Discovery of Gut-Restricted Small-Molecule Inhibitors of Intestinal Sodium-Dependent Phosphate Transport Protein 2b (NaPi2b) for the Treatment of Hyperphosphatemia.

NaPi2b is primarily expressed in the small intestine, lungs, and testes and plays an important role in phosphate homeostasis. The inhibition of NaPi2b, responsible for intestinal phosphate absorption, is considered to reduce serum phosphate levels, making it a promising therapeutic approach for hyperphosphatemia. Using a novel phosphate uptake inhibitor 3 (IC50 = 87 nM), identified from an in-house compound collection in human NaPi2b-transfected cells as a prototype compound, we conducted its derivatization based on a Ro5-deviated strategy to develop orally administrable small-molecule NaPi2b inhibitors with nonsystemic exposure. Consequently, compound 15, a zwitterionic compound with a potent in vitro phosphate uptake inhibitory activity (IC50 = 64 nM) and a low membrane permeability (Pe < 0.025 × 10-6 cm/s), was developed. Compound 15 showed a low bioavailability (F = 0.1%) in rats and a reduction in phosphate absorption in the rat intestinal loop assay comparable to sevelamer hydrochloride, a clinically effective phosphate binder for treating hyperphosphatemia.

Semicarbazone derivatives as promising therapeutic alternatives in leishmaniasis.

In the present study, we investigated the in vitro and in vivo leishmanicidal activity of synthetic compounds, containing a semicarbazone scaffold as a peptide mimetic framework. The leishmanicidal effect against amastigotes of Leishmania amazonensis was also evaluated at concentration of 100 µM-0.01 nM. The derivatives 2e, 2f, 2g and 1g, beyond the standards miltefosine and pentamidine, significantly diminished the number of L. amazonensis amastigotes in macrophages. These derivatives were also active against amastigotes of L. braziliensis. As 2g presented potent leishmanicidal activity against the amastigotes of L. amazonensis in macrophages, we also investigated the in vivo leishmanicidal activity of this compound against L. amazonensis. Approximately 105L. amazonensis promastigotes were subcutaneously inoculated into the dermis of the right ear of BALB/c mice, which were subsequently treated with 2g (p.o. or i.p.), miltefosine (p.o.) or glucantime (i.p.) at 30 µmol/kg/day x 28 days. Thus, a similar reduction in the lesion size was observed after the administration of 2g through oral (63.7 ±â€¯10.1%) and intraperitoneal (61.8 ±â€¯3.7%) routes. A larger effect was observed after treatment with miltefosine (97.7 ±â€¯0.4%), and glucantime did not exhibit activity at the dose administered. With respect to the ear parasite load, 2g diminished the number of parasites by p.o. (30.5 ±â€¯5.1%) and i.p. (33.3 ±â€¯4.3%) administration. In addition, 2g induced in vitro apoptosis, autophagy and cell cycle alterations on L. amazonensis promastigotes. In summary, the derivative 2g might represent a lead candidate for antileishmanial drugs, as this compound displayed pronounced leishmanicidal activity.

Thiazole, thio and semicarbazone derivatives against tropical infective diseases: Chagas disease, human African trypanosomiasis (HAT), leishmaniasis, and malaria.

Thiazole, thiosemicarbazone and semicarbazone moieties are privileged scaffolds (acting as primary pharmacophores) in many compounds that are useful to treat several diseases, mainly tropical infectious diseases. In this review article, we critically analyzed the contribution of these scaffolds to medicinal chemistry in the last five years, focusing on tropical infectious diseases, such as Chagas disease, human African trypanosomiasis (HAT), leishmaniasis, and malaria. We also present perspectives for their use in drug design in order to contribute to the development of new drugs.

Design and development of novel p-aminobenzoic acid derivatives as potential cholinesterase inhibitors for the treatment of Alzheimer's disease.

