It was previously shown that the original dipeptide mimetic of the 4th loop of neurotrophin-3 (NT-3) hexamethylenediamide bis-(N-monosuccinyl-L-asparaginyl-L-asparagine) (GTS-301), like the full-length neurotrophin, predominantly activates the tyrosine kinase receptor TrkC and has a neuroprotective effect in vitro at concentrations of 10-5-10-12 M, as well as antidiabetic (0.1 and 0.5 mg/kg) and antidepressant (5 and 10 mg/kg) effects after systemic administration in rodents. In this work, the analgesic properties of GTS-301 were identified, which were manifested in the dose range of 0.01-10 mg/kg after acute intraperitoneal injection to rats in the "tail flick" test. Dipeptide GTS-301 increased the threshold of pain response by 20-30%; this effect persisted for at least 24 h after administration.

Relevance. The nerve growth factor (NGF), possessing neuroprotective and neuroregenerative properties, holds promise for the development of medications for the treatment of post-stroke conditions. At the Federal Research Center for Innovator and Emerging Biomedical and Pharmaceutical Technologies, a dimeric dipeptide mimic of NGF with the laboratory code GK-2 was designed and synthesized. Under conditions of experimental cerebral ischemia, it significantly reduced the volume of brain infarction and stimulated neuro- and synaptogenesis. Objective. The aim of this study was to investigate the effects of GK-2 on experimental post-stroke dementia and depression. Methods. Ischemic stroke was induced by occlusion of the middle cerebral artery (MCAO) in Wistar rats. GK-2 was administered intraperitoneally at a dose of 0.5 mg/kg for 21 days post MCAO. Short-term and long-term memory of the animals were assessed 30–40 days post MCAO using the novel object recognition test. Depressive-like state was evaluated through the forced swimming test and sucrose preference test. Results. In animals subjected to MCAO, both short-term and long-term memory exhibited a statistically significant decline of 80 %, along with a depressive-like state characterized by a 50 % increase in total immobility time and a 30 % reduction in sucrose preference, when compared to the sham-lesioned group. Dipeptide GK-2 completely averted the onset of these impairments. Conclusion. The dipeptide mimic of NGF, GK-2, mitigates the development of cognitive and psychomotional impairments in the setting of experimental stroke.

Previously, based on the β-turn of the fourth loop of the brain-derived neurotrophic factor, we obtained GSB-106 (bis-(N-monosuccinyl-L-seryl-L-lysine) hexamethylenediamide), that has pronounced neuroprotective and antidepressant activities in doses of 0.1–10 mg/kg with intraperitoneal and oral administration. For identifying the stereospecificity of the antidepressant-like effect of GSB-106, in this work its enantiomer (GSB-106DD) was synthesized and its antidepressant-like properties were studied. It was shown that GSB-106DD has no antidepressant-like effect when administered intraperitoneally in doses of 0.1 and 1.0 mg/kg. It can be assumed that the stereospecificity of the antidepressant-like activity of GSB-106 dependence on the configuration of amino acid moieties.

A dimeric dipeptide mimetic based on the β-turn of the 4th loop of neurotrophin-3, bis-(N-monosuccinyl-L-asparaginyl-L-asparagine)hexamethylenediamide (GTS-301LL), was recently designed and synthesized by us. GTS-301, like the full-length neurotrophin, activated TrkC and TrkB receptors and exhibited neuroprotective activity on HT22 cells under oxidative stress conditions in the concentration range 10–5 – 10–12 M and antidepressant-like activity in the forced swimming test in mice (10 – 40 mg/kg, intraperitoneally). The stereospecificity of the pharmacological effects of GTS-301LL was revealed by synthesizing the LD, DL, and DD stereoisomers of GTS-301LL and studying their neuroprotective and antidepressant-like properties under the same conditions as for GTS-301LL. Both activities were found to disappear on going from the LL to the DL and DD stereoisomers and were retained on going to the LD stereoisomer. Thus, the stereospecificity of the neuroprotective and antidepressant-like activities of the dipeptide mimetic of neurotrophin-3 GTS-301LL at the N-terminal asparagine residue was proven, which indicated the key role of that amino-acid residue in the interaction with the receptor.

