Patent Publication Number: US-2011054019-A1

Title: Cancer Starvation Therapy

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
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     RELATED APPLICATIONS 
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     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention describes a method for the ablation of targeted tissue or cells via the administration of glutamine analogues containing platinum, iron, and/or other high Z elements and subsequently exposing such tissue or cells to high energy radiation, including, but not limited to, x-rays, gamma rays, microwaves, alpha particles, protons, and neutrons. More specifically, the present invention describes a method for targeting the mitochondria of the aforementioned tissue or cells for destruction, thereby starving such cells of the energy they require to proliferate. 
     2. Discussion of the Background 
     Radiation therapy is usually defined as the use of high-energy radiation from x-rays, gamma rays, neutrons, protons, and other sources to kill cancer cells and shrink tumors. Radiation may come from a machine outside the body also called external-beam radiation therapy, or it may come from radioactive material placed in the body near cancer cells also called internal radiation therapy. 
     Radiation therapy, however, has its limitations. The ionizing radiation used to ablate unwanted tissue can cause damage to surrounding healthy tissue, or may not be effective against the target tissue due to conditions such as hypoxia which makes the targeted cells radioresistent or cells being in a part of the mitotic cycle where they are not as sensitive to the effects of such radiation. Much study and effort has been expended developing compounds and techniques to enhance the effectiveness of radiation therapy and limit the damage to healthy, non-targeted tissue. 
     Radiosensitizers are drugs created to enhance the effectiveness of radiation therapy by making tumorigenic cells more susceptible to the effects of radiation. One class of radiosensitezers, known as halogenated pyrimidines, accomplishes this enhancing effect by directly making DNA more susceptible to damage from radiation. This class of radiosensitizers works by incorporating halogenated pyrimidines directly into the DNA chain in substitution of thymidine. This substitution weakens the DNA chain and makes cells more susceptible to radiation and ultraviolet light. Another class of radiosensitizers functions by fast ionization/deexcitation processes and the strong emission of secondary electrons. Yet another class of radiosensitizers, known as hypoxic-cell sensitizers, increase the radiation sensitivity of tumorigenic cells deficient in molecular oxygen. 
     The radiosensitizing effects of these drugs are believed to aid the ionizing radiation by augmenting the latter&#39;s ability to damage nuclear DNA in creating strand breaks that are not repairable, therefore triggering apoptosis. It has also been theorized that the drug cisplatin, a chemotherapeutic drug that is known to have radiosensitizing properties, may cause damage to mitochondrial structures. 
     Further, cellular respiration is the set of metabolic processes by which biochemical energy from nutrients is converted to energy in the form of andostein triphosphate (“ATP”). During normal aerobic cellular respiration, one molecule of glucose, the most abundant nutrient in mammalian serum, is converted to two molecules of pyruvate and two net molecules of ATP. This process is known as glycolysis. The pyruvate is then further broken down in order to release a theoretical yield of 36-38 molecules of ATP. 
     The mitochondria, which plays an important part in the aerobic cellular respiration process, are spherical or elongated organelle in the cytoplasm of nearly all eukaryotic cells, containing genetic material and many enzymes important for cell metabolism, including those responsible for the conversion of food to usable energy. Mitochondria provide the energy a cell needs to move, divide, produce secretory products, contract—in short, they are the power centers of the cell. They are about the size of bacteria but may have different shapes depending on the cell type. 
     Mitochondria are membrane-bound organelles, and like the nucleus have a double membrane. The outer membrane is fairly smooth; the inner membrane is highly convoluted, forming folds called cristae. The cristae greatly increase the inner membrane&#39;s surface area, and it is here that mitochondrial electron transport occurs. 
     The elaborate structure of a mitochondrion is very important to the functioning of the organelle. Two specialized membranes encircle each mitochondrion present in a cell, dividing the organelle into a narrow intermembrane space and a much larger internal matrix, each of which contains highly specialized proteins. The outer membrane of a mitochondrion contains many channels formed by the protein porin and acts like a sieve, filtering out molecules that are too big. Similarly, the inner membrane, which is highly convoluted so that a large number of infoldings called cristae are formed, also allows only certain molecules to pass through it and is much more selective than the outer membrane. To make certain that only those materials essential to the matrix are allowed into it, the inner membrane utilizes a group of transport proteins that will only transport the correct molecules. Together, the various compartments of a mitochondrion are able to work in harmony to generate ATP in a complex multi-step process. 
