Indinavir analogues with blocked metabolism sites as HIV protease inhibitors with improved pharmacological profiles and high potency against PI-resistant viral strains

Novel phenylthiazoles with a tert-butyl moiety: promising antimicrobial activity against multidrug-resistant pathogens with enhanced ADME properties

The structure-activity relationship of a new tert-butylphenylthiazole series, with a pyrimidine linker, was investigated. We wished to expand knowledge of this novel class of antibiotics by generating 21 new derivatives bearing ≥2 heteroatoms in their side chains. Their activity was examined against isolates of methicillin-resistant Staphylococcus aureus (MRSA), Clostridium difficile, Escherichia coli, Neisseria gonorrhoeae, and Candida albicans. Two compounds with 1,2-diaminocyclohexane as a nitrogenous side chain showed promising activity against the highly infectious MRSA USA300 strain, with a minimum inhibitory concentration (MIC) of 4 μg mL-1. One of these two compounds demonstrated potent activity against C. difficile, with a MIC of 4 μg mL-1. Moderate activities against a C. difficile strain with a MIC of 8 μg mL-1 were noted. Some new compounds possessed antifungal activity against a wild fluconazole-resistant C. albicans strain, with MIC values of 4-16 μg mL-1. ADME and metabolism-simulation studies were performed for the most promising compound and compared with lead compounds. Our results revealed that one compound possessed greater penetration of bacterial membranes and metabolic resistance, which aided a longer duration of action against MRSA.

A one-pot protocol for the synthesis of β-ketosulfones from α,α-dibromoketones

A one-pot debromination/sulfonylation strategy was developed for the direct transformation of α,α-dibromoketones into β-ketosulfones in the presence of sulfinate salts in a methanol solution.

Finding the structural requirements of diverse HIV-1 protease inhibitors using multiple QSAR modelling for lead identification

Multiple Quantitative Structure-Activity Relationship (QSAR) analysis is widely used in drug discovery for lead identification. Human Immunodeficiency Virus (HIV) protease is one of the key targets for the treatment of Acquired Immunodeficiency Syndrome (AIDS). One of the major challenges for the design of HIV-1 protease inhibitors (HIV PRIs) is to increase the inhibitory activities against the enzyme to a level where the problem associated to drug resistance may be considerably delayed. Herein, chemometric analyses were performed with 346 structurally diverse HIV PRIs with experimental bioactivities against a sub-type B mutant to develop highly predictable QSAR models and also to identify the effective structural determinants for higher affinity against HIV PR. The QSAR models were developed using OCHEM-based machine learning tools (ASNN, FSMLR, KNN, RF, MANN and XGBoost), with descriptors calculated by eight different software packages. Simultaneously, a Monte Carlo optimization-based QSAR modelling was performed using SMILES and graph-based descriptors to understand fragment and topochemical contributions. To validate the actual predictability of all these models, an additional set of 104 compounds (also with known experimental activities) with slightly different chemical space were employed. This ligand-based study serves as a crucial benchmark for further development of the HIV protease inhibitors with improved activities.

Phenylthiazoles with tert-Butyl side chain: Metabolically stable with anti-biofilm activity

A new series of phenylthiazoles with t-butyl lipophilic component was synthesized and their antibacterial activity against a panel of multidrug-resistant bacterial pathogens was evaluated. Five compounds demonstrated promising antibacterial activity against methicillin-resistant staphylococcal strains and several vancomycin-resistant staphylococcal and enterococcal species. Additionally, three derivatives 19, 23 and 26 exhibited rapid bactericidal activity, and remarkable ability to disrupt mature biofilm produced by MRSA USA300. More importantly, a resistant mutant to 19 couldn't be isolated after subjecting MRSA to sub-lethal doses for 14 days. Lastly, this new series of phenylthiazoles possesses an advantageous attribute over the first-generation compounds in their stability to hepatic metabolism, with a biological half-life of more than 9 h.

