MOLECULES DERIVED FROM MECHANISM BASED DRUG DESIGN

Abstract: A method for identifying molecules and designing novel pharmaceuticals is disclosed. The disclosed method of novel pharmaceutical design identifies a novel chemical group that triggers a mechanism of action for an identified reaction, thereby avoiding the various structural complexities associated with the application of the structure-based drug design. Additionally, examples of potential therapeutics identified by the mechanism based drug design method are provided.

Description: MOLECULES DERIVED FROM MECHANISM BASED DRUG DESIGN TECHNICAL FIELD OF THE INVENTION The field ofthe invention generally relates to a mechanism-based drug design system and methodology for identifying small molecules, in particular those that can be developed into pharmaceutical compounds BACKGROUND OF THE INVENTION The search for pharmaceutical agents to combat diseases is an ongoing process Several approaches to identify pharmaceutical agents are currently used (i) random drug screening, (ii) rational drug screening, and (iii) structure based drug design. Each method has its own set of advantages and disadvantages depending on the amount of information and resources available Random drug screening is the process by which a large number of molecules are tested in an assay to determine activity Although very little information about the molecular target or its agonist is required to successfully use this method, the investment of time and resources is high because ofthe extensive number of compounds needed to be synthesized and assayed for activity As a consequence, random drug screening is practiced almost exclusively by large commercial entities, although implementation of robotics for high throughput screening and synthesis of chemical libraries by combinatorial methods have made this a less expensive process (see Gallop, et al , "Applications of combinatorial technologies to drug discovery, background and peptide combinatorial libraries," J Med Chem 37 1233-50 (1994)) However, the tradeoff for easier screening and greater availability of compounds is the identification of more lead compounds, which must undergo further experimentation to determine clinical viability, thereby increasing the expense ofthe entire process Although software is being developed to analyze drug leads for pharmacokinetic profiles, there exists a need for drug discovery methods that begin with a smaller number of drug leads To effectively use the rational drug screening method, a ligand providing desired effects must be known and an effective assay developed In this method molecules with similar structural or chemical properties as the target ligand are synthesized and screened in an activity assay. The advantage of this method over the random drug screening method is that potentially fewer compounds must be screened. The disadvantage, however, is that more information must be known about the ligand, and preferably its target site, before a lead compound can be identified. A method requiring even more a priori knowledge before it can be used effectively is structure-based drug design (SBDD). The premise of this method is that potent pharmaceuticals possess significant structural and chemical compatibility to their target site. Thus, an understanding ofthe principles of molecular recognition in the target protein-ligand complexes is important for employing SBDD. To use SBDD, the target must be identified and its three- dimensional structure solved. (Hans- Joachim Bohm and Gerhard Klebe, "What can we learn from molecular recognition in protein-ligand complexes for the design of new drugs? " Agnew Chem Int Ed Engl 35: 2588-2614 (1996)). The application of SBDD has already assisted in providing several successful pharmaceutical products. For example, the enzyme inhibitor dorzolamide, which has been approved by the FDA for treating glaucoma, was the first approved pharmaceutical where the methods of structure-based drug design significantly contributed to its discovery. Computers and software play pivotal roles in SBDD because they generate graphic representations of three-dimensional structures of proteins and protein- ligand complexes to identify essential interactions. In addition, software that searches for additional binding sites not used by previously known ligands can also be used. For example, possible ligand binding sites might be positions where hydrogen bonds can be formed with an enzyme(s), or hydrophobic pockets in the enzyme structure. Moreover, a number of computational tools have been described to select putative ligands and to predict their interactions with the protein. In general, these tools for ligand design can be divided into the categories that follow: 1) analysis ofthe protein structure, 2) ligand docking and three-dimensional database searching, 3) de novo ligand design, 4) assessment ofthe ligand binding affinity, and 5) analysis ofthe ligands electronic and conformational properties of the ligand Several of these categories for designing ligands using a computer are described in the Agrafiotis patents (U S Patent No 5,684,711 and 5,901,069) In Agrafiotis, the computer generates chemicals with defined physical, chemical and/or bioactive properties For example, the computer employs a process wherein each iteration ofthe process includes (1) the generation of a diverse chemical library, (2) analysis of such compounds in the chemical library having desired properties, (3) the implementation of structure-property data to select compounds to be synthesized, and (4) the generation of new synthesis instructions to control the synthesis ofthe diverse chemical library for the next iteration More specifically, each cycle ofthe process described in the Agrafiotis patents begins with a robotically synthesized diverse chemical library comprising numerous chemical compounds, which are then analyzed to obtain structure- activity/structure-property data. The data is stored in a database that contains the structure-activities and structure-properties of previously synthesized compounds The computer evaluates the structure-activity and structure-property data of chemical compounds obtained from previous iterations and constructs structure- activity/structure-property models that substantially conform to the observed data The computer, using a reagent database, can then generate compounds to be tested and evaluated for having the desired pharmaceutical properties Additional patents involving the use of computer simulation for a rational drug design methodology are the Balaji patents (U S Patent Nos 5,579,250 and 5,612,895) The Balaji patents describe a method of rational drug design capable of identifying bioactive peptidomimetics that can be effectively used as drugs The method includes (1) the use of a computer to simulate the most probable conformation of a given polypeptide, (2) the simulation and design ofthe most probable conformation of a chemically modified analog of a peptide, (3) the evaluation of the activity of the synthesized chemically modified analog, and (4) the potential design of a suitable peptidomimetic based on the confirmation ofthe synthesized chemically modified analog. To predict the most probable tertiary structure ofthe peptide, the Balaji patents introduce the "ab initio" method, which is used to simulate a tertiary structure of a protein in the absence of physical or chemical data. The results of the "ab initio" calculations indicate the most probable conformation of such a peptide. Additionally, the Balaji patents introduce an analytical tool referred to as the "Balaji Plot," which is automatically generated when performing the "ab initio" method. The "Balaji Plot" can assist in determining the sequences of flexible and rigid areas in peptides or peptidomimetics, and provides insight as to how rigid, constrained or flexible peptide analogs should be modeled by computer programs. Although SBDD has emerged as a useful methodology to identify potential molecular reactions between a target site and a proposed pharmaceutical, the use of SBDD has been limited by the large amount of a priori knowledge needed to effectively use it. The novel design methodology described herein focuses on the mechanism of action of proteins (e.g. enzymes) to determine the "trigger" mechanism that drives a particular reaction. Pharmaceuticals can be designed from identified trigger mechanisms. By designing a compound around the trigger mechanism of action rather than molecular interactions at a defined loci, potent, low molecular weight target-specific compounds can be rapidly produced. Examples of such compounds are also disclosed. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 depicts a free energy diagram illustrating the action of a substrate - enzyme complex (-), an inhibitor - enzyme complex ( — ), and an enhancer - enzyme complex ( ). FIG. 2 depicts a flow chart for determining the trigger mechanisms for enzymes as they relate to a particular substrate. SUMMARY OF THE INVENTION One aspect ofthe invention includes a molecule comprising a minimal quantity of atoms to trigger a desired reaction wherein the molecule is designed by the steps of (a) determining the minimal quantity of atoms to trigger a desired reaction to occur, the minimal quantity of atoms collectively comprise the trigger mechanism for the desired reaction, and (b) positioning the minimal quantity of atoms on a ligand wherein the molecule can trigger the desired reaction independently from the naturally occuring desired reaction In yet another aspect ofthe invention includes a molecule comprising a minimal number of atoms for inhibiting a mechanism of action of a given reaction wherein the molecule is designed by the steps of. (a) determining the trigger mechanism ofthe given reaction; and (b) positioning the minimal number of atoms on a ligand wherein the ligand comprises an atom that functions as a poor leaving group when the molecule interacts with a reactant ofthe given reaction, thereby causing the molecule to inhibit the mechanism of action ofthe given reaction Examples of such molecules are as follows wherein B can be any basic group, and R can be any functional group, and x can be any atom or group that is more electronegative than sp 2 carbon, wherein B can be any basic group, Ri and R 2 can be any functional group; and x can be any atom or group that is more electronegative than sp carbon, wherein x can be any atom or group that is more electronegative than sp carbon; Ri and R are any functional group; and y is any proton donating group;and X II ■C- ■ Rι B wherein B can be any basic group;Ri and R 2 can be any functional group; and x can be any atom