Structure-based design of a phosphotyrosine-masked covalent ligand targeting the E3 ligase SOCS2

The Src homology 2 (SH2) domain recognizes phosphotyrosine (pY) post translational modifications in partner proteins to trigger downstream signaling. Drug discovery efforts targeting the SH2 domains have long been stymied by the poor drug-like properties of phosphate and its mimetics. Here, we use structure-based design to target the SH2 domain of the E3 ligase suppressor of cytokine signaling 2 (SOCS2). Starting from the highly ligand-efficient pY amino acid, a fragment growing approach reveals covalent modification of Cys111 in a co-crystal structure, which we leverage to rationally design a cysteine-directed electrophilic covalent inhibitor MN551. We report the prodrug MN714 containing a pivaloyloxymethyl (POM) protecting group and evidence its cell permeability and capping group unmasking using cellular target engagement and in-cell 19F NMR spectroscopy. Covalent engagement at Cys111 competitively blocks recruitment of cellular SOCS2 protein to its native substrate. The qualified inhibitors of SOCS2 could find attractive applications as chemical probes to understand the biology of SOCS2 and its CRL5 complex, and as E3 ligase handles in proteolysis targeting chimera (PROTACs) to induce targeted protein degradation.</p

Discovery of XL01126:A Potent, Fast, Cooperative, Selective, Orally Bioavailable, and Blood-Brain Barrier Penetrant PROTAC Degrader of Leucine-Rich Repeat Kinase 2

[Image: see text] Leucine-rich repeat kinase 2 (LRRK2) is one of the most promising targets for Parkinson’s disease. LRRK2-targeting strategies have primarily focused on type 1 kinase inhibitors, which, however, have limitations as the inhibited protein can interfere with natural mechanisms, which could lead to undesirable side effects. Herein, we report the development of LRRK2 proteolysis targeting chimeras (PROTACs), culminating in the discovery of degrader XL01126, as an alternative LRRK2-targeting strategy. Initial designs and screens of PROTACs based on ligands for E3 ligases von Hippel–Lindau (VHL), Cereblon (CRBN), and cellular inhibitor of apoptosis (cIAP) identified the best degraders containing thioether-conjugated VHL ligand VH101. A second round of medicinal chemistry exploration led to qualifying XL01126 as a fast and potent degrader of LRRK2 in multiple cell lines, with DC(50) values within 15–72 nM, D(max) values ranging from 82 to 90%, and degradation half-lives spanning from 0.6 to 2.4 h. XL01126 exhibits high cell permeability and forms a positively cooperative ternary complex with VHL and LRRK2 (α = 5.7), which compensates for a substantial loss of binary binding affinities to VHL and LRRK2, underscoring its strong degradation performance in cells. Remarkably, XL01126 is orally bioavailable (F = 15%) and can penetrate the blood–brain barrier after either oral or parenteral dosing in mice. Taken together, these experiments qualify XL01126 as a suitable degrader probe to study the noncatalytic and scaffolding functions of LRRK2 in vitro and in vivo and offer an attractive starting point for future drug development

Comparative Assessment of Quality Requirements for Medicinal Products Containing Diosmin

