Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Acyclic nitrogen double bonded to acyclic nitrogen – acyclic...
Reexamination Certificate
1997-04-07
2001-02-20
Gerstl, Robert (Department: 1613)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Acyclic nitrogen double bonded to acyclic nitrogen, acyclic...
C514S153000, C548S151000, C548S154000
Reexamination Certificate
active
06191124
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to compounds useful for inhibiting a retrovirus in a human cell infected with said retrovirus. More particularly, the present invention provides imidazo[2,1-b]thiazole derivatives as HIV-proteinase inhibitors.
BACKGROUND OF THE INVENTION
During the past decade, acquired immunodeficiency syndrome (AIDS) has progressed from having the status of a medical curiosity afflicting only a small number of individuals to a problem of major proportions, both medically and economically. John Saunders and Richard Storer, “New Developments in RT Inhibitors,” DN&P 5(3), April 1992, pages 153-169. WHO figures reveal that more than 360,000 cases of AIDS have been reported worldwide, including nearly 175,000 cases in the U.S.A. Of these, approximately 100,000 worldwide (50,000 in the U.S.A.) were reported in the preceding 12-month period and WHO estimated over one million new infections during the first half of 1992. In the U.S.A., the number of seropositive individuals is thought to be approximately two million, and estimates suggest that 5-10 million people worldwide may be seropositive. Saunders and Storer, page 153.
Since the first description of the malady in the early part of this decade, acquired immunodeficiency disease syndrome (AIDS) and its devastating consequences have been subjects of continuous and intense coverage in both the lay and scientific press. Indeed, an edition of Scientific American was entirely devoted to AIDS (Scientific American 289, #4 (1988)), and the literature on the disease and the virus is already so vast as to defy thorough citation.
On Mar. 20, 1987, the FDA approved the use of the compound, zidovudine (AZT), to treat AIDS patients with a recent initial episode of pneumocystis carinii pneumonia, AIDS patients with conditions other than pneumocystis carinii pneumonia or patients infected with the virus with an absolute CD4 lymphocyte count of less than 200/mm
3
in the peripheral blood. AZT is a known inhibitor of viral reverse transcriptase, an enzyme necessary for human immunodeficiency virus replication. U.S. Pat. No. 4,724,232 claims a method of treating humans having acquired immunodeficiency syndrome utilizing 3′-azido-3′-deoxy-thymidine (azidothymidine, AZT).
Following the discovery of the anti-HIV activity of AZT, much effort has been focused on a wide variety of other dideoxynucleoside analogues in the search for superior agents. In the case of the 2′,3′-dideoxy series, ddC and ddI have shown potent activity against HIV in vitro and have been evaluated in clinical trials. Saunders and Storer, page 160. The compound ddC is currently being developed by Hoffman-La Roche Co. as a potential anti-AIDS drug. Its limiting toxicity in humans is peripheral neuropathy which is reversible at low doses. Raymond R. Schinazi, Jan R. Mead and Paul M. Feorino, “Insights Into HIV Chemotherapy,” AIDS Research and Human Retroviruses, Vol. 8, Number 6, 1992, pages 963-990. It has been approved by the FDA for AIDS therapy in combination with AZT. The compound ddI has also been evaluated in clinical trials. Its limiting toxicities are peripheral neuropathy and pancreatitis. It has also been shown to stimulate hepatic glycolysis leading to irreversible liver damage. Schinazi, Mead and Feorino, page 966. It has recently been approved by the FDA for the treatment of HIV-1 infections in adults and pediatric patients who are intolerant to or whose health has significantly deteriorated while on AZT treatment. Schinazi, Mead and Feorino, page 966.
Among these approved drugs, AZT is currently the only drug that has been shown to decrease the morality and frequency of opportunistic infections associated with AIDS. Schinazi, Mead and Feorino, page 963.
