Low Drug Levels Research Articles

Importance of Therapeutic Drug Monitoring in the Treatment of Active Tuberculosis - A Retrospective Study of 4 Cases

Background: In the treatment of active tuberculosis, therapeutic drug monitoring (TDM) is used to optimize dosing that maximizes therapeutic benefit while minimizing toxicity. In Morocco, TDM is not routinely used, yet low levels of anti-TB drugs can be associated with poorer treatment outcomes. Methods: We retrospectively checked our archives for patients with active TB for whom TDM was performed during 2014. Medical records were reviewed to abstract demographic, clinical, radiographic and microbiological data including time until smear and culture conversion. Then, we looked for cases with delay of TB conversion. Results: In total, 24 patients were identified, for whom TDM was performed, they all had low serum drug levels. Among them, 4 patients showed delayed bacteriological conversion. Conclusions: Our study cases are showing the benefit of serum dosage in the follow-up of the patients showing a delay of sputum examination conversion, both direct and culture, during their evolutions. TDM is potentially useful for the treatment of active TB, but is currently underused in Morocco.

OC-001 Clinical Factors that Determine Primary Non-Response (PNR) to anti-TNF Drugs in Patients with Active Luminal Crohn’s Disease (CD)

Introduction 10–40% of patients with CD fail to respond to anti-TNF induction therapy at 10–14 weeks. The mechanisms underlying PNR are uncertain but a better understanding of these factors might allow more cost-effective, individualised anti-TNF treatment. We present an interim analysis of PNR in the PANTS cohort. Methods The PANTS study is a UK wide, multi-centre 3 year prospective, observational cohort study investigating PNR to Infliximab (IFX) and Adalimumab (ADA). Serial collection of clinical data and sampling of DNA, RNA, serum and stool will allow down-stream multi-omic studies. Inclusion criteria include active luminal Crohn’s disease supported by raised CRP or Calprotectin and no prior exposure to anti-TNF therapy. PNR was defined as failure of HBI to fall by ≥3 points or to ≤4 AND failure of CRP to fall by ≥50% or to ≤3 mg/dL OR failed steroid withdrawal. Drug and anti-drug antibody levels were measured using Immunodiagnostic drug tolerant assays. Results 1176 (568 male) patients aged 4.0–77.2 years have been recruited from 106 sites and reached 14 weeks after quality control. Patients were treated with IFX (695, 59.1%) or ADA (481, 40.9%). At entry 39.7% of patients had an HBI of ≤4, 32.14% ≥ 8, and 29.4% of patients had a CRP ≤ 3, 42.4% had a CRP ≥ 10. Concomitant drugs at entry included steroids 18.5%, azathioprine 39.2%, mercaptopurine 7.40%, methotrexate 5.4%. PNR could be assessed at week 14 for 1090 (92.7%) patients. PNR was observed in 16.9% and 23.7% of the IFX and ADA treated patients respectively. This difference was not significant once adjusted for baseline disease activity (P = 0.2). To date only 2 patients who met the week 14 PNR criteria achieved remission on anti-TNF at 1 year (sensitivity 0.99, specificity 0.4). A multivariate regression identified albumin (P = 0.0036) as associated with PNR at Week 14 in the IFX group and drug level (P = 0.00035), calprotectin (P = 0.033), albumin (P = 0.037) and anti-drug antibody level (P = 0.024) in the ADA group. In combined analysis BMI (P = 0.017) and drug level (P = 0.024) were associated with PNR. 75 IFX and 36 ADA patients had anti-drug antibodies at week 14, of which 33 and 6 patients had no detectable drug. Development of anti-drug antibodies in the first 14 weeks was associated with monotherapy (P = 0.00021) and was seen more commonly in patients with early infusion reactions (P = 2x10 −16 ). Conclusion The PANTS study has provided a real world estimate of PNR and associated risk factors in a large prospective cohort using a simple clinical and biochemical definition at week 14 that predicts non-remission at week 54. Low drug level and immunogenicity are associated with PNR, infusion reactions and monotherapy suggesting early measurement might help prevent and manage PNR. Disclosure of Interest G. Heap Conflict with: Abbvie, T. Ahmad Grant/research support from: Abbvie, MSD, Hospira, Inflectra, Conflict with: Abbvie, MSD

Why Biologic Therapies Sometimes Lose Efficacy.

