Challenges and key considerations of the enhanced permeability and retention effect for nanomedicine drug delivery in oncology.

Enhanced permeability of the tumor vasculature allows macromolecules to enter the tumor interstitial space, whereas the suppressed lymphatic filtration allows them to stay there. This phenomenon, enhanced permeability and retention (EPR), has been the basis of nanotechnology platforms to deliver drugs to tumors. However, progress in developing effective drugs using this approach has been hampered by heterogeneity of EPR effect in different tumors and limited experimental data from patients on effectiveness of this mechanism as related to enhanced drug accumulation. This report summarizes the workshop discussions on key issues of the EPR effect and major gaps that need to be addressed to effectively advance nanoparticle-based drug delivery.

The anti-interleukin-6 antibody siltuximab down-regulates genes implicated in tumorigenesis in prostate cancer patients from a phase I study.

BACKGROUND: Interleukin-6 (IL-6) is associated with prostate cancer morbidity. In several experimental models, IL-6 has been reported to have anti-apoptotic and pro-angiogenic effects. Siltuximab (CNTO 328) is a monoclonal anti-IL-6 antibody which has been successfully applied in several models representing prostate cancer. This study was designed to assess preliminary safety of siltuximab in patients with early prostate cancer. PATIENTS AND METHODS: Twenty patients scheduled to undergo radical prostatectomy received either no drug or siltuximab (6 mg/kg, five patients per group with administration once, two times, and three times prior to surgery). Blood samples were collected for pharmacokinetic and pharmacodynamic analyses. Expression of elements of IL-6 signaling pathways was analyzed in tumor tissue by immunohistochemistry. Gene analysis in tumor specimens was performed with the DASL array. RESULTS: No adverse events related to siltuximab were observed. Patients treated with siltuximab presented with higher levels of proliferation and apoptosis markers. Following a single dose, serum concentrations of siltuximab declined in a biexponential manner. This study revealed a decrease in phosphorylation of Stat3 and p44/p42 mitogen-activated protein kinases. In addition, gene expression analyses indicate down-regulation of genes immediately downstream of the IL-6 signaling pathway and key enzymes of the androgen signaling pathway. CONCLUSIONS: Preliminary safety of siltuximab is favorable. Future studies in which siltuximab could be combined with androgen-deprivation therapy and experimental therapies in advanced prostate cancer are justified.

Positive treatment effects of ustekinumab in psoriasis: analysis of lesional and systemic parameters.

Ustekinumab, a human anti-interleukin (IL)-12/IL-23p40 monoclonal antibody has demonstrated significant efficacy in patients with moderate-to-severe psoriasis. Skin lesion biopsies, cell surface markers on peripheral blood lymphocytes, and ex vivo T-helper (Th)1/Th2 cytokine responses from peripheral blood mononuclear cells (PBMC) from patients receiving ustekinumab 45 or 90 mg, or placebo were evaluated at baseline and week 12. Inflammatory serum protein levels were measured at baseline, week 2 and week 12. At week 12, median epidermal thickness decreased from 312.1 to 132.7 microm, and median levels of cellular proliferation (Ki67) and T-cell infiltration (CD3) decreased by 84.3% and 70.7%, respectively, in the combined ustekinumab group (all P < or = 0.002). Serum levels of tumor necrosis factor (TNF)-alpha, C-C motif ligand 27 (CCL27) and other inflammatory cytokines remained unchanged. Minimal variation in the percentage of T cells expressing cutaneous lymphocyte antigen (CLA) was observed following ustekinumab treatment, with no significant variation in the percentage of cells expressing CD45RA, CD45RO, CD25, human leukocyte antigen-DR (HLA-DR), and C-X-C motif receptor 3 (CXCR3). No apparent effect on the magnitude of Th1/Th2 responses to external stimuli in PBMC was observed following placebo or ustekinumab treatment. Ustekinumab improves histological psoriasis measures, with minimal impact on the systemic immune system.

Pharmacokinetic and pharmacodynamic modeling of an anti-interleukin-6 chimeric monoclonal antibody (siltuximab) in patients with metastatic renal cell carcinoma.

