Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/33—Heterocyclic compounds
  • A61K31/395—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins
  • A61K31/435—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having six-membered rings with one nitrogen as the only ring hetero atom
  • A61K31/44—Non condensed pyridines; Hydrogenated derivatives thereof
  • A61K31/4427—Non condensed pyridines; Hydrogenated derivatives thereof containing further heterocyclic ring systems
  • A61K31/4439—Non condensed pyridines; Hydrogenated derivatives thereof containing further heterocyclic ring systems containing a five-membered ring with nitrogen as a ring hetero atom, e.g. omeprazole
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/33—Heterocyclic compounds
  • A61K31/395—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins
  • A61K31/495—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having six-membered rings with two or more nitrogen atoms as the only ring heteroatoms, e.g. piperazine or tetrazines
  • A61K31/505—Pyrimidines; Hydrogenated pyrimidines, e.g. trimethoprim
  • A61K31/513—Pyrimidines; Hydrogenated pyrimidines, e.g. trimethoprim having oxo groups directly attached to the heterocyclic ring, e.g. cytosine
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/33—Heterocyclic compounds
  • A61K31/395—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins
  • A61K31/495—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having six-membered rings with two or more nitrogen atoms as the only ring heteroatoms, e.g. piperazine or tetrazines
  • A61K31/505—Pyrimidines; Hydrogenated pyrimidines, e.g. trimethoprim
  • A61K31/519—Pyrimidines; Hydrogenated pyrimidines, e.g. trimethoprim ortho- or peri-condensed with heterocyclic rings
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/33—Heterocyclic compounds
  • A61K31/395—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins
  • A61K31/495—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having six-membered rings with two or more nitrogen atoms as the only ring heteroatoms, e.g. piperazine or tetrazines
  • A61K31/505—Pyrimidines; Hydrogenated pyrimidines, e.g. trimethoprim
  • A61K31/519—Pyrimidines; Hydrogenated pyrimidines, e.g. trimethoprim ortho- or peri-condensed with heterocyclic rings
  • A61K31/52—Purines, e.g. adenine
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/33—Heterocyclic compounds
  • A61K31/395—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins
  • A61K31/495—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having six-membered rings with two or more nitrogen atoms as the only ring heteroatoms, e.g. piperazine or tetrazines
  • A61K31/505—Pyrimidines; Hydrogenated pyrimidines, e.g. trimethoprim
  • A61K31/519—Pyrimidines; Hydrogenated pyrimidines, e.g. trimethoprim ortho- or peri-condensed with heterocyclic rings
  • A61K31/52—Purines, e.g. adenine
  • A61K31/522—Purines, e.g. adenine having oxo groups directly attached to the heterocyclic ring, e.g. hypoxanthine, guanine, acyclovir
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P1/00—Drugs for disorders of the alimentary tract or the digestive system
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P35/00—Antineoplastic agents

Definitions

• the invention pertains to the field of ameliorating the effect of drugs on the human body. More particularly, the invention pertains to a composition and a method for treatment of the side-effects associated with the administration of cancer chemotherapeutic agents, specifically 5-fluorouracil (5-FU).
• cancer chemotherapeutic agents specifically 5-fluorouracil (5-FU).
• chemotherapeutic drugs While effective at destroying a cancerous tumor, may also cause damage to normal tissues of the body.
• the normal tissues of the body most often affected by the side-effects of a cancer chemotherapeutic drug include the lining of the mouth, the lining of the intestine, and the hair. Symptoms associated with the deleterious effects of chemotherapeutic cancer drugs include hair loss, nausea, and vomiting.
• chemotherapeutic drugs can be debilitating and result in interruptions of the cancer chemotherapeutic drug treatment regimen.
• Various attempts have been made to lessen or to eliminate the symptoms associated with the administration of 5-fluorouracil (5-FU).
• One approach to mitigate the toxicity of 5-FU is to combine a 5-FU precursor drug with other agents such as oral oxonic acid and 5-chloro-2,4-dihydroxypyridine in the case of S-l .
• GI gastrointestinal
• Other drugs such as steroids, have been administered to patients to alleviate the suffering associated with the side- effects of cancer treatment using chemotherapy. The success associated with the use of these other drugs to alleviate suffering has not been successful, and as a consequence, the "treatment" is to lower the dose of 5-FU.
• drugs such as steroids and other drugs used to alleviate the side-effects of cancer drugs may be toxic to other tissues. Such tissue toxicity produces additional unwanted side-effects.
