Opportunistic dried blood spot sampling validates and optimizes a pediatric population pharmacokinetic model of metronidazole

Pharmacokinetic models rarely undergo external validation in vulnerable populations such as critically ill infants, thereby limiting the accuracy, efficacy, and safety of model-informed dosing in real-world settings. Here, we describe an opportunistic approach using dried blood spots (DBS) to evaluate a population pharmacokinetic model of metronidazole in critically ill preterm infants of gestational age (GA) ≤31 weeks from the Metronidazole Pharmacokinetics in Premature Infants (PTN_METRO, NCT01222585) study. First, we used linear correlation to compare 42 paired DBS and plasma metronidazole concentrations from 21 preterm infants [mean (SD): post natal age 28.0 (21.7) days, GA 26.3 (2.4) weeks]. Using the resulting predictive equation, we estimated plasma metronidazole concentrations (ePlasma) from 399 DBS collected from 122 preterm and term infants [mean (SD): post natal age 16.7 (15.8) days, GA 31.4 (5.1) weeks] from the Antibiotic Safety in Infants with Complicated Intra-Abdominal Infections (SCAMP, NCT01994993) trial. When evaluating the PTN_METRO model using ePlasma from the SCAMP trial, we found that the model generally predicted ePlasma well in preterm infants with GA ≤31 weeks. When including ePlasma from term and preterm infants with GA >31 weeks, the model was optimized using a sigmoidal Emax maturation function of postmenstrual age on clearance and estimated the exponent of weight on volume of distribution. The optimized model supports existing dosing guidelines and adds new data to support a 6-hour dosing interval for infants with postmenstrual age >40 weeks. Using an opportunistic DBS to externally validate and optimize a metronidazole population pharmacokinetic model was feasible and useful in this vulnerable population.

Abatacept Pharmacokinetics and Exposure Response in Patients Hospitalized With COVID-19: A Secondary Analysis of the ACTIV-1 IM Randomized Clinical Trial

Importance

The pharmacokinetics of abatacept and the association between abatacept exposure and outcomes in patients with severe COVID-19 are unknown.

Objective

To characterize abatacept pharmacokinetics, relate drug exposure with clinical outcomes, and evaluate the need for dosage adjustments.

Design, Setting, and Participants

This study is a secondary analysis of data from the ACTIV-1 (Accelerating COVID-19 Therapeutic Interventions and Vaccines) Immune Modulator (IM) randomized clinical trial conducted between October 16, 2020, and December 31, 2021. The trial included hospitalized adults who received abatacept in addition to standard of care for treatment of COVID-19 pneumonia. Data analysis was performed between September 2022 and February 2024.

Exposure

Single intravenous infusion of abatacept (10 mg/kg with a maximum dose of 1000 mg).

Main Outcomes and Measures

Mortality at day 28 was the primary outcome of interest, and time to recovery at day 28 was the secondary outcome. Drug exposure was assessed using the projected area under the serum concentration time curve over 28 days (AUC0-28). Logistic regression modeling was used to analyze the association between drug exposure and 28-day mortality, adjusted for age, sex, and disease severity. The association between time to recovery and abatacept exposure was examined using Fine-Gray modeling with death as a competing risk, and was adjusted for age, sex, and disease severity.

Results

Of the 509 patients who received abatacept, 395 patients with 848 serum samples were included in the population pharmacokinetic analysis. Their median age was 55 (range, 19-89) years and most (250 [63.3%]) were men. Abatacept clearance increased with body weight and more severe disease activity at baseline. Drug exposure was higher in patients who survived vs those who died, with a median AUC0-28 of 21 428 (range, 8462-43 378) mg × h/L vs 18 262 (range, 9628-27 507) mg × h/L (P < .001). Controlling for age, sex, and disease severity, an increase of 5000 units in AUC0-28 was associated with lower odds of mortality at day 28 (OR, 0.52 [95% CI, 0.35-0.79]; P = .002). For an AUC0-28 of 19 400 mg × h/L or less, there was a higher probability of recovery at day 28 (hazard ratio, 2.63 [95% CI, 1.70-4.08] for every 5000-unit increase; P < .001). Controlling for age, sex, and disease severity, every 5000-unit increase in AUC0-28 was also associated with lower odds of a composite safety event at 28 days (OR, 0.46 [95% CI, 0.33-0.63]; P < .001). Using the dosing regimen studied in the ACTIV-1 IM trial, 121 of the 395 patients (30.6%) would not achieve an abatacept exposure of at least 19 400 mg × h/L, particularly at the extremes of body weight. Using a modified, higher-dose regimen, only 12 patients (3.0%) would not achieve the hypothesized target abatacept exposure.

Conclusions and Relevance

In this study, patients who were hospitalized with severe COVID-19 and achieved higher projected abatacept exposure had reduced mortality and a higher probability of recovery with fewer safety events. However, abatacept clearance was high in this population, and the current abatacept dosing (10 mg/kg intravenously with a maximum of 1000 mg) may not achieve optimal exposure in all patients.

Trial Registration

ClinicalTrials.gov Identifier: NCT04593940.

Indomethacin Pharmacokinetics and Pharmacodynamics in Pregnancies With Preterm Labor: The Need for Dose-Ranging Trials

The use of indomethacin to delay delivery in preterm labor (PTL) is widely accepted; however, the optimal dosage of indomethacin in pregnancy is unknown. Here, we perform population pharmacokinetic (PK) and pharmacodynamic (PD) analyses, characterize the plasma disposition of indomethacin in pregnant women with PTL, and relate indomethacin exposure to delayed delivery and maternal/neonatal safety. We analyzed plasma and urine samples collected from a multicenter, prospective, opportunistic PK/PD study of indomethacin in pregnant women 12-32 weeks gestation admitted with PTL. Ninety-four participants with 639 plasma concentrations for indomethacin were included in the analysis. The final population PK (popPK) model for indomethacin was a 2-compartment structural model with first-order absorption and elimination and a covariate effect of body mass index on apparent oral clearance. We observed a 21%-60% increase in apparent oral clearance observed during pregnancy. There was no clear association between indomethacin exposure and maternal or neonatal safety outcomes, or with the magnitude of delayed delivery; however, 96.7% of women treated with indomethacin had a delivery that was delayed at least 48 hours. Given the changes to indomethacin apparent oral clearance during pregnancy, and the lack of relationship between indomethacin exposure and safety, dose-finding studies of indomethacin in pregnant women with PTL may help clarify the most safe and efficacious dosage and duration of indomethacin.