Biologic therapies for psoriasis are associated with loss of response over time. Immunogenicity, suboptimal dosing, low serum drug levels, and intermittent or episodic therapy have been documented as explanations for this phenomenon. Use of an immunomodulatory agent can reduce the risk of immunogenicity and improve clinical response.

High frequency of antidrug antibodies and association of random drug levels with efficacy in certolizumab pegol-treated patients with rheumatoid arthritis: results from the BRAGGSS cohort

ObjectivesTo evaluate (i) the association between random certolizumab drug levels, antidrug antibodies (ADAbs) and treatment response in patients with rheumatoid arthritis (RA); (ii) longitudinal factors associated with ADAbs and certolizumab...

Functional oncogene signatures guide rationally designed combination therapies to synergistically induce breast cancer cell death.

A critical first step in the personalized approach to cancer treatment is the identification of activated oncogenes that drive each tumor. The Identification of driver oncogenes on a patient-by-patient basis is complicated by the complexity of the cancer genome and the fact that a particular genetic alteration may serve as a driver event only in a subset of tumors that harbor it. In this study, we set out to identify the complete set of functional oncogenes in a small panel of breast cancer cell lines. The cell lines in this panel were chosen because they each contain a known receptor tyrosine kinase (RTK) oncogene. To identify additional drivers, we integrated functional genetic screens with copy number and mutation analysis, and cancer genome knowledge databases. The resulting functional oncogene signatures were able to predict responsiveness of cell lines to targeted inhibitors. However, as single agents, these drugs had little effect on clonogenic potential. By contrast, treatment with drug combinations that targeted multiple oncogenes in the signatures, even at very low doses, resulted in the induction of apoptosis and striking synergistic effects on clonogenicity. In particular, targeting a driver oncogene that mediates AKT phosphorylation in combination with targeting the anti-apoptotic BCL2L1 protein had profound effects on cell viability. Importantly, because the synergistic induction of cell death was achieved using low levels of each individual drug, it suggests that a therapeutic strategy based on this approach could avoid the toxicities that have been associated with the combined use of multiple-targeted agents.

Distinct Pharmacodynamic Activity of Rilpivirine in Ectocervical and Colonic Explant Tissue.

A long-acting injectable form of rilpivirine (RPV) is being evaluated in clinical trials for the prevention of HIV infection. Preclinical testing was undertaken to define RPV pharmacokinetic (PK) and pharmacodynamic (PD) activities in ectocervical and colonic tissue treated in vitro Tenfold dilutions of RPV were added to the basolateral medium of polarized ectocervical and colonic explant tissues. To half the explants, HIV-1BaL was applied to the apical tissue surface. After culture overnight, all the explants were washed and the RPV in the explants not exposed to HIV was quantified using a validated liquid chromatography-mass spectrometry assay. For efficacy, explants exposed to HIV remained in culture, and supernatants were collected to assess viral replication using a p24 enzyme-linked immunosorbent assay. The data were log10 transformed, and PK/PD correlations were determined using GraphPad Prism and SigmaPlot software. The application of RPV to the basolateral medium at 10 μM and 1 μM was effective in protecting ectocervical and colonic tissues, respectively, from HIV infection. When the RPV in paired ectocervical and colonic explant tissues was quantified, significant inverse linear correlations (P < 0.001) between p24 and RPV concentrations were obtained; more viral replication was noted at lower drug levels. Using a maximum effect model, RPV concentrations of 271 nM in ectocervical tissue and 45 nM in colonic tissue were needed to achieve a 90% effective concentration (EC90). These data demonstrate that RPV can suppress HIV infection in mucosal tissue but that higher levels of RPV are needed in female genital tract tissue than in gastrointestinal tract tissue for protection.

Approach to Optimize Anti-TNF-α Therapy in Patients With IBD.

