Generation of polyclonal catalytic antibodies against cocaine using transition state analogs of cocaine conjugated to diphtheria toxoid

Immunotherapies for the Treatment of Drug Addiction

Substance use disorders (SUD) are a serious public health concern globally. Existing treatment platforms suffer from a lack of effectiveness. The development of immunotherapies against these substances of abuse for both prophylactic and therapeutic use has gained tremendous importance as an alternative and/or supplementary to existing therapies. Significant development has been made in this area over the last few decades. Herein, we highlight the vaccine and other biologics development strategies, preclinical, clinical updates along with challenges and future directions. Articles were searched in PubMed, ClinicalTrial.gov, and google electronic databases relevant to development, preclinical, clinical trials of nicotine, cocaine, methamphetamine, and opioid vaccines. Various new emerging vaccine development strategies for SUD were also identified through this search and discussed. A good number of vaccine candidates demonstrated promising results in preclinical and clinical phases and support the concept of developing a vaccine for SUD. However, there have been no ultimate success as yet, and there remain some challenges with a massive push to take more candidates to clinical trials for further evaluation to break the bottleneck.

Antibody-Mediated Catalysis in Infection and Immunity

The existence of catalytic antibodies has been known for decades. Natural antibodies capable of cleaving nucleic acid, protein, and polysaccharide substrates have been described. Although the discovery of catalytic antibodies initially aroused great interest because of their promise for the development of new catalysts, their enzymatic performance has been disappointing due to low reaction rates. However, in the areas of infection and immunity, where processes often occur over much longer times and involve high antibody concentrations, even low catalytic rates have the potential to influence biological outcomes. In this regard, the presence of catalytic antibodies recognizing host antigens has been associated with several autoimmune diseases. Furthermore, naturally occurring catalytic antibodies to microbial determinants have been correlated with resistance to infection. Recently, there has been substantial interest in harnessing the power of antibody-mediated catalysis against microbial antigens for host defense. Additional work is needed, however, to better understand the prevalence, function, and structural basis of catalytic activity in antibodies. Here we review the available information and suggest that antibody-mediated catalysis is a fertile area for study with broad applications in infection and immunity.

Vaccines against drugs of abuse: where are we now?

Drug addiction is a serious problem worldwide. One therapy being investigated is vaccines against drugs of abuse. The antibodies elicited against the drug can take up the drug and prevent it from reaching the reward centers in the brain. Few such vaccines have entered clinical trials, but research is going on apace. Many studies are very promising and more clinical trials should be coming out in the near future.

Probing active cocaine vaccination performance through catalytic and noncatalytic hapten design

Presently, there are no FDA-approved medications to treat cocaine addiction. Active vaccination has emerged as one approach to intervene through the rapid sequestering of the circulating drug, thus terminating both psychoactive effects and drug toxicity. Herein, we report our efforts examining two complementary, but mechanistically distinct active vaccines, i.e., noncatalytic and catalytic, for cocaine treatment. A cocaine-like hapten GNE and a cocaine transition-state analogue GNT were used to generate the active vaccines, respectively. GNE-KLH (keyhole limpet hemocyannin) was found to elicit persistent high-titer, cocaine-specific antibodies and blunt cocaine-induced locomotor behaviors. Catalytic antibodies induced by GNT-KLH were also shown to produce potent titers and suppress locomotor response in mice; however, upon repeated cocaine challenges, the vaccine's protecting effects waned. In depth kinetic analysis suggested that loss of catalytic activity was due to antibody modification by cocaine. The work provides new insights for the development of active vaccines for the treatment of cocaine abuse.

Anti-cocaine vaccine development

Cocaine abuse is an ongoing and serious problem that has led to the growth of a brutal criminal enterprise, particularly in the Americas and Europe. At present, there are no effective pharmacological agents available to treat the addiction by blocking cocaine or reversing its effects. In order to help motivated addicts conquer their addiction, vaccines against cocaine are being developed and one has progressed to clinical trials. This article will discuss the concept of antidrug vaccines in general, the successes and limitations of the various anti-cocaine vaccine approaches, the results of the clinical trials with an anti-cocaine vaccine and some new vaccine-mediated approaches to combat cocaine addiction.

Active immunotherapy for the Treatment of Cocaine Dependence

Although cocaine is illegal in most countries of the world, addiction is common and increasing in many populations, and the effectiveness of current treatment options for those afflicted has been very limited. The availability of an anti-cocaine vaccine could offer help to those who wish to quit their addiction. A number of vaccines differing in their chemical nature have been developed, and one has advanced into clinical trials. This review will discuss the successes and limitations of the various vaccines and the results of clinical trials of the vaccine using succinyl norcocaine conjugated to cholera toxin B. This latter vaccine shows considerable promise for those individuals whose antibody response is adequate..

[New developments in the pharmacotherapy of cocaine dependence]

New possibilities with medications for the treatment of cocaine dependence have begun to emerge. For example, in a randomised controlled study, disulfiram succeeded for the first time in significantly reducing cocaine consumption. In October 2003, a phase IIb study was started in the USA testing active immunisation against cocaine dependence. There is also an ongoing study in Switzerland testing methylphenidate treatment in combination with cognitive behavioural therapy. Pilot studies indicate that vigabatrin, selegiline, and topiramate are promising candidates for further clinical substance testing.