Based on the quantitative structure-activity relationship (QSAR), some novel p-aminobenzoic acid derivatives as promising cholinesterase enzyme inhibitors were designed, synthesized, characterized and evaluated to enhance learning and memory. The in vitro enzyme kinetic study of the synthesized compounds revealed the type of inhibition on the respective acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes. The in vivo studies of the synthesized compounds exhibited significant reversal of cognitive deficits in the animal models of amnesia as compared to standard drug donepezil. Further, the ex vivo studies in the specific brain regions like the hippocampus, hypothalamus, and prefrontal cortex regions also exhibited AChE inhibition comparable to standard donepezil. The in silico molecular docking and dynamics simulations studies of the most potent compound 22 revealed the consensual interactions at the active site pocket of the AChE.

Thio- and Semicarbazones: Hope in the Search for Treatment of Leishmaniasis and Chagas Disease.

BACKGROUND: Trypanosomiasis and leishmaniasis cause severe infections in humans and domestic animals in the tropics. Although typical diseases in Latin America, globalization and the migration of infected people has spread these diseases to countries in North America, Asia and Europe. Currently available drugs are not effective in the chronic phase, as well as cause side effects and develop resistance. RESULTS: Among the chemical groups studied as potential anti-T. cruzi and anti-Leishmania are the thio-and semicarbazones, which are easy to obtain, possess structural versatility and can sequester metal. In this article, we present an overview of thio-and semicarbazones associated with heterocycles, indanones, and styryl and aryl skeletons, including their metal complexes with antimony, platinum, palladium, copper, ruthenium, rhenium, manganese and vanadium. CONCLUSION: Because of the efficiency and selectivity that some of these derivatives have shown, it can be concluded that thio-and semicarbazones constitute promising chemical scaffolds in the search for new anti-parasitic agents.

Recent Developments of Hydrazide/Hydrazone Derivatives and Their Analogs as Anticonvulsant Agents in Animal Models.

Preclinical Research Epilepsy is a chronic devastating neurological disorder characterized by synchronous interictal discharges. Treatment with antiepileptic drugs (AEDs) can alleviate spontaneous seizure activity without preventing the progression and development of epileptogenesis. Current design and development of new AEDs and strategies for the prevention of epilepsy is focused mainly on attenuating uncontrolled seizures, severe side effects and toxicity in chronic drug therapy. It has thus become necessary to discover new chemical pharmacophores with a broad spectrum of activity and less neurotoxicity. Hydrazide/hydrazone derivatives that possess a -CO-NHN=CH- group constitute an important class of compounds for drug development. This review highlights the specific characteristics of various hydrazide/hydrazone derivatives and structurally related semicarbazones, semicarbazides and Schiff base compounds and their anticonvulsant activities. It is focused on the influence of differently substituted pharmacophores developed through SAR studies and testing their activity against different pharmcological targets. Drug Dev Res 77 : 379-392, 2016. © 2016 Wiley Periodicals, Inc.

New approach towards the synthesis of selenosemicarbazones, useful compounds for Chagas' disease.

Herein, we describe a new approach towards the synthesis of selenosemicarbazones. The reaction involves an O-Se exchange of semicarbazones using Ishihara reagent. Eleven selenosemicarbazones were prepared using this methodology, with low to moderate yields. Among the prepared compounds the m-bromo phenyl methyl derivative 1b was selected to be evaluated in vivo, in a murine model of acute Chagas' disease. Compound 1b 10 mg/kg bw/day reduced 50% of parasitaemia profile compared with the control group, but was less effective than Benznidazole (50 mg/kg bw/day reduced 90%) and toxic. These studies are important to guide future Chagas drug design.

Psychomotor seizure test, neurotoxicity and in vitro neuroprotection assay of some semicarbazone analogues.

