Trough Plasma Concentrations Research Articles

A retrospective analysis to estimate trough concentrations of teicoplanin in patients with suspected or documented Gram-positive infections

Teicoplanin is a glycopeptide antibiotic commonly used to treat Gram-positive bacterial infections in the clinic. The aim of this study was to provide a therapeutic reference for the clinical application and dosage regimen adjustment of teicoplanin by identifying factors associated with its plasma trough concentration (Ctrough). A retrospective study was performed on patients with suspected or documented Gram-positive infections who were hospitalized from November 2017 to January 2020 and treated with teicoplanin while undergoing routine therapeutic drug monitoring (TDM). A total of 112 Ctrough trough measurements were obtained from 72 patients were included in this study. SPSS software was used for correlation analysis and receiver operator characteristic curve (ROC) analysis. The Ctrough for teicoplanin showed statistically significant relationships (P<0.05) with PLT, Scr, CLcr, eGFR, BUN and Cys-C. ROC curve analysis revealed that CLcr and eGFR were more sensitive and specific for Ctrough compared to the other factors. These findings should be considered in the clinical application of teicoplanin and for its dosage adjustment.

Population Pharmacokinetics and Dosing Regimen Optimization of Linezolid in Cerebrospinal Fluid and Plasma of Post-operative Neurosurgical Patients

BackgroundLinezolid is a valuable therapeutic option for infections of the central nervous system caused by multi-drug resistant Gram-positive pathogens. Data regarding linezolid pharmacokinetics in cerebrospinal fluid from post-operative neurosurgical patients have revealed wide inter-individual variability. The objectives of this study were to establish a population pharmacokinetic model for linezolid in plasma and cerebrospinal fluid, as well as to optimize dosing strategies in this susceptible population. MethodsThis was a prospective pharmacokinetic study in post-operative neurosurgical patients receiving intravenous linezolid. Parallel blood and cerebrospinal fluid samples were collected and analyzed. The population pharmacokinetic modelling and Monte Carlo simulations were performed using the Phoenix NLME software. ResultsA two-compartment model (central plasma and cerebrospinal fluid compartments) fit the linezolid data well, with creatinine clearance and serum procalcitonin as significant variables. Linezolid demonstrated highly variable penetration into cerebrospinal fluid, with a mean cerebrospinal fluid/plasma ratio of 0.53. A strong correlation was found between plasma trough concentration and cerebrospinal fluid exposure of linezolid. Based on simulation results, optimal dosage regimens stratified by various renal functions and inflammatory status were proposed. ConclusionA modeling and simulating strategy was employed in dose individualization to improve the efficacy and safety of linezolid treatment.

The effect of therapeutic drug monitoring of risperidone and aripiprazole on weight gain in children and adolescents: the SPACe 2: STAR (trial) protocol of an international multicentre randomised controlled trial

BackgroundAntipsychotic drugs are an important part of the treatment of irritability and aggression in children with an autism spectrum disorder (ASD). However, significant weight gain and metabolic disturbances are clinically relevant side effects of antipsychotic use in children. In the SPACe study, we showed positive correlations between both risperidone and aripiprazole plasma trough concentrations and weight gain over a 6-month period. The trial SPACe 2: STAR is designed as a follow-up study, in which we aim to research whether therapeutic drug monitoring in clinical practice can prevent severe weight gain, while retaining clinical effectiveness.MethodsSPACe 2: STAR is an international, multicentre, randomised controlled trial (RCT). One hundred forty children aged 6 to 18 who are about to start risperidone or aripiprazole treatment for ASD related behavioural problems will be randomised into one of two groups: a therapeutic drug monitoring (TDM) group, and a care as usual (CAU) group. Participants will be assessed at baseline and 4, 10, 24, and 52 weeks follow-up. In the TDM group, physicians will receive dosing advice based on plasma levels of risperidone and aripiprazole and its metabolites at 4 and 10 weeks. Plasma levels will be measured in dried blood spots (DBS). The primary outcome will be BMI z-score at 24 weeks after start of antipsychotic treatment. Among the secondary outcomes are effectiveness, metabolic laboratory measurements, levels of prolactin, leptin and ghrelin, extrapyramidal side effects, and quality of life.DiscussionThis will be the first RCT evaluating the effect of TDM of antipsychotic drugs in children and adolescents. Thus, findings from SPACe 2: STAR will be of great value in optimising treatment in this vulnerable population.Trial registrationClinicalTrials.gov Identifier: NCT05146245. EudraCT number: 2020–005450-18. Sponsor protocol name: SPACe2STAR. Registered 8 June 2021. Protocol Version 6, Protocol date: 18 august 2022.

