The Unfinished Business of US Drug Safety Regulation

Posted with permission from FDLI ; Food and Drug Law Journal Various proposals have been advanced in response to recent problems with the safety of Food and Drug Administration (FDA)-approved drugs. Many call for incremental change, such as new safety oversight bodies or minor expansions of FDA's existing powers. "Fixing" FDA may not fix the problem, without related reform of the broader legal framework in which FDA operates. Key reform challenges include promoting clinical compliance with important safety warnings while preserving needed flexibility for physicians to adapt drug use to the individual patient; developing a clearer distinction between pre- and postapproval safety regulation; and devising mechanisms for funding investments in safety improvements. Until these fundamental problems are addressed, the United States will face ongoing problems with drug safety and patients will be denied the full measure of safety and therapeutic benefit that today's technologies could support. This article proposes a new direction to address these problems in the context of an insurance-based framework for promoting drug safety

Is personalized medicine achievable in obstetrics?

Personalized medicine seeks to identify the right dose of the right drug for the right patient at the right time. Typically, individualization of therapy is based on the pharmacogenomic makeup of the individual and environmental factors that alter drug disposition and response. In addition to these factors, during pregnancy, a woman's body undergoes many changes that can impact the therapeutic efficacy of medications. Yet, there is minimal research regarding personalized medicine in obstetrics. Adoption of pharmacogenetic testing into the obstetrical care is dependent on evidence of analytical validity, clinical validity, and clinical utility. Here, we briefly present information regarding the potential utility of personalized medicine for treating the obstetric patient for pain with narcotics, hypertension, and preterm labor, and discuss the impediments of bringing personalized medicine to the obstetrical clinic

Stereoselective pharmacokinetics of stable isotope (+/-)-[13C]-pantoprazole: Implications for a rapid screening phenotype test of CYP2C19 activity

AIMS: We have previously shown that the (±)-[(13) C]-pantoprazole breath test is a promising noninvasive probe of CYP2C19 activity. As part of that trial, plasma, breath test indices and CYP2C19 (*2, *3, and *17) genotype were collected. Here, we examined whether [(13) C]-pantoprazole exhibits enantioselective pharmacokinetics and whether this enantioselectivity is correlated with indices of breath test. METHODS: Plasma (-)- and (+)-[(13) C]-pantoprazole that were measured using a chiral HPLC were compared between CYP2C19 genotypes and correlated with breath test indices. RESULTS: The AUC( 0-∞) of (+)-[(13) C]-pantoprazole in PM (*2/*2, n = 4) was 10.1- and 5.6-fold higher that EM (*1/*1or *17, n = 10) and IM (*1/*2or *3, n = 10) of CYP2C19, respectively (P < 0.001). The AUC( 0-∞) of (-)-[(13) C]-pantoprazole only significantly differed between PMs and EMs (1.98-fold; P = 0.05). The AUC( 0-∞) ratio of (+)-/(-)-[(13) C]-pantoprazole was 3.45, 0.77, and 0.67 in PM, IM, and EM genotypes, respectively. Breath test index, delta over baseline show significant correlation with AUC( 0-∞) of (+)-[(13) C]-pantoprazole (Pearson's r = 0.62; P < 0.001). CONCLUSIONS: [(13) C]-pantoprazole exhibits enantioselective elimination. (+)-[(13) C]-pantoprazole is more dependent on CYP2C19 metabolic status and may serve as a more attractive probe of CYP2C19 activity than (-)-[(13) C]-pantoprazole or the racemic mixture

Differential quantification of CYP2D6 gene copy number by four different quantitative real-time PCR assays

Copy number variations (CNVs) in the CYP2D6 gene contribute to interindividual variation in drug metabolism. As the most common duplicated allele in Asian populations is the nonfunctional CYP2D6*36 allele, the goal of this study was to identify CNV assays that can differentiate between multiple copies of the CYP2D6*36 allele and multiple copies of other CYP2D6 alleles. We determined CYP2D6 gene copy numbers in 32 individuals with known CYP2D6 CNVs from the Coriell Japanese-Chinese panel using four quantitative real-time PCR assays. These assays target different regions of the CYP2D6 gene: 5'-flanking region, intron 2, intron 6, and exon 9 (Ex9). The specific target site of the Ex9 assay was verified by sequencing the PCR amplicon. Three of the CYP2D6 CNV assays (5'-flanking region, intron 2, and intron 6) estimated CYP2D6 copy numbers that were concordant for all 32 individuals. However, the Ex9 assay was concordant in only 10 of 32 samples. The 10 concordant samples did not contain any CYP2D6*36 alleles and the 22 discordant samples contained at least one CYP2D6*36 allele. In addition, the Ex9 assay accurately quantified all of the non-CYP2D6*36 alleles in all samples. Ex9 amplicon sequencing indicated that it targets a region of CYP2D6 exon 9 that undergoes partial gene-conversion in the CYP2D6*36 allele. In conclusion, CYP2D6 Ex9 CNV assay can be used to determine the copy number of non-CYP2D6*36 alleles. Selective amplification of non-CYP2D6*36 sequence by the Ex9 assay should be useful in determining the number of functional copies of CYP2D6 in Asian populations

Steroid Pathway Genes and Neonatal Respiratory Distress After Betamethasone Use in Anticipated Preterm Birth

