Author ORCID Identifier

https://orcid.org/0009-0000-6493-6412

Date Available

12-16-2026

Year of Publication

2024

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy (PhD)

College

Pharmacy

Department/School/Program

Pharmaceutical Sciences

Advisor

Dr. Chang-Guo Zhan

Abstract

Cocaine use disorder (CUD) has spanned several decades and continues to be a severe social and public health problem with high morbidity and mortality rate in the United States of America. However, there is no FDA-approved pharmacological treatment specific for CUD despite decades of efforts. It is hypothesized and proposed that a pharmacokinetic approach utilizing an efficient long-lasting cocaine-metabolizing enzyme could be a truly effective treatment strategy for CUD. Our recently designed and developed recombinant Fc-fused protein, known as CocH5-Fc(M6), represents the currently most efficient long-acting cocaine hydrolase (CocH) against cocaine based on the results from in vitro characterization with Kcat = 13,800 ± 750 min-1 and KM = 3.89 ± 0.76 μM. Preliminary preclinical studies demonstrated that a low dose of CocH5-Fc(M6) (1 mg/kg) via intravenous injection (IV) was able to accelerate cocaine metabolism, protect and rescue rats from a lethal dose of cocaine (180 mg/kg), injected intraperitoneally (IP), effectively blocked cocaine-induced hyperactivity and blocked cocaine-induced dopamine transporter (DAT) trafficking. Meanwhile, CocH5-Fc(M6) has the desired in vitro and in vivo stability as a therapeutic protein with an elimination half-life of 229 ± 5 h in rats.

The investigation described in this dissertation mainly aimed to continue evaluating the preclinical efficacy and clinical potential of CocH5-Fc(M6) as a therapeutic treatment of CUD. The cocaine discrimination and cocaine intravenous self-administration models were employed to study the effectiveness and duration of CocH5-Fc(M6) in blocking the psychostimulant, discriminative stimulus, and reinforcing effects of cocaine in rats. The impacts of CocH5-Fc(M6) on cocaine metabolism and cocaine-driving drug craving and drug seeking behaviors were characterized as well. At last, additional effort was put into studying polysubstance use involving heroin and cocaine. A quantitative LC-MS/MS method was developed and validated to study the role of cocaine in the etiology of heroin-related deaths in the context of molecular pharmacokinetics (PK) and to examine how cocaine-metabolizing enzyme such as CocH5-Fc(M6) affects the metabolism of cocaine and/or heroin when they are co-administered.

The results from this thesis have demonstrated that CocH5-Fc(M6) has the desired effects to block the interoceptive and discriminative stimulus effects of cocaine over a long period of time; CocH5-Fc(M6) is highly efficient to produce a favorable pattern of cocaine metabolism by converting cocaine and its active metabolites such as norcocaine and benzoylecgonine into inactive metabolites in vivo; CocH5-Fc(M6) is effective at long-lasting blocking cocaine voluntary intake (blocking cocaine’s reinforcing effect) and suppressing cocaine-induced reinstatement of drug-seeking behavior in rats. Finally, it has been demonstrated that the effectiveness of CocH5-Fc(M6) in metabolizing cocaine is not affected when cocaine is co-administered with heroin.

In summary, the long-acting cocaine hydrolase CocH5-Fc(M6) is a truly promising candidate of enzyme therapy and has the clinical potential to be developed as a therapeutic treatment of CUD.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2024.472

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Available for download on Wednesday, December 16, 2026

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