or group that is more electronegative than sp 2 carbon. In yet another aspect ofthe invention a system for developing a small molecule is provided wherein the system comprises: (a) a method to compare the stabilization energies of a given reaction between a catalytic residue of an enzyme to residues of a substrate to determine the trigger mechanism for the given reaction; (b) a minimal amount of atoms comprising the trigger mechanism ofthe given reaction; and (c) a ligand wherein said minimal amount of atoms are positioned on said ligand to form said molecule. Examples of such molecules include the minimum quantity of atoms to either inhibit or enhance the given reaction. In yet another aspect ofthe invention a method for determining the trigger mechanism of a given reaction is provided wherein the method uses a matrix involving the steps of: (a) performing ab initio calculations on a class of enzymes to compare a reactive residue associated with a catalytic site common to the class of enzymes to a reactive residue with one or more substrates associated with the class of enzymes; (b) using the information generated from step (a) and performing further ab initio calculations on a subclass of enzymes by comparing further reactive residues associated with the catalytic site common to the subclass of enzymes with one or more substates associated with the subclass of enzymes; (c) using the information generated from step (b) and performing further ab initio calculations on a single enzyme from the subclass of enzymes by comparing all reaction residues associated with the catalytic site of the enzyme with one or more substrates associated with the enzyme; and (d) using the information generated from step (c) to determine the trigger mechanism for the enzyme. In yet another aspect ofthe invention a method for determining a trigger mechanism for a given reaction is provided comprising the steps of: (a) performing ab initio calculations to determine the stability of each potential interaction between each active site residue of an enzyme and a chemical moiety of one or more substrates of said enzyme; (b) analyzing the calculated stabilization energies, wherein the most negative energies are the most reactive species and the most positive energies are the least reactive species; and (c) combining the chemical moieties that were calculated to be the most reactive, or the least reactive, with each corresponding catalytic residue on a compound scaffold. In yet another aspect ofthe invention a method for deteriming the trigger mechanism of a given reaction is provided comprising the steps of: (a) aligning a protein sequence of an enzyme with other proteins and determining by homology the general class ofthe enzyme; (b) performing biochemical assays to determine the reaction performed by the enzyme; (c) performing site-directed mutagenesis of conserved amino acids and determining if the mutated residues act in the reaction mechanism; (d) determining the mechanism of catalytic action for the enzyme; and (e) performing ab initio calculations to determine the stability of each potential interaction between each active site residue ofthe enzyme and a chemical moiety of one or more substrates of said enzyme. In yet another apsect ofthe invention a method for designing a small molecule that interacts with the active site of a certain enzyme is provided comprising the steps of: (a) aligning the protein sequence ofthe enzyme with other proteins and determining by homology the general class of enzyme; (b) performing biochemical assays to determine the reaction performed by the enzyme; (c) performing site-directed mutagenesis of conserved amino acids and determining if the mutated residues act in the reaction mechanism; (d) determining the mechanism of catalytic action for the enzyme; (e) performing ab initio calculations to determine the stability of each potential interaction between each active site residue ofthe enzyme and a chemical moiety of one or more substrates of said enzyme; (f) analyzing the calculated stabilization energies, wherein the most negative energies are the most reactive species and the most positive energies are the least reactive species; and (g) combining the chemical moieties that were calculated to be the most reactive, or the least reactive, with each corresponding catalytic residue on a compound scaffold. Examples of such molecules contain a minimum quanty of atoms that can inhibit or enhance a given reaction. In yet another aspect ofthe invention a molecule comprising a minimal quantity of atoms to inhibit the activation of telomerase is provided wherein said molecule comprises a poor leaving group. In yet another aspect ofthe invention a molecule comprising a minimal quantity of atoms to inhibit the activation of mycothiol s-conjugate amidase is provided wherein said molecule comprises a poor leaving group. DETAILED DESCRD7TION OF THE INVENTION The mechanism-based drug design technology (Quantum Core Technology™) ofthe present invention is a system and method for obtaining novel molecules that can function as pharmaceuticals or undergo modification to act as pharmaceuticals. The molecules obtained by this technology are small and specific to the target of interest, making them more likely to possess low toxicity. Because the majority ofthe designed compounds are based on the trigger mechanism (as discussed below) of a specific enzyme, the enzyme is not likely to evolve resistance to the molecules. The disclosed invention can also be used to design enzyme - inhibiting as well as enzyme - enhancing compounds. The method and system ofthe invention takes into account the four steps of enzymatic catalysis. First, in the inactive state ofthe enzyme, the spatial conformation ofthe catalytic residues do not allow interaction with another. Next, the substrate interacts with the enzyme to form an enzyme substrate complex (E - S complex). The E - S complex consists of numerous noncovalent interactions between the active site residues and the substrate. As the number of such nonconvalent interactions increases, the greater the E - S binding energy becomes. Third, the formation ofthe E - S complex activates the catalytic machinery ofthe enzyme by inducing a change in the spatial conformation ofthe catalytic residues. This change allows the catalytic residues to react with the substrate and catalyze the chemical reactions, a process referred to herein as "triggering." For proteins, the binding of a specific molecule to a protein triggers its transformation from an inactive state to an active state in which it can interact specifically with other proteins, DNA or RNA. Finally, after the substrate is converted to product and released, the enzyme returns to the inactive confirmational state, without having been consumed or altered in the reaction. To further illustrate the invention described herein, FIGs. 1 -2 are provided to assist in teaching the invention. Each figure is, however, merely for the purpose of illustrating the invention by way of example. Thus, it is to be expressly understood that FIG. 1-2 are for illustration purposes only, and therefore not intended, in any fashion, to be a definition ofthe limits ofthe invention. FIG. 1 is a free energy diagram that thermodynamically describes enzyme catalysis and inhibition. When an enzyme (E) is inactive, the spatial conformation ofthe catalytic residues do not allow interaction with one another. However, in the presence of a substrate (S), the enzyme begins to rearrange as numerous noncovalent interactions between the active site residues and the substrate form, which are indicated by the small peaks and valleys in the leftmost portion ofthe diagram. The binding energy between the enzyme and the substrate increases as the number of interactions increase, leading to a stabilized enzyme - substrate complex (E+S), depicted by the small valley just before the large peak in the diagram. The formation ofthe E+S complex allows the catalytic residues to react with the substrate and to begin the catalysis reaction by performing any ofthe functions that follow: spatial rearrangement, form a particular electronic state, form intramolecular hydrogen bonds, or perform an internal proton transfer. The role ofthe catalyst is to lower the energy activation barrier so that the reaction can proceed. After the reaction, the enzyme releases the products (P) at a lower energy state. As a hypothetical example, the E+S complex may have an energy barrier as depicted by the solid line. An enzyme inhibitor (I) increases the energy barrier needed to overcome to perform a reaction, as shown in the dashed - dotted line. A molecular trigger (T), defined herein below, decreases the energy barrier needed to overcome to perform a reaction, as shown in the dotted line. Unlike SBDD, in which molecules are designed to bind more strongly to the enzyme or compete with the substrate for active site binding, the present invention identifies a molecule that acts to initiate the reaction of an enzyme independent from the enzyme carrying the reaction trigger. The trigger for a reaction is the internal rearrangement that must be satisfied in order for the enzyme to form the reactant complex, which will lead to a reaction along the path catalyzed by the enzyme. The direct activation ofthe enzyme by the molecular trigger bypasses the need for multiple noncovalent interactions that typically occur in the natural enzyme activation process. Molecular triggers will reach the reactive state more readily than the native substrate due to either the energetic or kinetic processes involved. A successful drug or compound incorporating a molecular trigger will often form this initial complex more quickly or energetically more favorably than the native substrate, but will not complete the reaction because a suitable leaving group is lacking. The same can be applied to proteins which are not enzymes. For example, molecular triggers can be identified for reactive, non-enzymatic proteins. In this instance, a trigger can be identified that induces a conformational change leading to an allosteric effect or signal activation. In general, the method and system ofthe invention can employ known information about an enzyme target. The novel system and method ofthe present invention is depicted at 100 in FIG. 2. FIG. 2 is a flow chart depicting the preferred steps ofthe methodology for determining the trigger molecules of an enzyme. These preferred steps include: (1) developing a general classification of enzymes according to their reaction types 110, (2) deriving general categories of chemical reactions that enzymes undergo 120, (3) analyzing the enzymatic reaction and