The Vital Role of Melatonin and Its Metabolites in the Neuroprotection and Retardation of Brain Aging.

While primarily produced in the pineal gland, melatonin's influence goes beyond its well-known role in regulating sleep, nighttime metabolism, and circadian rhythms, in the field of chronobiology. A plethora of new data demonstrates melatonin to be a very powerful molecule, being a potent ROS/RNS scavenger with anti-inflammatory, immunoregulatory, and oncostatic properties. Melatonin and its metabolites exert multiple beneficial effects in cutaneous and systemic aging. This review is focused on the neuroprotective role of melatonin during aging. Melatonin has an anti-aging capacity, retarding the rate of healthy brain aging and the development of age-related neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, Huntington's disease, multiple sclerosis, amyotrophic lateral sclerosis, etc. Melatonin, as well as its metabolites, N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK) and N1-acetyl-5-methoxykynuramine (AMK), can reduce oxidative brain damage by shielding mitochondria from dysfunction during the aging process. Melatonin could also be implicated in the treatment of neurodegenerative conditions, by modifying their characteristic low-grade neuroinflammation. It can either prevent the initiation of inflammatory responses or attenuate the ongoing inflammation. Drawing on the current knowledge, this review discusses the potential benefits of melatonin supplementation in preventing and managing cognitive impairment and neurodegenerative diseases.

STAT Protein Thermal Shift Assays to Monitor Protein-Inhibitor Interactions.

STAT3 protein is a sought-after drug target as it plays a key role in the progression of cancer. Many STAT3 inhibitors (STAT3i) have been reported, but accumulating evidence suggests many of these act as off-target/indirect inhibitors of STAT signaling. Herein, we describe the STAT protein thermal shift assay (PTSA) as a novel target engagement tool, which we used to test the binding of known STAT3i to STAT3 and STAT1. This revealed STATTIC, BP-1-102, and Cpd188 destabilized both STATs and produced unique migratory patterns on SDS-PAGE gels, suggesting covalent protein modifications. Mass spectrometry experiments confirmed that these compounds are nonspecifically alkylating STATs, as well as an unrelated protein, NUDT5. These experiments have highlighted the benefits of PTSA to investigate interactions with STAT proteins and have helped reveal the novel reactivity of Cpd188. The described PTSA represents a promising chemical biology tool that could be applied to an array of other protein targets.

Efficacy of eprinomectin 5 mg/mL topical solution administered pour on at 1 mg per kg body weight against Oestrus ovis myiasis in sheep and goats.

The larvae of the nasal bot, Oestrus ovis, mainly parasitize sheep and goats and some species of wild Caprinae but other mammals and humans are also vulnerable to infestation. Eprinomectin 5 mg/mL topical solution (EPRINEX® Multi, Boehringer Ingelheim) administered at 1 mg eprinomectin per kg body weight pour on was recently authorized as an anthelmintic for sheep and goats with zero hours milk withdrawal in several countries in Europe. As the product in cattle has claims against a broad range of parasites including insect parasites and activity against O. ovis has previously been reported following extra-label use in sheep, its therapeutic efficacy against ovine and caprine O. ovis myiasis was evaluated in three regulatory compliant, masked clinical studies. Pre-study recovery of O. ovis larvae from five or six of six randomly selected animals per study site (Bulgaria, one site, sheep; Greece, two sites, sheep or goats) supported the inclusion of the animals from those sites into the studies. The study animals (34 animals per study) were ranked based on bodyweight and allocated randomly to remain untreated (control) or to be treated with eprinomectin 5 mg/mL topical solution at 1 mL per 5 kg body weight pour on. Treatment efficacy was determined based on O. ovis larval counts of eprinomectin 5 mg/mL topical solution-treated vs. untreated animals three weeks after treatment administration. Live O. ovis larvae, including all three instars in each study, were recovered from 13 or 16 of the 17 control animals in the sheep studies (range, 1 to 14 or 5 to 18 larvae, respectively) and from all 17 controls in the goat study (range, 7 to 18 larvae). In each study, eprinomectin 5 mg/mL topical solution-treated animals had significantly (p < 0.001) fewer live O. ovis larvae than the controls. Efficacy of the treatment was 100% and 91.3% against the combined parasitic O. ovis larval stages in sheep and in goats, respectively. The treatment was well accepted by all animals and no health problems were observed throughout the studies. The results of these studies demonstrated eprinomectin 5 mg/mL topical solution administered pour on at 1 mL per 5 kg body weight to be an efficacious and safe treatment of ovine and caprine oestrosis.

