Jeremiah D. Momper

The impact of conversion from prograf to generic tacrolimus in liver and kidney transplant recipients with stable graft function.

Bioequivalence of the recently available generic tacrolimus formulation, manufactured by Sandoz, to the reference product (Prograf; Astellas Pharma, Tokyo, Japan) has been demonstrated in healthy subjects. However, the safety and efficacy of substitution with generic tacrolimus in transplant patients have not been evaluated. Tacrolimus trough concentrations and indices of liver and kidney function were recorded before and after generic substitution in 48 liver and 55 kidney transplant recipients. In liver transplant patients, the mean tacrolimus concentration/dose (C/D) ratio (±SD) was 184.1 (±123.2) ([ng/mL]/[mg/kg/day]) for the reference product and 154.7 (±87.8) ([ng/mL]/[mg/kg/day]) for the generic product (p < 0.05). The mean C/D‐ratios in kidney transplant patients were 125.3 (±92.7) and 110.4 (±79.2) ([ng/mL]/[mg/kg/day]) for the reference and generic products, respectively (p < 0.05). Actual trough concentrations declined by an average of 1.98 ng/mL in liver and 0.87 ng/mL in kidney transplant patients following the switch, after accounting for all significant covariates. No change was observed in biochemical indices of liver or kidney function and no cases of acute rejection occurred following the substitution. These results suggest that transplant patients currently taking the reference tacrolimus formulation may be safely switched to the Sandoz‐generic product provided trough concentrations are closely monitored following the substitution.

Adolescent Dosing and Labeling Since the Food and Drug Administration Amendments Act of 2007

IMPORTANCE During pediatric drug development, dedicated pharmacokinetic studies are generally performed in all relevant age groups to support dose selection for subsequent efficacy trials. To our knowledge, no previous assessments regarding the need for an intensive pharmacokinetic study in adolescents have been performed. OBJECTIVES To compare U.S. Food and Drug Administration (FDA)-approved adult and adolescent drug dosing and to assess the utility of allometric scaling for the prediction of drug clearance in the adolescent population. DESIGN Adult and adolescent dosing and drug clearance data were obtained from FDA-approved drug labels and publicly available databases containing reviews of pediatric trials submitted to the FDA. Dosing information was compared for products with concordant indications for adolescent and adult patients. Adolescent drug clearance was predicted from adult pharmacokinetic data by using allometric scaling and compared with observed values. MAIN OUTCOMES AND MEASURES Adolescent and adult dosing information and drug clearance. RESULTS There were 126 unique products with pediatric studies submitted to the FDA since the FDA Amendments Act of 2007, of which 92 had at least 1 adolescent indication concordant with an adult indication. Of these 92 products, 87 (94.5%) have equivalent dosing for adults and adolescent patients. For 18 of these 92 products, a minimum weight or body surface area threshold is recommended for adolescents to receive adult dosing. Allometric scaling predicted adolescent drug clearance with an overall mean absolute percentage error of 17.0%. CONCLUSIONS AND RELEVANCE Approved adult and adolescent drug dosing is equivalent for 94.5% of products with an adolescent indication studied since the FDA Amendments Act of 2007. Allometric scaling may be a useful tool to avoid unnecessary dedicated pharmacokinetic studies in the adolescent population during pediatric drug development, although each development program in adolescents requires a full discussion of drug dosing with the FDA.

Consensus recommendations for systematic evaluation of drug-drug interaction evidence for clinical decision support.

BackgroundHealthcare organizations, compendia, and drug knowledgebase vendors use varying methods to evaluate and synthesize evidence on drug–drug interactions (DDIs). This situation has a negative effect on electronic prescribing and medication information systems that warn clinicians of potentially harmful medication combinations.ObjectiveThe aim of this study was to provide recommendations for systematic evaluation of evidence for DDIs from the scientific literature, drug product labeling, and regulatory documents.MethodsA conference series was conducted to develop a structured process to improve the quality of DDI alerting systems. Three expert workgroups were assembled to address the goals of the conference. The Evidence Workgroup consisted of 18 individuals with expertise in pharmacology, drug information, biomedical informatics, and clinical decision support. Workgroup members met via webinar 12 times from January 2013 to February 2014. Two in-person meetings were conducted in May and September 2013 to reach consensus on recommendations.ResultsWe developed expert consensus answers to the following three key questions. (i) What is the best approach to evaluate DDI evidence? (ii) What evidence is required for a DDI to be applicable to an entire class of drugs? (iii) How should a structured evaluation process be vetted and validated?ConclusionEvidence-based decision support for DDIs requires consistent application of transparent and systematic methods to evaluate the evidence. Drug compendia and clinical decision support systems in which these recommendations are implemented should be able to provide higher-quality information about DDIs.

Failed Pediatric Drug Development Trials

Pediatric product development initiatives have stimulated the development of therapies for children, resulting in improved product labeling, increased identification of adverse events, and development of new pediatric formulations. However, 42% of recently completed pediatric trials have failed to establish either safety or efficacy, leading to an inability to label the product for use in children.1 Characterizing these failed trials, including common contributing factors, is imperative to designing better pediatric trials in the future.

Therapeutic Drug Monitoring as a Component of Personalized Medicine: Applications in Pediatric Drug Development

Therapeutic drug monitoring (TDM) is foundational to the concept of personalized medicine. TDM transformed drug therapy by affording the ability to characterize sources of variability in drug disposition and response to individualize drug dosing. Initially, TDM formed the key conceptual basis for personalized medicine, which has evolved to include pharmacogenomic and other biomarker‐driven strategies for patient segmentation. Currently, TDM is an attractive option for personalized medicine and, under the right conditions, can facilitate drug development.

