Compounds and administered orally to fasted
Compounds , , and administered orally to fasted Harlan Sprague-Dawley rats 1h prior to trigeminal stimulation, decreased extravasation in this model in a dose-related manner, with an estimated ID of 1, 10 and 100μg/kg, respectively (determined 15min after stimulation, ). For comparison, the clinically-efficacious therapy sumatriptan for the abortive treatment of migraine had an ID value of 1000μg/kg. Upon observation of the Cmax values and activity, compounds and showed a Cmax/mGlu EC between 3 and 8-fold respectively (and higher than the corresponding Cmax/CysLT1 IC) suggesting the impact of mGlu potentiator driving the observed PPE efficacy. Compound showed a Cmax/CysLT1 IC about 8-fold, and providing the largest effect on efficacy of the three compounds. Although this is a limited set of compounds to drive many conclusions, this result might suggest the significant effect of CysLT1 pharmacology for migraine treatment. shows the dose-response curve of Tranexamic Acid (vs. vehicle) in the PPE model after oral administration. The graphic shows statistical significant decreased extravasation at a dose of 0.1μg/kg, however it is 1mg/kg the dose that inhibits approximately 100% of the extravasation on the stimulated side of the dura relative to the unstimulated side (ID). The mGlu PAM/CysLT1 antagonist polypharmacology for compound and its exquisite efficacy in the rat PPE model led us to further profile this compound, in particular regarding its selectivity index towards other mGlu targets. Tetrazole was selective against mGlu, mGlu, mGlu, mGlu and mGlu as agonist, potentiator or antagonist (). In addition, lacked agonist or antagonist activity at the mGlu receptor. Compound showed <50% activity at 10μM when tested in the Cerep mini-panel diversity panel and it did not possess relevant activity at any serotonin receptors (supplemental material). In addition, compound showed >40μM for 2D6, 3A4 and 2C9, and no significant inhibition (<15%) of hERG channel in a [H]Dofetilide binding assay. A more detailed pharmacokinetic profile is shown in . Compound had low clearance for both rat and dog, a low volume of distribution and oral bioavailabilities >20%. Although we believe that brain penetration is not necessary for efficacy in migraine, tetrazole exhibited a low brain exposure with B/P <1% when dosed orally at 15mg/kg. In general, the syntheses of the compounds described in this paper were assembled by first preparing a precursor including domains B and C. Domain A was then coupled to the combined domain B/C to produce a construct containing domains A, B and C. Finally, the acidic tetrazole or carboxylic acid was formed. The synthesis of compound was selected as a representative (). Reaction between 4-hydroxybenzyl alcohol and 6-chloronicotinitrile was mediated by potassium carbonate at 100°C affording 6-(4-hydroxymethyl-phenoxy)-nicotinonitrile in 32% yield. Combining polymer-supported triphenylphosphine, iodine, imidazole and alcohol led to iodo derivative , which was treated with (2,4-dihydroxy-3-methyl-phenyl)-propan-l-one () and cesium carbonate in acetone to provide in 67% yield over two steps. Nitrile was heated with trimethylamine hydrochloride and sodium azide in a pressure flask to give tetrazole in 40% yield. In summary, we have described the impact of structural modifications on pyridine containing hydroxyacetophenone tetrazole scaffold towards its dual pharmacology as an mGlu PAM and CysLT1 antagonist. The exploration led to the discovery of compound as a potent mGlu PAM and CysLT1 antagonist that demonstrated selectivity over other mGlu and GPCR receptors. Compound exhibited bioavailability >20% upon oral dosing and an acceptable PK profile in both rat and dog to warrant study in a rodent model of migraine (PPE assay). Indeed, compound showed full efficacy in the rat PPE model of migraine with an ID=1μg/kg. Finally, it should be noted that this effort was a demonstration of a multi-target SAR effort in which co-optimization of two separate SARs was undertaken. Multi-target drug discovery (MTDD) is an emerging area of increasing interest to the medicinal chemistry community. Drugs that modulate several targets in one molecule have the potential for an improved balance of efficacy and safety compared to single target agents. Additional studies around this dual mechanism will be disclosed in due course.