An albumin‑binding domain and targeting peptide‑based recombinant protein and its enediyne‑integrated analogue exhibit directional delivery and potent inhibitory activity on pancreatic cancer with K‑ras mutation

Molecular Docking and Intracellular Translocation of Extracellular Vesicles for Efficient Drug Delivery

Extracellular vesicles (EVs), including exosomes, mediate intercellular communication by delivering their contents, such as nucleic acids, proteins, and lipids, to distant target cells. EVs play a role in the progression of several diseases. In particular, programmed death-ligand 1 (PD-L1) levels in exosomes are associated with cancer progression. Furthermore, exosomes are being used for new drug-delivery systems by modifying their membrane peptides to promote their intracellular transduction via micropinocytosis. In this review, we aim to show that an efficient drug-delivery system and a useful therapeutic strategy can be established by controlling the molecular docking and intracellular translocation of exosomes. We summarise the mechanisms of molecular docking of exosomes, the biological effects of exosomes transmitted into target cells, and the current state of exosomes as drug delivery systems.

Extension of human GCSF serum half-life by the fusion of albumin binding domain

Granulocyte colony stimulating factor (GCSF) can decrease mortality of patients undergo chemotherapy through increasing neutrophil counts. Many strategies have been developed to improve its blood circulating time. Albumin binding domain (ABD) was genetically fused to N-terminal end of GCSF encoding sequence and expressed as cytoplasmic inclusion bodies within Escherichia coli. Biological activity of ABD-GCSF protein was assessed by proliferation assay on NFS-60 cells. Physicochemical properties were analyzed through size exclusion chromatography, circular dichroism, intrinsic fluorescence spectroscopy and dynamic light scattering. Pharmacodynamics and pharmacokinetic properties were also investigated in a neutropenic rat model. CD and IFS spectra revealed that ABD fusion to GCSF did not significantly affect the secondary and tertiary structures of the molecule. DLS and SEC results indicated the absence of aggregation formation. EC50 value of the ABD-GCSF in proliferation of NFS-60 cells was 75.76 pg/ml after 72 h in comparison with control GCSF molecules (Filgrastim: 73.1 pg/ml and PEG-Filgrastim: 44.6 pg/ml). Animal studies of ABD-GCSF represented improved serum half-life (9.3 ± 0.7 h) and consequently reduced renal clearance (16.1 ± 1.4 ml/h.kg) in comparison with Filgrastim (1.7 ± 0.1 h). Enhanced neutrophils count following administration of ABD-GCSF was comparable with Filgrastim and weaker than PEG-Filgrastim treated rats. In vitro and in vivo results suggested the ABD fusion as a potential approach for improving GCSF properties.

Structure-activity analysis of truncated albumin-binding domains suggests new lead constructs for potential therapeutic delivery

Rapid clearance by renal filtration is a major impediment to the translation of small bioactive biologics into drugs. To extend serum t1/2, a commonly used approach is to attach drug leads to the G-related albumin-binding domain (ABD) to bind albumin and evade clearance. Despite the success of this approach in extending half-lives of a wide range of biologics, it is unclear whether the existing constructs are optimized for binding and size; any improvements along these lines could lead to improved drugs. Characterization of the biophysics of binding of an ABD to albumin in solution could shed light on this question. Here, we examine the binding of an ABD to human serum albumin using isothermal titration calorimetry and assess the structural integrity of the ABD using CD, NMR, and molecular dynamics. A structure-activity analysis of truncations of the ABD suggests that downsized variants could replace the full-length domain. Reducing size could have the benefit of reducing potential immunogenicity problems. We further showed that one of these variants could be used to design a bifunctional molecule with affinity for albumin and a serum protein involved in cholesterol metabolism, PCSK9, demonstrating the potential utility of these fragments in the design of cholesterol-lowering drugs. Future work could extend these in vitro binding studies to other ABD variants to develop therapeutics. Our study presents new understanding of the solution structural and binding properties of ABDs, which has implications for the design of next-generation long-lasting therapeutics.