Synthesis and anti-HIV activity of prodrugs derived from saquinavir and indinavir

Piperazine based antimicrobial polymers: a review

Microbial infections are a life threatening concern in several areas, which include the biomedical sector, healthcare products, water purification systems, and food packaging. Polymers with low molecular weight bioactive agents or disinfectants help the scientific community to reduce the lethality rate caused by pathogenic microbes. Antimicrobial polymeric approach is one of the advanced approaches made by researchers in concern with the problems associated with small molecules that restrict their applications in broad spectrum. History reveals the synthesis of numerous antimicrobial polymers using various antimicrobial agents but lacks the use of piperazine molecule, which is of pharmaceutical importance. This review gives an insight into the current and future perspective for the development of piperazine-based antimicrobial polymers.

Identification of potential antivirals against SARS-CoV-2 using virtual screening method

SARS-CoV-2 has triggered a major epidemic among people around the world, and it is the newest in the sequence to become prevalent among other infectious diseases. The drug repurposing concept has been utilized effectively for numerous viral infections. Considering the situation and the urgency, the idea of drug repurposing for coronavirus infection (COVID-19) is also being studied. The molecular docking method was used for the screening of 29 antiviral drugs against primary protease proteins (MPP) of SARS-CoV-2, spike ecto-domain, spike receptor binding domain, Nsp9 RNA binding protein, and HR2 domain. Among these drugs, in terms of least binding energy, Indinavir, Sorivudine, Cidofovir, and Darunavir showed minimum docking scores with all the key proteins. For ADMET (Absorption, Distribution, Metabolism, Excretion and Toxicity) analysis, the ADMET properties of the top 4 drug candidates were retrieved through literature study. This analysis revealed that these drug candidates are well metabolized, distributed, and bioavailable, but have some undesirable effects. Furthermore, some approved structural analogues, such as Telbivudine, Tenofovir, Amprenavir, Fosamprenavir, etc., were predicted as similar drugs which may also be used for treating viral infections. We highly recommend these drug candidates as potential fighters against the deadly SARS-CoV-2 virus, and suggest in vivo trials for experimental validation of our findings.

Synthesis and Characterization of Long-Acting Darunavir Prodrugs

Antiretroviral therapy (ART) has improved the quality of life in patients infected with HIV-1. However, complete viral suppression within anatomical compartments remains unattainable. This is complicated by adverse side effects and poor adherence to lifelong therapy leading to the emergence of viral drug resistance. Thus, there is an immediate need for cellular and tissue-targeted long-acting (LA) ART formulations. Herein, we describe two LA prodrug formulations of darunavir (DRV), a potent antiretroviral protease inhibitor. Two classes of DRV prodrugs, M1DRV and M2DRV, were synthesized as lipophilic and hydrophobic prodrugs and stabilized into aqueous suspensions designated NM1DRV and NM2DRV. The formulations demonstrated enhanced intracellular prodrug levels with sustained drug retention and antiretroviral activities for 15 and 30 days compared to native DRV formulation in human monocyte-derived macrophages. Pharmacokinetics tests of NM1DRV and NM2DRV administered to mice demonstrated sustained drug levels in blood and tissues for 30 days. These data, taken together, support the idea that LA DRV with sustained antiretroviral responses through prodrug nanoformulations is achievable.

Advances in brain targeting and drug delivery of anti-HIV therapeutic agents

INTRODUCTION

Human immunodeficiency virus (HIV) is a neurotropic virus that enters the central nervous system (CNS) early in the course of infection. Although antiretroviral drugs are able to eliminate the majority of the HIV virus in the bloodstream, however, no specific treatment currently exist for CNS infections related to HIV. This is mainly attributed to the poor penetrability of antiretroviral therapy across the blood-brain barrier (BBB), and the protective nature of the BBB. Therefore, in order to increase the efficacy of anti-HIV drugs, novel drug delivery methodologies that can exhibit activity in the CNS are most needed and warranted.

AREAS COVERED

In this review article, the authors discussed the challenges with delivering drugs to the brain especially under HIV infection pathophysiology status. Also, they discussed the approaches currently being investigated to enhance brain targeting of anti-HIV drugs. A literature search was performed to cover advances in major approaches used to enhance drug delivery to the brain.

EXPERT OPINION

If drugs could reach the CNS in sufficient quantity by the methodologies discussed, mainly through intranasal administration and the utilization of nanotechnology, this could generate interest in previously abandoned therapeutic agents and enable an entirely novel approach to CNS drug delivery.

Investigation of oral bioavailability and brain distribution of the Ind(8)-Val conjugate of indinavir in rodents

Protease inhibitors are successfully used for the treatment of acquired immune deficiency syndrome (AIDS) although their biopharmaceutical characteristics are not optimal. Prodrugs have therefore been synthesized to increase protease inhibitor bioavailability and brain distribution. Among several compounds tested, a valine derivative of indinavir (Ind(8)-Val) showed promising characteristics using an in-vitro Caco-2 cell model. The objective of this study was to further investigate this compound using in-situ and in-vivo approaches. The pharmacokinetics of indinavir (Ind) and Ind(8)-Val were investigated in rats after intravenous and oral administration. Free indinavir resulting from in-vivo hydrolysis of Ind(8)-Val could not be detected in the plasma of rats receiving Ind(8)-Val. Furthermore Ind(8)-Val bioavailability was only 32% on average compared with 76% for indinavir, and effective permeability coefficients determined with a single-pass intestinal perfusion method were close to 25 times 106 cms−1 for the two compounds. Brain-to-plasma concentration ratios in the post equilibrium phase after intravenous administration to mice were 9.7 ± 8.1% for indinavir and 2.5 ± 2.7% for Ind(8)-Val. In conclusion, the promising biopharmaceutical characteristics of Ind(8)-Val suggested from previous in-vitro experiments with the Caco-2 cell model were not confirmed by in-situ and in-vivo experiments.