Objective: To test several key glucocorticoid genes that are enhanced in lung development for associations with respiratory distress syndrome (RDS) after antenatal corticosteroid use. Methods: A prospective cohort of women received betamethasone to accelerate fetal lung maturity for threatened preterm delivery. DNA was obtained from mothers and newborns. Neonatal RDS was the primary outcome. Genotyping for single-nucleotide polymorphisms (SNPs) in 68 glucocorticoid genes found to be differentially expressed during lung development was performed. Multivariable analysis tested for associations of SNPs in the candidate genes with RDS. Results: Genotypic results for 867 SNPs in 96 mothers and 73 babies were included. Thirty-nine (53.4%) babies developed RDS. Maternal SNPs in the centromeric protein E (CENPE), GLRX, CD9, and AURKA genes provided evidence of association with RDS (P < .01). In newborns, SNPs in COL4A3, BHLHE40, and SRGN provided evidence of association with RDS (P < .01). Conclusion: Single-nucleotide polymorphisms in several glucocorticoid responsive genes suggest association with neonatal RDS after antenatal corticosteroid use

Simultaneous administration of high-dose atorvastatin and clopidogrel does not interfere with platelet inhibition during percutaneous coronary intervention

BACKGROUND: Reloading with high-dose atorvastatin shortly before percutaneous coronary interventions (PCIs) has been proposed as a strategy to reduce periprocedural myonecrosis. There has been a concern that statins that are metabolized by cytochrome P450 3A4 may interfere with clopidogrel metabolism at high doses. The impact of simultaneous administration of high doses of atorvastatin and clopidogrel on the efficacy of platelet inhibition has not been established. METHODS: Subjects (n=60) were randomized to receive atorvastatin 80 mg together with clopidogrel 600 mg loading dose (n=28) versus clopidogrel 600 mg alone (n=32) at the time of PCI. Platelet aggregation was measured at baseline, 4 hours after clopidogrel loading dose, and 16-24 hours after clopidogrel loading dose by light transmittance aggregometry using adenosine diphosphate as agonist. RESULTS: Platelet aggregation was similar at baseline in both the atorvastatin and the control groups (adenosine diphosphate 10 µM: 57%±19% vs 61%±21%; P=0.52). There was no significant difference in platelet aggregation between the atorvastatin and the control groups at 4 hours (37%±18% vs 39%±21%; P=0.72) and 16-24 hours post-clopidogrel loading dose (35%±17% vs 37%±18%; P=0.75). No significant difference in incidence of periprocedural myonecrosis was observed between the atorvastatin and control groups (odds ratio: 1.02; 95% confidence interval 0.37-2.8). CONCLUSION: High-dose atorvastatin given simultaneously with clopidogrel loading dose at the time of PCI does not significantly alter platelet inhibition by clopidogrel. Statin reloading with high doses of atorvastatin at the time of PCI appears to be safe without adverse effects on platelet inhibition by clopidogrel (ClinicalTrials.gov: NCT00979940)

Synthesis of Triphenylethylene Bisphenols as Aromatase Inhibitors that Also Modulate Estrogen Receptors

A series of triphenylethylene bisphenol analogues of the selective estrogen receptor modulator (SERM) tamoxifen were synthesized and evaluated for their abilities to inhibit aromatase, bind to estrogen receptor α (ER-α) and estrogen receptor β (ER-β), and antagonize the activity of β-estradiol in MCF-7 human breast cancer cells. The long-range goal has been to create dual aromatase inhibitor (AI)/selective estrogen receptor modulators (SERMs). The hypothesis is that in normal tissue the estrogenic SERM activity of a dual AI/SERM could attenuate the undesired effects stemming from global estrogen depletion caused by the AI activity of a dual AI/SERM, while in breast cancer tissue the antiestrogenic SERM activity of a dual AI/SERM could act synergistically with AI activity to enhance the antiproliferative effect. The potent aromatase inhibitory activities and high ER-α and ER-β binding affinities of several of the resulting analogues, together with the facts that they antagonize β-estradiol in a functional assay in MCF-7 human breast cancer cells and they have no E/Z isomers, support their further development in order to obtain dual AI/SERM agents for breast cancer treatment

Influence of Oral Progesterone Administration on Drug-Induced QT Interval Lengthening: A Randomized, Double-Blind, Placebo-Controlled Crossover Study

Objectives We tested the hypothesis that oral progesterone administration attenuates drug-induced QT interval lengthening. Background Evidence from preclinical and human investigations suggests that higher serum progesterone concentrations may be protective against drug-induced QT interval lengthening. Methods In this prospective, double-blind, crossover study, 19 healthy female volunteers (21-40 years) were randomized to receive progesterone 400 mg or matching placebo orally once daily for 7 days timed to the menses phase of the menstrual cycle (between-phase washout period = 49 days). On day 7, ibutilide 0.003 mg/kg was infused over 10 minutes, after which QT intervals were recorded and blood samples collected for 12 hours. Prior to the treatment phases, subjects underwent ECG monitoring for 12 hours to calculate individualized heart rate-corrected QT intervals (QTcI). Results Fifteen subjects completed all study phases. Maximum serum ibutilide concentrations in the progesterone and placebo phases were similar (1247±770 vs 1172±709 pg/mL, p=0.43). Serum progesterone concentrations were higher during the progesterone phase (16.2±11.0 vs 1.2±1.0 ng/mL, p<0.0001), while serum estradiol concentrations in the two phases were similar (89.3±62.8 vs 71.8±31.7 pg/mL, p=0.36). Pre-ibutilide lead II QTcI was significantly lower in the progesterone phase (412±15 vs 419±14 ms, p=0.04). Maximum ibutilide-associated QTcI (443±17 vs 458±19 ms, p=0.003), maximum percent increase in QTcI from pretreatment value (7.5±2.4 vs 9.3±3.4%, p=0.02) and area under the effect (QTcI) curve during the first hour post-ibutilide (497±13 vs 510±16 ms-hr, p=0.002) were lower during the progesterone phase. Progesterone-associated adverse effects included fatigue/malaise and vertigo. Conclusions Oral progesterone administration attenuates drug-induced QTcI lengthening