PIPAC in patients with peritoneal metastases from gastrointestinal tract (PIPOX01): An open label, non-comparative phase 1/2 dose escalation and expansion trial.

BACKGROUND: Despite modern systemic chemotherapy, survival remains poor for patients with advanced isolated peritoneal metastases from the gastrointestinal tract. We aimed to assess the safety and efficacy of pressurized intraperitoneal aerosol chemotherapy (PIPAC) with oxaliplatin. PATIENTS AND METHODS: We conducted a phase 1/2, open label, non-comparative, dose escalation and expansion trial of PIPAC with oxaliplatin in patients with a peritoneal cancer index (PCI) of more than 5, 13 and 15 for respectively a gastric, small bowel and colorectal primary cancer, and who had received at least three months of systemic chemotherapy. PIPAC cycle lengths were 4-6 weeks with systemic chemotherapy allowed 15 days after each PIPAC. PCI and oxaliplatin tumor concentration were assessed every PIPAC cycle. The main endpoints were tolerability, tumor response, and survival. RESULTS: Between 2017 and 2020, 34 patients were enrolled in three centers, in this phase 1/2 study, of whom 25 were evaluable at the recommended dose determined in the phase I trial (90 mg/m2 plus systemic 5-FU). Before inclusion, patients received a median of 2 [1-4] chemotherapy lines and had a median PCI of 22.5 [7-29]. At this dose, the safety profile showed acceptable tolerability. Eight patients (32 %) had grade 3/4 treatment-related adverse events. Minor (grade 1/2) adverse events were mainly abdominal pain (n = 19, 76 %) and nausea (n = 16, 64 %). Median PFS was 6.1 months and median OS was 13 months. CONCLUSION: In patients with advanced and refractory peritoneal metastasis, PFS of 6.1 months is encouraging. A prospective randomized phase II study is required.

Eculizumab dose tapering should take into account the nonlinearity of its pharmacokinetics.

AIMS: Eculizumab is a monoclonal antibody targeting complement protein C5 used in renal diseases. As recommended dosing regimen leads to unnecessarily high concentrations in some patients, tailored dosing therapeutic drug monitoring was proposed to reduce treatment cost. The objectives of the present work were (i) to investigate the target-mediated elimination of eculizumab and (ii) whether a pharmacokinetic model integrating a nonlinear elimination allows a better prediction of eculizumab concentrations than a linear model. METHODS: We analysed 377 eculizumab serum concentrations from 44 patients treated for atypical haemolytic uraemic syndrome and C3 glomerulopathy with a population pharmacokinetic approach. Critical concentrations (below which a non-log-linear decline of concentration over time is evidenced) were computed to estimate the relevance of the target-mediated elimination. Simulations of dosing regimens were then performed to predict probabilities of target attainment (i.e. trough >100 mg/L). RESULTS: Pharmacokinetics of eculizumab was nonlinear and followed a mixture of first-order (CL = 1.318 mL/day/kg) and Michaelis-Menten elimination (Vmax = 26.07 mg/day, Km = 24.06 mg/L). Volume of distribution (72.39 mL/kg) and clearance were weight-dependent. Critical concentrations (Vmax/CL) ranged from 144.7 to 759.7 mg/L and were inversely related to body weight (P = .013). Nonlinearity was thus noticeable at therapeutic concentrations. Simulations predicted that 1200 mg of eculizumab every 21 days would allow 85% and 76% of patients to maintain a therapeutic exposure, for 50 or 90 kg body weight, respectively. CONCLUSIONS: Our study investigates the nonlinear elimination of eculizumab and discusses the importance of accounting for eculizumab target-mediated elimination in therapeutic drug monitoring.

Comprehensive analyses of immune tumor microenvironment in papillary renal cell carcinoma.

