Use of Propensity Scoring and Its Application to Real-World Data: Advantages, Disadvantages, and Methodological Objectives Explained to Researchers Without Using Mathematical Equations.

Real-time data collection of patient health status and medications is sped up with modern electronic devices and technologies. As real-world data provide enormous research opportunities, propensity score (PS) methods have been getting attention due to their theoretical grounds in a nonrandomized study setting. In contrast to randomized clinical trials, observational clinical data obtained from a real-world database may not have balanced distributions of patient characteristics between treatment and control groups at the beginning of the respective study. These imbalanced distributions may cause a bias in an estimated treatment effect, which needs to be eliminated. Propensity scoring is one class of statistical methods to address the imbalance issue of real-world data sets. This article provides basic concepts and assesses advantages, disadvantages, and methodological objectives of propensity scoring. Targeting clinical pharmacology researchers with limited statistical background, 5 representative methods are reviewed and visualized: matching, stratification, covariate modeling, inverse probability of treatment weighting, and doubly robust methods. Examples of applications of PS methods were selected from the literature of outcomes research and drug development, nephrology, and pediatrics. Opportunities of applications related to these examples are described. Furthermore, potential future applications of PS methods in clinical pharmacology are discussed. The 21st Century Cures Act signed in 2016 encourages scientists to find opportunities to apply propensity scoring to real-world data. This article underscores that scientists need to justify their choice of statistical methods, whether a PS method or an alternative method, based on their clinical study design, statistical assumptions, and research objectives.

Pharmacokinetics and Concentration-Response of Dupilumab in Patients With Seasonal Allergic Rhinitis.

Patients with moderate to severe allergic rhinitis may benefit from subcutaneous immunotherapy (SCIT), despite the risk of systemic allergic reaction. Dupilumab is a fully human monoclonal antibody that blocks the shared receptor component for interleukin-4 and interleukin-13, key drivers of the type 2 inflammation seen in allergic rhinitis, thereby inhibiting their signaling. In the LIBERTY Grass AID trial (NCT03558997), 16 weeks of treatment with 300 mg of dupilumab every 2 weeks plus timothy grass (TG) SCIT did not reduce TG allergen challenge nasal symptom scores compared with SCIT only but did improve tolerability of SCIT up-titration in patients with a history of grass pollen-induced seasonal allergic rhinitis. Here, we present the pharmacokinetics of functional serum dupilumab and concentration-response relationships in 52 patients enrolled in this trial. Functional dupilumab concentrations and concentrations of TG-specific IgE and IgG4 were assessed in blood samples collected from dupilumab-only and SCIT + dupilumab-treated groups. Mean functional dupilumab concentrations were similar in both groups and reached a steady state of ≈70-80 mg/L at week 5. One week after the end of treatment, TG-specific IgG4 concentrations were increased in the SCIT + dupilumab group, but not in the dupilumab-only group, over the range of dupilumab concentrations evaluated, whereas no changes were seen for TG-specific IgE concentrations. This study demonstrates that SCIT does not alter functional concentrations of serum dupilumab, and the impact of SCIT on TG-specific immunoglobulins is not affected by functional dupilumab concentrations over the range studied, indicating that maximum response was achieved in all patients.

Application of Individualized PBPK Modeling of Rate Data to Evaluate the Effect of Hemodialysis on Nonrenal Clearance Pathways.

