MPZP: a novel small molecule corticotropin-releasing factor type 1 receptor (CRF1) antagonist.

The extrahypothalamic stress peptide corticotropin-releasing factor (CRF) system is an important regulator of behavioral responses to stress. Dysregulation of CRF and the CRF type 1 receptor (CRF(1)) system is hypothesized to underlie many stress-related disorders. Modulation of the CRF(1) system by non-peptide antagonists currently is being explored as a therapeutic approach for anxiety disorders and alcohol dependence. Here, we describe a new, less hydrophilic (cLogP approximately 2.95), small molecule, non-peptide CRF(1) antagonist with high affinity (K(i)=4.9 nM) and specificity for CRF(1) receptors: N,N-bis(2-methoxyethyl)-3-(4-methoxy-2-methylphenyl)-2,5-dimethyl-pyrazolo[1,5-a] pyrimidin-7-amine (MPZP). The compound was systemically administered to adult male rats in two behavioral models dependent on the CRF(1) system: defensive burying (0, 5, 20 mg/kg, n=6-11 for each dose) and alcohol dependence (0, 5, 10, 20 mg/kg, n=8 for each self-administration group). Acute administration of MPZP reduced burying behavior in the defensive burying model of active anxiety-like behavior. MPZP also attenuated withdrawal-induced excessive drinking in the self-administration model of alcohol dependence without affecting nondependent alcohol drinking or water consumption. The present findings support the proposed significance of the CRF(1) system in anxiety and alcohol dependence and introduce a promising new compound for further development in the treatment of alcohol dependence and stress-related disorders.

Delta9-tetrahydrocannabinol immunochemical studies: haptens, monoclonal antibodies, and a convenient synthesis of radiolabeled delta9-tetrahydrocannabinol.

Immunopharmacotherapy as an approach to combat drugs of abuse has become an active area of investigation. Marijuana is the most commonly used illicit drug in the U.S. The main active chemical in marijuana is delta9-tetrahydrocannabinol (delta9-THC); hence, monoclonal antibodies with high affinity and specificity for delta9-tetrahydrocannabinol could be valuable immunopharmacotherapeutic intervention and diagnostic tools. We have synthesized immunoconjugates that induce an effective immune response to delta9-THC and describe a convenient synthesis of radiolabeled delta9-THC. We demonstrate the value and use of this probe to select anti-delta9-THC antibodies that bind delta9-THC with good affinity. The synthetic route to radiolabeled delta9-THC has enabled the correct assessment of the affinity of these antibodies to their ligand and may facilitate future binding studies between delta9-THC and its analogues and the cannabinoid receptors.

A blue fluorescent antibody-cofactor sensor for mercury.

[reaction: see text] A chemically programmed antibody sensor, consisting of a stilbenyl boronic acid cofactor and monoclonal antibody EP2-19G2, provides a new method of mercury detection. The fluorescent antibody sensor generates an intense powder blue fluorescence when bound to the stilbenyl boronic acid cofactor; however, it is quenched in the presence of Hg(2+) ions. The EP2-19G2-cofactor biosensor provides micromolar sensitivity and selectivity toward Hg(2+) ions over a wide range of metal ions in aqueous solution.

Evaluation of the anticocaine monoclonal antibody GNC92H2 as an immunotherapy for cocaine overdose.

The illicit use of cocaine continues in epidemic proportions and treatment for cocaine overdose remains elusive. Current protein-based technology offers a new therapeutic venue by which antibodies bind the drug in the blood stream, inactivating its toxic effects. The therapeutic potential of the anticocaine antibody GNC92H2 was examined using a model of cocaine overdose. Swiss albino mice prepared with intrajugular catheters were tested in photocell cages after administration of 93 mg/kg (LD50) of cocaine and GNC92H2 infusions ranging from 30 to 190 mg/kg. GNC92H2 was delivered 30 min before, concomitantly or 3 min after cocaine treatment. Significant blockade of cocaine toxicity was observed with the higher dose of GNC92H2 (190 mg/kg), where premorbid behaviors were reduced up to 40%, seizures up to 77% and death by 72%. Importantly, GNC92H2 prevented death even post-cocaine injection. The results support the important potential of GNC92H2 as a therapeutic tool against cocaine overdose.

Fluorescent cocaine probes: a tool for the selection and engineering of therapeutic antibodies.

