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There are many sources of analytical variability in ligand binding assays (LBA). One strategy to reduce variability has been duplicate analyses. With recent advances in LBA technologies, it is conceivable that singlet analysis is possible. We retrospectively evaluated singlet analysis using Gyrolab data. Relative precision of duplicates compared to singlets was evaluated using 60 datasets from toxicokinetic (TK) or pharmacokinetic (PK) studies which contained over 23,000 replicate pairs composed of standards, quality control (QC), and animal samples measured with 23 different bioanalytical assays. The comparison was first done with standard curve and QCs followed by PK parameters (i.e., Cmax and AUC). Statistical analyses were performed on combined duplicate versus singlets using a concordance correlation coefficient (CCC), a measurement used to assess agreement. Variance component analyses were conducted on PK estimates to assess the relative analytical and biological variability. Overall, 97.5% of replicate pairs had a %CV of <11% and 50% of the results had a %CV of ≤1.38%. There was no observable bias in concentration comparing the first replicate with the second (CCC of 0.99746 and accuracy value of 1). The comparison of AUC and Cmax showed no observable difference between singlet and duplicate (CCC for AUC and Cmax >0.99999). Analysis of variance indicated an AUC inter-subject variability 35.3-fold greater than replicate variability and 8.5-fold greater for Cmax. Running replicates from the same sample will not significantly reduce variation or change PK parameters. These analyses indicated the majority of variance was inter-subject and supported the use of a singlet strategy.

The synthesis, biological activity, and pharmacokinetic profile of CCR1 antagonists are described.

We previously described the in vitro characteristics of the potent and selective CCR1 antagonist, CP-481,715. In addition to being selective for CCR1 vs other chemokine receptors, CP-481,715 is also specific for human CCR1 (hCCR1), preventing its evaluation in classical animal models. To address this, we generated mice whereby murine CCR1 was replaced by hCCR1 (knockin) and used these animals to assess the anti-inflammatory properties of CP-481,715. Cells isolated from hCCR1 knockin mice were shown to express hCCR1 and migrate in response to both murine CCR1 and hCCR1 ligands. Furthermore, this migration is inhibited by CP-481,715 at dose levels comparable to those obtained with human cells. In animal models of cell infiltration, CP-481,715 inhibited CCL3-induced neutrophil infiltration into skin or into an air pouch with an ED50 of 0.2 mg/kg. CP-481,715 did not inhibit cell infiltration in wild-type animals expressing murine CCR1. In a more generalized model of inflammation, delayed-type hypersensitivity, CP-481,715 significantly inhibited footpad swelling and decreased the amount of IFN-gamma and IL-2 produced by isolated spleen cells from sensitized animals. It did not, however, induce tolerance to a subsequent challenge. These studies illustrate the utility of hCCR1 knockin animals to assess the activity of human specific CCR1 antagonists; demonstrate the ability of the CCR1 antagonist CP-481,715 to inhibit cell infiltration, inflammation, and Th1 cytokine responses in these animals; and suggest that CP-481,715 may be useful to modulate inflammatory responses in human disease.

The chemokines are a large gene superfamily with critical roles in development and immunity. The chemokine receptor CXCR3 appears to play a major role in the trafficking of activated Th1 lymphocytes. There are at least three major ligands for CXCR3: mig/CXCL9, IP-10/CXCL10 and I-TAC/CXCL11, and of these three ligands, CXCL11 is the least well-characterized. In this study, we have cloned a rat ortholog of CXCL11, evaluated its function, and examined its expression in the Th-1-mediated disease, experimental autoimmune encephalomyelitis (EAE) in the rat. Based on its predicted primary amino-acid sequence, rat I-TAC/CXCL11 was synthesized and shown to induce chemotaxis of activated rat T lymphocytes in vitro and the in vivo migration of T lymphocytes when injected into the skin. I-TAC/CXCL11 expression, as determined by RT-PCR, increased in lymph node and spinal cord tissue collected from rats in which EAE had been actively induced, and in spinal cord tissue from rats in which EAE had been passively induced. The kinetics of expression were similar to that of CXCR3 and IP-10/CXCL10, although expression of both CXCR3 and IP-10/CXCL10 was more intense than that of I-TAC/CXCL11 and increased more rapidly in both lymph nodes and the spinal cord. Only minor levels of expression of the related chemokine mig/CXCL9 were observed. Immunohistochemistry revealed that the major cellular source of I-TAC/CXCL11 in the central nervous system (CNS) during EAE is likely to be the astrocyte. Together, these data indicate that I-TAC/CXCL11 is expressed in the CNS during the clinical phase of EAE. However, the observation that I-TAC/CXCL11 is expressed after receptor expression is detected suggests that it is not essential for the initial migration of CXCR3-bearing cells into the CNS.

