Rubicon’s Fv-Hsp72 Program
The Problem that Rubicon is Solving: Irreversible Cellular Damage caused by Infarctions, Oxidative Stress and other Acute Assaults.
In heart attacks or strokes, the heart or brain is damaged at the cellular level by the hypoxic stress caused by the ischemic event itself and, ironically, by the oxidative stress caused by restoration of blood flow following the commonly used reperfusion procedures, percutaneous coronary intervention (PCI) or thrombolytic therapy. This damage leads to worsening heart function, lower quality of life and increased morbidity and mortality following the event.
Cardiovascular diseases claim more lives than all forms of cancer combined. In the United States, someone has a heart attack every 34 seconds. Every 60 seconds, someone in the United States dies from a heart disease-related event. About 720,000 people in the U.S. suffer heart attacks each year. Of these, 515,000 are a first heart attack and 205,000 happen in people who have already had a heart attack.1
Stroke is the leading cause of serious, long-term disability in the United States. Each year, approximately 795,000 people suffer a stroke. About 600,000 of these are first attacks, and 185,000 are recurrent attacks. Strokes can and do occur at ANY age. Nearly one fourth of strokes occur in people under the age of 65.2
Inhalation of toxic gas, whether by industrial accident or terrorism, is a major concern in the US. In 2003 the EPA identified over a hundred chemical plants in the US where a terrorist attack or accident could potentially expose more than a million people to a cloud of toxic gas. In addition, there are limited options to treat our soldiers in the field if they were exposed to such an attack.3
Traumatic brain injury (TBI) is a leading cause of morbidity and mortality. At last estimate, 2 million new cases of TBI occur every year in the US, of which 70,000-90,000 victims suffer long term disability and another 50,000 succumb to their injuries. From the year 2000 through the 3rd quarter of 2013, all four branches of the armed services reported 287,911 cases of TBI.4
- United States Government Accounting Office. Homeland security. Washington, DC: GAO-03-24R; 2003
Rubicon’s Solution: Fv-Hsp72 will target and deliver heat shock protein 72 (Hsp72) in therapeutic quantities directly into damaged cells to prevent apoptosis (programmed cell death following cellular injury).
Fv-Hsp72 is a fusion protein created by Dr. Richard Weisbart and Dr. Robert Nishimura at UCLA. The Fv moiety is an antibody fragment that specifically targets the endogenous DNA that is released from cells. The Hsp72 is a “heat shock protein” which helps with the proper folding of newly synthesized proteins within the cell. However, Hsp72 has multiple other roles including, during cell stress, it binds to critical proteins that are damaged and become misfolded. Hsp72 binds to these critical proteins and protects them from aggregation and cellular destruction, thereby inhibiting these processes. Hsp72 also has a role binding and inhibiting the activities of several key proteins involved in multiple apoptotic pathways; hence, the increased presence of this protein in a dying cell may rescue its viability.
The protective effects of endogenously produced Hsp72 are well known. Because it takes more than three hours for damaged cells to initiate production of the endogenous protein, and because peak production does not occur up to 72 hours later, nature’s own response to the heart attack or stroke is too slow to effectively prevent cell damage. Following a myocardial or cerebral infarction, time is of the essence, as cell damage begins immediately. Our technology will deliver therapeutic amounts of Hsp72 directly into the stressed and damaged cells immediately upon administration. Our NIH supported studies, executed at Mount Sinai Medical Center in NYC, have proven that Fv-Hsp72 administration will preserve ischemic myocardium in a rabbit model of left coronary artery ischemia-reperfusion injury.
Fv-Hsp70 Mechanism of Action
There are abundant exogenous pools of DNA (1) in areas of cell damage following a myocardial infarction or stroke. Fv-Hsp70 binds to this DNA (2) and is transported into stressed cells through the ENT2 channel (3) and into the interior of the damaged cell. Once internalized in the cell (4), the Hsp72 then carries out cell salvage activities by binding to critical proteins that are misfolded or to proteins involved in apoptosis and helps the cell avoid death.
Fv-Hsp72 Data Summary
Rubicon completed a comprehensive animal efficacy study at Mount Sinai Medical Center in which a heart attack was experimentally induced in rabbits by surgically ligating, or tying off, the left coronary artery, thereby causing a complete occlusion. This type of heart attack in humans is often fatal, often called a “widow maker.” The ligature was removed from the left coronary artery after 40 minutes, restoring blood flow after the heart attack was induced by the hypoxic event. Myocardial damage following release of the ligature parallels reperfusion injury in humans which occurs after relieving the occlusion with percutaneous coronary intervention and stent placement. After the experimental heart attack and reperfusion was induced in thirty test animals, they were divided into five cohorts of six animals each and were treated either with one of three controls: 1) saline, 2) Fv alone or 3) Hsp72 alone; or they received one of two treatment arms of Fv-Hsp72. Heart attack damage was assessed by three measures. Damage or infarct volume was visualized and quantitated by SPECT imaging. Heart function (left ventricular ejection fraction) was measured by cardiac ultrasound, as performed in humans. And cell death was further measured using a serum biomarker, troponin I, commonly used in the clinic for cardiac patients. Control rabbits receiving either Fv only or Hsp72 only showed no benefit compared to saline treated rabbits.
|ACUTE ISCHEMIC STROKE||
In this published study, (“Recombinant Fv-Hsp70 Protein Mediates Neuroprotection after Focal Cerebral Ischemia in Rats”, Stroke 41 (3): 538-543), focal cerebral ischemia was induced in two cohorts of rats (saline control and Fv-Hsp70 treatment arms) by occluding the middle cerebral artery using the standard intraluminal suture technique. The animals were subjected to 2 hours of focal ischemia by this method. Cerebral tissue began to die immediately following the onset of ischemia (cerebral artery occlusion). Fv-Hsp72 or saline was injected intravenously 15 minutes and 1 hour after release of the occlusion. The infarct volume and sensorimotor function were assessed 24 hours after ischemia.
|TOXIC INHALATION INJURY||
Rubicon was awarded a NIH CounterACT grant to determine if Fv-Hsp72 can protect against inhalation of toxic gases. Rats were exposed to deadly phosgene gas at LD50 (the dose at which 50% of animals die) for 10 minutes. At 30 minutes after phosgene exposure, the rats were injected intravenously with escalating doses of Fv-Hsp72 or saline control and then monitored for survival up to 25 hours post-treatment.
|TRAUMATIC BRAIN INJURY||
Rubicon has already demonstrated that Fv-Hsp72 can traverse the “blood-brain barrier” in our stroke model to reduce the infarct volume and improve sensimotor skills. Since there is substantial published evidence that Hsp72 plays a significant role in the attenuation of primary and secondary symptoms that lead to axonal degeneration and cell death, Rubicon intends to test Fv-Hsp72 in a TBI animal model to determine its efficacy, and a research grant application is in preparation.