Relationship between raltegravir trough plasma concentration and virologic response and the impact of therapeutic drug monitoring during pregnancy.

Limited data is available on raltegravir (RAL) pharmacokinetics during pregnancy and the value of therapeutic drug monitoring (TDM) in pregnancy is unknown. This study aims to describe RAL trough plasma concentrations (Ctrough) during pregnancy and review the impact of RAL TDM on outcomes. Women from the prospective mother-infant HIV cohort of Mother and Children's Infectious Diseases Center who received RAL during their pregnancy between 2011-2020 were included. TDM reports were reviewed and Ctrough values estimated when possible, using historical RAL half-lives. We included 76 pregnant women of which 47 underwent TDM. We observed a significant association between virological response and Ctrough (p-value .034) with an increase of 0.1mg/L corresponding to a 2.96 reduction in the risk of having a detectable viral load. The results indicated that in pregnant women a RAL Ctrough threshold of 0.04mg/L has a higher specificity (75%) as compared to our current Ctrough target value of 0.02mg/L (25%) and an acceptable sensitivity (77%). No significant differences were observed between Ctrough at each trimester. When comparing pregnancies with and without TDM, no statistically significant differences were observed in the virologic response during pregnancy and at delivery, or with the need for triple antiretroviral prophylaxis in newborns. An association between RAL Ctrough and viral load was observed and achieving a RAL Ctrough of 0.04mg/L or greater is a predictor of virologic response in pregnant women. The impact of TDM in pregnancy, however, could not be demonstrated.

The use of Ctrough for the therapeutic drug monitoring of olaparib in patients with ovarian cancer.

Olaparib is the poly-[Adenosine diphosphate ribose (ADP-ribose)] polymerase inhibitor (PARPI) used in maintenance therapy of patients with platinum-sensitive ovarian cancer with mutations in breast cancer genes 1/2 (BRCA1/2). Oncologists still do not have recommendations of treatment depending on efficient plasma concentrations of the PARP inhibitor. The aim of the study was the assessment of plasma trough concentrations of olaparib at steady state (Ctrough) in ovarian cancer patients. The severity of olaparib adverse effects (AEs) was noted. The retrospective study involved 33 patients [mean standard deviation (SD)]; age 57.0 (8.4) years; weight 68.7 (13.7) kg; and body mass index (BMI) 26.4 (4.9) kg/m2, with ovarian cancer treated with olaparib (tablets in dose 300 mg/12 h, 250 mg/12 h, 200 mg/12 h or capsules 400 mg/12 h, 200 mg/12 h, 100 mg/12 h). Plasma drug levels were measured by HPLC-UV method (λ = 254 nm; Symmetry C8 column; gradient flow). The severity of olaparib AEs was assessed by Common Terminology Criteria for Adverse Events (CTCAE) v5.0 scale. Drug interactions were analyzed. In total, 130 measurements (n) of Ctrough were determined in 33 patients (median sample frequency per patient was 4). The olaparib Ctrough in patients with AEs was 87.840-7,213.262 ng/mL [coefficient of variation (CV) = 91%], in patients without AEs 48.021-7,073.350 ng/mL (CV = 88%). AEs were the following: fatigue (modest, n = 4, severe, n = 2), anemia (grade G1 n = 66, G2 n = 6, G3 n = 3), neutropenia (grade G1 n = 15, G2 n = 4), prediabetes (n = 1). There was a correlation between Ctrough and olaparib-induced fatigue (p = 0.0015). The lower values of dose-adjusted olaparib concentrations (p = 0.0121) and dose/kg-adjusted olaparib concentrations (p = 0.0389) were correlated with higher grade of neutropenia. There was a correlation between Ctrough, expressed as ng/ml, ng/ml/mg or ng/ml/mg/kg, and fatigue degree, but not anemia. Patients with neutropenia had statistically significant lower plasma concentrations of olaparib.

Central Nervous System Toxicity of Voriconazole: Risk Factors and Threshold - A Retrospective Cohort Study.