BACKGROUND: Papillary renal cell carcinoma (pRCC) is the most common non-clear cell RCC, and associated with poor outcomes in the metastatic setting. In this study, we aimed to comprehensively evaluate the immune tumor microenvironment (TME), largely unknown, of patients with metastatic pRCC and identify potential therapeutic targets. METHODS: We performed quantitative gene expression analysis of TME using Microenvironment Cell Populations-counter (MCP-counter) methodology, on two independent cohorts of localized pRCC (n=271 and n=98). We then characterized the TME, using immunohistochemistry (n=38) and RNA-sequencing (RNA-seq) (n=30) on metastatic pRCC from the prospective AXIPAP trial cohort. RESULTS: Unsupervised clustering identified two "TME subtypes", in each of the cohorts: the "immune-enriched" and the "immune-low". Within AXIPAP trial cohort, the "immune-enriched" cluster was significantly associated with a worse prognosis according to the median overall survival to 8 months (95% CI, 6 to 29) versus 37 months (95% CI, 20 to NA, p=0.001). The two immune signatures, Teff and JAVELIN Renal 101 Immuno signature, predictive of response to immune checkpoint inhibitors (CPI) in clear cell RCC, were significantly higher in the "immune-enriched" group (adjusted p<0.05). Finally, five differentially overexpressed genes were identified, corresponding mainly to B lymphocyte populations. CONCLUSION: For the first time, using RNA-seq and immunohistochemistry, we have highlighted a specific immune TME subtype of metastatic pRCC, significantly more infiltrated with T and B immune population. This "immune-enriched" group appears to have a worse prognosis and could have a potential predictive value for response to immunotherapy, justifying the confirmation of these results in a cohort of metastatic pRCC treated with CPI and in combination with targeted therapies. TRIAL REGISTRATION NUMBER: NCT02489695.

Relationship Between Cetuximab Target-Mediated Pharmacokinetics and Progression-Free Survival in Metastatic Colorectal Cancer Patients.

BACKGROUND AND OBJECTIVE: Cetuximab, an anti-epidermal growth factor receptor (EGFR) monoclonal immunoglobulin (Ig)G1 antibody, has been approved for the treatment of metastatic colorectal cancer (mCRC). The influence of target-antigen on cetuximab pharmacokinetics has never been investigated using target-mediated drug disposition (TMDD) modelling. This study aimed to investigate the relationship between cetuximab concentrations, target kinetics and progression-free survival (PFS). METHODS: In this ancillary study (NCT00559741), 91 patients with mCRC treated with cetuximab were assessed. Influence of target levels on cetuximab pharmacokinetics was described using TMDD modelling. The relationship between cetuximab concentrations, target kinetics and time-to-progression (TTP) was described using a joint pharmacokinetic-TTP model, where unbound target levels were assumed to influence hazard of progression by an Emax model. Mitigation strategies of concentration-response relationship, i.e., time-varying endogenous clearance and mutual influences of clearance and time-to-progression were investigated. RESULTS: Cetuximab concentration-time data were satisfactorily described using the TMDD model with quasi-steady-state approximation and time-varying endogenous clearance. Estimated target parameters were baseline target levels (R0 = 43 nM), and complex elimination rate constant (kint = 0.95 day-1). Estimated time-varying clearance parameters were time-invariant component of CL (CL0= 0.38 L/day-1), time-variant component of CL (CL1= 0.058 L/day-1) and first-order rate of CL1 decreasing over time (kdes = 0.049 day-1). Part of concentration-TTP was TTP-driven, where clearance and TTP were inversely correlated. In addition, increased target occupancy was associated with increased TTP. CONCLUSION: This is the first study describing the complex relationship between cetuximab target-mediated pharmacokinetics and PFS in mCRC patients using a joint PK-time-to-progression model. Further studies are needed to provide a more in-depth description of this relationship.

Infliximab Treatment Does Not Lead to Full TNF-α Inhibition: A Target-Mediated Drug Disposition Model.

