David K.H. Lee

A back translation of pregabalin and carbamazepine against evoked and non-evoked endpoints in the rat spared nerve injury model of neuropathic pain.

The purpose of the present study was twofold. First to characterize endpoints distinct to the reflexive responses to sensory stimuli typically used in neuropathic pain models. A second aim was to evaluate two clinically approved drugs carbamazepine (Tegretol) and pregabalin (Lyrica) against these endpoints with the purpose to backtranslate from the clinical to preclinical setting. The selected neuropathic pain model was the spared nerve injury (SNI) model and the endpoints were burrowing and measures of paw posture in Sprague Dawley rats. As previously described, SNI surgery produced a robust heightened sensitivity to tactile and thermal (cold) stimuli. SNI surgery also produced robust decreases in burrowing and affected multiple measures of paw position. There was no correlation between magnitude of change in burrowing and sensory allodynia within SNI operated rats. Pregabalin (10-30 mg/kg IP) produced a reliable reversal of both tactile and cold allodynia and also the burrowing deficit, with minimal effect on neurological function evaluated using rotorod, beam walking and open field activity. Pregabalin did not affect any measure of paw position. Pharmacokinetic studies conducted in satellite animals identified plasma levels of pregabalin at the 10 mg/kg IP dose to be equivalent to clinically efficacious levels recorded in neuropathic patients (3-6 μg/ml). In contrast carbamazepine (10-60 mg/kg IP) had only a very modest effect against a reflexive (tactile) measure, and no effect against the burrowing deficit. Carbamazepine also affected various measures of neurological function, complicating interpretation of the reflexive measure. Measurement of burrowing appears to detect a behavioural deficit associated with the SNI model, that may be attenuated by pregabalin but not carbamazepine. Overall the present findings support an advantage of pregabalin over carbamazepine in terms of both efficacy and tolerability which is consistent with clinical experience. The inclusion of additional endpoints beyond traditional reflexive behaviours further supports the value of rodent neuropathic pain models, such as the SNI, as behavioural assays to detect new chemical entities to treat this pain condition.

Pyrrolo[3,2,1-ij]quinoline derivatives, a 5-HT2c receptor agonist with selectivity over the 5-HT2a receptor: potential therapeutic applications for epilepsy and obesity.

A series of pyrrolo[3,2,1-ij]quinoline derivatives was synthesized, evaluated for their activity against the 5-HT2c and 5-HT2a, receptors and found to be agonists at 5-HT2c with selectivity over 5-HT2a.

Design, synthesis, and biological evaluation of 3,4-dihydroquinolin-2(1H)-one and 1,2,3,4-tetrahydroquinoline-based selective human neuronal nitric oxide synthase (nNOS) inhibitors.

Neuronal nitric oxide synthase (nNOS) inhibitors are effective in preclinical models of many neurological disorders. In this study, two related series of compounds, 3,4-dihydroquinolin-2(1H)-one and 1,2,3,4-tetrahydroquinoline, containing a 6-substituted thiophene amidine group were synthesized and evaluated as inhibitors of human nitric oxide synthase (NOS). A structure-activity relationship (SAR) study led to the identification of a number of potent and selective nNOS inhibitors. Furthermore, a few representative compounds were shown to possess druglike properties, features that are often difficult to achieve when designing nNOS inhibitors. Compound (S)-35, with excellent potency and selectivity for nNOS, was shown to fully reverse thermal hyperalgesia when given to rats at a dose of 30 mg/kg intraperitonieally (ip) in the L5/L6 spinal nerve ligation model of neuropathic pain (Chung model). In addition, this compound reduced tactile hyperesthesia (allodynia) after oral administration (30 mg/kg) in a rat model of dural inflammation relevant to migraine pain.