Diphenylurea derivatives for combating methicillin- and vancomycin-resistant Staphylococcus aureus

A new class of diphenylurea was identified as a novel antibacterial scaffold with an antibacterial spectrum that includes highly resistant staphylococcal isolates, namely methicillin- and vancomycin-resistant Staphylococcus aureus (MRSA & VRSA). Starting with a lead compound 3 that carries an aminoguanidine functionality from one side and a n-butyl moiety on the other ring, several analogues were prepared. Considering the pharmacokinetic parameters as a key factor in structural optimization, the structure-activity-relationships (SARs) at the lipophilic side chain were rigorously examined leading to the discovery of the cycloheptyloxyl analogue 21n as a potential drug-candidate. This compound has several notable advantages over vancomycin and linezolid including rapid killing kinetics against MRSA and the ability to target and reduce the burden of MRSA harboring inside immune cells (macrophages). Furthermore, the potent anti-MRSA activity of 21n was confirmed in vivo using a Caenorhabditis elegans animal model. The present study provides a foundation for further development of diphenylurea compounds as potential therapeutic agents to address the burgeoning challenge of bacterial resistance to antibiotics.

Phenylthiazole antibiotics: A metabolism-guided approach to overcome short duration of action

Antibacterial resistance is a pressing global health challenge that necessitates the development of new therapeutic agents. Phenylthiazole antibacterial agents have been extensively studied, by our group, as a potential novel class of antibiotics to circumvent the scourge of antibacterial resistance. Previously, the phenylthiazole lead compound 1 was shown to possess potent activity against clinical isolates of methicillin- and vancomycin-resistant Staphylococcus aureus (MRSA and VRSA). The promising activity of this novel class of antibiotics is hampered by their short half-life due to rapid hepatic metabolism. In the present study, a metabolic methylene soft spot in the lead 1 was identified and replaced with an oxygen atom. The newly developed phenylthiazoles, with alkoxy side chains, demonstrate high metabolic stability (t_1/2 > 4 h), while maintaining their potent anti-MRSA activity. Furthermore, compound 5p demonstrated a selective advantage over vancomycin with its ability to kill intracellular MRSA.

Second generation HIV protease inhibitors against resistant virus

BACKGROUND

The AIDS epidemic has spread around the world at an alarming rate. Although the first generation of HIV protease inhibitors, including indinavir, nelfinavir, saquinavir, ritonavir and amprenavir, were initially effective against HIV infection, the fast emerging resistance to these agents has been a substantial and persistent problem in the treatment of AIDS. Attempts to address the resistance issue with 'salvage therapy' consisting of high doses of multiple protease inhibitors have only been moderately successful owing to the high level of cross-resistance and toxicities associated with the protease inhibitors.

OBJECTIVE

To study the second generation HIV protease inhibitors against resistant virus.

METHOD

This review highlights new developments achieved by various organizations to address the challenge of high level resistance of current therapies since 2000.

CONCLUSION

All second generation protease inhibitors used in patients who experienced extensive treatment require ritonavir as a pharmacological boosting agent to increase the drug level in the plasma, but there is toxicity associated with such a practice. Accordingly, there remains a need for new protease inhibitors with improved effectiveness against the resistant viral variants. A third generation protease inhibitor will require no boosting agent while maintaining high potency against resistant virus.

Design and synthesis of HIV-1 protease inhibitors for a long-acting injectable drug application