BACKGROUND AND OBJECTIVE: Infliximab, an anti-tumour necrosis factor (TNF)-α monoclonal antibody, has been approved in chronic inflammatory disease, including rheumatoid arthritis, Crohn's disease and ankylosing spondylitis. This study aimed to investigate and characterise target-mediated drug disposition of infliximab and antigen mass turnover during infliximab treatment. METHODS: In this retrospective cohort of 186 patients treated with infliximab for rheumatoid arthritis, Crohn's disease or ankylosing spondylitis, trough infliximab concentrations were determined from samples collected between weeks 0 and 22 after treatment initiation. Target-mediated pharmacokinetics of infliximab was described using target-mediated drug disposition modelling. Target-mediated elimination parameters were determined for rheumatoid arthritis and Crohn's disease, assuming ankylosing spondylitis with no target-mediated elimination. RESULTS: The quasi-equilibrium approximation of a target-mediated drug disposition model allowed a satisfactory description of infliximab concentration-time data. Estimated baseline TNF-α amounts were similar in Crohn's disease and rheumatoid arthritis (R0 = 0.39 vs 0.46 nM, respectively), but infliximab-TNF complex elimination was slower in Crohn's disease than in rheumatoid arthritis (kint = 0.024 vs 0.061 day-1, respectively). Terminal elimination half-lives were 13.5, 21.5 and 16.5 days for rheumatoid arthritis, Crohn's disease and ankylosing spondylitis, respectively. Estimated amounts of free target were close to baseline values before the next infusion suggesting that TNF-α inhibition may not be sustained over the entire dose interval. CONCLUSIONS: The present study is the first to quantify the influence of target antigen dynamics on infliximab pharmacokinetics. Target-mediated elimination of infliximab may be complex, involving a multi-scale turnover of TNF-α, especially in patients with Crohn's disease. Additional clinical studies are warranted to further evaluate and fine-tune dosing approaches to ensure sustained TNF-α inhibition.

Functional pre-therapeutic evaluation by genome editing of variants of uncertain significance of essential tumor suppressor genes.

BACKGROUND: Targeted therapies in oncology are promising but variants of uncertain significance (VUS) limit their use for clinical management and necessitate functional testing in vitro. Using BRCA1 and BRCA2 variants, which have consequences on PARP inhibitor sensitivity, and POLE variants, potential biomarkers of immunotherapy response, we developed a rapid functional assay based on CRISPR-Cas9 genome editing to determine the functional consequences of these variants having potentially direct implications on patients' access to targeted therapies. METHODS: We first evaluated the functional impact of 26 BRCA1 and 7 BRCA2 variants by editing and comparing NGS results between the variant of interest and a silent control variant. Ten of these variants had already been classified as benign or pathogenic and were used as controls. Finally, we extended this method to the characterization of POLE VUS. RESULTS: For the 23 variants that were unclassified or for which conflicting interpretations had been reported, 15 were classified as functionally normal and 6 as functionally abnormal. Another two variants were found to have intermediate consequences, both with potential impacts on splicing. We then compared these scores to the patients' responses to PARP inhibitors when possible. Finally, to prove the application of our method to the classification of variants from other tumor suppressor genes, we exemplified with three POLE VUS. Among them, two were classified with an intermediate functional impact and one was functionally abnormal. Eventually, four POLE variants previously classified in databases were also evaluated. However, we found evidence of a discordance with the classification, variant p.Leu424Val being found here functionally normal. CONCLUSIONS: Our new rapid functional assay can be used to characterize the functional implication of BRCA1 and BRCA2 variants, giving patients whose variants were evaluated as functionally abnormal access to PARP inhibitor treatment. Retrospective analysis of patients' responses to PARP inhibitors, where accessible, was consistent with our functional score evaluation and confirmed the accuracy of our protocol. This method could potentially be extended to the classification of VUS from all essential tumor suppressor genes and can be performed within a timeframe compatible with clinical applications, thereby having a direct theranostic impact.

Infliximab Efficacy May Be Linked to Full TNF-α Blockade in Peripheral Compartment-A Double Central-Peripheral Target-Mediated Drug Disposition (TMDD) Model.

Infliximab is an anti-TNF-α monoclonal antibody approved in chronic inflammatory bowel diseases (IBD). This study aimed at providing an in-depth description of infliximab target-mediated pharmacokinetics in 133 IBD patients treated with 5 mg/kg infliximab at weeks 0, 2, 14, and 22. A two-compartment model with double target-mediated drug disposition (TMDD) in both central and peripheral compartments was developed, using a rich database of 26 ankylosing spondylitis patients as a reference for linear elimination kinetics. Population approach and quasi-steady-state (QSS) approximation were used. Concentration-time data were satisfactorily described using the double-TMDD model. Target-mediated parameters of central and peripheral compartments were respectively baseline TNF concentrations (RC0 = 3.3 nM and RP0 = 0.46 nM), steady-stated dissociation rates (KCSS = 15.4 nM and KPSS = 0.49 nM), and first-order elimination rates of complexes (kCint = 0.17 day-1 and kPint = 0.0079 day-1). This model showed slower turnover of targets and infliximab-TNF complex elimination rate in peripheral compartment than in central compartment. This study allowed a better understanding of the multi-scale target-mediated pharmacokinetics of infliximab. This model could be useful to improve model-based therapeutic drug monitoring of infliximab in IBD patients.