In continuance of our search for anticonvulsant agents, we reported herein the synthesis, characterization and anticonvulsant evaluation of some newer semicarbazone analogues. A few compounds were also screened for neuroprotection assay. Some of the compounds showed significant anticonvulsant activity. Compound 4a showed 25% (1/4, 0.25 h), 75% (3/4, 0.5 & 2.0 h) and 100% (4/4, 1.0 h) protection against 6 Hz psychomotor seizure test at 100 mg/kg devoid of any neurotoxicity. Compound 4d showed neuroprotection activity with 26.3 ± 2.3 percent of total propidium iodide uptake at 100 µM and IC50 of the compound was calculated using dose response curve by probit analysis and was found to be 149 ± 1.22 µM.

Semicarbazone analogs as anticonvulsant agents: a review.

Semicarbazones are synthesized by the condensation of semicarbazide and aldehyde/ketone. The literature survey revealed that semicarbazones had been emerged as compounds with diverse biological activities including anticonvulsant, antitubercular, anticancer, and antimicrobial activities. The anticonvulsant activity of semicarbazones is mainly attributed due to the presence of an aryl binding site with aryl/alkyl hydrophobic group, a hydrogen bonding domain and an electron donor group and they are suggested to act by inhibiting sodium ion (Na(+)) channel. Dimmock et al., reported an extensive series of semicarbazones and reported 4-(4-fluorophenoxy) benzaldehyde semicarbazone (C0102862, V102862) as lead molecule. In MES (oral) screening C0102862 showed protective index (PI > 315) more than carbamazepine (PI 101), phenytoin (PI > 21.6) and valproate (PI > 2.17). This review briefly describes the information available about semicarbazone analogs and their anticonvulsant activity.

Synthesis, evaluation and molecular dynamics study of some new 4-aminopyridine semicarbazones as an antiamnesic and cognition enhancing agents.

Some new semicarbazones of 4-aminopyridine were synthesized and evaluated for antiamnesic, cognition enhancing and anticholinesterase activities. The results illustrated a significant cognition enhancing effect on elevated plus maze model with a significant reversal of scopolamine-induced amnesia. A significant inhibition in acetycholinesterase (AChE) activity by all the synthesized compounds in specific brain regions that is, prefrontal cortex, hippocampus and hypothalamus was observed. Compound 4APi exhibited significant antiamnesic and cognition enhancing activity which was comparable with standard drug donepezil. Its enzyme kinetic study revealed a non-competitive inhibition of AChE and a competitive inhibition of butyrylcholinesterase (BChE). Docking studies predicted the binding modes of these compounds in AChE active site, which were further processed for molecular dynamics simulation for calculating binding free energies using Molecular Mechanics-Generalized Born Surface Area (MM/GBSA). All the computational study confirmed their consensual interaction with AChE justifying the experimental outcome.

Hepatoprotective effect of acetone semicarbazone on Ehrlich ascites carcinoma induced carcinogenesis in experimental mice.

OBJECTIVE: To determine the hepatoprotective effect of acetone semicarbazone (ASC) in vivo in normal and Ehrlich ascites carcinoma (EAC) bearing male Swiss albino mice. METHODS: Drug-induced changes in biochemical and behavioral parameters at dose of 2.0 mg/kg body weight for 14 d and nullifying the toxicity induced by EAC cells were studied. The histopathology studies of the protective effects of ASC on vital organs were also assessed. RESULTS: The administration of ASC made insignificant changes in body weight and behavioral (salivation, diarrhea, muscular numbness) changes during treatment period due to minor toxicity were minimized after the treatment in normal mice. The biochemical parameters, including serum glutamate pyruvate transaminase, glutamate oxaloactate transaminase, alkaline phosphatase, serum glucose, cholesterol, urea, triglyceride and billirubin changed modestly in normal mice receiving ASC. Though the treatment continued, these values gradually decreased to normal level after the treatment. In EAC bearing mice, the toxic effects due to EAC cells in all cases were nullified by treatment with the ASC. Significant abnormalities were not detected in histology of the various organs of the normal mice treated with ASC. CONCLUSIONS: ASC can, therefore, be considered safe in formulating novel anticancer drug, as it exhibits strong protective effect against EAC cell bearing mice.

