In vitro and in vivo pharmacology and pharmacokinetics of a human engineered monoclonal antibody to epithelial cell adhesion molecule.

ING-1(heMAb), a Human Engineered monoclonal antibody to epithelial cell adhesion molecule (Ep-CAM), was evaluated for its in vitro and in vivo activity. The dissociation constant of ING-1(heMAb) for binding to Ep-CAM on HT-29 human colon tumor cells was 2 to 5 nM, similar to chimeric ING-1. In antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity assays, ING-1(heMAb) caused a concentration-dependent lysis of BT-20 breast, MCF-7 breast, HT-29 colon, and CACO-2 colon tumor cells, with maximum cytolysis at approximately 1 microg/ml. After an intravenous injection in rats, plasma ING-1(heMAb) levels declined with an alpha half-life of 8 to 11 hours, and a beta half-life of 20 days, typical of an IgG in a species without the target for ING-1. In nude mice with human HT-29 colon tumors, plasma ING-1(heMAb) levels declined more rapidly than in non-tumor-bearing mice, suggesting an enhanced clearance via the tumor-associated human Ep-CAM. In nude mice, intravenous treatments with ING-1(heMAb) twice a week for 3 weeks significantly suppressed the growth of human HT-29 colon and PC-3 prostate tumors in a dose-dependent manner, with 1.0 mg/kg providing the greatest benefit. These results indicate that Human Engineered ING-1(heMAb) is a high-affinity antibody with potent in vitro activity that targets and suppresses the growth of human tumors in vivo.

Adhesion molecules as therapeutic targets for autoimmune diseases and transplant rejection.

Inflammatory disorders such as autoimmune diseases and graft rejection are mediated by activated leukocytes, particularly T lymphocytes, which penetrate the inflamed tissue and perpetuate or amplify the immune reaction. In an unstimulated state, leukocytes do not readily adhere to the vascular endothelium. However, inflammatory signals induce the expression of proteins on the endothelial cell surface that promote the adhesion and extravasation of activated immune cells from the circulation into the underlying tissues. Key among these molecules are P- and E-selectin, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) on the endothelial cells, and their respective counter receptors, P-selectin glycoprotein ligand-1 (PSGL-1), leukocyte function-associated antigen-1 (LFA-1) and very late antigen-4 (VLA-4), on the leukocytes. In vitro blockade of these molecules inhibits the adhesion of leukocytes. In many cases there is attenuation of leukocyte activation as well. Adhesion blockade in animal models prevents or ameliorates graft rejection and disease severity in autoimmune models. Clinical studies with humanised monoclonal antibodies which interfere with LFA-1/ICAM-1 or VLA-4/VCAM-1 interactions have shown significant efficacy and good safety profiles in autoimmune disease, including psoriasis, multiple sclerosis and inflammatory bowel disease. Thus, adhesion blockade is emerging as a useful therapeutic strategy in several inflammatory settings.

Anti-adhesion antibodies efalizumab, a humanized anti-CD11a monoclonal antibody.

The acquired immune response that leads to graft rejection depends on regulated adhesive interactions between T lymphocytes, endothelial cells, dendritic cells, graft tissue and the extracellular matrix to coordinate cellular trafficking and activation of antigen-reactive T lymphocytes. Inhibiting the function of molecules involved in the adhesion processes offers the potential for interfering with the allograft response. The leukocyte function associated antigen-1 molecule (LFA-1), a heterodimer of CD11a (alphaL) and CD18 (beta2) integrin subunits, is an attractive therapeutic target because it plays an important role in key steps of inflammation and tissue rejection. These include: (1) binding of leukocytes to endothelium; (2) trafficking through activated endothelium; and (3) costimulatory interactions between T lymphocytes and antigen presenting cells. Clinical experience with efalizumab, a humanized anti-CD11a monoclonal antibody (mAb), in patients with chronic plaque psoriasis has shown that anti-CD11a therapy is well tolerated and effective at reducing the severity of the disease without depleting lymphocytes. Initial results in renal transplant patients are also promising.

Understanding gene expression patterns in immune-mediated disorders.

Gene expression profiling of peripheral blood cells can provide dynamic information regarding the host response to immune-mediated disorders. AlloMap molecular expression testing from XDx monitors the expression of 20 genes in peripheral blood mononuclear cells (PBMC) to discriminate cardiac allograft recipients of 15 years or greater who are at low risk for acute cellular rejection (ACR). The AlloMap test classifier is based on the expression level of 11 genes, encoding proteins with diverse functions, which are differentially expressed in stable patients with moderate to severe ACR compared to patients without ACR. The nine other test genes are used for normalizing gene expression levels and assuring sample quality. In this work we review the development processes leading to the selection of the 11 informative genes and the derivation of the AlloMap test classifier, and discuss the relationship of peripheral blood gene expression with diverse pathways associated with ACR, including T-cell priming, platelet activation, systemic responses to allograft inflammation, and the overall state of immunosuppression.

Pharmacokinetic-pharmacodynamic-efficacy analysis of efalizumab in patients with moderate to severe psoriasis.

PURPOSE: Efalizumab is a humanized anti-CD11a monoclonal antibody that demonstrated efficacy in the treatment of patients with psoriasis. The objective of this study was to perform a pharmacokinetic (PK)-pharmacodynamic (PD)-efficacy (E) modeling analysis with intersubject variability assessment to increase our understanding of the interaction of efalizumab with CD11a on T cells and consequent reduction in severity of disease in psoriasis patients. METHODS: A total of 6,329 samples from 240 patients in five Phase I and II clinical studies were used in the analysis. For the analysis, plasma efalizumab concentration was used as the PK measurement, the percent of predose CD11a was used as the PD measurement, and the psoriasis area and severity index was used as the measure of efficacy. A receptor-mediated PK/PD model was developed that describes the dynamic interaction of efalizumab binding with CD11a. In the efficacy model, the rate of psoriasis skin production is directly proportional to the amount of free surface CD11a on T cells, which is offset by the rate of skin healing. An additional CD11a-independent component to psoriasis skin production accounted for incomplete response to efalizumab therapy. A Monte Carlo parametric expectation maximization method implemented in the ADAPT II program was used to obtain the estimate of population parameters and inter- and intrasubject variability. RESULTS AND CONCLUSIONS: The final model described the PK/PD/E data in psoriasis patients reasonably well. In addition, simulations using the final model suggested that efalizumab administered less frequently could possibly be more convenient with similar efficacy.