Vaccines for drugs of abuse have
yet to achieve full clinical relevance,
largely due to poor/inconsistent immune responses in patients. The
use of multivalent scaffolding as a means to tailor drug–hapten
density and clustering was examined in the context of drug-immune
response modulation. A modular trivalent hapten containing a diglycine
spacer, triAM1(Gly)2, was synthesized and shown to elicit
anti-nicotine antibodies at equivalent affinity and concentration
to the monovalent AM1 analog, despite in this instance having a lower
effective hapten density. Augmenting this data, the corresponding
monovalent hapten AM1(Gly)2 resulted in enhanced antibody
affinity and concentration. Drug-hapten clustering represents a new
vaccine paradigm, and, while examined only in the context of nicotine,
it should be readily translatable to other drugs of abuse.
Active immunization is an effective
means of blocking the pharmacodynamic
effects of drugs and holds promise as a treatment for heroin addiction.
Previously, we demonstrated the efficacy of our first-generation vaccine
in blocking heroin self-administration in rats, however, many vaccine
components can be modified to further improve performance. Herein
we examine the effects of varying heroin vaccine injection route and
adjuvant formulation. Mice immunized via subcutaneous (sc) injection
exhibited inferior anti-heroin titers compared to intraperitoneal
(ip) and sc/ip coadministration injection routes. Addition of TLR9
agonist cytosine-guanine oligodeoxynucleotide 1826 (CpG ODN 1826)
to the original alum adjuvant elicited superior antibody titers and
opioid affinities compared to alum alone. To thoroughly assess vaccine
efficacy, full dose–response curves were generated for heroin-induced
analgesia in both hot plate and tail immersion tests. Mice treated
with CpG ODN 1826 exhibited greatly shifted dose–response curves
(10–13-fold vs unvaccinated controls) while non-CpG ODN vaccine
groups did not exhibit the same robust effect (2–7-fold shift
for ip and combo, 2–3-fold shift for sc). Our results suggest
that CpG ODN 1826 is a highly potent adjuvant, and injection routes
should be considered for development of small molecule–protein
conjugate vaccines. Lastly, this study has established a new standard
for assessing drugs of abuse vaccines, wherein a full dose–response
curve should be performed in an appropriate behavioral task.
vaccine; heroin; analgesia; dose−response; antibody; route of administration; adjuvant; CpG ODN
The botulinum neurotoxins, characterized by their neuromuscular paralytic effects, are the most toxic proteins known to man. Due to their extreme potency, ease of production, and duration of activity, the BoNT proteins have been classified by the Centers for Disease Control as high threat agents for bioterrorism. In an attempt to discover effective BoNT therapeutics, we have pursued a strategy in which we leverage the blockade of K+ channels that ultimately results in the reversal of neuromuscular paralysis. Towards this end, we utilized peptides derived from scorpion venom that are highly potent K+ channel blockers. Herein, we report the synthesis of charybdotoxin, a 37 amino acid peptide, and detail its activity, along with iberiotoxin and margatoxin, in a mouse phrenic nerve hemidiaphragm assay in the absence and the presence of BoNT/A.
Botulinum neurotoxin; Scorpion toxin; Bioterrorism; Aminopyridine; Phrenic nerve hemidiaphragm
Judicious hapten design has been shown to be of importance when trying to generate a viable vaccine against a drug of abuse. Hapten design has typically been predicated upon faithfully emulating the unique chemical architecture that each drug presents. However, the need for drug-hapten congruency may also compromise vaccine immunogenicity if the drug-hapten conjugate possesses epitope instability. There has been no systematic study on the impact of hapten stability as it relates to vaccine immunogenicity. As a starting point, we have probed the stability of a series of cocaine haptens through varying several of its structural elements, including functionality at the C2-position, the nature of the linker and its site of attachment. Accordingly, a hydrolytic stability profile of four cocaine haptens (GNNA, GNNS, GNE and GNC) was produced and these results were compared through each hapten’s immunological properties, which were generated via active vaccination. From this group of four, three of the haptens, GNE, GNNA and GNC were further examined in an animal behavioral model, and findings here were again measured in relationship to hapten stability. We demonstrate a corresponding relationship between the half-life of the hapten and its immunogenicity, wherein haptens presenting a fully representative cocaine framework elicited higher concentrations of cocaine-specific IgG in sera and also conferred better protection against cocaine-induced locomotor activity. Our results indicate that hapten half-life plays an important role in vaccine immunogenicity and this in turn can impact animal behavioral effects when challenged with a drug of abuse.
