Predicting drug release and degradation kinetics of long-acting microsphere formulations of tacrolimus for subcutaneous injection

Today, tacrolimus represents a cornerstone of immunosuppressive therapy for liver and kidney transplants and remains subject of preclinical and clinical investigations, aiming at the development of long-acting depot formulations for subcutaneous injection. One major challenge arises from establishing in vitro-in vivo correlations due to the absence of meaningful in vitro methods predictive for the in vivo situation, together with a strong impact of multiple kinetic processes on the plasma concentration-time profile. In the present approach, two microsphere formulations were compared with regards to their in vitro release and degradation characteristics. A novel biorelevant medium provided the physiological ion and protein background. Release was measured using the dispersion releaser technology under accelerated conditions. A release of 100% of the drug from the carrier was achieved within 7 days. The capability of the in vitro performance assay was verified by the level A in vitro-in vivo correlation analysis. The contributions of in vitro drug release, drug degradation, diffusion rate and lymphatic transport to the absorption process were quantitatively investigated by means of a mechanistic modelling approach. The degradation rate, together with release and diffusion characteristics provides an estimate of the bioavailability and therefore can be a guide to future formulation development.

Novel Dissolution Approach for Tacrolimus-Loaded Microspheres Using a Dialysis Membrane for in Vitro-in Vivo Correlation

The aim of this study was to establish a novel approach to in vitro dissolution evaluation using a combination of the paddle method and a dialysis membrane, both to predict the overall in vivo performance of tacrolimus microspheres and also to identify a suitable dissolution test method to describe the in vivo initial burst phenomenon. This new dissolution method for evaluating the release of tacrolimus from microspheres consisted of rotating a customized paddle inside a dialysis membrane using a conventional paddle apparatus. Findings were compared with a method in which the paddle was rotated outside the dialysis membrane, the conventional paddle method, and the flow-through cell method. We concluded that the paddle method with a dialysis membrane and internal agitation, which was designed to mimic in vivo conditions, predicted the overall pharmacokinetic (PK) profile of tacrolimus microspheres whereas the conventional paddle method described the initial burst. These findings suggest that it may not be possible to predict both the PK profile and initial burst using a single analysis method. We therefore recommend that evaluation of the initial burst be performed separately. In conclusion, we propose that combination of the paddle method with a dialysis membrane and internal agitation to evaluate the overall PK profile, together with the paddle method to describe the in vivo initial burst, represents a novel approach to in vitro dissolution evaluation for microsphere formulations.

A study of appropriate flow rate settings for cell-free and concentrated ascites reinfusion therapy and change of cytokine concentrations in ascites

We examined appropriate flow rates for high collection rates of Total Protein (TP) and Albumin (Alb) and a change of IL-6 concentrations in the cell-free and concentrated ascites reinfusion therapy (CART) process. No significant changes were observed in IL-6 concentration in the ascites storage test and the circulatory stimulation test. However, it was confirmed that the quantity of IL-6 in the ascites decreased by means of filtration and concentration. In some cases, it quickly reached high concentration rates at a higher flow rate (200 mL/min) setting, but clogging or pressure increase has occurred in the hollow fiber filter. Therefore, it was concluded that a low flow rate (50 mL/min) setting was best and provides safer conditions for filtration and concentration in order to collect TP and Alb effectively and reuse it as autologous protein, which is the primary objective of CART.

Mild resistance to thyroid hormone with a truncated thyroid hormone receptor beta

Recent studies have revealed mutations in the thyroid hormone receptor beta (TR beta) gene as a cause of the most cases of the thyroid hormone resistance syndrome. We have identified a novel nonsense mutation in codon 449 in the 3' end of exon 10 in the TR beta gene in a 16-year-old male patient with generalized resistance to thyroid hormone who also had familial thyroxine binding globulin deficiency. Receptor protein generated from this gene is thought to be 13 amino acid deficient at carboxy-terminus. Resistance to thyroid hormone was mild at least when the patient was evaluated. The patient was eumetabolic in the presence of elevated plasma-free thyroid hormone levels, and both thyrotrope and peripheral tissues responded to triiodothyronine (T3) administration. This mildness of resistance is in contrast to severe resistance to thyroid hormone in two previously reported cases with truncated receptors in which 16 amino acids or 11 amino acids were deficient at C-terminus. Thus, truncation of C-terminus of thyroid hormone receptor beta does not uniformly produce sever resistance.

