New drugs and phosphorescent labels
New organic molecules were synthesized and shown to act as inhibitors of carbonic anhydrases. Particularly, new effective antagonists of carbonic anhydrase II isoform (specific target in glaucoma) were synthesized. The compounds are able to reduce intraocular pressure at efficiency similar to the existing analogues, but at lower doses, showing promise as effective, but safer, carbonic anhydrase inhibitors. Thus, these compounds are promising for delivery of ocular controlled release systems.
Krasavin et al European Journal of Medicinal Chemistry. 2019. V. 168. P. 301–314. https://doi.org/10.1016/j.ejmech.2019.02.044
A number of peptide inhibitors of vascular epithelial growth factor (VEGF) have been synthesized. Such peptides are promising drugs, that may slow down or stop the formation of harmful formation of leaky neovessels in the eye (e.g. in age-related macular degeneration). The effectiveness of these peptides was shown using various in vitro binding assays and cell experiments. The developed anti-VEGF peptides are of interest not only in ophthalmology, but also for the treatment of various cancers and psoriasis, that are also characterized by overexpression of VEGF.
For effective bioimaging of drug delivery systems, new phosphorescent labels based on complexes of gold, iridium and platinum were synthesized. These complexes contained special reactive groups, which are necessary for their covalent conjugation with liposomes and polymer particles. It was shown that the complexes and their conjugates with polymer carriers have useful photophysical properties, namely, lifetimes in the microsecond range and the ability to emit in the NIR region. Successful imaging with iridium labels was also performed in the cultured cells and in the animal eyes.
Kritchenkov et al. Bioconjugate Chemistry. 2020. V.31. P.1327–1343, https://doi.org/10.1021/acs.bioconjchem.0c00020
New polymers and drug delivery systems
The biocompatible polymers served as the base for generation of drug delivery systems. The synthesis of new polymers was performed in three main directions: 1) polymers for the controlled delivery of small molecules; 2) the synthesis and modification of macromolecules to construct systems for the nucleic acid (RNA, DNA) delivery; 3) the production of hydrophilic polymeric conjugates of covalently bound anti-VEGF peptides. New macromolecules that were synthesized and comprehensively studied include: amphiphilic derivatives of polysaccharides (cholesteryl-succinyl-chitosan, succinyl-chitin) for the delivery of small molecules; cationic chitosan derivatives for siRNA delivery; statistical copolymers of poly(lysine-co-phenylalanine) with different compositions and stereochemistry for encapsulation of dexamethasone; ternary random copolymers of amino acids containing L-lysine, L-glutamic acid and L-phenylalanine/L-isoleucine for nucleic acid delivery; heparin and chondroitin sulphate grafted with poly(N-isopropylacrylamide) for the delivery of dexamethasone and carbonic anhydrase inhibitors; covalently conjugated forms of dexamethasone and anti-VEGF peptides with hyaluronic acid, chitosan and polyamino acids; melanosome-like polymer based on 3-(2-methacrylamidoethyl)-1H-indole-2-carboxylic acid. New polymeric colloidal systems, potentially suitable as drug delivery systems, have been developed: micro- and nanoparticles based on poly(lactic acid), with a variable amount of polyelectrolyte layers based on poly(L-lysine) and heparin on their surface; micelles based on amphiphilic chitosans and polyaminoacids; thermo- and pH-sensitive nanogels. The resulting nanoparticles were characterized using physical, physicochemical, and biological methods of analysis. Organic linkers have been synthesized to act as intermediates between a drug compound and a polymer/nanoparticle/cell surface, as well as cross-linking agents for polymer chains, designed to provide controlled cleavage/release of a therapeutic agent in changing environmental conditions (e.g. light, enzymes). The materials were safe in cultured human cells, including retinal and corneal cells of the eye. The controlled release properties of various systems were also evaluated.
Pilipenko et al. Pharmaceutics. 2019. V. 11. I. 7. Article #317. https://doi.org/10.3390/pharmaceutics11070317
Pilipenko et al Carbohydrate Polymers. 2020. V.248, 116764 https://doi.org/10.1016/j.carbpol.2020.116764
Osipova et al. Pharmaceutics. 2020. V. 12. Article #39 https://doi.org/10.3390/pharmaceutics12010039
The biohybrids were formed using two approaches: (a) internalization of drug or gene containing nanoparticles into cells; (b) covalent modification of the cell surface with various linkers.
According to the first method, nanoparticles based on poly(lactic acid) modified with camel antibodies were used to encapsulate a new drug – perchlozone, for the treatment of multi-drug resistant tuberculosis. The survival rate of tuberculotic mice improved by 50% by peritoneal injection of the nanoparticles. As compared to the oral drug dose, more than 10 times lower dose was effective when it was delivered in the particles. This resulted in significantly lower hepatotoxicity. These beneficial effects were probably related to uptake of the particles by peritoneal macrophages, followed by their migration to the inflammation locus by chemotaxis. In addition to these experiments, methods for cellular internalization of the particles were established.
According to the second method, a technology was developed for covalent modification of the surface of living T-cells by metabolic labelling with tetraacetate N-azidoacetylmannosamine (Ac4ManNAz). Ac4ManNAz integrated into polysaccharides on the cell surface. Thereafter, a hydrophilic fluorescent dye and selected anti-VEGF peptides (modified with dibenzocyclooctine) were bound to azide groups on the cell surface via the click reaction (azide-alkyne cycloaddition). The selected fluorescent dye was used as biomarker to optimize the cell surface modification protocols. Dibenzocyclooctin-modified anti-VEGF peptides were bound to cells in order to obtain biohybrid systems capable of detecting and selectively binding the VEGF protein to block its neovascular effects. The modified cells retained their viability during these processes. Experiments were carried out to demonstrate the directed transport of the cellular biohybrids according to chemotaxis.
L. Churilov, V. Korzhikov-Vlakh et al. Pharmaceutics. 2019. V.11. I.1. Article #2. https://doi.org/10.3390/pharmaceutics11010002
Results of chemiselective ligation of HEP G-2 cells.
New pharmacokinetic models
Computer models have been developed to simulate pharmacokinetics after intravitreal injections of polymeric materials and biohybrids into the eye. The results of computer modelling are in good agreement with pharmacokinetic data obtained by direct measurements of the concentration of drugs in vitreous fluid. The models take into account key parameters such as vitreous volume, vitreous diffusion coefficient, clearance via posterior and anterior routes, and flow factors (aqueous humor, blood). The effect of the degradation rate can also be taken into account in such modelling, if the degradation of the polymer and the size of the resulting fragments are estimated in advance during preliminary in vitro studies. These models provide a useful links from in vitro to in vivo and from animal studies to clinical situation.