Evaluation of drug-drug interaction between the novel cPLA2 inhibitor AK106-001616 and methotrexate in rheumatoid arthritis patients.

1. Drug interaction potential between AK106-001616, a novel cytosolic phospholipase A2 inhibitor, and methotrexate (MTX) in rheumatoid arthritis patients was investigated. This trial is registered with ClinicalTrials.gov, number NCT00902369. 2. In the clinical study, the 90% confidence intervals (CIs) for the geometric mean ratio (GMR) of AUC0-t of MTX administered after AK106-001616 200 mg compared to the MTX without AK106-001616 were within 80-125%. However, administration of AK106-001616 at doses of 400 and 600 mg exceeded the 125% threshold. As small but statistically significant increases in AUC0-t were observed, we investigated the mechanism for this drug-drug interaction between MTX and AK106-001616. 3. In vitro, AK106-001616 inhibited OAT1 (IC50 = 18.4 µM, Ki = 33.6 µM) in a non-competitive manner and OAT3 (IC50 = 1.80 µM, Ki = 1.49 µM) in a competitive manner. Both transporters are involved in MTX transport in renal proximal tubules. 4. AK106-001616 has a weak drug interaction with MTX. In vitro studies provide a mechanistic understanding of the in vivo inhibition of transporters by AK106-001616.

A simple method to evaluate reactivity of acylglucuronides optimized for early stage drug discovery.

Drugs containing the carboxylic functional group can be metabolized to form acylglucuronides believed to cause idiosyncratic drug toxicity when the acylglucuronide is unstable. Recent studies have shown that the half-life of an acylglucuronide in phosphate buffer is the best means for classifying acylglucuronides into safe, warning, and withdrawn drugs. However, it is difficult to halt the late stage development of new chemical entities due to the instability of their acylglucuronides. We report an optimized in vitro method for determining the half-lives of acylglucuronides in simple phosphate buffer without the need for authentic standards. The experiment was divided into two incubations. In the first incubation, acylglucuronide was synthesized by human liver microsomes, and in the second incubation, the degradation rate of acylglucuronide in phosphate buffer was determined. The degradation rate constants of acylglucuronides were determined from changes in the LC-MS/MS peak area and the half-lives were calculated. We evaluated the half-lives of 10 drugs: 3 safe drugs (telmisartan, gemfibrozil and flufenamic acid) and 7 withdrawn or warning drugs (zomepirac, diclofenac, furosemide, ibuprofen, S-naproxen, probenecid and tolmetin). The half-lives of the 3 safe drugs were 10.6 h or longer, whereas the half-lives of the 7 withdrawn or warning drugs were 4.0 h or shorter. Although authentic acylglucuronide standards were not used, we obtained half-lives of acylglucuronides in phosphate buffer similar to those reported previously. Using this method, the risk of reactivity caused by acylglucuronides can be evaluated in the early stages of drug discovery.

Osteosarcoma in Sprague-Dawley rats after long-term treatment with teriparatide (human parathyroid hormone (1-34)).

Teriparatide, a therapeutic agent for osteoporosis, has been reported to increase the incidences of bone neoplasms such as osteosarcoma when administered subcutaneously to Fischer 344 (F344) rats for a long term, but its non-carcinogenic dose level following 2-year daily administration has not been established. Here we report detailed studies on the carcinogenicity of teriparatide following long-term administration. When teriparatide was administered subcutaneously to male and female Sprague-Dawley (SD) rats daily for 2 years, the incidence of osteosarcoma was increased at 13.6 µg/kg/day. The non-carcinogenic dose level was 4.5 µg/kg/day for both males and females. The development of osteosarcoma in SD rats depends on the dose level of, and treatment duration with, teriparatide. Responses of the bones to teriparatide were similar between F344 and SD rats in many aspects. These results suggested that the carcinogenic potential of teriparatide in SD rats is essentially the same as in F344 rats.

The role of the liver and kidneys in the pharmacokinetics of subcutaneously administered teriparatide acetate in rats.

Teriparatide acetate, a synthetic polypeptide fragment consisting of human parathyroid hormone residues 1-34 [hPTH(1-34)], is a bone anabolic agent used to treat osteoporosis. The present study was conducted to characterise the pharmacokinetics of teriparatide acetate in rats after subcutaneous administration. Teriparatide was rapidly absorbed into the circulation and eliminated immediately. No intact teriparatide was detected in the urine. To elucidate the mechanism of teriparatide metabolism, we performed in vivo and in vitro studies using the radiolabelled bioactive analogue, [(125)I]-[Nle(8,18),Tyr(34)]-hPTH(1-34). After subcutaneous administration, the concentration of analogue metabolites increased in the plasma time-dependently. The concentration in the kidneys was more than 3-fold the concentration in the liver. In vitro analyses suggested that kidney radioactivity was associated with degraded bioactive analogue. In model rats, renal failure, but not hepatic failure, affected the pharmacokinetics of teriparatide acetate, which accounted for the decrease in the clearance of teriparatide. In conclusion, our results suggest that after subcutaneous administration of teriparatide acetate, teriparatide is rapidly absorbed and distributed to the liver or kidneys, where it is immediately degraded. The kidneys play a particularly important role in the distribution and metabolism of teriparatide, but not its excretion.

Collaborative work on evaluation of ovarian toxicity. 13) Two- or four-week repeated dose studies and fertility study of PPAR alpha/gamma dual agonist in female rats.

The main focus of this study was to determine the optimal dosing period in a repeated dose toxicity study based on toxic effects as assessed by ovarian morphological changes. To assess morphological and functional changes induced in the ovary by a peroxisome proliferator-activated receptor (PPAR) alpha/gamma dual agonist, the compound was administered to female rats at dose levels of 0, 4, 20, and 100 mg/kg/day in a repeated dose toxicity study for 2 or 4 weeks, and from 2 weeks prior to mating to Day 7 of pregnancy in a female fertility study. In the repeated dose toxicity study, an increase in atresia of large follicles, a decrease in corpora lutea, and an increase in stromal cells were observed in the treated groups. In addition, the granulosa cell exfoliations into antrum of large follicles and corpora lutea with retained oocyte are morphological characteristics induced by this compound, and they might be related with abnormal condition of ovulation. In the female fertility study, the pregnancy rate tended to decrease in the 100 mg/kg/day group. At necropsy, decreases in the number of corpora lutea, implantations and live embryos were noted in the 20 and 100 mg/kg/day group. No changes were observed in animals given 4 mg/kg/day. These findings indicated that histopathological changes in the ovary are important endpoints for evaluation of drugs inducing ovarian damage. In conclusion, a 2-week administration period is sufficient to detect ovarian toxicity of this test compound in the repeated dose toxicity study.