Cocaine is a highly addictive drug, and despite intensive efforts, effective therapies for cocaine craving and addiction remain elusive. In recent years, we and others have reported advances in anti-cocaine immunopharmacotherapy based on specific antibodies capable of sequestering the drug before it reaches the brain. In an effort to obtain high affinity therapeutic anti-cocaine antibodies, either whole IgGs or other antibody constructs, fluorescence spectroscopic techniques could provide a means of assisting selection and engineering strategies. We report the synthesis of a series of cocaine-fluorophore conjugates (GNC-F1, GNC-F2, GNC-I) and the functional evaluation of these compounds against single-chain Fv antibodies obtained via crystallographic analysis/engineering and against commercially available anti-cocaine monoclonal antibodies with a wide range of cocaine-binding affinities. From these studies, we determined that the GNC-F2 fluorophore reproduced affinity constants obtained using [(3)H]-labeled cocaine. We anticipate that the readily synthesized and nonradioactive GNC-F2 will find use both as a tool for bioimaging and in the high-throughput selection and engineering of potential therapeutic antibodies against cocaine.

Chiral sensing using a blue fluorescent antibody.

The chiral sensing of small molecules using a blue fluorescent antibody sensor is described.

A human single-chain antibody specific for integrin alpha3beta1 capable of cell internalization and delivery of antitumor agents.

Selective antitumor chemotherapy can be achieved by using antibody-drug conjugates that recognize surface proteins upregulated in cancer cells. One such receptor is integrin alpha3beta1, which is overexpressed on malignant melanoma, prostate carcinoma, and glioma cells. We previously identified a human single-chain Fv antibody (scFv), denoted Pan10, specific for integrin alpha3beta1 that is internalized by human pancreatic cancer cells. Herein, we describe the chemical introduction of reactive thiol groups onto Pan10, the specific conjugation of the modified scFv to maleimide-derivatized analogs of the potent cytotoxic agent duocarmycin SA, and the properties of the resultant conjugates. Our findings provide evidence that Pan10-drug conjugates maintain the internalizing capacity of the parent scFv and are cytotoxic at nanomolar concentrations. Our Pan10-drug conjugates may be promising candidates for targeted chemotherapy of malignant diseases associated with overexpression of integrin alpha3beta1.

Investigations using immunization to attenuate the psychoactive effects of nicotine.

Despite the enormous health risks, people continue to smoke and use tobacco primarily as a result of nicotine addiction. As part of our immunopharmacotherapy research, the effects of active and passive immunizations on acute nicotine-induced locomotor activity in rats were investigated. To this end, rats were immunized with either a NIC-KLH immunoconjugate vaccine designed to elicit an antinicotine immune response, or were administered an antinicotine monoclonal antibody, NIC9D9, prior to a series of nicotine challenges and testing sessions. Vaccinated rats showed a 45% decrease in locomotor activity compared to a 16% decrease in controls. Passive immunization with NIC9D9 resulted in a 66.9% decrease in locomotor activity versus a 3.4% decrease in controls. Consistent with the behavioral data, much less nicotine was found in the brains of immunized rats. The results support the potential clinical value of immunopharmacotherapy for nicotine addiction in the context of tobacco cessation programs.

Development of immunopharmacotherapy against drugs of abuse.

Drug addiction is a major worldwide medical and social problem that continues to escalate. The addiction syndrome is remarkably similar between different drugs of abuse, and can be characterized as a chronic relapsing brain disorder with neurobiological changes that lead to a compulsion to take a drug with loss of control over drug intake. Presently used medications for the treatment of dependence disorders are based on drugs that are either agonists or antagonists of drugs of abuse, and have yielded only limited success. Immunopharmacotherapy is based on the generation or administration of antibodies that are capable of binding the targeted drug before it can reach the brain, whereas replacement strategies based on agonists or antagonists of these drugs generally cause many undesired side effects. A large amount of data has been gathered in recent years on the effects of active and passive immunization against cocaine, nicotine, PCP and methamphetamine in animal models, suggesting potential efficacy of these treatments in humans; and clinical trials are currently underway for vaccines against cocaine and nicotine.

A new strategy for improved nicotine vaccines using conformationally constrained haptens.