The aim of this study was to apply individualized, physiologically based pharmacokinetic modeling of 14 CO2 production rates (iPBPK-R) measured by the erythromycin breath test to characterize the effect of hemodialysis on the function of nonrenal clearance pathways in patients with end-stage renal disease. Twelve patients previously received 14 C-erythromycin intravenously pre- and post-hemodialysis. Serial breath samples were collected after each dose over 2 hours. Eight PBPK parameters were co-estimated across periods, whereas activity of cytochrome P450 (CYP) 3A4 clearance was independently estimated for each period. Inhibition coefficients for organic anion transporting polypeptide (OATP), P-glycoprotein, and multidrug resistance-associated protein 2 activities were also estimated. Nonrenal clearance parameter estimates were explored regarding sex differences and correlations with uremic toxins and were used in hierarchical cluster analysis (HCA). Relationships between the function of nonrenal clearance pathways and uremic toxin concentrations were explored. Mean CYP 3A4 clearance increased by 2.2% post-hemodialysis. Uptake transporter activity was highly intervariable across hemodialysis. Females had 22% and 30% higher median CYP3A4 activity than males pre- and post-hemodialysis, respectively. Exploratory HCA indicated that using both CYP3A4 and OATP activity parameters at pre- and post-hemodialysis best identifies heterogeneous patients. This is the first study to use the iPBPK-R approach to simultaneously estimate multiple in vivo nonrenal elimination pathways in individual patients with kidney disease and to assess the effect of hemodialysis.

Dose Optimization in Kidney Disease: Opportunities for PBPK Modeling and Simulation.

Kidney disease affects pharmacokinetic (PK) profiles of not only renally cleared drugs but also nonrenally cleared drugs. The impact of kidney disease on drug disposition has not been fully elucidated, but describing the extent of such impact is essential for conducting dose optimization in kidney disease. Accurate evaluation of kidney function has been a clinical interest for dose optimization, and more scientists pay attention and conduct research for clarifying the role of drug transporters, metabolic enzymes, and their interplay in drug disposition as kidney disease progresses. Physiologically based pharmacokinetic (PBPK) modeling and simulation can provide valuable insights for dose optimization in kidney disease. It is a powerful tool to integrate discrete knowledge from preclinical and clinical research and mechanistically investigate system- and drug-dependent factors that may contribute to the changes in PK profiles. PBPK-based prediction of drug exposures may be used a priori to adjust dosing regimens and thereby minimize the likelihood of drug-related toxicity. With real-time clinical studies, parameter estimation may be performed with PBPK approaches that can facilitate identification of sources of interindividual variability. PBPK modeling may also facilitate biomarker research that aids dose optimization in kidney disease. U.S. Food and Drug Administration guidances related to conduction of PK studies in kidney impairment and PBPK documentation provide the foundation for facilitating model-based dose-finding research in kidney disease.

Simultaneous Assessment of Hepatic Transport and Metabolism Pathways with a Single Probe Using Individualized PBPK Modeling of 14CO2 Production Rate Data.

Erythromycin is a substrate of cytochrome P4503A4 (CYP3A4) and multiple drug transporters. Although clinical evidence suggests that uptake transport is likely to play a dominant role in erythromycin's disposition, the relative contributions of individual pathways are unclear. Phenotypic evaluation of multiple pathways generally requires a probe drug cocktail. This approach can result in ambiguous conclusions due to imprecision stemming from overlapping specificity of multiple drugs. We hypothesized that an individualized physiologically based pharmacokinetic modeling approach incorporating 14CO2 production rates (iPBPK-R) of the erythromycin breath test (ERMBT) would enable us to differentiate the contribution of metabolic and transporter pathways to erythromycin disposition. A seven-compartmental physiologically based pharmacokinetic (PBPK) model was built for 14C-erythromycin administered intravenously. Transporter clearance and CYP3A4 clearance were embedded in hepatic compartments. 14CO2 production rates were simulated taking the first derivative of by-product 14CO2 concentrations. Parameters related to nonrenal elimination pathways were estimated by model fitting the ERMBT data of 12 healthy subjects individually. Optimized iPBPK-R models fit the individual rate data well. Using one probe, nine PBPK parameters were simultaneously estimated per individual. Maximum velocity of uptake transport, CYP3A4 clearance, total passive diffusion, and others were found to collectively control 14CO2 production rates. The median CYP3A4 clearance was 12.2% of the input clearance. Male subjects had lower CYP3A4 activity than female subjects by 11.3%. We applied iPBPK-R to ERMBT data to distinguish and simultaneously estimate the activity of multiple nonrenal elimination pathways in healthy subjects. The iPBPK-R framework is a novel tool for delineating rate-limiting and non-rate-limiting elimination pathways using a single probe. SIGNIFICANCE STATEMENT: Our developed individualized physiologically based pharmacokinetic modeling approach incorporating rate data (iPBPK-R) enabled us to distinguish and simultaneously estimate the activity of multiple nonrenal elimination pathways of erythromycin in healthy subjects. A new interpretation of erythromycin breath test (ERMBT) data was also obtained via iPBPK-R. We found that rate data have rich information allowing estimation of per-person PBPK parameters. This study serves as proof of principle that the iPBPK-R framework is a novel tool for delineating rate-limiting and non-rate-limiting elimination pathways using a single probe. iPBPK-R can be applied to other rate-derived data beyond ERMBT. Potential areas of application include drug-drug interaction, pathophysiological effects on drug disposition, and the role of biomarkers on hemodialysis efficiency utilizing estimated adjustment factors with correlation analysis.