Feasibility and safety of tailored dosing schedule for eculizumab based on therapeutic drug monitoring: Lessons from a prospective multicentric study.

AIMS: Eculizumab is an anti-C5 monoclonal antibody approved for rare diseases including atypical haemolytic-uraemic syndrome. The maintenance phase dosing regimen is identical for all adult patients: 1200 mg every 2 weeks. Recent studies reported an overexposure in many patients when considering a target trough concentration range of 50-100 mg/L. The aim of the present work was to validate the feasibility of therapeutic drug monitoring of eculizumab in atypical haemolytic-uraemic syndrome patients. METHODS: We performed a 2-step prospective multicentre study. In the first phase, we developed a pharmacokinetic population model using data from 40 patients and identified patients for whom a 1-week lengthening of interval between infusions would lead to a trough concentration above 100 mg/L. In the second phase, selected patients were allocated a 1-week extension and eculizumab trough concentrations were monitored. RESULTS: The model confirmed the previously reported influence of bodyweight on elimination clearance and predicted that 36 (90%) patients would be eligible for interval extension. In the second phase of the study, a 1-week lengthening of interval between infusions was performed in 15 patients whose trough concentration at the next visit was predicted with a Bayesian model to be above 100 mg/L. After interval extension, 10 patients (67%) presented measured trough concentrations over 100 mg/L. No biological or clinical recurrence of disease was observed, even in the 5 patients with concentrations below 100 mg/L in whom the initial dosing regimen was resumed. CONCLUSION: Safe eculizumab interval adjustment is feasible with a PK monitoring.

A phase I dose-escalation study of oxaliplatin delivered via a laparoscopic approach using pressurised intraperitoneal aerosol chemotherapy for advanced peritoneal metastases of gastrointestinal tract cancers.

OBJECTIVE: The objectives were to define the maximum tolerated dose (MTD), safety profile and pharmacokinetics (PKs) of intraperitoneal oxaliplatin delivered by pressurised intraperitoneal aerosol chemotherapy (PIPAC) in patients with advanced peritoneal carcinomatosis from gastrointestinal tract cancers. METHODS: PIPAC was applied every 4-6 weeks, for 5 cycles, in a phase I dose-escalation study using a 3 + 3 design. The first dose level was 90 mg/m2 with planned increases of 50 mg/m2 per level. Platinum concentration was measured in plasma, tissues and intraperitoneal fluid samples. The trial was registered at ClinicalTrials.gov (NCT03294252). RESULTS: Ten patients with 33 PIPAC sessions were included. No dose limiting toxicity (DLT) occurred at 90 mg/m2 and two at 140 mg/m2. The MTD was therefore set at 90 mg/m2. Overall treatment included a median number of three PIPAC sessions (range: 1-5) and secondary complete cytoreductive surgery for two patients. Overall safety showed 67 grade I-II and 11 grade III-IV toxicities, usually haematologic, digestive (nausea/vomiting, abdominal pain), and fatigue. Oxaliplatin concentrations were three- to four-fold higher in tissue in contact with aerosol than in muscle without contact. At 140 mg/m2, the plasma oxaliplatin concentration was high with Cmax and area under the curve (AUC)0-48h of 1035 µg/l and 9028 µg h/L, respectively. CONCLUSIONS: The MTD of oxaliplatin during PIPAC is 90 mg/m2. PK data demonstrate a high tumour concentration and a significant systemic absorption.

[EGFR molecular characterization in non-small cell bronchic cancer: comparative prospective study by NGS and Idylla platform technologies]. / Caractérisation moléculaire de l'EGFR dans les cancers bronchiques non à petites cellules : étude prospective comparative des technologies NGS et automate Idylla.

