Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Having -c- – wherein x is chalcogen – bonded directly to...
Reexamination Certificate
2001-10-30
2003-04-29
Reamer, James H. (Department: 1614)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Having -c-, wherein x is chalcogen, bonded directly to...
C514S459000, C514S460000, C424S455000
Reexamination Certificate
active
06555558
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to unique oral dosage formulations of 5,6-dihydro-4-hydroxy-2-pyrones compounds. In particular, the present invention relates to a substantially alcohol-free and propylene glycol-free, microemulsion formulation of 5,6-dihydro-4-hydroxy-2-pyrone protease inhibitors, which formulation substantially improves bioavailability and stability at room temperature.
2. Background of the Related Art
Since the identification of acquired immunodeficiency syndrome (AIDS) in the early 1980s, AIDS and its devastating consequences have become a subject of intense coverage in the press and study in the scientific literature. It is widely held that such syndrome is due to infection with a retrovirus commonly referred to as the human immunodeficiency virus (HIV). From its identification nearly twenty years ago until today, AIDS has progressed from a medical curiosity affecting only a small population to a problem of major proportion. Millions of people in the United States alone are believed to be seropositive for HIV.
The first drug approved for the treatment of HIV infected individuals was zidovudine (AZT) on Mar. 20, 1987. Zidovudine or AZT was approved to treat AIDS patients with recent initial episodes of pneumocystis carinii pneumonia, carinii pneumonia or patients infected with the virus and having an absolute CD4 lymphocyte count of less than 200/mm
3
in the peripheral blood. AZT is believed to work by inhibiting viral reverse transcriptase, an enzyme necessary for human immunodeficiency virus replication.
In a very short period of time, the number of approved anti-retroviral drugs has increased from one drug with modest activity to twelve with substantial potency. The approved anti-retroviral drugs represent three classes: the nucleoside analog reverse transcriptase inhibitors; the non-nucleoside analog reverse transcriptase inhibitors; and the protease inhibitors. Highly active anti-retroviral therapy (known as “HAART”) almost invariably includes a protease inhibitor in combination with one or more drugs from the other classes. Protease inhibitors as a class demonstrate potent anti-retroviral activity.
The first protease inhibitor was approved by the U.S. Food and Drug Administration (“U.S. FDA”) in 1995, and such class of drugs can be said to have revolutionized the treatment of HIV infection. The protease inhibitors may be characterized as having converted what was once considered to be a uniformly fatal disease to a more treatable, chronic infectious disease. Presently there are five protease inhibitors approved by the U.S. FDA: amprenavir, indinavir, nelfinavir, ritonavir and saquinavir.
Retroviral proteases are enzymes essential for maturation of viral particles to their infectious stages. Inhibition of the proteases, or their absence or non-functionality, results in the virus being unable to efficiently replicate, thereby preventing the production of infective viral particles. For example, the retroviral protease “gag-protease,” one of the smallest enzymes yet characterized (consisting of only 99 amino acids and demonstrating homology to aspartyl proteases such as pepsin and renin) is responsible for the correct proteolytic cleavage of the precursor proteins that are produced from the genome regions coding for the “group specific antigens” (“gag”). The protease is believed to be encoded by the “pol” region of the viral genome, which also contains regions for reverse transcriptase and integrase. Gag-protease cleaves the major core protein p24 of HIV-1 and HIV-2 preferentially N-terminally of proline residues; for example, in the divalent residues Phe-pro, Leu-Pro or Tyr-Pro. During cleavage, the structural proteins of the virus core are liberated. In sum, gag-protease is needed for processing HIV-fusion polypeptide precursors permitting maturation of the gag and gag/pol fusion polypeptides, including capsid and replicative enzymes (e.g., reverse transcriptase, integrase).
A number of highly potent HIV protease inhibitors have been described in the literature. By protease inhibitors it is meant a group of compounds that inhibit aspartate proteases of viral origin and which are useful in the prophylaxis or treatment of viral infections caused by retroviruses, such as HIV in mammals. Protease inhibitors can be said to have revolutionized the treatment of HIV infection in that combination therapy using such compounds with inhibitors of viral DNA polymerase reverse transcriptase can result in the apparent complete suppression of virus replication. Resistance to protease inhibitors is believed to be the result of mutations within the retroviral protease coding domain. Unfortunately, with respect to the five currently approved protease inhibitors in the United States, most of these mutations are able to contribute to cross-resistance (Swanstrom et al., Pharmacol. Ther., 86(2): 145-170 (2000)).
HIV protease inhibitors may be peptidemimetic or non-peptidemimetic in nature.
Compounds of a reduced peptidic nature, or non-peptidic nature, generally show improved pharmacokinetic profiles over their peptidic counterparts. Peptidic HIV protease inhibitors frequently demonstrate low bioavailability and rapid excretion owing to rapid gastrointestinal breakdown. In general, non-peptidic compounds have better bioavailability and are not excreted as rapidly.
Presently available non-peptidic proteinase inhibitors may be characterized as hydrophobic and/or lipophilic in character. Because of such solubility characteristic, i.e., poor aqueous solubility, conventional solid and liquid pharmaceutical preparations containing these inhibitors may not be absorbed in a satisfactory manner. Of the various factors that can affect the bioavailability of a drug when administered orally (which include aqueous solubility, drug absorption through the gastrointestinal tract, dosage strength and first pass effect), aqueous solubility is often found to be among the most important factors. Poorly water soluble compounds often exhibit either erratic or incomplete absorption, and thus produce a less than desirable response.
5,6-dihydro-4-hydroxy-2-pyrone compounds are known to be potent inhibitors of retroviral proteases. They are thus useful in inhibiting the replication of the human immunodeficiency virus (strains of HIV-1 or HIV-2 and/or human T-cell leukemia viruses (HTLV-I or HTLV-II) and in preventing AIDS. Such protease inhibitors, however, generally demonstrate extremely poor aqueous solubility. For example, the free acid form of the 5,6-dihydro-4-hydroxy-2-pyrone sulfonamide compound, tipranavir, has an extremely low aqueous solubility of about 10 &mgr;g/ml at a pH of from about 6 to about 7. Nearly 15 capsules per dose, twice a day, of the disodium salt (4.5 grams) must be taken in order to achieve a therapeutic drug level. Attempts to identify other salts of such compounds in solid forms, which would substantially improve aqueous solubility, have not been successful. Formulations of salts of these compounds generally are prone to precipitation of the parent free-acid in the gastrointestinal tract.
Many attempts have been made to improve the bioavailability of non-peptidic protease inhibitors in general, and 5,6-dihydro-4-hydroxy-2-pyrone peptidase inhibitors in particular. There is an art-recognized need for developing improved oral dosage forms of HIV protease inhibitors, which will have suitable oral bioavailability, stability and side effects profiles. Given the low solubility of many non-peptidic protease inhibitors in free and salt form, a number of efforts have been undertaken to deliver the drug in so-called “emulsified” formulations, that is, formulations containing the drug, a hydrophilic phase, and a lipophilic phase. Such strategy may be borrowed from a similar strategy undertaken with respect to solubilization of cyclic poly-N-methylated undecapeptides of the cyclosporin class, the bioavailability of which were significantly improved by mixing them in an emulsion comprising a lipophilic phase of medium-chain fatty ac
Chen Shirlynn
Gunn Jocelyn A.
Boehringer Ingelheim Pharmaceuticals Inc.
Devlin Mary-Ellen M.
Raymond Robert P.
Reamer James H.
Stempel Alan R.
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