We studied the anti-anxiety effect of a low-molecular-weight mimetic of the BDNF loop 2, hexamethylenediamide bis-(-N-hexanoyl-L-seryl-L-lysine) (GTS-201) in adult animals. GTS-201 at a dose of 5 mg/kg after acute intraperitoneal administration to outbred male and female rats increased the time spent in the open arms and the number of entries into the open arms in the elevated plus maze (EPM). In "highly emotional" male BALB/c mice, GTS-201 exhibited a dose-dependent anxiolytic effect in the EPM in a dose range of 0.5-2.0 mg/kg with a maximum effective dose of 1 mg/kg. These data confirm the previously revealed anti-anxiety properties of GTS-201 in inbred male and female BALB/c mice and rats and indicate the dependence of the pharmacological activity of the BDNF mimetic on animal age.

Ранее нами на основе β-изгиба 4-й петли нейротрофина-3 был сконструирован и синтезирован его миметик, гексаметилендиамид бис-(N-моносукцинил-L-аспарагинил-L-аспарагина) (ГТС-301LL), проявивший свойства полноразмерного нейротрофина. ГТС-301LL активировал TrkC и TrkB рецепторы, обладал защитным действием на клетках HT22 в условиях окислительного стресса в концентрациях 10–5 – 10–12 М и антидепрессантоподобной активностью в тесте вынужденного плавания на мышах в дозах 10 – 40 мг/кг внутрибрюшинно. Для выявления стереоспецифичности эффектов ГТС-301 в настоящей работе синтезированы его LD-, DL- и DD-стереоизомеры и изучены их цитопротекторные и антидепрессантоподобные свойства в тех же условиях, что и для ГТС-301LL. Установлено, что оба вида активности исчезали при переходе от LL- к DL- и DD-стереоизомерам и сохранялись при переходе к LD-стереоизомеру. Таким образом, установлена стереоспецифичность фармакологических эффектов ГТС-301 по N-концевому остатку аспарагина, что свидетельствует о его ключевой роли во взаимодействии с рецептором.

BACKGROUND: The V.V. Zakusov Research Institute of Pharmacology developed hybrid digital sensors for the first, second, and fourth BDNF patches (GSB-214, GTSB-201, and GSB-106, respectively). When tested in vitro, on an oxidative stress model, in the culture of hippocampal neurons NT-22, the compound GTS201 (hexamethylenediamide bis-hexanoyl-seryl-lys), a simulator of the 2nd series of BDNF, activates the TrkB spy receptor and MAPK/Erk kinase pathway but does not affect the PI3K/Akt signature pathway and has neuroprotective activity similar to BDNF. AIM: To study the effect of GTS-201 dipeptide on the behavior of laboratory white rats during the formation of their dependency state and morphine withdrawal syndrome. MATERIALS AND METHODS: Morphine dependence in rats was developed due to administration of morphine in a doses escalation manner ranging from 10 to 20 mg/kg twice daily at 8-h intervals for 5 days. GTS-201 was given in 1- or 5-mg/kg doses for once in 30 minutes before morphine on the 5th day of the experiment or daily (in one of the groups) for 5 days in the morning 30 minutes before morphine administration. On the 5th day of the experiment, animals were tested for the presence of specific signs of morphine withdrawal syndrome in an open field for 5 minutes. Four experimental groups were formed: group 1 morphine hr. + naloxone (active control group); group 2 morphine hr. + GTS-201 (1) + naloxone; group 3 morphine hr. + GTS-201 (5) + naloxone; and group 4 morphine hr. + GTS-201 (1 5) + naloxone. Designations: hr. morphine administration within 5 days; (1) and (5) doses of substances in mg/kg, (1 5) chronic administration of the peptide for 5 days. RESULTS: When studying the effect of GTS-201 dipeptide on behavioral, somatic, and neurological markers of animal behavior after morphine withdrawal, significant changes in the severity of individual signs of withdrawal syndrome were noted. Manifestations of diarrhea were significantly decreased in all groups of animals injected with the peptide. In animals from group 3, morphine hr. + GTS201 (5) + naloxone showed the maximum effect: diarrhea was decreased by 71.0% (p 0.001), convulsions were decreased by 83.3 % (p 0.05), running was decreased by 71.4% (p 0.01), and vocalization was decreased by 62.5% (p 0.05). GTS-201, administered at a dose of 1 mg/kg once, eliminated the appearance of escape attempts in group 2, but the peptide at the same dose completely blocked convulsive reactions in rats in group 4. Despite significant changes in individual indicators, the total index (of morphine withdrawal syndrome for groups chronically injected with morphine) did not change statistically significantly compared with group 1 of active control. In the control group, its value in points was 7.3 0.36 (100%), whereas in groups 24, it ranged from 6.2 (84.9%) to 6.5 (89.0%; p 0.05). CONCLUSIONS: It is assumed that the antiaddictive dipeptide activity of GTS-201 is mediated by activation of these receptors and markers/the Erk-kinase signaling pathway, which does not exclude the involvement of opioid receptor mechanisms in the implementation of the observed behavioral phenomena.