INTRODUCTION: Detection of genetic alterations in the EGFR tyrosine kinase domain is a major concern in the management of non-small cell lung cancer because it conditions access to tyrosine kinase inhibitors. In practice, it is possible to characterize only well-documented mutations or to sequence all relevant EGFR exons and also other targets of theranostic interest. This prospective study compares the targeted EGFR characterization on Idylla platform (Biocartis) and a more extensive one by next generation sequencing using Ion Torrent technology. MATERIAL AND METHODS: A total of 100 formalin-fixed paraffin-embedded tumour samples were tested simultaneously by both techniques under the conditions recommended by the suppliers. The comparison covered all technical and practical aspects of the laboratory. RESULTS: At least one EGFR mutation of interest for tyrosine kinase inhibitors for 9 and 7 samples was detected respectively by sequencing and by the Idylla system. For three samples, EGFR sensitive mutations to tyrosine kinase inhibitors were detected only by next-generation sequencing. In addition, for 37 samples, mutations of clinical interest outside EGFR were characterized by sequencing and communicated to the prescriber. CONCLUSION: Idylla technology allows the rapid characterization of a majority of EGFR variants. The result can be optimized by careful analysis of the amplification curves with the Idylla Explore tool or by increasing the amount of initial material. A complementary new generation sequencing analysis for non-contributory results by Idylla should also be recommended.

Efficacy and Safety of Anti-D Immunoglobulins versus Intravenous Immunoglobulins for Immune Thrombocytopenia in Children: Systematic Review and Meta-analysis of Randomized Controlled Trials.

OBJECTIVES: To compare the efficacy and safety of intravenous immunoglobulins (IVIG) and anti-D immunoglobulin (anti-D) in pediatric immune thrombocytopenia (ITP). STUDY DESIGN: We conducted a systematic review and meta-analysis following PRISMA guidelines, including all randomized controlled trials that have assessed the efficacy and safety of anti-D and IVIG in children with ITP. We searched Medline, Embase, and Cochrane databases. Primary outcomes were the proportion of children achieving platelet count responses as defined in each study and bleeding response. Other safety outcomes included infusion reactions and hemolysis. RESULTS: Eleven studies with 558 children were included. Anti-D was significantly inferior to IVIG at increasing platelet counts, both for thresholds of >20 × 109/L at 24-72 hours (response rate ratio for anti-D vs IVIG: 0.85, 95% CI 0.78-0.94) and >50 × 109/L at 24-72 hours (response rate ratio for anti-D vs IVIG: 0.75, 95% CI 0.61-0.92). Bleeding response was assessed in 4 studies, but some heterogeneity in reporting leads to unclear conclusion. General symptoms after anti-D infusion were less frequent than after IVIG (Peto OR 0.39, 95% CI 0.25-0.62). Hemolysis was more frequent after anti-D. The overall quality of the studies was low. CONCLUSIONS: Compared with anti-D, IVIG led to a better response in terms of platelet count and may be preferred as a first-line treatment of ITP in children with acute hemorrhagic symptoms. However, the clinical significance of IVIG superiority on platelet count remains unclear.

Phase I feasibility study for intrathecal administration of trastuzumab in patients with HER2 positive breast carcinomatous meningitis.

PURPOSE: Leptomeningeal carcinomatosis (MC) is commonly associated with HER2-positive breast cancer (HER2-BC), with a poor prognosis and no standardised treatment. We conducted a phase I dose-escalation study of intrathecal (IT) administration of trastuzumab in HER2-BC patients with MC to determine the maximum tolerated dose (MTD), which was based on both the achievement of a trastuzumab intra-cerebrospinal fluid concentration close to a conventional therapeutic plasma concentration (30 mg/L) and/or dose-limiting toxicity (DLT). METHODS: The protocol planned IT administration of trastuzumab (30 mg, 60 mg, 100 mg or 150 mg dose levels) once a week, over the course of at least 4 weeks. Sixteen patients with MC from HER2-BC received IT trastuzumab. Intra-cerebrospinal fluid samples were obtained before each injection for pharmacokinetics. RESULTS: We did not observe DLT of IT trastuzumab. Eleven patients had no toxicity attributed to IT trastuzumab. For 60 mg or higher dose levels, minor toxicities attributed to IT trastuzumab included headache (2 patients), nausea (2 patients), vomiting (1 patient), cervical pain (1 patient) and peripheral neuropathy (1 patient). Two patients experienced immediate toxicity including headache or vomiting. The mean residual intra-cerebrospinal fluid concentration of trastuzumab was 27.9 mg/L for the 150 mg dose level. Three patients achieved a clinical response, seven patients had stable disease and four patients had progressive disease. CONCLUSIONS: The MTD and recommended phase II weekly dose of IT trastuzumab in patients with HER2-BC and MC is 150 mg. A phase II trial using this dose regimen in MC from HER2-BC is ongoing. REGISTRATION IDENTIFICATION: ClinicalTrials.gov Identifier: NCT01373710 (https://clinicaltrials.gov/ct2/show/NCT01373710?term=trastuzumab+intrathecal&rank=1).

