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.

Prospective study to characterize adalimumab exposure in pediatric patients with rheumatic diseases

BACKGROUND

In pediatric rheumatic diseases (PRD), adalimumab is dosed using fixed weight-based bands irrespective of methotrexate co-treatment, disease activity (DA) or other factors that might influence adalimumab pharmacokinetics (PK). In rheumatoid arthritis (RA) adalimumab exposure between 2-8 mg/L is associated with clinical response. PRD data on adalimumab is scarce. Therefore, this study aimed to analyze adalimumab PK and its variability in PRD treated with/without methotrexate.

METHODS

A two-center prospective study in PRD patients aged 2-18 years treated with adalimumab and methotrexate (GA-M) or adalimumab alone (GA) for ≥ 12 weeks was performed. Adalimumab concentrations were collected 1-9 (maximum concentration; Cmax), and 10-14 days (minimum concentration; Cmin) during ≥ 12 weeks following adalimumab start. Concentrations were analyzed with enzyme-linked immunosorbent assay (lower limit of quantification: 0.5 mg/L). Log-normalized Cmin were compared between GA-M and GA using a standard t-test.

RESULTS

Twenty-eight patients (14 per group), diagnosed with juvenile idiopathic arthritis (71.4%), non-infectious uveitis (25%) or chronic recurrent multifocal osteomyelitis (3.6%) completed the study. GA-M included more females (71.4%; GA 35.7%, p = 0.13). At first study visit, children in GA-M had a slightly longer exposure to adalimumab (17.8 months [IQR 9.6, 21.6]) compared to GA (15.8 months [IQR 8.5, 30.8], p = 0.8). Adalimumab dosing was similar between both groups (median dose 40 mg every 14 days) and observed DA was low. Children in GA-M had a 27% higher median overall exposure compared to GA, although median Cmin adalimumab values were statistically not different (p = 0.3). Cmin values ≥ 8 mg/L (upper limit RA) were more frequently observed in GA-M versus GA (79% versus 64%). Overall, a wide range of Cmin values was observed in PRD (0.5 to 26 mg/L).

CONCLUSION

This study revealed a high heterogeneity in adalimumab exposure in PRD. Adalimumab exposure tended to be higher with methotrexate co-treatment compared to adalimumab monotherapy although differences were not statistically significant. Most children showed adalimumab exposure exceeding those reported for RA with clinical response, particularly with methotrexate co-treatment. This highlights the need of further investigations to establish model-based personalized treatment strategies in PRD to avoid under- and overexposure.

TRIAL REGISTRATION

NCT04042792 , registered 02.08.2019.

Confounding mitigation for the exposure-response relationship of bevacizumab in colorectal cancer patients

AIMS

The exposure-response relationship of bevacizumab may be confounded by various factors, including baseline characteristics, time-dependent target engagement and recursive relationships between exposure and response, requiring effective mitigation. This study aimed to investigate the exposure-response relationships of bevacizumab in metastatic colorectal cancer (mCRC) patients while mitigating potential biases.

METHODS

Bevacizumab pharmacokinetics was described using target-mediated drug disposition modelling. Relationships between target kinetics, progression-free (PFS) and overall (OS) survivals were assessed using joint pharmacokinetic and parametric hazard function models. Both prognostic-driven and response-driven potential biases were mitigated. These models evaluated the impact of increased antigen target levels, clearance and intensified dosing regimen on survival.

RESULTS

Estimated target-mediated pharmacokinetic parameters in 130 assessed patients were baseline target levels (R0  = 8.4 nM), steady-state dissociation constant (KSS  = 10 nM) and antibody-target complexes elimination constant (kint  = 0.52 day-1 ). The distribution of R0 was significantly associated with increased baseline concentrations of carcinoembryonic antigen, circulating vascular endothelial growth factor and the presence of extrahepatic metastases. Unbound target levels (R) significantly influenced both progression and death hazard functions. Increasing baseline target levels and/or clearance values led to decreased bevacizumab unbound concentrations, increased R levels and shortened PFS and OS, while increasing bevacizumab dose led to decreased R and longer survival.

CONCLUSION

This study is the first to demonstrate the relationship between bevacizumab concentrations, target involvement and clinical efficacy by effectively mitigating potential sources of bias. Most of the target amount may be tumoural in mCRC. Future studies should provide a more in-depth description of this relationship.

Prediction of the Clinical Course of Immune Thrombocytopenia in Children by Platelet Kinetics

Childhood immune thrombocytopenia (ITP) is a rare autoimmune disorder characterized by isolated thrombocytopenia. Prolonged ITP (persistent and chronic) leads to a reduced quality of life for children in many domains. To provide optimal support for children, with ITP, it is important to be able to predict those who will develop prolonged ITP. This study aimed to develop a mathematical model based on platelet recovery that allows the early prediction of prolonged ITP. In this retrospective study, we used platelet counts from the 6 months following the diagnosis of ITP to model the kinetics of change in platelet count using a pharmacokinetic-pharmacodynamic model. In a learning set (n = 103), platelet counts were satisfactorily described by our kinetic model. The Kheal parameter, which describes spontaneous platelet recovery, allowed a distinction between acute and prolonged ITP with an area under the curve (AUC) of 0.74. In a validation set (n = 58), spontaneous platelet recovery was robustly predicted using platelet counts from 15 (AUC = 0.76) or 30 (AUC = 0.82) days after ITP diagnosis. In our model, platelet recovery quantified using the kheal parameter allowed prediction of the clinical course of ITP. Future prospective studies are needed to improve the predictivity of this model, in particular, by combining it with the predictive scores previously reported in the literature.

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.

Translation of Monoclonal Antibodies Pharmacokinetics from Animal to Human Using Physiologically Based Modeling in Open Systems Pharmacology (OSP) Suite: A Retrospective Analysis of Bevacizumab

Interspecies translation of monoclonal antibodies (mAbs) pharmacokinetics (PK) in presence of target-mediated drug disposition (TMDD) is particularly challenging. Incorporation of TMDD in physiologically based PK (PBPK) modeling is recent and needs to be consolidated and generalized to provide better prediction of TMDD regarding inter-species translation during preclinical and clinical development steps of mAbs. The objective of this study was to develop a generic PBPK translational approach for mAbs using the open-source software (PK-Sim® and Mobi®). The translation of bevacizumab based on data in non-human primates (NHP), healthy volunteers (HV), and cancer patients was used as a case example for model demonstration purpose. A PBPK model for bevacizumab concentration-time data was developed using data from literature and the Open Systems Pharmacology (OSP) Suite version 10. PK-sim® was used to build the linear part of bevacizumab PK (mainly FcRn-mediated), whereas MoBi® was used to develop the target-mediated part. The model was first developed for NHP and used for a priori PK prediction in HV. Then, the refined model obtained in HV was used for a priori prediction in cancer patients. A priori predictions were within 2-fold prediction error (predicted/observed) for both area under the concentration-time curve (AUC) and maximum concentration (Cmax) and all the predicted concentrations were within 2-fold average fold error (AFE) and average absolute fold error (AAFE). Sensitivity analysis showed that FcRn-mediated distribution and elimination processes must be accounted for at all mAb concentration levels, whereas the lower the mAb concentration, the more significant the target-mediated elimination. This project is the first step to generalize the full PBPK translational approach in Model-Informed Drug Development (MIDD) of mAbs using OSP Suite.