Voriconazole (VRC) is an antifungal agent which is used for treatment and prophylaxis of invasive fungal infections. The common clinical adverse reactions mainly include central nervous system (CNS) toxicity and abnormal liver function. These adverse reactions limit the clinical use of voriconazole to a certain extent. Therefore, the aim of this study was to analyze the risk factors of voriconazole neurotoxic side effects and to determine the plasma trough concentration (C min) threshold of voriconazole-induced CNS toxicity, so as to improve the safety of voriconazole treatment. This study retrospectively collected the clinical data of 165 patients who received voriconazole and underwent therapeutic drug monitoring (TDM). CNS toxicity was defined using the National Cancer Institute (NCI) criteria, logistic regression was used to analyze the risk factors of CNS toxicity, classification and Regression tree (CART) model was used to determine the C min threshold for CNS toxicity. Voriconazole-related CNS toxicity occurred during treatment in 34 of 165 patients (20.6%) and the median time from administration to onset of CNS toxicity was 6 days (range, 2-19 days). The overall incidence of CNS toxicity was 20.6% (34/165), including visual disturbances in 4.8% (8/165) and nervous system disorders in 15.8% (26/165). C min significantly affects the occurrence of CNS toxicity and the threshold of C min for voriconazole CNS toxicity was determined to be 4.85 mg/L, when C min >4.85 mg/L and ≤4.85 mg/L, the incidence of CNS was 32.9% and 11.6%, respectively. Voriconazole trough concentration of C min is an independent risk factor for CNS toxicity, and the threshold of C min for CNS toxicity is 4.85mg/L. TDM should be routinely performed in patients with clinical use of voriconazole to reduce the occurrence of CNS toxicity of voriconazole.

Impact of trough abiraterone level on adverse events in patients with prostate cancer treated with abiraterone acetate.

We assessed the impact of plasma trough concentrations of abiraterone (ABI) and its metabolite Δ4-abiraterone (D4A) and related polymorphisms on adverse events (AEs) in patients with metastatic prostate cancer who received abiraterone acetate (AA). This prospective study enrolled patients with advanced prostate cancer treated with AA between 2016 and 2021. Plasma trough concentrations of ABI and D4A were measured using high-performance liquid chromatography. The impact of HSD3B1 rs1047303, SRD5A2 rs523349, and cytochrome P450 family 3A member 4 rs2242480 polymorphisms on plasma concentrations of ABI and D4A and the incidence of AEs were also assessed. In 68 patients treated with AA, the median ABI and D4A concentrations were 18.1 and 0.94ng/mL, respectively. The high plasma trough concentration of ABI (≥ 20.6ng/mL) was significantly associated with the presence of any AE and its independent risk factor based on multivariable analysis (odds ratio, 7.20; 95% confidence interval (CI): 2.20-23.49). Additionally, a high plasma trough concentration of ABI was an independent risk factor of time to withdraw AA (hazard ratio, 4.89; 95% CI: 1.66-14.38). The risk alleles of three polymorphisms were not statistically associated with the ABI and D4A concentrations and the incidence of AEs. The plasma trough concentration of ABI is associated with the presence of AEs and treatment failure after AA administration. ABI concentration monitoring may be useful in patients with prostate cancer who received AA.

The impact of ABCB1 and CES1 polymorphisms on the safety of dabigatran in patients with non-valvular atrial fibrillation

BackgroundThis study aimed to analyze associations between genetic variants and plasma concentrations along with clinical outcomes in dabigatran in patients with non-valvular atrial fibrillation (NVAF).MethodsWe conducted a prospective study and enrolled NVAF patients treated with dabigatran in the real world. A total of 86 patients treated with 110 mg DE twice daily were recruited for this study. Blood samples were obtained from each patient and used for genotyping and determination of plasma dabigatran concentration. All bleeding and thromboembolic complications were recorded during the 1.5 years of follow-up.ResultsEighty-three patients provided samples at the trough plasma level of dabigatran, and 58 patients provided samples at the peak plasma level of dabigatran. There was a significant association between the CES1 SNP rs8192935 and trough plasma concentrations of dabigatran (P = 0.013). Our results showed that the CES1 SNP rs8192935 significantly influenced dabigatran trough concentrations in the Chinese population, and carriers of the G allele had increased trough plasma concentrations of dabigatran compared to noncarriers. The ABCB1 SNP c.2482-2236G > A (rs4148738) was associated with major bleeding events in the addictive model (P = 0.046, OR = 3.29) and dominant model (P = 0.040, OR = 8.17). Additionally, the ABCB1 SNP c.3435 C > T (rs1045642) was associated with the incidence of major bleeding events in the addictive model (P = 0.043, OR = 3.34) and dominant model (P = 0.046, OR = 7.77). However, no significant associations were found between all the SNPs and the incidence of minor bleeding events.ConclusionOur results indicated that the CES1 polymorphism rs8192935 was associated with trough plasma concentrations of dabigatran. Carriers of the G allele had increased trough plasma concentrations of dabigatran compared to noncarriers. The ABCB1 polymorphisms rs4148738 and rs1045642 were associated with an increased risk for major bleeding events for the first time in a Chinese population.