Currently, there is an increase in preand post-approval testing of medicinal products containing diosmin and hence a need to unify approaches to standardisation of this group of pharmaceuticals. Moreover, the State Pharmacopoeia of the Russian Federation lacks a monograph for these products.The aim of the study was to determine an approach to standardisation of medicinal products containing diosmin.Materials and methods: the study analysed scientific publications, as well as monographs of leading foreign pharmacopoeias. Experimental work was carried out using samples of diosmin-containing pharmaceuticals in the form of 500 and 1000 mg film-coated tablets produced by Russian and foreign manufacturers. The study involved high performance liquid chromatography with UV detection using an Agilent 1260 Infinity II liquid chromatography system with a diode array detector. The following reference standards were used: a diosmin RS, USP grade; a hesperidin CRS, Ph. Eur. Grade; and a diosmin CRS for testing chromatography system suitability for identification of impurities A, B, C, D, E, and F, Ph. Eur. grade.Results: the authors reviewed quality requirements for pharmaceutical products containing diosmin and analysed experimental data obtained during preand post-approval testing of Russian and foreign medicines. The comparison of regulatory documents for registered diosmin-containing medicinal products showed a difference in approaches to assessing the contents of related substances and active pharmaceutical ingredients. Having analysed the literature, experimental data and regulatory requirements for standardisation of diosmin-containing pharmaceuticals, the authors recommended an approach to standardisation. According to the approach, concomitant flavonoids (hesperidin, isorchoifolin, linarin, and diosmetin) contributing to the pharmacological activity of a medicinal product are specified as part of Assay, and process-related by-products (impurities A and D) are specified and evaluated as part of Related substances tests.Conclusion: the authors propose to evaluate the contents of concomitant flavonoids (hesperidin, isorchoifolin, linarin, diosmetin) under Assay and to specify impurities A and D, as well as single unidentified impurities and total amount of impurities under Related substances

Разработка унифицированной ВЭЖХ-методики определения родственных примесей и количественной оценки действующего вещества препаратов папаверина гидрохлорида

Abstract. Papaverine hydrochloride products are used as anticonvulsants in routine medical practice. Most of the approved product specification files include thin-layer chromatography for assessment of product-related impurities and UV spectrophotometry for determination of active pharmaceutical ingredients. An HPLC assay is not used for determination of papaverine hydrochloride in drug dosage forms.The aim of the study was to develop an HPLC test method for determination of product-related impurities and for quantification of papaverine hydrochloride in solutions for injection, tablets, and rectal suppositories.Materials and methods: samples of the following Russian-made papaverine products were used in the study: Papaverine, solution for injection, 20 mg/mL; Papaverine, rectal suppositories, 20 mg; Papaverine, tablets, 40 mg. The Agilent 1260 Infinity II DAD System was used for the HPLC assay, and the Agilent 8453Е UV-Vis System was used for recording UV spectra. The determination of product-related impurities and the assay of active ingredients were performed simultaneously by HPLC using a reversed-phase column Kromasil 100-5-C18, 250×4.6 mm, 5 μm, the gradient elution mode, and detection at        238 nm. Papaverine Hydrochloride USP RS, 99% purity, and Noscapine EP CRS were used as reference standards.Results: the study demonstrated that determination of product-related impurities and assay of active ingredients in papaverine products can be performed simultaneously using HPLC.Conclusions: the authors proposed an HPLC test method for determination of active ingredients in papaverine products, which is aligned with the “consistent standardisation” principle and can be recommended for inclusion into draft monographs for papaverine products.Резюме. Препараты папаверина гидрохлорида применяются в медицинской практике в качестве спазмолитического средства. В большинство зарегистрированных нормативных документов на эти препараты включена методика оценки родственных примесей методом тонкослойной хроматографии, для определения действующего вещества используется УФ-спектрофотометрия. Количественное определение папаверина гидрохлорида в лекарственных формах методом высокоэффективной жидкостной хроматографии (ВЭЖХ) не проводится.Цель работы: разработка методики определения родственных примесей и количественного определения папаверина гидрохлорида в растворе для инъекций, таблетках и суппозиториях ректальных методом ВЭЖХ.Материалы и методы: объектами исследования являлись образцы препаратов папаверина отечественных производителей: «Папаверин, раствор для инъекций 20 мг/мл», «Папаверин, суппозитории ректальные, 20 мг», «Папаверин, таблетки 40 мг». Исследование проводили методом ВЭЖХ на жидкостном хроматографе Agilent 1260 Infinity II DAD System , регистрацию УФ-спектров – на спектрофотометре Agilent 8453Е UV-Vis System. Оценку содержания родственных примесей и количественное определение действующих веществ проводили одновременно методом ВЭЖХ на обращенно-фазовой колонке Kromasil 100-5-C18, размер колонки 250×4,6 мм, размер частиц 5 мкм, в условиях градиентного элюирования с детектированием при 238 нм. В качестве стандартных образцов использовали папаверина гидрохлорид квалификации USP RS с содержанием действующего вещества 99,9% и носкапин квалификации EP CRS.Результаты: показана возможность одновременного определения родственных примесей и количественного определения действующих веществ в препаратах папаверина методом ВЭЖХ.Выводы: предложена методика определения действующих веществ в препаратах папаверина методом ВЭЖХ, удовлетворяющая принципу сквозной стандартизации, которая может быть рекомендована для включения в проект фармакопейных статей на препараты папаверина