Anti-cocaine vaccine; Hapten; Kinetics; Immunogenicity; Psychomotor stimulant Effects
The botulinum neurotoxin light chain (LC) protease has become an important therapeutic target for post-exposure treatment of botulism. Hydroxamic acid based small molecules have proven to be potent inhibitors of LC/A with nanomolar Ki values, yet, they lack cellular activity conceivably due to low membrane permeability. To overcome this potential liability, we investigated two prodrug strategies, 1,4,2-dioxazole and carbamate, based on our 1- adamantylacetohydroxamic acid scaffold. The 1,4,2-dioxazole prodrug did not demonstrate cellular activity, however, carbamates exhibited cellular potency with the most active compound displaying an EC50 value of 20 μM. Cellular trafficking studies were conducted using a “fluorescently silent” prodrug that remained in this state until cellular uptake was complete, which allowed for visualization of the drug’s release inside neuronal cells. In sum, this research sets the stage for future studies leveraging the specific targeting and delivery of these prodrugs, as well as other antibotulinum agents, into neuronal cells.
The opportunistic bacterial pathogen Pseudomonas aeruginosa causes chronic lung infections in cystic fibrosis (CF) patients. Importantly, virulence factor expression and biofilm formation in P. aeruginosa is coordinated by quorum sensing (QS) and one of the key QS signaling molecules is 3-oxo-C12-HSL. Remarkably, a tetramic acid, (C12-TA), with antibacterial properties is formed spontaneously from 3-oxo-C12-HSL under physiological conditions. Seeking to better understand this relationship we sought to investigate if 3-oxo-C12-HSL and C12-TA may be contributing factors to the overall pathogenicity of P. aeruginosa in CF individuals and their detection and quantitation in sputum samples might be used as an indicator to assess disease states and monitor therapy success in CF patients. To this end, 3-oxo-C12-HSL and C12-TA concentrations were initially analyzed in P. aeruginosa flow cell biofilms using liquid chromatography coupled with mass spectrometry (LC-MS). A liquid chromatography tandem mass spectrometry (LC-MS-MS)-based method was then developed and validated for their detection and quantification in sputa of CF patients. We highlight that this is the first report to show the presence of both the quorum sensing molecule (3-oxo-C12-HSL) and its rearranged product (C12-TA) in human clinical samples such as sputum. A total of 47 sputum samples from 20 CF and 2 non-CF individuals were analyzed: 3-oxo-C12-HSL was detected and quantified in 45 samples with concentrations ranging from 20 nM to >1000 nM; C12-TA was found in 14 samples (13 – 900 nM). Based on our findings, quorum sensing autoinducers merit further investigation as biomarkers for infectious disease states.
cystic fibrosis; sputum; quorum sensing; Pseudomonas aeruginosa; 3-oxo-C12-HSL; C12-TA; mass spectrometry
Cocaine addiction is a major problem for which there is no approved pharmacotherapy. We have developed a vaccine to cocaine (dAd5GNE), based on the cocaine analog GNE linked to the capsid proteins of a serotype 5 adenovirus, designed to evoke anti-cocaine antibodies that sequester cocaine in the blood, preventing access to the CNS. To assess the efficacy of dAd5GNE in a large animal model, positron emission tomography (PET) and the radiotracer [11C]PE2I were used to measure cocaine occupancy of the dopamine transporter (DAT) in nonhuman primates. Repeat administration of dAd5GNE induced high anti-cocaine titers. Before vaccination, cocaine displaced PE2I from DAT in the caudate and putamen, resulting in 62±4% cocaine occupancy. In contrast, dAd5GNE-vaccinated animals showed reduced cocaine occupancy such that when anti-cocaine titers were >4 × 105, the cocaine occupancy was reduced to levels of <20%, significantly below the 47% threshold required to evoke the subjective ‘high' reported in humans.
