Hidetoshi Ushio

High Throughput Prediction of Oral Absorption: Improvement of the Composition of the Lipid Solution Used in Parallel Artificial Membrane Permeation Assay

The purpose of the present study was to improve the composition of the lipid solution used in parallel artificial membrane permeation assay for the precise prediction of oral absorption. We modified the composition of lipid solution, which was used to make a lipid membrane on the filter support. First, we changed the chain length of organic solvent (PC/alkyldienes [C7-C10]). A negative charge was then added to the membrane to mimic the intestinal membrane (PC/stearic acid/1,7-octadiene and PC/PE/PS/PI/cholesterol/1,7-octadiene). Finally, we examined the predictability of the PC/PE/PS/PI/CHO/1,7-octadiene membrane using structurally diverse compounds. Permeability coefficients of tested compounds were increased as the chain length of alkyldiene became shorter. The addition of a negative charge to the membrane increased the permeability of the basic compounds. However, the negatively charged membrane with stearic acid showed different permeability profiles from PC/PE/PSIPI/CHO. The predictability of the PC/PE/PS/PI/CHO/1,7-octadiene membrane was adequate (r = 0.858, n = 31) for use during the early stages of the drug discovery/development process.

Optimized conditions of bio-mimetic artificial membrane permeation assay.

Effects of pH and co-solvents on the bio-mimetic artificial membrane permeation assay were investigated to determine the optimal conditions for the prediction of oral absorption. The permeability (P(am)) of 33 structurally diverse drugs to the PC/PE/PS/PI/CHO/1,7-octadiene membrane system (bio-mimetic lipid (BML) membrane) was measured at pH 5.5, 6.5, and 7.4. The pH dependence of P(am) was in accordance with the pH partition theory. The better prediction of oral absorption (fraction of a dose absorbed) was shown under the pH 5.5 condition (r=0.866, n=25) and/or pH 6.5 (r=0.865, n=28), rather than pH 7.4 (r=0.767, n=24). Then, the appropriate conditions for determining the permeability of poorly soluble compounds were examined. Dimethysulfoxide (DMSO), ethanol (EtOH) and polyoxyethyleneglycol 400 (PEG 400) were added up to 30% to the transport medium as solubilizers. DMSO, EtOH and PEG 400 decreased P(am) of hydrocortisone and propranolol. For example, DMSO (30%) decreased P(am) of hydrocortisone by 60% and by 70% in the case of propranolol. DMSO and PEG 400 also decreased P(am) of ketoprofen. In contrast, EtOH produced an opposite effect on permeability, i.e. an increased P(am) of ketoprofen. Therefore, the high concentration of these co-solvents could lead to the under- or overestimation of drug permeability.

Oxidation of recombinant human parathyroid hormone: effect of oxidized position on the biological activity.

AbstractPurpose. To determine the oxidation products of recombinant human parathyroid hormone (rhPTH) treated with H2O2, the amino acid residue oxidized, and the biological activity of the oxidation products. Methods. Oxidized residues were determined by CNBr cleavage, trypsin digestion and subsequent fast atom bombardment mass spectrometry. The biological activity of each oxidized rhPTH was examined in rat osteosarcoma cell adenylate cyclase assay. Results. Three oxidized products were isolated, namely, Met at position 8 (Met8) sulfoxide, Met at position 18 (Met 18) sulfoxide and both positions Met sulfoxide. It appears that the Met8 and Met 18 oxidized forms are intermediates in the generation of the Met doubly oxidized form. All oxidized forms possessed reduced biological activity, more so for oxidation at Met8 than at Met 18. Conclusions. The region around Met8 is important for the activity of the parathyroid hormone.

Quantitative structure-intestinal permeability relationship of benzamidine analogue thrombin inhibitor.

The intestinal permeability of benzamidine analogue thrombin inhibitor is correlated with molecular volume, lipophilicity (calculated log P and IAM column capacity factor), hydrogen bond acidity/basicity and dipolarity.