Semicarbazone--a versatile therapeutic pharmacophore for fragment based anticonvulsant drug design.

During the last fifteen years, semicarbazones have been extensively investigated for their anticonvulsant properties. 4-(4-Flurophenoxy) benzaldehyde semicarbazone (C0102862, V102862) was discovered as a lead molecule and is being developed as a potent antiepileptic drug, with maximal electroshock (MES) ED50 of i.p. 12.9 mg kg⁻¹. In MES (oral screen), this compound has a protective index (PI = TD50/ED50 > 315) higher than carbamazepine (PI 101), phenytoin (PI > 21.6) and valproate (PI 2.17). The compound is a potent sodium channel blocker. Other semicarbazones have demonstrated activity in various chemoshock screens, like subcutaneous pentylenetetrazole, subcutaneous strychnine, subcutaneous picrotoxin and subcutaneous bicculine. Semicarbazones are also GABA-transaminase inhibitors. Extensive structure- -activity relationship has demonstrated that F, Cl, Br and NO2 substituents in the arylhydrophobic pocket and a hydrogen bonding domain (HBD) are generally found in active anticonvulsant agents.

A novel series of 2,5-disubstituted 1,3,4-oxadiazoles: synthesis and SAR study for their anticonvulsant activity.

In search for a better anticonvulsant drug and the importance of semicarbazones and 2,5-disubstituted 1,3,4-oxadiazoles as anticonvulsant pharmacophore, a series of novel substituted semicarbazones were designed, synthesized, and evaluated for their anticonvulsant activity. The chemical structures of the synthesized molecules were confirmed by elemental and spectral (IR, (1) H NMR, (13) C NMR and MS) analysis. The anticonvulsant activities of the compounds were investigated using maximal electroshock seizure and subcutaneous pentylenetetrazole (scPTZ) models. Efforts were also made to establish structure-activity relationships among synthesized compounds. The results of the present study validated that the pharmacophore model with four binding sites is essential for anticonvulsant activity.

SC68896, a novel small molecule proteasome inhibitor, exerts antiglioma activity in vitro and in vivo.

PURPOSE: Glioblastomas are among the most lethal neoplasms, with a median survival of <1 year. Modulation of the proteasome function has emerged as a novel approach to cancer pharmacotherapy. Here, we characterized the antitumor properties of SC68896, a novel small molecule proteasome inhibitor. EXPERIMENTAL DESIGN: Different tumor cell lines were tested by crystal violet staining for sensitivity to SC68896, given alone or in combination with death ligands. The molecular mechanisms mediating SC68896-induced cell death and changes in cell cycle progression were assessed by immunoblot and flow cytometry. An orthotopic human glioma xenograft model in nude mice was used to examine the in vivo activity of SC68896. RESULTS: SC68896 inhibits the proliferation of cell lines of different types of cancer, including malignant glioma. Exposure of LNT-229 glioma cells to SC68896 results in a concentration- and time-dependent inhibition of the proteasome, with a consequent accumulation of p21 and p27 proteins, cell cycle arrest, caspase cleavage, and induction of apoptosis. Using RNA interference, we show that the effect of SC68896 on glioma cells is facilitated by wild-type p53. SC68896 sensitizes glioma cells to tumor necrosis factor-related apoptosis-inducing ligand and CD95 ligand and up-regulates the cell surface expression of the tumor necrosis factor-related apoptosis-inducing ligand receptor cell death receptors 4 and 5, which may contribute to this sensitization. Intracerebral glioma-bearing nude mice treated either i.p. or intratumorally with SC68896 experience prolonged survival. CONCLUSIONS: SC68896 is the first proteasome inhibitor that exerts antiglioma activity in vivo. It may represent a novel prototype agent for the treatment of malignant gliomas and warrants clinical evaluation.

The peptide-semicarbazone S-2209, a representative of a new class of proteasome inhibitors, induces apoptosis and cell growth arrest in multiple myeloma cells.

