Aminooxy Click Modification of a Periodate-Oxidized Immunoglobulin G: A General Approach to Antibody-Drug Conjugates with Dye-Mediated Expeditious Stoichiometry Control

A universal approach to the construction of antibody-drug conjugates (ADCs) has been developed. It relies on periodate oxidation of naturally present glycans of immunoglobulin G, followed by oxime ligation and, optionally, copper(I)-catalyzed alkyne-azide cycloaddition for conjugation with a toxic payload. The introduction of highly absorbing cyanine dyes into the linker allows for facile determination of the drug-antibody ratio. We applied this methodology to the synthesis of cytotoxic conjugates of an antibody against the tumor-associated antigen PRAME with doxorubicin and monomethyl auristatin E (MMAE). The resultant conjugates retained their affinity to a large extent, yet their cytotoxicity in vitro varied dramatically: while the doxorubicin-based conjugate did not produce any effect on cells, the MMAE-based one demonstrated specific activity against PRAME-expressing cancer cell lines. Importantly, the latter conjugate constitutes the first reported example of a PRAME-targeting ADC.

Sensitive Immunofluorescent Detection of the PRAME Antigen Using a Practical Antibody Conjugation Approach

Bioconjugation of antibodies with various payloads has diverse applications across various fields, including drug delivery and targeted imaging techniques. Fluorescent immunoconjugates provide a promising tool for cancer diagnostics due to their high brightness, specificity, stability and target affinity. Fluorescent antibodies are widely used in flow cytometry for fast and sensitive identification and collection of cells expressing the target surface antigen. Nonetheless, current approaches to fluorescent labeling of antibodies most often use random modification, along with a few rather sophisticated site-specific techniques. The aim of our work was to develop a procedure for fluorescent labeling of immunoglobulin G via periodate oxidation of antibody glycans, followed by oxime ligation with fluorescent oxyamines. Here, we report a novel technique based on an in situ oxime ligation of ethoxyethylidene-protected aminooxy compounds with oxidized antibody glycans. The approach is suitable for easy modification of any immunoglobulin G, while ensuring that antigen-binding domains remain intact, thus revealing various possibilities for fluorescent probe design. The technique was used to label an antibody to PRAME, a cancer-testis protein overexpressed in a number of cancers. A 6H8 monoclonal antibody to the PRAME protein was directly modified with protected-oxyamine derivatives of fluorescein-type dyes (FAM, Alexa488, BDP-FL); the stoichiometry of the resulting conjugates was characterized spectroscopically. The immunofluorescent conjugates obtained were applied to the analysis of bone marrow samples from patients with oncohematological diseases and demonstrated high efficiency in flow cytometry quantification. The approach can be applied for the development of various immunofluorescent probes for detection of diagnostic and prognostic markers, which can be useful in anticancer therapy.

[AFLP analysis of the genetic diversity of closely related Rhododendron species of the section Rhodorastra (Ericaceae) from Siberia and the Far East of Russia]

Using AFLP analysis, the genetic variation in four population samples of Rhododendron ledebourii, three such samples of Rh. dauricum, two samples of Rh. sichotence, and one sample of Rh. mucronulatum was examined. Application of three selective primer pairs provided genotyping of 87 accessions from the four species at 213 loci. An analysis of molecular variance revealed a high level of differences between all four species (F(ST) = 0.172). Populations within the species were also differentiated: for Rh. dauricum F(ST) = 0.245; Rh. ledebourii F(ST) = 0.264; Rh. sichotence F(ST) = 0.034. The highest Nei distance was observed for Rh. mucronulatum with Rh. dauricum and Rh. ledebourii (D = 0.057 and 0.069, respectively). Similarity was observed between the species pairs of Rh. ledebourii-Rh. dauricum (0.032) and Rh. sichotense-Rh. mucronulatum (0.034). The Far Eastern species Rh. sichotense and Rh. mucronulatum were characterized by an elevated level of intrapopulation variation. The data from the AFLP-based analysis of differentiation and variation that were thus obtained were compared with the literature data on the morphological criteria that differentiate the species of interest and those regarding the history of the formation of their ranges. The independence of all the species we examined was confirmed.

[Neuroprotective effect of kapakh, representative of new nootropic class non-anticholinesterase organophosphoric compounds]

In vivo and in vitro experiments revealed the neuroprotective activity of CAPAH, a representative of the new nootropic class phosphorylated carboxylic acid hydrazides. The mechanisms of this action, which were due to the membranous stabilizing activity of the drug and its affinity for glycine strychnine-sensitive sites of MMDA receptors (Ki = 8.8.10(-5) M). Six analogues of CAPAH have been also found to have affinity for these types of receptors; based on the examination of structure-affinity relationship, putative pharmacophores (only radicals of the benzene ring of a molecule in the para position exerted effects on affinity changes) were revealed. The findings give a deep insight into the mechanism of nootropic activity and open vistas for synthesizing phosphorylated carboxylic acid hydrazides as potential neuroprotective agents interacting with glycine strychnine-sensitive sites of MMDA receptor.

[Cytochemical demonstration of cyclic nucleotide phosphodiesterases in the taste buds of Testudo horsefieldi turtles upon exposure to flavored substances]

Phosphodiesterase of cyclic nucleotides was found cytochemically on the plasmat membrane of the apical part and microvillar projections of the receptor cells and, to a lower extent on the membranes of microvilli of the supporting cells as well as on the mucose granules of the taste buds of the tortoise Testudo horsfieldi. Administration of 1/250 M quinine chloride to the surface of the tongue results in the disappearance of the products of the enzymic reaction from the surface of the mentioned membranes. After application of 0.25 M surcrose, the reaction products are found within the apical part of the receptor cells on the membranes of the plain endoplasmic reticulum. Possible role of cyclic nucleotides in taste reception is discussed.

[Study of the composition and elaboration of a catalytic method for purifying the gaseous waste from neomycin and monomycin production]

Composition of the waste gases in the production of neomycin and monomycin at the stages of fermentation, coagulation and filtration was studied. It was found that the main components of the waste gases in the production of neomycin and monomycin were carbon dioxide (0.15-6.0 mg/1), moisture (22-34 mg/1) and organic substances (0.5-4.2 mg/1) calculated for carbon dioxide. These substances have a specific unpleasant odour. A procedure for purification of the waste gases in the production of neomycin and monomycin by catalytic oxidation was developed.