PURPOSE: Interleukin-6 (IL-6) induces tumor growth, invasion, metastasis, and angiogenesis. Siltuximab (CNTO 328) is a chimeric, murine-human monoclonal antibody that specifically binds human IL-6 with high affinity. C-reactive protein (CRP) can be a pharmacodynamic (PD) marker of IL-6 bioactivity. Reductions in CRP may correlate with clinical activity and IL-6 bioactivity. EXPERIMENTAL DESIGN: Starting-dose selection for this study was based on a previous siltuximab study in multiple myeloma patients. Pharmacokinetic (PK)/PD modeling explored the relationship between siltuximab PK and CRP suppression following i.v. siltuximab infusion in a three-part phase I/II study in 68 metastatic renal cell carcinoma patients. Modeling results were then used to simulate and determine which siltuximab dosage regimens would maintain CRP suppression below the lower limit of quantification (4 mg/L). Siltuximab was given at 1, 3, 6, or 12 mg/kg at weeks 1 and 4 and then every 2 weeks for 2 cycles in part 1; at 3 or 6 mg/kg every 3 weeks for 4 cycles in part 2; and at 6 mg/kg every 2 weeks for 6 cycles in part 3. RESULTS: A two-compartment PK model adequately described the serum siltuximab concentration-time data. An inhibitory indirect response PD model examined the relationship between siltuximab concentrations and CRP suppression. PD parameter estimates seemed reliable and physiologically relevant. Simulations showed that 6 mg/kg siltuximab every 2 weeks or 9 mg/kg every 3 weeks would reduce serum CRP to below 4 mg/L. CONCLUSIONS: Using a stepwise design, PK/PD modeling was used to select the dose levels in this study. Furthermore, PK/PD modeling results were used to help select doses to be used in future siltuximab clinical development.

The expression of monocyte chemotactic protein-1 in papillary thyroid carcinoma is correlated with lymph node metastasis and tumor recurrence.

BACKGROUND: Monocyte chemotactic protein-1 (MCP-1) is a chemokine ligand that has been associated with aggressive behavior in breast and prostate cancer. The present study was performed to determine if there is a relationship between the expression of MCP-1 in papillary thyroid carcinoma (PTC) and factors indicative of aggressive behavior in this disease. METHODS: The subjects of this study were 115 patients with PTC. MCP-1 expression was determined using a semiquantitative scoring system for immunohistochemical staining of MCP-1 in resected PTC samples. There were four levels of immunohistochemical staining intensity, and the population of cells that positively stained for MCP-1 was graded at four levels. The scores for the intensity of immunohistochemical staining for MCP-1 and for the percentage of cells that stained for MCP-1 were used to generate a range from 0 to 9 for scoring MCP-1 expression. RESULTS: Positive staining for MCP-1 was observed in the cytoplasm of PTC cells and stroma cells in 79.2% of the specimens. Expression levels of MCP-1 in PTC cells were positively correlated with tumor size (p < 0.05) and lymph node involvement (p < 0.05). In addition, the expression of MCP-1 in PTC cells level was an independent predictive factor for recurrence of PTC in an analysis that included age, sex, tumor size, extrathyroidal infiltration, and lymph node involvement (p < 0.005). CONCLUSIONS: MCP-1 expression in PTC may stimulate the aggressive behavior of this tumor or it may be a marker for aggressive behavior. Previous reports with non-thyroid tumor cells favor the hypothesis that MCP-1 expression promotes aggressive behavior in PTC.

A multicenter, phase II study of infliximab plus gemcitabine in pancreatic cancer cachexia.

To evaluate the safety and efficacy of infliximab administered with gemcitabine to treat cancer cachexia and to explore a functional measure of clinical benefit, investigators involved in this multicenter, phase II, placebo-controlled study randomized 89 patients with stage II-IV pancreatic cancer and cachexia to receive either placebo or 3 mg/ kg or 5 mg/kg of infliximab at weeks 0, 2, and 4 and then every 4 weeks to week 24; patients also received 1,000 mg/m2 of gemcitabine weekly from weeks 0-6 and then for 3 of every 4 weeks until their disease progressed. The primary endpoint was change in lean body mass (LBM) at 8 weeks from baseline; major secondary endpoints included overall survival, progression-free survival, Karnofsky performance status, and 6-minute walk test distance. In addition, quality of life was measured. The mean change in LBM at 8 weeks was +0.4 kg for patients receiving placebo, +0.3 kg for those receiving 3 mg/kg of infliximab, and +1.7 kg for those receiving 5 mg/kg of infliximab. No statistically significant differences in LBM or secondary endpoints were observed among the groups. Safety findings were similar in all groups. Adding infliximab to gemcitabine to treat cachexia in advanced pancreatic cancer patients was not associated with statistically significant differences in safety or efficacy when compared with placebo.