Screening for impulse control disorders in Parkinson's disease and dopamine agonist use: a study of pharmacokinetic and psychological risk factors.

Dopamine agonist (DA) use is considered the main risk factor for impulse control disorder (ICD) development in Parkinson's disease (PD). Besides DAs, personality traits and cognitive features may represent risk factors for ICDs. The primary aim of this study was to investigate differences in DA plasma concentrations in PD patients with and without a positive screening for ICDs according to validated tools. The secondary aim was to compare the psychological profile between ICD positive and negative screened patients. PD patients receiving chronic DA therapy were screened for ICDs according to the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease (QUIP). Blood samples for measurement of DA (pramipexole, ropinirole, rotigotine) trough plasma concentrations were drawn in the morning, at mean 16-19h from the last DA dose. Patients' psychological profile was investigated by Millon Clinical Multiaxal Inventory III and Barratt Impulsiveness Scale (BIS-11). One hundred and five PD patients were enrolled. Forty-one patients (39%) were QUIP positive, mainly for binge eating and hobbyism. Median plasma concentrations of pramipexole (n = 71, 66%), ropinirole (n = 21, 19%), and rotigotine (n = 16, 15%) were similar between QUIP positive and negative patients. QUIP positive patients showed higher motor impulsiveness (p = 0.04) and tended to higher total impulsiveness (p = 0.05). This is the first prospective study to evaluate the relationship between DA plasma concentrations and ICDs risk in PD patients. DA plasma levels were overlapping between QUIP positive and negative patients. BIS-11, particularly the motor impulsiveness subscale, might be a useful screening tool in PD patients eligible for DA therapy.

Population pharmacokinetics of voriconazole and initial dosage optimization in patients with talaromycosis.

The high variability and unpredictability of the plasma concentration of voriconazole (VRC) pose a major challenge for clinical administration. The aim of this study was to develop a population pharmacokinetics (PPK) model of VRC and identify the factors influencing VRC PPK in patients with talaromycosis. Medical records and VRC medication history of patients with talaromycosis who were treated with VRC as initial therapy were collected. A total of 233 blood samples from 69 patients were included in the study. A PPK model was developed using the nonlinear mixed-effects models (NONMEM). Monte Carlo simulation was applied to optimize the initial dosage regimens with a therapeutic range of 1.0–5.5 mg/L as the target plasma trough concentration. A one-compartment model with first-order absorption and elimination adequately described the data. The typical voriconazole clearance was 4.34 L/h, the volume of distribution was 97.4 L, the absorption rate constant was set at 1.1 h-1, and the bioavailability was 95.1%. Clearance was found to be significantly associated with C-reactive protein (CRP). CYP2C19 polymorphisms had no effect on voriconazole pharmacokinetic parameters. ‏Monte Carlo simulation based on CRP levels showed that a loading dose of 250 mg/12 h and a maintenance dose of 100 mg/12 h are recommended for patients with CRP ≤ 96 mg/L, whereas a loading dose of 200 mg/12 h and a maintenance dose of 75 mg/12 h are recommended for patients with CRP > 96 mg/L. The average probability of target attainment of the optimal dosage regimen in CRP ≤ 96 mg/L and CRP > 96 mg/L groups were 61.3% and 13.6% higher than with empirical medication, and the proportion of Cmin > 5.5 mg/L decreased by 28.9%. In conclusion, the VRC PPK model for talaromycosis patients shows good robustness and predictive performance, which can provide a reference for the clinical individualization of VRC. Adjusting initial dosage regimens based on CRP may promote the rational use of VRC.

Clinical validation of the two-point method for predicting vancomycin AUC based on peak and trough plasma concentrations.