The design and synthesis of novel HIV-1 protease inhibitors (PIs) (1-22), which display high potency against HIV-1 wild-type and multi-PI-resistant HIV-mutant clinical isolates, is described. Lead optimization was initiated from compound 1, a Phe-Phe hydroxyethylene peptidomimetic PI, and was directed towards the discovery of new PIs suitable for a long-acting (LA) injectable drug application. Introducing a heterocyclic 6-methoxy-3-pyridinyl or a 6-(dimethylamino)-3-pyridinyl moiety (R(3)) at the para-position of the P1' benzyl fragment generated compounds with antiviral potency in the low single digit nanomolar range. Halogenation or alkylation of the metabolic hot spots on the various aromatic rings resulted in PIs with high stability against degradation in human liver microsomes and low plasma clearance in rats. Replacing the chromanolamine moiety (R(1)) in the P2 protease binding site by a cyclopentanolamine or a cyclohexanolamine derivative provided a series of high clearance PIs (16-22) with EC(50)s on wild-type HIV-1 in the range of 0.8-1.8 nM. PIs 18 and 22, formulated as nanosuspensions, showed gradual but sustained and complete release from the injection site over two months in rats, and were therefore identified as interesting candidates for a LA injectable drug application for treating HIV/AIDS.

Synthesis of novel HIV protease inhibitors (PI) with activity against PI-resistant virus

A series of HIV protease inhibitors with modifications on the P3 position have been designed and synthesized. These compounds exhibit excellent antiviral activity against both the wild type enzyme and PI-resistant clinical viral isolates. The synthesis and biological activity of the compounds are described.

Biocatalytic racemization of sec-alcohols and α-hydroxyketones using lyophilized microbial cells

Biocatalytic racemization of aliphatic and aryl-aliphatic sec-alcohols and alpha-hydroxyketones (acyloins) was accomplished using whole resting cells of bacteria, fungi, and one yeast. The mild (physiological) reaction conditions ensured the suppression of undesired side reactions, such as elimination or condensation. Cofactor and inhibitor studies suggest that the racemization proceeds through an equilibrium-controlled enzymatic oxidation-reduction sequence via the corresponding ketones or alpha-diketones, respectively, which were detected in various amounts. Ketone formation could be completely suppressed by exclusion of molecular oxygen. Figure Biocatalytic racemization whole microbial cells.

Orally bioavailable highly potent HIV protease inhibitors against PI-resistant virus

Efforts directed to identifying potent HIV protease inhibitors (PI) have yielded a class of compounds that are not only very active against wild-type (NL4-3) HIV virus but also very potent against a panel of PI-resistant viral isolates. Chemistry and biology are described.

HIV-1 protease inhibitors with picomolar potency against PI-resistant HIV-1 by modification of the P1' substituent

Transposition of the pyridyl nitrogen from the P(3) substituent to the P(1)' substituent in HIV-1 protease inhibitors (PI) affords compounds such as 3 with an improved inhibitory profile against multiple P450 isoforms. These compounds also displayed increased potency, with 3 inhibiting viral spread (CIC(95)) at <8 nM for every strain of PI-resistant HIV-1 tested. The poor to modest bioavailability of these compounds may correlate in part to their aqueous solubility.

HIV protease inhibitors with picomolar potency against PI-Resistant HIV-1 by extension of the P3 substituent

A biaryl pyridylfuran P(3) substituent on the hydroxyethylene isostere scaffold affords HIV protease inhibitors (PI's) with picomolar (IC(50)) potency against the protease enzymes from PI-resistant HIV-1 strains. Inclusion of a gem-dimethyl substituent afforded compound 3 with 100% oral bioavailability (dogs) and more than double the t(1/2) of indinavir. Inhibition of multiple P450 isoforms is dependent on the regiochemistry of the pyridyl nitrogen in these compounds.

Design and synthesis of highly potent HIV protease inhibitors with activity against resistant virus

A series of highly potent HIV protease inhibitors have been designed and synthesized. These compounds are active against various clinical viral isolates as well as wild-type virus. The synthesis and biological activity of these HIV protease inhibitors are discussed.

Synthesis and activity of novel HIV protease inhibitors with improved potency against multiple PI-resistant viral strains

Substitution of the t-butylcarboxamide substituent in analogues of the HIV protease inhibitor (PI) Indinavir with a trifluoroethylamide moiety confers greater potency against both the wild-type (NL4-3) virus and PI-resistant HIV. The trifluoroethyl substituent also affords a slower clearance rate in vivo (dogs); however, this may be due to more potent inhibition of at least two P450 isoforms.