• a third problem associated with drugs administered to alleviate the side-effects of cancer therapy is that the drug used to alleviate the side-effects caused by the cancer drug may interfere with the activity of the cancer drug, resulting in diminished effectiveness for destroying the targeted cancerous tumor.
• a composition and method for the treatment of the side-effects associated with the administration of cancer chemotherapeutic agents involves the oral ingestion of a slow release capsule containing adenine and orotate.
• the administration of a protein pump inhibitor decreases systemic absorption of orotate, and the administration of allopurinol decreases the formation of 2,8-dihydroxy adenine from adenine.
• cationic liposomes contain purine/pyrimidine precursors. The cationic liposomes bind to the cells lining the mucosa of the intestinal tract and then the contents of the cationic liposome are then taken up in the interior of the cells to prevent the metabolism of the cancer treatment drug 5-FU into a toxic species.
• a composition addresses gastrointestinal toxicity caused by administration of at least one cancer chemotherapeutic agent to a cancer patient.
• the composition includes a protective formulation including at least one normal substrate of at least one enzyme that metabolizes the cancer chemotherapeutic agent to an active form.
• the normal substrate competes to inhibit metabolism of the cancer chemotherapeutic agent to a toxic species, and the normal substrate is non-toxic, such that normal homeostasis is maintained in the GI tract.
• Administration of the protective formulation does not result in a systemic level of the normal substrate sufficient to interfere with a systemic activity of the cancer chemotherapeutic agent.
• the protective formulation includes an aqueous solution including the normal substrate in an osmotically-controlled oral drug delivery device.
• the normal substrate includes adenine.
• the normal substrate further includes orotate.
• the composition includes a protein pump inhibitor.
• the protein pump inhibitor is omeprazole.
• the cancer therapeutic agent is 5-fluorouracil.
• the composition further includes allopurinol.
• a composition addresses the gastrointestinal toxicity caused by administration of 5-fluorouracil to cancer patients.
• the composition includes adenine, orotate, and a protein pump inhibitor.
• the adenine and orotate are in an osmotically-controlled oral drug delivery device.
• the protein pump inhibitor is omeprazole.
• the composition further includes allopurinol.
• a method addresses the gastrointestinal toxicity caused by administration of at least one cancer chemotherapeutic agent to a cancer patient.
• the method includes administering the cancer chemotherapeutic agent to the patient and orally administering to the patient a protective formulation including at least one normal substrate of at least one enzyme that metabolizes the cancer chemotherapeutic agent to an active form.
• the normal substrate competes to inhibit metabolism of the cancer chemotherapeutic agent to a toxic species, and the normal substrate is non-toxic, such that normal homeostasis is maintained in the GI tract.
• Administration of the protective formulation does not result in a systemic level of the normal substrate sufficient to interfere with a systemic activity of the cancer chemotherapeutic agent.
• the normal substrate includes adenine. In some embodiments, the normal substrate includes adenine.
• the normal substrate further includes orotate.
• the protective formulation further includes allopurinol.
• at least a portion of the protective formulation is administered in an osmotically-controlled oral drug delivery device.
• the cancer therapeutic agent is 5-fluorouracil.
• a composition addresses the gastrointestinal toxicity caused by administration of at least one cancer chemotherapeutic agent to a cancer patient.
• the composition includes cationic liposomes containing an aqueous solution of at least one normal substrate of at least one enzyme that metabolizes the cancer chemotherapeutic agent to an active form.
• the normal substrate competes to inhibit metabolism of the cancer chemotherapeutic agent to a toxic species, and the normal substrate is non-toxic, such that normal homeostasis is maintained in the GI tract.
• Administration of the protective formulation does not result in a systemic level of the normal substrate sufficient to interfere with a systemic activity of the cancer chemotherapeutic agent.
• the normal substrate includes adenine.
• the normal substrate further includes orotate.
• the aqueous solution further includes a protein pump inhibitor.
• the protein pump inhibitor is omeprazole.
• the cancer therapeutic agent is 5-fluorouracil.
• the aqueous solution further includes allopurinol.
• a method addresses the gastrointestinal toxicity caused by administration of 5-fluorouracil to a cancer patient. The method includes administering the 5-fluorouracil to the patient; and administering adenine and orotate at a dosage insufficient to give systemic levels of adenine and orotate to salvage cancer cells from a toxicity of the administered 5-fluorouracil.