Vaccines against drugs of abuse: a viable treatment option?

Drug addiction is a chronically relapsing brain disorder. There is an urgent need for new treatment options for this disease because the relapse rate among drug abusers seeking treatment is quite high. During the past decade, many groups have explored the feasibility of using vaccines directed against drugs of abuse as a means of eliminating illicit drug use as well as drug overdose and neurotoxicity. Vaccines work by inducing drug-specific antibodies in the bloodstream that bind to the drug of abuse and prevent its entry into the brain. The majority of work in this area has been conducted with vaccines and antibodies directed against cocaine and nicotine. On the basis of preclinical work, vaccines for cocaine and nicotine are now in clinical trials because they can offer long-term protection with minimal treatment compliance. In addition, vaccines and antibodies for phencyclidine, methamphetamine and heroin abuse are currently under development. An underlying theme in this research is the need for high concentrations of circulating drug-specific antibodies to reduce drug-seeking and drug-taking behaviour when the drug is repeatedly available, especially in high doses. Although vaccines against drugs of abuse may become a viable treatment option, there are several drawbacks that need to be considered. These include: a lack of protection against a structurally dissimilar drug that produces the same effects as the drug of choice;a lack of an effect on drug craving that predisposes an addict to relapse; and tremendous individual variability in antibody formation. Forced or coerced vaccination is not likely to work from a scientific perspective, and also carries serious legal and ethical concerns. All things considered, vaccination against a drug of abuse is likely to work best with individuals who are highly motivated to quit using drugs altogether and as part of a comprehensive treatment programme. As such, the medical treatment of drug abuse will not be radically different from treatment of other chronic diseases.

Polyclonal catalytic antibodies

Polyclonal catalytic antibodies offer advantages in the evaluation of immunogens and in the ease of production of large quantities of antibodies. They comprise the entire immune response of an animal to an immunogen where monoclonals represent a subset. Polyclonal antibodies are consequently particularly suitable for evaluating catalytic antibody responses generated by different haptens or a group of structurally related haptens. The authors reported the first polyclonal catalytic antibodies in 1990. An unexpected finding is that polyclonal catalytic antibodies show single-site kinetic behaviour, i.e. whatever structural heterogeneity exists, the kinetic behaviour is homogeneous. Many groups worldwide have since published work in this area. Three groups are prominent. The authors' group, a group based in Austin, Texas, and led by Iverson, and a Shanghai group. The authors' group works with sheep antibodies and has published mechanistic studies and, more recently, specificity studies that revealed the catalysis of a beta-lactam. Most of this work over a 10-year period was performed by using a single bleed from a single sheep, which gives an indication of the ease of production and utility of such catalytic antibodies. Iverson's group works with rabbit antibodies and has published much work on the evaluation of catalytic antibodies generated by structurally related haptens. The Shanghai group has concentrated on the studies of polyclonal catalytic antibodies for electrocyclic reactions where any danger of contaminating enzymes is reduced. The use of immunisation to generate therapeutically useful catalytic antibodies (necessarily polyclonal) in a host animal is an attractive target. Several groups are working towards this. The authors themselves have published in this area and promising recent studies come from a group working in France on immunisation to protect against nerve agents and a Texas group (based in Houston) that has demonstrated active immunisation to generate antibodies that catalyse the hydrolysis of a carbamate insecticide.

Exploiting antibodies as catalysts: potential therapeutic applications

In this review, we explore recent developments in the generation of catalytic antibodies and their potential in therapy.

An investigation of antibody acyl hydrolysis catalysis using a large set of related haptens

An aspect of catalytic antibody research that receives little attention in the literature involves hapten systems that fail to elicit antibody catalysts despite a high affinity immune response and hapten designs that resemble those known to elicit catalysts. We have investigated a series of 12 phosphate and phosphonate haptens in a total of three animal systems. Dramatic and reproducible differences were observed in the catalytic activities of polyclonal antibodies elicited by the different haptens. A phosphate hapten with a phenyl ring on the side of the hapten opposite the linker elicited reproducibly high levels of polyclonal antibody catalytic activity. The other 11 haptens, most with benzyl groups on the side of the hapten opposite the linker, elicited immune responses in which catalytic activity was significantly weaker in terms of the level of observed catalytic activity, as well as frequency of elicited catalysts. Our results indicate that subtle features of transition state analogue hapten structure can have a dramatic and reproducible influence over the catalytic activity of elicited antibodies in related haptens. Whatever the explanation, subtle changes in mechanistic features due to altered leaving group ability/location or overall hapten flexibility, the comprehensive data presented here indicate that phenyl or 4-nitrophenyl leaving groups located opposite the hapten linker are to be preferred in order to elicit highly active antibody catalysts for acyl hydrolysis reactions.

Synthesis of a transition state analogue for the hydrolysis of cocaine: assistance to phosphonylation of a 3beta-hydroxytropane by a neighbouring amide group

A simple synthesis of phenylphosphonate monoester analogues of the transition state for hydrolysis of the benzoyl ester group in cocaine is provided by the reaction of 2beta-amido-3beta-tropanols with phenylphosphonyl dichloride. Steric hindrance to phosphonylation of the hydroxyl is overcome because the neighbouring 2beta-amido group participates in the reaction. The intramolecular assistance by the amide to formation of the phosphonate ester is influenced by the electronic environment of the amide group.