extracting the role ofthe enzyme's chemical functionalities 130, (4) deriving simple chemical reactions 140, and (5) deriving from the reaction the trigger mechanism for each enzyme class 150. It should be noted that in most instances steps 1 and 2 can be overlooked if the enzyme being examined has previously been classified. To derive the molecular trigger, "ab initio" calculations are performed for each square of a two-dimensional matrix and the calculated stabilization energies are analyzed. An example ofthe two-dimensional matrix is provided at Table I. As previously discussed, the preferred first step ofthe invention is to classify a target enzyme according to its reaction type, which is depicted at 110 in FIG. 2. According to the Commission on Enzymes of the International Union of Biochemistry, enzymes are currently classified into six general groups according to their performed reaction. For example, enzymes in the hydrolase class catalyze a hydrolysis reaction. The enzymes can be further classified according to their biological function and/or preferred substrates. Several databases exist that include an extensive amount of information about enzymes as they relate to their designated class. For example, see Enzymes.htm at <http://crisceb.area.na.cnr.it/angelo/petrilli/ enzymes/intor.htm> or ExPASy- Enzyme.htm at http://www.expasy.ch/cgi-bin/nicezyme.pl72.3.1.43. The enzyme reaction classifications recognized by the Commission on Enzymes ofthe International Union of Biochemistry are provided in Table II below. Ascertaining the reaction classification of an enzyme can be accomplished with methods established in the art. Oftentimes, the reaction type of an enzyme is already known or can be easily identified from the published sequence ofthe enzyme. If this is not the case, there are methods in the art to ascertain particular aspects of an enzyme if they are not currently known. For example, the reaction an enzyme catalyzes can be determined by performing enzyme assays, which are known to those skilled in the art. (G. Sarath, R.S. de la Motte and F.W. Wagner. In Proteolytic Enzymes: A Practical Approach, ed. RJ. Beyon and J.S. Bond, IRL Press, 1990, p. 25). If the enzyme of interest has not been previously isolated and/or characterized, it can be isolated using a variety of techniques commonly practiced by biochemists. The enzyme can then be subjected to amino acid sequence analysis and the DNA sequence analyzed for the enzyme cloned with t ^J Table II: Enzyme Classifications by Commission on Enzymes ofthe International Union of Biochemistry techniques commonly known to persons practicing in the field of molecular biology (See Short Protocols in Molecular Biology, 2d. ed. , John Wiley & Sons (1992), which is incorporated herein by reference. To determine the DNA sequence ofthe target protein, the method discussed in Wilhelm Arronage, DNA Sequencing Strategies, Automated and Advanced Approaches, ISBN 0971136832 (S. Zimmerman, ed.), which is also incorporated herein by reference, is preferred. The determined DNA and amino acid sequences ofthe enzyme can be compared for homology to other known sequences of classified enzymes having an identified tertiary, or preferably quaternary structure. These higher level structures of enzymes are located in the Protein Data Bank ofthe Brookhaven National Laboratory. If there is no available quaternary structure for the enzyme of choice, but it is highly homologous to other enzymes, the three - dimensional structure of the studied enzyme can be modeled onto the solved structure. Additionally, if the enzyme is not identified in existing databases, the reaction it catalyzes can be determined by performing enzyme assays, which are known to those skilled in the art. Examples of such enzyme assays use natural or synthetic substrates for spectrophotometric or fluorimetric assays to characterize enzymes. (G. Sarath, R.S. de la Motte and F.W. Wagner. In Proteolytic Enzymes: A Practical Approach, ed. RJ. Beyon and J.S. Bopand, IRL Press, 1990, p. 25). After an enzyme has been classified according to its reaction, the next preferred step is to derive the general category of chemical reaction the enzyme undergoes. This step occurs at 120 in FIG. 2. For example, if the enzyme is a protease, the chemical reaction would be a hydrolysis. On the other hand, if the enzyme is an amidase, the chemical reaction would be a deamination. After categorizing the chemical reaction an enzyme undergoes, analysis to identify the mechanism of action ofthe enzyme is performed, which is represented as 130 in FIG. 2. The foundation for determining a reaction mechanism is based on organic chemistry and biochemistry. Furthermore, application of energetic principles (e.g., Gibb's free energy principle) and electronic properties ofthe various molecules involved in the enzymatic reaction can assist in determining the mechanism of action. By identifying the active site residues, one can begin to understand the enzyme's mechanism. Criteria that active site residues satisfy are listed below: 1) active site residues are present in all known examples of the particular class of enzymes; 2) Modification ofthe active site residues yields a debilitated enzyme; 3) Within the three dimensional structure ofthe enzyme, the active site residues are often closely situated; and 4) Within the three-dimensional structure ofthe enzyme, the active site residues are inside a groove or pocket and the orientation ofthe active residues allows them to interact with the substrate at a location consistent with the enzymes overall function. Beyond identifying the active site residues, the mechanism of an enzyme can be described by a plausible chemical reaction, or series of reactions, that show how the active residues and substrate undergo a reaction consistent with the known function ofthe enzyme. Data that describes the kinetics ofthe enzyme's reaction can be analyzed to determine if it is consistent with a hypothesized mechanism. Additionally, analysis ofthe thermodynamics of a hypothesized reaction can indicate whether a hypothesized mechanism is valid. "Ab initio" calculations can be used to assist in generating a model reaction. "Ab initio," which in Latin means "first principles," is a calculation procedure. The distribution of electrical charge, a molecular wave function, and various molecular properties can be determined using "ab initio" calculations. Examples of molecular properties include: stabilization energies, orbital energies, electronic properties, chemical properties, heats of formation, dipole moments, and intermediate stabilities. Chemical properties can also be predicted using "ab initio" calculations. Thus, "ab initio" calculations performed on a model reaction mechanism can be used to simulate the most favorable reaction mechanism ofthe target protein so to further define the most probable reaction (W.J. Hehre, L. Radom, P.N.R. Schleyer, and J.A. Pople. Ab Initio Molecular Orbital Theory, Wiley (1986)). The reaction having the more negative free energy value will demonstrate the more stable reaction intermediate because it requires the lowest amount of energy for the reaction to occur. In other words, the most labile reaction will possess the most negative free energy. Preferably, the "ab initio" calculations are performed with the assistance of a computer employing the Gaussian Series of Programs (University of California at San Francisco). Once the reaction mechanism has been determined, the next preferred step is to derive the trigger molecule for an enzyme. This step is illustrated at 150 of FIG. 2. Because enzymes are classified according to their reaction type and mechanisms, the triggers for enzymes of a particular class are likely to be similar. For example, the 3C protease from the picornavirus family and human caspase are both proteases that have only cysteine and histidine as their catalytic residues and so could be triggered by similar molecules. Triggers are identified using "ab initio" calculations. In order to analyze "ab initio" calculations to determine the molecular trigger, a two-dimensional matrix is developed to calculate the stabilization energy ofthe resulting products relative to the reactants. An example of such a two- dimensional matrix to determine the molecular trigger of cysteine proteases is provided in Table II. The x-axis ofthe matrix represents all the key chemical moieties on the catalytic residues of the enzyme in its resting state. The y-axis represents all reactive moieties of known substrates and inhibitors. The free energy for each potential interaction between two moieties is calculated using "ab initio" calculations (described above) in a reliable basis set representing consistent assumptions about the interactions. The reliable basis set is selected on the grounds that it yields energies and energy differences that are close to the experimental value. A preferred basis set is HF/6-3 l+G*//HF/6-31G*, which can be obtained by using programs such as Gaussian (Guassian Corp.), Q-chem (Q-Chem), and Spartan (Wavefunction). The "ab initio" calculations can be used to determine which ofthe chemical functionalities are likely to be inhibitors or enhancers for a particular enzymatic reaction. For example, a strong inhibitor interacting with an enzyme will decrease the negative free energy value, thereby making the reaction thermodynamically less favorable. Unlike an inhibitor, an enhancer will bind the enzyme with a large negative free energy value. By calculating all ofthe possible combinations in the matrix, the combination representing the most favorable reaction for a specific reaction can be determined. Example 1 : How Mechanism Based Drug Design Can Identify Reactive Molecules to Modulate Serine Proteases Proteases are part ofthe hydrolase class of enzymes, which are selected from the enzymatic class having the general reaction equation that follows: ROR' + enzyme + H20 — ROH + R'OH The protease family is selected from the enzymatic class having the general reaction equation of: R-CONHR' + enzyme + H20 — > RCOOH + R'NH2 Generally, the protease family consist of four major classes: serine proteases, cysteine proteases, aspartic proteases, and metalloproteases, each so named for the enzyme component believed to be critical for catalysis. Table I shows an example of a matrix constructed for determining the most probable (favorable) reaction between the reactants in the x and y axis using "ab initio" calculations. The x axis ofthe matrix includes all key catalytic residues of the proteases, while the y axis represents all possible substrates and inhibitors for the different types of reactions within the protease family. The resulting