Сравнительная оценка требований к качеству лекарственных препаратов, содержащих диосмин

Currently, there is an increase in pre- and post-approval testing of medicinal products containing diosmin and hence a need to unify approaches to standardisation of this group of pharmaceuticals. Moreover, the State Pharmacopoeia of the Russian Federation lacks a monograph for these products.The aim of the study was to determine an approach to standardisation of medicinal products containing diosmin.Materials and methods: the study analysed scientific publications, as well as monographs of leading foreign pharmacopoeias. Experimental work was carried out using samples of diosmin-containing pharmaceuticals in the form of 500 and 1000 mg film-coated tablets produced by Russian and foreign manufacturers. The study involved high performance liquid chromatography with UV detection using an Agilent 1260 Infinity II liquid chromatography system with a diode array detector. The following reference standards were used: a diosmin RS, USP grade; a hesperidin CRS, Ph. Eur. Grade; and a diosmin CRS for testing chromatography system suitability for identification of impurities A, B, C, D, E, and F, Ph. Eur. grade.Results: the authors reviewed quality requirements for pharmaceutical products containing diosmin and analysed experimental data obtained during pre- and post-approval testing of Russian and foreign medicines. The comparison of regulatory documents for registered diosmin-containing medicinal products showed a difference in approaches to assessing the contents of related substances and active pharmaceutical ingredients. Having analysed the literature, experimental data and regulatory requirements for standardisation of diosmin-containing pharmaceuticals, the authors recommended an approach to standardisation. According to the approach, concomitant flavonoids (hesperidin, isorchoifolin, linarin, and diosmetin) contributing to the pharmacological activity of a medicinal product are specified as part of Assay, and process-related by-products (impurities A and D) are specified and evaluated as part of Related substances tests.Conclusion: the authors propose to evaluate the contents of concomitant flavonoids (hesperidin, isorchoifolin, linarin, diosmetin) under Assay and to specify impurities A and D, as well as single unidentified impurities and total amount of impurities under Related substances.В настоящее время существует потребность в унификации подходов к стандартизации препаратов диосмина в связи с увеличением объема проведения регистрационной и пострегистрационной экспертизы препаратов этой группы, а также с необходимостью разработки фармакопейной статьи на препараты диосмина для Государственной фармакопеи Российской Федерации.Цель работы: определение подхода к стандартизации лекарственных препаратов, содержащих диосмин.Материалы и методы: объектами исследования служили данные научных публикаций, а также частные монографии ведущих зарубежных фармакопей. Экспериментальная работа проводилась на образцах препаратов диосмина в форме таблеток, покрытых пленочной оболочкой, в дозировке 500 и 1000 мг, отечественных и зарубежных производителей. Исследование осуществляли методом высокоэффективной жидкостной хроматографии с УФ-детектированием на жидкостном хроматографе Agilent 1260 Infinity II DAD System. В качестве стандартных образцов использовали диосмин квалификации USP RS, гесперидин квалификации EP CRS и диосмин для проверки пригодности хроматографической системы квалификации EP CRS для идентификации примесей A, B, C, D, E и F.Результаты: проведен аналитический обзор требований к качеству лекарственных препаратов, содержащих диосмин, с анализом экспериментальных данных, полученных в ходе регистрационной и пострегистрационной экспертизы российских и зарубежных лекарственных средств. Сравнительный анализ нормативной документации зарегистрированных лекарственных препаратов, содержащих диосмин, показал различие в подходах к оценке содержания родственных примесей и действующих веществ. Анализ данных литературы, экспериментальных данных и требований нормативных документов в области стандартизации, предъявляемых к стандартизации препаратов, содержащих диосмин, позволяет рекомендовать подход, согласно которому сопутствующие флавоноиды (гесперидин, изорхойфолин, линарин, диосметин), обеспечивающие вклад в фармакологическое действие препарата, нормируются в составе показателя «Количественное определение». Примеси, относящиеся к побочным продуктам при производстве диосмина (примеси А и D), нормируются и оцениваются при испытаниях по показателю «Родственные примеси».Выводы: предложено проводить оценку содержания сопутствующих флавоноидов (гесперидина, изорхойфолина, линарина, диосметина) в составе показателя «Количественное определение», примеси А и D, а также единичные неидентифицированные примеси и сумму примесей нормировать в показателе «Родственные примеси»