Bortezomib is the first approved member of a new class of anti-myeloma agents, the proteasome inhibitors. Further proteasome inhibitors are needed to optimise this promising treatment option. S-2209 [1-[1-{1-[(2,4-Dioxo-imidazolidin-1-ylimino)-methyl]-2-phenyl-ethylcarbamoyl}-2-(1H-indol-3-yl)-ethylcarbamoyl]-2-(1H-indol)] inhibits the chymotryptic activity of the human 20S proteasome (half maximal effective concentration, IC(50) approximately 220 nmol/l) which was determined by a proteasome inhibition assay. A nuclear factor kappaB inhibition assay revealed a half maximal effective concentration (EC(50)) of 0.9 micromol/l. The WST-1 growth assay showed inhibition of cell growth of all tested multiple myeloma (MM) cell lines with an IC(50) between 100 nmol/l and 600 nmol/l. Strong induction of apoptosis was seen in MM cells at nanomolar concentrations (IC(50) approximately 300 nm) as well as in primary myeloma cells. No induction of apoptosis was detected in peripheral blood mononuclear cells from healthy humans. Upregulation of p53, activation of JNK protein, and downregulation of Mcl-1 was revealed. Despite the administration of 15 mg S-2209/kg/d in wistar rats, no toxicity with respect to body weight, hepatic enzymes, creatinine or haemoglobin was seen. Proteasome inhibition in white blood cells isolated from the treated rats was higher in the S-2209 treated animals in comparison with the control animals treated with 0.1 mg/kg/d bortezomib. S-2209 is active in myeloma cells and shows a favourable toxicity profile in first in-vivo studies. S-2209 is a promising agent for further clinical development.

Comparative efficacy of imidacloprid, selamectin, fipronil-(S)-methoprene, and metaflumizone against cats experimentally infested with Ctenocephalides felis.

Four active ingredients--imidacloprid selamectin, fipronil-(S)-methoprene, and metaflumizone--were tested to assess the speed of flea kill against existing flea infestations and subsequent reinfestations. Thirty flea-infested cats were allocated to four treatment groups and one untreated control group. Flea counts were performed 6, 18, and 48 hours after treatment (day 0) and 2, 4, and 24 hours after weekly flea reinfestations. Cats were also reinfested with fleas after the 6- and 18-hour counts on day 0 and after the 2- and 4-hour counts on subsequent count days. Imidacloprid provided significantly greater flea kill at diverse time points. At the 24-hour counts, all compounds showed expected and similar high efficacies. On study day 34, imidacloprid showed the highest efficacy at 24 hours after reinfestation, with 90.8% flea reduction compared with 55.7% to 67.4% in the other treatment groups. A single topical application of imidacloprid provided a high efficacy in the early elimination of adult fleas, limiting the risk of pathogen transmission and flea allergy dermatitis.

A comparative evaluation of the speed of kill and duration of efficacy against weekly infestations with fleas on cats treated with fipronil-(S)-methoprene or metaflumizone.

Spot-on formulations of metaflumizone and a combination of fipronil-(S)-methoprene were evaluated in adult cats to determine the duration of 24- and 48-hour efficacy and short-term speed of kill against adult cat fleas, Ctenocephalides felis felis. Speed of kill efficacies (at 12, 18, 24, and 48 hours) were assessed against existing (day -1) infestations and against infestations at day 7, and efficacy was assessed 24 and 48 hours after weekly flea infestations through day 42. Cats treated with fipronil-(S)-methoprene had significantly (P<.01) fewer fleas than those treated with metaflumizone at 12 and 18 hours after treatment (day 0) and on the day 7 infestations. Fipronil-(S)-methoprene-treated cats also had significantly (P<.05) fewer fleas than metaflumizone-treated cats for all 24-hour counts from initial treatment on day 0 through infestation day 42 and for the 48-hour counts on day 28 through day 42.