Using Pharmacokinetic Modeling and Electronic Health Record Data to Predict Clinical and Safety Outcomes after Methylprednisolone Exposure during Cardiopulmonary Bypass in Neonates

Background

Infants undergoing cardiac surgery with cardiopulmonary bypass (CPB) frequently receive intraoperative methylprednisolone (MP) to suppress CPB-related inflammation; however, the optimal dosing strategy and efficacy of MP remain unclear.

Methods

We retrospectively analyzed all infants under 90 days-old who received intra-operative MP for cardiac surgery with CPB from 2014-2017 at our institution. We combined real-world dosing data from the electronic health record (EHR) and two previously developed population pharmacokinetic/pharmacodynamic models to simulate peak concentration (Cmax) and area under the concentration-time curve for 24 h (AUC24) for MP and the inflammatory cytokines interleukin-6 (IL-6) and interleukin-10 (IL-10). We evaluated the relationships between post-operative, safety, and other clinical outcomes obtained from the EHR with each predicted exposure using non-parametric tests.

Results

A total of 142 infants with median post-natal age 8 (interquartile range [IQR]: 5, 37) days received a total dose of 30 (19, 49) mg/kg of MP. Twelve (8%) died, 37 (26%) met the composite post-operative outcome, 114 (80%) met the composite safety outcome, and 23 (16%) had a major complication. Predicted median Cmax and AUC24 IL-6 exposure was significantly higher for infants meeting the composite post-operative outcome and those with major complications. Predicted median Cmax and AUC24 MP exposure was significantly higher for infants requiring insulin. No exposure was associated with death or other safety outcomes.

Conclusions

Pro-inflammatory IL-6, but not MP exposure, was associated with post-operative organ dysfunction, suggesting current MP dosing may not adequately suppress IL-6 or increase IL-10 to impact clinical outcomes. Prospective study will be required to define the optimal exposure-efficacy and exposure-safety profiles in these infants.

Occurrence of adverse events and change in disease activity after initiation of etanercept in paediatric patients with juvenile psoriatic arthritis in the CARRA Registry

OBJECTIVE

Etanercept is commonly used to treat juvenile idiopathic arthritis, including juvenile psoriatic arthritis (JPsA); however, information on etanercept's safety and effectiveness in clinical practice is limited. We used data from the Childhood Arthritis and Rheumatology Research Alliance (CARRA) Registry to evaluate etanercept's safety and effectiveness in JPsA in clinical practice.

METHODS

We analysed safety and effectiveness data for paediatric patients enrolled in the CARRA Registry who had a JPsA diagnosis and had used etanercept. Safety was assessed by calculating rates of prespecified adverse events of special interest (AESIs) and serious adverse events (SAEs). Effectiveness was assessed by a variety of disease activity measures.

RESULTS

Overall, 226 patients had JPsA and received etanercept; 191 met criteria for safety analysis and 43 met criteria for effectiveness analysis. AESI and SAE incidence rates were low. There were five events: three uveitis, one new-onset neuropathy and one malignancy. Incidence rates were 0.55 (95% CI: 0.18, 1.69), 0.18 (95% CI: 0.03, 1.29) and 0.13 (95% CI: 0.02, 0.09) per 100 patient-years for uveitis, neuropathy and malignancy, respectively. Etanercept showed effectiveness for JPsA treatment; 7 of 15 (46.7%) had an American College of Rheumatology-Pediatric Response 90, 9 of 25 (36.0%) had a clinical Juvenile Arthritis Disease Activity Score 10-joint ≤1.1 and 14 of 27 (51.9%) had clinically inactive disease at the 6-month follow-up.

CONCLUSION

Data in the CARRA Registry showed that etanercept treatment was safe in treating children with JPsA, with low AESIs and SAEs. Etanercept was also effective, even when assessed in a small sample size.

Dosing Variation at Initiation of Adalimumab and Etanercept and Clinical Outcomes in Juvenile Idiopathic Arthritis: A Childhood Arthritis and Rheumatology Research Alliance Registry Study

OBJECTIVE

To determine the dose-response relationship of tumor necrosis factor (TNF) inhibition in the treatment of juvenile idiopathic arthritis (JIA).

METHODS

Participants of the Childhood Arthritis and Rheumatology Research Alliance Registry were eligible for inclusion in the analyses if they started TNF inhibition treatment for JIA. The primary treatment response was determined 3 to 7 months after the start of treatment, based on the JIA American College of Rheumatology Pediatric criteria for improvement, clinical Juvenile Arthritis Disease Activity Score, and persistence of treatment after 6 months. Subsequently, pooled logistic regression models were performed to include long-term follow-up data. The models were adjusted for risk factors associated with poor treatment response. Dosing was expressed by body weight, body surface area, ideal body weight, fat free mass, and lean body mass.

RESULTS

Participants treated with adalimumab (n = 328) and etanercept (n = 437) were included in the analyses (median dose 0.82 mg/kg body weight [interquartile range (IQR) 0.66-1.04] and 0.83 mg/kg body weight [IQR 0.75-0.95], respectively). The majority of analyses did not show a relationship between dose and outcome. Where associations were found, results were conflicting. Alternative dosing characteristics based on ideal body weight, fat free mass, and lean body mass did not result in stronger or more consistent associations.

CONCLUSION

This study was not able to confirm our hypothesis that increased dosing of TNF inhibitors results in improved treatment outcomes. Although adjustment was performed for risk factors of impaired treatment response, residual confounding by indication likely explains the negative associations found in this study.

Population Pharmacokinetics of Piperacillin/Tazobactam Across the Adult Lifespan

BACKGROUND AND OBJECTIVE

Piperacillin/tazobactam is one of the most frequently used antimicrobials in older adults. Using an opportunistic study design, we evaluated the pharmacokinetics of piperacillin/tazobactam as a probe drug to evaluate changes in antibacterial drug exposure and dosing requirements, including in older adults.

