Isostructurality in amino molecular salts of two dicarboxylic acids driven by noncovalent synthons

Isostructurality was investigated for the molecular salts of two carboxylates. The luminescence properties of the solid solutions of 4apy salts of these carboxylates indicate that this property can be used to fine tune the physical properties.

Improving the Solubility of Aripiprazole by Multicomponent Crystallization

Aripiprazole (ARI) is a third-generation antipsychotic with few side effects but a poor solubility. Salt formation, as one common form of multicomponent crystals, is an effective strategy to improve pharmacokinetic profiles. In this work, a new ARI salt with adipic acid (ADI) and its acetone hemisolvate were obtained successfully, along with a known ARI salt with salicylic acid (SAL). Their comprehensive characterizations were conducted using X-ray diffraction and differential scanning calorimetry. The crystal structures of the ARI-ADI salt acetone hemisolvate and ARI-SAL salt were elucidated by single-crystal X-ray diffraction for the first time, demonstrating the proton transfer from a carboxyl group of acid to ARI piperazine. Theoretical calculations were also performed on weak interactions. Moreover, comparative studies on pharmaceutical properties, including powder hygroscopicity, stability, solubility, and the intrinsic dissolution rate, were carried out. The results indicated that the solubility and intrinsic dissolution rate of the ARI-ADI salt and its acetone hemisolvate significantly improved, clearly outperforming that of the ARI-SAL salt and the untreated ARI. The study presented one potential alternative salt of aripiprazole and provided a potential strategy to increase the solubility of poorly water-soluble drugs.

Solution-Mediated Phase Transformation of Aripiprazole: Negating the Effect of Crystalline Forms on Dissolution and Oral Pharmacokinetics

We aimed to evaluate the effect of crystalline forms of aripiprazole, an antipsychotic drug for schizophrenia, on the dissolution rates and oral pharmacokinetics. Solubility, intrinsic dissolution rates, and tablet dissolution rates of the monohydrate (MA) and the anhydrous form (AA) were measured in various aqueous media while monitoring the phase transformation by ATR-FTIR. And their oral pharmacokinetics in dogs were compared. The intrinsic dissolution rate of MA was lower compared to AA, confirming its thermodynamic stability relative to AA in water. Phase transformations during the solubility measurement were media-dependent: In simulated gastric fluid, both AA and MA changed to HCl salt form, whereas AA and HCl salt form transformed to MA in simulated intestinal fluid. In vitro dissolution rates and dog oral pharmacokinetics of AA and MA tablets were similar. The results suggest that the solution-mediated transformation to HCl salt or MA negates the effect of different crystalline forms on dissolution rates in vivo and, consequently, on oral pharmacokinetics. We emphasize the importance of the dissolution tests employing various bio-relevant media for better prediction of in vivo performance and the selection of a solid form for development.

Structural determinants influencing halogen bonding: a case study on azinesulfonamide analogs of aripiprazole as 5-HT1A, 5-HT7, and D2 receptor ligands

A series of azinesulfonamide derivatives of long-chain arylpiperazines with variable-length alkylene spacers between sulfonamide and 4-arylpiperazine moiety is designed, synthesized, and biologically evaluated. In vitro methods are used to determine their affinity for serotonin 5-HT_1A, 5-HT₆, 5-HT₇, and dopamine D₂ receptors. X-ray analysis, two-dimensional NMR conformational studies, and docking into the 5-HT_1A and 5-HT₇ receptor models are then conducted to investigate the conformational preferences of selected serotonin receptor ligands in different environments. The bent conformation of tetramethylene derivatives is found in a solid state, in dimethyl sulfoxide, and as a global energy minimum during conformational analysis in a simulated water environment. Furthermore, ligand geometry in top-scored complexes is also bent, with one torsion angle in the spacer (τ₂) in synclinal conformation. Molecular docking studies indicate the role of halogen bonding in complexes of the most potent ligands and target receptors.

Correlating the melting point alteration with the supramolecular structure in aripiprazole drug cocrystals

Structural reasons for the melting point variations in isostructural cocrystals of the aripiprazole drug are investigated through combined spectroscopic and diffraction studies.

Polymorphism and isostructurality in sulfonylhydrazones

Five new methyl and halogen derivatives of triaryl sulfonylhydrazone were synthesized to understand polymorphism and isostructurality upon Cl–Me and inter-halogen exchange. Conformational rigidity and sulfonamide dimer synthon control the isostructurality in this family of crystal structures.