Vancomycin area under the curve/minimum inhibitory concentration (AUC/MIC) has been proposed as a therapeutic drug monitoring (TDM) target to dose vancomycin. It is time-consuming to estimate AUCs using traditional methods. A two-point trough-peak method is more straightforward for calculating the vancomycin AUC. However, the technique and the AUC/MIC target have not been validated in Chinese patients. To compare the clinical outcomes of vancomycin therapy in Chinese older adults (aged > 60years) between the trough-only and the two-point peak-trough AUC TDM approaches. The patients were divided into study and control groups according to TDM approaches. A trough-based TDM was used in the control group (target trough level 15-20mg/L). Stanford University has provided a method to predict vancomycin AUC using peak-valley concentration alone (two-point method). A two-point trough-peak TDM approach was employed in the study group (target AUC/MIC ≥ 400). The effect of vancomycin was evaluated in terms of clinical findings, laboratory values, and bacteriologic responses. The effects of treatment and kidney functions were compared between the two groups. A total of 389 patients met the study inclusion criteria, and 189 were excluded based on the exclusion criteria. Of the 200 patients, 80 received the two-point TDM approach (the study group), and 120 were monitored using the trough-based approach (the control group). The average age was 69.8 ± 7.1years. Staphylococcus aureus (34%) was the most common Gram-positive bacteria. No vancomycin-related nephrotoxicity was observed in either group. The percentages of patients with an excellent response to vancomycin therapy were significantly higher in the study group than in the control group, 90% (72/80) versus 73.3% (88/120),P = 0.0039. The two-point peak-trough method is practical for obtaining vancomycin AUC. The AUC/MIC ≥ 400 target demonstrates treatment effectiveness and safety in older Chinese patients.

A randomized, open-label trial of combined nitazoxanide and atazanavir/ritonavir for mild to moderate COVID-19.

BackgroundThe nitazoxanide plus atazanavir/ritonavir for COVID-19 (NACOVID) trial investigated the efficacy and safety of repurposed nitazoxanide combined with atazanavir/ritonavir for COVID-19.MethodsThis is a pilot, randomized, open-label multicenter trial conducted in Nigeria. Mild to moderate COVID-19 patients were randomly assigned to receive standard of care (SoC) or SoC plus a 14-day course of nitazoxanide (1,000 mg b.i.d.) and atazanavir/ritonavir (300/100 mg od) and followed through day 28. Study endpoints included time to clinical improvement, SARS-CoV-2 viral load change, and time to complete symptom resolution. Safety and pharmacokinetics were also evaluated (ClinicalTrials.gov ID: NCT04459286).ResultsThere was no difference in time to clinical improvement between the SoC (n = 26) and SoC plus intervention arms (n = 31; Cox proportional hazards regression analysis adjusted hazard ratio, aHR = 0.898, 95% CI: 0.492–1.638, p = 0.725). No difference was observed in the pattern of saliva SARS-CoV-2 viral load changes from days 2–28 in the 35% of patients with detectable virus at baseline (20/57) (aHR = 0.948, 95% CI: 0.341–2.636, p = 0.919). There was no significant difference in time to complete symptom resolution (aHR = 0.535, 95% CI: 0.251–1.140, p = 0.105). Atazanavir/ritonavir increased tizoxanide plasma exposure by 68% and median trough plasma concentration was 1,546 ng/ml (95% CI: 797–2,557), above its putative EC90 in 54% of patients. Tizoxanide was undetectable in saliva.ConclusionNitazoxanide co-administered with atazanavir/ritonavir was safe but not better than standard of care in treating COVID-19. These findings should be interpreted in the context of incomplete enrollment (64%) and the limited number of patients with detectable SARS-CoV-2 in saliva at baseline in this trial.Clinical trial registration[https://clinicaltrials.gov/ct2/show/NCT04459286], identifier [NCT04459286].

Plasma lacosamide monitoring in children with epilepsy: Focus on reference therapeutic range and influencing factors.

BackgroundLacosamide (LCM) is a newer anti-seizure medication (ASM) that was approved in China in 2018, but its real-world clinical data and plasma concentrations in Chinese children with epilepsy are very limited. Of note, the reference range for routine LCM therapeutic drug monitoring is still unknown. The purpose of this study was to investigate the efficacy and safety of LCM as a monotherapy or an adjunctive treatment with other ASMs and to evaluate the potential factors affecting its efficacy and variable LCM plasma concentrations in Chinese children with epilepsy.MethodsChildren with epilepsy (<18 years) with routine plasma LCM monitoring from March 2019 to December 2021 at the Department of Pharmacy, Children's Hospital of Nanjing Medical University were retrospectively collected. Clinical data were obtained from the hospital information system.Results76 pediatric patients (52 males) were finally enrolled. Mean age was 7.9 years (1.3–17.3 years) with a mean dose of LCM 6.3 mg/kg/day (2.0–11.3 mg/kg/day). The TDM data as a whole showed that the median plasma trough concentration (C0) was 3.42 μg/mL (1.25–8.31 μg/mL). A 6-month LCM add-on therapy produced 70% of patients achieving ≥50% seizure frequency reductions, and the number was 81% for the one-year follow-up findings. Interestingly, more patients who took LCM monotherapy achieved seizure freedom over the same periods of follow-up observations. Under maintenance dosages, approximately 92.1% of the C0 values were 2.0–7.0 μg/mL. The plasma-C0-to-daily dose (C0/Dose) ratio was significantly associated with age and body weight (BW). The C0/Dose ratio in patients aged 1– ≤ 6 and 6– ≤ 12 years was significantly higher by 81% and 29% than those aged 12– ≤ 18 years, respectively. The C0/Dose ratio in patients with a BW of ≥40 kg was 1.7-fold lower than in patients with a BW of ≤ 20 kg. In addition, complex LCM-ASMs interactions were observed. Oxcarbazepine significantly decreased the C0/Dose ratio of LCM by 28%.ConclusionThis retrospective study confirmed the effectiveness and tolerability of the LCM treatment used alone or with other ASMs in children with focal epilepsy. Children with higher BW and older age have lower C0/Dose ratio. Complex drug interactions between LCM and other concomitant ASMs were revealed. Notably, based on the data in our hands, the reference range, i.e., 2.0–7.0 μg/mL, for routine LCM monitoring may be feasible. The real-world evidence of this study supports LCM as a promising option in children with focal epilepsy.

