Acute changes in colonic PGE2 levels as a biomarker of efficacy after treatment of the Pirc (F344/NTac-Apc am1137) rat with celecoxib.

OBJECTIVE: This study sought to evaluate short-term treatment with COX-2 inhibitors and acute changes in colonic PGE2 levels as predictors of long-term efficacy in a genetic model of colorectal cancer. METHODS: Celecoxib oral suspension (40 mg/kg BID) was dosed to Apc-mutant Pirc (F344/NTac-Apcam1137) rats for 4 days (short-term group), or the equivalent dose of 1500 ppm celecoxib was administered in the diet for 4 months (long-term group). Percent inhibition of colonic PGE2 was calculated, and the reduction in colonic PGE2 was assessed in relation to suppression of adenomatous colon polyps. RESULTS: Colonic mucosa PGE2 was fourfold higher in Pirc than in F344 wild-type rats (21 vs. 5.6 pg/mg epithelial tissue), due at least in part to higher COX-2 expression, and this was confirmed by elevated PGE2-d11 levels in Pirc colonic S9 incubations. In the 4-day study, dose-dependent reductions in PGE2 were observed in colonic epithelium (-33% (P>0.05) and -57% (P=0.0012)), after low- and high-dose celecoxib treatments of 4 mg/kg and 40 mg/kg (bid), respectively. In the 4-month study, 1500 ppm celecoxib suppressed colonic epithelium PGE2 by 43.5%, and tumor multiplicity by 80% (P<0.0015). Suppression of plasma 6-keto PGF1α also was corroborated following long-term treatment with 1500 ppm celecoxib (P<0.05). CONCLUSIONS: Acute changes in colonic mucosa PGE2 provided a rapid means of predicting long-term chemopreventive effects from celecoxib, and might be useful for screening of new COX-2 inhibitor compounds.

Glucuronidation: driving factors and their impact on glucuronide disposition.

Glucuronidation is a well-recognized phase II metabolic pathway for a variety of chemicals including drugs and endogenous substances. Although it is usually the secondary metabolic pathway for a compound preceded by phase I hydroxylation, glucuronidation alone could serve as the dominant metabolic pathway for many compounds, including some with high aqueous solubility. Glucuronidation involves the metabolism of parent compound by UDP-glucuronosyltransferases (UGTs) into hydrophilic and negatively charged glucuronides that cannot exit the cell without the aid of efflux transporters. Therefore, elimination of parent compound via glucuronidation in a metabolic active cell is controlled by two driving forces: the formation of glucuronides by UGT enzymes and the (polarized) excretion of these glucuronides by efflux transporters located on the cell surfaces in various drug disposition organs. Contrary to the common assumption that the glucuronides reaching the systemic circulation were destined for urinary excretion, recent evidences suggest that hepatocytes are capable of highly efficient biliary clearance of the gut-generated glucuronides. Furthermore, the biliary- and enteric-eliminated glucuronides participate into recycling schemes involving intestinal microbes, which often prolong their local and systemic exposure, albeit at low systemic concentrations. Taken together, these recent research advances indicate that although UGT determines the rate and extent of glucuronide generation, the efflux and uptake transporters determine the distribution of these glucuronides into blood and then to various organs for elimination. Recycling schemes impact the apparent plasma half-life of parent compounds and their glucuronides that reach intestinal lumen, in addition to prolonging their gut and colon exposure.

Systematic Review of Device Parameters and Design of Studies Bridging Biologic-Device Combination Products Using Prefilled Syringes and Autoinjectors.

Biologic-device combination products using prefilled syringes (PFSs) and autoinjectors (AIs) are popular for biological products administered subcutaneously. Pharmacokinetic (PK) comparability studies commonly provide the scientific data to support introduction of AI presentations via bridging with PFS. A survey of biological products approved by FDA's Center for Drug Evaluation and Research identified 17 biologics license applications (BLAs) with both PFS and AI presentations for subcutaneous (SC) administration, including 16 approved on February 1, 2018, and one with AI presentation under review. A systematic review on the device parameters and the PK comparability studies bridging the two presentations was conducted. Subsequently, whether device parameters or the PK study design may have influenced the PK comparability study results was evaluated. The reported device parameters for AI and PFS are generally consistent across BLAs, whereas the approach to assess PK comparability varied, including the study design. Most PK comparability studies met bioequivalence (BE) criteria. Upon inspection of the studies that did not meet BE criteria, injection depth of AI and the injection site for either AI or PFS were identified as potential influencing factors to the outcome of PK comparability study. This study represents an initial attempt to identify the potential influencing factors on device bridging, including the characteristics of the device and the clinical pharmacology study. These findings may inform the combination product development strategy, specifically design considerations for device and PK comparability studies.

Determination of 7α-OH cholesterol by LC-MS/MS: Application in assessing the activity of CYP7A1 in cholestatic minipigs.

An LC-MS/MS method was developed and validated to determine 7α-OH cholesterol in liver microsome. This method was convenient and fast with high specificity and sensitivity. Briefly, a gradient elution was performed on a Synergi polar-C18 column (50×4.6mm i.d., 3µm). The mobile phase (consisting of 0.1% HCOOH solution and acetonitrile) eluted in gradient at a flow rate of 1ml/min. MS detection was operated on APCI (+) mode; the MRM transitions for 7α-OH cholesterol and D7-cholesterol (I.S.) were 385.1≥159.1 and 376.4≥266.3, respectively. The linear response range of 7α-OH cholesterol was covered from 1.563 to 100.0ng/ml. All of the validation items meet the requirement of FDA guidance for bioanalytical method validation. This method was applied to enzymatic studies for determination of cholesterol 7alpha-hydroxylation activity catalyzed by CYP7A1 in the cholestatic minipigs liver microsomes.