energies ofthe products are compared for inhibition and activation. Candidate inhibitors having the best stabilization energies and inhibition are selected. The matrix can be further expanded to include general acid base reactions relevant to all hydrolases. This version ofthe matrix includes a large variety of substrates. Examples include organic phosphates, carbohydrates, fatty acid esters, several amides, esters, epoxides, nucleic acid bases, etc. The results of "ab-initio" calculations for the different constituents of each protease provides for a large selection of potential core molecules. Again, by focusing on the stabilization energies calculated for the products ofthe various reactant combinations, a potential modulator can be located by selecting the products having the best stabilization energies. For example, the triggers for serine proteases, aspartic proteases, metalloproteases, and cysteine proteases were determined using "ab initio" calculations and quantum mechanic principles as previously discussed. The triggers for the various proteases are as follows: (1) the serine protease trigger involves the removal of a hydrogen from the serine residue, which allows the serine anion to then attack the electorphile as illustrated below: me wherein B = any basic group; R = any functional group; and X = any atom or group more electronegative than carbon; (2) the aspartic protease trigger involves the removal of a hydrogen from a water molecule to form a hydroxy anion, which can then attack the sp as shown below: wherein X = an atom or group more electronegative than the sp carbon; R = any functional group; and B = any basic group (3) the metalloprotease trigger involves the removal of a hydrogen from a water molecule to form a hydroxy anion, which can then attack the sp2 carbon as shown below: wherein X = an atom or group more electronegative than the sp carbon; R = any functional group; and B = any basic group; and (4) the cysteine protease trigger involves the addition of a proton to the X position (carbonyl in native substrate), which can augment or replace the oxyanion hole. This allows the cysteine to attack the carbon atom as shown below: Enz V me wherein X = an atom or group more electronegative than the sp 2 carbon, R, R' = any functional group, and Y = a proton donating group Example 2 Determining the trigger mechanism for a serine protease Quantum Core Technology™ has been used to identify reactive chemical moieties that triggers or inhibits a serine protease Activators and inhibitors were desired to target an exemplary serine protease The method employed for the process of identifying the chemical moieties is provided herein These steps are the preferred methods for isolating the triggers of a serine protease and are presented for the mere purpose of teaching others skilled in the art to use the invention described herein and are not to be construed as limitations to the invention. The first step ofthe QCT™ method is to develop a general classification of a chosen enzyme according to its reaction type. The amino acid sequence ofthe exemplary serine protease was procured from an enzyme database. A preferred database is Swiss Prot, although if the sequence for the exemplary serine protease was unknown, it could be determined through methods provided herein by identifying the DNA sequence and applying the genetic code dictionary The sequence ofthe exemplary serine protease sequence was aligned to other serine proteases. A source of known sequences, the Protein Data Bank at the Brookhaven National Laboratory possesses categories of known enzymes in the serine protease class. If it has been solved, the three - dimensional structure ofthe exemplary serine protease can also be found at the Protein Data Bank at the Brookhaven National Laboratory If the structure ofthe exemplary serine protease has not been solved, it can be accomplished using methods known in the art of x- ray crystallography and /or nuclear magnetic resonance (NMR). In order to derive the general category of chemical reaction that the exemplary serine protease undergoes, its three - dimensional structure was compared to those of other known serine proteases and found to be at least 20% homologous A homology model of the exemplary serine protease was then constructed using the homology module of MSI Software Package (MSI Molecular Simulations, San Diego, CA) Although the homology module of MSI Software Package was the preferred method for constructing the homology model, there are other suitable programs including MDL, Tripos, and Oxford Molecular. Once the model ofthe exemplary serine protease was created, it was analyzed using the MSI Software Package to extract the role ofthe exemplary serine protease' s chemical functionalities. The simulation software provided a three-dimensional view ofthe serine protease of interest and the ability to enlarge the amino acid residues homologous to the known serine proteases. The catalytic residues ofthe active site ofthe exemplary serine protease were compared to the catalytic residues ofthe active sites of other known serine proteases to determine the mechanism ofthe protein of interest. In addition, the catalytic residues ofthe exemplary serine protease can also be analyzed by comparing the alignment ofthe amino acid sequences of various serine proteases and identifying the extent of conservation of specific catalytic residues at the active sites. Only amino acids that are conserved within all species ofthe serine proteases are the actual catalytic residues. Site-directed mutagenesis ofthe conserved catalytic residues can be performed to confirm that the conserved residues play significant roles in triggering the protease of interest. A preferred methodology for performing site- directed mutagenesis is discussed in Weiner, M.P., Gackstetter, T., Costa, G.L., Bauer, J.C., and K. A. Kretz, Molecular Biology: Current Innovations and Future Trends, A.M. Griffin and H.G. Griffin (eds), 1995 which is incorporated herein by reference. Once the catalytic residues were ascertained, simple chemical reactions were derived comprising the catalytic residues ofthe active site and a chemical model was constructed. Construction ofthe chemical model was done by taking only the functional chemical groups and placing them in the proper spatial conformation, which is suggested by the homology model ofthe exemplary serine protease. The serine protease mechanism involves charge relay between the three members ofthe catalytic triad, resulting in the activation ofthe serine nucleophile. A model demonstrating the trigger mechanism is as follows: Resting State of the Serine Protease: Serine Histidine Aspartic Acid Substrate Introduced Substrate Released: Serine Histidine Aspartic Acid As one can see, the essence ofthe serine protease mechanism is the activation ofthe catalytic serine nucleophile by the extraction of a proton from its hydroxyl group, which forms an intensely charged hydroxyl anion. The formation ofthe charged hydroxyl anion results from a charge relay mechanism wherein the histidine extracts the proton from the hydroxyl ofthe serine and the aspartic acid residue extracts the hydrogen ofthe histidine, thereby making the histidine residue neutral. Furthermore, an additional factor that facilitates the nucleophilic attack of the hydroxyl anion on the carbonyl is the presence of an oxyanion binding site. The oxyanion site, which is depleted by the two amino groups, is a narrow hole in which the oxygen ofthe carbonyl ofthe substrate enters during the formation of the enzyme substrate complex. In the oxyanion binding site, multiple hydrogen bonds form with the oxygen ofthe substrate's carbonyl, thereby polarizing the C=O bond, which provides for a greater positive charge to the carbonyl ofthe substrate. The greater positive charge on the carbonyl further facilitates the nucleophilic attack ofthe hydroxyl anion ofthe serine residue to the carbonyl carbon ofthe substrate. Because the mechanism ofthe exemplary serine protease was understood, "ab initio" calculations were made next for various combinations of reactants to determine the stabilization energies of each potential tetrahedral complex and therefore the trigger ofthe protease. The reactions involving a more negative stabilization energy are more likely to represent possible moieties for activators. The activating chemical functionalities provide the trigger mechanism ofthe serine protease because even an uncharged serine OH group can serve as a nucleophile and bypass the need for the charge relay process. As an example, "ab initio" calculations regarding the anionic transition complexes of exemplary serine proteases are illustrated in Table III below. Table III: Ab initio 6-31+G*/3-21G* calculated stabilization energies E st of Tetrahedral Complexes a The E st for the F(OH) 2 P=O was estimated from the reaction equation: HO + F(OH) 2 P=O^ (HO) 2 PO 2 - + HF An example for a typical reaction is the following: OH- + H(NH 2 )C=O→- OH(H)(NH 2 )C-O- Using these results from Table III, all factors important to the stabilization ofthe transition state ofthe reaction or the rate determining step ofthe reaction were analyzed. The most important determination from this analysis occurred in the bond between the oxygen ofthe serine protease and the carbonyl carbon ofthe formamide. As this bond increased in strength, the catalysis ofthe serine protease was enhanced. Therefore, the trigger for serine protease is the activation ofthe hydroxyl group on serine to form a hydroxyl anion. Based upon the application of principles of organic chemistry and the above "ab initio" calculations, triggering chemical moieties were determined for the exemplary serine protease. Example 3: How Mechanism Based Drug Design Can Identify Reactive Molecules to Modulate Cysteine Proteases The Quantum Core Technology™ described in the general methodology has also been employed to identify chemical functionalities that trigger or inhibit cysteine proteases. The following preferred methodology is for the mere purpose of teaching others skilled in the art to use the invention described herein. The following process has exemplary steps for identifying triggering functionalities for an exemplary cysteine protease. The first step ofthe QCT™ method is to develop a general classification of a chosen enzyme according to its reaction type. The amino acid sequence ofthe exemplary cysteine protease was determined through using the database Swiss Prot. If the sequence for the exemplary cysteine protease had not been known, it could have been determined using techniques known to those skilled in the art. The cysteine protease sequence determined from