Synthesis, Pharmacological Evaluation, and Molecular Modeling of Lappaconitine-1,5-Benzodiazepine Hybrids.

Diterpenoid alkaloids, originating from the amination of natural tetracyclic diterpenes, have long interested scientists due to their medicinal uses and infamous toxicity which has limited the clinical application of the native compound. Alkaloid lappaconitine extracted from various Aconitum and Delphinium species has displayed extensive bioactivities and active ongoing research to reduce its adverse effects. A convenient route to construct hybrid molecules containing diterpenoid alkaloid lappaconitine and 3H-1,5-benzodiazepine fragments was proposed. The key stage involved the formation of 5'-alkynone-lappaconitines in situ by acyl Sonogashira coupling of 5'-ethynyllappaconitine, followed by cyclocondensation with o-phenylenediamine. New hybrid compounds showed low toxicity and outstanding analgesic activity in experimental pain models, which depended on the nature of the substituent in the benzodiazepine nucleus. An analogous dependence was also shown for the antiarrhythmic activity in the epinephrine arrhythmia test in vivo. Studies on the isolated atrium have shown that the mechanism of action of the new compounds is included the blockade of beta-adrenergic receptors and potassium channels. Molecular docking analysis was conducted to determine the binding potential of target molecules with the voltage-gated sodium channel NaV1.5. All obtained results provide a basis for future rational modifications of lappaconitine, reducing side effects, while retaining its therapeutic effects.

Pharmacodynamic and pharmacokinetic profiles of a neurotensin receptor type 2 (NTS2) analgesic macrocyclic analog.

The current opioid crisis highlights the urgent need to develop safe and effective pain medications. Thus, neurotensin (NT) compounds represent a promising approach, as the antinociceptive effects of NT are mediated by activation of the two G protein-coupled receptor subtypes (i.e., NTS1 and NTS2) and produce potent opioid-independent analgesia. Here, we describe the synthesis and pharmacodynamic and pharmacokinetic properties of the first constrained NTS2 macrocyclic NT(8-13) analog. The Tyr11 residue of NT(8-13) was replaced with a Trp residue to achieve NTS2 selectivity, and a rationally designed side-chain to side-chain macrocyclization reaction was applied between Lys8 and Trp11 to constrain the peptide in an active binding conformation and limit its recognition by proteolytic enzymes. The resulting macrocyclic peptide, CR-01-64, exhibited high-affinity for NTS2 (Ki 7.0 nM), with a more than 125-fold selectivity over NTS1, as well as an improved plasma stability profile (t1/2 > 24 h) compared with NT (t1/2 ~ 2 min). Following intrathecal administration, CR-01-64 exerted dose-dependent and long-lasting analgesic effects in acute (ED50 = 4.6 µg/kg) and tonic (ED50 = 7.1 µg/kg) pain models as well as strong mechanical anti-allodynic effects in the CFA-induced chronic inflammatory pain model. Of particular importance, this constrained NTS2 analog exerted potent nonopioid antinociceptive effects and potentiated opioid-induced analgesia when combined with morphine. At high doses, CR-01-64 did not cause hypothermia or ileum relaxation, although it did induce mild and short-term hypotension, all of which are physiological effects associated with NTS1 activation. Overall, these results demonstrate the strong therapeutic potential of NTS2-selective analogs for the management of pain.

The Effect of Process Variables and Binder Concentration on Tabletability of Metformin Hydrochloride and Acetaminophen Granules Produced by Twin Screw Melt Granulation with Different Polymeric Binders.