METHODS

A total of 121 adult patients were included. The population pharmacokinetic models that best characterized the observed plasma concentrations of piperacillin and tazobactam were one-compartment structural models with zero-order input and linear elimination.

RESULTS

Among all potential covariates, estimated creatinine clearance had the most substantial impact on the elimination clearance for both piperacillin and tazobactam. After accounting for renal function and body size, there was no remaining impact of frailty on the pharmacokinetics of piperacillin and tazobactam. Monte Carlo simulations indicated that renal function had a greater impact on the therapeutic target attainment than age, although these covariates were highly correlated. Frailty, using the Canadian Study of Health and Aging Clinical Frailty Scale, was assessed in 60 patients who were ≥ 65 years of age.

CONCLUSIONS

The simulations suggested that adults ≤ 50 years of age infected with organisms with higher minimum inhibitory concentrations may benefit from continuous piperacillin/tazobactam infusions (12 g/day of piperacillin component) or extended infusions of 4 g every 8 hours. However, for a target of 50% fT + minimum inhibitory concentration, dosing based on renal function is generally preferable to dosing by age, and simulations suggested that patients with creatinine clearance ≥ 120 mL/min may benefit from infusions of 4 g every 8 hours for organisms with higher minimum inhibitory concentrations.

Extrapolation of Adult Efficacy Data to Pediatric Systemic Lupus Erythematosus: Evaluating Similarities in Exposure-Response

To streamline drug development, the United States Food and Drug Administration (FDA) can consider the extrapolation of adult efficacy data to children when the disease and drug effects are sufficiently similar. This study explored whether the relationship between drug exposure and response for selected drugs in systemic lupus erythematosus (SLE) was sufficiently similar to support a consideration of the extrapolation of adult efficacy data to children of ≥5 years of age. An exposure-response analysis of drugs used to treat SLE was conducted using published exposure versus response and efficacy versus time data. Statistical analyses included noncompartmental analysis of a drug's area under the effect curve and direct Imax pharmacodynamic (PD) modeling. Six drugs were included: azathioprine, belimumab, cyclophosphamide, hydroxychloroquine, mycophenolate/mycophenolic acid, and rituximab. For belimumab, the net change in responders at week 52 (the primary end point) was nearly identical between 1 adult trial and the pediatric trial. For mycophenolate, PD modeling suggested no significant differences in exposure and SLE disease activity between adults and children. For azathioprine, cyclophosphamide, hydroxychloroquine, and rituximab the data were not sufficient to quantitatively characterize the exposure-response relationship, but the clinical or pharmacologic response between children and adults was similar overall. Adult SLE data should be leveraged to guide pediatric drug development programs and identify areas with residual uncertainty regarding the effectiveness or safety of a drug in children. The degree to which efficacy extrapolation can reduce clinical trial requirements in pediatric SLE should be individualized for each new drug product, depending in part on the mechanism of action of the drug and the similarity of disease manifestations in children and adults.

Pharmacokinetics of hydroxychloroquine in paediatric lupus: data from a novel, direct-to-family clinical trial

Objective

Determine the pharmacokinetics (PK) and exposure–response of hydroxychloroquine (HCQ) and desethylhydroxychloroquine (DHCQ) in paediatric SLE (pSLE).

Methods

We conducted an exploratory phase 2, direct-to-family trial. Children enrolled in the Childhood Arthritis and Rheumatology Research Alliance (CARRA) Registry with a diagnosis of pSLE were eligible if they were receiving HCQ as standard of care for ≥3 months. Biological samples were collected at up to four visits over a 6-month period. At each visit, plasma was obtained to measure the concentrations of HCQ and DHCQ, as well as cytokines. HCQ and DHCQ plasma PK data were analysed using a population PK modelling approach.

Results

Twenty-five subjects provided a total of 88 plasma concentrations for PK analysis. There was a poor linear fit between HCQ concentrations and total body weight (R²=0.03). There was a decline in both interferon (IFN)-alpha and IFN-gamma with higher concentrations of HCQ and DHCQ. Volume of distribution for HCQ in plasma was higher in children compared with published values in adults (73 000 L vs 44 000 L), but clearance values in children were similar to adults.

Conclusions

We report the first population PK model for HCQ and DHCQ in children using data from a novel direct-to-family clinical trial. We observed high interindividual variability in HCQ PK and found that weight-based dosing for HCQ is poorly correlated with drug concentrations, suggesting the need to use therapeutic drug monitoring to individualise dosing. Furthermore, our results suggest that the current weight-based dosing paradigm for HCQ may result in suboptimal drug exposures, particularly for children with obesity. Accordingly, additional studies of HCQ are needed in pSLE to determine the optimal drug concentration and dosing to reduce disease activity and improve outcomes.

Trial registration number

NCT04358302.

External Evaluation of Risperidone Population Pharmacokinetic Models Using Opportunistic Pediatric Data

Risperidone is approved to treat schizophrenia in adolescents and autistic disorder and bipolar mania in children and adolescents. It is also used off-label in younger children for various psychiatric disorders. Several population pharmacokinetic models of risperidone and 9-OH-risperidone have been published. The objectives of this study were to assess whether opportunistically collected pediatric data can be used to evaluate risperidone population pharmacokinetic models externally and to identify a robust model for precision dosing in children. A total of 103 concentrations of risperidone and 112 concentrations of 9-OH-risperidone, collected from 62 pediatric patients (0.16–16.8 years of age), were used in the present study. The predictive performance of five published population pharmacokinetic models (four joint parent-metabolite models and one parent only) was assessed for accuracy and precision of the predictions using statistical criteria, goodness of fit plots, prediction-corrected visual predictive checks (pcVPCs), and normalized prediction distribution errors (NPDEs). The tested models produced similarly precise predictions (Root Mean Square Error [RMSE]) ranging from 0.021 to 0.027 nmol/ml for risperidone and 0.053–0.065 nmol/ml for 9-OH-risperidone). However, one of the models (a one-compartment mixture model with clearance estimated for three subpopulations) developed with a rich dataset presented fewer biases (Mean Percent Error [MPE, %] of 1.0% vs. 101.4, 146.9, 260.4, and 292.4%) for risperidone. In contrast, a model developed with fewer data and a more similar population to the one used for the external evaluation presented fewer biases for 9-OH-risperidone (MPE: 17% vs. 69.9, 47.8, and 82.9%). None of the models evaluated seemed to be generalizable to the population used in this analysis. All the models had a modest predictive performance, potentially suggesting that sources of inter-individual variability were not entirely captured and that opportunistic data from a highly heterogeneous population are likely not the most appropriate data to evaluate risperidone models externally.