the Swiss Prot database was then aligned to other cysteine proteases whose sequences were available in databases. The exemplary cysteine protease was determined to be homologous to other known cysteine proteases. In order to derive the general category of chemical reaction that the exemplary cysteine protease undergoes, its three - dimensional structure was compared to those of other known cysteine proteases. A model was constructed for the exemplary cysteine protease with the structure of a cysteine protease that was at least 20% identical using the homology module of MSI Software Package (MSI Molecular Simulations, San Diego, CA). Although the homology module of MSI Software Package was the preferred method for constructing the homology model, there are other suitable programs including MDL, Tripos, Oxford Molecular, and Molecular Operating Environment. Once the model ofthe exemplary cysteine protease was created, it was analyzed using the MSI Software Package, which provided a three-dimensional structure of the protein and the ability to enlarge the amino acid residues homologous to the known cysteine proteases. The catalytic residues ofthe active site ofthe exemplary cysteine protease were compared to the catalytic residues of other known cysteine proteases to determine the mechanism ofthe protease. In addition, catalytic residues ofthe exemplary cysteine protease can also be analyzed by comparing the alignment of the amino acid sequences of various cysteine proteases and identifying the extent of conservation of specific catalytic residues at the active sites. Only amino acids that are conserved within all species of cysteine proteases are catalytic residues. Site-directed mutagenesis ofthe conserved catalytic residues can be performed to verify that the conserved residues play significant roles in the mechanism ofthe protease of interest. A preferred methodology for performing site-directed mutagenesis is discussed in Weiner, et al. (Weiner, M.P., Gackstetter, T., Costa, G.L., Bauer, J.C.,and K. A. Kretz, Molecular Biology: Current Innovations and Future Trends, A.M. Griffin and H.G. Griffin (eds), 1995). Once the catalytic residues were ascertained, simple chemical reactions were derived comprising the catalytic residues ofthe active site and a chemical modul was constructed. Construction ofthe chemical model was done by taking only the functional chemical groups and placing them in the proper spatial conformation, which was suggested by the homology model ofthe exemplary cysteine protease. "Ab initio" calculations for various combinations of reactants were then performed to describe the mechanism ofthe cysteine protease of interest. The reaction mechanism of cysteine proteases is distinct over the reaction mechanism of serine proteases. In serine proteases, the activation ofthe nucleophile occurs by a consecutive charge relay mechanism, wherein the histidine pulls a proton from the hydroxyserine and subsequently the aspartic acid pulls a proton from the histidine. In cysteine proteases, the cysteine-histidine pair exist as an ion-pair in the resting state ofthe enzyme. Consequently, the cysteine is already charged. "Ab initio" calculations demonstrate how the sulfur group ofthe cysteine protease is very different from the hydroxy group ofthe serine protease in their nucleophilic attack on a carbonyl group (Arad, et al. "A simulation ofthe sulfur attach in the catalytic pathway of papain using molecular mechanics and semi-empirical quantum mechanics," J Am Chem Soc, 112:491-502 (1990); Arad, et al., "Structural and mechanistic aspects of 3C protease from the picornavirus family," J Chem Infor Comp Sci 33 :345-349 (1993); Arad, et al., Organic Reactivity, Physical and Biological Aspects, 1995; Arad, et al. J Mol Modeling, (1996)). Reactions (i) and (iii), provided below, illustrate this difference where the lack of protonation on the carbonyl oxygen yields no tetrahedral structure. O θ I (i) OH Θ ^C - 'H -20 kcal/mol H 2 N H HO k NH 2 O II (ϋ) SH c v No tetrahedral structure H 2 N V H H- θ OH I (iii) Θ / C - Η SH C v HS^ l -20 kcal/mol H 2 N κ V H NH As in reaction (i), when the reaction of a hydroxy anion on formamide forms a charged tetrahedral structure, the product tetrahedral complex (TC) is 20 kcal/mol lower in energy (in the gas phase) than the sum ofthe reactants (the calculations are performed in the HF/6-3 l+G*//HF/6-31+G* level). The reaction with the sulfur (SH ' ) nucleophile on formamide has a completely different reaction potential surface. In this reaction (ii), the tetrahedral structure is not a minimum on the reaction potential surface. In order for the reaction to occur in a similar manner to the way it occurs in serine proteases, there has to be a protonation ofthe carbonyl. In reaction (iii), calculations performed on the same level (ITF/6- 31+G*//HF/6-31+G*) on the protonated set results in a similar reaction path to the one observed in serine proteases. In this ab initio study, it was shown that an early protonation ofthe substrate has to occur in order for the cysteine nucleophile to attack the peptide bond. Elsewhere (Arad, et al. "A simulation ofthe sulfur attach in the catalytic pathway of papain using molecular mechanics and semi-empirical quantum mechanics," J Am Chem Soc, 1 12:491-502 (1990)), it was shown that the group that actually provides the proton necessary for protonation ofthe substrate is the catalytic histidine. Thus, a proton is transferred from the catalytic histidine to the substrate prior to the nucleophilic attack by cysteine. Based on the above results, it appears that the catalytic histidine provides a proton which protonates the carbonyl ofthe substrate during the activation ofthe cysteine protease. This process enables the sulfur anion ofthe cysteine catalytic residue to attack the newly formed protonated carbonyl ofthe substrate, thereby forming the tetrahedral intermediate. The nucleophilic attack ofthe sulfur anion of the cysteine catalytic residue to the protonated carbonyl ofthe substrate is the rate determining step ofthe enzymatic reaction because this nucleophilic addition does not occur until the carbonyl ofthe substrate is protonated. The mechanism for cysteine protease thereby occurs as follows: Resting State of the Cysteine Protease: Charge Stabilization Cysteine Histidine Asparagine R - S ® HN-^ NH O^ v®v c — NH2 Substrate Introduced: e Interestingly, an oxyanion hole ofthe cysteine protease exists but is not sufficient to facilitate the nucleophilic attack ofthe sulfur anion to form the tetrahedral E - S structure. Therefore, full protonation ofthe substrate is needed. This protonation is done either by protonation ofthe carbonyl ofthe substrate or the nitrogen amide. In the instance where the nitrogen is protonated, the carbonyl is directed towards the oxyanion binding site. In the instance when the carbonyl is protonated, the carbonyl is directed towards the histidine. In order for the reaction to proceed, the carbonyl oxygen must be protonated before the nucleophilic attack by the cysteine, which is indicated by the results shown in Table I. The neutral acetamide (column 5), which is most similar to the native substrate, does not form a stable complex with the cysteine sulfur (row 6). However, the protonated form of acetamide (column 6) does form a stable complex with the cysteine' s sulfur (row 6). This table also indicates that the cysteine should be in the deprotonated form (row 6) rather than the neutral form (row 13) to form a stable complex. Thus, the protonation ofthe substrate and deprotonation ofthe active cysteine are prerequisites for the subsequent nucleophilic attack by the cysteine, which is in agreement with literature published about the reaction mechanism ofthe cysteine protease. Identifying substrate protonation as a trigger in the cysteine protease mechanism indicates that a functional motif capable of protonation would make a good activator. Making a compound with a hydroxy group close to the carbonyl would result in a self protonating compound by facilitating the transfer of a hydrogen from the carbonyl to the hydroxy group. The QCT™ methodology further encompasses a means for tuning, or modulating, the reactivity of an inhibitor or activator. Having established that the relevant portions for designing an inhibitor of Table I are row 6 and the columns for protonated species, the relative energies of these compounds can be examined. Those compounds possessing stronger binding energies than possessed by acetamide, such as propan-2-one, will bind more strongly in the active site than the native substrate. Table I, thus, indicates a number of molecular motifs that could be present at the active site for enhanced binding ability. This is further supported and quantified by the computation of charge separations (Table IV- A) and orbital energies (Table IN-B). With this information as guidance, a selection of structural motifs with some or all of these features can be computed, as shown in Table IN-C. Compounds of this size are expected to have some activity as inhibitors of many different cysteine proteases. The drug design process would then proceed to the addition of other functional groups that give specificity for a particular cysteine protease by binding to residues that are conserved across stereotypes, using the techniques of structure based drug design which are already well know to researchers in this field. The lead compounds could then be subjected to further testing for bioavailability and toxicity. The procedures described in Examples 1 and 2 have been repeated for aspartic proteases and metalloprotease to demonstrate the universality ofthe method for determining chemical functionalities that trigger an enzymatic reaction. The trigger for the aspartic proteases is the activation of a water molecule to form a hydroxide anion. The trigger for the metalloproteases is the metal activation ofthe enzyme nucleophile. More importantly, the QCT™ methodology can be applied to any enzyme or protein - ligand interaction. Table IN-A: Charge and bond length for cysteine and serine protease tetrahedral complex calculations. Tβbki 1. Electronic and gtonvttric characteristics of a stable TC. no. Tetrahedral Vaiaes of charge-transler Charges on reactiv* centers X-Afa,*] complex (TC) ait ϋύtio abu ' ώio MuUiken SAO MulWun. NλO eq. 2 X Λ X A 1 H0-CH,-O- 0.6417 0.5563 0.3720 -0.8337 0.2381 -05257 0.3584 1.470 2 HO-CE,-0- 0.6053 0.6343 0.3SS3 -0.8893 604 -0.8623 1.3537 1.396 3 Ho-ca-s- 0.7168 0.6261 0.4124 -0.7728 -0.0734 -0.8708 -0.2104 1.428 4 fKwαo-c-o- 0.6865 0.6107 0.3733 -0.8002 0.4608 -0.8818 0.6563 1.433 5 HO-(ΝH-)-C-0- 0.6618 0.5823 0-26S3 -0.8283 0.6777 -0.9073 0.9485 1.459 6 HCM H 2 >,C-S- 0.7S27 0.6401 0.3801 -0.7229 0.1OU -0.8654 0.4687 1.421 7 H0-SiH,- - 0.4639 0.2914 0.4207 -1.0296 1.1723 -1-2062 1.9172 1.705 8 HO-S«K,-5- 0.5670 0.314O 0.4346 -0.9354 0.8547 -1.1943 1.4206 1.692 9 HS-CF j -O- 0.3109 0.8634 0.3623 -0.2650 0.7802 -0.2492 1.0459 1.915 10 HS-CH.