Fosamprenavir: advancing HIV protease inhibitor treatment options

Decoding molecular mechanism underlying binding of drugs to HIV-1 protease with molecular dynamics simulations and MM-GBSA calculations

HIV-1 protease (PR) is thought to be efficient targets of anti-AIDS drug design. Molecular dynamics (MD) simulations and multiple post-processing analysis technologies were applied to decipher molecular mechanism underlying binding of three drugs Lopinavir (LPV), Nelfinavir (NFV) and Atazanavir (ATV) to the PR. Binding free energies calculated by molecular mechanics generalized Born surface area (MM-GBSA) suggest that compensation between binding enthalpy and entropy plays a vital role in binding of drugs to PR. Dynamics analyses show that binding of LPV, NFV and ATV highly affects structural flexibility, motion modes and dynamics behaviour of the PR, especially for two flaps. Computational alanine scanning and interaction network analysis verify that although three drugs have structural difference, they share similar binding modes to the PR and common interaction clusters with the PR. The current findings also confirm that residues located interaction clusters, such as Asp25/Asp25', Gly27/Gly27', Ala28/Ala28', Asp29, Ile47/Ile47', Gly49/Gly49', Ile50/Ile50', Val82/Val82' and Ile84/Ile84, can be used as efficient targets of clinically available inhibitors towards the PR.

Structure-based identification of small molecules against influenza A virus endonuclease: an in silico and in vitro approach

Influenza viruses are known to cause acute respiratory illness, sometimes leading to high mortality rates. Though there are approved influenza antivirals available, their efficacy has reduced over time, due to the drug resistance crisis. There is a perpetual need for newer and better drugs. Drug screening based on the interaction dynamics with different viral target proteins has been a preferred approach in the antiviral drug discovery process. In this study, the FDA approved drug database was virtually screened with the help of Schrödinger software, to select small molecules exhibiting best interactions with the influenza A virus endonuclease protein. A detailed cytotoxicity profiling was carried out for the two selected compounds, cefepime and dolutegravir, followed by in vitro anti-influenza screening using plaque reduction assay. Cefepime showed no cytotoxicity up to 200 μM, while dolutegravir was non-toxic up to 100 μM in Madin-Darby canine kidney cells. The compounds did not show any reduction in viral plaque numbers indicating no anti-influenza activity. An inefficiency in the translation of the molecular interactions into antiviral activity does not necessarily mean that the molecules were inactive. Nevertheless, testing the molecules for endonuclease inhibition per se can be considered a worthwhile approach.

Immune response and possible therapeutics in COVID-19

COVID-19 has emerged as a pandemic affecting about 213 countries in all the continents of the globe, resulting in more than 37.8 million individuals getting infected and over 1.08 million deaths worldwide, jeopardizing global human health and the economy. This presents an urgent need to develop therapies that target the SARS-CoV2 virus specifically. This review aims at presenting the available information on the coronavirus disease 2019 along with various drugs that are having widespread use until a vaccine candidate is available to aid in the development of therapeutic strategies against COVID-19.

Current perspectives on HIV-1 antiretroviral drug resistance

Current advancements in antiretroviral therapy (ART) have turned HIV-1 infection into a chronic and manageable disease. However, treatment is only effective until HIV-1 develops resistance against the administered drugs. The most recent antiretroviral drugs have become superior at delaying the evolution of acquired drug resistance. In this review, the viral fitness and its correlation to HIV-1 mutation rates and drug resistance are discussed while emphasizing the concept of lethal mutagenesis as an alternative therapy. The development of resistance to the different classes of approved drugs and the importance of monitoring antiretroviral drug resistance are also summarized briefly.

Exploration of 4(1H)-pyridones as a novel family of potent antimalarial inhibitors of the plasmodial cytochrome bc1

A novel family of antimalarials based on the 4(1H)-pyridone scaffold is described. The compounds display potent antimalarial activity against Plasmodium falciparum in vitro and in vivo. Like atovaquone, 4(1H)-pyridones exert their antimalarial action by inhibiting selectively the electron-transport chain in P. falciparum at the cytochrome bc1 level (complex III). However, despite the similar mechanism of action, no cross-resistance with atovaquone has been found, suggesting that the binding mode of 4(1H)-pyridones might be different from that of atovaquone. The medicinal chemistry program, focused on improving potency and physicochemical properties, ultimately led to the discovery of GSK932121, which was progressed efficiently into first time in human studies. However, progression of GSK932121 was terminated when new toxicology results were obtained in the rat with a soluble phosphate prodrug of the candidate, indicating a potentially narrow therapeutic index.