Development and validation of an ELISA to study panitumumab pharmacokinetics.

AIM: Panitumumab is a monoclonal antibody directed against EGFR that is approved for the treatment of metastatic colorectal cancer. To investigate its pharmacokinetics and concentration-response relationship, a validated assay is required. RESULTS: An ELISA assay was developed and validated according to international recommendations. Six calibrators (ranging from 0.1 to 20 mg/l) plus one anchor point (50 mg/l) and three quality controls (0.45, 2 and 8 mg/l) were defined. The limit of detection, lower limit of quantification and upper limit of quantification were 0.033, 0.112 and 10 mg/l, respectively. CONCLUSION: This method is validated and can be used to study pharmacokinetics of panitumumab or to perform therapeutic drug monitoring.

Model-Based Therapeutic Drug Monitoring of Infliximab Using a Single Serum Trough Concentration.

BACKGROUND AND OBJECTIVES: The pharmacokinetics of infliximab are highly variable and influence clinical response in chronic inflammatory diseases. The goal of this study was to build a Bayesian model allowing predictions of upcoming infliximab concentrations and dosing regimen adjustment, using only one concentration measurement and information regarding the last infliximab infusion. METHODS: This retrospective study was based on data from 218 patients treated with infliximab in Tours University Hospital who were randomly assigned to learning (two-thirds) or validation (one-third) data subsets. One-compartment pharmacokinetic and time since last dose (TLD) models were built and compared using learning and validation subsets. From these models, Bayesian pharmacokinetic and TLD models using one concentration measurement (1C-PK and 1C-TLD) were designed. The predictive performances of the 1C-TLD model were tested on two external validation cohorts. RESULTS: Pharmacokinetic and TLD models described the data satisfactorily and provided accurate parameter estimations. Comparable predictions of infliximab concentrations were obtained from pharmacokinetic versus TLD models, as well as from Bayesian 1C-PK versus 1C-TLD models. The 1C-TLD model showed satisfactory prediction of future infliximab concentrations and provided satisfactory predictions of infliximab steady-state concentration for up to three upcoming visits after a blood sample. CONCLUSIONS: Accurate individual concentration predictions can be obtained using a single infliximab concentration measurement and information regarding only the last infusion. The 1C-TLD model may help to optimize the dosing regimen of infliximab in routine therapeutic drug monitoring.

Development and validation of an enzyme-linked immunosorbent assay to measure free eculizumab concentration in serum.

AIM: Eculizumab is a monoclonal antibody toward C5 fraction of the complement system. It is approved to treat paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome. To perform pharmacokinetic studies and therapeutic drug monitoring, a validated assay is required. MATERIALS & METHODS: An indirect ELISA with recombinant human C5 sensitized microtiter plates were developed. RESULTS: The assay allows the measurement of free eculizumab concentration in human serum. The LOD, LLOQ and ULOQ were 0.091, 0.25 and 82.35 mg/l, respectively. The assay meets EMA and US FDA guidelines criteria for the validation of a ligand-binding assay. CONCLUSION: This method is validated and can be used in PK and PK-PD studies as well as to perform therapeutic drug monitoring of free eculizumab.

Therapeutic Drug Monitoring of Biopharmaceuticals May Benefit From Pharmacokinetic and Pharmacokinetic-Pharmacodynamic Modeling.