Adverse Reactions in a Phase 1 Trial of the Anti-Malarial DM1157: An Example of Pharmacokinetic Modeling and Simulation Guiding Clinical Trial Decisions

Introduction

There is an urgent need to develop new drugs to treat malaria due to increasing resistance to first-line therapeutics targeting the causative organism, Plasmodium falciparum (P. falciparum). One drug candidate is DM1157, a small molecule that inhibits the formation of hemozoin, which protects P. falciparum from heme toxicity. We describe a first-in-human, phase 1 trial of DM1157 in healthy adult volunteers that was halted early because of significant toxicity.

Methods

Adverse events were summarized using descriptive statistics. We used pharmacokinetic modeling to quantitatively assess whether the DM1157 exposure needed for P. falciparum inhibition was achievable at safe doses.

Results

We found that there was no dose where both the safety and efficacy target were simultaneously achieved; conversely, the model predicted that 27 mg was the highest dosage at which patients would consistently maintain safe exposure with multiple dosing. By pre-defining dose escalation stopping rules and conducting an interim pharmacokinetic/pharmacodynamic analysis, we determined that the study would be unable to safely achieve a dosage needed to observe an anti-malarial effect, thereby providing strong rationale to halt the study.

Conclusion

This study provides an important example of the risks and challenges of conducting early phase research as well as the role of modeling and simulation to optimize participant safety (ClinicalTrials.gov, NCT03490162).

Supplementary Information

The online version contains supplementary material available at 10.1007/s40121-022-00605-z.

Hydroxychloroquine PK and exposure-response in pregnancies with lupus: the importance of adherence for neonatal outcomes

OBJECTIVE

Evaluate the impact of pregnancy physiology and medication non-adherence on serum hydroxychloroquine (HCQ) pharmacokinetics (PK) and exposure-response in SLE.

METHODS

We conducted a PK analysis using data from two observational pregnancy registries. We enrolled pregnant women with SLE taking HCQ at least 3 months prior to, and throughout pregnancy, and excluded those with multiple gestations. Using the PK model, we conducted dosing simulations and imputed 0%/20%/40%/60% non-adherence to evaluate the impact of adherence versus physiological changes on HCQ concentrations. We compared the effect of pregnancy-average non-adherent concentrations (≤100 ng/mL vs >100 ng/mL) on preterm birth using adjusted logistic regression.

RESULTS

We enrolled 56 women who had 61 pregnancies. By the third trimester, mean apparent HCQ clearance increased by 59.6%. At a dosage of 400 mg/day, fully adherent patients are expected to have HCQ concentrations ≤100 ng/mL only 0.3% of the time, compared with 24.2% when 60% of doses are missed. Persistently low HCQ concentrations throughout pregnancy were associated with a significantly higher odds of preterm birth, controlling for lupus nephritis and race (OR 11.2; 95% CI 2.3 to 54.2; p=0.003).

CONCLUSIONS

We observed significant changes in HCQ PK during pregnancy, resulting in a shortening in the drug's half-life by 10 days; however, medication non-adherence had a more pronounced effect on HCQ exposure compared with physiological changes alone. Moreover, pregnant women with non-adherent HCQ concentrations had significantly higher rates of preterm birth. Accordingly, optimising adherence in pregnancy may be more clinically meaningful than adjusting HCQ dosage to account for physiological changes. PK modelling indicates that serum HCQ concentrations ≤100 ng/mL are suggestive of non-adherence regardless of trimester and may help identify pregnancies at risk for poor outcomes.

Precision Medicine: Towards Individualized Dosing in Pediatric Rheumatology

Despite an increase in the number of available therapeutics, many children with rheumatic disease continue to experience active inflammatory disease and treatment failure. One reason for treatment failure is the lack of dosing paradigms to account for the wide between-patient variability in drug pharmacokinetics because of developmental changes or genetic polymorphisms that effect drug absorption, distribution, metabolism, and elimination. This review highlights several strategies to optimize dosing for biologic and nonbiologic disease-modifying antirheumatic drugs, including therapeutic drug monitoring, pharmacogenomics, and the use of pharmacokinetic/pharmacodynamic modeling.

Low Etanercept Concentrations in Children With Obesity and Juvenile Idiopathic Arthritis

OBJECTIVE

To evaluate the impact of obesity on etanercept (ETN) drug exposure in children with juvenile idiopathic arthritis (JIA).

METHODS

We conducted a pilot, cross-sectional, observational study in a real-world cohort of children with JIA receiving ETN as standard of care from a single center. We analyzed the relationship between body size and ETN plasma concentrations, adjusting for dosage. Body size was analyzed as a continuous measure using weight and body mass index (BMI) percentiles and categorically using BMI percentile classifications according to the CDC guidelines.

RESULTS

We enrolled a total of 29 children. Each child provided one plasma sample for ETN concentration measurement, and all participants were receiving subcutaneous ETN dosed weekly. We observed that the ETN concentration normalized for dose decreased significantly as a function of weight (p = 0.004) and BMI percentile (p = 0.04). Similarly, we observed a progressive decline in mean and median dose-normalized concentrations across higher body size categories. Because of reaching maximum ETN dosage (50 mg), 7 of 8 children (87.5%) with obesity received a weight-based dosage < 0.8 mg/kg/dose.

CONCLUSIONS

We found that higher body weight and BMI percentile are significantly and negatively associated with ETN drug serum concentration, accounting for differences in dosing. Our data suggest that children who are obese may be routinely under-dosed using current dosing strategies. Inadequate dosing may increase the risk for therapeutic failure and long-term morbidity in a developing child. As a result, characterizing adequate drug exposure in children of all sizes is an important step toward precision dosing.