Alpha-v integrins as therapeutic targets in oncology.

Integrins are heterodimeric cell adhesion receptors that mediate intercellular communication through cell-extracellular matrix interactions and cell-cell interactions. Integrins have been demonstrated to play a direct role in cancer progression, specifically in tumor cell survival, tumor angiogenesis, and metastasis. Therefore, agents targeted against integrin function have potential as effective anticancer therapies. Numerous anti-integrin agents, including monoclonal antibodies and small-molecule inhibitors, are in clinical development for the treatment of solid and hematologic tumors. This review focuses on the role of alpha(v) integrins in cancer progression, the current status of integrin-targeted agents in development, and strategies for the clinical development of anti-integrin therapies.

Modulation of CLA, IL-12R, CD40L, and IL-2Ralpha expression and inhibition of IL-12- and IL-23-induced cytokine secretion by CNTO 1275.

Cytokines interleukin (IL)-12 and IL-23 are implicated in the pathogenesis of psoriasis. IL-12 causes differentiation of CD4+ T cells to interferon-gamma (IFN-gamma)-producing T helper 1 (Th1) cells, while IL-23 induces differentiation to IL-17-producing pathogenic Th17 cells. The effects of the monoclonal antibody to IL-12/23 p40 subunit (CNTO 1275) on IL-12 receptor (IL-12R) expression, markers associated with skin homing, activation, and cytokine secretion were investigated in vitro using human peripheral blood mononuclear cells (PBMCs) from healthy donors. PBMCs were activated in the presence or absence of recombinant human (rh) IL-12 or rhIL-23, with or without CNTO 1275. CNTO 1275 inhibited upregulation of CLA, IL-12R, IL-2Ralpha and CD40L expression and also inhibited IL-12- and IL-23-induced IFN-gamma, IL-17A, tumor necrosis factor (TNF)-alpha, IL-2, and IL-10 secretion. Thus, the therapeutic effect of CNTO 1275 may be attributed to the IL-12/23 neutralization, resulting in decreased expression of skin homing and activation markers, and IL-12- and IL-23-induced cytokine secretion.

Phase I evaluation of a fully human anti-alphav integrin monoclonal antibody (CNTO 95) in patients with advanced solid tumors.

PURPOSE: A fully human monoclonal antibody to anti-alpha(v) integrins (CNTO 95) has been shown to inhibit angiogenesis and tumor growth in preclinical studies. We assessed the safety and pharmacokinetics of CNTO 95 in patients with advanced refractory solid tumors. EXPERIMENTAL DESIGN: In this phase I trial, CNTO 95 (0.1, 0.3, 1.0, 3.0, and 10.0 mg/kg) was infused on days 0, 28, 35, and 42, and clinical assessments, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), and [(18)F]-2-fluorodeoxyglucose positron emission tomography (FDG-PET) were done. Patients achieving stable disease or better were eligible for extended dosing every 3 weeks for up to 12 months. RESULTS: Among the 24 enrolled patients, CNTO 95 was associated with one episode of grade III and four episodes of grade II infusion-related fever (all responded to acetaminophen). Of the six patients who received extended dosing, one patient (10.0 mg/kg), with cutaneous angiosarcoma, had a 9-month partial response. Pre- and post-treatment lesion biopsies confirmed tumor cell alpha(v) integrin expression, as well as CNTO 95 penetration of the tumor and localization to tumor cells in association with reduced bcl-2 expression. A lesion in one patient (10.0 mg/kg) with stable ovarian carcinosarcoma was no longer detectable by FDG-PET by day 49. Exposure to CNTO 95 seemed to increase in a greater-than-dose-proportional manner; dose-dependent mean half-life ranged from 0.26 to 6.7 days. CONCLUSIONS: CNTO 95 was generally well tolerated. Six patients received extended therapy, including one patient with a prolonged response. Biopsy data confirmed tumor localization and pharmacodynamic activity.

Multiplexed cytokine sandwich immunoassays: clinical applications.