Biopharmaceuticals, especially monoclonal antibodies, have been increasingly used to treat several chronic inflammatory diseases. Due to the complexity of their pharmacokinetics and concentration-effect relationship, therapeutic drug monitoring (TDM) has been used to optimize their dosing regimen. Up to date, several decisional algorithms have been developed to provide tools for monoclonal antibodies' therapeutic drug monitoring. However, these algorithms are unable to determine the individual optimal dosing scheme. The aim of this article is to deal with population pharmacokinetic (PK) and pharmacokinetic-pharmacodynamic (PK-PD) modeling. Allowing the quantification of the variability of the dose-concentration-response relationship, population pharmacokinetic-pharmacodynamic modeling may be a valuable tool to determine the optimal dosing scheme. Based on population modeling, Bayesian estimators may be developed to optimize dosing schemes for each patient using limited sampling strategies. These estimators may allow accurate dosing adjustment for each patient individually.

Crucial Role for Immune Complexes but Not FcRn in Immunization against Anti-TNF-α Antibodies after a Single Injection in Mice.

The immunogenicity of infliximab and adalimumab is a major concern because patients may develop Abs also called antidrug Abs (ADA), directed against these anti-TNF-α Abs after just a few weeks of treatment. These ADAs can lead to a decrease in biologic concentration, which is associated with lower treatment efficacy. Our aim was to study the involvement of immune complexes and neonatal Fc receptor (FcRn) in the emergence of ADAs in the case of anti-TNF-α Abs. Wild type and FcRn knockout mice were injected once with either infliximab or adalimumab, alone or preincubated with TNF-α. Adalimumab cross-reacts with murine TNF-α whereas infliximab is species specific. When injected alone, only adalimumab elicited a humoral response. By preforming immune complexes with TNF-α, an anti-infliximab response was elicited. Surprisingly, both wild type and FcRn knockout mice were able to mount an immune response against anti-TNF-α Abs, suggesting that immune complexes are a major determinant of this immunization.

Rationale for Therapeutic Drug Monitoring of Biopharmaceuticals in Inflammatory Diseases.

Biopharmaceuticals bring together a number of specific characteristics as compared with other drugs. However, as it is done for most drugs, an individual adjustment of their dose may be necessary. Similar to "chemical" drugs, biopharmaceuticals used in immunoinflammatory diseases have a rather narrow therapeutic range, lack good early clinical or biological marker of response, have variable pharmacokinetics, and their serum concentrations are most often related with response. Monoclonal antibodies have additional specific sources of pharmacokinetic variability. Low concentrations may increase the risks of immunization, plasmapheresis may increase their elimination, and subcutaneous formulations may be associated with decreased adherence. For all these reasons, pharmacokinetic therapeutic drug monitoring may be useful. However, few randomized controlled therapeutic drug monitoring studies have been published. For monoclonal antibodies, a precise definition of the therapeutic concentrations is challenging because of the interindividual variability in their concentration-effect relationship.

Antigenic burden and serum IgG concentrations influence rituximab pharmacokinetics in rheumatoid arthritis patients.

AIMS: Rituximab is a monoclonal antibody directed against CD20, which is approved in rheumatoid arthritis (RA). This study aimed at assessing the influence of CD19+ cell counts as target-antigen amount, and of immunoglobulin G (IgG) serum concentrations on rituximab pharmacokinetics in RA patients. METHODS: In a cohort of 64 RA patients who had received repetitive courses of rituximab, the influence of CD19+ cell count, IgG serum concentration, body surface area, sex and disease activity score in 28 joints on rituximab pharmacokinetic parameters was assessed using a population pharmacokinetic analysis. RESULTS: A two-compartment model, with first-order distribution and elimination best described the data. The volume of distribution of central compartment and clearance of rituximab were estimated at 4.7 l and 0.56 l day-1 , respectively. Distribution and elimination half-lives were 0.9 days and 17.3 days, respectively. As expected, the central volume of distribution increased with body surface area (P = 0.012) and was higher in male than in female (P = 0.004). We found that the elimination rate constant (k10 ) increased with CD19+ count (P = 0.00022) and IgG concentration (P = 7.4 × 10-8 ), and that k10 decreased with time (P = 0.00015), partly explained by a change in target-antigen amount. CONCLUSIONS: The association between CD19+ count and k10 may be explained by target-mediated drug disposition, while the association between IgG serum concentration and k10 may be explained by a saturation of the neonatal Fc receptor at high IgG concentrations, resulting in decreased recycling of rituximab.