Response to Biologic Drugs in Patients With Rheumatoid Arthritis and Antidrug Antibodies

Importance

There are conflicting data on the association of antidrug antibodies with response to biologic disease-modifying antirheumatic drugs (bDMARDs) in rheumatoid arthritis (RA).

Objective

To analyze the association of antidrug antibodies with response to treatment for RA.

Design, Setting, and Participants

This cohort study analyzed data from the ABI-RA (Anti-Biopharmaceutical Immunization: Prediction and Analysis of Clinical Relevance to Minimize the Risk of Immunization in Rheumatoid Arthritis Patients) multicentric, open, prospective study of patients with RA from 27 recruiting centers in 4 European countries (France, Italy, the Netherlands, and the UK). Eligible patients were 18 years or older, had RA diagnosis, and were initiating a new bDMARD. Recruitment spanned from March 3, 2014, to June 21, 2016. The study was completed in June 2018, and data were analyzed in June 2022.

Exposures

Patients were treated with a new bDMARD: adalimumab, infliximab (grouped as anti-tumor necrosis factor [TNF] monoclonal antibodies [mAbs]), etanercept, tocilizumab, and rituximab according to the choice of the treating physician.

Main Outcomes and Measures

The primary outcome was the association of antidrug antibody positivity with EULAR (European Alliance of Associations for Rheumatology; formerly, European League Against Rheumatism) response to treatment at month 12 assessed through univariate logistic regression. The secondary end points were the EULAR response at month 6 and at visits from month 6 to months 15 to 18 using generalized estimating equation models. Detection of antidrug antibody serum levels was performed at months 1, 3, 6, 12, and 15 to 18 using electrochemiluminescence (Meso Scale Discovery) and drug concentration for anti-TNF mAbs, and etanercept in the serum was measured using enzyme-linked immunosorbent assay.

Results

Of the 254 patients recruited, 230 (mean [SD] age, 54.3 [13.7] years; 177 females [77.0%]) were analyzed. At month 12, antidrug antibody positivity was 38.2% in patients who were treated with anti-TNF mAbs, 6.1% with etanercept, 50.0% with rituximab, and 20.0% with tocilizumab. There was an inverse association between antidrug antibody positivity (odds ratio [OR], 0.19; 95% CI, 0.09-0.38; P < .001) directed against all biologic drugs and EULAR response at month 12. Analyzing all the visits starting at month 6 using generalized estimating equation models confirmed the inverse association between antidrug antibody positivity and EULAR response (OR, 0.35; 95% CI, 0.18-0.65; P < .001). A similar association was found for tocilizumab alone (OR, 0.18; 95% CI, 0.04-0.83; P = .03). In the multivariable analysis, antidrug antibodies, body mass index, and rheumatoid factor were independently inversely associated with response to treatment. There was a significantly higher drug concentration of anti-TNF mAbs in patients with antidrug antibody-negative vs antidrug antibody-positive status (mean difference, -9.6 [95% CI, -12.4 to -6.9] mg/L; P < 001). Drug concentrations of etanercept (mean difference, 0.70 [95% CI, 0.2-1.2] mg/L; P = .005) and adalimumab (mean difference, 1.8 [95% CI, 0.4-3.2] mg/L; P = .01) were lower in nonresponders vs responders. Methotrexate comedication at baseline was inversely associated with antidrug antibodies (OR, 0.50; 95% CI, 0.25-1.00; P = .05).

Conclusions and Relevance

Results of this prospective cohort study suggest an association between antidrug antibodies and nonresponse to bDMARDs in patients with RA. Monitoring antidrug antibodies could be considered in the treatment of these patients, particularly nonresponders to biologic RA drugs.

Randomized Phase III Trial Evaluating Subcutaneous Rituximab for the First-Line Treatment of Low-Tumor Burden Follicular Lymphoma: Results of a LYSA Study

PURPOSE

Rituximab improves progression-free survival (PFS) and time to next treatment (TTNT) when compared with the watch and wait strategy for patients with low-tumor burden follicular lymphoma (FL). Prolonged rituximab maintenance did not prolong TTNT, whereas it raises concerns about resources use and patient adhesion. Our aim was then to investigate the use of short rituximab maintenance using the subcutaneous (SC) route in patients with low-tumor burden FL.

METHODS

Patients with histologically confirmed CD20⁺ low-tumor burden FL were randomly assigned to receive either rituximab, 375 mg/m² once daily on D1, D8, D15, and D22, intravenous route (IV, control arm), or rituximab, 375 mg/m², on day 1 (D1), IV followed by rituximab 1,400 mg total dose, SC once daily on D8, D15, and D22, with maintenance at months 3 (M3), M5, M7, and M9 (experimental arm). The primary end point was PFS. Secondary end points included safety, overall response rates, TTNT, and overall survival (OS).

RESULTS

Two hundred two patients with low-tumor burden FL were randomly assigned to the experimental (n = 100) or control arm (n = 102). The primary end point was met: the 4-year PFS was 58.1% (95% CI, 47.5 to 67.4) and 41.2% (95% CI, 30.6 to 51.6) in experimental and control arms, respectively (hazard ratio, 0.585 [0.393 to 0.871]; P = .0076). Complete response (CR) rates were 59.0% (95% CI, 48.7 to 68.7) in the experimental arm and 36.3% (95% CI, 27.0 to 46.4) in the control arm (P = .001). TTNT and OS were not significantly different. CR was associated with longer PFS and TTNT. High rituximab exposure during the first three months was independently associated with higher CR, PFS, and TTNT.

CONCLUSION

SC rituximab improves PFS for patients with low-tumor burden FL when used in induction followed by short maintenance. High rituximab exposure during the first 3 months after treatment initiation is, however, the only parameter influencing patient outcomes.

Abstract 1144: A multiplex LC-MS/MS method for assaying mAbs in oncology: Application to the CETUXIMAX GPCO-Unicancer trial on cetuximab pharmacokinetics in head and neck cancer patients

Implementing PK-guided dosing with monoclonal antibodies (mAbs) in oncology has been for long impaired by difficulties in developing appropriate (i.e., time- and cost-effective) bioanalytical methods suitable for routine Therapeutic Drug Monitoring, plus concerns regarding the exact PK/PD relationships of several biologics possibly blurred by the TMDD phenomenon. To help lifting these issues, we have developed and cross-validated a multiplex LC-MS/MS method allowing to assay simultaneously up to 8 mAbs in plasma, including several immune checkpoint inhibitors (i.e., atezolizumab, bevacizumab, cetuximab, ipilimumab, nivolumab, pembrolizumab, rituximab, trastuzumab). Using a ready-to-use kit (mAbXmise), the method proved to be simple and rapid - covering a concentration range of 2-100 µg/ml, in line with plasma concentrations usually expected with mAbs. Inter and intra-assay precision were both &lt;15% and accuracy was comprised between 90.1 and 111.1%, thus meeting the requirements of current EMA guidelines for validating bioanalytical methods. Cross-validation using reference LC-MS/MS or ELISA methods was performed on 7 mAbs (excluding atezolizumab since no reference method was available) with a satisfactory mean absolute bias of 10.6% (3.0-19.9%). This LC-MS/MS method was next used as part of the Cetuximax trial (NCT-04218136), an open, non-randomized, single arm, multicentric study aiming at determining the PK/PD relationships of Cetuximab in Head-and-Neck cancer patients with monitoring of both Cmax and Cmin levels. Patients are all treated with the 250 mg/m² QW schedule. Previous works have suggested that Cetuximab trough levels &lt; 34 µg/ml were associated with higher risk for treatment failure in Head-and-Neck patients. Patients were repeatedly sampled in a longitudinal fashion at their Cmax plus trough levels and individual PK parameters were derived using a pop-PK approach. Preliminary results on 90 samples collected from the first 25 out of the 110 patients to be included have confirmed the marked inter-individual variability in Cetuximab exposure (i.e., &gt;56% on trough levels and &gt;55% on Cmax values). Mean Cetuximab trough level was 54 ± 30 µg/ml (range: 12-104 µg/ml) and mean Cmax value was 211 ± 116 µg/ml (range: 75-418 µg/ml), with several individuals (8 out of 25, i.e., 32%) showing plasma exposure below the expected trough levels associated with efficacy. Although preliminary, our data confirm that PK variability is massive with mAbs. This observation suggests that Therapeutic Drug Monitoring, using appropriate LC-MS/MS method, could help appraising interpatient variability at bedside and detecting individuals with exposure levels out of the range usually observed.