• a method alleviates gastrointestinal distress, where either adenine or orotate is limiting in availability, in a patient.
• the method includes orally administering at least one of adenine and orotate to the patient.
• the method also includes administering allopurinol to the patient.
• the method also includes administering a protein pump inhibitor to the patient.
• the adenine or orotate is administered in an osmotically-controlled oral drug delivery device.
• the adenine or orotate is administered in cationic liposomes.
• Fig. 1 shows the effect of different levels of adenine in combination with 2.5 mM orotate on the growth of human-derived colon (Caco-2) cells exposed to 5-FU in cell culture.
• Fig. 2 shows the effect of different levels of adenine in combination with 1.25 mM orotate on the growth of human-derived colon (Caco-2) cells exposed to 5-FU in cell culture.
• Fig. 3 shows the effect of adenine or inosine in combination with orotate on the growth of human-derived colon (Caco-2) cells exposed to 5-FU in cell culture.
• Fig. 4 shows the effect of different levels of uracil in combination with adenine
• Fig. 5 shows the effect of adenine, orotate, and uracil on the growth of primary human skin cells exposed to 5-FU in cell culture after 48 hours.
• Fig. 6 shows the effect of adenine, orotate, and uracil on the growth of primary human skin cells exposed to 5-FU in cell culture after 72 hours.
• the approach described herein to alleviate the toxicity of 5-FU to the GI tract and its associated suffering is to deliver the mitigating drug directly to the organ affected by the cancer treatment drug, which causes undesirable organ toxicity, in this case to the GI tract.
• This asymmetric delivery of toxicity prevention only to the tissue subject to the toxicity can allow a higher dose of anti-cancer medicine to be given to treat the cancer.
• compositions and methods for the treatment of the side-effects associated with administration of cancer chemotherapeutic agents are disclosed herein.
• a protective formulation is orally administered to the patient.
• the protective formulation includes at least one natural substrate of at least one enzyme that also metabolizes the cancer therapeutic agent.
• a substrate of an enzyme that metabolizes the cancer therapeutic agent may be any chemical that binds to the enzyme to a degree such that the rate of reaction between the enzyme and the cancer therapeutic agent decreases and the product of the substrate and the enzyme is a normal cell component.
• a protective formulation for 5-FU includes a mixture of adenine (A) and orotate (O) administered orally at concentrations in the range of 0.0074 mM to 2.5 mM of adenine and 0.0064 mM to 2.5 mM of orotate.
• Experimental results in cell culture show 150% viability of control for growth in the presence of 0.625 mM adenine and 1.25 mM orotate with growth at 5 days despite the concomitant exposure to 0.01 mM of 5-FU. Exposure to adenine/orotate concentrations in the range of 0.001- 0.0125 mM, resulted in no meaningful salvage of 5-FU toxicity administered at the physiologic dose of 0.01 mM.
• both adenine and orotate are normal enzyme substrates and generate normal anabolites. There is no toxicity from their use together or without the concomitant exposure to 5-FU.
• Other purine and pyrimidine precursors, such as uracil and inosine do not attenuate, but actually exacerbate, the toxicity of 5-FU to human-derived colon (Caco-2) cells.
• the dosage of 5-FU or its active precursor may be increased so as to more effectively destroy the existing cancerous tumor.
• 5-FU is not being metabolized in the gastrointestinal tract, more 5-FU is available for destruction of the targeted cancerous tumor.
• the toxic side-effects associated with 5-FU metabolism have been ameliorated by the compositions and methods, normal homeostasis is maintained in the GI tract and patients receiving 5-FU for cancer therapy are more likely to adhere to the treatment regimen recommended by their physician.
• the combination of increased compliance and increased dosage of 5-FU afforded by the compositions and methods improves the outcome associated with 5-FU cancer treatment therapy.
• adenine and orotate are delivered via an osmotically-controlled oral drug delivery system (see, for example, Verma, et ah, "Osmotically Controlled Oral Drug Delivery", Drug Development and Industrial Pharmacy, Vol. 26, pp. 695-708, 2000).
• This system preferably delivers adenine and orotate to all the columnar cells throughout the GI tract.
• the protective formulation includes cationic liposomes containing one or more of various purine/pyrimidine precursors that are administered orally to patients receiving 5-FU for cancer treatment.