Tumor necrosis factor-α (TNF-α) is an inflammatory cytokine that plays a major role during the initiation and perpetuation of inflammatory bowel disease (IBD). Anti-TNF-α agents are the most widely used biologics that specifically target either or both circulating and membrane-bound TNF-α, thus preventing its pro-inflammatory activity. Despite their efficacy, one third of the patients receiving anti-TNF-α agents are primary non-responders and nearly half of the patients that initially respond may subsequently lose response (secondary loss of response). Many of these cases can be explained by immunogenicity, which can lead to lower drug levels associated with reduced response and serious adverse effects that cause patients to withdraw from treatment. New treatment algorithms instruct practitioners to check drug and antibody levels when there is loss of response, and then provide guidance towards either dose optimization and/or change in the biologic agent or class to help regain efficacy.

A randomized safety and pharmacokinetic trial of daily tenofovir 1% gel in term and near-term pregnancy.

IntroductionVaginal tenofovir (TFV) 1% gel may reduce incident HIV-1 and herpes simplex virus 2 infection. Pregnancy may increase risk of HIV acquisition, and incident HIV in pregnancy potentiates perinatal HIV transmission. Our objective was to investigate the safety and pharmacokinetics of seven days of TFV 1% vaginal gel in term and near-term pregnancy.MethodsNinety-eight healthy pregnant women, stratified to a term cohort followed by a near-term cohort, were enrolled into a 2:1 randomized, double-blinded, placebo-controlled trial. Women received TFV or placebo gel for seven consecutive days with pharmacokinetic sampling on days 0 and 6. Maternal and cord blood were collected at delivery. Primary end points included laboratory and genital adverse events, adverse pregnancy and neonatal outcomes, and maternal TFV levels.ResultsMost adverse events were grade 1 and none of the grade 3 or 4 adverse events were related to study product. There was no significant difference in safety end points between the two pregnancy cohorts (p=0.18); therefore, their data were combined. Primary safety end point rates were similar for mothers randomized to the TFV gel vs placebo arm (72.7 and 68.8%, p=0.81). The same was true for newborns in the TFV gel vs placebo arms (4.5% vs 6.3%, p=0.66). All women randomized to TFV had quantifiable serum levels within eight hours of dosing, with low overall median (interquartile range) day 0 and day 6 peak values (3.8 (2.0 to 7.0) and 5.8 (2.6 to 9.4) ng/mL, respectively).ConclusionsDaily TFV 1% vaginal gel use in term and near-term pregnancy appears to be safe and produces low serum drug levels.

Certolizumab treatment during late pregnancy in patients with rheumatic diseases: Low drug levels in cord blood but possible risk for maternal infections. A case series of 13 patients

ObjectiveDue to reduction of immune-suppressive drugs, patients with rheumatic diseases can experience an increase in disease activity during pregnancy. In such cases, TNF-inhibitors may be prescribed. However, monoclonal antibodies with the Fc moiety are actively transported across the placenta, resulting in therapeutic drug levels in the newborn. As certolizumab (CZP) lacks the Fc moiety, it may bear a lower risk for the child. MethodWe report a case series of thirteen patients (5 with rheumatoid arthritis and 8 with spondyloarthritis) treated with CZP during late pregnancy to control disease activity. ResultCZP measured in cord blood of eleven infants ranged between undetectable levels and 1μg/mL whereas the median CZP level of maternal plasma was 32.97μg/mL. Three women developed an infection during the third trimester, of whom one had a severe infection and one had an infection that resulted in a pre-term delivery. During the postpartum period, 6 patients remained on CZP while breastfeeding. CZP levels in the breast milk of two breastfeeding patients were undetectable. ConclusionThe lack of the active transplacental transfer of CZP gives the possibility to treat inflammatory arthritis during late gestation without potential harm to the newborn. However, in pregnant women treated with TNF-inhibitors and prednisone, attention should be given to the increased susceptibility to infections, which might cause prematurity. CZP treatment can be continued while breastfeeding.