Towards a Biologically Plausible Computational Model of Developmental Learning with Robotic Applications

Building robots that are able to efficiently operate in the real world is a formidable challenge. Functioning in the real world is extremely difficult, because it requires a vast amount of knowledge about the world, specific tasks, and the robot’s own body, as well as the ability to handle unexpected situations. Despite the undoubtable power of modern machine learning approaches and great success in the solving of task-specific problems (especially in controlled environments), such algorithms as supervised and reinforcement learning have significant limitations in real world environments, because they require from the designer either a prepared set of labelled examples of desired behaviours or an adequate reward function. Even having these pre-requisites, the algorithm faces the problem of the greater size of the environment comparing to the agent’s learning abilities. In contrast, humans or animals efficiently gather knowledge of the world during the developmental stage. Children and young animals are intrinsically motivated to use exploration and play to select and learn information about the world that is useful in the future, but also fits into their existing mental schemas and satisfies the physical constraints. According to White, intrinsically motivated learning (also referred to as self-motivated exploratory activity) is responsible for the formation of a wide range of salient competences, from grasping and walking to language. Moreover, this ability to explore and learn for the sake of knowledge typically persists over a lifetime, progressing in complexity and allowing the adaption of the organism’s behaviour to the dynamically changing environment. The current research project aims to apply the developmental learning concept to robotics, taking an approach of building a biologically plausible model of intrinsic motivation. Page ii In particular, we have proposed a theory that explains neurological mechanisms underlying an inverted U-shaped dependence of the activity of deep cortical areas with respect to familiarity of perceived information. We have shown that our model is able to account for recent neuroimaging studies that have not been explained yet. Furthermore, we have linked the neural activity to behavioural response through the feeling of pleasure, showing that the neural activity effectively might be considered as a reinforcement signal that shapes the animal behaviour. We have conducted several computational experiments showing that such behaviour could structure exploration and is beneficial for building a world model in close-to-real world conditions. Finally, we have demonstrated in a simulation that exploration on the periphery of knowledge could lead to an emergence of competences

Dissociable forms of repetition priming: A computational model

Nondeclarative memory and novelty processing in the brain is an actively studied field of neuroscience, and reducing neural activity with repetition of a stimulus (repetition suppression) is a commonly observed phenomenon. Recent findings of an opposite trend specifically, rising activity for unfamiliar stimuli—question the generality of repetition suppression and stir debate over the underlying neural mechanisms. This letter introduces a theory and computational model that extend existing theories and suggests that both trends are, in principle, the rising and falling parts of an inverted U-shaped dependence of activity with respect to stimulus novelty that may naturally emerge in a neural network with Hebbian learning and lateral inhibition. We further demonstrate that the proposed model is sufficient for the simulation of dissociable forms of repetition priming using real-world stimuli. The results of our simulation also suggest that the novelty of stimuli used in neuroscientific research must be assessed in a particularly cautious way. The potential importance of the inverted-U in stimulus processing and its relationship to the acquisition of knowledge and competencies in humans is also discusse