RESUMEN
Tissue factor (TF) antagonists targeting the factor VII (FVII) binding domain have been shown to interrupt acute vascular thrombus formation without impairing haemostasis in non-human primates. In this study, we evaluate whether a human/mouse chimeric monoclonal antibody (ALT-836, formerly known as Sunol-cH36) blocking the factor X/factor IX (FX/FIX) binding site of tissue factor could achieve similar clinical benefits in an arterial thrombosis model induced by surgical endarterectomy in chimpanzees. In this model, sequential surgical endarterectomies on right and left superficial femoral arteries were performed 30 days apart in five chimpanzees. A bolus (1 mg/kg) of ALT-836 was injected intravenously immediately preceding the restoration of flow in the endarterectomised femoral artery. Pre-surgical labelling of autologous platelets using (111)In-Oxine and post-surgical gamma camera imaging of (111)In-platelet deposition at endarterectomy sites was performed. The manipulated arterial segments were harvested for patency analysis 30 days following surgery. The results indicate that ALT-836 was highly effective at reducing acute vascular thrombosis, with no significant variations in surgical blood loss and template-bleeding time in the treated group compared to the control animals. These data suggest that ALT-836 is an effective and safe antithrombotic agent in preventing TF-initiated vascular thrombogenesis without compromising haemostasis.
Asunto(s)
Anticuerpos Monoclonales/farmacología , Factor X/metabolismo , Fibrinolíticos/farmacología , Tromboplastina/antagonistas & inhibidores , Trombosis/prevención & control , Animales , Anticuerpos Monoclonales/administración & dosificación , Anticuerpos Monoclonales/efectos adversos , Anticuerpos Monoclonales/genética , Anticuerpos Monoclonales/farmacocinética , Especificidad de Anticuerpos , Sitios de Unión , Coagulación Sanguínea/efectos de los fármacos , Pérdida de Sangre Quirúrgica/prevención & control , Células CHO , Cricetinae , Cricetulus , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Endarterectomía , Factor IX/metabolismo , Factor VIIa/metabolismo , Femenino , Arteria Femoral/cirugía , Fibrinolíticos/administración & dosificación , Fibrinolíticos/efectos adversos , Fibrinolíticos/farmacocinética , Hemorragia/inducido químicamente , Humanos , Inyecciones Intravenosas , Ratones , Ratones Endogámicos BALB C , Pan troglodytes , Cintigrafía , Proteínas Recombinantes de Fusión/farmacología , Tromboplastina/inmunología , Tromboplastina/metabolismo , Trombosis/sangre , Trombosis/diagnóstico por imagen , Trombosis/etiologíaRESUMEN
Antibody-based targeted immunotherapy has shown promise as an approach to treat cancer. However, many known tumor-associated antigens are not expressed as integral membrane proteins and cannot be utilized as targets for antibody-based therapeutics. In order to expand the limited target range of antibodies, we have constructed a soluble single-chain T-cell receptor (TCR) fusion protein designated 264scTCR/IL-2. This fusion protein is comprised of a three-domain HLA-A2-restricted TCR specific for a peptide epitope of the human p53 tumor suppressor protein, which is overexpressed in a broad range of human malignancies. The 264scTCR/IL-2 fusion protein has been expressed at high levels in mammalian cells, and milligram quantities have been purified. MHC-restricted antigen-specific binding properties are maintained in the single-chain, three-domain TCR portion of the fusion protein, and the IL-2 portion retains bioactivity similar to that of free recombinant IL-2. Moreover, this fusion protein is capable of conjugating target and effector cells, remains intact in the blood and substantially increases the half life of the IL-2 portion of the molecule. Finally, the 264scTCR/IL-2 fusion protein can be used to stain tumor cells and is capable of reducing lung metastases in an experimental model of metastasis. Thus, TCR-based fusion proteins may provide a novel class of targeted immunotherapeutics for cancer.