Evaluation of in vitro models for screening alkaline phosphatase-mediated bioconversion of phosphate ester prodrugs

Generating a phosphate prodrug is one of the common approaches for circumventing poor solubility issues of a parent drug. Alkaline phosphatase (ALP) level was determined in rat intestine mucosa scraps, human colon carcinoma (Caco-2) cells, and Madin-Darby canine kidney (MDCK) cells to characterize in vitro models for ALP-mediated phosphate prodrug conversion. In addition, fosphenytoin and fosfluconazole were used as probe prodrugs to evaluate the models. The highest amount of ALP was detected in rat intestinal mucosa scraps, whereas ALP in 5-day cultured MDCK cells was minimal. As anticipated, ALP levels correlated with the parent drug conversion; the shortest cleavage half-life (t(1/2)) was observed in rat mucosa scraps; and MDCK cells showed the slowest conversion. Furthermore, the polarized conversion for the prodrugs was observed in Caco-2 monolayer cells, suggesting the polarized localization of alkaline in differentiated Caco-2 cells. The rate of ALP-mediated conversion was prodrug concentration-dependent with Michaelis-Menten constants of 1160 and 351 microM for fosphenytoin and fosfluconazole, respectively, determined in Caco-2 cells. The results revealed that whereas the intestinal mucosa scraps reserved the highest ALP activities and were shown as a promising in vitro tool for screening the bioconversion of phosphate prodrug, Caco-2 monolayers could provide the predictive information of bioconversion and further offer the capability in characterizing the permeability of prodrug and parent drug.

Insulin resistance and diabetes mellitus associated with antiretroviral use in HIV-infected patients: pathogenesis, prevention, and treatment options

The contribution of current antiretroviral treatment regimens to the long-term survival of HIV-infected individuals is accompanied by increased risk of glucose metabolism abnormalities in this patient population. The risk of insulin resistance and diabetes in HIV-infected patients receiving antiretroviral treatment stems from 2 sources: exposure to the same environmental factors that have led to an increased incidence of these conditions in the general population and the negative effects on glucose metabolism inherent to components of antiretroviral treatment regimens. This article reviews the pathogenesis and diagnosis of insulin resistance and diabetes and the contribution of components of antiretroviral therapy regimens to increased risk for these conditions. Optimization of antiretroviral treatment regimens for HIV-infected patients with or at increased risk for development of abnormalities in glucose metabolism is discussed.

Synthesis and in vitro biological evaluation of valine-containing prodrugs derived from clinically used HIV-protease inhibitors

In an approach to improve the pharmacological properties and pharmacokinetic profiles of the current protease inhibitors (PIs) used in clinics, and consequently, their therapeutic potential, we performed the synthesis of PI-spacer-valine prodrugs (PI=saquinavir, nelfinavir and indinavir; spacer=-C(O)(CH(2))(5)NH-), and evaluated their in vitro stability with respect to hydrolysis, anti-HIV activity, cytotoxicity, and permeation through a monolayer of Caco-2 cells (used as a model of the intestinal barrier), as compared with their parent PI and first generation of valine-PIs (wherein valine was directly connected through its carboxyl to the PIs). The PI-spacer-valine conjugates were prepared in two steps, in good yields, by condensing an acid derivative of the appropriate protected valine-spacer moiety with the PI, followed by deprotection of the valine protecting group. With respect to hydrolysis, we found that the PI-spacer-valine prodrugs were chemically more stable than the first generation of PI-Val prodrugs. Their stabilities correlated with the low to very low in vitro anti-HIV activity measured for those prodrugs wherein the coupling of valine-spacer residue to the PIs was performed onto the peptidomimetic PI's hydroxyl. Prodrugs wherein the coupling of the valine-spacer residue was performed onto the non-peptidomimetic PI hydroxyl displayed a higher antiviral activity, indicating that these prodrugs are also to some extent anti-HIV drugs by themselves. While the direct conjugation of L-valine to the PIs constituted a most appealing alternative, which improved their absorptive diffusion across Caco-2 cell monolayers and reduced their recognition by efflux carriers, its conjugation to the PIs through the -C(O)(CH(2))(5)NH- spacer was found to inhibit their absorptive and secretory transepithelial transport. This was attributable to a drastic reduction of their passive permeation and/or active transport, indicating that the PI-spacer-valine conjugates are poor substrates of the aminoacid carrier system located at the brush border side of the Caco-2 cell monolayer.

Prodrug strategies to overcome poor water solubility

Drug design in recent years has attempted to explore new chemical spaces resulting in more complex, larger molecular weight molecules, often with limited water solubility. To deliver molecules with these properties, pharmaceutical scientists have explored many different techniques. An older but time-tested strategy is the design of bioreversible, more water-soluble derivatives of the problematic molecule, or prodrugs. This review explores the use of prodrugs to effect improved oral and parenteral delivery of poorly water-soluble problematic drugs, using both marketed as well as investigational prodrugs as examples. Prodrug interventions should be considered early in the drug discovery paradigm rather than as a technique of last resort. Their importance is supported by the increasing percentage of approved new drug entities that are, in fact, prodrugs.