Ferritin-Displayed GLP-1 with Improved Pharmacological Activities and Pharmacokinetics

Adapting Ferritin, a Naturally Occurring Protein Cage, to Modulate Intrinsic Agonism of OX40

Ferritin is a multivalent, self-assembling protein scaffold found in most human cell types, in addition to being present in invertebrates, higher plants, fungi, and bacteria, that offers an attractive alternative to polymer-based drug delivery systems (DDS). In this study, the utility of the ferritin cage as a DDS was demonstrated within the context of T cell agonism for tumor killing. Members of the tumor necrosis factor receptor superfamily (TNFRSF) are attractive targets for the development of anticancer therapeutics. These receptors are endogenously activated by trimeric ligands that occur in transmembrane or soluble forms, and oligomerization and cell-surface anchoring have been shown to be essential aspects of the targeted agonism of this receptor class. Here, we demonstrated that the ferritin cage could be easily tailored for multivalent display of anti-OX40 antibody fragments on its surface and determined that these arrays are capable of pathway activation through cell-surface clustering. Together, these results confirm the utility, versatility, and developability of ferritin as a DDS.

Albumin-binding DARPins as scaffold improve the hypoglycemic and anti-obesity effects of exendin-4 in vivo

Type 2 diabetes mellitus (T2DM) and obesity have been considered epidemics and threats to public health worldwide. Exendin-4 (Ex), a GLP-1R agonist, has potential for treating T2DM and obesity. However, Ex has a half-life of only 2.4 h in humans and needs to be administered twice daily, which hampers its clinical application. In this study, we synthesized four new GLP-1R agonists by genetically fusing Ex to the N-terminus of HSA-binding ankyrin repeat proteins (DARPins) via linkers of different lengths, denoted as Ex-DARPin-GSx fusion proteins (x = 0, 1, 2, and 3). The Ex-DARPin fusion proteins were substantially stable, resulting in incomplete denaturation even at 80 °C. The in vitro bioactivity results demonstrated that Ex-DARPin fusion proteins could bind to HSA and activate GLP-1R. The Ex-DARPin fusion proteins had a comparable half-life (29-32 h), which is much longer than that of native Ex (0.5 h in rats). Subcutaneous injection of 25 nmol/kg Ex-DARPin fusion protein normalized blood glucose (BG) levels for at least 72 h in mice. The Ex-DARPin fusion proteins, injected at 25 nmol/kg every three days, significantly lowered BG, inhibited food consumption, and reduced body weight (BW) for 30 days in STZ-induced diabetic mice. Histological analysis of pancreatic tissues using H&E staining revealed that Ex-DARPin fusion proteins significantly improved the survival of pancreatic islets in diabetic mice. The differences in in vivo bioactivity of fusion proteins with different linker lengths were not significant. According to the findings in this study, long-acting Ex-DARPin fusion proteins designed by us hold promise for further development as antidiabetic and antiobesity therapeutic agents. Our findings also indicate that DARPins are a universal platform for generating long-acting therapeutic proteins via genetic fusion, thus broadening the application scope of DARPins.

Multistage targeting and dual inhibiting strategies based on bioengineered tumor matrix microenvironment‐mediated protein nanocages for enhancing cancer biotherapy

Regulation of the apoptotic pathway plays a critical role in inducing tumor cell death and circumventing drug resistance. Survivin protein is the strongest inhibitor of apoptosis found so far. It is highly expressed in several cancers and is a promising target for cancer therapy. However, clinical applications are limited by incomplete inhibition of survivin expression. Here, we present a novel strategy that extended the release of YM155 (an effective survivin inhibitor that works by inhibiting the activity of survivin promoter) and TATm‐survivin (T34A) (TmSm) protein (survivin protein mutant with penetrating peptide, a potential anticancer protein therapeutic) via tumor matrix microenvironment‐mediated ferritin heavy chain nanocages (FTH1 NCs), enabling significant inhibition of survivin activity at both transcript and protein levels. FTS (FTH1‐matrix metalloproteinase‐2‐TmSm)/YM155 NC synthesis was easily scaled up, and these NCs could sequentially release TmSm protein through matrix metalloproteinase‐2 and promote YM155 to enter the nucleus via transferrin receptor 1 (TfR1) binding, which increased the cytotoxicity and apoptosis of Capan‐2 and A549 cells compared to that with individual drugs. Moreover, FTS/YM155 NCs enhanced drug accumulation at tumor sites and had a higher tumor inhibition rate (88.86%) than the compounds alone in A549 tumor‐bearing mice. In addition, FTS/YM155 NCs exerted significant survivin downregulation (4.43‐fold) and caspase‐3 upregulation (4.31‐fold) and showed better therapeutic outcomes without inducing organ injury, which highlights their promising future clinical application in precision therapy. This tumor microenvironment‐responsive platform could be harnessed to develop an effective therapy via multilevel inhibition of cancer targets.