Flow cytometric, microsphere-based immunoassays have been developed for the simultaneous detection of soluble analytes in a variety of sample types. The ability to discriminate between individual microspheres on the basis of size, fluorescent intensity, and/or wavelength has allowed the simultaneous analysis of multiple analytes from the same sample. Cytokines are particularly good candidates for multiplexed analysis. Through intricate networks and complex feedback mechanisms, cytokines modulate each other as well as a multitude of cellular events and play an important role in health and disease. The simultaneous measurement of multiple cytokines in a single biological sample has tremendous potential value to further our understanding of the role of these immunomodulators in health and disease. This chapter describes a multiplexed, microsphere-based flow cytometric method to quantitate and compare multiple cytokines simultaneously in human serum. Serum poses a challenge for multiplexed cytokine analysis owing to the presence of numerous proteins and other potentially interfering factors. Assessment of the "real world" performance of the multiplexed, microsphere-based flow cytometry assay with clinically relevant sample types is critical for determining the proper application of these methods in deciphering the role of cytokines in disease pathogenesis and for evaluating drug action.

Co-expression of IL-12 receptors along with CXCR3 and CD25 on activated peripheral blood T lymphocytes.

IL-12 receptors (IL-12R) play a critical role in maintaining IL-12 regulation of T helper-1 (Th1) type immune responses. We studied the expression of two IL-12R, beta1 and beta2 on peripheral blood mononuclear cells (PBMCs) from normal donors, stimulated with polyclonal activators in the presence or absence of exogenous rhIL-12. Unstimulated peripheral blood T lymphocytes (PBTs) expressed moderate levels of IL-12Rbeta1 and very low to undetectable levels of IL-12Rbeta2. Superantigens and anti-CD3+anti-CD28 induced higher expression of both IL-12R on PBTs than PHA-P stimulation. Exogenous rhIL-12 further enhanced the PHA-P or anti-CD3+anti-CD28 induced IL-12Rbeta2 expression. Only a fraction of mitogen activated IL-12Rbeta1+ or beta2+ T lymphocytes co-expressed CD25 (with further enhancement by exogenous rhIL-12), while a higher percentage of these cells were CXCR3+. The majority of superantigen or anti-CD3+anti-CD28-induced IL-12R+ PBTs were positive for both CD25 and CXCR3 markers. Our results indicated differential induction of IL-12R expression that correlated with up regulation of CD25 and CXCR3 expression on activated PBTs and provide a useful insight for monitoring these markers during treatment of Th1 type inflammatory diseases.

Cutaneous lymphocyte antigen expression on activated lymphocytes and its association with IL-12R (beta1 and beta2), IL-2Ralpha, and CXCR3.

The majority of T lymphocytes that infiltrate psoriatic lesions express cutaneous lymphocyte antigen (CLA), a skin homing receptor involved in the influx of memory T cells to cutaneous sites. We investigated CLA expression on normal human peripheral blood mononuclear cells (PBMCs) and evaluated its association with IL-12 receptors, chemokine receptor, CXCR3, and IL-2Ralpha. PBMCs were stimulated in vitro with or without polyclonal activators (mitogen, or superantigens, or anti-CD3+anti-CD28) in the presence or absence of exogenous rhIL-12. The percentage of CLA+ T lymphocytes increased significantly after superantigen stimulation compared to anti-CD3+anti-CD28 or mitogen activation. The majority of activation induced CLA+ T lymphocytes co-expressed IL-12Rbeta1, IL-12Rbeta2, CXCR3, and CD25 in the presence of rhIL-12. Our results indicate that CLA expression on activated T lymphocytes is IL-12 and activation dependent and correlates with the expression of IL-12 receptors, IL-2Ralpha, and CXCR3. Monitoring the levels of Th1 differentiation markers such as CXCR3 and IL-12Rbeta2 along with activation marker, CD25 on skin homing CLA+ T lymphocytes may provide insight into the mechanism of action of immunotherapies directed against Th1 type skin inflammatory diseases.

Correlation of protein and gene expression profiles of inflammatory proteins after endotoxin challenge in human subjects.