Trimethylamine N-Oxide and Cardiovascular Outcomes in Patients with ESKD Receiving Maintenance Hemodialysis.

BACKGROUND AND OBJECTIVES: Trimethylamine N-oxide (TMAO), a compound derived from byproducts of intestinal bacteria, has been shown to accelerate atherosclerosis in rodents. To date, there are conflicting data regarding the association of serum TMAO with cardiovascular outcomes in patients with ESKD, a population exhibiting both high serum TMAO and excessive atherosclerosis. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We measured baseline serum TMAO concentrations in a subset of participants (n=1243) from the Evaluation of Cinacalcet Hydrochloride Therapy to Lower Cardiovascular Events (EVOLVE) trial and conducted post hoc analyses evaluating the association between baseline serum TMAO and cardiovascular outcomes. RESULTS: We observed a wide distribution of serum TMAO in our cohort, with approximately 80% of participants exhibiting TMAO concentrations ≥56 µM and a maximum TMAO concentration of 1103.1 µM. We found no association between TMAO and our primary outcome, a composite of cardiovascular mortality, myocardial infarction, peripheral vascular event, stroke, and hospitalization for unstable angina. Moreover, in unadjusted and adjusted analyses, we observed no relation between TMAO and all-cause mortality, the independent components of our composite outcome, or the original EVOLVE primary outcome. Although we did observe higher TMAO concentrations in white participants, further subgroup analyses did not confirm the previously identified interaction between TMAO and race observed in a prior study in patients receiving dialysis. CONCLUSIONS: We found no evidence linking TMAO to adverse clinical outcomes in patients receiving maintenance hemodialysis with moderate to severe secondary hyperparathyroidism.

Metabolic Characterization of Inflammatory Breast Cancer With Baseline FDG-PET/CT: Relationship With Pathologic Response After Neoadjuvant Chemotherapy, Receptor Status, and Tumor Grade.

BACKGROUND: The aim of this study was to determine if, in inflammatory breast cancer (IBC), baseline metabolic activity (maximum standardized uptake value [SUVmax]) of primary tumor and involved regional lymph nodes (IRLN) are prognostic markers of response after neoadjuvant systemic therapy (NAS). PATIENTS AND METHODS: Baseline 2-deoxy-2-[18F]fluoro-D-glucose (FDG) positron emission tomography/computed tomography scans were retrospectively reviewed among 61 women with IBC who received NAS, had mastectomy, and had available pathology reports. Primary tumor and IRLN SUVmax were compared between patients with a pathologic complete response (pCR) versus those with residual disease after NAS. A multivariate Cox model was fit to evaluate the effects of SUVmax on overall survival, adjusting for pCR and stratified by receptor status and disease stage. RESULTS: SUVmax in primary IBC tumors tended to increase with tumor grade (trend test P = .06) and was lower for stage III, non-triple-negative (TN) versus stage III, TN and stage IV, non-TN disease (P = .04). Neither primary tumor nor IRLN SUVmax was significantly different comparing pCR versus residual disease after NAS. Adjusting for pathology response in the overall survival model stratified by stage and receptor status, baseline SUVmax in primary IBC tumor was associated with an estimated hazard ratio of 1.10 (95% confidence interval, 0.97-1.25; P = .15) for patients with stage III, TN and stage IV, non-TN disease. This hazard ratio corresponded to a 1.74-fold risk of death with 1 standard deviation (SD = 5.9) increase in baseline SUVmax in primary IBC tumor. CONCLUSION: 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography/computed tomography provides prognostic information for newly diagnosed IBC. Larger studies are needed to confirm these findings and assess how such early information could affect treatment choices for IBC in the neoadjuvant setting.