-S- 0.8*13 0.9634 0.3832 -0-2286 -0.4190 -0.1702 -0.7127 1.261 TT HS-(NK,),C-S- 0.8746 0.9669 0.3428 -0.2160 -0.0346 -0.1640 0.1308 1.897 12 HS-S-H,-0- 0.5673 0.4821 0.3959 -0-5042 0.8339 -0.6445 9S7 2.248 13 HS-SiH,-S- 0.6420 0.55731 0.4087 -0.4476 0.618S -0.5814 1.0107 2.225 Table 1V-B: Energies ofthe HOMO, LUMO, ionization potential, and electron affinity obtained by "ab initio" calculations. no. Coaφ. Ηn»to *tCMO 1 W A. la) 1 HO- -0.10333 0.41779 0.0589 -0.3902 2 HS- -O.09416 0J26O90 0.0660 -0.2444 3 CH j =0 -0.44295 0.07593 0.4046 -0.0577 4 Ov-O -0.55939 0.06644 0.5047 -0.0536 5 -0.35227 0.03559 0.3373 -0.0110 6 (CH>,00 -0.39286 0ΛS850 0.3593 -0.0498 7 (NH,) 2 C»0 -0.41446 0.06333 03762 -0.1722 8 {KH,) 2 C»S -0.31813 0.04853 0.2911 -0.0340 9 SiR,=0 -0.44595 0.02247 0.4075 -0.0098 10 SiH j =S -036239 0.COS49 0-3396 0.0079 Table IV C Cysteine Protease Inhibitor Matrix HF/6-31 +G Geometry Optimized in a u (hartrees) CH3S- TC Binding Protonated CH3S- TC Binding Electrophile Energy (a u (kcal/mol) Energy Energy (kcal/mol) Benzamide -398 5 NTC -398 8531 -836 1716 120 2370953 Benzoic acid methyl ester -457 36 NTC -457 6971 -895 0231 124 9245913 OH 4-Hydroxy- pent-3-en-2-one -343 73 NTC -344 0793 -781 4099 127 8487855 C4 attack -343 73 -780 8502 -6 62023 Acetamide -207 98 NTC -208 3232 -645 6607 1 32 1284003 Table IV C Cysteine Protease Inhibitor Matrix Continued HF/6-31 +G Geometry Optimized in a u. (hartrees) CH3S- TC Binding Protonated CH3S- TC Binding Electrophile Energy (a u ) (kcal/mol) Energy Energy (kcal/mol) 3-(3-Oxo-3-phenyl-propyl)- pyrrolidin-2-one -705.25 NTC -705.5931 ' -1 142 933 133 828951 1 Benzoic acid -418.34 NTC -418 6621 -856 0038 134 7764904 5-Oxo-5-phenyl-pentanoic acid amide -628 34 N JC -628 6856 -1066 033 1 38 2277927 Table IV C Cysteine Protease Inhibitor Matrix Continued HF/6-31 +G Geometry Optimized " in a u (hartrees) CH3S- TC Binding Protonated CH3S- TC Binding Electrophile Energy (a u ) (kcal/mol) Energy Energy (kcal/mol) acetophenone -382 49 NTC -382 8232 -820 1745 140 8068567 3-hydroxy- acetophenone -457 34 NTC -457 6761 -895 0318 143 5616234 4-Oxo-4-phenyl-butane- 1-sulfonic acid amide -10628 NTC -1063092 -1500452 1464544422 Table IV C Cysteine Protease Inhibitor Matrix Continued HF/6-31+G i Geometry Optimized in a.u. (hartrees) CH3S- TC Binding Protonated ι CH3S- TC Binding Electrophile Energy (a u.) (kcal/mol) Energy Energy (kcal/mol) 3 -chloroacetophenone -841.38 NTC -841 7125 -1279.073 146 774472 3-Acetyl- benzenesulfonamide -984.681 NTC -985.0098 -1422.371 147 0819517 3 -fluoroacetophenone -481.34 ' NTC -481.6683 -919.03 ' 147.30158 OH 4-Hydroxy-butan-2-one -305.86 NTC -306 1862 -743.5496 148.362071 1 zwitteπon form -305.86 -742.9554 -18 7814 Table IV C Cysteine Protease Inhibitor Matrix Continued HF/6-31 +G Geometry Optimized in a u (hartrees) CH3S- TC Binding Protonated CH3S- TC Binding Electrophile Energy (a u ) (kcal/mol) Energy Energy (kcal/mol) 3 -bromoacetophenone -392 67 NTC -392 9999 -442 5245 156 4067429 3 -nitro-acetophenone -585 96 NTC -586 2793 -1023 657 157 2538807 3,5-Difluoro-2-hydroxy- benzaldehyde -616 01 -1053 151 10 15938 -616 3176 -1053 705 163 5415259 C2 attack -616 01 -1053 121 -8 60316 -616 3176 -1053 649 128 1 186146 zwittenon form -615 98 -1053 163 33 61568 Table IV C Cysteine Protease Inhibitor Matrix Continued HF/6-31+G Geometry Optimized in a u. (hartrees) CH3S-TC Binding Protonated CH3S- TC Binding Electrophile Energy (a.u ) (kcal/mol) Energy Energy (kcal/mol) 2,2,2-Trifluoro- 1 -phenyl-ethanone -67907 -1116205 6595125 -6793724 -1116762 164871846 3 ,3 -Difluoro-4-hydroxy- butan-2-one -503.58! -940.71331 5.8672141 -503.88011 -9412743 167.7207392 zwittenon form -503.58! -940.6984' -3.53288 1, 1,1, 3,3,3 -Hexafluoro- propan-2-one -78512 -1222.284! 2417794ι -7853628 -1222831 2141689924 Example 4 Determining chemical functionalities that trigger the 3C protease ofthe cysteine protease family The QCT™ methodology has also been used to identify reactive chemical moieties that trigger or inhibit the 3C protease, a cysteine protease The 3C protease is a versatile viral protease responsible for most cleavage events within the viral polyprotein and is considered to be indispensable in the reproduction of several virus types Each step presented in the provided preferred methodology is for the mere purpose of teaching others skilled in the art to use the invention described herein The first step ofthe QCT™ method is to develop a general classification of a chosen enzyme according to its reaction type The amino acid sequence ofthe 3C protease was determined using the preferred database, Swiss Prot If the sequence for the 3C protease had not been known, it could have been determined by techniques known to those skilled in the art The 3C protease sequence determined from the Swiss Prot database was then aligned to other cysteine proteases to determine homology In order to derive the general category of chemical reaction that the 3C protease undergoes, its three - dimensional structure was compared to those of other known cysteine proteases, for example trypsin and kalekrein Because there was at least 20% homology between the 3C protease and known proteins whose structure had been solved, it was concluded that a homology model could be constructed The homology model was preferably constructed using the homology module ofthe MSI Software Package (MSI Molecular Simulations, San Diego, CA) Although the homology module of MSI Software Package was the preferred method for constructing the homology model, there are other suitable programs including MDL, Tripos, Oxford Molecular, and MOE The active site ofthe model of 3C protease was analyzed using the MSI Software Package, which has the ability to enlarge select amino acid residues To determine the mechanism for the 3C protease, the catalytic residues of the active site ofthe 3C protease were compared to the catalytic residues of other known 3C proteases In addition, the catalytic residues ofthe 3C protease can also be analyzed by comparing the alignment ofthe amino acid sequences of various 3C proteases and identifying the extent of conservation of specific catalytic residues at the active sites. Only the amino acids that are conserved within all ofthe 3C proteases are the actual catalytic residues. Site-directed mutagenesis ofthe conserved catalytic residues can be performed to verify that the conserved residues play significant roles in the mechanism ofthe 3C protease. A preferred methodology for performing site- directed mutagenesis is discussed in Weiner, et al. (Weiner, M P., Gackstetter, T., Costa, G.L., Bauer, J.C.,and K.A Kretz, Molecular Biology: Current Innovations and Future Trends, A.M. Griffin and H.G. Griffin (eds), 1995). Once the catalytic residues are ascertained, simple chemical reactions were derived comprising the catalytic residues ofthe active site. The chemical model was constructed by taking only the functional chemical groups and placing them in the proper spatial conformation, which was ascertained from the homology model. "Ab initio" calculations for various interactions were then performed to determine the mechanism ofthe 3C protease. The reactions resulting in a more negative stabilization energy are more likely to represent the reaction involving the trigger mechanism ofthe 3C protease. The trigger mechanism for 3C protease is similar to other cysteine proteases because the histidine must protonate the substrate for the reaction to proceed. Where the mechanism ofthe 3C protease differs from the mechanism of other cysteine proteases is that it does not contain an asparagine residue. The active site ofthe 3C protease consists of only two residues, cysteine and histidine. On the opposite side ofthe catalytic histidine, another conserved histidine at position 161 resides on the same side ofthe oxyanion binding site and functions either to protonate the carbonyl ofthe substrate or to direct the carbonyl to the histidine present in the catalytic site. The trigger mechanism for 3C protease thereby occurs as follows: NH S® Because the mechanism ofthe 3C protease was understood, "ab initio" calculations were made next for various combinations of reactants to determine the stabilization energies of each potential tetrahedral complex and therefore the trigger ofthe protease. All of the examples thus far have considered simplistic "ab initio" calculations between one residue and a host of potential chemical moeities. Once a chemical group has been identified as being a potential activator or inhibitor, the effect of that chemical group can be considered with regard to other residues in the enzyme's active site. For mechanism based drug design, it is very important to be able to compute, and thus understand how to modify, the reactivity of a small molecule that interacts with the enzyme active site. In order to compute reactivity in the active site of an enzyme, one must determine how much ofthe active site must be included to be predictive while keeping the calculation small enough to be performed routinely. Provided herein are a set of steps for doing this, along with illustrative data for the 3C protease active site, and a simple inhibitor, labeled cpiOOlό. As was stated above, the trigger for substrate reactivity ofthe 3C protease is the transfer of a proton or formation of multiple hydrogen bonds to stabilize a carbonyl oxygen. Therefore, the deprotonated sulfur of a cysteine residue must attack the carbonyl carbon in the substrate for the reaction to proceed. Now that the trigger has been identified, portions of 3C protease substrates that could have a significant effect on the electronic properties at the attack site must be identified. For this illustrative example, the compound labeled cpiOOlό is being used (common name 3',5'-dichloro-2'-hydroxy-acetophenone) as a 3C protease substrate. Next, a computable parameter that will vary according to the strength ofthe interaction between the enzyme and substrate portion must be identified. For this example, the bond length between the attacking cysteine sulfur atom ofthe 3C protease and the carbonyl carbon of cpiOOlό will be used. Other suitable parameters might be bond angles, torsion angles, pyramidalization angles, bond energies, or atomic charges. The third step is to identify the portion of the active site that could be reasonably expected to affect the reactivity ofthe attack interaction. For