Citation Format: Clemence Marin, Nihel Khoudour, Aurélien Millet, Dorothée Lebert, Pauline Bros, Fabienne Thomas, David Ternant, Jerôme Guitton, Mourad Hamimed, Benoit Blanchet, Sebastien Salas, Joseph Ciccolini. A multiplex LC-MS/MS method for assaying mAbs in oncology: Application to the CETUXIMAX GPCO-Unicancer trial on cetuximab pharmacokinetics in head and neck cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1144.

Adjunction of a fish oil emulsion to cytarabine and daunorubicin induction chemotherapy in high-risk AML

The treatment of acute myeloid leukemia (AML) with unfavorable cytogenetics treatment remains a challenge. We previously established that ex vivo exposure of AML blasts to eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), or fish oil emulsion (FO) induces Nrf2 pathway activation, metabolic switch, and cell death. The FILO group launched a pilot clinical study to evaluate the feasibility, safety, and efficacy of the adjunction of a commercial FO emulsion to 3 + 7 in untreated AML with unfavorable cytogenetics. The primary objective was complete response (CR). Thirty patients were included. FO administration raised the plasma levels of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids (p < 0.001). The pharmacokinetics of cytarabine and daunorubicin were unaffected. A historical comparison to the LAM2001 trial (Lioure et al. Blood 2012) found a higher frequency of grade 3 serious adverse events, with no drug-related unexpected toxicity. The CR rate was 77%, and the partial response (PR) 10%, not significantly superior to that of the previous study (CR 72%, PR 1%). RT-qPCR analysis of Nrf2 target genes and antioxidant enzymes did not show a significant in vivo response. Overall, FO emulsion adjunction to 3 + 7 is feasible. An improvement in CR was not shown in this cohort of high-risk patients. The present data does not support the use of FO in adjunction with 3 + 7 in high-risk AML patients.

ClinicalTrials.gov identifier: NCT01999413.

Curcumin and NCLX inhibitors share anti-tumoral mechanisms in microsatellite-instability-driven colorectal cancer

BACKGROUND AND AIMS

Recent evidences highlight a role of the mitochondria calcium homeostasis in the development of colorectal cancer (CRC). To overcome treatment resistance, we aimed to evaluate the role of the mitochondrial sodium-calcium-lithium exchanger (NCLX) and its targeting in CRC. We also identified curcumin as a new inhibitor of NCLX.

METHODS

We examined whether curcumin and pharmacological compounds induced the inhibition of NCLX-mediated mitochondrial calcium (mtCa2+) extrusion, the role of redox metabolism in this process. We evaluated their anti-tumorigenic activity in vitro and in a xenograft mouse model. We analyzed NCLX expression and associations with survival in The Cancer Genome Atlas (TCGA) dataset and in tissue microarrays from 381 patients with microsatellite instability (MSI)-driven CRC.

RESULTS

In vitro, curcumin exerted strong anti-tumoral activity through its action on NCLX with mtCa2+ and reactive oxygen species overload associated with a mitochondrial membrane depolarization, leading to reduced ATP production and apoptosis. NCLX inhibition with pharmacological and molecular approaches reproduced the effects of curcumin. NCLX inhibitors decreased CRC tumor growth in vivo. Both transcriptomic analysis of TCGA dataset and immunohistochemical analysis of tissue microarrays demonstrated that higher NCLX expression was associated with MSI status, and for the first time, NCLX expression was significantly associated with recurrence-free survival.

CONCLUSIONS

Our findings highlight a novel anti-tumoral mechanism of curcumin through its action on NCLX and mitochondria calcium overload that could benefit for therapeutic schedule of patients with MSI CRC.

Angiogenic factors could help us to define patients obtaining complete response with undetectable minimal residual disease in untreated CLL patients treated by FCR: results from the CLL2010FMP, a FILO study

Angiogenesis is in a constant balance between pro and anti-angiogenic factors. Neoangiogenesis, implicated in metastatic spreading is characterized in solid cancers, but fairly new in chronic lymphocytic leukemia (CLL). We hypothesize that secretion of angiogenic factors could be correlated to the pathogenesis of CLL, and therefore predict the outcome of patients. We investigated concentrations of 22 cytokines and chemokines in 137 non-del 17p B-CLL patients, treated with a fludarabine-cyclophosphamide-rituximab (FCR)-based regimen. We constructed a biomarker index defining different risk groups based on lymphocyte count, the intensity of CD20 antigen on CD19⁺ cells, Ang-2, and PDGF-BB plasma concentrations at diagnosis. Four groups were defined, exhibiting specific molecular signatures and correlated with progression-free survival of patients. Our results suggest that we can determine at diagnosis of non-del 17p B-CLL patients, those with a very high probability of progression-free survival, independently of IGVH mutational status and residual disease at the end of treatment.

The Influence of Underlying Disease on Rituximab Pharmacokinetics May be Explained by Target-Mediated Drug Disposition

BACKGROUND AND OBJECTIVES

Rituximab is an anti-CD20 monoclonal antibody approved in several diseases, including chronic lymphocytic leukemia (CLL), diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), rheumatoid arthritis (RA), and anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV). The influence of underlying disease on rituximab pharmacokinetics has never been investigated for several cancer and non-cancer diseases simultaneously. This study aimed at assessing this influence using an integrated semi-mechanistic model accounting for target-mediated elimination of rituximab.

METHODS

Rituximab concentration-time data from five studies previously published in patients with CLL, DLBCL, FL, RA, and AAV were described using a two-compartment model with irreversible binding of rituximab to its target antigen. Both underlying disease and target antigen measurements were assessed as covariates.

RESULTS

Central volume of distribution was [95% confidence interval] 1.7-fold [1.6-1.9] higher in DLBCL than in RA, FL, and CLL, and it was 1.8-fold [1.6-2.1] higher in RA, FL, and CLL than in AAV. First-order elimination rate constants were 1.8-fold [1.7-2.0] and 1.3-fold [1.2-1.5] higher in RA, DLBCL, and FL than in CLL and AAV, respectively. Baseline latent antigen level (L₀) was 54-fold [30-94], 20-fold [11-36], and 29-fold [14-64] higher in CLL, DLBCL, and FL, respectively, than in RA and AAV. In lymphoma, L₀ increased with baseline total metabolic tumor volume (p = 6.10^-7). In CLL, the second-order target-mediated elimination rate constant (k_deg) increased with baseline CD20 count on circulating B cells (CD20_cir, p = 0.0081).

