Pharmacology and clinical experience with saquinavir

Protease Inhibitors for the Treatment of HIV/AIDS: Recent Advances and Future Challenges

Acquired Immunodeficiency Syndrome (AIDS) is a chronic disease characterized by multiple life-threatening illnesses caused by a retro-virus, Human Immunodeficiency Virus (HIV). HIV infection slowly destroys the immune system and increases the risk of various other infections and diseases. Although, there is no immediate cure for HIV infection/AIDS, several drugs targeting various cruxes of HIV infection are used to slow down the progress of the disease and to boost the immune system. One of the key therapeutic strategies is Highly Active Antiretroviral Therapy (HAART) or ' AIDS cocktail' in a general sense, which is a customized combination of anti-retroviral drugs designed to combat the HIV infection. Since HAART's inception in 1995, this treatment was found to be effective in improving the life expectancy of HIV patients over two decades. Among various classes of HAART treatment regimen, Protease Inhibitors (PIs) are known to be widely used as a major component and found to be effective in treating HIV infection/AIDS. For the past several years, a variety of protease inhibitors have been reported. This review outlines the drug design strategies of PIs, chemical and pharmacological characteristics of some mechanism-based inhibitors, summarizes the recent developments in small molecule based drug discovery with HIV protease as a drug target. Further discussed are the pharmacology, PI drug resistance on HIV PR, adverse effects of HIV PIs and challenges/impediments in the successful application of HIV PIs as an important class of drugs in HAART regimen for the effective treatment of AIDS.

A semi-mechanistic pharmacokinetic model of saquinavir combined with itraconazole in HIV-1-positive patients

The mechanism of drug-drug interaction between saquinavir, a protease inhibitor used effectively for HIV/AIDS treatment, and itraconazole, an azole antifungal agent, is hypothesized to involve competitive inhibition at CYP3A4 enzyme, an important drug metabolizing enzyme in humans. The resulting interaction between these CYP3A4 substrates can be utilized clinically as a pharmacokinetic booster for prolonging saquinavir dosing regimen and/or decreasing saquinavir dose requirement in HIV/AIDS patients. To quantitatively describe this specific drug-drug interaction, based on the existing data, we aimed to develop a mathematical model incorporated with the competitive inhibition phenomena. PlotDigitizer was used to extract data from literature. Advance Continuous Simulating Language Extreme (ACSLX), a FORTRAN-based computer program, was employed as our developing tool. Our computer model simulations could successfully describe concentration-time course of saquinavir from selected pharmacokinetic studies in HIV-1-positive patients. To extend the model's utility as an aid in saquinavir dosage regimens, the developed model may be applied to other HIV/AIDS patients in genuine clinical settings.

HIV Protease Inhibitors: Effect on the Opportunistic Protozoan Parasites

The impact of highly active antiretroviral therapy (HAART) in the natural history of AIDS disease has been allowed to prolong the survival of people with HIV infection, particularly whose with increased HIV viral load. Additionally, the antiretroviral therapy could exert a certain degree of protection against parasitic diseases. A number of studies have been evidenced a decrease in the incidence of opportunistic parasitic infections in the era of HAART. Although these changes have been attributed to the restoration of cell-mediated immunity, induced by either non-nucleoside reverse transcriptase inhibitors or HIV protease inhibitors, in combination with at least two nucleoside reverse transcriptase inhibitors included in HAART, there are evidence that the control of these parasitic infections in HIV-positive persons under HAART, is also induced by the inhibition of the proteases of the parasites. This review focuses on the principal available data related with therapeutic HIV-protease inhibitors and their in vitro and in vivo effects on the opportunistic protozoan parasites.

Inhibition of HIV-1 virus replication using small soluble Tat peptides

Although the introduction of highly active antiretroviral therapy (HAART) has led to a significant reduction in AIDS-related morbidity and mortality, unfortunately, many patients discontinue their initial HAART regimen, resulting in development of viral resistance. During HIV infection, the viral activator Tat is needed for viral progeny formation, and the basic and core domains of Tat are the most conserved parts of the protein. Here, we show that a Tat 41/44 peptide from the core domain can inhibit HIV-1 gene expression and replication. The peptides are not toxic to cells and target the Cdk2/Cyclin E complex, inhibiting the phosphorylation of serine 5 of RNAPII. Using the Cdk2 X-ray crystallography structure, we found that the low-energy wild-type peptides could bind to the ATP binding pocket, whereas the mutant peptide bound to the Cdk2 interface. Finally, we show that these peptides do not allow loading of the catalytic domain of the cdk/cyclin complex onto the HIV-1 promoter in vivo.