In twin screw melt granulation, granules are produced by passing mixtures of drug substances and polymeric binders through twin screw extruder such that temperatures are maintained below melting point of drugs but above glass transition of polymers used, whereby the polymers coat surfaces of drug particles and cause their agglomeration into granules. Since various formulation factors, such as binder type and concentration, and processing variables like extrusion temperature, screw configuration, and screw speed, can influence the granulation process, the present investigation was undertaken to study their effects on tabletability of granules produced. Three different types of polymeric binders, Klucel® EXF (hydroxypropyl cellulose), Eudragit® EPO (polyacrylate binder), and Soluplus® (polyvinyl caprolactam-co-vinyl acetate-ethylene glycol graft polymer), were used at 2, 5, and 10% concentrations. Metformin hydrochloride (HCl) (mp: 222°C) and acetaminophen (mp: 169°C) were used as model drugs, and drug-polymer mixtures with metformin HCl were extruded at 180, 160, and 130°C, while those with acetaminophen were extruded at 130 and 110°C. Other process variables included screw configurations: low, medium, and high shear for metformin HCl, and low and medium shear for acetaminophen; feed rates: 20 and 60 g/min; and screw speed of 100 and 300 RPM. Formulation and process variables had significant impact on tabletability. The target tensile strength of ≥2 MPa could be obtained with all polymers and at all processing temperatures when metformin HCl was granulated at 180°C and acetaminophen at 130°C. At other temperatures, the target tensile strength could be achieved at certain specific sets of processing conditions.

Six-Step Total Synthesis of (±)-Conolidine.

A concise total synthesis of (±)-conolidine, a potent nonopioid analgesic, in 19% overall yield is described here. A gold(I)-catalyzed Conia-ene reaction (Toste cyclization) and a Pictet-Spengler reaction served as key transformations for assembling the 1-azabicyclo[4.2.2]decane core and defining the geometry of the exocyclic double bond. The activation energies of formation of the vinyl-gold intermediates were calculated and revealed a silyl enol ether with an unprotected indole moiety as a suitable precursor for the Toste cyclization. This six-step synthesis did not involve any nonstrategic redox manipulations.

Study of Anti-inflammatory Activity of a New Non-opioid Analgesic on the Basis of a Selective Inhibitor of TRPA1 Ion Channels.

INTRODUCTION: Nowadays, the group of NSAIDs is used the most widely in order to treat the inflammatory process. But its long-term administration increases the risk of complications of pharmacotherapy. Therefore, today it is urgent to search for new molecules that can selectively block biological targets that directly perceive inflammatory mediators. One of such targets is TRPA1. ZC02-0012, a compound from the group of substituted pyrazinopyrimidinones, which is a selective inhibitor of TRPA1 ion channel. OBJECTIVE: The aim of our study was to study the anti-inflammatory activity of an innovative molecule under the laboratory code ZC02-0012 from the group of selective inhibitors of TRPA1 ion channel. MATERIALS AND METHODS: Anti-inflammatory activity of ZC02-0012 was studied on the model of acute exudative inflammation of the paw in response to subplantar injection in the right hind paw of mice with 0.02 ml of 2% formaldehyde solution. The mass of the paw was measured after 4 hours (peak edema) after phlogistic injection. The test substance and the reference drug was administered intragastrically or intramuscularly 45 minutes before the injection of formaldehyde solution. The presence and intensity of antiinflammatory activity was judged by the inhibitory effect, represented in percent. RESULTS AND DISCUSSION: Selective inhibitor of the TRPA1 ion channel ZC02-0012 revealed the anti-inflammatory activity at doses of 3 and 9 mg/kg, its intensity is comparable to diclofenac sodium. CONCLUSION: The selective inhibitor of the ion channel TRPA1, a substance under code ZC02-0012, has an anti-inflammatory activity comparable with diclofenac sodium.

Development of Theranostic Perfluorocarbon Nanoemulsions as a Model Non-Opioid Pain Nanomedicine Using a Quality by Design (QbD) Approach.