CONCLUSIONS

Our results show for the first time that rituximab pharmacokinetics is strongly influenced by underlying disease and disease activity. Notably, neoplasms are associated with higher antigen amounts that result in decreased exposure to rituximab compared to inflammatory diseases. Our model might be used to estimate unbound target amounts in upcoming studies.

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 (R^C₀ = 3.3 nM and R^P₀ = 0.46 nM), steady-stated dissociation rates (K^C_SS = 15.4 nM and K^P_SS = 0.49 nM), and first-order elimination rates of complexes (k^C_int = 0.17 day⁻¹ and k^P_int = 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.

Relationship Between Antithymocyte Globulin Concentrations and Lymphocyte Sub-Populations in Kidney Transplant Patients

BACKGROUND

Rabbit antithymocyte globulins (rATGs) are polyclonal antibodies used to prevent acute cellular rejection in kidney transplantation. Their dosing remains largely empirical and the question of an individualized dose is still unresolved.

METHODS

Data from a prospective study in 17 kidney transplant patients were used to develop a model describing the dose-concentration-response relationship of rATG with T-lymphocyte subpopulation counts over time. The model was validated using an independent cohort of kidney transplant patients treated by rATG in the same center.

RESULTS

Pharmacokinetics of rATG was described using a two-compartment model integrating a third compartment and a target-mediated elimination for active rATG. The kinetics of CD3⁺, CD4⁺, CD8⁺, and CD3^-CD56⁺ cell counts over time were described by a pharmacokinetic-pharmacodynamic model with transit compartments, integrating both CD3^-CD56⁺-independent and CD3^-CD56⁺-dependent rATG-mediated lymphocyte depletion, and a positive feedback. Elimination of rATG was influenced by age and body surface area, while its distribution was also influenced by body surface area. CD3⁺ proliferation rate decreased with age and CD3^-CD56⁺-mediated elimination was influenced by the V158F-FCGR3A polymorphism. Binary efficacy and tolerance endpoints were defined as a CD3⁺ count < 20 mm^-3 for at least 7 days and a CD4⁺ count > 200 mm^-3 at 1 year, respectively. Simulations showed that increasing or decreasing the standard 6-mg/kg dose will impact both tolerance and efficacy, while a dose decrease may be beneficial in elderly patients.

CONCLUSIONS

Our results can be used to design prospective clinical trials testing dose individualization based on patients' characteristics.

CLINICAL TRIAL REGISTRATION

Eudract No. 2009-012673-35.

Synthetic alkyl-ether-lipid promotes TRPV2 channel trafficking trough PI3K/Akt-girdin axis in cancer cells and increases mammary tumour volume

The Transient Receptor Potential Vanilloid type 2 (TRPV2) channel is highly selective for Ca2+ and can be activated by lipids, such as LysoPhosphatidylCholine (LPC). LPC analogues, such as the synthetic alkyl-ether-lipid edelfosine or the endogenous alkyl-ether-lipid Platelet Activating Factor (PAF), modulates ion channels in cancer cells. This opens the way to develop alkyl-ether-lipids for the modulation of TRPV2 in cancer. Here, we investigated the role of 2-Acetamido-2-Deoxy-l-O-Hexadecyl-rac-Glycero-3-PhosphatidylCholine (AD-HGPC), a new alkyl-ether-lipid (LPC analogue), on TRPV2 trafficking and its impact on Ca2+ -dependent cell migration. The effect of AD-HGPC on the TRPV2 channel and tumour process was further investigated using calcium imaging and an in vivo mouse model. Using molecular and pharmacological approaches, we dissected the mechanism implicated in alkyl-ether-lipids sensitive TRPV2 trafficking. We found that TRPV2 promotes constitutive Ca2+ entry, leading to migration of highly metastatic breast cancer cell lines through the PI3K/Akt-Girdin axis. AD-HGPC addresses the functional TRPV2 channel in the plasma membrane through Golgi stimulation and PI3K/Akt/Rac-dependent cytoskeletal reorganization, leading to constitutive Ca2+ entry and breast cancer cell migration (without affecting the development of metastasis), in a mouse model. We describe, for the first time, the biological role of a new alkyl-ether-lipid on TRPV2 channel trafficking in breast cancer cells and highlight the potential modulation of TRPV2 by alkyl-ether-lipids as a novel avenue for research in the treatment of metastatic cancer.

Association of IgG1 Antibody Clearance with FcγRIIA Polymorphism and Platelet Count in Infliximab-Treated Patients

The FcγRIIA/CD32A is mainly expressed on platelets, myeloid and several endothelial cells. Its affinity is considered insufficient for allowing significant binding of monomeric IgG, while its H131R polymorphism (histidine > arginine at position 131) influences affinity for multimeric IgG2. Platelet FcγRIIA has been reported to contribute to IgG-containing immune-complexe clearance. Given our finding that platelet FcγRIIA actually binds monomeric IgG, we investigated the role of platelets and FcγRIIA in IgG antibody elimination. We used pharmacokinetics analysis of infliximab (IgG1) in individuals with controlled Crohn’s disease. The influence of platelet count and FcγRIIA polymorphism was quantified by multivariate linear modelling. The infliximab half-life increased with R allele number (13.2, 14.4 and 15.6 days for HH, HR and RR patients, respectively). It decreased with increasing platelet count in R carriers: from ≈20 days (RR) and ≈17 days (HR) at 150 × 10⁹/L, respectively, to ≈13 days (both HR and RR) at 350 × 10⁹/L. Moreover, a flow cytometry assay showed that infliximab and monomeric IgG1 bound efficiently to platelet FcγRIIA H and R allotypes, whereas panitumumab and IgG2 bound poorly to the latter. We propose that infliximab (and presumably any IgG1 antibody) elimination is partly due to an unappreciated mechanism dependent on binding to platelet FcγRIIA, which is probably tuned by its affinity for IgG2.

Non-Linear Rituximab Pharmacokinetics and Complex Relationship between Rituximab Concentrations and Anti-Neutrophil Cytoplasmic Antibodies (ANCA) in ANCA-Associated Vasculitis: The RAVE Trial Revisited

BACKGROUND AND OBJECTIVES

Rituximab is approved in patients with anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and leads to a decrease of ANCA levels. The objectives of this study were to investigate the non-linear pharmacokinetics of rituximab and the relationship between its concentrations and ANCA levels in AAV patients.

METHODS

Ninety-two AAV patients from the RAVE (Rituximab in ANCA-Associated Vasculitis) trial were assessed. Both ANCA anti-myeloperoxidase (MPO-ANCA) and anti-proteinase 3 (PR3-ANCA) levels were used as biomarkers. The pharmacokinetics of rituximab were described using a semi-mechanistic two-compartment model that included a latent target antigen turnover and allowed the estimation of specific target-mediated elimination in addition to its non-specific elimination of rituximab. The effect of rituximab on the ANCA level was described using a semi-mechanistic compartment model with a negative feedback (Friberg) model with no transit compartment. A population modeling approach was used.

RESULTS

Our pharmacokinetic and pharmacokinetic-pharmacodynamic (PK-PD) models satisfactorily described both concentration-time and concentration-effect relationship data. The mean (inter-individual standard deviation) estimated non-specific clearance was 0.15 L/day (0.30%) and the target-mediated elimination rate constant was 2.4 × 10^-5 nmol/day. The elimination half-lives for MPO-ANCA and PR3-ANCA were 24 and 18 days, respectively.

CONCLUSIONS

A non-linear target-mediated elimination of rituximab was detected in AAV patients. Our PK-PD model allowed quantification of the association between rituximab concentrations and ANCA levels. This decrease was deep but delayed, and more sustained in patients with MPO-ANCA than in those with PR3-ANCA. Our results suggest that repeating courses of rituximab might improve the clinical response to rituximab.