• the cationic liposomes containing the purine/pyrimidine precursors bind to the cells lining the mucosa of the intestinal tract. After binding to the cells lining the mucosa of the intestinal tract, the substrate contents of the cationic liposomes are deposited into the interior of the cells lining the mucosa of the intestinal tract.
• the liposomally-transfected substrates prevent the metabolism of 5-FU into a toxic species, thereby protecting those cells, into which the cationic liposome has been deposited, from the toxicity associated with administration of 5-FU.
• the liposomally-transfected substrates protect the cells lining the mucosa of the intestinal tract from any toxicity associated with the administration of the substrate orotate.
• chemotherapeutic drug administration disclosed herein employ substrates of the enzymes which the human body uses to metabolize the cancer treatment drug.
• the substrates of the enzymes are incorporated into slow-release capsules.
• a particularly well-suited drug delivery format is an osmotically-controlled drug delivery system.
• a preferred use would be for the device to deliver the purine/pyrimidine precursor drug to the columnar cells throughout the GI tract, which extends from the base of the squamous cell-lined esophagus to the squamous cell-lined anus.
• the push-pull osmotic pump (PPOP) can provide the optimal zero-order release rate kinetics (see, for example, Verma et al).
• the PPOP has been used to deliver drugs such as indomethacin and levodopa.
• Alternative delivery vehicles include devices such as pH- dependent, enzyme degradation-dependent, and matrix- or polymer-dependent devices.
• the substrates of the enzymes are incorporated into cationic liposomes.
• Such metabolic by-products and enzyme substrates are incorporated into the cationic liposomes to prevent the damage caused by the cancer drug.
• Oral administration of the slow-release capsules or cationic liposomes promotes incorporation of the enzyme substrates into the cells lining the mucosa of the intestinal tract to which the cancer drug is toxic. Thereby, the toxic effect of the cancer drug is minimized.
• These substrates of the enzymes used to metabolize the cancer treatment drug are nontoxic to normal tissues.
• the substrates of the enzymes used to metabolize the cancer treatment drug are delivered only to the cells lining the mucosa of the intestinal tract and do not interfere with the activity of the cancer chemotherapeutic drug on the cancerous tumor to which the cancer chemotherapeutic drug is directed.
• compositions and methods may be adapted for alleviating the gastrointestinal effect of any administered drug regiment, the compositions and methods are preferably specifically directed to a composition and method for alleviating the gastrointestinal side-effects of 5-fluorouracil (5-FU).
• the principle of applying locally an agent to reverse the toxicity of a chemotherapy agent may be applicable to alleviating the side-effects of other cancer chemotherapeutic drugs which cause GI toxicity.
• the cancer chemotherapeutic agent, 5-FU is one of the first cancer drugs identified and is commonly used in the treatment of cancers of the colon, breast, stomach, and other organs of the body.
• the common side-effects of 5-FU administration are nausea and diarrhea because of the toxicity exerted by 5-FU on the cells lining the mucosa of the intestinal tract.
• the metabolic pathway for 5-FU is widely known.
• the chemical 5-FU is inactive against cancerous tumors until it is metabolized by the body to the active species.
• Anabolism of 5-FU to its active species is accomplished by one of three alternate enzyme systems, which are as follows: 1) uridine phosphorylase (UP), 2) thymidine phosphorylase (TP), and 3) orotate phosphoribosyl transferase (OPT).
• UP uridine phosphorylase
• TP thymidine phosphorylase
• OPT orotate phosphoribosyl transferase
• Saturation of the active site of an enzyme with such a substrate decreases the availability of the enzyme for accepting the alternative substrate (e.g., 5-FU) at the active site of the enzyme, where it is metabolized by the enzyme. If a substance has decreased the active access to the enzyme, clearly this substrate is metabolized less by the enzyme.
• the alternative substrate e.g., 5-FU
• Fig. 5 and Fig. 6 show the effect of different combinations of adenine (A), orotate (O), and uracil (U), either in liposomes or without liposomes, in mediating the toxicity to growth of 5-FU for human skin cells in cell culture after incubation at 37 °C.
• the concentration of 5-FU was also 0.01 mM in these trials.
• the concentration of adenine and orotate, when present, was 2.5 mM.
• the relative viability of the cells was determined after 48 hours (Fig. 5) or 72 hours (Fig. 6).
• the inclusion of uracil with adenine and orotate actually increases the protection of the human skin cells against 5-FU toxicity, as shown in Fig. 5 and Fig. 6 (Results
• OPT on 5-FU is decreased by the presence of an excess by saturating the active sites on the enzyme OPT by the natural substrate orotate.