Type II & III inhibitors of tropomyosin receptor kinase (Trk): a 2020-2022 patent update.

INTRODUCTION: The Trk family proteins are membrane-bound kinases predominantly expressed in neuronal tissues. Activated by neurotrophins, they regulate critical cellular processes through downstream signaling pathways. Dysregulation of Trk signaling can drive a range of diseases, making the design and study of Trk inhibitors a vital area of research. This review explores recent advances in the development of type II and III Trk inhibitors, with implications for various therapeutic applications. AREAS COVERED: Patents covering type II and III inhibitors targeting the Trk family are discussed as a complement of the previous review, Type I inhibitors of tropomyosin receptor kinase (Trk): a 2020-2022 patent update. Relevant patents were identified using the Web of Science database, Google, and Google Patents. EXPERT OPINION: While type II and III Trk inhibitor development has advanced more gradually compared to their type I counterparts, they hold significant promise in overcoming resistance mutations and achieving enhanced subtype selectivity - a critical factor in reducing adverse effects associated with pan-Trk inhibition. Recent interdisciplinary endeavors have marked substantial progress in the design of subtype selective Trk inhibitors, with impressive success heralded by the type III inhibitors. Notably, the emergence of mutant-selective Trk inhibitors introduces an intriguing dimension to the field, offering precise treatment possibilities.

Investigating the anti-cancer potential of pyrimethamine analogues through a modern chemical biology lens.

Pharmacological inhibition of dihydrofolate reductase (DHFR) is an established approach for treating a variety of human diseases, including foreign infections and cancer. However, treatment with classic DHFR inhibitors, such as methotrexate (MTX), are associated with negative side-effects and resistance mechanisms that have prompted the search for alternatives. The DHFR inhibitor pyrimethamine (Pyr) has compelling anti-cancer activity in in vivo models, but lacks potency compared to MTX, thereby requiring higher concentrations to induce therapeutic responses. The purpose of this work was to investigate structural analogues of Pyr to improve its in vitro and cellular activity. A series of 36 Pyr analogues were synthesized and tested in a sequence of in vitro and cell-based assays to monitor their DHFR inhibitory activity, cellular target engagement, and impact on breast cancer cell viability. Ten top compounds were identified, two of which stood out as potential lead candidates, 32 and 34. These functionalized Pyr analogues potently engaged DHFR in cells, at concentrations as low as 1 nM and represent promising DHFR inhibitors that could be further explored as potential anti-cancer agents.

Attenuation of Hypothyroidism-Induced Cognitive Impairment by Modulating Serotonin Mediation.

Thyroid hormones play an important role in the modeling of neural networks in the brain. Besides its metabolic effects, thyroid dysfunction, and hypothyroidism in particular, is frequently associated with cognitive decline and depressive-like behavior. The current study aimed to examine the changes in behavior, cognition, and memory in rats with propylthiouracil-induced overt hypothyroidism. The behavior and cognition were assessed using the open field test, T-maze, and novel object recognition test. We found significant differences in the behavioral patterns of the hypothyroid animals showing a reduction in locomotor activity, frequency of rearing, and impaired memory function compared to the euthyroid controls. As serotonin is an essential biomarker regulating cognition and mood, we tried to modulate the serotonin mediation in hypothyroid animals through tryptophan administration. Treatment with 5-hydroxy-tryptophan (5-OH-TRP) intraperitoneally for 10 days or directly into the hippocampus as a single injection led to attenuation of the hypothyroidism-induced cognitive and memory decline. A staggering amount of research is suggesting that the common denominators in the pathophysiology of depression and the behavior changes in hypothyroidism are the hippocampal complex and the distorted serotonin metabolism. In our study, it was observed a significant alleviation of cognitive impairment and an improvement of memory performance in hypothyroid rats after 5-OH-TRP administration. Current results are promising and may serve as groundwork for further investigation of functional and structural changes in the hippocampus during a hypothyroid state, and in particular, the effects of serotonin mediation in hypothyroid-associated depressive-like behavior.