A robust enzyme-linked immunosorbent assay to measure serum ramucirumab concentrations

Aim: Ramucirumab, an anti-VEGFR2 monoclonal antibody, has been approved for the treatment of metastatic gastric and colorectal cancer. An assay measuring ramucirumab serum concentrations was needed to investigate its pharmacokinetics and concentration-response relationship. Results: An ELISA was developed and validated according to the international guidelines for ligand-binding assays. Ramucirumab calibration standards ranged from 0.125 to 40 mg/l. Low, middle and high quality controls were spiked at 0.2, 4 and 8 mg/l, respectively. The limits of quantification were established to be 0.125 and 10 mg/l for LLOQ and ULOQ, respectively. No cross-reactivity with anti-VEGF or anti-EGFR was detected. Conclusion: This in-house-developed ELISA is sensitive, accurate, reproducible and suitable for pharmacokinetic studies of ramucirumab.

Antigen Mass May Influence Trastuzumab Concentrations in Cerebrospinal Fluid After Intrathecal Administration

Intravenous administration of monoclonal antibodies leads to low concentrations in the central nervous system, which is a serious concern in neuro-oncology, especially in leptomeningeal carcinomatosis of HER2-overexpressing breast cancer. Case reports of i.t. administrations of trastuzumab have shown promising results in these patients but dosing regimens are empirical in absence of pharmacokinetic (PK) study. With a population PK approach, we described the fate of trastuzumab after i.t. administration in 21 women included in a phase I-II clinical trial. Trastuzumab was administered by i.t. route every week for 8 weeks and both cerebrospinal fluid (CSF) and serum were sampled to measure trough concentrations. Some patients showed noticeable CSF concentration fluctuations predicted using a target-mediated drug disposition. This target was latent and produced with a delayed feedback. Apparent volumes of distribution were close to physiological volumes (V₁  = 3.25 L, V₂  = 0.644 L, for serum and CSF, respectively). Estimated (constant) transfer from serum to CSF was very slow (k₁₂  = 0.264 mg/day) whereas estimated half-life of transfer from CSF to serum was rapid (2.2 days). From the individual parameters of patients, a single i.t. administration of 150 mg of trastuzumab corresponded to median mean residence times of 3.8 days and 15.6 days in CSF and serum, respectively. Survival without neurological relapse was not related to trastuzumab exposure. This study confirms that transfer of trastuzumab from serum to CSF is very limited and that this monoclonal antibody, when administered by i.t. route, is rapidly transferred to the serum.

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.

LDL-cholesterol decrease by anti-PCSK9 monoclonal antibodies: systematic review, meta-analysis and meta-regression of randomized controlled trials

Background

PCSK9 antibodies are novel potent and expansive lipid lowering agents that demonstrated clinical benefit in high risk patients. We hypothesized that optimization of dose and administration schedule, ideally adapted to the target population, could reduce costs while maintaining the clinical benefit.

Objective

To explore the relationship between LDL-Cholesterol (LDL-C) decrease by anti-PCSK9 monoclonal antibodies and several covariates such as drug dose, administration schedule, baseline LDL-C, population and statins.

Methods

We performed systematic review, meta-analysis and meta-regression of randomized controlled trials that compared alirocumab or evolocumab to placebo or no treatment and reported LDL-C decrease, with a minimum follow-up of 12 weeks and with a sample size of 30 patients or more. Electronic searches of MEDLINE, EMBASE, CENTRAL and ClinicalTrials.gov from inception to March 2019. We evaluated the quality of included studies and extracted aggregate data. We used random effect models and multivariate multilevel meta-regression to explore factors influencing LDL-C decrease. All analyses were performed with R.

Results

From 1479 references identified and screened on title/abstract, the full texts of 72 articles were screened. We included 32 studies (31 references.) Anti-PCSK9 mAbs decreased LDL-C by 53%, 95% CI (−56% to −50%), with no significant difference between the two drugs (p=0.07). In univariate meta-regressions, higher baseline LDL-C level, monthly administration, higher percentage of patients with high-dose statins were associated with a lower LDL-C decrease (p&lt;0.0001, p=0.02 and p=0.006 respectively). Drug dose and population did not influence LDL-C decrease in univariate analysis, but with a significant statistical interaction between drug dose and administration schedule (p=0.03). In multivariate meta-regression, LDL-C decrease remained significantly and negatively influenced by baseline LDL-C level

(p&lt;0.0001) and the percentage of patients with high-dose statins (p=0.0009), and was significantly and positively influenced by drug dose (p&lt;0.0001).

Conclusion

Alirocumab and evolocumab showed substantial LDL-C reductions in clinical trials, without significant differences in their biological efficacies. A higher baseline LDL-C, higher intensity of statin co-treatment and a lower dose seemed to negatively influence LDL-C decrease.

Funding Acknowledgement

Type of funding source: None

P2X7 Receptor Promotes Mouse Mammary Cancer Cell Invasiveness and Tumour Progression, and Is a Target for Anticancer Treatment

The P2X7 receptor is an ATP-gated cation channel with a still ambiguous role in cancer progression, proposed to be either pro- or anti-cancerous, depending on the cancer or cell type in the tumour. Its role in mammary cancer progression is not yet defined. Here, we show that P2X7 receptor is functional in highly aggressive mammary cancer cells, and induces a change in cell morphology with fast F-actin reorganization and formation of filopodia, and promotes cancer cell invasiveness through both 2- and 3-dimensional extracellular matrices in vitro. Furthermore, P2X7 receptor sustains Cdc42 activity and the acquisition of a mesenchymal phenotype. In an immunocompetent mouse mammary cancer model, we reveal that the expression of P2X7 receptor in cancer cells, but not in the host mice, promotes tumour growth and metastasis development, which were reduced by treatment with specific P2X7 antagonists. Our results demonstrate that P2X7 receptor drives mammary tumour progression and represents a pertinent target for mammary cancer treatment.

Kinetic modelling of myocardial necrosis biomarkers offers an easier, reliable and more acceptable assessment of infarct size

Infarct size is a major prognostic factor in ST-segment elevation myocardial infarction (STEMI). It is often assessed using repeated blood sampling and the estimation of biomarker area under the concentration versus time curve (AUC) in translational research. We aimed at developing limited sampling strategies (LSS) to accurately estimate biomarker AUC using only a limited number of blood samples in STEMI patients. This retrospective study was carried out on pooled data from five clinical trials of STEMI patients (TIMI blood flow 0/1) studies where repeated blood samples were collected within 72 h after admission to assess creatine kinase (CK), cardiac troponin I (cTnI) and muscle-brain CK (CK-MB). Biomarker kinetics was assessed using previously described biomarker kinetic models. A number of LSS models including combinations of 1 to 3 samples were developed to identify sampling times leading to the best estimation of AUC. Patients were randomly assigned to either learning (2/3) or validation (1/3) subsets. Descriptive and predictive performances of LSS models were compared using learning and validation subsets, respectively. An external validation cohort was used to validate the model and its applicability to different cTnI assays, including high-sensitive (hs) cTnI. 132 patients had full CK and cTnI dataset, 49 patients had CK-MB. For each biomarker, 180 LSS models were tested. Best LSS models were obtained for the following sampling times: T4-16 for CK, T8-T20 for cTnI and T8-T16 for CK-MB for 2-sample LSS; and T4-T16-T24 for CK, T4-T12-T20 for cTnI and T8-T16-T20 for CK-MB for 3-sample LSS. External validation was achieved on 103 anterior STEMI patients (TIMI flow 0/1), and the cTnI model applicability to recommended hs cTnI confirmed. Biomarker kinetics can be assessed with a limited number of samples using kinetic modelling. This opens the way for substantial simplification of future cardioprotection studies, more acceptable for the patients.