To assess the pharmacological safety of the dipeptide mimetic of the 2nd loop of BDNF (compound GTS-201) when co-administered with ethanol, its effect on the alteration in motor activity induced by ethanol during acute and subchronic administration in mice C57Bl/6 and DBA/2 was studied. It was found that GTS-201 at a dose of 5.0 mg / kg, i.p., without affecting spontaneous motor activity per se, after a preliminary acute administration prevented the development of a sedative reaction caused by ethanol (2.0 g/ kg, i.p.) in C57Bl/6 mice. After subchronic administration, GTS-201 is devoid of psychostimulant effect and impact on the formation of ethanol-induced behavioral sensitization in DBA/2 mice. The data obtained indicate the absence of a psychostimulant component and synergism in the pharmacological profile of GTS-201 when used with ethanol at low dose.

Earlier, in experiments in vitro and in vivo, it was shown that the TrkA receptor agonist compound GK-2, which was a low molecular weight NGF mimetic, had pronounced angiogenic and antiischemic activity. However, it remained unclear whether this activity was associated with the activation of VEGF-A, since, on the one hand, there are reports that NGF-mediated angiogenesis can be initiated by activating NGF of the vascular endothelial growth factor VEGF-A, and on the other hand, it is shown that a selective antagonist of Flk1 receptors specific for VEGF-A, compound SU-5416 does not affect the angiogenic effect of NGF. Purpose of the investigation. Study of the selective VEGF blockade effect on the antiischemic activity of the TrkA receptor agonist GK-2. Methods. Evaluation of the compound GK-2 antiischemic activity was assessed in model experiments simulating hind limb ischemia in rats. Results. It has been shown that against the background of blockade of VEGF-A binding with specific for it (VEGFR1 / Flt-1 / and VEGFR2 / KDR /) receptors, bevacizumab (2.5 mg / kg, i.p., every 3 days for 14 days) compound GK-2 (1 mg / kg, i.p., daily, for 14 days) realizes its antiischemic activity. Conclusion. The results of these experiments indicate that the selective blockade of VEGF does not significantly affect the anti-ischemic activity of the dipeptide NGF mimetic compound GK-2, which has the properties of a TrkA receptor agonist.