Minimally invasive esophagectomy: results of a prospective phase II multicenter trial-the eastern cooperative oncology group (E2202) study.

OBJECTIVE: The primary aim of this trial was to assess the feasibility of minimally invasive esophagectomy (MIE) in a multi-institutional setting. BACKGROUND: Esophagectomy is an important, potentially curative treatment for localized esophageal cancer, but is a complex operation. MIE may decrease the morbidity and mortality of resection, and single-institution studies have demonstrated successful outcomes with MIE. METHODS: We conducted a multicenter, phase II, prospective, cooperative group study (coordinated by the Eastern Cooperative Oncology Group) to evaluate the feasibility of MIE. Patients with biopsy-proven high-grade dysplasia or esophageal cancer were enrolled at 17 credentialed sites. Protocol surgery consisted of either 3-stage MIE or Ivor Lewis MIE. The primary end point was 30-day mortality. Secondary end points included adverse events, duration of hospital-stay, and 3-year outcomes. RESULTS: Protocol surgery was completed in 95 of the 104 patients eligible for the primary analysis (91.3%). The 30-day mortality in eligible patients who underwent MIE was 2.1%; perioperative mortality in all registered patients eligible for primary analysis was 2.9%. Median intensive care unit and hospital stay were 2 and 9 days, respectively. Grade 3 or higher adverse events included anastomotic leak (8.6%), acute respiratory distress syndrome (5.7%), pneumonitis (3.8%), and atrial fibrillation (2.9%). At a median follow-up of 35.8 months, the estimated 3-year overall survival was 58.4% (95% confidence interval: 47.7%-67.6%). Locoregional recurrence occurred in only 7 patients (6.7%). CONCLUSIONS: This prospective multicenter study demonstrated that MIE is feasible and safe with low perioperative morbidity and mortality and good oncological results. This approach can be adopted by other centers with appropriate expertise in open esophagectomy and minimally invasive surgery.

10% Tumor diameter shrinkage on the first follow-up computed tomography predicts clinical outcome in patients with advanced renal cell carcinoma treated with angiogenesis inhibitors: a follow-up validation study.

Vascular endothelial growth factor (VEGF)-targeted agents are standard therapies for metastatic renal cell carcinoma (mRCC), associated with variable tumor shrinkage. Response Evaluation Criteria in Solid Tumors (RECIST) is of limited utility in this setting, and other imaging changes are sought to reliably predict outcome early. We aim to validate 10% tumor shrinkage as the best early indicator of outcome. Methods. In this institutional review board-approved, Health Insurance Portability and Accountability Act-compliant study, 66 mRCC patients with 165 lesions on clinical trials of VEGF-targeted agents underwent thoracic and abdominal computed tomography at baseline and at first follow-up after therapy. Measurements were performed according to RECIST and tumor shrinkage of ≥10% decrease in sum of the longest diameter (-10%SLD). Correlation with time-to-treatment failure (TTF) and overall survival (OS) were compared and stratified by response to the radiologic criteria. Receiver-operating characteristics (ROC) analysis yielded the optimal threshold change in SLD, defining patients with prolonged survival. Results. More than -10%SLD significantly differentiated responders from nonresponders (median TTF 8.4 vs. 4.1 months, p = .001), whereas partial response by RECIST did not (median TTF 6.9 vs. 5.5 months in responders vs. nonresponders, p = .34). -10%SLD was also significantly predictive of OS (median OS 35.1 vs. 15.0 months in responders vs. nonresponders, p = .003). ROC curve analysis yielded -9.3% in SLD as the optimal threshold for response/no response. Conclusion. Ten percent tumor shrinkage is validated as a reliable early predictor of outcome in mRCC patients receiving VEGF-targeted therapies and may provide a practical measure to guide therapeutic decisions.