Human immunodeficiency virus (HIV) has long been recognized as the causative agent in AIDS, although a minority opinion to the contrary has been expressed (e.g., P. Duesberg, Proc. Natl. Acad. Sci., USA, 86:755-764 (1989)). Sequence analysis of the complete genomes from several infective and non-infective HIV-isolates has shed considerable light on the make-up of the virus and the types of molecules that are essential for its replication and maturation to an infective species. The HIV protease is essential for the processing of the viral gag and gag-pol polypeptides into mature virion proteins. L. Ratner, et al., Nature, 313:277-284 (1985); L. H. Pearl and W. R. Taylor, Nature, 329:351 (1987). HIV exhibits the same gag/pol/env organization seen in other retroviruses. L. Ratner, et al., above; S. Wain-Hobson, et al., Cell, 40:9-17 (1985); R. Sanchez-Pescador, et al., Science, 227:484-492 (1985); and M. A. Muesing, et al., Nature, 313: 450-458 (1985).
Reverse transcriptase (RT) is an enzyme unique to retroviruses that catalyzes the conversion of viral RNA into double stranded DNA. Blockage at any point during the transcription process, by AZT or any other aberrant deoxynucleoside triphosphate incapable of elongation, should have dramatic consequences relative to viral replication. Much work on the RT target is in progress based, in large measure, upon the fact that nucleosides like AZT are easily delivered to cells. However, the inefficiency of phosphorylation steps to the triphosphate, and the lack of specificity and consequent toxicity, constitute major drawbacks to use of AZT and similar nucleosides having a blocked, or missing, 3′hydroxyl group.
The T4 cell receptor for HIV, the so-called CD4 molecule, has also been targeted as an intervention point in AIDS therapy. R. A. Fisher, et al., Nature, 331:76-78 (1988); R. E. Hussey, et al., Nature, 331:78-81 (1988); and K. C. Deen, et al., Nature, 331:82-84 (1988). The exterior portion of this transmembrane protein, a molecule of 371 amino acids (sCD4) has been expressed in Chinese hamster ovary (CHO) cells and Genentech (D. H. Smith, et al., Science, 238:1704-1707 (1987)) has had a product in clinical trials since the fall of 1987. CD4 has been shown to have a narrow spectrum of activity against wild-type virus and so far has failed to control HIV infection in humans. Schinazi, Mead and Feorino, page 963. The idea behind CD4 based therapy is that the molecules can neutralize HIV by interfering with viral attachment to T4, and other cells which express CD4 on their surfaces. A variant on this theme is to attach cell toxins to CD4 for specific binding and delivery to infected cells which display glycoprotein gp-120 on their surfaces. M. A. Till, et al., Science, 242:1166-1168 (1988); and V. K. Chaudhary, et al., Nature, 335:369-372 (1988).
Another therapeutic target in AIDS involves inhibition of the viral protease (or proteinase) that is essential for processing HIV-fusion polypeptide precursors. In HIV and several other retroviruses, the proteolytic maturation of the gag and gag/pol fusion polypeptides (a process indispensable for generation of infective viral particles) has been shown to be mediated by a protease that is, itself, encoded by the pol region of the viral genome. Y. Yoshinaka, et al., Proc. Natl. Acad. Sci. USA, 82:1618-1622 (1985); Y. Yoshinaka, et al., J. Virol., 55:870-873 (1985); Y. Yoshinaka, et al., J. Virol., 57:826-832 (1986); and K. von der Helm, Proc. Natl. Acad. Sci., USA, 74:911-915 (1977). Inhibition of the protease has been shown to inhibit the processing of the HIV p55 in mammalian cell and HIV replication in T lymphocytes. T. J. McQuade, et al., Science, 247:454 (1990).
The protease (or proteinase), consisting of only 99 amino acids, is among the smallest enzymes known, and its demonstrated homology to aspartyl proteases such as pepsin and renin (L. H. Pearl and W. R. Taylor, Nature, 329: 351-354 (1987); and I. Katoh, et al., Nature, 329:654-656 (1987)), led to inferences regarding the three-dimensional structure and mechanism of the enzyme (L. H. Pearl and W. R. Taylor, above) that have since been borne out experimentally. Active HIV protease has been expressed in bacteria (see, e.g., P. L. Darke, et al., J. Biol. Chem., 264:2307-2312 (1989)) and chemically synth
Darnley James D.
Gerstl Robert
Pharmacia & Upjohn Company
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