Establishing best practices and guidance in population modeling: an experience with an internal population pharmacokinetic analysis guidance

This tutorial describes the development of a population pharmacokinetic (Pop PK) analysis guidance within Pfizer, which strives for improved consistency and efficiency, and a more systematic approach to model building. General recommendations from the Pfizer internal guidance and a suggested workflow for Pop PK model building are discussed. A description is also provided for mechanisms by which conflicting opinions were captured and resolved across the organization to arrive at the final guidance.

CPT: Pharmacometrics & Systems Pharmacology (2013) 2, e51; doi:10.1038/psp.2013.26; advance online publication 3 July 2013

In vitro chemosensitivity assay of ascites in epithelial ovarian cancer

OBJECTIVE

This study aimed to investigate the predictive value of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for chemosensitivity test in ascites.

MATERIALS AND METHODS

The relationship of the in vitro sensitivity results and the clinicopathological characteristics, objective response rates (ORRs) of chemotherapy, and time to progression (TTP) were retrospectively analyzed in 120 epithelial ovarian cancer (EOC) patients. The clinical response criterion was based on the Response Evaluation Criteria in Solid Tumors (RECIST) standard. The log-rank test and Kaplan-Meier curve were used to estimate TTP.

RESULTS

MTT assays revealed that tumor cells from ascites of primary and type II EOC were more sensitive to paclitaxel (PTX) and carboplatin (CBDCA) than relapse (p = 0.01 and p < 0.01, respectively) and type I (p = 0.03, p = 0.02, respectively) EOC. p53 positive expression and Ki67 high expression were associated with high PTX (p = 0.01 and p < 0.01, respectively) and CBDCA (p = 0.03 and p < 0.01, respectively) sensitivity. Ki67 weak positive immunostaining was associated with topotecan (p < 0.01), gemcitabine (p < 0.01), and doxorubicin (p < 0.01) resistance. Chemosensitivity to CBDCA/PTX was associated with the ORR ofneo-adjuvant (p = 0.03) and adjuvant (p = 0.02) chemotherapy. The MTT assay results of ascites were consistent with the clinical response (p = 0.04) and TTP (p = 0.04) in patients with platinum-resistant relapse EOC tumors.

CONCLUSIONS

Evaluation of the chemosensitivity of ascites in EOC by MTT can aid the establishment of individualized clinical chemotherapeutic plans for platinum-resistant relapse patients.

Cigarette smoke exposure hinders long-term allograft survival by suppressing indoleamine 2, 3-dioxygenase expression

Cigarette smoke causes cancer and increases the vulnerability of smokers to infections. Epidemiologic studies have shown that smoking is one of major risk factors for late allograft rejection. Despite statistical data that associate smoking with allograft rejection, no any study has been conducted to prove that cigarette smoke directly causes allograft rejection in a cause-effect manner. In particular, investigation into immunologic mechanisms underlying smoke-related allograft rejection is lacking. Here we found that second hand smoke (SHS) hindered long-term islet allograft survival induced by CD154 costimulatory blockade plus donor-specific splenocyte transfusion (DST), although it failed to alter acute islet allograft rejection. SHS did not directly interfere with vigorously alloreactive T-cell proliferation in vivo and in vitro. Neither naturally occurring nor induced CD4+CD25+ Treg cell numbers were significantly reduced by SHS. However, SHS suppressed mRNA and protein expression of indoleamine 2, 3-dioxygenase (IDO) and its activity upon transplantation while IDO overexpression in islet allografts restored their long-term survival induced by CD154 blockade. Therefore, SHS prevents long-term allograft survival by inhibiting IDO expression and activity. Thus, our study for the first time demonstrates that SHS shortens allograft survival in a cause-effect manner and unveils a novel immunologic mechanism underlying smoking-related allograft rejection.