Fecal Calprotectin Levels Can Predict Pharmacokinetics of Anti-TNF Therapy

Introduction: Even though anti-tumor necrosis factor (ATNF) agents have revolutionized the treatment of inflammatory bowel disease (IBD) many patients do not experience a benefit (primary nonresponse). This could be explained by insufficient drug, which is often seen in patients with severe intestinal disease. Fecal calprotectin is a novel marker of intestinal inflammation used to monitor patients with IBD, but it's role predicting the pharmacokinetics of ATNFs is not clear. The aim of this study was to assess if fecal calprotectin (FCP) pre-ATNF therapy can predict low drug levels and need for dose escalation. Methods: We designed a cohort study of patients 18 years or older with IBD who started infliximab (IFX) or adalimumab (ADA) at our tertiary IBD center. Predictive variables (before initiating ATNF therapy) included demographics, disease phenotype, FCP, C-Reactive protein (CRP), albumin and concomitant use of immunomodulators. The primary outcome was ATNF serum levels as a continuous and “adequate levels” as dichotomous variable (a threshold level of 3 and 5 mg/dL were used for IFX and ADA respectively as per current evidence). The secondary outcome was need for drug dose escalation.Table 2: Correlations of several measurements and anti-TNF levelsResults: 31 patients were included. Baseline characteristics of the study population are in Table 1. IFX levels were measured between weeks 14 and 22, while ADA levels were measured between weeks 12 and 36. Higher FCP levels predicted ATNF primary non response (ROC: 0.78, p=0.78). There was a negative correlation between pre-treatment FCP and drug levels and CRP, but only the former achieved statistical significance (rho: -0.5, p=0.0042 [Figure 1] and rho: -0.26, p=0.16). Concomitantly, there was a significant correlation between drug levels and pre-therapy serum albumin (rho: 0.38, p=0.035). Patients with a FCP ≥ 150 μg/g had an increased chance of requiring dose escalation (OR: 12 [95%CI: 1.2-117.4], p=0.03).Figure 1Table 1: Baseline characteristics of the study populationConclusion: Baseline FCP is correlated with drug levels achieved after starting ATNF therapy and those who require dose escalation. FCP can lead to more precise dosing of ATNF, decreasing the rate of primary non-responders by predicting the group of patients that may require higher induction/maintenance doses. Further, larger studies are warranted.

Cystic echinococcosis therapy: Albendazole-loaded lipid nanocapsules enhance the oral bioavailability and efficacy in experimentally infected mice

Therapeutic failures attributed to medical management of cystic echinococcosis (CE) with albendazole (ABZ) have been primarily linked to the poor drug absorption rate resulting in low drug level in plasma and hydatid cysts. Lipid nanocapsules (LNCs) represent nanocarriers designed to encapsulate lipophilic drugs, such as ABZ. The goals of the current work were: (i) to characterize the plasma and cyst drug exposure after the administration of ABZ as ABZ-LNCs or ABZ suspension (ABZ-SUSP) in mice infected with Echinococcus granulosus, and ii) to compare the clinical efficacies of both ABZ formulations. Enhanced ABZ sulphoxide (ABZ-SO) concentration profiles were obtained in plasma and cysts from ABZ-LNC treated animals. ABZSO exposure (AUC0–LOQ) was significantly higher in plasma and cyst after the ABZ-LNC treatments, both orally and subcutaneously, compared to that observed after oral administration of ABZ-SUSP. Additionally, ABZSO concentrations measured in cysts from ABZ-LNC treated mice were 1.7-fold higher than those detected in plasma. This enhanced drug availability correlated with an increased efficacy against secondary CE in mice observed for the ABZ-LNCs, while ABZ-SUSP did not reach differences with the untreated control group. This new pharmacotechnically-based strategy could be a potential alternative to improve the treatment of human CE.

Duloxetine enters the brain – but why is it not found in the cerebrospinal fluid

Objective: Antidepressants enter the brain to reach their site of action. However, little is known about duloxetineʼs ability to enter the brain and cerebrospinal fluid (CSF). Aim of the study was to measure blood and CSF concentrations of duloxetine and to account for the distribution between the two compartments. Method: Concentrations of duloxetine were measured in blood serum and CSF of 19 patients treated with daily doses of 30–120 mg. Daily doses were correlated with serum and cerebrospinal fluid concentrations and serum concentrations were correlated with concentrations in cerebrospinal fluid. Results: Serum concentrations of duloxetine showed a moderate but significant correlation with the applied daily dose, r = +0.473, p = 0.04. Duloxetine concentrations in the cerebrospinal fluid above the designated limit of quantification of 2.0 ng/mL were only found in three of the 19 patients. Conclusions: Contrasting to own preceding studies on different antidepressants, the findings indicate a very different distribution pattern. Very low concentrations in the CSF may be due to the fact that the drug crosses the blood-cerebrospinal fluid barrier much worse than other antidepressants do, suggesting a low ability of duloxetine to enter the brain. Alternatively, low drug levels may be interpreted in a sense of a missing residence time in cerebrospinal fluid due to active transport mechanisms out of this environment either back into the bloodstream or into the brain.