     The mitochondrion is different from most other organelles because it has its own circular DNA (similar to the DNA of prokaryotes) and reproduces independently of the cell in which it is found; an apparent case of endosymbiosis. Mitochondrial DNA is localized to the matrix, which also contains a host of enzymes, as well as ribosomes for protein synthesis. Many of the critical metabolic steps of cellular respiration are catalyzed by enzymes that are able to diffuse through the mitochondrial matrix. The other proteins involved in respiration, including the enzyme that generates ATP, are embedded within the mitochondrial inner membrane. Infolding of the cristae dramatically increases the surface area available for hosting the enzymes responsible for cellular respiration. 
     Human mitochondria contain 5 to 10 identical, circular molecules of DNA. Each molecule contains 16,569 base pairs that encode 37 genes including ribosomal RNA (rRNA), transfer RNA (tRNA), and 13 polypeptides. The 13 proteins are an important part of the protein complexes in the inner mitochondrial membrane, forming part of complexes I, III, IV, and V. These protein complexes also dependent upon proteins encoded by nuclear DNA which are synthesized in the cytosol and imported into the mitochondria. 
     In the absence oxygen, a hypoxic cell can still generate energy through glycolysis and generate two net molecules of ATP. However, under such hypoxic conditions, the resulting pyruvate is not transported into the mitochondria for further processing, but rather remains in the cytoplasm where it is converted to lactate by lactic acid fermentation and expelled from the cell. This process is known as anaerobic respiration. 
     Interestingly, it has been observed for some time that even in the presence of oxygen, rapidly proliferating tumorgenic cells have a preference for inefficient anaerobic respiration and therefore utilize an abnormally high amount of glucose. This is known as aerobic glycolysis, or the Warburg Effect, named after Otto Heinrich Warburg, who made the discovery in 1926. Various theories have been put forth to account for this effect, among which is that glucose degradation provides cells with intermediaries used in a variety of biosynthetic pathways. It is therefore theorized that tumor cells maintain robust glycolysis in order to keep a ready supply of such intermediaries. 
     Glucose is not however, the only compound to be consumed at highly elevated levels by proliferating cancerous cells. These cells also use copious amounts of glutamine relative to non-tumorigenic cells. Glutamine is a non-essential amino acid present abundantly throughout the body and is involved in many metabolic processes. It is synthesized from glutamic acid and ammonia. It is the principal carrier of nitrogen in the body and is an important energy source for many cells. 
     In cancerous cells, the TCA cycle is truncated because such cells use carbon from the cycle for biosynthetic purposes. Citrate therefore is unlikely to cycle all the way back around and regenerate oxaloacetic acid (“OAA”). Tumors solve the problem of the need to regenerate OAA—and also generate much of the energy they need to proliferate—by oxidizing large amounts of the amino acid glutamine and incorporating it into the truncated TCA cycle. In tumorigenic cells, the truncated TCA cycle incorporates glutamine and pyruvate supplied by the phosphorylation of glucose to generate energy and create precursors for biosynthetic pathways. 
     The phenomenon of significantly increased glutamine utilization in tumorigenic cells has been previously studied as a potential pathway by which therapeutic anti-cancer drugs may act. The glutamine analogues L-[alpha S,5S]-alpha-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid (acivicin) and 6-diazo-5-oxo-L-norleucine (DON) are known to possess cytotoxic activity against a wide variety of tumors. These drugs are thought to function by inhibiting mitochondrial enzymatic activity. However, their usefulness as therapies for humans has been limited due to their high toxicity. 
     To date, there has been no drug specifically designed as a radiosensitizer that targets the mitochondria of tumorigenic tissue and cells for destruction. 
     Physical Aspects of High-Z Materials and Charged Particle Amplification 
     The following discusses the effects of high-Z materials on the atomic (picometer, or 1E-12 meter) scale, by comparing the individual interaction rates of different materials when exposed to a fluence of charged particles and gamma- or x-ray photons. Furthermore, in the context of therapeutic radiation, the energy deposition models provided herein for the orthovoltage and megavoltage energy ranges are 2E5 to 1.8E7 eV, or 3.2E-14 to 2.88E-12 J. 