In vitro suppression of drug-induced methaemoglobin formation by Intralipid(®) in whole human blood: observations relevant to the 'lipid sink theory'

To provide further evidence for the lipid sink theory, we have developed an in vitro model to assess the effect of Intralipid® 20% on methaemoglobin formation by drugs of varying lipid solubility. Progressively increasing Intralipid concentrations from 4 to 24 mg.ml⁻¹ suppressed methaemoglobin formation by the lipid soluble drug glyceryl trinitrate in a dose-dependent manner (p < 0.001). Both dose and timing of administration of Intralipid to blood previously incubated with glyceryl trinitrate for 10 and 40 min resulted in significant suppression of methaemoglobin formation (p < 0.0001 and p < 0.05, respectively). Mathematical modelling demonstrated that the entire process of methaemoglobin formation by glyceryl trinitrate was slowed down in the presence of Intralipid. Intralipid did not significantly suppress methaemoglobin formation induced by 2-amino-5-hydroxytoluene (partially lipid soluble) or sodium nitrite (lipid insoluble; both p > 0.5). This work may assist determination of the suitability of drugs taken in overdose for which Intralipid might be deployed.

Assessment of lateral geniculate nucleus atrophy with 3T MR imaging and correlation with clinical stage of glaucoma

BACKGROUND AND PURPOSE

Although previous animal studies have shown structural changes in ocular hypertension such as atrophy of the LGN, such changes have not been thoroughly studied in human glaucoma patients nor correlation made with clinical stage. Our aim was to investigate prospectively LGN atrophy in patients with POAG using 3T MR imaging and correlation with the clinical stage of disease.

MATERIALS AND METHODS

Twenty-six patients with known POAG and 26 age-matched healthy volunteers were included in this institutional review board-approved study. All subjects underwent imaging on a 3T MR imaging system with a PD and GM sequence. LGN height and volume were measured by 2 blinded neuroradiologists. Measurements were compared and correlated with clinical glaucoma severity as assessed by static threshold visual field parameters.

RESULTS

Average maximum LGN height in patients with glaucoma on PD images was 4.36 ± 0.61 mm (right) and 4.31 ± 0.61 mm (left), significantly less (P < 10⁻³) than respective measurements of 5.05 ± 0.41 and 4.99 ± 0.41 mm in volunteers. With the GM sequences, such respective measurements were also less (P < 10⁻³) in patients with glaucoma (4.20 ± 0.71 mm right, 4.00 ± 0.85 mm left) versus respective measurements in volunteers (4.88 ± 0.51 mm right, 4.77 ± 0.47 mm left). Average LGN volumes in the patient group were 98.0 ± 27.2 mm³ (right) and 93.7 ± 25.8 mm³ (left) with the PD sequence versus respective measurements of 85.2 ± 27.1 and 80.5 ± 23.6 mm³ with the GM sequence. All height and volume measurements were greater in volunteers (P < 10⁻³). In the patient group, both maximum height and volume of the LGN with both sequences were significantly correlated with cumulative clinical glaucoma stage (P < .05).

CONCLUSIONS

MR imaging measurements of LGN height and volume are diminished in patients with glaucoma, with the extent of atrophy correlating to clinical stage, suggesting a novel imaging marker of disease severity.

Efficacy and safety of the dipeptidyl peptidase-4 inhibitor PF-734200 added to metformin in Type 2 diabetes

AIMS

  PF-734200 is a potent and selective oral dipeptidyl peptidase-4 (DPP-4) inhibitor. This study assessed the efficacy and safety of PF-734200 at dose rates of 20 and 30 mg/day in subjects with Type 2 diabetes mellitus inadequately controlled on metformin monotherapy.

METHODS

  This was a placebo-controlled, double-blind, randomized, multicentre, 12 week study. Subjects with Type 2 diabetes mellitus were eligible if screening glycosylated haemoglobin (HbA(1c) ) was 7-11% (53.0-96.7 mmol/mol) and they had been receiving metformin monotherapy for ≥2 months. Subjects receiving metformin and an insulin secretagogue or metformin and thiazolidinedione needed to have a screening HbA(1c) of 6.5-9.5% (47.5-80.3 mmol/mol), measured prior to discontinuing the insulin secretagogue or thiazolidinedione. The primary end-point of the study was a change from baseline to week 12 in HbA(1c) levels.