Administration of endotoxin (LPS) in humans results in profound physiological responses, including activation of peripheral blood mononuclear cells and the release of inflammatory factors. The time course of the response of selected inflammatory proteins was examined in healthy subjects (n = 6) administered a single intravenous dose of the purified derivative of endotoxin (3.0 ng/kg). Microarray analysis demonstrated changes in the expression of a number of genes, which were confirmed in separate in vitro endotoxin stimulation experiments. Subsequent TaqMan analysis of genes of interest indicated time-dependent changes in the expression of many of these genes. This included pre-B cell enhancing factor, which was identified on microarray analysis as being markedly upregulated following endotoxin stimulation. Protein expression of the genes examined by TaqMan analysis was measured and demonstrated the appearance of tumor necrosis factor (TNF)-alpha and sTNF-R proteins in the plasma beginning within 1 h after dosing, followed by other cytokines/ inflammatory markers (e.g., IL-1ra, G-CSF, IL-6, IL-8, and IL-10) and suppressors of cytokine signaling (SOCS-1 and SOCS-3). In general, cytokine protein expression correlated well with gene expression; however, the temporal profile of expression of some genes did not correlate well with the protein data. For many of these proteins, the lack of correlation was attributable to alternate tissue sources, which were demonstrated on TaqMan analysis. Principal component analysis indicated that cytokines could be grouped according to their temporal pattern of response, with most transcript levels returning to baseline 24 h following endotoxin administration. The combination of cDNA microarray and TaqMan analysis to identify and quantify changes in gene expression, along with the analysis of protein expression, can be useful in investigating inflammatory and other diseases.

Reviews Preclinical Safety and Immune-Modulating Effects of Therapeutic Monoclonal Antibodies to Interleukin-6 and Tumor Necrosis Factor-alpha in Cynomolgus Macaques.

Inhibitors of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) have been shown to be efficacious in a number of autoimmune diseases. In this study, the safety of long-term administration of anti-TNF-alpha and anti-IL-6 monoclonal antibodies (mAbs) was evaluated in cynomolgus macaques. Effects on the immune system were evaluated by analysis of lymphocyte subsets and histopathology of lymphoid tissues. To evaluate the functioning of the immune system, the ability of mAb-treated monkeys to mount a humoral immune response (IgG and IgM) to keyhole limpet hemocyanin (KLH) was evaluated. Treatment with the anti-TNF-alpha mAb produced no histopathological changes in any of the lymphoid tissues examined. There was a small (< 2-fold) elevation in circulating T-and B-lymphocytes during anti-TNF-alpha mAb treatment that was not considered to be toxicologically significant. The antibody response to KLH was unaffected by anti-TNF-alpha mAb treatment. Treatment with anti-IL-6 mAb resulted in a decrease in the size of germinal centers in the spleens of a minority of the animals and a modest but significant decrease in the IgG antibody response to KLH. Weekly intravenous treatment with the anti-IL-6 mAb and twice-weekly subcutaneous treatment with the anti-TNF-alpha mAb for up to 6 months was not associated with any signs of toxicity, and no animal developed an infection throughout the study period. This study demonstrates that the anti-IL-6 and anti-TNF-alpha mAbs produce specific modulating effects on the immune system without rendering the animals immune compromised.

Comparative analysis of lymphocyte activation marker expression and cytokine secretion profile in stimulated human peripheral blood mononuclear cell cultures: an in vitro model to monitor cellular immune function.

Activation of lymphocytes is a complex, yet finely regulated cascade of events that results in the expression of cytokine receptors, production and secretion of cytokines and expression of several cell surface molecules that eventually lead to divergent immune responses. Assessing the qualitative and quantitative nature of lymphocyte function following immunotherapy provides valuable information about the immune responses mediated by a therapeutic agent. To facilitate evaluation of the immunomodulatory activity of therapeutic agents, we have established a platform of in vitro immunoassays with normal human peripheral blood mononuclear cells (PBMCs) treated with several polyclonal activators that are known to exhibit different modes of action. We evaluated the kinetics of cell surface marker expression and cytokine release from PBMCs stimulated in parallel with various activating agents over a time course. These stimulating agents induced early (CD69 and CD71) and late (CD25 and HLA-DR) activation markers to varying antigen densities, indicated different cytokine profiles, and showed differential inhibition with dexamethasone (DEX), an inhibitor of early signaling events. Based on the association or correlation of the kinetics of activation marker expression and secreted cytokines, the results of our study indicate the appropriate time points for the simultaneous measurement of both these activation products. This study defines the kinetics for both measures of T cell activation and provides a comprehensive review with various polyclonal activators that can serve as a reference for monitoring lymphocyte function in clinical study samples.

A pilot study on safety and pharmacokinetics of infliximab for the cancer anorexia/weight loss syndrome in non-small-cell lung cancer patients.