Discovery of N-(3-(1-Methyl-1,2,3,6-tetrahydropyridin-4-yl)-1H-indol-6-yl) thiophene-2-carboximidamide as a Selective Inhibitor of Human Neuronal Nitric Oxide Synthase (nNOS) for the Treatment of Pain

3,6-Disubstituted indole derivatives were designed, synthesized, and evaluated as inhibitors of human nitric oxide synthase (NOS). Bulky amine containing substitution on the 3-position of the indole ring such as an azabicyclic system showed better selectivity over 5- and 6-membered cyclic amine substitutions. Compound (-)-19 showed the best selectivity for neuronal NOS over endothelial NOS (90-fold) and inducible NOS (309-fold) among the current series. Compounds 16 and (-)-19 were shown to be either inactive or very weak inhibitors of human cytochrome P450 enzymes, indicating a low potential for drug-drug interactions. Compound 16 was shown to reverse thermal hyperalgesia in vivo in the Chung model of neuropathic pain. Compound 16 was also devoid of any significant vasoconstrictive effect in human coronary arteries, associated with the inhibition of human eNOS. These results suggest that 16 may be a useful tool for evaluating the potential role of selective nNOS inhibitors in the treatment of pain such as migraine and CTTH.

5-Alkyltryptamine derivatives as highly selective and potent 5-HT1D receptor agonists.

A series of 5-alkyltryptamines (6) and the corresponding conformationally constrained analogues (8) have been synthesized. The structure activity relationships (SAR) at the 5-position of the indole skeleton and the ethylamine side chain have been studied. Functional activities were assessed using isolated rabbit saphenous vein. Potent, selective ligands were found (6e, Ki 2.5 nM, 5-HT1B/5-HT1D 125-fold) that have potential for treating acute migraine.

1,2,3,4-tetrahydroquinoline-based selective human neuronal nitric oxide synthase (nNOS) inhibitors: lead optimization studies resulting in the identification of N-(1-(2-(methylamino)ethyl)-1,2,3,4-tetrahydroquinolin-6-yl)thiophene-2-carboximidamide as a preclinical development candidate.

Numerous studies have shown that selective nNOS inhibitors could be therapeutic in many neurological disorders. Previously, we reported a series of 1,2,3,4-tetrahydroquinoline-based potent and selective nNOS inhibitors, highlighted by 1 ( J. Med. Chem. 2011 , 54 , 5562 - 5575 ). Despite showing activity in two rodent pain models, 1 suffered from low oral bioavailability (18%) and moderate hERG channel inhibition (IC(50) = 4.7 μM). To optimize the properties of 1, we synthesized a small focused library containing various alkylamino groups on the 1-position of the 1,2,3,4-tetrahydroquinoline scaffold. The compounds were triaged based on their activity in the NOS and hERG manual patch clamp assays and their calculated physicochemical parameters. From these studies, we identified 47 as a potent and selective nNOS inhibitor with improved oral bioavailability (60%) and no hERG channel inhibition (IC(50) > 30 μM). Furthermore, 47 was efficacious in the Chung model of neuropathic pain and has an excellent safety profile, making it a promising preclinical development candidate.

5-Thienyltryptamine derivatives as serotonin 5-HT1B/1D receptor agonists: potential treatments for migraine

A series of 5-(2- or 3-thienyl)tryptamine derivatives (9) has been synthesized and shown to be potent and selective 5-HT1D versus 5-HT1B receptor agonists and, therefore, potential treatments for migraine.

Synthesis and SAR of N-(4-(4-alklylpiperazin-1-yl)phenyl)benzamides as muscarinic acetylcholine receptor subtype 1 (M1) anatgonists.

This Letter describes the synthesis and SAR, developed through an iterative analog library approach, of a novel series of selective M(1) mAChR antagonists, based on an N-(4-(4-alkylpiperazin-1-yl)phenyl)benzamide scaffold for the potential treatment of Parkinsons disease, dystonia and other movement disorders. Compounds in this series possess M(1) antagonist IC(50)s in the 350 nM to >10 microM range with varying degrees of functional selectivity versus M(2)-M(5).

Synthesis and structure-activity relationship of the isoindolinyl benzisoxazolpiperidines as potent, selective, and orally active human dopamine D4 receptor antagonists.

A new class of potent dopamine D4 antagonists was discovered with selectivity over dopamine D2 and the α‐1 adrenoceptor. The lead compound was discovered by screening our compound collection. The structure–activity relationships of substituted isoindoline rings and the chirality about the hydroxymethyl side chain were explored. The isoindoline analogues showed modest differences in potency and selectivity. The S enantiomer proved to be the more potent enantiomer at the D4 receptor. Several analogues with greater than 100‐fold selectivity for D4 over D2 and the α‐1 adrenoreceptor were discovered. Several selective analogues were active in vivo upon oral or intraperitoneal administration. A chiral synthesis starting from either D‐ or L‐O‐benzylserine is also described.

