The present invention is in the pharmaceutical area, and in particular relates to pharmaceutical compositions containing 5'-diphosphohexose and 5'-diphosphohexosamine derivatives of nucleosides.
Acquired immunodeficiency syndrome ("AIDS") was recognized as early as 1979. The number of cases reported to the Centers for Disease Control (CDC) has increased dramatically each year since then, and in 1982 the CDC declared AIDS a new epidemic. Infection with the AIDS virus is highly variable. Initially, the virus replicates abundantly, with virus present in the central nervous system and the cells of the immune system. This is frequently accompanied by fevers, rashes, flulike symptoms and neurological complaints. These symptoms generally disappear within a few weeks, as the amount of virus in the circulation drops. However, virus is still present in the immune cells, the cells of the nervous system, cells of the intestine and bone marrow cells. The victim typically dies two to ten years after the initial asymptomatic period, following a protracted and painful illness.
Human immunodeficiency virus, a retrovirus, is the etiological agent of AIDS, as well as of a variety of related disorders, such as AIDS Related Complex (ARC). HIV infection begins when a virion or virus-infected cell binds to susceptible cells and fuses with them, injecting the core protein and viral RNA into the cell. The RNA is transcribed to viral DNA. The double stranded DNA migrates to the nucleus and is integrated into the cell's DNA. The viral DNA can remain dormant for an indefinite period of time, or the genes can replicate and be translated into viral proteins. The viral proteins are assembled into new virions that bud from the cell, spreading the disease.
HIV preferentially infects the T4 lymphocytes, immune cells important in helping to suppress infection by other agents, thereby impairing proper functioning of the immune system. As a result of impaired immunity caused by the destruction of helper T-cells by the HIV, the host becomes susceptible to opportunistic infections, various types of cancer such as Kaposi's sarcoma, and other disorders associated with reduced functioning of the immune system.
A variety of approaches have been developed to treat AIDS infections, including inhibiting the binding of the virus to host cells with dextran sulfate or soluble CD4 (a glycoprotein found on the surface of cells of the immune system which the HIV binds to when infecting the cells), administration of anti-idiotypic antibodies (an antibody to the antibody against CD4), blockage of viral protein synthesis by compounds such as phosphorothioate, and inhibition of protein glycosylation by compounds such as 2-deoxy-D-glucose. However, these approaches are still in early experimental phases, and have not been approved for clinical treatment.
AIDS and ARC chemotherapy have been recently reviewed by Schinazi, Strategies and Targets for Anti-Human Immunodeficiency Virus Type 1 Therapy, "Aids in Children, Adolescents, and Heterosexual Adults: An Interdisciplinary Approach to Prevention," Elsvier, N.Y. 1988); E. D. Clercq, J. Med. Chem. 29, 1561-1569 (1986); H. Mitsuya, S. Broder, Nature 325, 773-778 (1987); and R. Yarchoan, et al., "AIDS Therapies" The Science of AIDS Scientific American (W. H. Freeman and Co. N.Y. 1989).
A number of nucleosides have been found to have anti-HIV activity, including 3'-azido-3'-deoxythymidine (AZT), 2',3'-dideoxycytidine (DDC), 2',3'-dideoxyadenosine (DDA), 3'-azido-2',3'-dideoxyuridine (AzddU), 2',3'-didehydro-2',3'-dieoxycytidine, 3'-deoxy-2',3'-didehydrothymidine, 3'-azido-5-ethyl-2',3'-dideoxyuridine (AzddEU), 3'-azido-5-methyl-2',3'-dideoxycytidine (AzddMeC), 9-(2,3-Dideoxy-2-halo-.beta.-D-arabinofuranosyl)-N.sup.6 -methyladenine (2'-halo-D.sub.2 MeA), and N.sup.6 -methyl-D-glycero-2',3'-dideoxyfuranosyladenosine (D.sub.2 MeA). The present application is a continuation-in-part of applications directed to AzddU.
It is generally accepted that the active form of nucleosides such as AZT, AzddU, AzddMeC, D.sub.2 MeA, and DDC is the triphosphorylated derivative. Triphosphorylated deoxynucleosides appear to inhibit the replication of HIV by limiting the production of viral DNA by at least two mechanisms: competitive inhibition of reverse transcriptase and chain termination of viral DNA due to the missing 3'-hydroxyl group.