     For therapeutic irradiation, tissue is exposed to a calibrated beam of electrons or photons. Photons indirectly interact with matter through coherent, photoelectric, Compton, or pair production collisions. Coherent scattering results in no energy deposition, and will not be discussed further. The remaining collisions result in the emission or ejection of electrons. The scattered electrons further deposit energy by directly interacting with nearby atoms in collisional or radiative type events, potentially ejecting additional electrons (5 rays). The total amount of kinetic energy per unit mass lost from the photons and δ rays in non-radiative processes is referred to as collision kerma, or K c . The units are typically given in J/kg, or Gy. In the presence of charged particle equilibrium, the total amount of absorbed dose is equal to the collision kerma. In surrounding matter, the dose deposition process results in the generation of free electrons and ions which can damage the DNA or other cellular structures; in the case of the present invention, the mitochondria. Collision kerma can be calculated directly from the collision probabilities (or cross sections) of each interaction using the formula as in  FIG. 1 , where ψ refers to the incident photon energy fluence in J/cm 2 , P is the material density in g/cm 3 , g is the average fraction of secondary electron energy lost to radiative processes. The values T tr , σ tr , and K tr , refer to the energy transfer cross sections, in cm −1 , for photoelectric, Compton, and pair production interactions, respectively. 
     For incident photon energies of 0.5 to 5 MeV on almost all materials, the Compton cross section dominates the above equation; that is, σ tr &gt;T tr , K tr . The cross section for Compton interactions has been rigorously modeled by Klein and Nishina (Evans, 1955), as shown in  FIG. 2 , who defined the following statement for σ tr , where r 0  refers to the classical electron radius e 2 /m 0 c 2 =2.818×10 −13  cm, N A =6.022×10 23  mole −1  is Avagadro&#39;s constant, Z is the number of electrons per atom, A w , is the atomic weight in grams, h=6.626×10 −34  is Planck&#39;s constant in J-s, v is the frequency of incident radiation in cm −1 , m 0 =0.91095×10 −3 ° kg is the rest mass of an electron, and c=2.9979×10 10  cm/sec is the speed of light. 
     For incident electrons with energy T (in J), the expectation value for rate of energy loss due to collisional events through a linear distance x (in cm) can be described by the collision stopping power of a material, or (dT/dx) c .  FIG. 3  defines the collision stopping power for electrons adjusted for the polarization effect and shell correction, where 1 is the mean ionization/excitation potential (Berger &amp; Seltzer, 1983) of the material in J, δ is the polarization correction parameter (Stermheimer, 1952), and c is the shell correction parameter (Bichsel, 1968). 
     Similarly, the expectation value for energy loss due to radiative events, i.e. bremsstrahlung, is described by the radiative stopping power (dT/dX) r , and is shown in  FIG. 4 . The value  B   r  is defined by Bethe and Heitler (Evans, 1955), and carries a slight dependence on Z and T. 
     The radiation yield, therefore, is simply the mean ratio of energy loss to radiative processes relative to the total rate of energy loss over all initial electron energies and as each electron loses energy.  FIG. 5  shows the radiation yield formula, where T max  refers to the maximum initial electron energy. 
     In order to achieve an increased dosimetric effect from external ionizing radiation, targeted molecules located around a biological target can be replaced with appropriate analogues that contain one or more high-Z elements. An important quantifier for this effect can be defined as the relative increase in the expectation value of charged particle fluence created by the high-Z analogue over that of the original molecule. This value, herein referred to as the amount of charged particle amplification A, as shown in  FIG. 6 . 
     As defined above, the value of A is dependent on the type of molecule used for high-Z implementation. Furthermore, the effects of molecular binding on each high-Z atom will modify slightly the above equations that define the interaction rates. That said, numerical values for A can be estimated and quantified for each individual high-Z elemental substitution performed in a molecule using the above formulas. For photon interactions, the increase in charged particle fluence is simply the ratio of energy transfer interaction probabilities (the subscript a is used to denote these probabilities in units of cm 2 /atom). Similarly, the reduction in fluence may be estimated for electron interactions by comparing the ratio of energy lost to radiative processes.  FIG. 7  presents a formula wherein these results compete to formulate A, where the superscript z refers to the interaction cross sections for the high-Z material, while c refers to the element substituted (considered a carbon atom). 
     Values for A have been plotted in  FIG. 8  for atomic numbers Z=1 through 90, where carbon (Z=6) is used as the reference, using published energy absorption cross sections (Seltzer, 1993). Data for three incident photon energies has been given: a monoenergetic 500 keV theoretical beam, and polyenergetic 6 MV and 18 MV beams typically found on a modern therapeutic linear accelerator. As an example, three gold atoms (Z=79) would yield a factor of 17×3=51:1 higher fluence rate than three carbon atoms present in the same molecule for a 6 MV photon beam. The same replacement would yield a factor of 136:1 and 82:1 for 500 keV photons and an 18 MV beam, respectively. In order to apply this value to the entire molecule, A can be expanded to include the atomic fractions f 1 , f 2  of each element with atomic number Z 1 , Z 2 , etc. present in the compound. In addition, Bragg&#39;s rule can be applied to estimate the mean ionization potential and polarization correction, as shown in  FIG. 9 . 