A rapid and sensitive ultra-performance liquid chromatography tandem mass spectrometry method for determination of anlotinib in plasma and dried blood spots: Method development, validation, and clinical application.

Anlotinib is a multi-target tyrosine kinase inhibitor, approved in China for treating several cancer types. Dose individualization based on therapeutic drug monitoring (TDM) is a useful tool to reduce toxicity. However, it is not convenient for patients to go to hospital for routine TDM via venous blood sampling at a certain time. An ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for determination of anlotinib in human plasma and dried blood spot (DBS), characterized by simple sample preparation, high sensitivity, and short analysis time. The assay was validated in the concentration range of 0.2-200 ng/mL in plasma and 5-1000 ng/mL in DBS. This method was applied to monitor anlotinib exposure levels in patients with advanced biliary tract cancer (BTC) and non-small cell lung cancer (NSCLC). The trough plasma concentration (Ctrough ) of anlotinib was highly variable among BTC patients with coefficients of variation (CV) of 47.5%. DBS and venous blood samples were also collected from NSCLC patients to determine whether DBS sampling is a viable alternative sampling approach. Pearson correlation coefficient (R) between DBS and plasma concentration was 0.985. Bland-Altman plot demonstrated that the difference between estimated and measured plasma concentration was -2.9%. And 87% of sample pairs had a maximal deviation of ±20%. Anlotinib exhibits a high inter-individual variability in plasma exposure, and DBS sampling could be a promising tool for TDM of anlotinib.

1184P Improving the tolerability of osimertinib by identifying its toxic limit

Osimertinib is the cornerstone in the treatment of epidermal growth factor receptor-mutated non-small cell lung cancer (NSCLC). Nonetheless, ±25% of patients experience severe treatment-related toxicities. Currently, it is impossible to identify patients at risk of severe toxicity beforehand. We hence aimed to study the relationship between osimertinib exposure and severe toxicity, and to identify a safe toxic limit for a preventive dose reduction. In this real-life prospective cohort study, patients with NSCLC treated with osimertinib were followed for severe toxicity (grade ≥3 toxicity, dose reduction or discontinuation, hospital admission, or treatment termination). Blood for pharmacokinetic analyses was withdrawn during every out-patient visit. To quantify individual exposure to osimertinib, a population-pharmacokinetic model was developed. Primary endpoint was the correlation between osimertinib clearance (exposure) and severe toxicity. Secondary endpoint was the exposure-efficacy relationship, defined as progression-free (PFS) and overall survival (OS). In total, 819 samples from 159 patients were included in the analysis. Multivariate competing risk analysis showed osimertinib clearance (c.q. exposure) to be significantly correlated with severe toxicity (hazard ratio (HR) 0.93, 95% CI 0.88 – 0.99). An ROC-curve showed the optimal toxic limit to be 259 ng/mL osimertinib. This target concentration divides the cohort in two groups: the risk of severe toxicity in the >259 ng/mL group is 34% versus 14% in the <259 ng/mL group. A 50% dose reduction in the high-exposure group - i.e. 25.8% of the total cohort - would reduce the risk of severe toxicity by 53%. Correlation of the first plasma trough concentrations in collected in the first two months of treatment revealed a similar difference in severe toxicity (31% versus 17%), when dividing the cohort in two by the toxic limit of 259 ng/mL osimertinib. Osimertinib exposure was not significantly associated with PFS nor OS. Osimertinib exposure is highly correlated with occurrence of severe toxicity. To optimize tolerability, patients above the toxic limit concentration of 259 ng/mL could benefit from a preventive dose reduction, without fear for diminished effectiveness.

