Synthesis and Preclinical Characterization of LY3154885, a Human Dopamine D1 Receptor Positive Allosteric Modulator with an Improved Nonclinical Drug-Drug Interaction Risk Profile.

Results from recently completed clinical studies suggest the dopamine D1 receptor positive allosteric modulator (PAM) mevidalen (1) could offer unique value for lewy body dementia (LBD) patients. In nonclinical assessments, 1 was mainly eliminated by CYP3A4-mediated metabolism, therefore at the risk of being a victim of drug-drug interactions (DDI) with CYP3A4 inhibitors and inducers. An effort was initiated to identify a new D1 PAM with an improved DDI risk profile. While attempts to introduce additional metabolic pathways mediated by other CYP isoforms failed to provide molecules with an acceptable profile, we discovered that the relative contribution of CYP-mediated oxidation and UGT-mediated conjugation could be tuned to reduce the CYP3A4-mediated victim DDI risk. We have identified LY3154885 (5), a D1 PAM that possesses similar in vitro and in vivo pharmacologic properties as 1, but is metabolized mainly by UGT, predicting it could potentially offer lower victim DDI risk in clinic.

Discovery of selective N-[3-(1-methyl-piperidine-4-carbonyl)-phenyl]-benzamide-based 5-HT1 F receptor agonists: Evolution from bicyclic to monocyclic cores.

Preclinical experiments and clinical observations suggest the potential effectiveness of selective 5-HT1F receptor agonists in migraine. Identifying compounds with enhanced selectivity is crucial to assess its therapeutic value. Replacement of the indole nucleus in 2 (LY334370) with a monocyclic phenyl ketone moiety generated potent and more selective 5-HT1F receptor agonists. Focused SAR studies around this central phenyl ring demonstrated that the electrostatic and steric interactions of the substituent with both the amide CONH group and the ketone CO group play pivotal roles in affecting the adopted conformation and thus the 5-HT1F receptor selectivity. Computational studies confirmed the observed results and provide a useful tool in the understanding of the conformational requirements for 5-HT1F receptor agonist activity and selectivity. Through this effort, the 2-F-phenyl and N-2-pyridyl series were also identified as potent and selective 5-HT1F receptor agonists.

GluK1 antagonists from 6-(carboxy)phenyl decahydroisoquinoline derivatives. SAR and evaluation of a prodrug strategy for oral efficacy in pain models.

The synthesis and structure-activity relationship of decahydroisoquinoline derivatives with various benzoic acid substitutions as GluK1 antagonists are described. Potent and selective antagonists were selected for a tailored prodrug approach in order to facilitate the evaluation of the new compounds in pain models after oral administration. Several diester prodrugs allowed for acceptable amino acid exposure and moderate efficacy in vivo.

GluK1 antagonists from 6-(tetrazolyl)phenyl decahydroisoquinoline derivatives: in vitro profile and in vivo analgesic efficacy.

We have explored the decahydroisoquinoline scaffold, bearing a phenyl tetrazole, as GluK1 antagonists with potential as oral analgesics. We have established the optimal linker atom between decahydroisoquinoline and phenyl rings and demonstrated an improvement of both the affinity for the GluK1 receptor and the selectivity against the related GluA2 receptor with proper phenyl substitution. In this Letter, we also disclose in vivo data that led to the discovery of LY545694·HCl, a compound with oral efficacy in two persistent pain models.

Discovery of a potent, dual serotonin and norepinephrine reuptake inhibitor.

The objective of the described research effort was to identify a novel serotonin and norepinephrine reuptake inhibitor (SNRI) with improved norepinephrine transporter activity and acceptable metabolic stability and exhibiting minimal drug-drug interaction. We describe herein the discovery of a series of 3-substituted pyrrolidines, exemplified by compound 1. Compound 1 is a selective SNRI in vitro and in vivo, has favorable ADME properties, and retains inhibitory activity in the formalin model of pain behavior. Compound 1 thus represents a potential new probe to explore utility of SNRIs in central nervous system disorders, including chronic pain conditions.

Pharmacological characterization of the competitive GLUK5 receptor antagonist decahydroisoquinoline LY466195 in vitro and in vivo.

