Durable pharmacological responses from the peptide ShK-186, a specific Kv1.3 channel inhibitor that suppresses T cell mediators of autoimmune disease.

The Kv1.3 channel is a recognized target for pharmaceutical development to treat autoimmune diseases and organ rejection. ShK-186, a specific peptide inhibitor of Kv1.3, has shown promise in animal models of multiple sclerosis and rheumatoid arthritis. Here, we describe the pharmacokinetic-pharmacodynamic relationship for ShK-186 in rats and monkeys. The pharmacokinetic profile of ShK-186 was evaluated with a validated high-performance liquid chromatography-tandem mass spectrometry method to measure the peptide's concentration in plasma. These results were compared with single-photon emission computed tomography/computed tomography data collected with an ¹¹¹In-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-conjugate of ShK-186 to assess whole-blood pharmacokinetic parameters as well as the peptide's absorption, distribution, and excretion. Analysis of these data support a model wherein ShK-186 is absorbed slowly from the injection site, resulting in blood concentrations above the Kv1.3 channel-blocking IC50 value for up to 7 days in monkeys. Pharmacodynamic studies on human peripheral blood mononuclear cells showed that brief exposure to ShK-186 resulted in sustained suppression of cytokine responses and may contribute to prolonged drug effects. In delayed-type hypersensitivity, chronic relapsing-remitting experimental autoimmune encephalomyelitis, and pristane-induced arthritis rat models, a single dose of ShK-186 every 2 to 5 days was as effective as daily administration. ShK-186's slow distribution from the injection site and its long residence time on the Kv1.3 channel contribute to the prolonged therapeutic effect of ShK-186 in animal models of autoimmune disease.

p53 heterozygosity alters the mRNA expression of p53 target genes in the bone marrow in response to inhaled benzene.

C57BL/6 Trp53 heterozygous (N5) mice (p53+/- mice) show an increased sensitivity to tumorigenesis following exposure to genotoxic compounds and are being used as an alternate animal model for carcinogenicity testing. However, there is relatively little data regarding the effect of p53 heterozygosity on the genomic and cellular responses of target tissues in these mice to toxic insult, especially under chronic exposure conditions used in carcinogenicity bioassays. We hypothesized that heterozygosity at the p53 locus in p53+/- mice alters the expression of bone marrow p53-regulated genes involved in cell cycle control and apoptosis during chronic genotoxic stress. We used real-time quantitative reverse transcription polymerase chain reaction (RT-PCR) to examine gene expression alterations in bone marrow cells from C57BL/6 p53+/+ and isogenic p53+/- mice chronically exposed for 15 weeks to genotoxic and carcinogenic levels (100 ppm) of inhaled benzene. Examination of mRNA levels of p53-regulated genes involved in cell cycle control (p21, gadd45, and cyclin G) or apoptosis (bax and bcl-2) showed that during chronic genotoxic stress, bone marrow cells from p53+/+ mice expressed significantly higher levels of a majority of these genes compared to p53+/- bone marrow cells. Our results indicate that p53 heterozygosity results in a haploinsufficient phenotype in p53+/- bone marrow cells as evident by significantly altered mRNA levels of key genes involved in the p53-regulated DNA damage response pathway.

Carcinogenicity and chronic rodent toxicity of the selective progesterone receptor modulator ulipristal acetate.

Carcinogenic properties of ulipristal acetate (UPA), a selective progesterone receptor modulator developed for the treatment of benign gynecological conditions such as uterine fibroids, were assessed in a 26-week carcinogenicity study in transgenic TgRasH2 mice and a 104-week study in Sprague Dawley rats. Dose levels used in the mouse study were 15, 45, or 130 mg/kg/day and for the ratstudy the doses used were 1, 3, or 10 mg/kg/day. Vehicle and water controls were part of both studies and a positive control, N-Nitroso-N-methylurea intraperitoneally, was included in the transgenic mouse assay. Survival at all dose levels was similar to vehicle controls in both sexes of both species and there was no evidence of any UPA-induced carcinogenicity in either species. Rats receiving UPA had decreased incidences of fibroadenomas and adenocarcinomas in the mammary gland in all treated groups. UPA exposure [AUC(0-24h)] at the highest dose in rats was 67 times human therapeutic exposure at 10 mg/day. In mice, no tumor of any type increased at UPA exposures up to 313 times of therapeutic exposure. UPA-related findings in mice were limited to organ weight changes in the liver, pituitary, thyroid/parathyroid glands, and epididymis as well as minimal panlobular hepatocellular hypertrophy in male and female mice receiving 130 mg/kg/day. Rats had UPA-related non-neoplastic findings in the reproductive system (mammary gland, ovary, uterus, vagina, seminal vesicle, prostate), endocrine system (adrenal, pituitary), thymus, muscle, liver, pancreas and lungs most of which are considered to be due to exaggerated pharmacological action of the compound.