Type I inhibitors of tropomyosin receptor kinase (Trk): a 2020-2022 patent update.

INTRODUCTION: Trk inhibitors are significant in the realm of personalized medicine as they target specific genetic alterations, such as NTRK gene fusions, leading to improved treatment outcomes for cancer patients. By tailoring the treatment to the genetic characteristics of the tumor rather than the tumor type, Trk inhibitors offer the potential for more effective and precise therapies, resulting in enhanced response rates and prolonged survival for patients with NTRK fusion-positive cancers. AREAS COVERED: Patents covering type I inhibitors targeting the Trk family are discussed, building upon our prior review series on Trk inhibitors. Relevant patents were identified through the Web of Science database, Google, and Google Patents. EXPERT OPINION: The field of Trk inhibitors has evolved significantly, as reflected in the current patent literature, which emphasizes the selective structural refinement of clinical champions. Efforts now concentrate on enhancing efficacy against on-target resistance mechanisms, with modifications made to improve potency, reduce toxicity, and enhance pharmacokinetics. Combination therapies show potential to address off-target resistance mechanisms and improve treatment outcomes. Challenges remain in accurately diagnosing NTRK gene alterations and integrating screening into routine clinical practice. Trk inhibitors have surpassed their conventional role of inhibition and are now seeing new applications in radiopharmaceutical development and as molecular targeting agents.

Cycloguanil and Analogues Potently Target DHFR in Cancer Cells to Elicit Anti-Cancer Activity.

Dihydrofolate reductase (DHFR) is an established anti-cancer drug target whose inhibition disrupts folate metabolism and STAT3-dependent gene expression. Cycloguanil was proposed as a DHFR inhibitor in the 1950s and is the active metabolite of clinically approved plasmodium DHFR inhibitor Proguanil. The Cycloguanil scaffold was explored to generate potential cancer therapies in the 1970s. Herein, current computational and chemical biology techniques were employed to re-investigate the anti-cancer activity of Cycloguanil and related compounds. In silico modeling was employed to identify promising Cycloguanil analogues from NCI databases, which were cross-referenced with NCI-60 Human Tumor Cell Line Screening data. Using target engagement assays, it was found that these compounds engage DHFR in cells at sub-nanomolar concentrations; however, growth impairments were not observed until higher concentrations. Folinic acid treatment rescues the viability impairments induced by some, but not all, Cycloguanil analogues, suggesting these compounds may have additional targets. Cycloguanil and its most promising analogue, NSC127159, induced similar metabolite profiles compared to established DHFR inhibitors Methotrexate and Pyrimethamine while also blocking downstream signaling, including STAT3 transcriptional activity. These data confirm that Cycloguanil and its analogues are potent inhibitors of human DHFR, and their anti-cancer activity may be worth further investigation.

Pharmacological targeting of MTHFD2 suppresses acute myeloid leukemia by inducing thymidine depletion and replication stress.

The folate metabolism enzyme MTHFD2 (methylenetetrahydrofolate dehydrogenase/cyclohydrolase) is consistently overexpressed in cancer but its roles are not fully characterized, and current candidate inhibitors have limited potency for clinical development. In the present study, we demonstrate a role for MTHFD2 in DNA replication and genomic stability in cancer cells, and perform a drug screen to identify potent and selective nanomolar MTHFD2 inhibitors; protein cocrystal structures demonstrated binding to the active site of MTHFD2 and target engagement. MTHFD2 inhibitors reduced replication fork speed and induced replication stress followed by S-phase arrest and apoptosis of acute myeloid leukemia cells in vitro and in vivo, with a therapeutic window spanning four orders of magnitude compared with nontumorigenic cells. Mechanistically, MTHFD2 inhibitors prevented thymidine production leading to misincorporation of uracil into DNA and replication stress. Overall, these results demonstrate a functional link between MTHFD2-dependent cancer metabolism and replication stress that can be exploited therapeutically with this new class of inhibitors.