Extraction of diffuse reflection spectrum on reflectance spectroscopy for solid or powder surfaces

Reflectance spectroscopy usually produces distorted spectra because it is arbitrarily composed of two different types of reflectance, specular reflectance and diffuse reflectance. That is why this has been an annoying problem for reflectance spectroscopists. In this report, we studied the extraction of only the diffuse reflectance spectra from several reflectance spectra using redundant multiple spectral information, non-negative transformation of the recorded spectra and information processing as the multi-curve resolution. As a result, we found that we could estimate just the diffuse reflectance spectral profile.

The in vitro synthesized and processed human insulin receptor precursor binds insulin

The cell-free examination of the human insulin receptor during biogenesis may provide a greater understanding of the elements that contribute to the acquisition of receptor function. The insulin receptor precursor components were produced in a cell-free system and the insulin binding ability of the [35S]methionine-labeled translation products was determined. The processed proreceptor represented by a 190 kDa band was retained on insulin-linked biotin-streptavidin agarose or an insulin column. The insulin binding 190 kDa band migrated slower than the non-binding 190 kDa band on SDS-PAGE which suggests that covalent modifications account for these differences. The trypsin-digested product of the 190 kDa proreceptor was also retained on insulin-linked biotin-streptavidin agarose, however the alpha-subunit precursor was retained on insulin agarose to a much lesser degree. We conclude that a significant fraction of the processed, in vitro translated insulin proreceptor acquires insulin binding ability.

Decay-accelerating factor (CD55) deficiency phenotypes in Japanese

Decay-accelerating factor (DAF, CD55) is a complement regulatory glycoprotein that expresses the Cromer-system blood group antigens. Two, very rare, inherited DAF-deficiency phenotypes, Inab and Dr(a-), were identified in Japanese propositi. Red cells of the Inab phenotype propositus had no Cromer-system antigens and did not bind monoclonal anti-DAF. The Inab propositus was homozygous for a DAF non-sense mutation, converting the Trp53 codon to a stop codon; her parents were heterozygous for this mutation. This is the same mutation as that previously found in the original Inab phenotype propositus. Haemagglutination-inhibition titrations of the serum of the Inab propositus with soluble-recombinant DAF demonstrated that anti-IFC represents a mixture of antibodies to all four DAF short consensus repeat domains. The Dr(a-) individual had very low levels of Cromer-system antigens and DAF on her red cells. Loss of a TaqI restriction site from DAF exon 5 suggested that she has a previously detected mutation, encoding a Ser165Leu substitution. Red cells of the two propositi did not show abnormal levels of lysis in an acid lysis test, but after blocking of CD59 with monoclonal antibody, Inab phenotype red cells showed more lysis than Dr(a-) red cells, and Dr(a-) cells showed substantially more lysis than control cells.

Specific PCR amplification for N-ras mutations in neoplastic thyroid diseases

We analyzed point mutations of N-ras protooncogene codon 61 in thyroid neoplasms by means of a mutation-specific PCR method. In this method, one of the paired primers has a base at the 3' terminal that is complementary to a mutated base of the DNA sequence to be analyzed. With this primer, only alleles which have the same mutation can be amplified. Among 24 thyroid tissues, we detected 2 point mutations out of 7 follicular carcinomas (29%). One tumor had a cytosine to adenine substitution mutation at the first base of codon 61, and the other had an adenine to guanine substitution mutation in the second base of the same codon. The same mutations were not detected in 7 follicular adenomas or 1 papillary carcinoma. These results were confirmed by both dot blot hybridization and direct sequencing method. Mutation of N-ras codon 61 may be significant in malignant transformation of follicular thyroid tumors. Because of its easy availability, the mutation-specific PCR method is a useful screening test for N-ras mutations.

[Specific amplification by PCR for N-ras mutation in thyroid follicular cartinoma]

Mutation-specific PCR amplification, a special version of allele-specific amplification, is a method for detection of known mutation. In this method, one of the paired primers has a base at the 3' terminal that is complementary to a mutated base. With this primer, only alleles which have the same mutation can be amplified. We analyzed point mutations of N-ras protooncogene codon 61 in thyroid neoplasms using this mutation-specific PCR amplification method. This method is easy to perform, and many samples can be treated at one time. We detected 2 point mutations of N-ras codon 61 out of 7 follicular carcinomas. One was a cytosine to adenine substitution mutation at the first base, and the other was an adenine to guanine substitution mutation in the second base. These mutations were not detected in 7 follicular adenoma and 1 papillary carcinoma. The results were confirmed by both dot blot hybridization and direct sequencing. Mutation-specific amplification is a powerful method for detection of known mutations of protooncogenes or tumor suppressor genes in investigation of the cancer biology.