animal models; behavioral science; cocaine vaccine; imaging; clinical or preclinical; neuropharmacology; cocaine; vaccine; dopamine transporter (DAT); PET imaging; addiction
The oncogenic bHLH-LZ transcription factor Myc forms binary complexes with its binding partner Max. These and other bHLH-LZ-based protein-protein interactions (PPI) in the Myc-Max network are essential for the physiological and oncogenic activities of Myc. We have generated a genetically determined and highly specific protein-fragment complementation assay based on Renilla luciferase to analyze the dynamic interplay of bHLH-LZ transcription factors Myc, Max, and Mxd1 in vivo. We also applied this PPI reporter to quantify alterations of nuclear Myc-Max complexes in response to mutational events, competitive binding by the transcriptional repressor Mxd1, or perturbations by small-molecule Myc inhibitors, including recently identified potent PPI inhibitors from a Kröhnke pyridine library. We show that the specificity of Myc-Max PPI reduction by the pyridine inhibitors directly correlates with their efficient and highly specific potential to interfere with the proliferation of human and avian tumor cells displaying deregulated Myc expression. In a direct comparison with known Myc inhibitors using human and avian cell systems, the pyridine compounds reveal a unique inhibitory potential even at sub-micromolar concentrations combined with remarkable specificity for the inhibition of Myc-driven tumor cell proliferation. Furthermore, we show in direct comparisons using defined avian cell systems that different Max PPI profiles for the variant members of the Myc protein family (c-Myc, v-Myc, N-Myc, L-Myc) correlate with their diverse oncogenic potential and their variable sensitivity to the novel pyridine inhibitors.
transcription factor; protein-protein interactions; biosensor; small-molecule inhibitors; cancer
In order to create an effective immunization approach for a potential vaccine to heroin, liposomes containing monophosphoryl lipid A [L(MPLA)] were tested as an adjuvant system to induce antibodies to heroin hapten analogs. Four synthetic haptens and two immunization strategies were employed. In the first strategy, a hydrophobic 23 amino acid immunogenic peptide derived from the membrane proximal external region of gp41 from HIV-1 envelope protein was embedded as a carrier in the outer surface of L(MPLA), to which was conjugated a 15 amino acid universal T cell epitope and a terminal heroin hapten analog. In the second strategy, tetanus toxoid (TT) carrier protein was decorated with haptens by conjugation, and the hapten-conjugated protein was mixed with L(MPLA). After immunization of mice, each of the immunization strategies was effective for induction of IgG anti-hapten antibodies. The first immunization strategy induced a mean end-point IgG titer against one of two haptens tested of approximately 12,800; however, no detectable antibodies were induced against the liposome-associated HIV-1 carrier peptide. In the second immunization strategy, depending on the hapten used for decorating the TT, end-point IgG titers ranged from 100,000 to 6,500,000. In this strategy, in which hapten was conjugated to the TT, end-point IgG titers of 400,000 to the TT carrier were observed with each conjugate. However, upon mixing unconjugated TT with L(MPLA), anti-TT titers of 6,500,000 were observed. We conclude that L(MPLA) serves as a potent adjuvant for inducing antibodies to candidate heroin haptens. However, antibodies to the carrier peptide or protein were partly or completed inhibited by the presence of conjugated hapten.
Liposomes containing monophosphoryl lipid A; adjuvant system; opiate vaccine; antibodies to heroin haptens
Small molecule probes have been employed extensively to explore biological systems and elucidate cellular signaling pathways. In this study, we utilize an inhibitor of bacterial communication to monitor changes in the proteome of Salmonella enterica serovar Typhimurium with the aim of discovering new processes regulated by AI-2-based quorum sensing (QS), a mechanism of bacterial intracellular communication that allows for the coordination of gene expression in a cell density-dependent manner. In S. typhimurium, this system regulates the uptake and catabolism of intracellular signals and has been implicated in pathogenesis, including the invasion of host epithelial cells. We demonstrate that our QS antagonist is capable of selectively inhibiting the expression of known QS-regulated proteins in S. typhimurium, thus attesting that QS inhibitors may be used to confirm proposed and elucidate previously unidentified QS pathways without relying on genetic manipulation.
Streptococcus pneumoniae relies on a number of virulence factors, including immunoglobulin A1 protease (IgA1P), a Zn2+ metalloprotease produced on the extracellular surface of the bacteria, to promote pathogenic colonization. IgA1P exhibits a unique function, in that it catalyzes the proteolysis of human IgA1 at its hinge region to leave the bacterial cell surface masked by IgA1 Fab, enabling the bacteria to evade the host's immune system and adhere to host epithelial cells to promote colonization. Thus, S. pneumoniae IgA1P has emerged as a promising antibacterial target; however, the lack of an appropriate screening assay has limited the investigation of this metalloprotease virulence factor. Relying on electrostatics-mediated AuNP aggregation, we have designed a promising high-throughput colorimetric assay for IgA1P. By using this assay, we have uncovered inhibitors of the enzyme that should be useful in deciphering its role in pneumococcal colonization and virulence.
Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) preferentially induces apoptosis in cancer cells over normal cells; however, tumor cells may develop TRAIL resistance. Here we demonstrate that this resistance can be overcome in the presence of bacterial acylhomoserine lactones (AHLs) or AHL-producing bacteria through the combined effect of TRAIL-induced apoptosis and AHL-mediated inhibition of inflammation regulated by NF-κB signaling. This discovery unveils a previously unrecognized symbiotic link between bacteria and host immunosurveillance.
Despite antismoking campaigns, cigarette smoking remains a pervasive addiction with significant societal impact, accounting for one of every five deaths. Smoking cessation therapies to help smokers quit are ineffective with a high recidivism rate. With the knowledge that nicotine is the principal addictive compound of cigarettes, we have developed an antismoking vaccine based on the highly immunogenic properties of the hexon protein purified from the serotype 5 adenovirus (Ad) capsid. We hypothesized that an effective antinicotine vaccine could be based on coupling the nicotine hapten AM1 to purified Ad hexon protein. To assess this, AM1 was conjugated to hexon purified from serotype 5 Ad to produce the HexonAM1 vaccine. C57Bl/6 mice were sensitized by 10 daily nicotine administrations (0.5 mg/kg, subcutaneous) to render the mice addicted to nicotine. Control groups were sensitized to phosphate-buffered saline (PBS). The mice were then immunized with HexonAM1 (4 μg, intramuscular) at 0, 3, and 6 weeks. By 6 weeks, the HexonAM1-vaccinated mice had serum antinicotine antibody titers of 1.1×106±7.6×104. To demonstrate that these high antinicotine titers were sufficient to suppress the effects of nicotine, HexonAM1-vaccinated mice were evaluated for nicotine-induced hypoactive behavior with nicotine challenges (0.5 mg/kg wt) over 5 weeks. In all challenges, the HexonAM1-vaccinated mice behaved similar to PBS-challenged naive mice. These data demonstrate that a vaccine comprised of a nicotine analog coupled to Ad hexon can evoke a high level of antinicotine antibodies sufficient to inhibit nicotine-induced behavior. The HexonAM1 vaccine represents a platform paradigm for vaccines against small molecules.
Rosenberg and colleagues describe an antinicotine vaccine comprising a nicotine analog (AM1) coupled to hexon protein purified from the adenovirus serotype 5 capsid. They show that this vaccine can elicit high levels of antinicotine antibodies in vivo and that this leads to significant inhibition of nicotine-induced behaviors in C57BL/6 mice.
In enteric bacteria, the kinase LsrK catalyzes the phosphorylation of the C5-hydroxyl group in the linear form of 4,5-dihydroxy-2,3-pentanedione (DPD), the precursor of the type II bacterial quorum sensing molecule (AI-2). This phosphorylation is required for AI-2 sequestration in the cytoplasm and subsequent derepression of AI-2 related genes necessary for quorum development. While LsrK is a critical enzyme within the DPD quorum sensing relay system, kinetic details of this kinase have yet to be reported. A continuous UV-vis spectrophotometric assay was developed, which allowed steady-state kinetic analysis of LsrK to be undertaken with the substrates ATP and DPD. The data was most consistent with a rapid equilibrium ordered mechanism with ATP binding first: kcat (7.4 ± 0.6 s−1), Km,ATP (150 ± 30 µM) and Km(app),DPD (1.0 ± 0.2 mM). The assay also allowed a DPD substrate profile to be conducted, which provided an unexpected biochemical disconnect between the previous agonist/antagonist cell based reporter assay and the LsrK assay presented herein. Together these findings raise the importance of LsrK and lay the foundation not only for further understanding of this enzyme and its critical biological role but also the rational design of regulatory molecules targeting AI-2 quorum sensing in pathogenic bacteria.
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 complimentary, 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 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.
Active immunization; Anti-cocaine vaccine; Hapten synthesis; Catalytic antibodies; Psychomotor stimulant effects
Tropolone emerged from the screening of a chelator fragment library (CFL) as an inhibitor of the Zn2+-dependent virulence factor, Pseudomonas aeruginosa elastase (LasB). Based on this initial hit, a series of substituted tropolone-based LasB inhibitors was prepared, and a compound displaying potent activity in vitro and in a bacterial swarming assay was identified. Importantly, this inhibitor was found to be specific for LasB over other metalloenzymes, validating the usage of tropolone as a viable scaffold for identifying first-in-class LasB inhibitors.