• the production of toxic metabolite of 5- FU is reduced by the metabolism of 5-FU by the enzyme OPT because the active site of the enzyme OPT is filled with the competing substrate orotate.
• the competing substrate orotate inhibits 5-FU from entering the active site of the enzyme OPT, where it can be further metabolized to the toxic product.
• Orotate, in comparison to 5-FU is an acid with a much lower pK and therefore is a much better substrate for OPT.
• the competing substrate orotate does not readily enter or exit the cell membrane of the cells lining the mucosa of the intestinal tract, because the substrate orotate has an acidic pK and an overall negative charge, as do the cell membranes of the cells lining the mucosa of the intestinal tract.
• the orotate is not charged and is better absorbed into the systemic circulation (see, for example, Robinson et al, "Effects of Orotic Acid Ingestion on Urinary and Blood Parameters in Humans", Nutrition Research, Vol. 3, pp. 407-415, 1983).
• 5-FU is also, alternatively, metabolized to its toxic form by the two enzymes UP and TP.
• Uracil can compete for anabolism with 5-FU via TP and UP.
• the active site on the UP and TP enzymes are filled with uracil, thereby decreasing the rate of metabolism of 5-FU by enzymes UP and TP to the toxic form.
• the gland cells (columnar cells) that line the GI tract rely little on the salvage pathways of UP and TP. The result is that the use of uracil increases the toxicity of 5-FU.
• uracil competes well with 5-FU for UP and TP but is not active at all as a substitute for OPT because of its even higher pK than 5- FU (pK of uracil of 9.45 » pK of 5-FU of 7.8).
• TP/UP in preference to OPT, are formed as squamous cells salvage pyrimidines to grow, as shown in Fig. 5 and Fig. 6.
• orotate does not impact skin (squamous) cell response to 5-FU exposure.
• the competing substrate dietary orotate is nontoxic and requires facilitated transport to exit the cell because of its charge at neutral pH.
• the orotate At low pH, as in the stomach, the orotate is not ionized and is absorbed at a higher rate (see, for example, Robinson et al). Then the orotate/adenine mixture may be given together with a protein pump inhibitor (PPI), such as omeprazole, to retain orotate within the GI tract and reduce systemic exposure to orotate.
• PPI protein pump inhibitor
• APRT phosphoribosyltransferase
• AMD adenosine monophosphate deaminase
• IMP inosine monophosphate
• the present methods and compositions may have much wider application to treat GI disorders.
• the exposure of human-derived colon (Caco-2) cells grew better in the presence of a combination of adenine, orotate, and 5-FU than controls without 5-FU.
• Adenine has in the past been noted to prolong the shelf life of stored blood (see, for example, Bartlett, "Erythrocyte Metabolism", pp. 10-13 in Adenine and Red Cell Storage, The Human Red Cell in Vitro, Greenwald et al., ed., New York: Grune and Stratton, 1974).
• adenine and orotate are orally administered to a patient, where either adenine or orotate is limiting in availability in the patient.
• the gastrointestinal distress may have any of a number of different causes and need not necessarily be caused by administration of 5-FU, or for that matter, another administered drug to the patient.
• Adenine unlike orotate, is uncharged and well-absorbed systemically. Adenine can, however, then be oxidized to 2,8-dihydroxy adenine. 2,8-dihydroxy adenine is poorly soluble and can cause renal stones (see, for example, Van Acker et ah, "Complete Deficiency of Adenine Phosphoribosyltransferase", The New England Journal of
• Adenine also can reverse the systemic toxicity of 5-FU at high doses, which is another reason adenine exposure must be kept to a minimum.
• Fig. 2 shows that 1.25 mM orotate and 0.125 mM adenine can protect cells from the toxicity of 0.01 mM 5-FU exposure to cell growth, whereas decreasing the concentration of adenine to 0.0125 mM with orotate exposure at 1.25 mM offers no protection from the toxicity of 0.01 mM 5-FU exposure to cell growth. It has been estimated that systemic exposure (i.e. by intravenous administration) to adenine in a single dose at 20 mg/kg to a human is safe (see, for example, Bartlett).
• the adenine dosage would be 1.4 g.
• a 0.125-mM solution of adenine in a liter volume of GI fluid would be a 15 mg total body adenine exposure.