     SUMMARY OF THE INVENTION 
     The present invention helps to overcome the limitations of radiation therapy as disclosed above, by providing a radiosensitizing glutamine analogue containing platinum, iron, and/or other high Z elements, which when exposed to x-rays or other ionizing or high energy radiation such as gamma rays, alpha particles, protons, neutrons, or fast ions, causes the destruction of mitochondrial and other structures of targeted tissue and cells. 
     Another object of the present invention is the destruction of the mitochondria, wherein said destruction effectively denies energy and substrates necessary for proliferation for cancerous cells. 
     Another object of the present invention is to destroy mitochondrial structures of target cells, thereby rendering the mitochondria nonfunctional and starving the cell of the energy and substrates necessary for its survival. 
     Another object of the present invention is to interact with the mitochondria instead of the DNA. Radiation therapy traditionally targets nuclear DNA for destruction. However, in proliferating cells, unless such cell is undergoing mitotic division the double helix strand of nDNA has not condensed into a chromosome and is therefore not susceptible to the same irreparable damage as if the cell were in mitosis. The current invention does not primarily seek to destroy nuclear DNA, although nDNA damage of target tissue may result and would be desirable. 
     Yet another object of the present invention is to provide a radiosensitizing compound where one or more atoms, functional groups, or substructures of glutamine have been replaced with at least one or more high Z elements. 
     The present invention consists of platinum, iron, and/or other high Z elements located at the center of the glutamine analogue, thereby replacing one or multiple carbons. Further the present invention consists of high Z elements being attached via a side chain or ligand to the glutamine analogue. 
     Irrespective of the embodiment, the invention may be administered by any standard method, including, but not limited to, intravenously, intra-arterially, orally, or direct injection into targeted tissue in vivo or in vitro. 
     High Z elements suitable for inclusion in the invention are those with a Z value of at least 22, and include, but are not limited to, platinum (Z=78), vanadium (Z=23), iron (Z=26), cobalt (Z=27), copper (Z=29), molybdenum (Z=42), palladium (Z=46), silver (Z=47), tin (Z=50), tantalum (Z=73), gadolinium (Z=64), dysprosium (Z=66), holmium (Z=67), hafnium (Z=72), tungsten (Z=74), rhenium (Z=75), osmium (Z=76), iridium (Z=77), gold (Z=79), thallium (Z=81), lead (Z=82), bismuth (Z=83), and uranium (Z=92). 
     Further, the purpose of the accompanying abstract is to enable the U.S. Patent and Trademark Office and the public generally, and especially the scientists, engineers, and practitioners in the art who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The abstract is neither intended to define the invention of the application, which is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings which are incorporated herein constitute part of the specifications and illustrate the preferred embodiment of the invention. 
         FIG. 1  shows a collision probability equation. 
         FIG. 2  shows a Compton interaction model. 
         FIG. 3  shows the collision stopping power equation for electrons. 
         FIG. 4  shows a radiative stopping power equation. 
         FIG. 5  shows a radiation yield equation. 
         FIG. 6  shows the amount of charged particle amplification formula. 
         FIG. 7  shows relative amount of charged particle amplification formula when binding high Z-atoms. 
         FIG. 8  shows plotted values of  FIG. 7  equation for different values of Z. 
         FIG. 9  shows an equation to estimate the mean of ionization potential and polarization correction. 
         FIG. 10  shows the structure of glutamine, chemical formula C 5 H 10 N 2 O 3 . 
         FIG. 10  shows the structure of glutamine. 
         FIG. 11   a - 11   b  shows a structural analogue of present invention with single replacement. 
         FIG. 12   a - 12   b  shows a structural analogue of present invention with 2 carbon replacement. 
         FIG. 13   a - 13   b  shows a structural analogue of present invention with 3 carbon replacement. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention is directed to a glutamine analogue composition, wherein said composition is design to be exposed and enter the mitochondrion, more particularly the mitochondria of not-healthy cells, such as but not limited to cancer cells. Subsequently the not-healthy cells become a target, wherein said targeted cells are exposed to ionizing radiation. When exposed to ionizing radiation, the present composition, having metallic particles, reacts in such way that damages mitochondrial (as well as other) substructures such as mtDNA, the outer membrane, the inner membrane, cristae, ribosomes, etc., and causes the effective destruction of such mitochondrion. The destruction of the mitochondria starts the programmed cell death of Tumorigenic cells for the reason that without mitochondria Tumorigenic cells cannot produce the energy they need to subsist and replicate, effectively starving mitochondria damaged cells of energy and causing their destruction. 