The excitatory neurotransmitter glutamate has been implicated in both migraine and persistent pain. The identification of the kainate receptor GLU(K5) in dorsal root ganglia, the dorsal horn, and trigeminal ganglia makes it a target of interest for these indications. We examined the in vitro and in vivo pharmacology of the competitive GLU(K5)-selective kainate receptor antagonist LY466195 [(3S,4aR,6S,8aR)-6-[[(2S)-2-carboxy-4,4-difluoro-1-pyrrolidinyl]-methyl]decahydro-3-isoquinolinecarboxylic acid)], the most potent GLU(K5) antagonist described to date. Comparisons were made to the competitive GLU(K5)/alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor antagonist LY293558 [(3S,4aR,6R,8aR)-6-[2-(1(2)H-tetrazole-5-yl)ethyl]-decahydroisoquinoline-3-carboxylic acid], other decahydroisoquinoline GLU(K5) receptor antagonists, and the noncompetitive AMPA receptor antagonist LY300168 [1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodi-azepine]. When characterized electrophysiologically in rat dorsal root ganglion neurons, LY466195 antagonized kainate (30 microM)-induced currents with an IC50 value of 0.045 +/- 0.011 microM. In HEK293 cells transfected with GLU(K5), GLU(K2)/GLU(K5), or GLU(K5)/GLU(K6) receptors, LY466195 produced IC50 values of 0.08 +/- 0.02, 0.34 +/- 0.17, and 0.07 +/- 0.02 microM, respectively. LY466195 was efficacious in a dural plasma protein extravasation (PPE) model of migraine with an ID100 value of 100 microg/kg i.v. LY466195 was also efficacious in the c-fos migraine model, with a dose of 1 microg/kg i.v. significantly reducing the number of Fos-positive cells in the rat nucleus caudalis after electrical stimulation of the trigeminal ganglion. Furthermore, LY466195 showed no contractile activity in the rabbit saphenous vein in vitro. The diethyl ester prodrug of LY466195 was also efficacious in the same PPE and c-fos models after oral administration at doses of 10 and 100 microg/kg, respectively while having no N-methyl-D-aspartate antagonist-like behavioral effects at oral doses up to 100 mg/kg.

Two prodrugs of potent and selective GluR5 kainate receptor antagonists actives in three animal models of pain.

Amino acids 5 and 7, two potent and selective competitive GluR5 KA receptor antagonists, exhibited high GluR5 receptor affinity over other glutamate receptors. Their ester prodrugs 6 and 8 were orally active in three models of pain: reversal of formalin-induced paw licking, carrageenan-induced thermal hyperalgesia, and capsaicin-induced mechanical hyperalgesia.

Substituted furo[3,2-b]pyridines: novel bioisosteres of 5-HT 1F receptor agonists.

Synthesis and evaluation of a series of 2,3,5- and 3,5-substituted furo[3,2-b]pyridines were undertaken in order to investigate their utility as bioisosteres of 5-HT(1F) receptor agonist indole analogues, 1-3. The replacement proved to be effective, providing compounds with similar 5-HT(1F) receptor affinity and improved selectivity when compared with the indole analogues. Through these studies we identified 4-fluoro-N-[3-(1-methyl-piperidin-4-yl)-furo[3,2-b]pyridin-5-yl]-benzamide (5), a potent and selective 5-HT(1F) receptor agonist with the potential to treat acute migraine.

Novel potent 5-HT(1F) receptor agonists: structure-activity studies of a series of substituted N-[3-(1-methyl-4-piperidinyl)-1H-pyrrolo[3,2-b]pyridin-5-yl]amides.

Compound 1a (LY334370), a selective 5-HT(1F) receptor agonist (SSOFRA), inhibited dural inflammation in the neurogenic plasma protein extravasation model of migraine and demonstrated clinical efficacy for the acute treatment of migraine. Although 1a was greater than 100-fold selective over both the 5-HT(1B) and 5-HT(1D) receptors, it exhibited appreciable 5-HT(1A) receptor affinity. Described here is the synthesis and evaluation of a series of pyrrolo[2,3-c]pyridine and pyrrolo[3,2-b]pyridine (2a and 3a) as well as pyrrolo[3,2-d]pyrimidine (4a) analogues of 1a, compounds prepared in an effort to identify SSOFRAs with improved selectivity over other 5-HT(1) receptor subtypes. The pyrrolo[3,2-b]pyridine analogue 3a showed high 5-HT(1F) receptor affinity but offered no improvement in selectivity compared to 1a. However, the C-5 acetamide derivative, 3b, was greater than 100-fold selective over the 5-HT(1A), 5-HT(1B), and 5-HT(1D) receptors. SAR studies of this series determined that alkylamides in particular exhibited high selectivity for the 5-HT(1F) receptor. Replacement at C-5 with other substituents decreased affinity or selectivity. These SAR studies identified SSOFRAs that demonstrated oral activity in the neurogenic plasma protein extravasation model, a model indicative of antimigraine activity.

Ethyl (3S,4aR,6S,8aR)-6-(4-ethoxycar- bonylimidazol-1-ylmethyl)decahydroiso-quinoline-3-carboxylic ester: a prodrug of a GluR5 kainate receptor antagonist active in two animal models of acute migraine.

Amino diacid 3, a highly selective competitive GluR5 kainate receptor antagonist, exhibited high GluR5 receptor affinity and selectivity over other glutamate receptors. Its diethyl ester prodrug 4 was orally active in two models of migraine: the neurogenic dural plasma protein extravasation model and the nucleus caudalis c-fos expression model. These data suggest that a GluR5 kainate receptor antagonist might be an efficacious antimigraine therapy with a novel mechanism of action.