Pain nanomedicine is an emerging field in response to current needs of addressing the opioid crisis in the USA and around the world. Our group has focused on the development of macrophage-targeted perfluorocarbon nanoemulsions as inflammatory pain nanomedicines over the past several years. We present here, for the first time, a quality by design approach used to design pain nanomedicine. Specifically, we used failure mode, effects, and criticality analysis (FMECA) which identified the process and composition parameters that were most likely to impact nanoemulsion critical quality attributes (CQAs). From here, we applied a unique combination approach that compared multiple linear regression, boosted decision tree regression, and partial least squares regression methods in combination with correlation plots. The presented combination approach allowed for in-depth analyses of which formulation steps in the nanoemulsification processes control nanoemulsion droplet diameter, stability, and drug loading. We identified that increase in solubilizer (transcutol) content increased drug loading and decreased nanoemulsion stability. This was mitigated by inclusion of perfluorocarbon oil in the internal phase. We observed negative correlation (R2 = 0.4357, p value 0.0054) between the amount of PCE and the percent diameter increase (destabilization), and no correlation between processing parameters and percent diameter increase over time. Further, we identified that increased sonication time decreases nanoemulsion drug loading but does not significantly impact droplet diameter or stability. We believe the methods presented here can be useful in the development of various nanomedicines to produce higher-quality products with enhanced manufacturing and design control.

Synthesis of Some Novel 2,6-Disubstituted Pyridazin-3(2H)-one Derivatives as Analgesic, Anti-Inflammatory, and Non-Ulcerogenic Agents.

Some novel 2,6-disubstituted pyridazine-3(2H)-one derivatives were synthesized and evaluated for in vitro cyclooxygenase-2 (COX-2) inhibitory efficacy. Compounds 2-{[3-(2-methylphenoxy)-6-oxopyridazin-1(6H)-yl]methyl}-1H-isoindole-1,3(2H)-dione (5a), 2-propyl-6-(o-tolyloxy)pyridazin-3(2H)-one (6a), and 2-benzyl-6-(3,5-dimethyl-1H-pyrazol-1-yl)pyridazin-3(2H)-one (16a) showed the most potent COX-2 inhibitory activity with IC50 values of 0.19, 0.11, and 0.24 µM, respectively. The synthesized compounds with the highest COX-2 selectivity indices were evaluated for their anti-inflammatory, analgesic, and ulcerogenic activities. Compounds 6a and 16a demonstrated the most potent and consistent anti-inflammatory activity over the synthesized compounds, which was significantly higher than that of celecoxib in the carrageenin rat paw edema model and with milder ulcer scoring than that of indomethacin in the ulcerogenicity screening.

Discovery of Potent Antiallodynic Agents for Neuropathic Pain Targeting P2X3 Receptors.

Antagonism of the P2X3 receptor is one of the potential therapeutic strategies for the management of neuropathic pain because P2X3 receptors are predominantly localized on small to medium diameter C- and Aδ-fiber primary afferent neurons, which are related to the pain-sensing system. In this study, 5-hydroxy pyridine derivatives were designed, synthesized, and evaluated for their in vitro biological activities by two-electrode voltage clamp assay at hP2X3 receptors. Among the novel hP2X3 receptor antagonists, intrathecal treatment of compound 29 showed parallel efficacy with pregabalin (calcium channel modulator) and higher efficacy than AF353 (P2X3 receptor antagonist) in the evaluation of its antiallodynic effects in spinal nerve ligation rats. However, because compound 29 was inactive by intraperitoneal administration in neuropathic pain animal models due to low cell permeability, the corresponding methyl ester analogue, 28, which could be converted to compound 29 in vivo, was investigated as a prodrug concept. Intravenous injection of compound 28 resulted in potent antiallodynic effects, with ED50 values of 2.62 and 2.93 mg/kg in spinal nerve ligation and chemotherapy-induced peripheral neuropathy rats, respectively, indicating that new drug development targeting the P2X3 receptor could be promising for neuropathic pain, a disease with high unmet medical needs.

Discovery of Stable Non-opioid Dynorphin A Analogues Interacting at the Bradykinin Receptors for the Treatment of Neuropathic Pain.