Simultaneous development of insulin dependent diabetes mellitus and alopecia areata universalis

Alopecia areata universalis developed gradually over nine months in a 25-year-old woman. When her scalp hairs were totally lost and other body hair began to fall out, the symptoms of insulin dependent diabetes mellitus, an organ-specific autoimmune disease, developed rapidly and progressed to diabetic coma. Alopecia did not regress after the metabolic state improved following insulin therapy. Biopsy of the scalp skin revealed significant reduction of the total number of hair bulbs and prominent lymphocyte infiltration into the remaining hair follicles. Insulin dependent diabetes mellitus and alopecia areata universalis are both thought to be related to the autoimmune mechanism and sometimes coexist. However, simultaneous development of these two disorders is extremely rare.

[The significance of serum fructosamine measurement in patients with thyroid diseases]

Serum fructosamine was measured in patients with Graves' disease and primary hypothyroidism. Fructosamine levels and fructosamine per albumin ratio were significantly lower in patients with Graves' disease than in normal subjects, while they were significantly higher in patients with primary hypothyroidism. Fructosamine levels were normalized by treatment in the euthyroid state in patients with Graves' disease. Along with the normalization of thyroid stimulating hormone levels, fructosamine levels returned to the normal range in patients with primary hypothyroidism with treatment. There were significant correlations between fructosamine levels and free triiodothyronine levels, free thyroxine levels, thyroid stimulating hormone levels, hemoglobin A1C levels, albumin levels, and creatine phosphokinase levels. We concluded that it was useful to measure serum fructosamine as an indicator of peripheral metabolic function in patients with thyroid diseases.

[A study of the secretion capacity of TSH-beta in patients with pituitary disorders]

We studied the secretion capacity of TSH-beta in 63 patients with various pituitary disorders, carrying out the observation of TSH-beta changes after TRH administration. Serum TSH-beta concentrations were measured by radioimmunoassay according to the modified method of Kourides. Serum TSH concentrations were measured by immunoradiometric assay, and serum concentrations of free thyroid hormones were measured by radioimmunoassay. Basal TSH-beta concentrations were below 0.39 ng/ml in 17 patients with Acromegaly, below 0.56 ng/ml in 5 patients with Prolactinoma, below 0.68 ng/ml in 4 patients with Cushing's disease, below 0.48 ng/ml in 12 patients with non-functioning tumor, below 6.4 ng/ml in 16 patients with SITSH, and below 0.45 ng/ml in 9 patients with other pituitary diseases. TSH-beta changes after TRH administration differed from TSH changes in 4 patients (25%) with Acromegaly, in 2 patients (67%) with Prolactinoma, in 5 patients (71%) with non-functioning tumor, in one patient (33%) with Cushing's disease, in 4 patients (100%) with Rathke's cleft cyst, in one patient with suprasellar meningioma, and in one patient with suprasellar arachnoid cyst. 2 patients (67%) with Prolactinoma, 3 patients (43%) with non-functioning tumor, all 6 patients with non-neoplastic SITSH, and one patient with Rathke's cleft cyst showed exaggerated TSH-beta changes after TRH administration. In patients with some pituitary disorders, we thought the secretion and synthesis of TSH and TSH-beta differed from that of normal subjects. We concluded that it was necessary to investigate the mechanism of secretion of TSH-beta in patients with pituitary disorders.

[Reevaluation of serum TSH determination in various pituitary disorders using highly sensitive immunoradiometric assay]

In thirty-one patients with various pituitary disorders, their serum TSH levels were reevaluated using two kinds of highly sensitive immunoradiometric assays (IRMAs). TSH levels were measured by radioimmunoassay (RIA) supplied by Daiichi Radioisotope Laboratory and the IRMAs, which were RIA-gnost TSH Ultrasensitive and SUCROSEP TSH IRMA using two types of monoclonal antibodies. The sensitivities of them were 0.08 and 0.1 microU/ml, respectively. Free thyroxine and free triiodothyronine levels were measured by RIAs (Amerlex kits). There was a significant correlation between basal TSH levels and the maximum increase in serum TSH above baseline using the RIA and the IRMAs when responses to TRH (500 micrograms i.v.) was determined, but no correlation between basal TSH and thyroid free hormone levels. In their TRH tests, three patients showed absent responses to TRH which were measured by the RIA, although by the IRMAs slight responses were observed. In two patients, exaggerated responses to TRH were observed and the increase of TSH levels measured by the IRMAs showed 143 approximately 210% higher than that of the RIA. The IRMAs were able to handle their peak levels time in all the patients with responses, however, in some patients the RIA was not sensitive enough to distinguish it. These results indicated that measurement of TSH levels by the IRMAs might be useful in the evaluation of the TSH secretion capacity in patients with various pituitary disorders.