Synthesis and antimalarial activity of semicarbazone and thiosemicarbazone derivatives.

Seventeen semicarbazone and thiosemicarbazone derivatives were prepared and tested in vitro against a chloroquine resistant strain of Plasmodium falciparum (W2) to evaluate their antiplasmodial potential. Three thiosemicarbazones were found to be active against the parasite and non-toxic to human peripheral blood mononuclear cells (PBMC). Among these, compound 5b presented the lowest IC50 value against P. falciparum (7.2 microM) and was the least toxic in the PBMC proliferation assay (IC50=73.5 microM). It was selected for in vivo tests on mice infected with Plasmodium berghei (strain NK-65). The thiosemicarbazone 5b was able to reduce the parasitaemia by 61% at 20 mg/kg on day 7 after infection without any sign of toxicity to the animals. In comparison, the standard drug chloroquine at 15 mg/kg showed a reduction around 95%. These in vitro and in vivo results make 5b an interesting lead for further development.

Efficacy of a topically applied spot-on formulation of a novel insecticide, metaflumizone, applied to cats against a flea strain (KS1) with documented reduced susceptibility to various insecticides.

A spot-on metaflumizone formulation was evaluated in adult domestic short hair cats to determine its adultidical efficacy against a flea strain that has reduced susceptibility to a number of insecticides. Eight cats served as non-treated controls, eight cats were treated with a metaflumizone formulation at 0.2 ml/kg (40 mg metaflumizone/kg) and eight cats were treated with fipronil 10% w/v-(s)-methoprene 12%w/v at 0.075 ml/kg (7.5-7.7 mg fipronil/kg:9.0-9.2 mg (s)-methoprene/kg). On days -1, 7, 14, 21, 28, 35, and 42 each cat was infested with approximately 100 unfed KS1 cat fleas, Ctenocephalides felis. At approximately 48 h after treatment or infestation, each cat was combed to remove and count live fleas. Treatment with metaflumizone provided > or = 99.3% efficacy for 3 weeks post-treatment and then 97.4, 91.4 and 86.2% efficacy at 4, 5 and 6 weeks post-treatment, respectively. Fipronil-(s)-methoprene provided 99.6% efficacy at 1 week post-treatment and then 97.6, 96.4, 71.3, 22.0 and 13.1% efficacy at weeks 2, 3, 4, 5 and 6, respectively. The reductions in flea numbers were significantly greater for the metaflumizone treatment than for fipronil-(s)-methoprene from 3 to 6 weeks after treatment.

Safety of a topically applied metaflumizone spot-on formulation for flea control in cats and kittens.

Four laboratory studies were conducted in cats of various ages to evaluate the safety of a novel low-volume topical spot-on containing 20% metaflumizone (ProMeris for Cats, Fort Dodge Animal Health, Overland Park, KS) when used in cats according to the recommended minimum dosage of 40mg metaflumizonekg(-1) delivered via fixed volume doses of 0.8ml for cats 4.0kg. Study parameters included body weight, food consumption, clinical, physical and neurological examinations, and clinical pathology including complete hematology, coagulation, clinical chemistry and urinalysis. Exaggerated and repeated topical applications of metaflumizone at 1x, 3x and 5x the proposed recommended dose in adult cats and kittens 8 weeks of age had no effect on mortality, body weight, food consumption, clinical, physical or neurological examinations, or clinical pathology parameters. Transient salivation was sporadically noted following some, but not all treatment applications. It occurred and resolved within minutes of treatment application in all groups, including cats treated with placebo. Consequently, it was not considered a direct result of treatment with the active ingredient, metaflumizone. Cats orally administered 10% of the recommended topical dose exhibited considerable avoidance behaviors including spitting, head shaking, and salivation. Therefore, voluntary oral exposure is unlikely. No other adverse signs were observed. Repeated use of metaflumizone caused no adverse health effects when administered at 5x the recommended dose and is safe when used as directed, even on kittens as young as 8 weeks of age.