Dynorphin A (Dyn A) is a unique endogenous ligand that possesses well-known neuroinhibitory effects via opioid receptors with a preference for the kappa receptor but also neuroexcitatory effects, which cause hyperalgesia. We have shown that the neuroexcitatory effects are mediated through bradykinin (BK) receptors and that intrathecal (i.th.) administration of our lead ligand 1, [des-Arg7]-Dyn A-(4-11), which shows good binding affinity (IC50 = 150 nM) at the BK receptors, blocks Dyn A-induced hyperalgesia in naïve animals and reverses thermal and tactile hypersensitivities in a dose-dependent manner in nerve-injured animals. However, 1 has a serious drawback as a potential drug candidate for the treatment of neuropathic pain because of its susceptibility to enzymatic degradation. In an effort to increase its stability, we modified ligand 1 using non-natural amino acids and found that analogues substituted at or near the N-terminus with a d-isomer retain binding at the receptor and provide a large increase in stability. In particular when Leu5 was modified, with either the d-isomer or N-methylation, there was a large increase in stability (t1/2 = 0.7-160 h in rat plasma) observed. From these studies, we have developed a very stable Dyn A analogue 16, [d-Leu5,des-Arg7]-Dyn A-(4-11), that binds to BK receptors (IC50 = 130 nM) in the same range as ligand 1 and shows good antihyperalgesic effects in both naïve rats and L5/L6 spinal nerve ligation rats.

Synthesis and Pharmacological Evaluation of Novel 1-(1,4-Alkylaryldisubstituted-4,5-dihydro-1H-imidazo)-3-substituted Urea Derivatives.

Novel 1-(1,4-alkylaryldisubstituted-4,5-dihydro-1H-imidazo)-3-substituted urea derivatives have been synthesized and evaluated for their central nervous system activity. Compounds 3a-m were prepared in the reaction between the respective 1-alkyl-4-aryl-4,5-dihydro-1H-imidazol-2-amines 1a-c and appropriate isocyanates 2 in dichloromethane. The compounds were subjected to in silico ADMET studies in order to select best candidates for in vivo experiments. The effects of the compounds on the spontaneous locomotor activity and amphetamine-evoked hyperactivity were estimated. Analgesic activity, without or in the presence of naloxone, was assessed in the writhing test. The tendency to change the HTR, evoked by l-5-HTP and the involvement in alteration in body temperature in mice was studied. Additionally, to check possible occurrence of drug-induced changes in the muscle relaxant activity of mice, which may have contributed to their behaviour in other tests, the rota-rod and chimney tests were performed. The new urea derivatives exerted significant activities in the performed pharmacological tests, although the presented results show a preliminary estimation, and thus, need to be extended for identification and understanding the complete pharmacological profile of the examined compounds.

Synthesis, antioxidant and analgesic activities of Schiff bases of 4-amino-1,2,4-triazole derivatives containing a pyrazole moiety.

A series of Schiff bases of 4-amino-1,2,4-triazole derivatives containing pyrazole (5a-h) were synthesized from condensation of 4-amino-5-(5-methyl-1H-pyrazol-3-yl)-4H-1,2,4-triazole-3-thiol (3) derivative with various aromatic aldehydes (4a-h). The structures of the synthesized compounds were elucidated by IR, 1H NMR, 13C NMR, and mass spectrometry. All the synthesized compounds (5a-h) were screened for their in vivo analgesic and in vitro antioxidant activities revealing significant analgesic and antioxidant properties.

Synthesis and Biological Evaluation of Novel σ1 Receptor Ligands for Treating Neuropathic Pain: 6-Hydroxypyridazinones.