RESULTS

  Baseline characteristics for 289 subjects randomized to PF-734200 or placebo groups were similar (mean age 56.5 years, mean body mass index 32.2 kg/m(2) and mean HbA(1c) 8.2%, 66.1 mmol/mol). In the predefined per protocol data set, least-squares mean HbA(1c) at week 12 was reduced by 0.79 (8.6 mmol/mol 95% confidence interval -1.10 to -0.49, -12.0 to -5.4 mmol/mol) and 0.92% (10.1 mmol/mol; -1.23 to -0.61, -13.4 to -6.7 mmol/mol) in the 20 and 30 mg groups, respectively, compared with placebo. Differences from placebo were statistically significant (P<0.0001), but the differences between the 20 and 30 mg groups were not. The intent-to-treat analysis yielded similar findings.

CONCLUSIONS

  The HbA(1c) was significantly and meaningfully reduced by both doses of PF-734200, but 20 mg appears to be the more appropriate therapeutic dose for Type 2 diabetes mellitus, contingent upon confirmation by long-term controlled studies.

Strong impact of acute kidney injury on survival after liver transplantation

Acute kidney injury (AKI) is a major complication in orthotopic liver transplantation (OLT). In an evaluation of Acute Kidney Injury Network (AKIN) criteria in liver transplanted patients, we retrospectively analyzed the usefulness of these criteria to predict survival of 193 consecutive patients at a single center who underwent primary OLT for clinical parameters and peak AKI. Postoperative AKI according to AKIN occurred in 60.1% of the patients, namely, stages 1, 2, and 3 in 30%, 13% and 17.1% respectively. Using multivariate logistic regression, AKIN stage 1 and 2 AKI were independently associated with the pre-OLT Model for End-Stage Liver Disease (MELD) score and age, while stage 3 AKI was independently associated with MELD and Acute Physiology and Chronic Health Evaluation (APACHE) II scores. The 28-day and 1-year mortality post-OLT of AKI patients were 15.5% and 25.9% respectively compared with 0% and 3.9% among non-AKI patients (P < .05 for both). The survival rates of non-AKI and stages 1, 2, and 3 AKI subjects were 96%, 85.5%, 84%, and 45.3%, respectively. Cox regression analysis showed independent risk factors for mortality during the first year after transplantation to include post-OLT AKI (12.1; P < .05), post-OLT infection (HR 4.7; P < .01), pre-OLT hypertension (HR 4.4; P < .01) hazard ratio [HR] and post-OLT APACHE II ≥10 (HR 3.6; P < .05). We concluded that AKI as defined by the AKIN criteria is a major complication of OLT linked to a poor outcomes. It remains to be evaluated whether aggressive perioperative therapy to prevent AKI can improve survival among OLT patients.

Essential roles of Jab1 in cell survival, spontaneous DNA damage and DNA repair

Jun activation domain-binding protein 1 (JAB1) is a multifunctional protein that participates in the control of cell proliferation and the stability of multiple proteins. JAB1 overexpression has been implicated in the pathogenesis of human cancer. JAB1 regulates several key proteins and thereby produces varied effects on cell cycle progression, genome stability and cell survival. However, the biological significance of JAB1 activity in these cellular signaling pathways is unclear. Therefore, we developed mice that were deficient in Jab1 and analyzed the null embryos and heterozygous cells. This disruption of Jab1 in mice resulted in early embryonic lethality due to accelerated apoptosis. Loss of Jab1 expression sensitized both mouse primary embryonic fibroblasts and osteosarcoma cells to γ-radiation-induced apoptosis, with an increase in spontaneous DNA damage and homologous recombination (HR) defects, both of which correlated with reduced levels of the DNA repair protein Rad51 and elevated levels of p53. Furthermore, the accumulated p53 directly binds to Rad51 promoter, inhibits its activity and represents a major mechanism underlying the HR repair defect in Jab1-deficient cells. These results indicate that Jab1 is essential for efficient DNA repair and mechanistically link Jab1 to the maintenance of genome integrity and to cell survival.