Delivering clinical trials at home: protocol, design and implementation of a direct-to-family paediatric lupus trial

INTRODUCTION

Direct-to-family clinical trials efficiently provide data while reducing the participation burden for children and their families. Although these trials can offer significant advantages over traditional clinical trials, the process of designing and implementing direct-to-family studies is poorly defined, especially in children with rheumatic disease. This paper provides lessons learnt from the design and implementation of a self-controlled, direct-to-family pilot trial aimed to evaluate the effects of a medication management device on adherence to hydroxychloroquine in paediatric SLE.

METHODS

Several design features accommodate a direct-to-family approach. Participants meeting eligibility criteria from across the USA were identified a priori through a disease registry, and all outcome data are collected remotely. The primary outcome (medication adherence) is evaluated using electronic medication event-monitoring, plasma drug levels, patient questionnaires and pill counts. Secondary and exploratory endpoints include (1) lupus disease activity measured by a remote SLE Disease Activity Index examination and the Systemic Lupus Activity Questionnaire; and (2) hydroxychloroquine pharmacokinetics and pharmacodynamics. Recruitment of the initial target of 20 participants was achieved within 10 days. Due to initial recruitment success, enrolment was increased to 26 participants. Additional participants who were interested were placed on a waiting list in case of dropouts during the study.

DISCUSSION AND DISSEMINATION

Direct-to-family trials offer several advantages but present unique challenges. Lessons learnt from the protocol development, design, and implementation of this trial will inform future direct-to-family trials for children and adults with rheumatic diseases. Additionally, the data collected remotely in this trial will provide critical information regarding the accuracy of teleresearch in lupus, the impact of adherence to hydroxychloroquine on disease activity and a pharmacokinetic analysis to inform paediatric-specific dosing of hydroxychloroquine.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Registry (NCT04358302).

The importance of pregnancy planning in lupus pregnancies

OBJECTIVE

In seeking new approaches to improve lupus pregnancy outcomes, we study the association between pregnancy planning, behaviors recommended by American College of Rheumatology's Reproductive Health Guideline 2020, and pregnancy and infant outcomes.

METHODS

Lupus pregnancies in a prospective registry (1/1/2018 to 4/1/2020) were classified as planned or not-planned using the patient-reported London Measure of Unplanned Pregnancy. These groups were compared for demographics, pre-pregnancy disease activity, pregnancy planning behaviors, and delivery outcomes.

RESULTS

Among 43 women with 43 singleton pregnancies the average age was 29.4 years and 42% were Black. Overall, 60% were planned pregnancies and 40% were not-planned (16 ambivalent, 1 unplanned). Women with not-planned pregnancies had lower age, income, and education, and more required Medicaid. Women with not-planned pregnancies were more likely to conceive when lupus activity was higher (p = 0.001), less likely to receive pre-pregnancy counseling with a rheumatologist (p = 0.02), and less likely to continue pregnancy-compatible medications (p = 0.03). Severe PROMISSE adverse pregnancy outcomes (APOs) and severe neonatal outcomes were higher among women with not-planned than planned pregnancies (43% vs 0% p = 0.003; 70% vs 30% p = 0.06).

CONCLUSION

This study identifies pregnancy intention as a potentially modifiable risk factor for poor outcomes in women with lupus. It highlights a unique population of women with lupus at high risk for pregnancy and infant complications: those ambivalent about pregnancy. These women may not be effectively engaging in health behaviors that prevent pregnancy nor those that will prepare for a safe pregnancy. With effective pregnancy planning and contraception guidance, we may decrease their risk for maternal-fetal morbidity and mortality.

Hydroxychloroquine and COVID-19: a Rheumatologist's Take on the Lessons Learned

PURPOSE OF REVIEW

Told from the viewpoint of rheumatologists, this review tells the story of hydroxychloroquine and its swift ascent to become a household name as a therapeutic strategy against the novel SARS-CoV-2 virus. This review describes the history, mechanisms, pharmacokinetics, therapeutic applications, and safety profile of hydroxychloroquine as an immunomodulatory and antiviral agent. It also summarizes the major studies that launched and assessed the use of hydroxychloroquine against COVID-19 infection.

RECENT FINDINGS

More recent literature calls into question the long-held dogma that endolysosomal alkalinization is the primary mode of action of hydroxychloroquine. Ongoing uncertainty about the multiple potential mechanisms contributing to the therapeutic effect of hydroxychloroquine in rheumatic and viral disease led to a natural avenue for exploration in the treatment of COVID-19. Taken as a whole, the literature does not support utilizing hydroxychloroquine to treat or prevent infection from the SARS-CoV-2 virus. This is, at least in part, due to the wide variability in hydroxychloroquine pharmacokinetics between patients and difficulty achieving adequate target tissue concentrations of hydroxychloroquine without encountering unacceptable toxicities. Hydroxychloroquine continues to be a routinely prescribed, well-tolerated, effective, and low-cost treatment for rheumatic disease. Its therapeutic versatility has led to frequent repurposing for other conditions, most recently as an investigative treatment against the SARS-CoV-2 virus. Despite overall negative findings, the intense study of hydroxychloroquine against COVID-19 infection has enhanced our overall understanding of how hydroxychloroquine operates in autoimmune disease and beyond.

Physiologically Based Pharmacokinetic Modeling for Trimethoprim and Sulfamethoxazole in Children

OBJECTIVE

The aims of this study were to (1) determine whether opportunistically collected data can be used to develop physiologically based pharmacokinetic (PBPK) models in pediatric patients; and (2) characterize age-related maturational changes in drug disposition for the renally eliminated and hepatically metabolized antibiotic trimethoprim (TMP)-sulfamethoxazole (SMX).

METHODS

We developed separate population PBPK models for TMP and SMX in children after oral administration of the combined TMP-SMX product and used sparse and opportunistically collected plasma concentration samples to validate our pediatric model. We evaluated predictability of the pediatric PBPK model based on the number of observed pediatric data out of the 90% prediction interval. We performed dosing simulations to target organ and tissue (skin) concentrations greater than the methicillin-resistant Staphylococcus aureus (MRSA) minimum inhibitory concentration (TMP 2 mg/L; SMX 9.5 mg/L) for at least 50% of the dosing interval.

