Radiolabeled Inhibitors of Carbonic Anhydrase IX

DESCRIPTION (provided by applicant): The NCI estimates that in 2008 there will be more than 54,000 new cases of renal cell cancer in the United States and that it will claim the lives of more than 13,000 Americans. Overt metastatic disease is present at th e time of diagnosis in 25% of patients, with a median survival of 10 months, and 25% of all patients with renal cancer will later manifest metastatic disease and ultimately succumb to their cancer. The expression of distinct proteins on the surface of tumo r cells offers the opportunity to diagnose and characterize disease by probing the phenotypic identity and biochemical composition of the tumor. Radioactive molecules that selectively bind to specific tumor cell surface proteins allow the use of noninvasiv e imaging techniques, such as molecular imaging or nuclear medicine, for detecting the presence and quantity of tumor associated proteins, thereby providing vital information related to the diagnosis and extent of disease, prognosis and therapeutic managem ent options. The goal of this proposal is to develop a series of novel techenium-99m (99mTc) based molecular imaging pharmaceuticals that target the cell surface protein, carbonic anhydrase IX (CA-IX) for imaging by single photon emission computed tomograp hy (SPECT). CA-IX is constitutively expressed in 85- 95% of human clear cell renal carcinomas through inactivation of the tumor suppressor, Von-Hippel-Lindau, but neither in normal kidney nor most normal tissues. The constitutive upregulation of CA-IX expr ession offers the opportunity to diagnose and characterize renal cell carcinoma by probing the phenotypic identity of the tumor. The research plan combines high affinity targeting molecules with the conjugation of a chelator for coordination of a diagnosti c or therapeutic radionuclide. Several classes of selective and cell membrane impermeable CA-IX inhibitors have been described in the primary literature representing a foundation for the design of radiotracers. Analogs of CA-IX inhibitors will be synthesiz ed first as non-radiolabeled rhenium complexed molecules and tested to verify binding to CA-IX in biochemical and cellular assays. Compounds demonstrating high affinity binding to CA-IX will then be radiolabeled with 99mTc and examined for cell binding, an d tumor uptake and retention in mice bearing human renal cancer xenografts. As CA-IX is a cell surface protein, the target will be readily accessible, with a straightforward pharmacokinetic analysis. The use of 99mTc will lead to widespread application thr ough kit preparation and the prevalence of SPECT scanners in medical institutions. We believe that the 99m-Tc labeled CA-IX radiotracers could be exploited for the diagnosis, staging, and prognosis of patients with clear cell renal carcinoma. PUBLI C HEALTH RELEVANCE: The NCI estimates that in 2008 there will be more than 54,000 new cases of renal cell cancer in the United States and that it will claim the lives of more than 13,000 Americans. Overt metastatic disease is present at the time of diagnos is in 25% of patients, with a median survival of 10 months, and 25% of all patients with renal cancer will later manifest metastatic disease and ultimately succumb to their cancer. The goal of this proposal is to develop a series of novel imaging pharmaceu ticals targeting carbonic anhydrase IX, a protein constitutively expressed in 85-95% of human clear cell renal carcinomas through inactivation of the tumor suppressor, Von Hippel Lindau, but neither in normal kidney nor most normal tissues, that may be exp loited for the diagnosis, staging, and prognosis of patients with clear cell renal carcinoma.