VistaGen Therapeutics Presents Highlights of CardioSafe 3D™
VistaGen Therapeutics, Inc. has announced a poster presentation of its research and development activities leading to validation of its human stem cell-derived "Micro-Heart" cardiotoxicity bioassay system, CardioSafe 3D™, at the fourth Symposium on Cardiovascular Regenerative Medicine hosted by the National Institutes of Health's National Heart, Lung and Blood Institute.
The poster was presented by Dr. Ralph Snodgrass, VistaGen's President and Chief Scientific Officer, at the NIH symposium held in Bethesda, Maryland on October 4 - 5, 2011.
The research and development work presented by Dr. Snodgrass underscores the advances VistaGen's versatile pluripotent stem cell technology platform, Human Clinical Trials in a Test Tube™, is driving in the areas of predictive toxicology and drug safety screening.
Screening methods currently employed by the pharmaceutical industry to measure the potential toxicity of drug candidates do not accurately predict the cardiac effects of many new drug candidates.
There is a growing recognition in the field that existing methods suffer from the use of either animal models, which respond differently than humans to many drugs, or cell lines that are engineered, transformed, non-human and/or of non-cardiac lineage and are typically focused on the effects of the drug candidate on a single cardiac ion channel.
These methods yield both false positive and false negative results leading to important implications for patient safety and costly project terminations during clinical development.
Human pluripotent stem cells have the potential to address these limitations by permitting the generation of functional human cardiac cells that express ion channels and auxiliary proteins relevant to the accurate measurement of cardiac function and evaluation of the possibility of long-term cardiac abnormalities.
"Cardiotoxicity has been implicated in almost 30% of drug withdrawals in the United States over the last 30 years," said Dr. Ralph Snodgrass, President and Chief Scientific Officer of VistaGen.
Dr. Snodgrass continued, "Our human stem cell-derived 'Micro-Heart' cardiotoxicity assay, CardioSafe 3D™, will contribute to the efficient and rapid identification of safer drugs before valuable resources are lost developing drug candidates with toxicity issues that are undetected until human clinical trials are in progress or even after FDA approval resulting in withdrawal from the market."
The poster describes work conducted by VistaGen's scientists in collaboration with scientists at ChanTest Corporation in Cleveland, Capsant Neurotechnologies in Southampton (in the UK), and the laboratory of Dr. Gordon Keller at the University Health Network's McEwen Centre for Regenerative Medicine in Toronto.
The research described combines optimized stem cell cardiac differentiation protocols, a novel 3-dimensional culture system, and traditional electrophysiological measurements to assess drug-related safety data.
The system, called a "Micro-Heart" Cardiotoxicity Assay, was validated by measuring the dose-dependent effects on cardiomyocyte cell viability and electrophysiological responses, as measured by patch clamp and field potential assays, of twelve compounds with known cardiac cytotoxicity or electrophysiology effects.
These drugs included Class III antiarrhythmic compounds, mixed ion channel compounds, antihistamines, sodium and calcium channel blockers, as well as antineoplastic agents.
The observed action potential Vmax values of these highly enriched cardiomyocytes was approximately 3-6x higher than values reported in the literature, suggesting a more normal high-level sodium channel density in these cardiomocytes.
Expected dose-dependent effects of typical hERG channel blockers on QT interval were observed, as well as dose-dependent effects of mixed ion channel drugs. In addition, direct dose-dependent drug cytotoxicity could also be measured.
The data described in the poster presentation have demonstrated that VistaGen's human stem cell-derived "Micro-Heart" cardiotoxicity bioassay system is highly reproducible with very strong concordance with the in vivo cardiac effects of multiple classes of compounds.
This work further supports VistaGen's Human Clinical Trials in a Test Tube™ platform by demonstrating its strong applicability for preclinical cardiac safety screening, with greater sensitivity and predictive power than conventional animal models for compounds known to induce lethal arrhythmias.
VistaGen is developing this platform for proprietary applications in drug rescue screening, cell therapy and regenerative medicine, and the validation of its stem cell-derived human cardiac cell-based assays represents another major step forward in demonstrating the clinical relevance and power of the platform.