Targeted thrombosis

#The present invention relates to the fields of blood coagulation, thrombosis, tumor angiogenesis, and cancer therapy. The present invention provides various compositions and methods to treat solid tumors by inducing site-selective thrombosis in tumor blood vessels.

#Although many advances in cancer therapy have been made during the last thirty years, many prevalent forms of human cancer currently resist chemotherapeutic intervention. For example, prostate cancer is the second leading cause of cancer death in men. The incidence of prostate cancer has increased 141.8% between 1973 and 1994. In 1998, new prostate cancer cases totaled 184,500, representing about one new case every three minutes, and 29% of all new cancer cases in American men. In 1998, an estimated 39,200 men died of prostate cancer. A life is lost to prostate cancer in this country every 13 minutes. According to the National Cancer Institute, the annual cost of prostate cancer to the country, including medical care, lost wages and lost productivity, may be as high as $15 billion.

#Certain types of tumors are more amenable to therapy than others because they are more accessible to therapeutic agents. For example, soft tissue tumors such as lymphomas, and tumors of the blood and blood-forming organs such as leukemia, have generally been more responsive to chemotherapeutic therapy than have solid tumors such as carcinomas. One reason for the susceptibility of soft and blood-based tumors to chemotherapy is that they are physically more accessible to chemotherapeutic intervention. It is simply more difficult for most chemotherapeutic agents to reach all of the cells of a solid tumor mass than it is for such agents to reach the cells of soft tumors and blood-based tumors. While it is possible to increase dosages, chemotherapeutic agents are toxic at higher doses. Hence, conventional anti-tumor agents generally have a limited range of effectiveness against solid tumors and a need exists for the development of novel strategies for the treatment of solid tumors.

#FIG. 1A provides a structural model of the ternary complex of Tissue Factor (blue molecule in the middle that projects through the cell membrane) with Factor VIIa (red molecule to the left) and Factor X (yellow molecule to the right that extends down to become) associated with a cell surface. The transmembrane domain of native Tissue Factor spans the cell membrane and ensures proper positioning of both Factor VIIa and Factor X (or Factor IX) on the cell surface. The interaction of the N-terminal Gla domain of both Factor VIIa and Factor X with the cell membrane is critical for the full thrombogenic activity of this complex.

#FIG. 1B shows a structural model of a ternary complex of a Tissue-Selective Vascular Thrombogen of the invention where the Tissue Factor polypeptide (in the middle) is associated with Factor VIIa (on the left) and Factor X (on the right). The N-terminal extracellular domain of Tissue Factor is fused with a Selective Binding Domain (arrow in the upper left comer of the right panel (FIG. 1B)) to form a novel Tissue-Selective Vascular Thrombogen. The extreme portion of the N-terminus of Tissue Factor is not involved in its function. Hence, addition to the N-terminus of a Tissue Factor polypeptide of another molecule or domain is possible. In this invention, a Selective Binding Domain can be added to properly associate and physically align the Tissue Factor polypeptide with the cell surface. Attachment of such a Selective Binding Domain to its N-terminus does not adversely affect the conformation or the function of the selected Tissue Factor polypeptide. Factor VII, or its activated form, Factor VIIa, and Factor X, or Factor IX, can therefore interact with the Tissue Factor domain when aligned on a functionally supportive region of an anionic cell surface. Such interaction permits formation of a complex that has a conformation very similar to the structure of a native Tissue Factor:Factor VIIa:Factor Xa complex. The thrombogenic activity of this complex is substantially unaffected by the incorporated Selective Binding Domain.

#FIG. 2A is a silver-stained SDS polyacrylamide gel of an electrophoretically purified fibronectin-Tissue Factor (Fn-TF) construct (lane 1) and a polypeptide encoding the extracellular domain of Tissue Factor (TF1-218) (lane 2). Only a single band was observed for each sample, indicative of the homogeneity and the purity of each protein preparation.

#The present invention provides new compositions and methods for targeted thrombosis at selected vascular sites within an animal, for example, within tumors. Such targeted thrombosis is achieved by administering novel Tissue-Selective Vascular Thrombogens and compositions thereof. Such Tissue-Selective Vascular Thrombogens contain at least two domains. The first domain comprises a coagulation-activating Tissue Factor polypeptide. The second domain is a Selective Binding Domain. The Selective Binding Domain can recognize and bind to a selected cell type, for example, a specific tumor cell type. More than one Tissue Factor polypeptide and/or more than one Selective Binding Domain can be included in the Tissue-Selective Vascular Thrombogens of the invention.

#Other domains can be incorporated into the Tissue-Selective Vascular Thrombogens of the invention. Such additional domains can be used, for example, to help spatially orient one or more of the other domains, to add additional Selective Binding Domains, to facilitate insertion of the Tissue-Selective Vascular Thrombogen into a cell membrane, to orient the Tissue-Selective Vascular Thrombogen with the cell surface or to enhance, or prevent neutralization of, the activity of the Tissue-Selective Vascular Thrombogen.

#These compositions and methods can be used to activate the thrombogenic cascade in the tumor blood vessels, thereby blocking blood flow to the tumor and killing tumor cells within the tumor. The present invention provides that such compositions may be administered alone, in combination with conventional chemotherapeutics, in combination with Factor VIIa or other factors involved in the cascade of events leading to localized thrombogenesis.