this example, the crucial interaction is the stabilization ofthe carbonyl oxygen on cpiOOlό. This is done both by hydrogens on the 3C protease backbone and by the hydroxy group ion cpiOOlό (an internal trigger). Becaise only the backbone is part of this interaction, the residue side chains were removed from the calculation, with the exception ofthe attacking cysteine. An "ab initio" calculation is then run on this portion ofthe system. For this example, geometry optimization calculations at the PM3 level of theory were used. Examine the C-S bond length of 2.000 A. The complex being modeled is provided below: Next, the same calculation is performed using successively smaller portions ofthe 3C protease. For this example, the following results were obtained. Once these calculations have been completed, they can be examined to determine how much ofthe enzyme must be included in the calculation at this stage. In this example, the second system, with a bond length of 2.001 A is sufficient to obtain most ofthe electronic effect ofthe 3C protease. This same portion of enzyme could then be used in electronic structure calculations to test the electronic effect of various substrate groups. In general, a model system that recovers 90% ofthe electronic effect will reliably predict the electronic effects from the enzyme site. Note that it will be necessary to test several computational levels of theory for performing the geometry optimizations and energy calculations, then choose the level of theory that gives an acceptable level of accuracy. The least time consuming calculations that give acceptable accuracy should be used. Some recommended levels of theory to test are PM3, HF/6-31+G*//PM3, B3LYP/6- 31+G*/ PM3, ONIOM(B3LYP/6-31+G*:UFF). Example 5: Identifying Compounds Usin QCT ' and Employing Such Compounds to Screen for New Target Sites Because the trigger for the 3C protease is a proton transfer to the substrate from the enzyme and the oxyanion binding site in 3 C is not as tight as it is in serine or other cysteine proteases, a molecule with an internal hydrogen bond transfer capability is required per example of such a molecule is provided in the general scheme below: Specifically: The "ab initio" calculations performed using the HF/6-3 l+G*//HF/6- 31+G* basis presents the affinity for the internal proton transfer during a nucleophilic attack by a sulfur as a function ofthe addition of electron- withdrawing substituent X 3 and X 5 and as a function of R. The results are provided in Table V. In Table VI, also below, the original molecule and the addition product energies are calculated and presented. The energy difference between the reactants (original molecule+ nucleophile) and the product is calculated. The larger the energy difference between the products and the reactants, the more stable the compound. The more stable the compound, the more likely it to serve as a candidate as a QCT lead molecule. For example, S3 has a stabilization energy of -16 kcal/mol. It is the best candidate because the value is most negative. The whole series of compounds were tested experimentally, and Table V: Ab initio calculations for various combinations of reactants of a 3C protease Table VI: Calculations of Molecules to Screen for New Target Sites. there is a full correlation between the calculations and the experiment Thus, as X 3 and X 5 more strongly withdraw electrons, the potency ofthe inhibitors increases Example 6 Prophetic Examples of Pharmaceuticals Derived from Quantum Core Technology Telomerase is a nucleoprotein expressed in immortalized cells, including most cancerous cells Telomerase adds hexameric nucleotide repeats to telomeres, located at the ends of chromosomes to counteract the cellular aging process by which telomeres shorten at every cellular division Because the majority of common human tumors possess telomerase activity, telomerase has become a universal cancer target The two components of telomerase, the RNA component and the polymerase component, interact to form the active site Sequences of both components are known although the structures are not From the sequence identity, the telomerase polymerase is reported to be homologous to FflN reverse transcriptase, whose structure is known Telomerase inhibition can be accomplished through a variety of molecules reported in the scientific literature The most important class of inhibitory molecules for the application in Quantum Core Technology™ are nucleotide analogs "Ab initio" calculations can be made between the two components ofthe enzymes and the potential inhibitors and rank ordered according to the greatest negative Gibbs free energy, thereby determining the most likely inhibitory molecule to compete with the endogenous substrate The structure of HIV reverse transcriptase can be used to model the hypothesized active site residues to interact with potential inhibitors After determining the trigger mechanism ofthe target protein, a pharmaceutical agent comprising the isolate trigger can be synthesized In another prophetic example, molecules derived from QCT™ can be used to treat metastases which possess active cathepsins Cathepsins are diverse intracellular proteases that can cleave substrates with a variety of active catalytic residues including cysteine, serine, or aspartic acid Cathepsins are active at acidic pH and chiefly located in lysosomes There is no known inhibitor of any cathepsin in mammals Cathepsins can be endopeptidases or exopeptidases and in normal cells contribute to cellular metabolism Secretion of cathepsins to the extracellular milieu, however, is associated with a variety of pathological states arthritis, cancer, and Alzheimer's disease In healthy cells, cathepsin D is regulated by estrogen and appears to play a role in the renewal of newborn epithelial tissues Cathepsin D is an aspartic protease whose upregulation is diagnostic and prognostic of cancer One mechanism by which cathepsin D can promote metastases in the extracellular milieu is by liberating Fibroblast Growth Factor 2 (FGH 2 ), which consequently acts as a mitogen on cancer cells. From experiments performed in rats, it appears that cathepsin D can promote metastases at sites distal from the initial invasion by promoting growth and colonization. Cathepsin D can activate cathepsin B, which can further activate metastatic promoting protease cascades (see below). Another way in which cathepsin B can influence metastases is through competing with IGFII for receptor binding. Cathepsin B is a cysteine protease whose upregulation and increased activity is associated with cancer diagnosis and prognosis. Its ability to degrade fibronectin, laminin, and collagen IV at physiological pH suggests that cathepsin B could act in cancer to promote metastases. Yet another demonstrated role for cathepsin B is activating a protease cascade that promotes metastasis. Procathepsin B can be activated by cathepsin D, which in turn can activate pro- urokinase-type plasminogen activator. Urokinase-type plasminogen activator converts plasminogen into plasmin, which is then capable of degrading the tumor stroma. Plasmin can also activate all three major matrix metalloproteases, each able to contribute to the degradation ofthe tumor stroma. Involvement in tumor angiogenesis might be another way in which cathepsin B promotes cancer. Both cathepsins B and D appear to be upregulated in cancer and promote metastases through at least one common mode: their protease activities. The protease activities of both cathepsins B and D are excellent targets for inhibitor development using the quantum core technology. "Ab initio" calculations can be made between the cathepsins and the potential substrates and rank ordered according to the greatest negative Gibbs free energy, thereby determining the most likely inhibitory molecule. After determining the trigger mechanism ofthe target protein, a pharmaceutical agent comprising the isolate trigger can be synthesized. In yet another prophetic example in which molecules derived from QCT™ can be utilized is in reducing antibiotic resistance by inhibiting certain amidase activity in mycobacteria and other actinomycetes. Mycothiol is an antioxidizing molecule produced in actinomycetes, including mycobacteria, but not in humans. The presence of this protein in pathogenic organisms and absence in humans suggests that it could be a specific drug target, if its inhibition led to infection clearance with minimal side effects. In fact, when Mycobacterium smegmatis mutants are generated for decreased mycothiol biosynthesis, existing compounds like peroxide, superoxide, and the antibiotic rifampin are able to more effectively kill the organisms. These observations indicate that inhibiting mycothiol biosynthesis could render existing therapeutics more effective against mycobacteria infections. A pathway for detoxifying antibiotics has been identified in mycobacteria in which mycothiol forms a thiol conjugate with an electrophilic moeity of an antibiotic. Mycothiol S-conjugate amidase (termed amidase-I) then cleaves the compound into a mercapturic acid which is secreted from the cell and glucosamine-alpha (l->l)-myo-inositol which is resynthesized into mycothiol. Amidase I has been identifed in the genomes of M. smegmatis and M. tuberculosis and a second protein with 36% identity to amidase I has been identified in tuberculosis, which represents a possible second protein involved in the detoxifying process. A streptomycete null mutant for amidase-I is more sensitive to killing by isoniazid, erythromycin, tetracycline, and vancomycin. Amidase- 1 inhibitors would severely impair mycothiol biosynthesis by reducing the necessary precursor. Without a functioning amidase- 1 , mycothiol will form a thiol conjugate with an antibiotic, but not undergo subsequent release. In this way the amount of mycothiol in each organism will decrease, making the organism vulnerable to antibiotics. Antibiotic resistance is on the rise throughout the world, and it is reasoned that a compound able to increase the lifetime utility of current therapies will enhance the repetoire of pharmacopoeia available to the clinician. Amidase- 1 is an excellent target for inhibitor development using QCT™. Amidase- 1 can be cloned and expressed in great enough quantity to facilitate solving a crystal structure. After this step, "ab initio" calculations can be made between the amidase- 1 and its potential substrates and rank ordered according to the greatest negative Gibbs free energy, thereby determining the most likely inhibitory molecule. After determining the trigger mechanism ofthe target protein, a pharmaceutical agent comprising the isolated trigger can be synthesized.