A randomized, blinded, controlled, multi-centered field study assessing the treatment of gastrointestinal nematode infections in cats with fluralaner plus moxidectin spot-on solution (Bravecto® Plus).

BACKGROUND: A spot-on formulation containing fluralaner (280 mg/ml) plus moxidectin (14 mg/ml) (Bravecto® Plus) was developed for the treatment of nematode infections as well as providing 12 weeks of protection against insect and acarine parasites in cats. The effectiveness and safety of this product against feline gastrointestinal nematodes was assessed in naturally-infested, client-owned cats under field conditions in Albania, Bulgaria, Germany and Hungary. METHODS: To be eligible for enrollment in this investigator-blinded study cats had to be at least 10 weeks-old, weigh at least 1.2 kg, be clinically healthy, and have a faecal sample testing positive for nematodes no more than eight days prior to treatment. Cats were stratified into blocks of three in order of presentation at each center and randomly allocated in a 2:1 ratio to be treated topically on Day 0 with fluralaner plus moxidectin (minimum dose rates 40 mg/kg and 2 mg/kg, respectively) or emodepside plus praziquantel (minimum dose rates 3 mg/kg and 12 mg/kg, respectively) (Profender®). Faecal samples were collected from cats prior to treatment and 14 ± 4 days later. RESULTS: There were 182 cats randomized to the fluralaner plus moxidectin group, and 91 to the emodepside plus praziquantel group. Prior to treatment the most commonly identified nematode egg was Toxocara cati, found in 79.1 and 82.4% of cats in the fluralaner plus moxidectin and emodepside plus praziquantel groups, respectively. Eggs of Toxascaris leonina were found in 8.2 and 6.6% of cats; of hookworms in 30.8 and 24.2%; and of Capillaria spp. in 7.1 and 4.3%, respectively. After treatment, faecal samples from 98.3% of fluralaner plus moxidectin treated and 96.6% of emodepside plus praziquantel-treated cats were free of nematode ova. Geometric mean faecal egg count reductions for T. cati, the only eggs found in post-treatment faecal samples, were 99.97% and 99.93%, respectively. Treatment with fluralaner plus moxidectin was non-inferior to emodepside plus praziquantel. Both products were safe and well tolerated by cats treated under field conditions. CONCLUSIONS: This field study confirms that, in addition to 12-week extended duration flea and tick control, fluralaner plus moxidectin provides broad spectrum treatment of nematodes in cats.

Small-molecule inhibitor of OGG1 suppresses proinflammatory gene expression and inflammation.

The onset of inflammation is associated with reactive oxygen species and oxidative damage to macromolecules like 7,8-dihydro-8-oxoguanine (8-oxoG) in DNA. Because 8-oxoguanine DNA glycosylase 1 (OGG1) binds 8-oxoG and because Ogg1-deficient mice are resistant to acute and systemic inflammation, we hypothesized that OGG1 inhibition may represent a strategy for the prevention and treatment of inflammation. We developed TH5487, a selective active-site inhibitor of OGG1, which hampers OGG1 binding to and repair of 8-oxoG and which is well tolerated by mice. TH5487 prevents tumor necrosis factor-α-induced OGG1-DNA interactions at guanine-rich promoters of proinflammatory genes. This, in turn, decreases DNA occupancy of nuclear factor κB and proinflammatory gene expression, resulting in decreased immune cell recruitment to mouse lungs. Thus, we present a proof of concept that targeting oxidative DNA repair can alleviate inflammatory conditions in vivo.