Development of purification process for dual-function recombinant human heavy-chain ferritin by the investigation of genetic modification impact on conformation

Ferritin is a promising drug delivery platform and has been functionalized through genetic modifications. This work has designed and expressed a dual-functional engineered human heavy-chain ferritin (HFn) with the inserted functional peptide PAS and RGDK to extend half-life and improve tumor targeted drug delivery. A facile and cost-effective two-step purification pathway for recombinant HFn was developed. The genetic modification was found to affect HFn conformation, and therefore varied the purification performance. Heat-acid precipitation followed by butyl fast flow hydrophobic interaction chromatography (HIC) has been developed to purify HFn and modified HFns. Nucleic acid removal reached above 99.8% for HFn and modified HFns. However, HFn purity reached above 95% and recovery yield (overall) above 90%, compared with modified HFns purity above 82% and recovery yield (overall) above 58%. It is interesting to find that the inserted functional peptides significantly changed the molecule conformation, where a putative turnover of the E-helix with the inserted functional peptides formed a "flop" conformation, in contrast with the "flip" conformation of HFn. It could be the cause of fragile stability of modified HFns, and therefore less tolerant to heat and acid condition, observed by the lower recovery yield in heat-acid precipitation.

Generation of novel long-acting GLP-1R agonists using DARPins as a scaffold

Glucagon-like peptide-1 (GLP-1) has been considered to be a promising peptide for treatment of type 2 diabetes mellitus (T2DM). However, the extremely short half-life (minutes) of native GLP-1 limits its clinical application potential. Here, we designed two GLP-1 analogues by genetic fusion of GLP-1 to one or two tandem human serum albumin-binding designed ankyrin repeat proteins (DARPins), denoted as GLP-DARPin or GLP-2DARPin. The two DARPin-fusion GLP-1 proteins were expressed in E. coli and purified, followed by measurements of their bioactivities and half-lives in mice. The results revealed that the half-life of GLP-2DARPin, binding two HSA molecules, was approximately 3-fold longer than GLP-DARPin (52.3 h versus 18.0 h). In contrast, the bioactivity results demonstrated that the blood glucose-lowering effect of GLP-DARPin was more potent than that of GLP-2DARPin. The oral glucose tolerance tests indicated that blood glucose levels were significantly reduced for at least 48 h by GLP-DARPin, but were reduced for only 24 h by GLP-2DARPin. Injected once every two days, GLP-DARPin substantially reduced blood glucose levels in streptozotocin (STZ)-induced diabetic mice to the same levels as normal mice. During the treatment course, GLP-DARPin significantly reduced the food intake and body weight of diabetic mice up to approximately 17% compared with the control group. A histological analysis revealed that GLP-DARPin alleviated islet loss in diabetic mice. These findings suggest that long-acting GLP-DARPin holds great potential for further development into drugs for the treatment of T2DM and obesity. Meanwhile, our data indicate that albumin-binding DARPins can be used as a universal scaffold to improve the pharmacokinetic profiles and pharmacological activities of therapeutic peptides and proteins.

Albumin-binding domain extends half-life of glucagon-like peptide-1

Glucagon-like peptide-1 (GLP-1) is considered to be a promising peptide for the treatment of type 2 diabetes mellitus (T2DM). However, the extremely short half-life of GLP-1 limits its clinical application. Albumin-binding domain (ABD) with high affinity for human serum albumin (HSA) has been used widely for half-life extension of therapeutic peptides and proteins. In the present study, novel GLP-1 receptor agonists were designed by genetic fusion of GLP-1 to three kinds of ABDs with different affinities for HSA: GA3, ABD035 and ABDCon. The bioactivities and half-lives of ABD-fusion GLP-1 proteins with different types and lengths of linkers were investigated in vitro and in vivo. The results demonstrated that ABD-fusion GLP-1 proteins could bind to HSA with high affinity. The blood glucose-lowering effect of GLP-1 was significantly improved and sustained by fusion to ABD. Meanwhile, the fusion proteins significantly inhibited food intake, which was beneficial for T2DM and obesity treatment. The half-life of GLP-1 was substantially extended by virtue of ABD. The in vivo results also showed that a longer linker inserted between GLP-1 and ABD resulted in a higher blood glucose-lowering effect. The fusion proteins generated by fusion of GLP-1 to GA3, ABD035 and ABDCon exhibited similar bioactivities and pharmacokinetics in vivo. These findings demonstrate that ABD-fusion GLP-1 proteins retain the bioactivities of natural GLP-1 and can be further developed for T2DM treatment and weight loss. It also indicates that the ABD-fusion strategy can be generally applicable to any peptide or protein, to improve pharmacodynamic and pharmacokinetic properties.