Yoichi Kawashima

Binding properties of SA4503, a novel and selective σ1 receptor agonist

Abstract The binding profiles of SA4503 (1-(3,4-dimethoxyphenethyl)-4-(3-phenylpropyl)piperazine dihydrochloride), a novel σ receptor ligand, to σ1 and σ2 receptor subtypes in guinea pig and rat brain membranes were evaluated. SA4503 showed a high affinity for the σ1 receptor subtype labeled by (+)-[3H]pentazocine (IC50 = 17.4 ± 1.9 nM), while it had about 100-fold less affinity for the σ2 receptor subtype labeled by [3H]1,3-di(2-tolyl)guanidine ([3H]DTG) in the presence of 200 nM (+)-pentazocine. SA4503 showed little affinity for 36 other receptors, ion channels and second messenger systems. The inhibition curves of SA4503 for (+)-[3H]pentazocine binding were shifted to the right in the presence of guanosine 5′-o-(3-thiotriphosphate) (GTPγS), as similar to those of (+)-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine ((+)-3-PPP) and (+)-pentazocine, σ1 receptor agonists. SA4503 significantly increased the KD value, but did not affect the Bmax value for specific (+)-[3H]pentazocine binding. These results indicated that SA4503 is a potent and selective agonist for the σ1 receptor subtype in the brain. In addition, SA4503 inhibited specific (+)-[3H]pentazocine binding in a competitive manner.

Cyclosporine A Formulation Affects Its Ocular Distribution in Rabbits

Systemic Cyclosporine A (CsA) administration averts graft rejection after organ transplantation. In the eye, CsA is also beneficial in the treatment of autoimmune diseases, uveitis, Bechet’s disease, Sjögren’s syndrome, keratoconjunctivis sicca, and corneal transplantation (1). It has been suggested that topical rather than systemic CsA application could also be therapeutic, without causing systemic side effects, in the treatment of ocular disease. This may be possible because much less CsA can penetrate into the bloodstream after its topical instillation in either an aqueousor oil-based medium. It is expected that penetration from an aqueous medium will be even less than in oil because its solubility in water is much less. Various attempts were made to develop ophthalmic formulations that improve ocular CsA penetration, including an alpha-cyclodextrin vehicle (2), vegetable oils (3), liposomes (4), collagen shields (5), microor nanospheres (6), and oilin-water emulsion (7). However, none of these deliver therapeutic amounts of CsA into target ocular tissues with low ocular toxicity. In this work, we compared in rabbit ocular tissues CsA pharmacokinetics and distribution resulting from its topical application as an oil-based medium, o/w emulsion, and CsA aqueous clear solution containing a surfactant. Our results suggest that only an aqueous solution containing the nonionic surfactant MYS-40 delivers therapeutic levels of CsA.

Synthesis, structure and quantitative structure-activity relationships of σ receptor ligands, 1-[2-(3,4-dimethoxyphenyl)ethyl]-4-(3-phenylpropyl)piperazines

A set of the title compounds having different substituents (R1, R2) on their phenyl groups was synthesized to find sigma receptor binding affinity. Among the compounds, 2b (R1 = R2 = Cl) has the most potent sigma 1-binding activity, while 2a (R1 = R2 = H, SA4503) was most selective to sigma 1 over sigma 2 receptor. The crystal structures of 2a and 2b were shown, by X-ray crystallography, to be similar except for the one torsional angle of their propylene parts. Quantitative structure-activity relationship study suggested the affinity of the compounds to the sigma 1 receptor was dependent on the electronic feature, Swain-Luptons R or Sz that was derived by molecular orbital method, of R1 and R2.

Resolution of the enantiomers of thiol compounds by reversed-phase liquid chromatography using chiral derivatization with 2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl isothiocyanate

Abstract A new derivatization procedure has been developed for converting enantiomeric thiol compounds into their diastereomers for resolution by reversed-phase liquid chromatography. The thiol compounds were derivatized with 2,3,4,6-tetra-O-acetyl-β- d -glucopyranosyl isothiocyanate as chiral derivatization reagent and triethylamine as basic catalyst. The thiol group reacted smoothly with the isothiocyanate to form the dithiocarbamate derivative within 30 min at room temperature. The reaction mixture can be injected directly into the chromatograph without purification procedures. The ultraviolet detection wavelength was set at 250 nm, based on the absorption of the thiocarbonyl group. The resulting diastereomers were well separated on an octadecyl-bonded silica column with methanol-0.01 M phosphate buffer as the mobile phase.