The stability and degradation pathway of recombinant human parathyroid hormone : Deamidation of asparaginyl residue and peptide bond cleavage at aspartyl and asparaginyl residues

AbstractPurpose. The stability of recombinant human parathyroid hormone (rhPTH) was examined under acidic to alkaline conditions; its degradation pathways were elucidated from resultant products. Methods. Degradation assay was performed in the pH range 2 to 10 at 40, 50 and 60°C. The approximate molecular mass and pI values of the degradation products were estimated by electrophoresis. FAB-MS peptide mapping and amino acid composition analysis were used to determine these structures. The amount of each respective product was determined by HPLC. Results. At pH2, eight degradation products were found: l-30rhPTH, l-74rhPTH, l-71rhPTH, l-56rhPTH, l-45rhPTH, 46-84rhPTH, 31-84rhPTH and Asp76-rhPTH; these were mainly as a consequence of peptide bond cleavage of the amide bond of Asp. At pH9, five products were found: isoAsp16-rhPTH, Aspl6-rhPTH, Asp57-rhPTH, Asp76-rhPTH, 17-84rhPTH; the main degradation pathway was deamidation of Asn via a cyclic imide intermediate. Degradation products resulting from cleavage at Asp were increased in proportion to the extent that pH was lowered below 5. As pH was increased above 5, so were products resulting from deamidation of Asn. Correspondingly, levels of intact rhPTH were at a peak at pH5. Conclusions. Degradation of rhPTH under acidic conditions predominantly occurs by cleavage at Asp, whereas, above pH5, deamidation of Asn is the more prominent. rhPTH is most stable at pH5.

Characterization and monitoring of pseudo-polymorphs in manufacturing process by NIR

Moisture-sensitive pseudo-polymorphs with different stabilities were characterized, and their polymorphisms were monitored in the process of tableting and film coating by near-infrared (NIR) spectroscopy. In this study, we proved that we could successfully maintain the crystal form ratio in the tablet by controlling the moisture profile during the manufacture to sufficiently stabilize the drug product. Mitemcinal fumarate is an erythromycin derivative with two pseudo-polymorphic forms, hydrate and anhydrate. We characterized them by X-ray powder diffraction and water sorption isotherm plot analysis. Stability test revealed that the hydrate form is more stable than the anhydrate form. We established a quantitative method by using NIR and monitored the hydrate form ratio in the tablet during the tableting and coating process. The manufacturing room was controlled to between 40 and 60% RH. Although the hydrate form ratio just after the onset of tableting decreased to below 40%, 60% was obtained at the end of the final process which sufficiently retains stability. Transition of the hydrate form ratio during the manufacturing process was reasonable; this indicates that our NIR method is suitable for monitoring. Thus, NIR is one of the most suitable tools for in-process testing of these humidity-sensitive APIs.

Transport of NG-Nitro-L-Arginine Across Intestinal Brush Border Membranes by Na+-Dependent and Na+ Independent Amino Acid Transporters

AbstractPurpose. To clarify the transport mechanism of NG-nitro-L-arginine (L-NNA), a potent NO-synthase inhibitor, across intestinal brush border membranes (BBM). Methods. Dog intestinal BBM vesicles were used. Results. The time course of L-NNA uptake showed a Na+-dependent overshoot phenomenon. Concentration-dependence curves of L-NNA initial uptake were saturable in the presence and absence of Na+, indicating participation of Na+-dependent and Na+-independent carrier-mediated transport systems. The calculated kinetic parameters of L-NNA initial uptake indicate that the former is a low-affinity high-capacity system and the latter is a high-affinity low-capacity one, similar to those in neutral amino acid transport. Neutral and basic amino acids showed cis-inhibitory and trans-stimulatory effects on L-NNA uptake in the presence or absence of Na+. NG-Nitro-L-arginine methyl ester, another potent NO-synthase inhibitor, also had both effects, which were smaller than with amino acids. Conclusions. The present study clearly indicates that transport of L-NNA across the intestinal BBM occurs in the same manner as neutral amino acid transport. However, it is affected by both neutral and basic amino acids in the presence or absence of Na+ differently from that across plasma membranes of nonepithelial cells, because B0, + and b0, + amino acid transporters function partly in L-NNA transport across intestinal BBM.

Kinetic study of methionine oxidation in human parathyroid hormone

Abstract Human parathyroid hormone (hPTH) has two methionine (Met) residues at positions 8 and 18. These are oxidized to Met sulfoxide in the presence of an oxidant such as H2O2. In this study, the rate constants of Met oxidation were estimated in the 2–10 pH range. Between pH 4–7, the rate constants were constant. The rate constant of Met18 was greater than that of Met8 at all pH values examined. In the presence of urea, both rate constants increased with rise of urea concentration until the difference between them was negligible. In comparison with 1–34 hPTH, both rate constants of hPTH were smaller. From these results, we suggest that differences of folding, especially in the proximity of the Met residues, are reflected by the rate constants for Met oxidation.