RESULTS

We found 67-87% and 71-91% of the observed data for TMP and SMX, respectively, were captured within the 90% prediction interval across five age groups, suggesting adequate fit of our model. Our model-rederived optimal dosing of TMP at the target tissue was in the range of recommended dosing for TMP-SMX in children in all age groups by current guidelines for the treatment of MRSA.

CONCLUSION

We successfully developed a pediatric PBPK model of the combination antibiotic TMP-SMX using sparse and opportunistic pediatric pharmacokinetic samples. This novel and efficient approach has the potential to expand the use of PBPK modeling in pediatric drug development.

Simulated Assessment of Pharmacokinetically Guided Dosing for Investigational Treatments of Pediatric Patients With Coronavirus Disease 2019

IMPORTANCE

Children of all ages appear susceptible to severe acute respiratory syndrome coronavirus 2 infection. To support pediatric clinical studies for investigational treatments of coronavirus disease 2019 (COVID-19), pediatric-specific dosing is required.

OBJECTIVE

To define pediatric-specific dosing regimens for hydroxychloroquine and remdesivir for COVID-19 treatment.

DESIGN, SETTING, AND PARTICIPANTS

Pharmacokinetic modeling and simulation were used to extrapolate investigated adult dosages toward children (March 2020-April 2020). Physiologically based pharmacokinetic modeling was used to inform pediatric dosing for hydroxychloroquine. For remdesivir, pediatric dosages were derived using allometric-scaling with age-dependent exponents. Dosing simulations were conducted using simulated pediatric and adult participants based on the demographics of a white US population.

INTERVENTIONS

Simulated drug exposures following a 5-day course of hydroxychloroquine (400 mg every 12 hours × 2 doses followed by 200 mg every 12 hours × 8 doses) and a single 200-mg intravenous dose of remdesivir were computed for simulated adult participants. A simulation-based dose-ranging study was conducted in simulated children exploring different absolute and weight-normalized dosing strategies.

MAIN OUTCOMES AND MEASURES

The primary outcome for hydroxychloroquine was average unbound plasma concentrations for 5 treatment days. Additionally, unbound interstitial lung concentrations were simulated. For remdesivir, the primary outcome was plasma exposure (area under the curve, 0 to infinity) following single-dose administration.

RESULTS

For hydroxychloroquine, the physiologically based pharmacokinetic model analysis included 500 and 600 simulated white adult and pediatric participants, respectively, and supported weight-normalized dosing for children weighing less than 50 kg. Geometric mean-simulated average unbound plasma concentration values among children within different developmental age groups (32-35 ng/mL) were congruent to adults (32 ng/mL). Simulated unbound hydroxychloroquine concentrations in lung interstitial fluid mirrored those in unbound plasma and were notably lower than in vitro concentrations needed to mediate antiviral activity. For remdesivir, the analysis included 1000 and 6000 simulated adult and pediatric participants, respectively. The proposed pediatric dosing strategy supported weight-normalized dosing for participants weighing less than 60 kg. Geometric mean-simulated plasma area under the time curve 0 to infinity values among children within different developmental age-groups (4315-5027 ng × h/mL) were similar to adults (4398 ng × h/mL).

CONCLUSIONS AND RELEVANCE

This analysis provides pediatric-specific dosing suggestions for hydroxychloroquine and remdesivir and raises concerns regarding hydroxychloroquine use for COVID-19 treatment because concentrations were less than those needed to mediate an antiviral effect.

Hydroxychloroquine in Patients with Rheumatic Disease Complicated by COVID-19: Clarifying Target Exposures and the Need for Clinical Trials

OBJECTIVE

To characterize hydroxychloroquine (HCQ) exposure in patients with rheumatic disease receiving longterm HCQ compared to target concentrations with reported antiviral activity against the coronavirus disease 2019 caused by SARS-CoV-2 (COVID-19).

METHODS

We evaluated total HCQ concentrations in serum and plasma from published literature values, frozen serum samples from a pediatric systemic lupus erythematosus trial, and simulated concentrations using a published pharmacokinetic model during pregnancy. For each source, we compared observed or predicted HCQ concentrations to target concentrations with reported antiviral activity against SARS-CoV-2.

RESULTS

The average total serum/plasma HCQ concentrations were below the lowest SARS-CoV-2 target of 0.48 mg/l in all studies. Assuming the highest antiviral target exposure (total plasma concentration of 4.1 mg/l), all studies had about one-tenth the necessary concentration for in vitro viral inhibition. Pharmacokinetic model simulations confirmed that pregnant adults receiving common dosing for rheumatic diseases did not achieve target exposures; however, the models predict that a dosage of 600 mg once a day during pregnancy would obtain the lowest median target exposure for most patients after the first dose.

CONCLUSION

We found that the average patient receiving treatment with HCQ for rheumatic diseases, including children and non-pregnant/pregnant adults, are unlikely to achieve total serum or plasma concentrations shown to inhibit SARS-CoV-2 in vitro. Nevertheless, patients receiving HCQ long term may have tissue concentrations far exceeding that of serum/plasma. Because the therapeutic window for HCQ in the setting of SARS-CoV-2 is unknown, well-designed clinical trials that include patients with rheumatic disease are urgently needed to characterize the efficacy, safety, and target exposures for HCQ.

Cefazolin pharmacokinetics in premature infants

OBJECTIVE

Pharmacokinetic (PK) data to guide cefazolin dosing in premature infants are virtually non-existent. Therefore, we aimed to characterize cefazolin PK in infants aged ≤32 weeks of gestation at birth.

STUDY DESIGN

We conducted a prospective, open-label PK and safety study of cefazolin in infants ≤32 weeks gestation from a University Medical Center. We administered intravenous cefazolin and collected both timed and scavenged blood samples. We analyzed data using non-linear mixed effect modeling and simulated several dosage regimens to achieve target concentrations against methicillin-susceptible Staphylococcus aureus.