• a slow or controlled release dosage of adenine and orotate is given orally. More preferably, the oral delivery is osmotically-controlled oral drug delivery.
• a protein pump inhibitor (PPI) is preferably also given concomitantly to cause secretion of neutral gastric juices to prevent orotate absorption in the stomach.
• allopurinol is preferably administered to decrease conversion of adenine to 2,8-dihydroxy adenine (see, for example, Biihrdel et al, "Adenine Therapy in Lesch-Nyhan Syndrome", Acta Paediatrica Hungarica, Vol. 26, pp. 327-333, 1985).
• a method and composition promote accumulation of the substrate orotate in the cells lining the mucosa of the intestinal trace by incorporating the substrate orotate with certain substrates of the enzymes into cationic liposomes.
• Cationic liposomes carry a net positive charge. This net positive charge enables the cationic liposome to be taken up by the negatively charged outer membranes of the cells lining the mucosa of the intestinal tract.
• the substrate orotate and other substrates of enzymes can be delivered to the cells lining the mucosa of the intestinal tract and then be taken up by the individual cells of the intestinal tract. Once taken up by the individual cells of the intestinal tract, the competing substrate orotate can then reduce the activity of the enzyme OPT in metabolizing 5-FU to its toxic by-product by saturating the active site of the enzyme OPT.
• This saturation of the active site of the enzyme OPT decreases further metabolism of 5-FU by the enzyme OPT.
• the cells lining the mucosa of the intestinal tract are thus relatively protected from the toxic, active 5-FU metabolites.
• the purine/pyrimidine substrates included in the cationic liposome further decrease the metabolism of 5-FU.
• the cationic liposomes because of their charge, minimally permeate the body and release the substrate orotate to alter 5-FU metabolism in the cancerous tumor.
• cationic lipids have been developed and used in cationic liposome preparation. While the cationic lipids have many different chemical structures, cationic lipids are all composed of a cationic head group composed of primary, secondary, tertiary, or quaternary amines. The primary, secondary, tertiary, or quaternary amines are attached to a hydrophobic group via a linker.
• the cationic lipids When placed in an aqueous solution, the cationic lipids form liposomes in which the cationic head is on the outside surface of the liposome and the hydrophobic group is on the inside of the liposome.
• a three dimensional bag or sack is formed.
• the three-dimensional bag or sack contains the substrate orotate and other substrates of enzymes within the interior of the cationic liposome. Since the cationic head of the lipid is located on the surface of the cationic liposome, the positive charge associated with the cationic lipid is located on the outside surface of the cationic liposome.
• cationic lipids include, but are not limited to, Lipofect ACE (Life Technologies), Lipofection (Life Technologies), LipofectAmine (Life Technologies), CeliFectin (Life Technologies), DMRIE-C (Life Technologies), DDAB (Sigma), DC-Choi (Sigma), DOTAP (Boehringer Mannheim, Avanti Polar Lipids, Biontex), MRX-230 and MRX-220 (Avanti Polar Lipids),
• a cationic lipid or a combination of cationic lipids are dissolved in an organic solvent such as chloroform or methanol.
• the solvent is then removed by use of a vacuum or by blowing an inert gas over the solution followed by rehydration in an aqueous solution.
• the aqueous solution used for rehydration contains the substrate orotate and other substrates of enzymes which metabolize the cancer treatment drug.
• the aqueous solution containing the substrate orotate and other substrates of enzymes which metabolize the cancer treatment drug are trapped within the interior of the cationic liposome.
• the cationic liposomes containing the substrate orotate and other substrates of enzymes which metabolize the cancer treatment drug are then made to a uniform size by either sonication or membrane extrusion.
• the cationic liposome is a targeted vector to gastro-intestinal mucosa and does not provide a systemic source of nucleotide precursors.
• liposomes are used to deliver a purine or pyrimidine substrate to the cells lining the mucosa of the intestinal tract without raising the systemic levels of the delivered material.
• the reason for not raising the systemic levels of the delivered material is that a substance such as the substrate orotate may salvage a tumor from the effects of the 5-FU chemotherapy.
• Liposomes have never been used to accomplish this function. Rather, liposomes are typically used to cause a substance to enter a cancerous tumor or to enter into an organ such as the liver.
• a substance like the substrate orotate is used only to get into the cells lining the mucosa of the intestinal tract. Such function then becomes an asymmetric drug delivery system and method where different amounts of a drug are delivered to different parts of the body.

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