Botulinum neurotoxins (BoNTs) are the most lethal biotoxins known to mankind and are responsible for the neuroparalytic disease botulism. Current treatments for botulinum poisoning are all protein based and thus have a limited window of treatment opportunity. Inhibition of the BoNT light chain protease (LC) has emerged as a therapeutic strategy for the treatment of botulism as it may provide an effective post exposure remedy. Using a combination of crystallographic and modeling studies a series of hydroxamates derived from 1-adamantylacetohydroxamic acid (3a) were prepared. From this group of compounds, an improved potency of about 17-fold was observed for two derivatives. Detailed mechanistic studies on these structures revealed a competitive inhibition model, with a Ki = 27 nM, which makes these compounds some of the most potent small molecule, non-peptidic BoNT/A LC inhibitors reported to date.
Botulinum neurotoxin; Protease inhibitor; Adamantane derivatives; Small molecule inhibitor; Zinc-dependent metalloprotease
Cocaine addiction is a long-lasting relapsing illness characterized by cycles of abuse, abstinence and reinstatement, and antibody-based therapies could be a powerful therapeutic approach. Herein, we explored the possibility of using halogenated cocaine haptens to enhance the immunological properties of anti-cocaine vaccines. Three fluorine-containing cocaine haptens (GNF, GNCF and GN5F) and one chlorine-containing cocaine hapten (GNCl) were designed and synthesized, based upon the chemical scaffold of the only hapten that has reached clinical trials, succinyl norcocaine (SNC). Hapten GNF was found to retain potent cocaine affinity, and also elicit antibodies in a higher concentration than the parent structure SNC. Our data suggests that strategic hapten fluorination could be useful for not only improving upon the current cocaine vaccine undergoing clinical trials, but it may also be a valuable new approach, with application to any of the vaccines being developed for the treatment of drugs of abuse.
As a guide for chemical probe design, focused analogue synthetic studies were undertaken upon the lactone ring of 3-oxo-C12-homoserine lactone. We have concluded that hydrolytic instability of the heterocyclic ring is pivotal for its ability to modulate immune signaling and probe preparation was aligned with these findings.
A major liability of existing nicotine vaccine candidates is the wide variation in anti-nicotine immune responses among clinical trial participants. In order to address this liability, significant emphasis has been directed at evaluating adjuvants and delivery systems that confer more robust potentiation of the anti-nicotine immune response. Toward that end, we have initiated work that seeks to exploit the adjuvant effect of liposomes, with or without Toll-like receptor agonist(s). The results of the murine immunization study described herein support the hypothesis that a liposomal nicotine vaccine formulation may provide a means for addressing the immunogenicity challenge.
Immunopharmacotherapy; Liposome; Nicotine; Vaccine; Adjuvant
Botulinum neurotoxins (BoNTs) are among the most deadly poisons known though ironically, they also are of great therapeutic utility. A number of research programs have been initiated to discover small molecule inhibitors of BoNTs metalloprotease activity. Many, though not all of these programs have screened against a truncated and more stable form of the enzyme, that possess comparable catalytic properties to the full length enzyme. Interestingly, several classes of inhibitors notably the hydroxamates, display a large shift in potency between the two enzyme forms. In this report we compare the kinetics of active-site, alpha-exosite and beta-exosite inhibitors versus truncated and full length enzyme. Molecular dynamics simulations conducted with the truncated and homology models of the fully length BoNT LC/A indicate the flexibility of the C-terminus of the full length enzyme is responsible for the potency shifts of active-site proximally binding inhibitors while distal binding (alpha-exosite) inhibitors remain equipotent.
Botulinum neurotoxin; zinc-dependent metalloprotease; protease inhibitor; small molecule inhibitor; natural product
Botulinum neurotoxins (BoNTs) are among the most deadly
known, though ironically, they also are of great therapeutic utility.