RESULTS

We analyzed 40 samples from nine infants and observed that premature infants had lower clearance and greater volume of distribution for cefazolin compared to older children. The median (range) individual Bayesian estimates were 0.03 L/h/kg (0.01-0.08) for clearance and 0.39 L/kg (0.31-0.52) for volume.

CONCLUSION

Simulations suggested reduced cefazolin dosing based on postmenstrual age achieve target concentrations and potentially reduce unnecessary exposure.

Pharmacokinetics of Hydroxychloroquine in Pregnancies with Rheumatic Diseases

BACKGROUND

Hydroxychloroquine is an oral drug prescribed to pregnant women with rheumatic disease to reduce disease activity and prevent flares. Physiologic changes during pregnancy may substantially alter drug pharmacokinetics. However, the effect of pregnancy on hydroxychloroquine disposition and the potential need for dose adjustment remains virtually unknown.

METHODS

We performed a population-pharmacokinetic analysis using samples from the Duke Autoimmunity in Pregnancy Registry from 2013 to 2016. We measured hydroxychloroquine concentration using high-performance liquid chromatography/tandem mass spectrometry and analyzed data using non-linear mixed-effect modeling. We calculated differences between pregnancy and postpartum empirical Bayesian estimates using paired t tests. We computed steady-state concentration profiles for hydroxychloroquine during pregnancy and postpartum using individual clinical data and empirical Bayesian estimates developed from the final pharmacokinetic model.

RESULTS

We obtained 145 serum samples from 50 patients, 25 of whom had paired pregnancy and postpartum specimens. Five subjects had average concentrations (pregnancy and postpartum) < 100 ng/mL, consistent with medication non-adherence, and were excluded. The population estimated apparent volume of distribution was 1850 L/70 kg and estimated apparent clearance was 51 L/h. Compared with postpartum, median apparent volume of distribution increased significantly during pregnancy (p < 0.001), whereas apparent clearance and 24-h area under the curve did not change.

CONCLUSIONS

We developed a one-compartment population-pharmacokinetic model for hydroxychloroquine in pregnant women with rheumatic disease. Estimates for serum CL were within the expected range for plasma in non-pregnant adults. Because CL and 24-h area under the curve did not change during pregnancy compared with postpartum, our modeling in this small cohort does not support adjusting hydroxychloroquine dose during pregnancy.

Pharmacokinetics of ticarcillin-clavulanate in premature infants

Ticarcillin-clavulanate covers a broad spectrum of pathogens that are common in premature infants. In infants <30 weeks gestational age, pharmacokinetic data to guide ticarcillin-clavulanate dosing are lacking. We enrolled 15 premature infants <30 weeks gestational age, determined pharmacokinetic parameters, and performed dosing simulations to determine optimal dosing for ticarcillin-clavulanate. The infants had a median (range) postnatal age (PNA) of 18 days (6-44 days) and gestational age of 25 weeks (23-28 weeks). Clearance was lower in infants with a PNA <14 days (0.050 L/kg/h [range 0.043-0.075]) compared with a PNA ≥14-45 days (0.078 L/kg/h [0.047-0.100]), consistent with maturation of renal function. Dosing simulations determined that ticarcillin 75 mg/kg q12h (PNA <14 days) or q8h (PNA ≥ 14-45 days) achieved the target exposure for organisms with a minimum inhibitory concentration ≤16 μ/mL in >90% of simulated infants. For highly resistant organisms (minimum inhibitory concentration 32 μg/mL), increased dosing frequency or extended infusion are necessary.

Prescribing for Children With Rheumatic Disease: Perceived Treatment Approaches Between Pediatric and Adult Rheumatologists

OBJECTIVE

To compare practice patterns and prescribing differences for juvenile idiopathic arthritis (JIA) between adult rheumatologists (ARs) and pediatric rheumatologists (PRs), the perceived educational needs, and factors that enhance or impede co-management.

METHODS

Two parallel, cross-sectional surveys focusing on JIA were administered in 2009 to a random sample of 193 PRs and 500 ARs using the American College of Rheumatology membership file. Bivariate analysis was conducted for common items.

RESULTS

The response rate was 62.1% for ARs (n = 306) and 72.3% for PRs (n = 138). Only 23% of responding ARs (n = 69) reported caring for children with JIA. Of these, 94% strongly agreed/agreed feeling comfortable diagnosing JIA; however, only 76% felt comfortable treating JIA. Clinical vignettes highlighted several prescribing differences. Forty-eight percent of ARs and 31% of PRs felt medications to treat JIA did not have clear dosing guidelines. Though PRs initiated disease-modifying antirheumatic drugs and biologic agents earlier, treatments were similar after 3 months. To enhance co-management, 74% of pediatric respondents endorsed shared medical records.

CONCLUSION

Nearly one-quarter of surveyed ARs care for children with JIA, with most limiting their practice to older children. There was more discomfort in treating JIA than diagnosing it, and there were significant prescribing differences. Both provider types identified the need for better dosing and treatment resources. Updated management guidelines along with exposure to pediatric rheumatology in fellowship could reduce treatment differences and enhance the care of children with JIA. Shared medical records and improvement in reimbursement may optimize co-management.

Innovative Study Designs Optimizing Clinical Pharmacology Research in Infants and Children

Almost half of recent pediatric trials failed to achieve labeling indications, in large part because of inadequate study design. Therefore, innovative study methods are crucial to optimizing trial design while also reducing the potential harms inherent with drug investigation. Several methods exist to optimize the amount of pharmacokinetic data collected from the smallest possible volume and with the fewest number of procedures, including the use of opportunistic and sparse sampling, alternative and noninvasive matrices, and microvolume assays. In addition, large research networks using master protocols promote collaboration, reduce regulatory burden, and increase trial efficiency for both early- and late-phase trials. Large pragmatic trials that leverage electronic health records can capitalize on central management strategies to reduce costs, enroll patients with rare diseases on a large scale, and augment study generalizability. Further, trial efficiency and safety can be optimized through Bayesian adaptive techniques that permit planned protocol changes based on analyses of prior and accumulated data. In addition to these trial design features, advances in modeling and simulation have paved the way for systems-based and physiologically based models that individualize pediatric dosing recommendations and support drug approval. Last, given the low prevalence of many pediatric diseases, collecting deidentified genetic and clinical data on a large scale is a potentially transformative way to augment clinical pharmacology research in children.

