Research & Development - PAD
About Peripheral Arterial Disease (PAD)
Nearly 24 million people currently suffer from diabetes mellitus, and the prevalence of the disease has been steadily increasing for several years. Patients with diabetes are at a greater risk of developing peripheral artery disease (PAD), a chronic disorder associated with reduced blood flow to the extremities. PAD causes severe pain in the extremities, limits mobility, and in some cases may lead to death. In the US alone, PAD affects some 12-14 million people, and if left untreated will lead to critical limb ischemia with at annual cost of care estimated at $10 billion. The primary cause of the disease is the build up of fatty acids in the blood vessels, or atherosclerosis, that leads to the formation of plaques in the vessels, which in turn block or weaken the vessel walls, ultimately resulting in reduced blood flow to the extremities. Blood clots, diabetes, inflammation, infection and injury can also lead to PAD. The best predictor of the disease is aging; as the population continues to age, the incidence of PAD will continue to increase. Among other risk factors, diabetes may help to explain the recent increase in incidence among younger people.
TV1001SR is a twice-daily orally-dosed slow-release formulation of the FDA-approved therapeutic sodium nitrite. Results from Phase IIa clinical trials support the use of sodium nitrite for the treatment and prevention of peripheral artery disease, and as a non-addictive and cost-effective treatment for diabetic neuropathy.
A Phase IIa clinical trial was carried out with TV1001, the precursor to the slow-release formulation TV1001SR, in patients with PAD. Flow Mediated Dialation (FMD) was tracked as the primary endpoint. FMD, an imaging modality used to assess endothelial function, is highly compromised in patients with PAD. Because the mechanism of action of sodium nitrite increases endothelial function, PAD measured drug effectiveness. Patients were dosed with 40mg or 80mg. While the placebo group’s baseline FMD experienced a continued decline over the 10 week study suggesting worsening vascular function, the diabetic cohort receiving the 80 mg bid dose experienced a significantly greater change in FMD than the placebo and the 40 mg bid dose.
Studies on TV1001SR
In studies conducted in the ischemic hind-limb model of PAD, the following was learned about sodium nitrite as treatment for recovery in tissue damaged by ischemia:
Sodium nitrite therapy preferentially increases blood flow in ischemic tissue. This was demonstrated when sodium nitrite effectively promoted blood flow to the damaged tissue as early as three days after inducing ischemia, while no effects were observed in the normal, undamaged limb.
Sodium nitrite as therapy for ischemic tissue acts through a different mechanism of action than sodium nitrite in its current uses. Sodium nitrite is currently used as therapy for cyanide poisoning and in experimental trials for congestive heart failure, and stroke. In these cases, sodium nitrite is administered as a single acute injection. When sodium nitrite was used as therapy for ischemic tissue in ischemic mouse models, the drug was administered as a chronic low-dose infusion. In contrast to a single, acute injection, which did not have an effect on angiogenesis, a chronic, low-dose infusion of sodium nitrite quickly restored blood flow, angiogenesis, and arteriogenesis to damaged tissue, which is evidence that the altered method of administration had a different mechanism of action.
Delayed sodium nitrite therapy is effective in promoting recovery from pre-existing ischemia. The compound acts by promoting recovery in ischemic tissue, as opposed to preventing injury, as demonstrated by the fact that sodium nitrite was effective in restoring blood flow to damaged tissue when administered five days after the induction of ischemia, far past the point after which tissue damage had occurred.
Phase IIa studies are currently being conducted with the slow-release formulation, TV1001SR, which has shown increased efficacy in animal models for faster and more robust angiogenesis in the ischemic hind-limb model of PAD. Furthermore, sustained release of nitrite resulted in improved cardiac function in the transverse aortic constriction model of heart failure, where bolus release was inactive. Sustained release should increase efficacy in human subjects and reduce side effects by eliminating the high Cmax.
PAD Research Program
- Chronic low dose sodium nitrite therapy quickly restores ischemic tissue blood flow, angiogenesis and arteriogenesis;
- Sodium nitrite therapy preferentially increases blood flow in ischemic tissue;
- Sodium nitrite therapy increases vascular density of ischemic tissue and increases endothelial cell proliferation;
- Delayed sodium nitrite therapy is effective in promoting recovery from pre-existing ischemia.
Wound Healing Research Program
Development of sodium nitrite as treatment for diabetic ulcers and an agent for chronic wound management.
Diabetes represents an extremely large problem in today’s society, affecting approximately 25 million people. There are a large number of complications associated with diabetes, including increased heart disease and stroke caused by the narrowing of blood vessels due to fat deposits, leading to restricted blood flow. When severe, this restricted blood flow can lead to critical limb ischemia (CLI). This in turn can lead to nerve damage, ulcers or foot wounds that won’t heal and potentially, amputation. Indeed, 90% of lower extremity amputations results from non-healing wounds and 17% of diabetic patients will develop a foot ulcer within 3 years.
During diabetes, biologically available NO is greatly reduced resulting in defective blood vessel function and blunted wound healing responses. Recent studies from Dr. Kevil’s laboratory show that nitrite therapy significantly enhances diabetic ischemic hind limb blood flow and enhances wound healing responses.