Food and lipid intake alters the pharmacokinetics of cyclosporine in kidney transplants

Prevention of kidney graft rejection with cyclosporine leads to a large interindividual pharmacokinetic variability. However, food intake is likely to alter cyclosporine pharmacokinetics, and therefore its efficacy. The aim of our study was to evaluate the influence of food and lipid intake on cyclosporine pharmacokinetics. Twenty-four kidney grafted patients treated with Neoral® were included in this prospective monocentric study. In all patients, the pharmacokinetics of cyclosporine was evaluated in two occasions, after meal ('feed') and without meal ('fasting'). At each occasion, blood samples were collected at trough, and 0.5, 1, 2, 3, and 4 h after administration. Cyclosporine pharmacokinetics was described using a Bayesian pharmacokinetic model including two-compartments with first-order transfer and elimination rate constants, and a gamma absorption model. Influence of meal or olive oil, very common in Morocco, was tested as covariates on interoccasion variability parameters. Cyclosporine concentration-time data were satisfactorily described using the Bayesian pharmacokinetic model. Food intake significantly increased volume of distribution and decreased elimination of cyclosporine. The influence of oil intake explained a large part of this effect, suggesting that lipid intake was the main factor of pharmacokinetic variability due to food. This intake resulted in a decrease in area under the concentration curve between two administrations of 14.6%. Food, and especially lipid intake is likely to decrease the exposure to cyclosporine and may therefore lead to a decrease in treatment efficacy. Therefore, to ensure optimal immunosuppression in time, meal composition should remain as steady as possible.

AB0310 TROUGH CONCENTRATION AND ESTIMATED CLEARANCE CAN DETECT IMMUNOGENICITY TO ADALIMUMAB IN RA PATIENTS: A PROSPECTIVE LONGITUDINAL MULTICENTRE STUDY

Background:

Anti-Drug Antibodies (ADA) to adalimumab increase drug clearance in rheumatoid arthritis (RA).

Objectives:

To study the ability of drug concentration or estimating clearance to identify ADA to adalimumab.

Methods:

Adalimumab concentration was measured with a validated ELISA. ADA was measured using a capture ELISA (Theradiag®) and the Meso scale discovery (MSD) platform. Using a bayesian PK model, adalimumab clearance was estimated at 1, 3, 6 and 12 months. Predictions for ADA presence were calculated, and the correlation between ADA and adalimumab clearance was analysed.

Results:

We analyzed 108 samples from 53 RA patients. Serum concentrations and clearance estimates showed good prediction performance for ADA presence (Table 1). There was a correlation between adalimumab clearance and ADA (Figure 1).

Table 1.

Immunogenicity prediction of adalimumab, using trough concentration or estimated clearance

Time of visitADA methodAdalimumab trough concentrationAdalimumab estimated clearanceAUC ROCp-valueAUC ROCp-valueMonth 1THER.55.6411.52.8358MSD.65.0821.61.1872Month 3THER.89.0006.91.0003MSD.73.0096.72.0131Month 6THER.95.0035.95.0035MSD.85.0004.84.0006Month 12THER.87.0045.86.0057MSD.88.0002.88.0002Figure 1.

correlation between adalimumab estimated clearance and ADA as provided by the Meso scale discovery (MSD) plateform

Conclusion:

Adalimumab concentration and clearance should be considered as reliable predictors for ADA presence in RA patients.

Acknowledgments:

Measurement of adalimumab serum concentrations was performed within the ‘Centre pilote de suivi biologique des anticorps thérapeutiques’ (CePiBAc)– Pilot centre for therapeutic antibodies monitoring platform of Tours University Hospital, which was cofinanced by the European Regional Development Fund (ERDF). We thank Oscar Knight, Delphine Delord and Fabien Giannoni (ABIRISK lab technician), Caroline Brochon and Anne Claire Duveau (CePIBAc), Aliette Decock-Giraudaud (Centre de ressource-Biobank), Sophie Tourdot (ABRISIK Project manager), Aline Doublet (Assistance Publique Hopitaux de Paris, Agnès Hincelin-Méry (Sanofi, Chilly-Mazarin, France). This work has received support from the Innovative Medicines Initiative Joint Undertaking (IMI JU) under grant agreement no. 115303, the resources of which are composed of financial contributions from the European Union’s Seventh Framework Programme (FP7/2007-2013) and European Federation of Pharmaceutical Industries and Associations (EFPIA) companies’ in-kind contributions.

Disclosure of Interests:

David Ternant Consultant of: Sanofi and Amgen., Jamal Elhasnaoui: None declared, Natacha Szely: None declared, Salima Hacein-Bey: None declared, Aude Gleizes: None declared, Christophe Richez Consultant of: Abbvie, Amgen, Mylan, Pfizer, Sandoz and UCB., Jessica Manson: None declared, Martin SOUBRIER: None declared, Olilvier Brocq: None declared, Jérôme Avouac: None declared, Anna Fogdell-Hahn Grant/research support from: Biogen Idec and Pfizer., Consultant of: Pfizer, Biogen, Merck-Serono, and Sanofi-Genzyme., Pierre Dönnes: None declared, Gilles Paintaud Grant/research support from: Amgen, Genzyme (Sanofi), Lilly, Merck, Novartis, and Roche Pharma., Consultant of: Chugai, Novartis and Shire (Takeda), with remunerations received by his institution., Céline Desvignes: None declared, Florian Deisenhammer: None declared, Sebastian Spindeldreher Employee of: Novartis, Marc Pallardy: None declared, Xavier Mariette Consultant of: BMS, Gilead, Medimmune, Novartis, Pfizer, Servier, UCB, Denis Mulleman Grant/research support from: Non-governmental organisation Lions Club Tours Val de France, French Society for Rheumatology., Consultant of: Pfizer, Novartis.

Influence of Antigen Mass on the Pharmacokinetics of Therapeutic Antibodies in Humans

Therapeutic antibodies are increasingly used to treat various diseases, including neoplasms and chronic inflammatory diseases. Antibodies exhibit complex pharmacokinetic properties, notably owing to the influence of antigen mass, i.e. the amount of antigenic targets to which the monoclonal antibody binds specifically. This review focuses on the influence of antigen mass on the pharmacokinetics of therapeutic antibodies quantified by pharmacokinetic modelling in humans. Out of 159 pharmacokinetic studies, 85 reported an influence of antigen mass. This influence led to non-linear elimination decay in 50 publications, which was described using target-mediated drug disposition or derived models, as quasi-steady-state, irreversible binding and Michaelis-Menten models. In 35 publications, the pharmacokinetics was apparently linear and the influence of antigen mass was described as a covariate of pharmacokinetic parameters. If some reported covariates, such as the circulating antigen level or tumour size, are likely to be correlated to antigen mass, others, such as disease activity or disease type, may contain little information on the amount of antigenic targets. In some cases, antigen targets exist in different forms, notably in the circulation and expressed at the cell surface. The influence of antigen mass should be soundly described during the early clinical phases of drug development. To maximise therapeutic efficacy, sufficient antibody doses should be administered to ensure the saturation of antigen targets by therapeutic antibodies in all patients. If necessary, antigen mass should be taken into account in routine clinical practice.

