An Albumin Sandwich Enhances in Vivo Circulation and Stability of Metabolically Labile Peptides.

The effectiveness of numerous molecular drugs is hampered by their poor pharmacokinetics. Different from previous approaches with limited effectiveness, most recently, emerging high-affinity albumin binding moieties (ABMs) for in vivo hitchhiking of endogenous albumin opens up an avenue to chaperone small molecules for long-acting therapeutics. Although several FDA-approved fatty acids have shown prolonged residence and therapeutic effect, an easily synthesized, water-soluble, and high-efficiency ABM with versatile drug loading ability is urgently needed to improve the therapeutic efficacy of short-lived constructs. We herein identified an ideal bivalent Evans blue derivative, denoted as N(tEB)2, as a smart ABM-delivery platform to chaperone short-lived molecules, through both computational modeling screening and efficient synthetic schemes. The optimal N(tEB)2 could reversibly link two molecules of albumin through its two binding heads with a preferable spacer, resulting in significantly extended circulation half-life of a preloaded cargo and water-soluble. Notably, this in situ dimerization of albumin was able to sandwich peptide therapeutics to protect them from proteolysis. As an application, we conjugated N(tEB)2 with exendin-4 for long-acting glucose control in a diabetic mouse model, and it was superior to both previously tested NtEB-exendin-4 (Abextide) and the newly FDA-approved semaglutide, which has been arguably the best commercial weekly formula so far. Hence, this novel albumin binder has excellent clinical potential for next-generation biomimetic drug delivery systems.

Evans Blue Dye: A Revisit of Its Applications in Biomedicine.

Evans blue (EB) dye has owned a long history as a biological dye and diagnostic agent since its first staining application by Herbert McLean Evans in 1914. Due to its high water solubility and slow excretion, as well as its tight binding to serum albumin, EB has been widely used in biomedicine, including its use in estimating blood volume and vascular permeability, detecting lymph nodes, and localizing the tumor lesions. Recently, a series of EB derivatives have been labeled with PET isotopes and can be used as theranostics with a broad potential due to their improved half-life in the blood and reduced release. Some of EB derivatives have even been used in translational applications in clinics. In addition, a novel necrosis-avid feature of EB has recently been reported in some preclinical animal studies. Given all these interesting and important advances in EB study, a comprehensive revisiting of EB has been made in its biomedical applications in the review.

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.

Time-reversal acoustics and ultrasound-assisted convection-enhanced drug delivery to the brain.

Time-reversal acoustics is an effective way of focusing ultrasound deep inside heterogeneous media such as biological tissues. Convection-enhanced delivery is a method of delivering drugs into the brain by infusing them directly into the brain interstitium. These two technologies are combined in a focusing system that uses a "smart needle" to simultaneously infuse fluid into the brain and provide the necessary feedback for focusing ultrasound using time-reversal acoustics. The effects of time-reversal acoustics-focused ultrasound on the spatial distribution of infused low- and high-molecular weight tracer molecules are examined in live, anesthetized rats. Results show that exposing the rat brain to focused ultrasound significantly increases the penetration of infused compounds into the brain. The addition of stabilized microbubbles enhances the effect of ultrasound exposure.

P2-purinoceptor antagonists: II. Blockade of P2-purinoceptor subtypes and ecto-nucleotidases by compounds related to Evans blue and trypan blue.

Effects of Evans blue and four derivatives as well as of trypan blue and four derivatives, mostly smaller fragments but two compounds with an additional ethylene bridge in the center of the molecule, were studied on contractions of the rat vas deferens elicited by alpha, beta-methylene ATP (alpha, beta-MeATP; mediated by P2X-purinoceptors), relaxations of the carbachol-precontracted guinea-pig taenia coli elicited by adenosine 5'-O-(2-thiodiphosphate) (ADP beta S; mediated by P2Y-purinoceptors), and the degradation of ATP by rat vas deferens tissue. All compounds shifted the concentration-response curve of alpha, beta-MeATP in the rat vas deferens to the right, and most compounds increased the maximum of the curve. Each member of the Evans blue series was similar in potency to the corresponding member of the trypan blue series. Where three concentrations were tested, the Arunlakshana-Schild regression was linear, and the slope did not differ from 1. The apparent Kd values were between 0.8 and 385 microM. In the guinea-pig taenia coli, only the members of the trypan blue group were relatively potent, shifting the concentration-response curve of ADP beta S to the right in a surmountable manner. In 2 of 3 cases where three concentrations were tested, the slope of the Arunlakshana-Schild regression was lower than 1. Apparent Kd values in the trypan blue group were between 5.2 and 324 microM. The removal of ATP from the medium by vas deferens tissue was decreased mainly by the members of the Evans blue group, with IC25% values between 13 and 158 (in 1 case > 1000) microM. The results indicate that the position of the sulphonate residues at the terminal naphthalene rings of these compounds hardly influences P2X purinoceptor affinity but greatly influences P2Y affinity and ecto-nucleotidase blockade. Among active compounds, apparent purinoceptor affinity and ecto-nucleotidase blockade increase with the size of the molecules up to Evans blue and trypan blue themselves; introduction of a central ethylene bridge does not result in a further gain in potency. NH01, the desmethyl derivative of Evans blue, seems to be interesting because it is the compound with the highest P2X- versus P2Y-selectivity presently available.