cotransporter GPR agonistic activity was evaluated for the h

GPR119 agonistic activity was evaluated for the human GPR119 receptor in a cell-based cAMP assay. The results expressed the potency as EC values and the inherent activity (IA) as percentages which were compared to the test compound with oleoylethanolamide (OEA), an endogenous ligand of GPR119 (defined as 100% activation). As expected, compounds – all showed lower values of lipophilicity than . In addition, they exhibited acceptable GPR119 agonist activity, which indicated that the spirocyclic cyclohexane structure of was a versatile right side moiety in GPR119 agonists. Among –, pyrimidine derivative expressed the highest LLE value (4.0). Therefore, we selected as a new lead compound having a better balance of agonistic activity and lipophilicity. Next, we moved to an optimization process, where we focused on improvement for values of solubility of (). Compound showed considerably lower values of solubility for Japanese Pharmacopoeia 1st fluid for a dissolution test adjusted to pH 1.2 (JP1) and Fed-state simulated intestinal fluid (FeSSIF). In general, solubility is one factor that governs oral absorption, and compounds with low solubility are related to low oral absorption. In our previous work and in other reports, conversion of the methylsulfonyl group at the left side to the dimethylcarbamoyl compound exhibited considerable improvement in solubility. Compound transformed by the dimethylcarbamoyl group showed higher values of solubility, particularly against JP1. However, agonistic activity of was decreased about three times compared with . Next, we focused on molecular planarity, which is known to influence crystal packing. Disruption of molecular planarity would be expected to decrease the efficiency of crystal packing, leading to improved solubility. In the case of , molecular planarity of the two aromatic rings was considered as the cause of low solubility. Therefore, we investigated how solubility and agonistic activity were affected by disrupting molecular planarity. Compound with the O cotransporter instead of the NH group connecting the two aromatic rings in showed little improvement in solubility and its agonistic activity decreased four times. In addition, the F atom on the benzene ring had little effect in solubility, and the agonistic activity of compound without the F atom decreased about ten times compared with . On the other hand, -methylation of slightly improved solubility and the agonistic activity of -methylated was greatly weakened. These results suggested that the intramolecular hydrogen bond between the F atom and the H atom of the NH group in might be important to achieve highly agonistic activity. This outcome was also indicated that steric repulsion between the -methyl group and the methyl group at the 5-position on the pyrimidine ring in significantly changed the molecular arrangement and led to decreased agonistic activity. In order to eliminate the steric repulsion, cyclization of the two methyl groups in was investigated. As anticipated, this cyclization boosted the agonistic activity significantly, and the thus-obtained showed an EC value of 4 nM and LLE value of 4.6. The similar improvement in agonistic activity was observed in the indoline derivative, which maintained coplanarity compared with compound . These results suggested that maintaining of coplanarity in the two aromatic rings was important to demonstrate potent agonistic activity. Unfortunately, cyclized compounds and exhibited little improvement in solubility against only acidic medium (JP1) as compared with . Another approach to decrease the efficiency of crystal packing while maintaining the coplanar arrangement was investigated. The methyl group at the 5-position of the pyrimidine ring was converted to either an ethyl group or an isopropyl group. Although ethyl derivative showed slight improvement in solubility against FeSSIF, the agonistic activity diminished about three times compared with . In isopropyl derivative , no improvement in solubility was observed and further agonistic activity attenuation occurred.