Socio-demographic and lifestyle factors for child's physical growth and adiposity rebound of Japanese children: a longitudinal study of the 21st century longitudinal survey in newborns.

BACKGROUND: It is unknown whether childhood physical development in Asian populations differs from western populations, since no longitudinal analysis has been performed in Asian countries yet. Utilizing the 21st Century Longitudinal Survey in Newborns, we studied the timing of adiposity rebound (AR) among Japanese children and determined whether AR occurs earlier in obese children compared to nonobese children. Furthermore, we identified important demographic, social, and lifestyle factors that affect their physical development. METHODS: We used data from the annual surveillance of Japanese children born in 2001, with 45,392 eligible subjects. We applied survival analysis to evaluate the AR and a trajectory method for the BMI transition across 5 ½ years. Time-dependent and time-independent factors affecting BMI changes were investigated using longitudinal analysis. Accounting for the known difference in prevalence between Japanese and Western children, we adopted a 95th percentile of BMI as criterion for obesity. RESULTS: Mean BMI at birth and at ages 1 ½, 2 ½, 3 ½, 4 ½, and 5 ½ years for all subjects were 12.6, 16.3, 16.1, 15.8, 15.5, and 15.4, respectively, showing a progressive reduction after 1 ½ years. However, among obese children at 5 ½ years, 39.6% had experienced AR as early as at age 4 ½ years. Controlling for sex, Cox's proportional hazards model showed that obese children had a 48.5% higher hazard to experience AR than nonobese children. The difference in BMI transition between obese and non-obese children was also captured by a trajectory method. In longitudinal analysis, BMI was lower for children who had a longer gestational period whereas children who received parental care from non-family members gained higher BMI values. CONCLUSIONS: With the 95th percentile cutoff for children obesity, obese Japanese children developed AR earlier than nonobese Japanese children, similar to those in Western countries reported in the literature. Primary caretakers and length of gestational period were the most important socio-demographic factors affecting physical development.

Intraobserver and interobserver variability in computed tomography size and attenuation measurements in patients with renal cell carcinoma receiving antiangiogenic therapy: implications for alternative response criteria.

BACKGROUND: Alternative response criteria have been proposed in patients with metastatic renal cell carcinoma (mRCC) who are receiving vascular endothelial growth factor (VEGF)-targeted therapy, including 10% tumor shrinkage as an indicator of response/outcome. However, to the authors' knowledge, intraobserver and interobserver measurement variability have not been defined in this setting. The objective of the current study was to determine intraobserver and interobserver agreement of computed tomography (CT) size and attenuation measurements to establish reproducible response indicators. METHODS: Seventy-one patients with mRCC with 179 target lesions were enrolled in phase 2 and phase 3 trials of VEGF-targeted therapies and retrospectively studied with Institutional Review Board approval. Two radiologists independently measured the long axis diameter and mean attenuation of target lesions at baseline and on follow-up CT. Concordance correlation coefficients and Bland-Altman plots were used to assess intraobserver and interobserver agreement. RESULTS: High concordance correlation coefficients (range, 0.8602-0.9984) were observed in all types of measurements. The 95% limits of agreement for the percentage change of the sum longest diameter was -7.30% to 7.86% for intraobserver variability, indicating that 10% tumor shrinkage represents a true change in tumor size when measured by a single observer. The 95% limits of interobserver variability were -16.3% to 15.4%. On multivariate analysis, the location of the lesion was found to significantly contribute to interobserver variability (P = .048). The 95% limits of intraobserver agreement for the percentage change in CT attenuation were -18.34% to 16.7%. CONCLUSIONS: In patients with mRCC who are treated with VEGF inhibitors, 10% tumor shrinkage is a reproducible radiologic response indicator when baseline and follow-up studies are measured by a single radiologist. Lesion location contributes significantly to measurement variability and should be considered when selecting target lesions.