Claims: WE CLAIM: 1. A molecule comprising a minimal quantity of atoms to trigger a desired reaction wherein said molecule is designed by the following steps: (a) determining the minimal quantity of atoms to trigger a desired reaction to occur, said minimal quantity of atoms collectively comprise the trigger mechanism for the desired reaction; and (b) positioning said minimal quantity of atoms on a ligand wherein said molecule can trigger said desired reaction independently from the naturally occuring desired reaction. 2. A molecule comprising a minimal number of atoms for inhibiting a mechanism of action of a given reaction wherein said molecule is designed by the following steps: (a) determining the trigger mechanism ofthe given reaction; and (b) positioning said minimal number of atoms on a ligand wherein said ligand comprises an atom that functions as a poor leaving group when said molecule interacts with a reactant ofthe given reaction, thereby causing said molecule to inhibit the mechanism of action of the given reaction. 3. A molecule of claim 1 wherein said molecule comprises the minimum quantity of atoms to trigger the reaction of aspartic protease and has the following basic structure. wherein B can be any basic group; R 1 and R 2 can be any functional group; and x can be any atom or group that is more electronegative than sp 2 carbon. 4. A molecule of claim 1 wherein said molecule comprises the minimum quantity of atoms to trigger the reaction of metallo protease and has the following basic structure: wherein B can be any basic group; Ri and R 2 can be any functional group; and x can be any atom or group that is more electronegative than sp carbon. 5. A molecule of claim 1 wherein said molecule comprises the minimum quantity of atoms to trigger the reaction of cysteine protease and has the following basic structure wherein x can be any atom or group that is more electronegative than sp carbon; and R 2 are any functional group; and y is any proton donating group. 6. A molecule of claim 1 wherein said molecule comprises the minimum quantity of atoms to trigger the reaction of serine protease and has the following basic structure: X II / κ 1 B wherein B can be any basic group; Ri and R 2 can be any functional group; and x can be any atom or group that is more electronegative than carbon. 7. A system for developing a small molecule wherein said system comprises: (a) a method to compare the stabilization energies of a given reaction between a catalytic residue of an enzyme to residues of a substrate to determine the trigger mechanism for the given reaction; (b) a minimal amount of atoms comprising said trigger mechanism of the given reaction; and (c) a ligand wherein said minimal amount of atoms are positioned on said ligand to form said molecule. 8. A molecule that can inhibit a given reaction wherein said molecule is designed from the system in claim 7. 9. A molecule that can enhance the probability of a given reaction occuring wherein said molecule is designed from the system in claim 7. 10. A molecule wherein said molecule comprises a minimum quantity of atoms to inhibit the given reaction wherein said molecule is designed from the system in claim 7. 11. A molecule in claim 10 wherein said minimum quantity of atoms includes a poor leaving group to inhibit the given reaction. 12. A method for determining the trigger mechanism of a given reaction wherein said method uses a matrix involving the steps of: (a) performing ab initio calculations on a class of enzymes to compare a reactive residue associated with a catalytic site common to the class of enzymes to a reactive residue with one or more substrates associated with the class of enzymes; (b) using the information generated from step (a) and performing further ab initio calculations on a subclass of enzymes by comparing further reactive residues associated with the catalytic site common to the subclass of enzymes with one or more substates associated with the subclass of enzymes; (c) using the information generated from step (b) and performing further ab initio calculations on a single enzyme from the subclass of enzymes by comparing all reaction residues associated with the catalytic site ofthe enzyme with one or more substrates associated with the enzyme; and (d) using the information generated from step (c) to determine the trigger mechanism for the enzyme. 13. A method for determining a trigger mechanism for a given reaction comprising the steps of: (a) performing ab initio calculations to determine the stability of each potential interaction between each active site residue of an enzyme and a chemical moiety of one or more substrates of said enzyme; (b) analyzing the calculated stabilization energies, wherein the most negative energies are the most reactive species and the most positive energies are the least reactive species; and (c) combining the chemical moieties that were calculated to be the most reactive, or the least reactive, with each corresponding catalytic residue on a compound scaffold. 14. A method for deteriming the trigger mechanism of a given reaction comprising the steps of: (a) aligning a protein sequence of an enzyme with other proteins and determining by homology the general class ofthe enzyme; (b) performing biochemical assays to determine the reaction performed by the enzyme; (c) performing site-directed mutagenesis of conserved amino acids and determining if the mutated residues act in the reaction mechanism; (d) determining the mechanism of catalytic action for the enzyme; and (e) performing ab initio calculations to determine the stability of each potential interaction between each active site residue ofthe enzyme and a chemical moiety of one or more substrates of said enzyme. 15. A method of designing a small molecule that interacts with the active site of a certain enzyme comprising the steps of: (a) aligning the protein sequence ofthe enzyme with other proteins and determining by homology the general class of enzyme; (b) performing biochemical assays to determine the reaction performed by the enzyme; (c) performing site-directed mutagenesis of conserved amino acids and determining if the mutated residues act in the reaction mechanism; (d) determining the mechanism of catalytic action for the enzyme; (e) performing ab initio calculations to determine the stability of each potential interaction between each active site residue ofthe enzyme and a chemical moiety of one or more substrates of said enzyme; (f) analyzing the calculated stabilization energies, wherein the most negative energies are the most reactive species and the most positive energies are the least reactive species; and (g) combining the chemical moieties that were calculated to be the most reactive, or the least reactive, with each corresponding catalytic residue on a compound scaffold. 16. A molecule that can inhibit a given reaction wherein said molecule is designed from the methodology in claim 15. 17. A molecule that can enhance the probability of a given reaction occuring wherein said molecule is designed from the methodology in claim 15. 18. A molecule comprising a minimum quantity of atoms that function as a trigger mechanism for a given reaction wherein said molecule is designed from the methodology in claim 15. 19. A molecule comprising a minimal quantity of atoms to inhibit the activation of telomerase wherein said molecule comprises a poor leaving group. 20. A molecule comprising a minimal quantity of atoms to inhibit the activation of mycothiol s-conjugate amidase wherein said molecule comprises a poor leaving group.

Inventors: ARAD DORIT, BOLLON ARTHUR P, PEEK ANDREW S, POLAND BRADLEY W, YOUNG DAVID C, ARAD, DORIT, BOLLON, ARTHUR, P., PEEK, ANDREW, S., POLAND, BRADLEY, W., YOUNG, DAVID, C.
Applicants: ARAD DORIT, BOLLON ARTHUR P, CYTOCLONAL PHARMACEUTICS INC, PEEK ANDREW S, POLAND BRADLEY W, YOUNG DAVID C, ARAD, DORIT, BOLLON, ARTHUR, P., CYTOCLONAL PHARMACEUTICS, INC., PEEK, ANDREW, S., POLAND, BRADLEY, W., YOUNG, DAVID, C.
Application year: 2000
Main classification: B01J19
IPC codes: A61K45, A61P35, A61P43, C07B61, C07C49, C07C233, C07C323, C12Q1