       FIG. 10  shows glutamine, wherein said glutamine is composed of a chain of three carbon atoms, Z=6, attached on either end to an additional atom of carbon. The present composition as mentioned consists in the replacement the core carbon atoms with high Z elements, such as gold atoms, Z=79.  FIGS. 11-13  discloses several embodiments for the present invention. The present composition is generated, for example by replacing the carbon atoms. Further the present composition acts as a glutamine analogue compound that accesses the mitochondria. However due to the replacement of glutamine atoms for other high Z elements, such as but not limited to gold or copper, the properties of the element change providing a composition susceptible to radiation, as mentioned before. 
       FIG. 11(   a ), as an example, shows a first generic embodiment of the present invention compound wherein the structural analogue of glutamine, more particularly the amine functional group NH 2  is replaced with a high z element, and in this generic case, three Hydrogen atoms. The Nitrogen atom may also be replaced with any high z element that would require 2 (or any number) hydrogen atoms to bind with it, in which case such generic substitution would take the form ZH 2 , where Z is any high z element as previously defined. Such general first embodiment is denoted with the generic chemical formula C 5 H 11 ZNO 3 . 
       FIG. 11   b  provides a more specific embodiment of the first general embodiment presented in  FIG. 11   a  above. As disclosed above the first embodiment consists of a structural analogue of glutamine where the amine functional group NH 2  is replaced with a high z element and three Hydrogen atoms such as AuH 3 . The chemical formula for this specific compound is C 5 H 11 AuNO 3 . 
       FIG. 12   a , as an example, shows an second embodiment of the present invention, wherein a structural analogue of glutamine, more particularly two carbon atoms are replaced with high z elements. Z is any high z element as previously defined, wherein said general second embodiment is denoted with the generic chemical formula C 3 H 10 Z 2 N 2 O 3 . 
       FIG. 12   b  provides a more specific second embodiment of the general embodiment presented in  FIG. 12   a  above. The present second embodiment consists of a structural analogue of glutamine where two carbon atoms are replaced with Cu atoms. The chemical formula for this specific compound is C 3 H 10 Cu 2 N 2 O 3 . 
       FIG. 13   a , as en example, shows a third embodiment of the present invention, wherein structural analogues of glutamine, more particularly three carbon atoms are replaced with high z elements. Again Z is any high z element as previously defined, such general third embodiment is denoted with the generic chemical formula C 2 H 10 Z 3 N 2 O 3 . 
       FIG. 13   b  provides a more specific embodiment of the general embodiment presented in  FIG. 13   a  above. The present third embodiment consists of a structural analogue of glutamine where three carbon atoms are replaced with Au atoms. The chemical formula for this specific compound is C 2 H 10 Au 3 N 2 O 3 . 
     As mentioned, the present compounds are designed to access the mitochondria, wherein the estimated charged particle density from interactions in the area immediately surrounding present invention compound increases dramatically relative to the glutamine it substitutes. For example, as previously mentioned, for a 6 MV photon beam, three gold atoms (Z=79) in such an analogue would yield a factor of 17×3=51:1 higher fluence rate than three carbon atoms they replace. The same replacement would yield a factor of 136:1 and 82:1 for 500 keV photons and an 18 MV beam, respectively. 
     While the invention has been described as having a preferred design, it is understood that many changes, modifications, variations and other uses and applications of the subject invention will, however, become apparent to those skilled in the art without materially departing from the novel teachings and advantages of this invention after considering this specification together with the accompanying drawings. Accordingly, all such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by this invention as defined in the following claims and their legal equivalents. In the claims, means-plus-function clauses, if any, are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. 
     All of the patents, patent applications, and publications recited herein, and in the Declaration attached hereto, if any, are hereby incorporated by reference as if set forth in their entirety herein. All, or substantially all, the components disclosed in such patents may be used in the embodiments of the present invention, as well as equivalents thereof. The details in the patents, patent applications, and publications incorporated by reference herein may be considered to be incorporable at applicant&#39;s option, into the claims during prosecution as further limitations in the claims to patentable distinguish any amended claims from any applied prior art.