Coordinate activation of Shh and PI3K signaling in PTEN-deficient glioblastoma: new therapeutic opportunities.

In glioblastoma, phosphatidylinositol 3-kinase (PI3K) signaling is frequently activated by loss of the tumor suppressor phosphatase and tensin homolog (PTEN). However, it is not known whether inhibiting PI3K represents a selective and effective approach for treatment. We interrogated large databases and found that sonic hedgehog (SHH) signaling is activated in PTEN-deficient glioblastoma. We demonstrate that the SHH and PI3K pathways synergize to promote tumor growth and viability in human PTEN-deficient glioblastomas. A combination of PI3K and SHH signaling inhibitors not only suppressed the activation of both pathways but also abrogated S6 kinase (S6K) signaling. Accordingly, targeting both pathways simultaneously resulted in mitotic catastrophe and tumor apoptosis and markedly reduced the growth of PTEN-deficient glioblastomas in vitro and in vivo. The drugs tested here appear to be safe in humans; therefore, this combination may provide a new targeted treatment for glioblastoma.

An adaptive two-stage dose-response design method for establishing proof of concept.

We propose an adaptive two-stage dose-response design where a prespecified adaptation rule is used to add and/or drop treatment arms between the stages. We extend the multiple comparison procedures-modeling (MCP-Mod) approach into a two-stage design. In each stage, we use the same set of candidate dose-response models and test for a dose-response relationship or proof of concept (PoC) via model-associated statistics. The stage-wise test results are then combined to establish "global" PoC using a conditional error function. Our simulation studies showed good and more robust power in our design method compared to conventional and fixed designs.

A murine lung cancer co-clinical trial identifies genetic modifiers of therapeutic response.

Targeted therapies have demonstrated efficacy against specific subsets of molecularly defined cancers. Although most patients with lung cancer are stratified according to a single oncogenic driver, cancers harbouring identical activating genetic mutations show large variations in their responses to the same targeted therapy. The biology underlying this heterogeneity is not well understood, and the impact of co-existing genetic mutations, especially the loss of tumour suppressors, has not been fully explored. Here we use genetically engineered mouse models to conduct a 'co-clinical' trial that mirrors an ongoing human clinical trial in patients with KRAS-mutant lung cancers. This trial aims to determine if the MEK inhibitor selumetinib (AZD6244) increases the efficacy of docetaxel, a standard of care chemotherapy. Our studies demonstrate that concomitant loss of either p53 (also known as Tp53) or Lkb1 (also known as Stk11), two clinically relevant tumour suppressors, markedly impaired the response of Kras-mutant cancers to docetaxel monotherapy. We observed that the addition of selumetinib provided substantial benefit for mice with lung cancer caused by Kras and Kras and p53 mutations, but mice with Kras and Lkb1 mutations had primary resistance to this combination therapy. Pharmacodynamic studies, including positron-emission tomography (PET) and computed tomography (CT), identified biological markers in mice and patients that provide a rationale for the differential efficacy of these therapies in the different genotypes. These co-clinical results identify predictive genetic biomarkers that should be validated by interrogating samples from patients enrolled on the concurrent clinical trial. These studies also highlight the rationale for synchronous co-clinical trials, not only to anticipate the results of ongoing human clinical trials, but also to generate clinically relevant hypotheses that can inform the analysis and design of human studies.