Vical, in collaboration with Merck, is developing gene-based therapies, including its 'naked DNA', for the potential treatment of ischemic heart disease. Vical has obtained preclinical data in animal models showing that a gene for a potent growth factor, FGF-5, can be delivered and expressed in coronary arteries stimulating the formation of new blood vessels. This new blood vessel formation may provide supplemental blood flow and necessary cardiac tissue oxygenation in areas of the heart where atherosclerotic blockages are present. Vical anticipates that its FGF-5 gene-based product would be used in conjunction with balloon angioplasty to stimulate new blood vessel formation at the site of the blockage. A series of experiments have been conducted in rats, whereby genes encoding FGF-5 were injected directly into rat heart muscle. The DNA was absorbed and the FGF-5 protein was expressed by cardiac myocytes. Active FGF-5 was released into the extracellular spaces of the heart muscle cells and new blood vessels formed throughout the local area. Quantitative measurements of blood vessel formation indicated that capillary density increased significantly in the hearts of treated rats compared to untreated controls. Further studies are underway to evaluate the persistence of new blood vessels following FGF-5 gene injection, and measurements will be made to assess the extent of improved blood flow in the affected region [177118]. In December 1996, the US patent office issued patent number US-05580859, covering Vical's naked DNA technology [227199].