Drug trough levels predict therapeutic responses to dose reduction of adalimumab for rheumatoid arthritis patients during 24 weeks of follow-up.

To evaluate the impact of adalimumab (ADA) dose-halving on therapeutic responses and drug levels, the differences in drug levels among patients with different therapeutic responses and the optimal baseline cut-off ADA levels for predicting persistent remission or low disease activity (LDA) at week 24 of dose-halving therapy in 64 RA patients who had already achieved LDA or remission at baseline. Anti-ADA antibody levels were determined by bridging ELISA, ADA levels were evaluated using sandwich ELISA and therapeutic responses were assessed by the 28-joint DAS change. The optimal cut-off drug levels for predicting persistent remission were determined by receiver operating characteristic curve analysis. At baseline, 25 (39.1%) and 39 (60.9%) patients had achieved remission and LDA, respectively. After 24 week ADA dose-halving, persistent remission was observed in 23 patients, remission turned LDA in 2 patients, persistent LDA in 24 patients and disease flare in 15 (23.5%) patients. Three patients who developed anti-ADA antibodies at week 24 of dose-halving had very low drug levels and disease flare. Among 61 anti-ADA antibody-negative patients, ADA levels declined by half after 24 weeks of dose-halving (median 5.5 vs 2.6 μg/ml). Baseline ADA levels were significantly higher in patients with persistent remission (median 10.5 μg/ml) or LDA (4.5 μg/ml) than in those with disease flare (0.9 μg/ml), indicating associations of ADA levels with therapeutic responses. An ADA level above the cut-off value of 6.4 μg/ml might predict persistent remission after dose-halving with high sensitivity and specificity. ADA dose-halving is feasible for patients who have achieved remission and sufficient drug levels. Drug level monitoring may help clinicians optimize the dosing regimen and prevent overtreatment for patients receiving anti-TNF-α therapy.

Abstract 4531: Effects of drug load on therapeutic index for antibody-maytansinoid conjugates

Abstract Antibody-drug conjugates (ADCs) are being actively pursued as a new modality to treat cancer following the regulatory approval of Adcetris@ and Kadcyla@. ADCs consist of a cytotoxic agent, or drug, conjugated to a targeting antibody (Ab) through a linker. The two approved ADCs (and most ADCs now in the clinic) are heterogeneous conjugates with an average molar drug to Ab ratio (DAR) of 3-4 (potentially ranging from 0-8 for individual molecules). To understand the effects of different DAR ranges on the preclinical properties of ADCs using a maytansinoid cytotoxic agent, we prepared a series of conjugates with a cleavable linker (M9346A-sulfo-SPDB-DM4 targeting folate receptor alpha) or an uncleavable linker (J2898A-SMCC-DM1 targeting epidermal growth factor receptor) with varying DAR, and evaluated their biochemical characteristics, in vivo stability, efficacy, and tolerability. Both M9346A-sulfo-SPDB-DM4 and J2898A-SMCC-DM1 conjugates with low (average ∼2, range 0-4) to very high DAR (average 10, range 7-14) were prepared in good yield, high monomer content and low free drug levels. At constant Ab concentration, the in vitro potency consistently increased with increasing DAR. We then characterized the in vivo disposition of these ADCs. First, pharmacokinetic analysis showed that conjugates with an average DAR below ∼6 had comparable clearance rates, but at an average DAR around 9-10 rapid clearance was observed. Biodistribution studies in mice showed that these 9-10 DAR conjugates rapidly distribute to the liver, with the maximum%ID/g for this organ at 24-28% compared with 7-10% for lower DAR conjugates (all at 2-6 h post-injection). We further studied the efficacy of these ADCs in mouse xenograft models at both constant antibody and constant maytansinoid doses. At constant Ab dose, conjugates with average DAR ∼6 are more efficacious than conjugates with DAR ∼3. However, DAR 9-10 conjugates are either less or similarly active compared to DAR 6 conjugates, consistent with the observed rapid clearance. At constant maytansinoid dose, conjugates with 2 - 6 DAR show similar efficacy, while those with 9-10 DAR were again less active. Tolerability studies monitoring body weight loss show that conjugates with different DAR, even as high as 9-10, have comparable tolerability based on total administered maytansinoid dose. In summary, our preclinical findings on tolerability and efficacy suggest that maytansinoid conjugates with DAR in the range between 2 - 6 have better therapeutic index than conjugates with very high DAR (∼9-10). These very high DAR ADCs suffer from decreased efficacy likely due to faster clearance. These results support the use of DAR 3-4 for maytansinoid ADCs, but suggest the exploration of lower or higher DAR depending on the biology of the target antigen. Citation Format: Xiuxia Sun, Jose F. Ponte, Nicholas C. Yoder, Jennifer Coccia, Leanne Lanieri, Rassol Laleau, Qifeng Qiu, Rui Wu, Erica Hong, Megan Bogalhas, Lintao Wang, Erin K. Maloney, Olga Ab, Hans K. Erickson, Thomas A. Keating, Ravi Chari, John M. Lambert. Effects of drug load on therapeutic index for antibody-maytansinoid conjugates. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4531. doi:10.1158/1538-7445.AM2015-4531