Constrained nicotine analogues were synthesized and coupled to the carrier protein KLH. The immunogenic effects were compared to those using our previously designed flexible nicotine hapten. Immunization of mice with the constrained hapten conjugates resulted in highly increased antibody titers and affinity for nicotine.

Expression and characterization of a humanized cocaine-binding antibody.

The murine immunoglobulin G (IgG) cocaine-binding monoclonal antibody (mAb), GNC92H2, is notable for its exquisite specificity for cocaine, as opposed to chemically-related cocaine metabolites, and for its moderately high affinity (K(d) approximately 200 nM) for cocaine. Recently, we described the crystal structure of a mouse/human chimeric Fab construct at 2.3 A resolution. Herein, we report the successful framework humanization of a single-chain Fv (scFv) GNC92H2 construct without loss of affinity for cocaine. In brief, we compared the mAb GNC92H2 sequence to human antibody sequences, and used structure-based design to incorporate mutations (total = 49) that would humanize the framework region without affecting the overall shape of the binding pocket or the key cocaine-contact residues. The codons of the rationally designed sequence were optimized for E. coli expression, and the gene was synthesized by a de novo PCR reaction using 14 overlapping primers. Expression of the scFv construct was significantly improved in E. coli by fusion to thioredoxin. Intriguingly, this construct apparently refolds to form soluble active antibody in the reducing environment of the cytoplasm. Competitive ELISA and equilibrium dialysis demonstrated comparable binding activity between the humanized scFv and the whole IgG. The successful humanization of mAb GNC92H2 should enhance its potential therapeutic value by reducing its overall. immunogenicity.

Enabling ScFvs as multi-drug carriers: a dendritic approach.

To enable scFvs as multi-drug carriers, we designed and synthesized dendritic linker molecules bearing up to nine chlorambucil residues at the branch ends. A maleimide group was used at the focal point of the dendron for easy linkage to the scFv. Originally designed molecules showed poor water solubility. To address this problem, a lysine residue with an unprotected carboxylic acid group was inserted into the dendron branches. The new molecules showed excellent water solubility and are now suitable for conjugation. Such dendritic molecules will allow studies to understand the relationship between the drug/antibody ratio and the potency of the immunoconjugates. The dendritic approach could also be applied to drugs other than chlorambucil and carriers other than scFvs to greatly increase the drug/carrier ratio.

De novo identification of tumor-specific internalizing human antibody-receptor pairs by phage-display methods.

Three tumor-specific, internalizing human single-chain Fvs (scFvs) were obtained by direct selection against tumor cells from a large, nonimmune scFv-phage library pre-subtracted with various normal human cells. After scFv selection and characterization for cell binding and internalization, the scFvs were also employed in immunoprecipitations to identify putative receptors. In the case of a prostate tumor-cell specific scFv PR5, the receptor that mediated endocytosis was shown to be the transferrin receptor. For two pancreatic adenocarcinoma specific scFvs SW1 and PAN10, the alpha(3)beta(1) integrin was identified. The scFv SW1 was studied in further detail and found to induce functional effects as a ligand-mimetic by mediating cell adhesion and migration. The results demonstrated the feasibility of utilizing enhanced phage-display methods as a rapid and general approach for not only direct isolation of human internalizing scFvs, but also for identifying tumor cell-surface receptors from various classes. The use of scFv constructs that target tumor cells and undergo internalization could have significant impact on the future of cancer and gene therapy.

A cell-penetrating peptide from a novel pVII-pIX phage-displayed random peptide library.

A novel random peptide library was constructed using a phage-display format on the coat proteins pVII and pIX of filamentous bacteriophage. Panning against B-lymphocyte WI-L2 cells yielded one unique peptide-phage, denoted CHL8, that specifically bound to and penetrated the cells. Studies of each peptide derived from CHL8, denoted pep7 and pep9, established that only pep7 mediated the observed activity and only as a homodimer. Peptide libraries displayed on pVII-pIX should serve as a novel source of bioactive ligands for a variety of applications.

A method for the generation of combinatorial antibody libraries using pIX phage display.