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.

Prodrugs of HIV protease inhibitors—saquinavir, indinavir and nelfinavir—derived from diglycerides or amino acids: synthesis, stability and anti-HIV activity

With the aim of improving the pharmacological properties of current protease inhibitors (PIs), the synthesis of various acyl and carbamate amino acid- or diglyceride-containing prodrugs derived from saquinavir, indinavir and nelfinavir, their in vitro stability with respect to hydrolysis and their anti-HIV activity in CEM-SS and MT4 cells have been investigated. l-Leucine (Leu) and l-phenylalanine (Phe) were connected through their carboxyl to the PIs while l-tyrosine (Tyr) was conjugated through its aromatic hydroxyl via various spacer units. Hydrolysis of the prodrug with liberation of the active free drug was crucial for antiviral activity. The Leu- and Phe-PI prodrugs released the active free drug very rapidly (half-lives of hydrolysis in buffer at 37 degree C of 3-4 h). The Tyr-PI conjugates with a -C(O)(CH(2))(4)- linker exhibited half-lives in the 40-70 h range and antiviral activities in the 21-325 nM range (from 2 to 22 nM for the free PIs). The chemically very stable carbamate "peptidomimetic" Tyr-PI prodrugs (no hydrolysis detected after 7 days in buffer) displayed a very low anti-HIV activity or were even inactive (EC(50) from 2300 nM to >10 microM). A very low antiviral activity was measured for the diglyceride-substituted saquinavir and for all of the disubstituted indinavir and nelfinavir prodrugs. All these prodrugs probably released the active parent PI too slowly under the antiviral assay conditions. These results combined with those from transepithelial transport studies (Rouquayrol et al., Pharm. Res., 2002, 19, 1704-1712) indicate that conjugation of amino acids (through their carboxyl) to the PIs constitutes a most appealing alternative which could improve the intestinal absorption of the PIs and reduce their recognition by efflux carriers.

Transepithelial transport of prodrugs of the HIV protease inhibitors saquinavir, indinavir, and nelfinavir across Caco-2 cell monolayers

PURPOSE

[corrected] This study is dedicated to the permeation of various amino acid-, D-glucose-, and PEG-conjugates of indinavir, saquinavir, and nelfinavir across monolayers of Caco-2 cells as models of the intestinal barrier. This screening is aimed at detecting the most promising prodrugs for improving the intestinal absorption of these protease inhibitors.

METHODS

The bidirectional transport of the prodrugs was investigated using P-gp-expressing Caco-2 monolayers grown on membrane inserts using high-performance liquid chromatography for quantitation.

RESULTS

The L-valyl, L-leucyl, and L-phenylalanyl ester conjugates led to an enhancement of the absorptive flux of indinavir or saquinavir. These results are likely attributable to an active transport mechanism and/or to a decrease of their efflux by carriers such as P-gp. Connection of tyrosine through its hydroxyl, of D-glucose, or of polyethylene glycol decreased their absorptive and secretory diffusion.

CONCLUSIONS

Conjugation of the protease inhibitors to amino acids constitutes a most appealing alternative that could improve their intestinal absorption and oral bioavailability. Whether it could improve their delivery into the central nervous system remains to be explored. D-Glucose conjugation will most probably not improve their intestinal absorption or their crossing of the blood-brain barrier. If some pharmacologic benefits are to be expected from PEG-protease inhibitor conjugates, they must then be administered intravenously.

Synthesis and anti-HIV activity of glucose-containing prodrugs derived from saquinavir, indinavir and nelfinavir

With the aim at improving the transport of the current HIV protease inhibitors across the intestinal and blood brain barriers and their penetration into the central nervous system, the synthesis of various acyl and carbamatoyl glucose-containing prodrugs derived from saquinavir, indinavir and nelfinavir, their in vitro stability with respect to hydrolysis, and their anti-HIV activity have been investigated. D-Glucose, which is actively transported across these barriers, was connected through its 3-hydroxyl to these antiproteases via a linker. The liberation of the active free drug during the incubation time of the prodrugs with the cells was found to be crucial for HIV inhibition. The labile ester linking of the glucose-containing moiety to the peptidomimetic hydroxyl of saquinavir or to the indinavir C-8 hydroxyl, which is not part of the transition state isostere, is not an obstacle for anti-HIV activity. This is not the case for its stable carbamate linking to the peptidomimetic hydroxyl of saquinavir, indinavir and nelfinavir. The chemical stability with respect to hydrolysis of some of the saquinavir and indinavir prodrugs reported here, the liberation rate of the active free drug and the HIV inhibitory potency are acceptable for an in vivo use of these prodrugs. These glucose-linked ester and carbamate prodrugs display a promising therapeutic potential provided that their bioavailability, penetration into the HIV sanctuaries, and/or the liberation of the active free drug from the carbamate prodrugs are improved. Furthermore, no cytotoxicity was detected for the prodrugs for concentrations as high as 10 or even 100 microM, thus indicating an encouraging therapeutic index.