Concurrent losses of skeletal muscle mass, adipose tissue and bone mineral density during bevacizumab / cytotoxic chemotherapy treatment for metastatic colorectal cancer

BACKGROUND

Changes in skeletal muscle mass (SMM), total adipose tissue mass (TAT) or bone mineral density (BMD) have been described in patients with cancer undergoing various treatments; simultaneous variations of all 3 tissues has not been reported.

METHODS

Data were prospectively collected in a clinical study (NCT00489697) including patients with liver metastases of colorectal cancer who received 4 cycles of bevacizumab in combination with cytotoxic chemotherapy. Computerized tomography (CT) at baseline and after chemotherapy was used to quantify skeletal muscle and adipose tissue cross-sectional areas, and mean lumbar spine BMD using validated approaches.

RESULTS

After exclusion of patients lacking adequate CT images or missing data, 72 subjects were included. Patients were 63% male, aged 63.2 ± 10.3 years, 100% had liver metastases and 54%, 24% and 22% respectively has 0, 1 and ≥2 extrahepatic metastases. 100% tolerated 4 cycles of treatment and none showed progressive disease at the end of treatment. The scan interval was 70 days (95% CI, 62.3 to 80.5). Thresholds for loss of tissue were defined as loss ≥ measurement error. 10% of patients showed no loss of any tissue and a further 43% lost one tissue (SMM, TAT or BMD); 47% of patients lost 2 tissues (16.5% lost SMM + TAT, 8% lost SMM + BMD, 10% lost TAT + BMD) or all 3 tissues (12.5%). Catabolic behavior (2 or 3 tissue loss vs 0 or 1 tissue loss) associated with disease burden, including unresectable primary tumor (p = 0.010), presence of extrahepatic (EH) metastases (p = 0.039) and number of EH metastases (p = 0.004). No association was found between the number of tissues lost and treatment response, which was uniformly high, or treatment toxicity, which was uniformly low.

CONCLUSION

Multiple tissues can be measured in routine CT images and these show considerable inter-individual variation. Substantial losses in some individuals appear to associate with disease burden.

Enhanced Amikacin Diffusion With Ultrasound and Microbubbles in a Mechanically Ventilated Condensed Lung Rabbit Model

The poor diffusion of intravenous antibiotics in lung tissue makes nosocomial pneumonia challenging to treat, notably in critical patients under mechanical ventilation. The combination of ultrasound and microbubbles (USMB) is an emerging method for non-invasive and targeted enhancement of uptake of various drugs in several organs. This study aims to evaluate if USMB may increase amikacin concentration in condensed lung tissues in a mechanically ventilated rabbit model. When applied 60 or 160 min after the beginning of an intravenous amikacin infusion, USMB increased amikacin concentration in the condensed lung tissue by 1.33 (p = 0.025) or 1.56-fold (p = 0.028) respectively. When applied 70 min after the beginning of an intravenous amikacin infusion, USMB increased amikacin concentration in the muscle tissue by 2.52 (p = 0.025). In conclusion, this study demonstrates that USMB is a promising method for the targeted delivery of amikacin in mechanically ventilated condensed lung, thus opening new therapeutic fields against lung infections.

Methotrexate effect on immunogenicity and long-term maintenance of adalimumab in axial spondyloarthritis: a multicentric randomised trial

Objectives

Anti-drug antibodies (ADA) are responsible for decreased adalimumab efficacy in axial spondyloarthritis (SpA). We aimed to evaluate the ability of methotrexate (MTX) to decrease adalimumab immunisation.

Methods

A total of 110 patients eligible to receive adalimumab 40 mg subcutaneously (s.c.) every other week were randomised (1:1 ratio) to receive, 2 weeks before adalimumab (W-2) and weekly, MTX 10 mg s.c. (MTX+) or not (MTX−). ADA detection and adalimumab serum concentration were assessed at weeks 4 (W4), 8 (W8), 12 (W12) and 26 (W26) after starting adalimumab (W0). The primary outcome was the proportion of patients with ADA at W26. Four years after the study completion, we retrospectively analysed adalimumab maintenance in relation with MTX co-treatment duration.

Results

We analysed data for 107 patients (MTX+; n=52; MTX-; n=55). ADA were detected at W26 in 39/107 (36.4%) patients: 13/52 (25%) in the MTX+ group and 26/55 (47.3%) in the MTX− group (p=0.03). Adalimumab concentration was significantly higher in the MTX+ than MTX− group at W4, W8, W12 and W26. The two groups did not differ in adverse events or efficacy. In the follow-up study, MTX co-treatment >W26 versus no MTX or ≤W26 was significantly associated with adalimumab long-term maintenance (p=0.04).

Conclusion

MTX reduces the immunogenicity and ameliorate the pharmacokinetics of adalimumab in axial SpA. A prolonged co-treatment of MTX>W26 seems to increase adalimumab long-term maintenance.

[Pharmacokinetic variability of therapeutic antibodies]

Therapeutic antibodies have been increasingly used for the treatment of various diseases, including cancers and chronic inflammatory diseases. The pharmacokinetic interindividual variability of mAbs is large and influences, at least in part, the clinical response to antibody treatment. This variability is explained by a number of individual sources of variability, which are reviewed here. Some of them are major because they are frequently reported to greatly influence the interindividual variability; notably, increased body size, the presence of anti-drug antibodies, and high antigen mass are associated with decreased antibody concentrations. Other individual sources of variability are of less critical importance. They include sex, age, co-treatments, or genetic polymorphisms of IgG Fc receptors (FcgRs). The interindividual variability of antibody pharmacokinetics should be soundly described in order to design optimal dosing strategy.

CD4+ count-dependent concentration-effect relationship of rituximab in rheumatoid arthritis

AIMS

Rituximab is approved in rheumatoid arthritis (RA). A substantial decrease in CD4+ count was observed in responders after a single cycle of treatment. This study aimed to describe and quantifying the influence of CD4+ count depletion on the concentration-response relationship of rituximab in RA patients.

METHODS

In this retrospective monocentric observational study, 52 patients were assessed. Repeated measurements of rituximab concentrations (pharmacokinetics), CD4+ counts (biomarker) and disease activity score in 28 joints (DAS28, clinical response) were made. Rituximab pharmacokinetics was described using a 2-compartment model, and CD4+ cell counts and DAS28 measurements were described using indirect turnover and direct Emax pharmacokinetic-pharmacodynamic models, respectively. Delay between rituximab concentrations and responses was accounted for by including biophase compartments.

RESULTS

Elimination half-life of rituximab was 18 days. The pharmacokinetic-pharmacodynamic model showed that DAS28 response to rituximab was partly associated with CD4+ cell depletion. At 6 months, a deeper DAS28 decrease was observed in patients when CD4+ cell count is decreased: median [interquartile range] of DAS28 was 3.7 [2.9-4.4] and 4.5 [3.7-5.3] in patients with and without CD4+ decrease, respectively.

CONCLUSIONS

This is the first study to quantify the relationship between rituximab concentrations, CD4+ count and DAS28 in RA patients. This model showed that approximately 75% of patients had CD4+ count decrease, and that the clinical improvement is 2-fold higher in patients with CD4+ cells decrease than in others.

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.