The therapeutic effectiveness of all of the known active nucleosides depends on how easily the nucleoside can enter cells and undergo phosphorylation by cellular enzymes. The efficiency of this process varies considerably among nucleosides, and can severely limit the usefulness of the compounds. For example, nucleoside triphosphates without modification, are not useful clinically, since they cannot pass through the cell membrane, even though the triphosphate may have greater antiviral activity.
Nucleosides are also converted by intracellular enzymes into less active metabolites. If the conversion rate to less active compounds is faster than the rate of triphosphorylation of the nucleoside, the pharmaceutical effectiveness of the nucleoside is diminished. For example, it is known that DDA in the triphosphate form is a potent HIV inhibitor in vitro, but in vivo the enzyme adenosine deaminase rapidly converts DDA to the less active DDI (2',3'-dideoxyinosine) before DDA can be phosphorylated. DDI-5'-monophosphate must then be converted to DDA-5'-monophosphate by cellular enzymes to restore the activity of the compound.
The therapeutic effectiveness of a drug is the determining factor in the dosage required for therapy. Nucleosides that pass through the cell membrane with difficulty or which are metabolized into less active or inactive forms in the cell must be administered in higher dosages. Unfortunately, most nucleosides are toxic to healthy uninfected cells at high dosage levels.
AZT has been studied extensively in humans for treatment of HIV infections. However, bone marrow toxicity and other side effects limit its long term usefulness. For example, Richman, et al., have shown that because of AZT-associated hematological abnormalities, twenty-one percent of patients undergoing AZT therapy required multiple blood transfusions during the six month treatment period. Bone marrow depression may be due to the accumulation of phosphorylated AZT within cells, which may result in a substantial depression of thymidine 5'-triphosphate pools. Another drawback of AZT is its short half life in humans (about 1.1 hour) and its elimination in urine as 3'-azido-3'-deoxy-5'-glucuronylthymidine, a metabolite with no substantial antiviral activity.
Many nucleoside derivatives have been developed that have anticancer, anti-bacterial, and anti-fungal activity. Effective therapy with these nucleosides, as with the anti-HIV nucleosides, is significantly affected by the ability of the nucleoside to pass through the cell membrane and diffuse to the active site before the compound is converted to an inactive form or eliminated.
Nucleoside diphosphate sugars are used in vivo for the synthesis of oligosaccharides, polysaccharides, glycolipids, glycoproteins, and components of bacterial cell membranes. Certain nucleoside derivatives have been found to block the glycosylation of proteins. However, most, if not all, known nucleoside glycosylation inhibitors show little selectivity and have low activity against viral infections.
Camarasa, et al., J. Med. Chem., 28, 40 (1985) reported that uridine 5'-diphosphate glucose analogues, 5'-O-[[[[(2",3",4",6"-tetra-O-benzyl- and 2",3",4",6"-tetra-O-benzoyl-.alpha.-D-glucopyranosyl)oxyl]carbonyl]ami no]sulfonyl]-2',3'-isopropylideneuridine (P-536), a UDP-glucose analog, and the corresponding deisopropylidenated derivatives, show in vitro antiviral activity against herpes simplex virus type 1. Alarcon, et al., in Antimicrobial Agents and Chemotherapy 1257, (1988) reported that P-536 has broad antiviral activity, including activity against adenovirus type 5, vaccinia virus, and poliovirus type 1. The compound was demonstrated to inhibit protein glycosylation if added at a time when late viral proteins were being synthesized, and to inhibit the synthesis of nucleic acids and phosphorylation of nucleosides. Alcina, et al., Antimicrobial Agents and Chemotherapy, 1412 (1988), later demonstrated that the same compound has activity against the flagellated protozoan Trypanosoma cruzi.
In light of the state of the art, it is clear that there is a strong need for biologically active nucleoside derivatives that can pass through a cell membrane and reach the active site prior to conversion to inactive metabolites or elimination.
It is therefore an object of the present invention to provide nucleoside derivatives that have enhanced antiviral, antibacterial, antifungal or anticancer activity.
It is a further object of the present invention to provide nucleoside derivatives that can easily pass through a cell membrane in the proper chemical form to perform a desired biological function, or a chemical form.
It is a still further object of the present invention to provide a method to enhance the cellular levels of nucleosides.