Development of a Human Hydrolase to Treat Cocaine Abuse and Overdose:Rat Models

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DESCRIPTION (provided by applicant): This competitive revision is submitted in response to Notice Number NOT-OD-09-058, entitled "NIH Announces the Availability of Recovery Act Funds for competitive Revision Applications". The current submission modifies a parent grant concerned with a novel concept for treatment of cocaine abuse that envisages interception of cocaine en route to brain as a means of reducing drug-seeking behavior. The parent grant investigates the potential to accomplish that goal with a powerful cocaine hydrolase (CocH). The revision proposes an expanded effort, with additional personnel, to address the very promising potential that synergistic combinations of hydrolase with anti-cocaine vaccine will dramatically increase the therapeutic power of such a drug-interception strategy. The plan builds on the successful outcome of efforts under the parent grant, which showed that cocaine hydrolase will rescue rats from lethal overdose and prevent reinstatement of cocaine-seeking behavior in a rat model of addiction relapse. It is further supported by our observations that therapeutic levels of CocH can be maintained almost indefinitely in rodents without evidence of harm, using gene transfer with a well-tolerated, new-generation, helper- dependent viral vector. Research with CocH will continue unabated, focusing on the ability of CocH to affect all phases of cocaine abuse, including acquisition, maintenance, extinction, and reinstatement. Efforts will also be continued to optimize methods for long-term delivery of effective enzyme levels, including the systemic delivery of modified adult stem cells. The major revision to the research plan, however, is a new aim to explore in depth the effects of adding anti-cocaine antibody or cocaine vaccine on top of enzyme delivery. Preliminary results have already been obtained showing that such conditions are likely to reduce brain concentrations of drug more than is possible with either agent alone. The data also indicate that CocH continues to clear cocaine from the blood stream and is capable of "offloading" and destroying antibody bound drug within minutes. That effect should prepare the system to handle large doses of cocaine repeatedly delivered over short intervals of time. These considerations lead us to the major hypothesis that the administration of cocaine hydrolase to vaccinated or passively immunized subjects will have unprecedented power to drive drug-seeking behavior into complete and lasting extinction. PUBLIC HEALTH RELEVANCE: Recent advances in protein engineering have led to a human enzyme that destroys cocaine rapidly enough to prevent it from reaching the heart or brain. Our preliminary results show that this enzyme rescues rats from lethal seizures after drug overdose and also prevents formerly addicted rats from relapsing when they get access to cocaine. The parent grant is aimed at investigating whether direct treatment or gene therapy with this enzyme can reduce drug-seeking behavior in rats as a model for cocaine addiction in humans. The competitive revision requests support for a new aim which addresses the potential for dramatic gains in the power and duration of suppressing drug-seeking behavior by a synergistic combination of enzyme treatment with an anti-cocaine vaccine.