FV-082: A safer orally active broad-spectrum antiepileptic drug candidate

Broad spectrum Anti-Epileptic Drugs (AED) are valued for their potential to treat refractory epilepsy and as general ‘neurostabilizers’ have been employed for a variety of neurological diseases including migrane, biopolar disorder and neuropathic pain. However, the benefits of historical AEDs have been constrained by unintended CNS side effects. Combining proprietary breakthrough chemistry with Fluorinov Pharma and NIH’s in vivo phenotypic screening strategy identified three completely novel candidate drugs, including FV-082 with superior safety and efficacy profiles. FV-082 was screened across available in vitro and rodent seizure models at ASP, and was found to display an excellent spectrum of anti-seizure activity and safety profiles superior to that produced by Depakote, Neurontin and Keppra. FV-082 has an oral ED50 of 20.1 ± 0.7 and 17.4 ± 0.6 mg/kg in the rat MES and mouse 6Hz (ip) assays, respectively. FV-082 prevented seizures induced by sound in the Audiogenic Seizure (AGS)-susceptible Frings mouse model (i.p) with an ED50 value of 13.0 ± 2.0 mg/kg. In addition, FV-082 displayed significant efficacy in the electrically induced corneally kindled mouse, kindled rat amygdala and hippocampal seizures models. Importantly, FV-082 was also found to limit seizure spread and elevate seizure threshold in preclinical animal models, therefore, it has the potential to be effective in refractory, or pharmacoresistant, epilepsy. Also, the anticonvulsant pharmacology suggests applicability for treating multiple forms of epilepsy, such as generalized tonic−clonic, complex partial, and myoclonic seizures, at dose levels that confer a favorable safety margin (therapeutic index ≥ 34). Safety assessment of FV-082 suggests no interaction with the major CYP isoenzymes when tested up to 500 μM and no functional hERG activity when tested up to 20 μM. Further, acute toxicity studies revealed that FV082 exhibited no adverse effects at oral and intravenous doses in rats and mice with a maximally tolerated dose greater than 600 mg/kg in the mice (i.p) and rats (p.o). Also, there was a pronounced safety margin between behavioral efficacy (rat oral MES neurotoxicity and (rat TD50 > 600 mg/kg) for a protective index (rat oral TD50/MES ED50) of >34-fold. Hence, FV-082 displays a considerably broader CNS therapeutic index superior to historical AEDs. Additionally, a convenient and cost effective manufacturing process for FV-082 has been developed allowing for access to multi-kilogram scale synthesis. In-vivo pharmacokinetic studies in rat and dog revealed that FV-082 had excellent oral bioavailability and good oral half-life, and excellent plasma drug levels across multiple models of epilepsy and pain. In addition, drug exposure as measured by Cmax and AUC was shown to be linear with dose. Mechanistically, broad ion channel profiling in combination with a CEREP broad profiling screen (10 μM) across 90 known GPCR, ion channel, transporter and enzyme targets studies suggest that several mechanisms contribute to the observed pharmacological profile of FV-082 but that no single mechanism is likely to be a major contributor. In fact, in whole-cell patch-clamp recordings FV-082 inhibited voltage-gated Na + channel Nav1.7, and the CEREP panel indicated that FV-082 interacted with androgen receptor (AR) and (h) recombinant enzyme monoamine-oxidase-B (MAO-B). The anticonvulsant profile of FV-082 suggests that it may be useful for treating multiple forms of epilepsy (generalized tonic-clonic, complex partial, absence seizures), including refractory (or pharmacoresistant) epilepsy, at dose levels that confer a good safety margin. Furthermore, in models of neuropathic pain (spinal nerve injury [SNI] and formalin inflammatory pain, administration of a single dose showed robust efficacy (SNI: 50 mg/kg ip; and formalin: 71 mg/kg ip). Based on these promising preclinical data, FV-082 warrants clinical investigation.