order absorption from the subcutaneous tissue after s.c. injections for somapacitan in all three species. Apparent terminal half-lives were 5-6h in rats, 10-12h in minipigs, and 17-20h in monkeys. Somapacitan induced a dose-dependent growth in hypophysectomised rats (p<0.001) and an increase in plasma IGF-I levels in rats (p<0.01), minipigs (p<0.01), and cynomolgus monkeys (p<0.05) after single dose administration. Multiple once weekly dosing of somapacitan in hypophysectomised rats induced a step-wise increase in body weight with an initial linear phase the first 3-4days in each dosing interval (p<0.001).

CONCLUSION

The nonclinical pharmacokinetic and pharmacodynamic studies of somapacitan showed similar pharmacokinetic properties, with no absorption-limited elimination, increased clearance and increased and sustained levels of IGF-I in plasma for up to 10days after a single dose administration in all three species. Somapacitan induced a dose-dependent increase in body weight and IGF-I levels in hypophysectomised rats. Multiple dosing of somapacitan in hypophysectomised rats suggested a linear growth for the first 3-4days in each weekly dosing interval, whereas daily hGH dosing showed linear growth for approximately two weeks before reaching a plateau level.

Nickel-diflunisal complexes: synthesis, characterization, in vitro antioxidant activity and interaction with DNA and albumins

The reaction of NiCl₂ with the non-steroidal anti-inflammatory drug diflunisal (Hdifl) resulted in the formation of complex [Ni(difl-O)₂(MeOH)₄], 1. The co-existence of a N,N'-donor heterocyclic ligand 2,2'-dipyridylketone oxime (Hpko), 1,10-phenanthroline (phen), 2,2'-bipyridine (bipy) and 2,2'-bipyridylamine (bipyam) led to the formation of complexes [Ni(difl-O)₂(Hpko-N,N')₂], 2, [Ni(difl)₂(phen)(MeOH)₂], 3, [Ni(difl)₂(bipy)(MeOH)₂], 4 and [Ni(difl-O,O')₂(bipyam)], 5, respectively. The complexes were characterized by physicochemical and spectroscopic techniques and the crystal structures of complexes 1 and 2 were determined by X-ray crystallography. The ability of the complexes to scavenge in vitro 1,1-diphenyl-picrylhydrazyl, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) and hydroxyl radicals was investigated; the complexes were more active scavengers than free Hdifl. The interaction of the complexes with serum albumins was investigated by fluorescence emission spectroscopy and the binding constants of the compounds to the albumins were calculated. UV spectroscopy, cyclic voltammetry and viscosity measurements as well as fluorescence emission spectroscopy for the competitive studies of the complexes with ethidium bromide were employed so as to monitor the interaction of the compounds with calf-thymus DNA and revealed intercalation as the most possible mode of binding.

Albumin-based drug delivery: harnessing nature to cure disease

The effectiveness of a drug is dependent on accumulation at the site of action at therapeutic levels, however, challenges such as rapid renal clearance, degradation or non-specific accumulation requires drug delivery enabling technologies. Albumin is a natural transport protein with multiple ligand binding sites, cellular receptor engagement, and a long circulatory half-life due to interaction with the recycling neonatal Fc receptor. Exploitation of these properties promotes albumin as an attractive candidate for half-life extension and targeted intracellular delivery of drugs attached by covalent conjugation, genetic fusions, association or ligand-mediated association. This review will give an overview of albumin-based products with focus on the natural biological properties and molecular interactions that can be harnessed for the design of a next-generation drug delivery platform.

Albumin-based drug delivery: harnessing nature to cure disease

The effectiveness of a drug is dependent on accumulation at the site of action at therapeutic levels, however, challenges such as rapid renal clearance, degradation or non-specific accumulation requires drug delivery enabling technologies. Albumin is a natural transport protein with multiple ligand binding sites, cellular receptor engagement, and a long circulatory half-life due to interaction with the recycling neonatal Fc receptor. Exploitation of these properties promotes albumin as an attractive candidate for half-life extension and targeted intracellular delivery of drugs attached by covalent conjugation, genetic fusions, association or ligand-mediated association. This review will give an overview of albumin-based products with focus on the natural biological properties and molecular interactions that can be harnessed for the design of a next-generation drug delivery platform.

Chemical Conjugation of Evans Blue Derivative: A Strategy to Develop Long-Acting Therapeutics through Albumin Binding

The efficacy of therapeutic drugs is highly dependent on their optimal in vivo pharmacokinetics. Albumin conjugation is considered to be one of the most effective means of protracting the short lifespan of peptides and proteins. In this study, we proposed a novel platform for developing long lasting therapeutics by conjugating a small molecular albumin binding moiety, truncated Evans blue, to either peptides or proteins. Using the anti-diabetic peptide drug Exendin-4 as a model peptide, we synthesized a new long-acting Exendin-4 derivative (denoted as Abextide). Through complexation with albumin in situ, the biological half-life of Abextide was significantly extended. The hypoglycemic effect of Abextide was also improved remarkably over Exendin-4. Thus, Abextide has considerable potential to treat type 2 diabetes. This strategy as a general technology platform can be applied to other small molecules and biologics for the development of long-acting therapeutic drugs.