Exposure-Response Analysis of Osimertinib in Patients with Advanced Non-Small-Cell Lung Cancer.

High interindividual variability (IIV) of the clinical response to epidermal growth factor receptor (EGFR) inhibitors such as osimertinib in non-small-cell lung cancer (NSCLC) might be related to the IIV in plasma exposure. The aim of this study was to evaluate the exposure–response relationship for toxicity and efficacy of osimertinib in unselected patients with advanced EGFR-mutant NSCLC. This retrospective analysis included 87 patients treated with osimertinib. Exposure–toxicity analysis was performed in the entire cohort and survival analysis only in second-line patients (n = 45). No significant relationship between occurrence of dose-limiting toxicity and plasma exposure was observed in the entire cohort (p = 0.23, n = 86). The median overall survival (OS) was approximately two-fold shorter in the 4th quartile (Q4) of osimertinib trough plasma concentration (>235 ng/mL) than in the Q1–Q3 group (12.2 months [CI95% = 8.0–not reached (NR)] vs. 22.7 months [CI95% = 17.1–34.1]), but the difference was not statistically significant (p = 0.15). To refine this result, the exposure–survival relationship was explored in a cohort of 41 NSCLC patients treated with erlotinib. The Q4 erlotinib exposure group (>1728 ng/mL) exhibited a six-fold shorter median OS than the Q1–Q3 group (4.8 months [CI95% = 3.3-NR] vs. 22.8 months (CI95% = 10.6–37.4), p = 0.00011). These results suggest that high exposure to EGFR inhibitors might be related to worse survival in NSCLC patients.

1130P Real-world data of osimertinib (osi) for the treatment of metastatic epidermal growth factor receptor (EGFR+) non-small cell lung cancer (NSCLC) patients (pts), with a focus on age, body mass index (BMI) and trough levels

For pts with metastatic NSCLC and a sensitizing EGFR mutation, osi is standard treatment, either in first line (1L) or beyond (2L+, if T790M+). Limited osi efficacy data is available in relation to plasma trough levels, as well as elderly or those with low or high BMI. Retrospective Dutch multicentre (two academic, one non-academic) study. Eligible: pts ≥18 years, with metastatic EGFR+ NSCLC regularly treated with osi. Start date of osi was used as index date, data was extracted from medical files. Primary endpoint: progression free survival (PFS). Secondary endpoint: overall survival (OS), objective response rate (ORR, RECIST v1.1) and disease control rate (DCR). Kaplan-Meier and multivariate Cox proportional hazard models were used to compare different subgroups for age, BMI and steady state plasma trough levels (Cmin,SS), measured <3 months (m) before disease progression (age [<70 / ≥70], BMI [<18.5 / 18.5 – 24.9 / 25.0 – 29.9 / >30] and plasma trough level [<149 / 149 – 259 / >259]). In total 294 pts were included: mean age 67 years (range = 29 – 87 years), mean BMI 25.3 (range = 17.6 – 67.1), 35% male, 90% Caucasian, 54% exon 19 deletion, 30% L858R, 17% other. Osi was given in 1L (n = 118, 40%), 2L (n = 134, 46%) or beyond (3L+, n=42, 14%). Median PFS was 14.6 m (95% CI = 10.2 – 20.0) (1L), 13.7 m (95% CI = 11.1 – 15.6) (2L) and 8.7 m (95% CI = 5.1 – 12.7) (3L+). ORR and DCR were similar in all lines (1L: 68% and 96%, 2L: 62% and 93% and 3L+: 69% and 91%). Pts ≥70 years at osi start achieved similar PFS and OS compared to pts <70 years (PFS: aHR = 0.93; 0.68 – 1.28; OS: aHR = 1.14; 0.77 – 1.68). Low BMI (<18.5) led to lower absolute effectiveness (PFS and OS), but not statistically significant, due to the low number of pts in the subgroup (n = 8). A high plasma trough concentration was associated with lower PFS (aHR = 1.92, 95% CI = 1.10 – 3.37). PFS and OS with 1L osi were lower compared to those found in the FLAURA trial, while in 2L survival was slightly longer in daily practice. Age was not associated with PFS, while a low BMI and a high Cmin,SS may be correlated with worse treatment outcomes on osi.

Evaluating linezolid dose regimens against methicillin-resistant Staphylococcus aureus based on renal function in populations with different body weight.