For more than a decade, phage displayed combinatorial antibody libraries have been used to generate and select a wide variety of antibodies. We previously reported that the phage coat proteins pVII and pIX could be used to display the heterodimeric structure of the antibody Fv region. Herein, aspects of this technology were invoked and extended to construct a large, human single-chain Fv (scFv) library of 4.5 x 10(9) members displayed on pIX of filamentous bacteriophage. Furthermore, the diversity, quality, and utility of the library were demonstrated by the selection of scFv clones against six different protein antigens. Notably, more than 90% of the selected clones showed positive binding for their respective antigens after as few as three rounds of panning. Analyzed scFvs were also found to be of high affinity. For example, kinetic analysis (BIAcore) revealed that scFvs against staphylococcal enterotoxin B and cholera toxin B subunit had a nanomolar and subnanomolar dissociation constant, respectively, affording affinities comparable to, or exceeding that, of mAbs obtained from immunization. High specificity was also attained, not only between very distinct proteins, but also in the case of the Ricinus communis ("ricin") agglutinins (RCA(60) and RCA(120)), despite >80% sequence homology between the two. The results suggested that the performance of pIX-display libraries can potentially exceed that of the pIII-display format and make it ideally suited for panning a wide variety of target antigens.

Syntheses of dendritic linkers containing chlorambucil residues for the preparation of antibody-multidrug immunoconjugates.

A novel dendritic molecule with nine chlorambucil (CBL) residues on the surface and a maleimide moiety at the core terminus was synthesized using a convergent synthetic methodology. This molecule is ready for attachment to single-chain Fv antibodies (scFvs) to form antibody-multidrug immunoconjugates in an effort to study the relevance of drug/antibody molar ratio and the potency of these drug-antibody immunoconjugates. A monomer and a trimer with a similar structural motif were also prepared for comparative purposes.

Human antibodies against spores of the genus Bacillus: a model study for detection of and protection against anthrax and the bioterrorist threat.

A naive, human single-chain Fv (scFv) phage-display library was used in bio-panning against live, native spores of Bacillus subtilis IFO 3336 suspended in solution. A direct in vitro panning and enzyme-linked immunosorbent assay-based selection afforded a panel of nine scFv-phage clones of which two, 5B and 7E, were chosen for further study. These two clones differed in their relative specificity and affinity for spores of B. subtilis IFO 3336 vs. a panel of spores from 11 other Bacillus species/strains. A variety of enzyme-linked immunosorbent assay protocols indicated these scFv-phage clones recognized different spore epitopes. Notably, some spore epitopes markedly changed between the free and microtiter-plate immobilized state as revealed by antibody-phage binding. An additional library selection procedure also was examined by constructing a Fab chain-shuffled sublibrary from the nine positive clones and by using a subtractive panning strategy to remove crossreactivity with B. licheniformis 5A24. The Fab-phage clone 52 was improved compared with 5B and was comparable to 7E in binding B. subtilis IFO 3336 vs. B. licheniformis 5A24, yet showed a distinctive crossreactivity pattern with other spores. We also developed a method to directly detect individual spores by using fluorescently labeled antibody-phage. Finally, a variety of "powders" that might be used in deploying spores of B. anthracis were examined for antibody-phage binding. The strategies described provide a foundation to discover human antibodies specific for native spores of B. anthracis that can be developed as diagnostic and therapeutic reagents.

Synthesis, properties, and reactivity of cocaine benzoylthio ester possessing the cocaine absolute configuration.

One aspect of immunopharmacotherapy for cocaine abuse involves the use of a catalytic monoclonal antibody (mAb) to degrade cocaine via hydrolysis of the benzoate ester. A cocaine benzoylthio ester analogue provides a means to implement high-throughput selection strategies to potentially isolate mAbs with high activity. The required analogue was synthesized starting from (-)-cocaine hydrochloride and possessed the cocaine absolute configuration. Key points in the preparation were the introduction of the sulfur atom at C-3 via a bromomagnesium thiolate addition to the exo face of anhydroecgonine, separation of C-2 diastereomers, recycling of a C-2 thio ester byproduct, and formation of the necessary C-2 methyl and C-3 benzoylthio esters. Effects resulting from the lower electronegativity and greater hydrophobicity of sulfur compared to oxygen were observed. These characteristics could result in interesting drug properties. Furthermore, the analogue was found to be a substrate for catalytic mAbs that hydrolyze cocaine as monitored by HPLC and also spectrophotometry by coupling cleavage of the benzoylthio ester to the disulfide exchange with Ellman's reagent. Screening antibody libraries with the new cocaine analogue using the spectroscopic assay provides an avenue for the high-throughput identification of catalysts that efficiently breakdown cocaine.