Optimizing Biologic Agents in Ulcerative Colitis and Crohn's Disease.

The goals of therapy in inflammatory bowel disease (IBD) are the induction and maintenance of clinical and biological remission. Mucosal healing is desirable to prevent complications and reduce the need for surgery, hospitalizations, and steroid exposure. Therapeutic monoclonal antibodies (biologic agents) have revolutionized the treatment of IBD. The initial magnitude of the clinical/biologic response to these agents has been associated with a number of underlying phenotypic features in the recipient. In addition, the durability of the initial response often declines over time. This can occur due to low drug serum drug levels, anti-drug antibodies, and a shift to alternative inflammatory pathways. This review discusses strategies that may optimize the initial response to biologics and sustain this to improve patient outcomes.

Undetectable anti-TNF drug levels in patients with long-term remission predict successful drug withdrawal.

Low drug levels are associated with emerging loss of response to anti-TNF. However, this may not be the case in patients with long-term remission. To investigate the outcome of anti-TNF discontinuation in patients with long-term remission and incidental undetectable drug levels. A retrospective cohort study examining the duration of relapse-free survival in IBD patients in remission who discontinued infliximab or adalimumab having undetectable drug levels. Forty eight patients who discontinued anti-TNF while in remission and had available drug levels were identified in two centres in France and Israel (infliximab-treated 35, adalimumab-13, Crohn's disease 30, ulcerative colitis 18, mean treatment duration of 22.7 ± 12.4 months). Endoscopy/MRE before stopping showed absence of active inflammation in 40/42 (95%) of evaluated patients, while inflammatory biomarkers (CRP and/or Calprotectin) were completely normal in only 31/48 (65%) of patients. During 12 months median follow-up, relapse occurred in 16/20 (80%) of patients who stopped anti-TNF while having measurable drug levels compared with 9/28 (32%) of patients who had undetectable drug levels (OR: 8.4, 95% CI: 2.2-32, P = 0.002). Relapse-free survival after anti-TNF cessation was significantly longer in patients with absent drug compared to those with detectable drug (P < 0.001, log rank test). On multivariate analysis, a patient's decision to stop therapy was weakly associated and abnormal inflammatory biomarkers and detectable drug levels were both strongly and independently associated with a higher risk of relapse after drug discontinuation. Incidental finding of undetectable anti-TNF drug levels in patients with stable long-term deep remission may identify a subset of patients whose clinical remission is no longer dependent on anti-TNF treatment.

Prevalence of TNF-α blocker immunogenicity in psoriatic arthritis.