By use of the 6-hydroxypyridazinone framework, a new series of potent σ1 receptor ligands associated with pharmacological antineuropathic pain activity was synthesized and is described in this article. In vitro receptor binding studies revealed high σ1 receptor affinity (Ki σ1 = 1.4 nM) and excellent selectivity over not only σ2 receptor (1366-fold) but also other CNS targets (adrenergic, µ-opioid, sertonerigic receptors, etc.) for 2-(3,4-dichlorophenyl)-6-(3-(piperidin-1-yl)propoxy)pyridazin-3(2H)-one (compound 54). Compound 54 exhibited dose-dependent antiallodynic properties in mouse formalin model and rats chronic constriction injury (CCI) model of neuropathic pain. In addition, functional activity of compound 54 was evaluated using phenytoin and indicated that the compound was a σ1 receptor antagonist. Moreover, no motor impairments were found in rotarod tests at antiallodynic doses and no sedative side effect was evident in locomotor activity tests. Last but not least, good safety and favorable pharmacokinetic properties were also noted. These profiles suggest that compound 54 may be a member of a novel class of candidate drugs for treatment of neuropathic pain.

Inhibition of N-type calcium channels by fluorophenoxyanilide derivatives.

A set of fluorophenoxyanilides, designed to be simplified analogues of previously reported ω-conotoxin GVIA mimetics, were prepared and tested for N-type calcium channel inhibition in a SH-SY5Y neuroblastoma FLIPR assay. N-type or Cav2.2 channel is a validated target for the treatment of refractory chronic pain. Despite being significantly less complex than the originally designed mimetics, up to a seven-fold improvement in activity was observed.

P2X7 receptor-mediated analgesia in cancer-induced bone pain.

Pain is a common and debilitating complication for cancer patients significantly compromising their quality of life. Cancer-induced bone pain involves a complex interplay of molecular events, including mechanisms observed in inflammatory and neuropathic pain states, but also changes unique for cancer-induced bone pain. The P2X7 receptor (P2X7R) is involved in a variety of cellular functions and has been linked to both inflammatory and neuropathic pain. Here we study the analgesic potential of P2X7R antagonism in a rat model of cancer-induced bone pain. In cancer-bearing animals, the P2X7R antagonist A839977 attenuated dorsal horn neuronal responses in a modality and intensity-specific way. Spinal application of 0.4-mg/kg and 1.2-mg/kg A839977 significantly reduced the evoked responses to high-intensity mechanical and thermal stimulation, whereas no effect was seen in response to low-intensity or electrical stimulation. In contrast, A839977 had no effect on the tested parameters in naïve or sham animals. In awake animals, 40-mg/kg A839977 (i.p.) significantly reduced both early- and late-stage pain behavior. In contrast, no effect was observed in sham or vehicle-treated animals. The results suggest that the P2X7R is involved in the mechanisms of cancer-induced bone pain, and that P2X7R antagonism might be a useful analgesic target. No effect was observed in sham or naïve animals, indicating that the P2X7R-mediated effect is state-dependent, and might therefore be an advantageous target compared to traditional analgesics.

Analgesic activity of new 8-methoxy-1,3-dimethyl-2,6-dioxo-purin-7-yl derivatives with carboxylic, ester or amide moieties.

BACKGROUND: The previous studies in a group of 4-arylpiperazinylalkyl derivatives of purine-2,6-dione and several other heterocyclic systems revealed their analgesic properties. In an effort to establish new analgesic agents we designed and synthesized a series of new 8-methoxy-1,3-dimethyl-2,6-dioxo-purin-7-yl derivatives with terminal carboxylic, ester or amide moieties. METHODS: The obtained compounds were evaluated pharmacologically in two in vivo models: the writhing syndrome and the formalin tests. The influence of the investigated compounds on the phosphodiesterase (PDE) activity was also determined. RESULTS: Majority of the tested compounds showed significant analgesic activity. The strongest analgesic and anti-inflammatory effect were observed for benzylamide (10) and 4-phenylpiperazinamide (11-14) derivatives which were more active than acetylic acid used as a reference drug (up to 23 and 36 fold increase in activity in writhing and formalin test, respectively). Several active compounds stronger than theophylline inhibited the phosphodiesterase activity. CONCLUSION: The present study revealed that the presented compounds are new class of analgesic and anti-inflammatory agents and are worthy of the further evaluation regarding to their pharmacological properties.

HYP-1, a novel diamide compound, relieves inflammatory and neuropathic pain in rats.