Genetics-Based Pediatric Warfarin Dosage Regimen Derived Using Pharmacometric Bridging

BACKGROUND Warfarin dosage regimens using CYP2C9 and VKORC1 polymorphisms have been extensively studied in adults and is included in US Food and Drug Administration-approved warfarin labeling. However, no dosage algorithm is available for pediatric patients. OBJECTIVE To derive a genetics-based pediatric dosge regimen for warfarin, including starting dose and titration scheme. METHODS A model-based approach was developed based on a previously validated warfarin dosage model in adults, with subsequent comparison to pediatric data from pediatric warfarin dose, genotyping, and international normalized ratio (INR) results. The adult model was based on a previously established model from the CROWN (CReating an Optimal Warfarin dosing Nomogram) trial. Pediatric warfarin data were obtained from a study conducted at the Childrens Hospital of Los Angeles with 26 subjects. Variant alleles of CYP2C9 (rs1799853 or *2, and rs1057910 or *3) and the VKORC1 single nucleotide polymorphism (SNP) rs9923231 (-1639 G>A) were assessed, where the rs numbers are reference SNP identification tags assigned by the National Center for Biotechnology Information. RESULTS A pediatric warfarin model was derived using the previously validated model and clinical pharmacology considerations. The model was validated, and clinical trial simulation and stochastic modeling were used to optimize pediatric dosage and titration. The final dosage regimen was optimized based on simulations targeting a high (≥60%) proportion of INRs within the therapeutic range by week 2 of warfarin therapy while minimizing INRs >3.5 or <2. CONCLUSIONS The proposed pediatric warfarin dosage scheme based on individual CYP2C9 (alleles *1,*2,*3) and VKORC1 rs9923231 (-1639 G>A) genotypes may offer improved dosage compared to current treatment strategies, especially in patients with variant CYP2C9 and VKORC1 alleles. This pilot study provides the foundation for a larger prospective evaluation of genetics-based warfarin dosage in pediatric patients.

Pediatric drug development programs for type 2 diabetes: A review

Considerable progress has been made in pediatric drug development. Despite these gains there remain certain therapeutic areas where a high percentage of drugs approved for use in adults do not gain approval for use in children. Lack of sufficient US Food and Drug Administration (FDA)–approved labeling correlates with diminished therapeutic efficacy and increased risk for adverse drug reactions. Despite the increasing prevalence and important clinical challenge with pediatric type 2 diabetes mellitus (T2DM), only 1 drug (metformin) of the first 4 T2DM drugs to complete testing in children gained FDA approval. This analysis reviews 4 pediatric drug development programs for orally administered antidiabetic agents that have undergone FDA review and discusses factors influencing failure to meet specified end points for approval. Recommendations to guide future study are also provided.

Blocking Zika virus vertical transmission

The outbreak of the Zika virus (ZIKV) has been associated with increased incidence of congenital malformations. Although recent efforts have focused on vaccine development, treatments for infected individuals are needed urgently. Sofosbuvir (SOF), an FDA-approved nucleotide analog inhibitor of the Hepatitis C (HCV) RNA-dependent RNA polymerase (RdRp) was recently shown to be protective against ZIKV both in vitro and in vivo. Here, we show that SOF protected human neural progenitor cells (NPC) and 3D neurospheres from ZIKV infection-mediated cell death and importantly restored the antiviral immune response in NPCs. In vivo, SOF treatment post-infection (p.i.) decreased viral burden in an immunodeficient mouse model. Finally, we show for the first time that acute SOF treatment of pregnant dams p.i. was well-tolerated and prevented vertical transmission of the virus to the fetus. Taken together, our data confirmed SOF-mediated sparing of human neural cell types from ZIKV-mediated cell death in vitro and reduced viral burden in vivo in animal models of chronic infection and vertical transmission, strengthening the growing body of evidence for SOF anti-ZIKV activity.

Pharmacokinetics of low-dose cidofovir in kidney transplant recipients with BK virus infection

BK virus (BKV) infection in kidney transplant recipients is associated with progressive graft dysfunction and graft loss. Cidofovir, an antiviral agent with known nephrotoxicity, has been used in low doses to treat BKV infections. However, the systemic exposure and disposition of the low‐dose cidofovir regimen are not known in kidney transplant recipients.

Determination of cidofovir in human plasma after low dose drug administration using high-performance liquid chromatography–tandem mass spectrometry

A sensitive and specific method for the determination of cidofovir (CDV) in human plasma using high-performance liquid chromatography with tandem mass spectrometry (LC-MS/MS) was developed and validated. Plasma samples were processed by a solid phase extraction (SPE) procedure using Varian SAX extraction cartridges prior to chromatography. The internal standard was (13)C5-Folic acid ((13)C5-FA). Chromatography was performed using a Luna C8(2) analytical column, 5 microm, 150 mm x 3.0 mm, using an isocratic elution with a mobile phase consisting of 43% methanol in water containing 12 mM ammonium acetate, at a flow rate of 0.3 mL/min. The retention times of CDV and (13)C5-FA were 2.1 min and 1.9 min, respectively, with a total run time of 5 min. The analytes were detected by a Micromass Quattro Micro triple quadrupole mass spectrometer in positive electron spray ionization (ESI) mode using multiple reaction monitoring (MRM). The extracted ions monitored following MRM transitions were m/z 280.0-->262.1 for CDV and m/z 447.0-->294.8 for (13)C5-FA (IS). The assay was linear over the range 20-1000 ng/mL. Accuracy (101.6-105.7%), intra-assay precision (4.1-5.4%), and inter-assay precision (5.6-6.8%) were within FDA limits. No significant variation in the concentration of CDV was observed with different sample storage conditions. This method is simple, adaptable to routine application, and allows easy and accurate measurement of CDV in human plasma.