The longterm use of tumor necrosis factor (TNF)-α blockers is limited by the formation of neutralizing antibodies. To the best of our knowledge, immunogenicity in psoriatic arthritis (PsA) has not been investigated in depth. Our objective was to evaluate the prevalence and significance of TNF-α blocker immunogenicity in PsA. Consecutive patients with PsA treated with either infliximab (IFX), adalimumab (ADA), or etanercept (ETN) > 3 months participated in our cross-sectional study. Their demographic and clinical characteristics, skin and joint disease activity, and records of use of methotrexate (MTX) and other medications were collected. Drug levels (ELISA) and antidrug antibodies (ADAb; Bridging ELISA) were evaluated before the next injection or infusion. A total of 93 patients with PsA were recruited (48 receiving ADA, 24 IFX, and 21 ETN), with a mean age of 53 years (range 21-83 yrs), composed of 53% women. One-fourth of the patients were concomitantly treated with MTX. Altogether, 77% of the patients demonstrated therapeutic drug levels. High levels of ADAb were found in 29% of patients taking ADA, 21% taking IFX, and 0% taking ETN. ADAb significantly correlated with lower drug levels, higher 28-joint Disease Activity Scores, and higher global assessments. MTX use correlated significantly with a lower prevalence of ADAb. Significant levels of ADAb were present in up to 29% of patients with PsA treated with ADA or IFX. ADAb clearly correlated with low therapeutic drug levels and higher disease activity variables. The use of MTX significantly decreased ADAb prevalence, and its use should be strongly considered in combination with TNF-α blocker antibodies in patients with PsA.

Detection of adalimumab and anti-adalimumab levels by ELISA: clinical considerations.

Psoriasis (Ps) is a common and stigmatizing chronic inflammatory skin disease that may cause other chronic inflammatory conditions with overlapping pathology, such as rheumatoid arthritis (RA). Tumor necrosis factor (TNF) is a proinflammatory cytokine that plays a pivotal role in chronic inflammatory and autoimmune diseases such as uveitis, multiple sclerosis, systemic lupus, arthritis, Ps, and Crohn's disease. The TNF superfamily and receptors represent active targets for drug development. Anti-TNF biological therapies, such as infliximab, adalimumab (ADL), and etanercept, are effective in treating RA, spondyloarthritis, Ps, and inflammatory bowel diseases, but long-term treatment can induce anti-drug antibody (ADA) formation associated with lower drug levels and clinical nonresponse. An investigation of the relationship between serum ADL/anti-adalimumab antibody (AAA) concentration, and clinical response in moderate to severe Ps, confirmed an association between ADL and AAA levels and response. Although the detection of ADAs can be used to determine the cause of nonresponse and aid therapy decisions, the contrary observation of long-term responders with low drug levels and detectable ADA suggests that another mechanism is also involved.

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Novel approach of MALDI drug imaging, immunohistochemistry, and digital image analysis for drug distribution studies in tissues.

Drug efficacy strongly depends on the presence of the drug substance at the target site. As vascularization is an important factor for the distribution of drugs in tissues, we analyzed drug distribution as a function of blood vessel localization in tumor tissue. To explore distribution of the anticancer drugs afatinib, erlotinib, and sorafenib, a combined approach of matrix-assisted laser desorption/ionization (MALDI) drug imaging and immunohistochemical vessel staining was applied and examined by digital image analysis. The following two xenograft models were investigated: (1) mice carrying squamous cell carcinoma (FaDu) xenografts (ntumor = 13) were treated with afatinib or erlotinib, and (2) sarcoma (A673) xenograft bearing mice (ntumor = 8) received sorafenib treatment. MALDI drug imaging revealed a heterogeneous distribution of all anticancer drugs. The tumor regions containing high drug levels were associated with a higher degree of vascularization than the regions without drug signals (p < 0.05). When correlating the impact of blood vessel size to drug abundance in the sarcoma model, a higher amount of small vessels was detected in the tumor regions with high drug levels compared to the tumor regions with low drug levels (p < 0.05). With the analysis of coregistered MALDI imaging and CD31 immunohistochemical data by digital image analysis, we demonstrate for the first time the potential of correlating MALDI drug imaging and immunohistochemistry. Here we describe a specific and precise approach for correlating histological features and pharmacokinetic properties of drugs at microscopic level, which will provide information for the improvement of drug design, administration formula or treatment schemes.