In the present study, we investigated whether a novel compound, 2-(2-(4-((4-chlorophenyl)(phenyl)methyl) piperazin-1-yl)-2-oxoethylamino)-N-(3,4,5-trimethoxybenzyl)acetamide (HYP-1), is capable of binding to voltage-gated sodium channels (VGSCs) and evaluated both its inhibitory effect on Na+ currents of the rat dorsal root ganglia (DRG) sensory neuron and its in vivo analgesic activity using rat models of inflammatory and neuropathic pain. HYP-1 showed not only high affinity for rat sodium channel (site 2), but also potent inhibitory activity against the TTX-R Na+ currents of the rat DRG sensory neuron. HYP-1 co-injected with formalin (5%, 50 µl) under the plantar surface of rat hind paw dose-dependently reduced spontaneous pain behaviors during both the early and late phases. This result was confirmed by c-Fos immunofluorescence in the L4-5 spinal segments. A large number of c-Fos-positive neurons were observed in rat injected with a mixture of formalin and vehicle, but not in rat treated with a mixture of formalin and HYP-1. In addition, the effectiveness of HYP-1 (6 and 60 mg/kg, i.p.) in suppression of neuropathic pain, such as mechanical, cold and warm allodynia, induced by rat tail nerve injury was investigated. HYP-1 showed limited selectivity over hERG, N-type and T-type channels.Our present results indicate that HYP-1, as a VGSC blocker, has potential analgesic activities against nociceptive, inflammatory and neuropathic pain.

[Synthesis and analgesic activities of phenyl piperazinyl aralkyl ketone derivatives].

To explore novel non-opioid analgesic agents, 16 compounds were synthesized and their structures were confirmed by 1H NMR and HR-MS. YX0611-1 was treated as the leading compound. The results of mice writhing model and hot plate model showed that compounds 2, 7, 8, 9, 11 and 15 had obvious analgesic activities in vivo. The test of affinity to mu, delta, kappa receptor displayed that active compounds didn't act on opioid receptor. The results of preliminary toxicity and pharmacokinetic tests showed that compound 7 had better safety and pharmacokinetic properties than that of YX0611-1, and it deserved further development.

Synthesis and determination of acute and chronic pain activities of 1-[1-(4-methylphenyl) (cyclohexyl)] morpholine as a new phencyclidine derivative in rats.

Phencyclidine (1-(1-phenylcyclohexyl)piperidine, CAS 77-10-1, PCP, I) and many of its analogues have been synthesized and their pharmacological properties studied. In this research, new methyl morpholine derivative of phencyclidine (1-[1-(4-methylphenyl) (cyclohexyl)]morpholine, Methyl-PCM, III) was synthesized and the acute and chronic pain activities were studied using tail immersion and formalin tests on rats and compared to PCP and PCM (1-(1-phenylcyclohexyl)morpholine, CAS 2201-40-3, PCP-morpholine, II). The results Indicated that Methyl-PCM (III, 6 mg/kg, i.p) produces more analgesic effects in tail immersion test (as a model of acute thermal pain) in comparison with the PCP, PCM and control groups. Meanwhile, this analgesic effect was markedly shown 5-15 min after the compound III application. In formalin test analysis, the acute pain (phase I) could not be affected by any drugs, but the chronic formalin pain (phase II) could be diminished by PCM and especially compound III. The chronic analgesic effect of Methyl-PCM was markedly shown in the late phase of chronic pain.

Orally bioavailable imidazoazepanes as calcitonin gene-related peptide (CGRP) receptor antagonists: discovery of MK-2918.

In our ongoing efforts to develop CGRP receptor antagonists for the treatment of migraine, we aimed to improve upon telecagepant by targeting a compound with a lower projected clinical dose. Imidazoazepanes were identified as potent caprolactam replacements and SAR of the imidazole yielded the tertiary methyl ether as an optimal substituent for potency and hERG selectivity. Combination with the azabenzoxazinone spiropiperidine ultimately led to preclinical candidate 30 (MK-2918).