The present manuscript details the discovery and early fundamental structure-activity relationship studies involving compound 3, a novel hydroxyethylene peptide isostere derived molecule that provides micromolar inhibition of CCL3 binding to its receptor CCR1. Initial studies established this screening hit as a legitimate lead for further medicinal chemistry optimization.

The synthesis, biological activity, and pharmacokinetic profile of novel CCR1 antagonists are described.

The present manuscript details structure-activity relationship studies of lead structure 1, which led to the discovery of CCR1 antagonists >100-fold more potent than 1.

The chemokines CCL3 and CCL5, as well as their shared receptor CCR1, are believed to play a role in the pathogenesis of several inflammatory diseases including rheumatoid arthritis, multiple sclerosis, and transplant rejection. In this study we describe the pharmacological properties of a novel small molecular weight CCR1 antagonist, CP-481,715 (quinoxaline-2-carboxylic acid [4(R)-carbamoyl-1(S)-(3-fluorobenzyl)-2(S),7-dihydroxy-7-methyloctyl]amide). Radiolabeled binding studies indicate that CP-481,715 binds to human CCR1 with a Kd of 9.2 nm and displaces 125I-labeled CCL3 from CCR1-transfected cells with an IC50 of 74 nm. CP-481,715 lacks intrinsic agonist activity but fully blocks the ability of CCL3 and CCL5 to stimulate receptor signaling (guanosine 5'-O-(thiotriphosphate) incorporation; IC50 = 210 nm), calcium mobilization (IC50 = 71 nm), monocyte chemotaxis (IC50 = 55 nm), and matrix metalloproteinase 9 release (IC50 = 54 nm). CP-481,715 retains activity in human whole blood, inhibiting CCL3-induced CD11b up-regulation and actin polymerization (IC50 = 165 and 57 nm, respectively) on monocytes. Furthermore, it behaves as a competitive and reversible antagonist. CP-481,715 is >100-fold selective for CCR1 as compared with a panel of G-protein-coupled receptors including related chemokine receptors. Evidence for its potential use in human disease is suggested by its ability to inhibit 90% of the monocyte chemotactic activity present in 11/15 rheumatoid arthritis synovial fluid samples. These data illustrate that CP-481,715 is a potent and selective antagonist for CCR1 with therapeutic potential for rheumatoid arthritis and other inflammatory diseases.

CCR2, and its principle ligand MCP-1/CCL2, have been well documented for their ability to induce monocyte infiltration and promote the pathogenesis of rheumatoid arthritis and atherosclerosis. In order to assess additional roles for CCR2, we inserted allogeneic implants into CCR2-/- and MCP-1-/- mice and characterized T cell responses and the regulatory role of CCR2 on MCP-1 expression. The results demonstrate a marked decrease in lymphocyte infiltration in both CCR2-/- and MCP-1-/- animals. In contrast, IL-12 and CTL function were only suppressed in CCR2-/- animals. Further, whereas MCP-1 was only transiently elevated in the inflammatory fluid of WT animals, levels were sustained within the implants (5000pg/ml; >8 days) and serum (243pg/ml) of CCR2-/- mice. Higher levels of MCP-1 were also observed in the culture supernatants of CCR2-/- macrophages as compared to WT cells despite no difference in mRNA levels. Evidence that MCP-1 levels are regulated by receptor binding and internalization was suggested by its rapid decline when added to WT macrophages at 37 degrees C but not 4 degrees C. These studies indicate that CCR2 plays an important role in regulating T cell responses and controlling the level of MCP-1 at inflammatory sites.