Cardium Therapeutics: Genvascor Pre-Clinical Development

PRECLINICAL DEVELOPMENT: GENVASCOR

Genvascor, a pre-clinical, DNA-based, endothelial nitric oxide synthase (eNOS) therapeutic is being designed to induce production of nitric oxide directed at mediating the effects of multiple growth factors to enhance neovascularization and increased blood flow for the treatment of patients with critical limb ischemia due to advanced peripheral arterial occlusive disease. The Company may seek to develop additional pre-clinical information through sponsored studies and, if confirmatory, anticipates it will seek to further develop Genvascor through corporate collaboration.

Nitric oxide (NO) plays an important role in angiogenesis by mediating some of the effects of vascular endothelial growth factor (VEGF) and other growth factors and by inhibiting local anti-angiogenic mechanisms (e.g., VEGF receptor down-regulation). In the setting of atherosclerotic arterial disease and the presence of multiple concurrent cardiovascular risk factors, activation of vascular endothelial cells leads to reduced production of endothelial nitric oxide and impaired local angiogenesis. We believe that a treatment that re-establishes a sufficient level of bioavailable nitric oxide can potentially lead to enhanced neovascularization and increased blood flow to an ischemic limb. Based on its multiple vasculoprotective mechanisms, as well as the anti-inflammatory activity that nitric oxide exerts while also stimulating angiogenesis and arteriogenesis, treatment with Genvascor could lead to superior clinical efficacy to relieve peripheral limb ischemia over single growth factor treatments that are currently in development.

Critical limb ischemia due to advanced peripheral arterial occlusive disease (PAOD) is characterized by reduced blood flow and oxygen delivery with exercise or even at rest with severe disease, resulting in claudication (muscle pain) and eventual non-healing skin ulcers that can lead to gangrene. The estimated incidence of critical limb ischemia is 500-1000 per million per year in the United States. Progressive microcirculatory dysfunction and impairment of angiogenesis/arteriogenesis are crucial pathophysiologic determinants of critical limb ischemia. As critical limb ischemia progresses, deregulation of the microcirculation occurs, characterized by activation of white blood cells, platelet aggregation, plugging of capillaries, endothelial damage and release of free radicals, all of which promote further ischemia leading to tissue damage and eventual tissue necrosis. The prognosis of patients with critical limb ischemia is very poor. The survival rate for patients with significant tissue necrosis without major amputation is less than 50% after one year. Many patients presenting with ischemic pain and ulcers are not suitable candidates for surgical revascularization or angioplasty due to diffuse, distal occlusive vascular disease. Current pharmacotherapy has had little impact on limb salvage in patients with advanced critical limb ischemia and, likewise, little symptomatic effect.

Angiogenesis and collateral vessel formation in an extremity are complex processes that require the coordination of multiple factors. Therefore, the potential efficacy of treatments currently under development using a single growth factor may be limited. We believe that the delivery of the gene directed at the production of nitric oxide to mediate the effect of multiple growth factors to induce angiogenesis represents a promising new approach for the treatment of critical limb ischemia. Nitric oxide availability to the tissues can reverse ischemia through multiple mechanisms including stimulating impaired angiogenesis, ameliorating existing microvascular dysfunction, restoring vasomotor (vasodilator) activity of existing vessels and contributing to the remodeling and maturation of existing collateral vessels. This "biology-based" revascularization of ischemic limb tissues could possibly be efficacious for patients who are not amenable to percutaneous or surgical revascularization.

The proprietary endothelial nitric oxide synthase mutant has an increased specific activity of the nitric oxide synthase enzyme, which induces the production of high local levels of nitric oxide. This production is not only independent of the level of endogenous growth factors present, but also is not inhibited by common concurrent risk factors such as hypercholesterolemia or increased oxidative stress, which are known to inhibit the activity of endogenous wildtype eNOS. The properties of this eNOS mutant, Genvascor, may predict a beneficial effect in chronic ischemic conditions. Significant improvement in revascularization and limb salvage has been shown with intramuscular delivery of Genvascor in eNOS-knock-out mouse models of chronic limb ischemia. Efficacy of Genvascor has also been demonstrated in mouse chronic limb ischemia models with reported functional deficiencies in eNOS due to diabetes, the most common cause of PAOD. Treatment with Genvascor therefore has the potential to be efficacious in patients with chronic limb ischemia who also exhibit severe endothelial nitric oxide deficiency, either due to genetic causes or due to metabolic or inflammatory factors. These properties may provide Genvascor a competitive advantage over single growth factor therapies in development as a novel therapy for symptomatic, severe PAOD.