Images to the left readily demonstrate that diabetic wounds treated with vehicle control remain open and poorly healed 14 days after injury. Conversely, daily nitrite therapy significantly enhances closure of diabetic wounds and restoration of tissue perfusion. These exciting discoveries provide the foundation for our second product, a nitrite agent which shows great potential for the treatment of diabetic ulcers, chronic wound management and many other applications.
Studies in mouse models of diabetic wounds provide evidence that sodium nitrite therapy significantly enhances closure of diabetic wounds and restoration of tissue perfusion.
Diabetic ulcers or foot wounds occur in diabetic patients who develop critical limb ischemia (CLI). 17% of diabetic patients will develop a foot ulcer within 3 years of disease onset, and 90% of lower extremity amputations result from non-healing wounds. Diabetes-induced CLI is mediated by diabetes-induced heart disease or stroke, which leads to narrowing of the blood vessels and severe lack of blood flow to the extremities.
A critical factor in diabetic critical limb ischemia is reduced biologically available NO, which leads to defective blood vessel function and blunted wound healing response. Studies have shown that diabetic wounds treated with vehicle control remain open and poorly healed 14 days after injury, whereas daily nitrite therapy significantly enhances closure of diabetic wounds and restoration of tissue perfusion.
Circulating nitrite levels are found normally in our blood. However, in two recent studies, the levels of circulating nitrite levels were shown to be depressed in patients with cardiovascular disease. In the first study, researchers found a negative correlation between circulating nitrite levels in the plasma and cardiovascular risks factors: patients with an increase in the number of risk factors associated with cardiovascular disease had a correspondingly lower level of circulating nitrite. In the second study, researchers showed that not only did PAD patients and diabetic patients with PAD have a significantly lower level of circulating nitrite than non-PAD patients, but that when these PAD patient groups exercised, no change in circulating nitrite levels were observed, unlike non-PAD patients where exercise induced a 25-30% increase in circulating nitrite levels. While diabetic patients without PAD had a higher level of resting nitrite levels in the blood, like PAD patients, exercise failed to promote the release of nitrite. In a subsequent study, this same research team found that when PAD patients were given a large amount of dietary nitrate, a precursor to nitrate, exercise performance was enhanced. This has important implications in treating PAD patients in that the current standard of care is exercise, to promote blood flow to the affected limb. However, if exercise is not resulting in a release of nitrite, which in turn will limit the amount of nitric oxide made in the limb and the degree of new vascularization, exercise alone may not offer significant benefit. Increasing circulating nitrite levels with TV1001 could alleviate this problem and other cardiovascular problems where circulating nitrite levels are low.
TheraVasc has recently completed a Phase I clinical trial under the direction of Dr. Frank Greenway at the Pennington Biomedical Research Center, a leader in obesity and diabetes research. Dr. Greenway, the Medical Director at Pennington, has substantial experience in conducting clinical trials on obesity on diabetes. A total of 12 diabetic patients were enrolled and received two different formulations of 80 mg of sodium nitrite, an enteric-coated and a non-enteric coated capsule, with a minimum of two weeks between dosing. There were no serious adverse events, with only three of the twelve subjects reporting any adverse events (headache, flushing, feeling of nausea) all of which resolved within an hour, thus demonstrating that the 80 mg dose is well-tolerated in patients. Circulating nitrite levels were measured at Emory Medical School and University of Alabama, Birmingham using two different methodologies. The results were similar between the two. Peak nitrite levels hit the targeted goal of low micromolar circulating concentrations, demonstrating that the 80 mg capsule resulted in the blood levels predicted to achieve therapeutic benefit based on animal studies. Final analysis of the data will soon be released but it appears the drug is safe and well tolerated at the planned 80 mg dose level.
TheraVasc has recently completed an FDA -authorized placebo controlled, double blind clinical trial across 10 sites throughout the US of an investigational drug for peripheral artery disease (PAD). Sodium nitrite has been demonstrated to promote new blood vessel growth, speed up wound healing and prevent tissue necrosis in animals. In addition to safety, since patients with PAD experience many of these problems, this study sought to determine whether this drug, when given orally, could provide the same benefits to patients with PAD. SG1002 therapy was safe and well tolerated following 10 weeks of twice daily administration. The primary adverse events were headaches and dizziness, which resolved without intervention. PAD subjects with diabetes had a significant improvement in endothelial function and a significant reduction in pain. .
For complete information on this clinical trial, visit ClinicalTrials.gov
Aging Research Program
Development of sodium nitrite as a therapeutic to increase motor and cognitive function while reducing oxidative stress.
Dr. Doug Seals at the University of Colorado has conducted an NIH – supported study investigating the effects of TV1001sr on aging. Using 40 mg TV1001sr and placebo groups, with 34 subjects per group, and the SONIC protocol with little variation, his findings indicated that TV1001sr demonstrated bioactivity through an improvement in FMD, demonstrated a clinical benefit in terms of significant improvement in motor function and cognitive function, and showed a reduction in oxidative stress.