Hydroxychloroquine Levels throughout Pregnancies Complicated by Rheumatic Disease: Implications for Maternal and Neonatal Outcomes

OBJECTIVE

Pregnancies in women with active rheumatic disease often result in poor neonatal outcomes. Hydroxychloroquine (HCQ) reduces disease activity and flares; however, pregnancy causes significant physiologic changes that may alter HCQ levels and lead to therapeutic failure. Therefore, our objective was to evaluate HCQ concentrations during pregnancy and relate levels to outcomes.

METHODS

We performed an observational study of pregnant patients with rheumatic disease who were taking HCQ from a single center during 2013-2016. Serum samples were analyzed using high-performance liquid chromatography/mass spectrometry. Primary HCQ exposure was categorized as nontherapeutic (≤ 100 ng/ml) or therapeutic (> 100 ng/ml). Categorical outcomes were analyzed using Fisher's exact test and continuous outcomes using linear regression models, Wilcoxon signed-rank test, Kruskal-Wallis test, t test, and ANOVA.

RESULTS

We analyzed 145 samples from 50 patients with rheumatic disease, 56% of whom had systemic lupus erythematosus (SLE). HCQ concentration varied widely among individuals at each trimester. Mean physician's global assessment scores in patients with SLE were significantly higher in those with average drug levels ≤ 100 ng/ml compared to > 100 ng/ml (0.93 vs 0.32, p = 0.01). Of patients with SLE, 83% with average drug levels ≤ 100 ng/ml delivered prematurely (n = 6), compared to only 21% with average levels > 100 ng/ml (n = 19; p = 0.01). HCQ levels were not associated with prematurity or disease activity in non-SLE patients.

CONCLUSION

With both high and low HCQ levels associated with preterm birth and disease activity in SLE, further study is necessary to understand HCQ disposition throughout pregnancy and to clarify the relationship between drug levels and outcomes.

Increasing contraception use among women receiving teratogenic medications in a rheumatology clinic

Teratogenic medications are often prescribed to women of childbearing age with autoimmune diseases. Literature suggests that appropriate use of contraception among these women is low, potentially resulting in high-risk unintended pregnancies. Preliminary review in our clinic showed suboptimal documentation of women's contraceptive use. We therefore designed a quality improvement initiative to target three process measures: documentation of contraception usage and type, contraception counselling and provider action after counselling. We reviewed charts of rheumatology clinic female patients aged 18-45 over the course of 10 months; for those who were on teratogenic medications (methotrexate, leflunomide, mycophenolate and cyclophosphamide), we looked for evidence of documentation of contraception use. We executed multiple plan-do-study-act (PDSA) cycles to develop and evaluate interventions, which centred on interprofessional provider education, modification of electronic medical record (EMR) templates, periodic provider reminders, patient screening questionnaires and frequent feedback to providers on performance. Among eligible patients (n=181), the baseline rate of documentation of contraception type was 46%, the rate of counselling was 30% and interventions after counselling occurred in 33% of cases. Averaged intervention data demonstrated increased provider performance in all three domains: documentation of contraception type increased to 64%, counselling to 45% and provider action to 46%. Of the patients with documented contraceptives, 50% used highly effective, 27% used effective and 23% used ineffective contraception methods. During this project, one unintentional pregnancy occurred in a patient on methotrexate not on contraception. Our interventions improved three measures related to contraception counselling and documentation, but there remains a need for ongoing quality improvement efforts in our clinic. This high-risk population requires increased provider engagement to improve contraception compliance, coupled with system-wide EMR changes to increase sustainability.

Clinical Trial Design in Juvenile Idiopathic Arthritis

Randomized clinical trials provide the gold standard evidence base to guide clinical practice. Despite major advances in trial design, pediatric clinical trials are still difficult to perform and pose unique challenges, including the need to consider the impact of developmental changes in trial design. Advances within pediatric rheumatology combined with the need to comply with legislative requirements have driven new approaches to performing pediatric clinical trials such as utilization of large research networks, incorporation of patient and family stakeholders in the planning and implementation of clinical trials, and the development of novel trial designs. The expansion of available biological therapeutics that now includes biosimilar drugs highlights the important and difficult balance of providing new and cost-effective drugs to children while ensuring safety in a vulnerable population. Future advances in juvenile idiopathic arthritis (JIA) clinical trials will likely be the application of precision medicine based on biologic, rather than phenotypic, classification of JIA, with improved understanding of pediatric clinical pharmacology. Clinical trial simulations and comparative effectiveness studies are important supplements to traditional clinical trials, permitting efficient studies and results that are more generalizable.

Profile of adalimumab and its potential in the treatment of uveitis

Uveitis refers to the presence of intraocular inflammation, and as a strict definition compromises the iris and ciliary body anteriorly and the choroid posteriorly (the uvea). Untreated, uveitis can lead to visual loss or blindness. The etiology of uveitis can include both infectious and noninfectious (usually immune-mediated) causes, the latter of which are often mediated predominantly by Th1 CD4⁺ T-cells that secrete proinflammatory cytokines. Tumor necrosis factor-alpha (TNF-α) is a proinflammatory cytokine involved in the pathogenesis of uveitis, which at high concentrations can cause excess inflammation and tissue damage. Adalimumab is a recombinant human IgG1 monoclonal antibody specific for human TNF-α. Historically, corticosteroids and methotrexate were used to treat uveitis; however, newer biologic agents such as adalimumab have revolutionized therapy for noninfectious uveitis. Adalimumab has shown efficacy in treating refractory uveitis in multiple settings, including idiopathic disease, juvenile idiopathic arthritis, sarcoidosis, Behçets disease, and uveitis secondary to spondyloarthropathies, among several other noninfectious uveitis conditions. In this paper, we will review the profile of adalimumab, the role of TNF-α in uveitis, discuss safety data, and summarize key articles evaluating the efficacy of adalimumab in treating uveitis secondary to the most commonly associated autoimmune diseases.