BACKGROUND: Weight loss predicts a poor prognosis for patients with non-small-cell lung cancer. Tumor necrosis factor alpha (TNFalpha) is a mediator of this weight loss, yet no studies have tested infliximab, an IgG monoclonal antibody that blocks the binding of TNFalpha to its p55 and p75 receptors, for this indication. The safety and pharmacokinetics of infliximab in combination with docetaxel, a commonly used chemotherapy agent for non-small-cell lung cancer, were explored in this pilot study. METHODS/RESULTS: Four patients with metastatic non-small-cell lung cancer were treated initially with infliximab 5 mg/kg per day intravenously once a week on weeks 1, 3 and 5, and docetaxel 36 mg/m2 per day intravenously once a week on weeks 1, 2, 3, 4, 5 and 6 of an 8-week treatment cycle. Therapy was well tolerated with no grade 4 or 5 adverse events. Maximal serum concentrations of infliximab at 1, 3 and 5 weeks were (mean+/-SD) 108+/-11, 135+/-19, and 139+/-6 microg/ml, respectively, and appeared similar to historical concentrations from non-cancer patients not receiving concomitant chemotherapy (144+/-68 microg/ml). One patient manifested weight stability. One patient manifested a partial tumor response, one stable disease, and two disease progression. Median survival within the cohort was 203 days (range 111 to 324 days). CONCLUSIONS: The above combination appears safe, and docetaxel does not appear to increase serum concentrations of infliximab. A larger study testing the role of this combination for weight loss in non-small-cell lung cancer patients is ongoing and utilizes the doses described above.

Validation and comparative analysis of a multiplexed assay for the simultaneous quantitative measurement of Th1/Th2 cytokines in human serum and human peripheral blood mononuclear cell culture supernatants.

There is increasing evidence suggesting a relationship between cytokine levels and disease pathogenesis, which has led to interest in analyzing multiple cytokines in biological fluids and culture supernatants for various research and clinical studies. The introduction of methodologies allowing simultaneous measurement of interrelated biomarkers/cytokines has further revolutionized this process. In contrast to tissue culture supernatant, the measurement of cytokines in serum has proven to be difficult to characterize in multiplexed formats because of the presence of large dynamic concentration ranges of proteins and other interfering factors that are present in this matrix. In the present study, we have used the microsphere-based multiplex method to simultaneously quantitate and compare six analytes, encompassing a representation of the Th1/Th2 cytokine panel (interleukin (IL)-2, IL-4, IL-5, interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), and IL-10), in both serum and culture supernatants from peripheral blood mononuclear cells (PBMCs). A detailed validation procedure for these determinations is described along with a comparative analysis of the performance of the multiplexed assay in serum and culture supernatant matrices. Our results indicate that precision of the multiplexed assay is comparable in both culture supernatant and serum. However, the accuracy of quantification of cytokines in the serum matrix but not in culture supernatant may be compromised depending upon the cytokine being analyzed. Therefore, one must use caution when interpreting data from such complex matrices. Nevertheless, this assay format is appropriate to profile cytokines in clinical trial samples.

Simultaneous quantification of proinflammatory cytokines in human plasma using the LabMAP assay.

There is an emerging trend in the pharmaceutical industry to evaluate a variety of surrogate biomarkers in Phase I/II clinical studies with the intention of determining potential activity of drugs early in clinical development. A number of cytokines expressed in pathological conditions are currently being considered as potential surrogates of disease and/or drug activity. The quantitative measurement of such analytes (biomarkers) in biological fluids has traditionally been performed by bioassays, enzyme-linked immunosorbent assay (ELISA), ribonuclease protection assay (RPA) and polymerase chain reaction (PCR). Typically, these methods have been limited to the measurement of a single analyte, require large sample volume and are time and cost involved. The LabMAP (Luminex) system has been previously used to quantify cytokines in tissue culture supernatants and in animal serum. In the present study, the LabMAP technology was used for quantifying for the first time, pro-inflammatory cytokines such as, tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1beta), IL-6 and IL-8 levels in lipopolysaccharide (LPS)-stimulated human plasma samples. Both single-cytokine and two-cytokine (biplexed) panel formats were evaluated and the performance in the two formats was compared. A detailed validation procedure for these determinations is described along with a side-by-side comparison with ELISA results. Our results indicate that the LabMAP system can be used to measure cytokine levels in LPS-stimulated human plasma samples and that the levels obtained by this technique are comparable with ELISA results. It is therefore feasible to use this optimized technology to detect and quantify cytokines and other potential biomarkers in a complex milieu such as human plasma in support of clinical studies.