A number of research programs have been initiated to discover small
molecule inhibitors of BoNTs metalloprotease activity. Many, though
not all, of these programs have screened against a truncated and more
stable form of the enzyme, that possesses comparable catalytic properties
to the full length enzyme. Interestingly, several classes of inhibitors,
notably the hydroxamates, display a large shift in potency between
the two enzyme forms. In this report we compare the kinetics of active-site,
α-exosite and β-exosite inhibitors versus truncated and
full length enzyme. Molecular dynamics simulations conducted with
the truncated and homology models of the full length BoNT LC/A indicate
the flexibility of the C-terminus of the full length enzyme is responsible
for the potency shifts of active-site proximally binding inhibitors
while distal binding (α-exosite) inhibitors remain equipotent.
Botulinum neurotoxin; zinc-dependent metalloprotease; protease inhibitor; small molecule inhibitor; natural product
Adenovirus (Ad) vaccine vectors have been used for many applications due to the capacity of the Ad capsid proteins to evoke potent immune responses, but these vectors are often ineffective in the context of pre-existing anti-Ad immunity. Leveraging the knowledge that E1−E3− Ad gene transfer vectors are potent immunogens, we have developed a vaccine platform against small molecules by covalently coupling analogs of small molecules to the capsid proteins of disrupted Ad (dAd5). We hypothesized that the dAd5 platform would maintain immunopotency even in the context of anti-Ad neutralizing antibodies. To test this hypothesis, we coupled cocaine and nicotine analogs, GNE and AM1, to dAd5 capsid proteins to generate dAd5GNE and dAd5AM1, respectively. Mice were pre-immunized with Ad5Null, resulting in high titer anti-Ad5 neutralizing antibodies comparable to those observed in the human population. The dAd5GNE and dAd5AM1 vaccines elicited high anti-cocaine and anti-nicotine antibody titers, respectively, in both naive and Ad5-immune mice, and both functioned to prevent cocaine or nicotine from reaching the brain of anti-Ad immune mice. Thus, disrupted Ad5 evokes potent humoral immunity that is effective in the context of pre-existing neutralizing anti-Ad immunity, overcoming a major limitation for current Ad-based vaccines.
De and colleagues examine the efficacy of adenovirus-based vaccines against cocaine and nicotine. They report that each respective vaccine elicits high anti-cocaine or anti-nicotine antibody titers in mice irrespective of preexisting neutralizing anti-adenovirus immunity.
We challenged the performance of our previous heroin vaccine with a similar vaccine containing a more hydrolytically stable hapten analogue and a Th1 adjuvant (CpG ODN). Our results indicate that the elements of our previous vaccine are essential for its anti-heroin potency, i.e. a chemically labile hapten and an exclusively Th2 humoral response elicited by alum. Such design elements are critical for producing next generation heroin vaccines.
Cocaine achieves its psychostimulant, reinforcing properties through selectively blocking dopamine transporters, and this neurobiological mechanism impedes the use of classical receptor-antagonist pharmacotherapies to outcompete cocaine at CNS sites. Passive immunization with monoclonal antibodies (mAb) specific for cocaine circumvents this problem as drug is sequestered in the periphery prior to entry into the brain. To optimize an immunopharmacotherapeutic strategy for reversing severe cocaine toxicity, the therapeutic properties of mAb GNC92H2 IgG were compared to those of its engineered formats in a mouse overdose model. Whereas the extended half-life of an IgG justifies its application to the prophylactic treatment of addiction, the rapid, thorough biodistribution of mAb-based fragments, including F(ab')2, Fab and scFv, may correlate to accelerated scavenging of cocaine and reversal of toxicity. To test this hypothesis, mice were administered the anti-cocaine IgG (180 mg/kg, i.v.) or GNC92H2-based agent after receiving an LD50 cocaine dose (93 mg/kg, i.p.), and the timeline of overdose symptoms was recorded. All formats lowered the rate of lethality despite the >100-fold molar excess of drug to antibody binding capacity. However, only F(ab')2-92H2 and Fab-92H2 significantly attenuated the progression of premorbid behaviors, and Fab-92H2 prevented seizure generation in a percentage of mice. The calculation of serum half-life of each format demonstrated that the pharmacokinetic profile of Fab-92H2 (elimination half-life, t1/2 ∼ 100 minutes) best approximated that of cocaine. These results not only confirm the importance of highly specific and tight drug binding by the mAb, but also highlight the benefit of aligning the pharmacokinetic and pharmacodynamic properties of the immunopharmacotherapeutic with the targeted drug.
Cocaine; Drug Overdose; Immunopharmacotherapy; Vaccine; Passive Immunization; Monoclonal Antibody; Mice