The dimeric dipeptide mimetic hexamethylenediamide bis-(N-monosuccinyl-L-asparaginyl-L-asparagine) (GTS-301) was created on the basis of the structure of the exposed region of the neurotrophin-3 4th loop. The new compound, as well as the full-length neurotrophin, activated the TrkC and TrkB receptors. GTS-301 showed neuroprotective activity in experiments on HT-22 mouse hippocampal cells under conditions of oxidative stress and glutamate toxicity at concentrations of 10–12 and 10–8 M, respectively, and antidepressant-like activity in the forced swimming test on mice with 7-day intraperitoneal administration in doses of 10–40 mg/kg.

The study examined the effect of GTS-201, a low-molecular weight mimetic of brain-derived neurotrophic factor (BDNF) loop 2, on persistent alcohol craving in outbred male and female albino rats with ethanol preference score ~50% developed in the free choice paradigm between 10% ethanol and water over 24 weeks. Both single and subchronic (5 days) injections of GTS-201 in a daily dose of 5 μg/kg reduced alcohol deprivation effect in female, but not in male rats. The possibility of in vivo sex-dependent regulation of modeled alcohol craving with a low-molecular-weight dipeptide mimetic of BDNF loop 2 was demonstrated and sex-related differences in this effect were revealed

Previous studies at the V. V. Zakusov Science Research Institute of Pharmacology created a dimeric dipeptide mimetic of the most exposed fourth loop of nerve growth factor (NGF), bis-(N-monosuccinyl-L-glutamyl-Llysine) hexamethylenediamide (GK-2), which activates specific TrkA receptors and has neuroprotective activity in vitro (at 10 5 to 10 9 M) and in vivo (0.1 – 10 mg/kg, i.p., or p.o.). The present report describes the construction and synthesis of a mimetic of the first loop of NGF based on the β-turn (-Lys 32 -Gly 33 -Lys 34 -Glu 35 -), bis-(N-aminocaproyl-glycyl-L-lysine) hexamethylenediamide (GK-6). The structure of GK-6 preserves the central dipeptide fragment of the β-turn -Gly 33 -Lys 34 -, the Lys 32 residue being substituted by its bioisostere – a 6-aminocaproic acid residue - and the dimeric structure of NGF being reproduced by dimerization at the C-terminal using a bivalent hexamethylenediamine spacer. Structure-activity relationships of GK-6 were studied by sequential substitution of the side groups of the peptide by hydrogen to produce bis-(N-acetyl-glycyl-Llysine) hexamethylenediamide (GTS-611) and bis-(N-aminocaproyl-glycyl-glycine) hexamethylenediamine (GTS-613). Mimetic GL-6 and its analogs GTS-613, which contains the N-aminocaproyl radical, had neuroprotective effects at concentrations of 10 6 and 10 5 M in conditions of oxidative stress in HT-22 neuron cultures. Dipeptide GTS-611, in which the aminocaproyl fragment was replaced by an acetyl residue, had no neuroprotective activity in these conditions, pointing to the importance of Lys 32 in NGF for this property. In contrast to the loop 4 mimetic GK-2, the loop 1 mimetics GK-6 and GTS-611 showed differentiation-inducing activity on PC12 cells.

At the Zakusov Institute of Pharmacology designed and synthesized dimeric dipeptide mimetics of the 1st (GK-6) and 4th (GK-2) nerve growth factor loops, 1st (GSB-214), 2nd (GTS-201) and 4th (GSB -106, GSB-106Ac) brain-derived neurotrophic factor loops. Antidepressant activity of GSB-106 has already been established by oral and intraperitoneal administration in 0.1-5.0 mg/kg doses. Newly synthesized mimetics were studied in comparison with GSB-106 for antidepressant-like activity in the forced swim test on male Balb/c mice with a single intraperitoneal administration. It was found that only mimetic of the fourth brain-derived neurotrophic factor loop GSB-106Ac, varied from GSB-106 by replace monosuccinyl fragment to acetyl, has antidepressant activity in doses of 1.0 mg / kg and 5.0 mg / kg.