Nonlinear pharmacokinetics of rituximab in non-Hodgkin lymphomas: A pilot study

AIMS

Rituximab is an anti-CD20 monoclonal antibody approved in non-Hodgkin lymphoma (NHL). This study aimed to assess the relationship between antigen mass and nonlinear pharmacokinetics of rituximab in NHL patients.

METHODS

In a retrospective cohort of 25 NHL patients treated with rituximab, antigen mass was assessed at baseline by measuring metabolic tumour volume (MTV) by positron emission tomography. Rituximab pharmacokinetics was described using a semimechanistic 2-compartment model including a latent target antigen. Rituximab target-mediated elimination was described as irreversible binding between rituximab and it target. Histology (follicular or diffuse large B-cell lymphomas), initial MTV and body weight were tested as covariates on pharmacokinetic parameters.

RESULTS

The model allowed a satisfactory description of rituximab serum concentrations. Target-mediated elimination was maximum at the beginning of treatment and became negligible towards the end of follow-up. The second-order elimination of rituximab due to target binding and complex elimination increased with baseline MTV. Central volume of distribution increased with body weight (P = .022) and baseline MTV (P = .005).

CONCLUSIONS

This study quantified for the first time the target-mediated elimination of rituximab in NHL patients and confirmed rituximab retention by antigen mass.

A recycling anti-transferrin receptor-1 monoclonal antibody as an efficient therapy for erythroleukemia through target up-regulation and antibody-dependent cytotoxic effector functions

Targeting transferrin receptor 1 (TfR1) with monoclonal antibodies is a promising therapeutic strategy in cancer as tumor cells often overexpress TfR1 and show increased iron needs. We have re-engineered six anti-human TfR1 single-chain variable fragment (scFv) antibodies into fully human scFv₂-Fcγ1 and IgG1 antibodies. We selected the more promising candidate (H7), based on its ability to inhibit TfR1-mediated iron-loaded transferrin internalization in Raji cells (B-cell lymphoma). The H7 antibody displayed nanomolar affinity for its target in both formats (scFv₂-Fcγ1 and IgG1), but cross-reacted with mouse TfR1 only in the scFv₂-Fc format. H7 reduced the intracellular labile iron pool and, contrary to what has been observed with previously described anti-TfR1 antibodies, upregulated TfR1 level in Raji cells. H7 scFv₂-Fc format elimination half-life was similar in FcRn knock-out and wild type mice, suggesting that TfR1 recycling contributes to prevent H7 elimination in vivo. In vitro, H7 inhibited the growth of erythroleukemia and B-cell lymphoma cell lines (IC₅₀ 0.1 µg/mL) and induced their apoptosis. Moreover, the Im9 B-cell lymphoma cell line, which is resistant to apoptosis induced by rituximab (anti-CD20 antibody), was sensitive to H7. In vivo, tumor regression was observed in nude mice bearing ERY-1 erythroleukemia cell xenografts treated with H7 through a mechanism that involved iron deprivation and antibody-dependent cytotoxic effector functions. Therefore, targeting TfR1 using the fully human anti-TfR1 H7 is a promising tool for the treatment of leukemia and lymphoma.

17p deletion strongly influences rituximab elimination in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most common type of leukemia and the anti-CD20 monoclonal antibody, rituximab, represents the therapeutic gold standard for more than 2 decades in this pathology, when used in combination with chemotherapy. However, some patients experience treatment resistance or rapid relapses, and in particular, those harboring a 17p/TP53 deletion (del(17p)). This resistance could be explained by a chemo-resistance, but it could also result from the direct impact of del(17p) on the pharmacokinetics of rituximab, which represents the aim of the present study. Accordingly, 44 CLL patients were included in the study, and among them 9 presented a del(17p). Next, a total of 233 rituximab sera were selected for a pharmacokinetic study and analyzed in a two-compartment model showing important differences when del(17p) CLL patients were compared with non-del(17p) patients treated with rituximab and chemotherapy: (1) clearance of rituximab was faster; (2) central volume of rituximab distribution V1 (peripheral blood) was reduced while peripheral volume V2 (lymphoid organs and tissues) was increased; and (3) the rate of rituximab elimination (Kout) was faster. In contrast, the group with a better prognosis harboring isolated del(13q) presented a slower rate of elimination (Kout). Pharmacokinetic parameters were independent from the other factors tested such as age, sex, chemotherapy regimen (fludarabine/cyclophosphamide versus bendamustine), IGHV mutational status, and FCGR3A 158VF status. In conclusion, this study provides an additional argument to consider that del(17p) is effective not only to control chemoresistance but also monoclonal antibody activity, based on higher rituximab turnover.

New steps in infliximab therapeutic drug monitoring in patients with inflammatory bowel diseases

AIMS

Therapeutic drug monitoring (TDM) of infliximab (IFX) appears to be beneficial for patients with inflammatory bowel disease (IBD). However, the recommended target concentrations depend partly on the method used to quantify IFX. Since we recently developed a liquid chromatography-tandem mass spectrometry method to quantify IFX, we aimed to determine IFX trough concentrations (Cmin) associated with biological remission.

METHODS

We retrospectively measured IFX Cmin in sera from 55 patients with IBD, on IFX maintenance therapy, and for whom demographic, biological and clinical data were collected from medical records. A threshold of IFX Cmin associated with biological remission (defined by C-reactive protein < 5 mg l^-1 and faecal calprotectin <150 μg g^-1 ) was determined using receiver operating characteristics analysis.

RESULTS

IFX Cmin ranged from <1 mg l^-1 to 57.2 mg l^-1 . IFX Cmin were higher (P = 0.038) in patients with biological remission and a cut-off of IFX Cmin set to 6.2 mg l^-1 was associated with biological remission (sensitivity = 0.75, 95% confidence interval 0.58-0.75; specificity = 0.61, 95% confidence interval 0.39-0.83).

CONCLUSION

Liquid chromatography-tandem mass spectrometry measurement of IFX Cmin and the determination of a new threshold of IFX Cmin associated with biological remission are new steps towards IFX treatment personalization in patients with IBD.

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.

Modeling Immunization To Infliximab in Children With Crohn's Disease Using Population Pharmacokinetics: A Pilot Study

BACKGROUND

Antidrug antibodies (ADAs) dramatically increase infliximab clearance and are responsible for underexposure to the drug, leading to treatment failure. This pilot study aimed at developing a population pharmacokinetic model to detect and describe an early increase in infliximab clearance due to ADA.

METHODS

Twenty children with Crohn's disease (CD) were followed for 1 year or until treatment failure. Infliximab trough concentration, ADA, C-reactive protein (CRP), and Paediatric Crohn's Disease Activity Index (PCDAI) were recorded at each visit. A time-varying clearance population pharmacokinetic model was built to detect and describe an increase in infliximab clearance, independent from ADA testing. Factors associated with clearance variation and the relationships between infliximab concentrations, clearance variation, and clinical response were investigated.

RESULTS

The model detected important increases in clearance in 4 patients. These patients had suboptimal early response, with higher mean PCDAI (P = 0.0086) and CRP (P = 0.028) compared with other patients. Two of them had detectable ADA. Clearance increase as described by the model and lower infliximab trough concentration at week 2 were associated with poorer outcomes in a multivariate Cox model (P = 0.001 and P = 0.0048, respectively).

CONCLUSIONS

Being able to detect an increase in infliximab clearance, this model could allow the early detection of immunization to infliximab and therefore could help with dose adjustment in patients with CD. Moreover, the results suggest that clearance variations could be used as a predictive marker of clinical response. These findings need to be confirmed in a larger cohort, however, and predictive factors of clearance increase have to be investigated.