Autism spectrum disorder is related to endoplasmic reticulum stress induced by mutations in the synaptic cell adhesion molecule, CADM1

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with an unknown molecular pathogenesis. A recent molecular focus has been the mutated neuroligin 3, neuroligin 3(R451C), in gain-of-function studies and for its role in induced impairment of synaptic function, but endoplasmic reticulum (ER) stress induced by mutated molecules also deserves investigation. We previously found two missense mutations, H246N and Y251S, in the gene-encoding synaptic cell adhesion molecule-1 (CADM1) in ASD patients, including cleavage of the mutated CADM1 and its intracellular accumulation. In this study, we found that the mutated CADM1 showed slightly reduced homophilic interactions in vitro but that most of its interactions persist. The mutated CADM1 also showed morphological abnormalities, including shorter dendrites, and impaired synaptogenesis in neurons. Wild-type CADM1 was partly localized to the ER of C2C5 cells, whereas mutated CADM1 mainly accumulated in the ER despite different sensitivities toward 4-phenyl butyric acid with chemical chaperone activity and rapamycin with promotion activity for degradation of the aggregated protein. Modeling analysis suggested a direct relationship between the mutations and the conformation alteration. Both mutated CADM1 and neuroligin 3(R451C) induced upregulation of C/EBP-homologous protein (CHOP), an ER stress marker, suggesting that in addition to the trafficking impairment, this CHOP upregulation may also be involved in ASD pathogenesis.

Con-specific neighbours may enhance compensation capacity in an invasive plant

Facilitation, both by inter- and intra-specific neighbours, is known to be an important process in structuring plant communities. However, only a small number of experiments have been reported on facilitation in plant invasions, especially between invasive con-specific individuals. Here, we focus on how con-specific neighbours of the invasive alien plant alligator weed affect the tolerance of alligator weed to herbivory by the introduced biological control agent, Agasicles hygrophila. We conducted greenhouse and garden experiments in which invasive plant density and herbivory intensity (artificial clipping and real herbivory) were manipulated. In the greenhouse experiment, artificial clipping significantly reduced plant biomass when plants were grown individually, but when con-specific neighbours were present in the same pot, biomass was not significantly different from control plants. Similarly, when compared to control plants, plants that were subjected to herbivory by A. hygrophila produced more biomass when grown with two con-specific neighbours than when grown alone. Real herbivory also resulted in an increased number of vegetative buds, and again when two con-specific neighbours were present this effect was increased (a 55.3% increase in buds when there was no neighbour, but a 111.6% increase in buds when two con-specific neighbours were present). In the garden experiment, in which plants were grown at high density (6 plants per pot), alligator weed fully recovered from defoliation caused by insects at levels from 20-30% to 100%. Our results indicate that the con-specific association may increase the compensatory ability to cope with intense damage in this invasive plant.

Elevated levels of serum antibodies against Saccharomyces cerevisiae mannan in patients with systemic lupus erythematosus

This study was undertaken to investigate whether levels of anti- Saccharomyces cerevisiae mannan antibodies (ASCMAs), a serological marker for Crohn’s disease, seronegative spondyloarthritis and Behcet’s disease, also correlate with systemic lupus erythematosus (SLE) in humans. Serum samples from healthy volunteers ( n = 152) and patients with SLE ( n = 40) were compared for ASCMA-IgA, -IgG and -IgM levels using enzyme linked immunosorbent assays. ASCMA-IgG, but not IgM and IgA, prevalence was significantly raised in active SLE patients (57.5%) compared with healthy controls (8.5%). ASCMA-IgG levels in SLE patients during remission were relatively lower, indicating a possible correlation with disease activity. These results differ from a previous study, which did not detect a difference between ASCMA levels in SLE patients and healthy control. It remains to be evaluated whether elevated ASCMA-levels are common to all rheumatic disorders.