Micromeritic characteristics and agglomeration mechanisms in the spherical crystallization of bucillamine by the spherical agglomeration and the emulsion solvent diffusion methods

Abstract The physical properties of bucillamine were modified by the application of two spherical crystallization techniques — the spherical agglomeration and the emulsion solvent diffusion methods. The mechanisms of spherical agglomeration and crystallization were investigated. In the spherical agglomeration method, the microcrystalline drug precipitates were aggregated via liquid bridges of dichloromethane liberated from the crystallization solvent system. The growth rates were mainly determined by the amount of dichloromethane formulated. In the emulsion solvent diffusion method, the drug was precipitated within finely dispersed ethanol drops and these quasi-emulsion droplets were transformed into rigid spherical agglomerates. The mechanism determining the structure of the resultant agglomerates was clarified by measuring their mechanical strength. The crystal binding points within agglomerates produced by the spherical agglomeration method were distributed uniformly through the entire cross-section, whereas in the agglomerates prepared by the emulsion solvent diffusion method, they were localized in the agglomerate surface crust.

Conformational study of 2-phenylbenzothiazine part of SA2995, a Ca2+ antagonist having a benzothiazine skeleton, and structure-activity relationships

Nuclear magnetic resonance (NMR) studies were carried out for the title compound ((+/-)-3,4-dihydro-2-[5-methoxy-2- [3-[N-methyl-N-[2-(3,4-methylenedioxy)phenoxy]ethyl]amino] propoxy]phenyl]-4-methyl-3-oxo-2H-1,4-benzothiazine) (1a; R = H) and its 2-substituted analogs (1b; R = OCH3, 1c; R = SCH3, 1d; R = CH3, 1e; R = i-C3H7) which had Ca2+ antagonistic activities. Conformational analysis using the model compounds of the 2-phenylbenzothiazine (2-PBT) part of 1 by semiempirical molecular orbital method agreed with the NMR behavior. Two local minimum conformations, having different rotational angles (theta 1) of the 2-phenyl ring, were suggested for biologically active 1a-1d. The molar fractional ratios, including the conformations within a particular theta 1 range that contained each global minimum conformation, were found to correlate well with the activities. In the same theta 1 range, any stable conformation was not indicated for non-active compound 1e. From these results, the active conformation for the 2-PBT part of 1 was suggested to be similar to the global minimum conformation indicated for the most potent 1a.

Direct high-performance liquid chromatographic resolution of a novel benzothiazine Ca2+ antagonist and related compounds

Abstract Enantiomers of 3,4-dihydro-2-{;5-methoxy-2-[3-(N-methyl-N-{;2-[(3,4-methylenedioxy)phenoxy]ethyl};amino)propoxy]phneyl};-4-methyl-3-oxo-2H-1,4- benzothiazine hydorgen fumarate (I), a novel and potent Ca 2+ antagonist, and its synthetic pecursors, phenol (II) and bromide (III), were directly resolved by high-performance liquid chromatography on a chiral column, with a stationary phase of cellulose carbamate-coated silica gel. Further, the resolution of some 2-(substituted-phenyl)benzothiazines (IVa–IVl) was investigated to study the effects of 2-phenyl ring substituents on chial recognition. As an index of the characteristics of substituents, substituent constants for quantitative structure-activity relationship studies were used. The correlations between the resolution efficiency ( R s ) and the substituent constants for these benzothiazines were investigated by regression analysis. As a result, for 2-(4-substituted-phenyl)-benzothiazines, R s showed good correlation with E s , Tafts steric parameter [correlation coefficient ( r ) = 0.99]. It was also shown that R s correlated with R , an electronic constant for the resonance effect, for 2-(2-hydroxy-5-substituted-phenyl)benzothiazines ( r =0.92). These findings suggest that the 2-phenyl ring plays an important role in chiral recognition in the resolution of these benzothiazines.

Pharmaceutical design of Kary Uni® ophthalmic suspension

Pirenoxine ophthalmic solution was developed based on the quinoid theory which is one of the theories for development mechanism of senile cataracts, and its usefulness for treatment of cataracts has been proved. Since pirenoxine is unstable in aqueous solution, conventional products are required the reconstitution procedure of tablet (or granule) with accompanied solvent before use. Therefore, there are some problems with respect to good patients compliance. Under these circumstances, one bottle type and stable pirenoxine ophthalmic product has been desired. Our concepts for designing new pirenoxine ophthalmic product are as follows, (1) To be one bottle type product, (2) To stabilize pirenoxine in aqueous media for three years at room temperature, (3) To keep its bioequivalence to conventional products. Pirenoxine showed very low solubility in acidic aqueous solution and good stability in aqueous suspension (pH 3.4-4.0) for three years at room temperature in our study. On the other hand, pirenoxine showed good solubility in neutral aqueous solution. We applied these unique properties and developed a new pirenoxine ophthalmic product, Kary Uni® ophthalmic suspension. As no buffer agent is contained in Kary Uni® ophthalmic suspension, the pH of the solution is elevated to the physicological pH of tears immediately after instillation, and pirenoxine microparticles rapidly dissolve in tears. As a result, the bioequivalence to conventional products can be obtained. Kary Uni® is a one bottle type ophthalmic suspension in ready to use, without the reconstitution procedure required for conventional products and is especially evaluated as a new type DDS pharmaceutical product taking advantage of the transformation on the living environment of ocular surface.