Linezolid is an alternative first-line agent for MRSA pneumonia. This study assessed whether dose adjustments of linezolid against methicillin-resistant Staphylococcus aureus (MRSA) infections were needed based on renal function in populations with different body weight. Monte Carlo simulations were conducted to evaluate renal function in relation to the probability of target attainment (PTA) in three population groups with different body weight. Area under the concentration time curve (AUC)/ minimum inhibitory concentration (MIC) ratio and percentage of time above the MIC (%T > MIC) were regarded as pharmacokinetic/pharmacodynamic targets. The PTA and cumulative fractions of response (CFR) were calculated to assess the efficacy. Regarding safety, trough plasma concentration (Cmin ) > 8mg/L was used as target for toxicity. Using AUC/MIC >100 as the target pharmacodynamic (PD) index, the CFR of linezolid at the standard dose (600 mg every 12 h [q12h]) were 57.01%, 93.22%, and 99.93% in patients with normal renal function, patients with renal dysfunction and low body weight patients with renal dysfunction, respectively. Using 100%T> MIC as the target PD index, all the CFR of three population groups were more than 90% at the standard dose. The percentages of Cmin > 8mg/L at the standard dose of linezolid were 24.16%, 53.24%, and 90.10% in three population groups on day 7. The risk of thrombocytopenia of linezolid was extremely higher in low body weight patients with renal impairment when receiving standard linezolid dose compared with patients with normal renal function. 450 mg q12h and 300 mg q12h might be effective and safe against MRSA infection in patients with renal dysfunction and low body weight patients with renal dysfunction, respectively.

Pharmacogenetic Expression of CYP2C19 in a Pediatric Population

Genetic variability in CYP2C19 may be associated with both lack of efficacy and toxicity of drugs due to its different metabolic status based on the presence of particular alleles. This literature review summarizes current knowledge relative to the association or treatment adaptation based on CYP2C19 genetics in a pediatric population receiving drugs metabolized by CYP2C19, such as voriconazole, antidepressants, clopidogrel and proton pump inhibitors. Additionally, we also presented one of the approaches that we developed for detection of variant alleles in the CYP2C19 gene. A total of 25 articles on PubMed were retained for the study. All studies included pediatric patients (age up to 21 years) having benefited from an assessment of CYP2C19. CYP2C19 poor and intermediate metabolizers exhibit a higher trough plasma concentration of voriconazole, and PPIs compared to the rapid and ultra-rapid metabolizers. The pharmacogenetic data relative to CYP2C19 and clopidogrel in the pediatric population are not yet available. CYP2C19 poor metabolizers have a higher trough plasma concentration of antidepressants compared to the rapid and the ultra-rapid metabolizers. Modification of allele-specific PCR through the introduction of artificial mismatch is presented. CYP2C19 genotyping remains a powerful tool needed to optimize the treatment of children receiving voriconazole, PPIs, and anti-depressants.

Exposure-Response Analysis of Osimertinib in EGFR Mutation Positive Non-Small Cell Lung Cancer Patients in a Real-Life Setting.

Osimertinib, an irreversible inhibitor of the epidermal growth factor receptor (EGFR) is an important drug in the treatment of EGFR-mutation positive non-small cell lung cancer (NSCLC). Clinical trials with osimertinib could not demonstrate an exposure-efficacy relationship, while a relationship between exposure and toxicity has been found. In this study, we report the exposure-response relationships of osimertinib in a real-life setting. A retrospective observational cohort study was performed, including patients receiving 40-80mg osimertinib as ≥ 2 line therapy and from whom pharmacokinetic samples were collected during routine care. Trough plasma concentrations (Cmin,pred) were estimated and used as a measure of osimertinib exposure. A previously defined exploratory pharmacokinetic threshold of 166µg/L was taken to explore the exposure-efficacy relationship. A total of 145 patients and 513 osimertinib plasma concentration samples were included. Median progression free survival (PFS) was 13.3 (95% confidence interval (CI):10.3-19.1) months and 9.3 (95% CI: 7.2-11.1) months for patients with Cmin,pred < 166µg/L and Cmin,pred ≥ 166µg/L, respectively (p = 0.03). In the multivariate analysis, a Cmin,pred < 166µg/L resulted in a non-statistically significant hazard ratio of 1.10 (95% CI: 0.60-2.01;p = 77). Presence of a EGFR driver-mutation other than the exon 19 del or L858R mutations, led to a shorter PFS with a hazard ratio of 2.89 (95% CI: 1.18-7.08;p = 0.02). No relationship between exposure and toxicity was observed (p = 0.91). In our real-life cohort, no exposure-response relationship was observed for osimertinib in the current dosing scheme. The feasibility of a standard lower fixed dosing of osimertinib in clinical practice should be studied prospectively.