Jayakanth Kankanala

Bio: Jayakanth Kankanala is an academic researcher from University of Minnesota. The author has contributed to research in topics: RNase H & Reverse transcriptase. The author has an hindex of 14, co-authored 45 publications receiving 614 citations. Previous affiliations of Jayakanth Kankanala include University of Leeds.

Design, synthesis, biochemical, and antiviral evaluations of C6 benzyl and C6 biarylmethyl substituted 2-hydroxylisoquinoline-1,3-diones: dual inhibition against HIV reverse transcriptase-associated RNase H and polymerase with antiviral activities.

Abstract: Reverse transcriptase (RT) associated ribonuclease H (RNase H) remains the only virally encoded enzymatic function not targeted by current chemotherapy against human immunodeficiency virus (HIV). Although numerous chemotypes have been reported to inhibit HIV RNase H biochemically, few show significant antiviral activity against HIV. We report herein the design, synthesis, and biological evaluations of a novel variant of 2-hydroxyisoquinoline-1,3-dione (HID) scaffold featuring a crucial C-6 benzyl or biarylmethyl moiety. The synthesis involved a recently reported metal-free direct benzylation between tosylhydrazone and boronic acid, which allowed the generation of structural diversity for the hydrophobic aromatic region. Biochemical studies showed that the C-6 benzyl and biarylmethyl HID analogues, previously unknown chemotypes, consistently inhibited HIV RT-associated RNase H and polymerase with IC50s in low to submicromolar range. The observed dual inhibitory activity remained uncompromised against RT mu...

5'-Silylated 3'-1,2,3-triazolyl Thymidine Analogues as Inhibitors of West Nile Virus and Dengue Virus.

Abstract: West Nile virus (WNV) and Dengue virus (DENV) are important human pathogens for which there are presently no vaccine or specific antivirals. We report herein a 5'-silylated nucleoside scaffold derived from 3'-azidothymidine (AZT) consistently and selectively inhibiting WNV and DENV at low micromolar concentrations. Further synthesis of various triazole bioisosteres demonstrated clear structure-activity relationships (SARs) in which the antiviral activity against WNV and DENV hinges largely on both the 5'-silyl group and the substituent of 3'-triazole or its bioisosteres. Particularly interesting is the 5' silyl group which turns on the antiviral activity against WNV and DENV while abrogating the previously reported antiviral potency against human immunodeficiency virus (HIV-1). The antiviral activity was confirmed through a plaque assay where viral titer reduction was observed in the presence of selected compounds. Molecular modeling and competitive S-adenosyl-l-methionine (SAM) binding assay suggest that these compounds likely confer antiviral activity via binding to methyltransferase (MTase).

Design, Synthesis, and Biological Evaluations of Hydroxypyridonecarboxylic Acids as Inhibitors of HIV Reverse Transcriptase Associated RNase H

Abstract: Targeting the clinically unvalidated reverse transcriptase (RT) associated ribonuclease H (RNase H) for human immunodeficiency virus (HIV) drug discovery generally entails chemotypes capable of chelating two divalent metal ions in the RNase H active site. The hydroxypyridonecarboxylic acid scaffold has been implicated in inhibiting homologous HIV integrase (IN) and influenza endonuclease via metal chelation. We report herein the design, synthesis, and biological evaluations of a novel variant of the hydroxypyridonecarboxylic acid scaffold featuring a crucial N-1 benzyl or biarylmethyl moiety. Biochemical studies show that most analogues consistently inhibited HIV RT-associated RNase H in the low micromolar range in the absence of significant inhibition of RT polymerase or IN. One compound showed reasonable cell-based antiviral activity (EC50 = 10 μM). Docking and crystallographic studies corroborate favorable binding to the active site of HIV RNase H, providing a basis for the design of more potent analogues.

Isoquinoline-1,3-diones as Selective Inhibitors of Tyrosyl DNA Phosphodiesterase II (TDP2)

Abstract: Tyrosyl DNA phosphodiesterase II (TDP2) is a recently discovered enzyme that specifically repairs DNA damages induced by topoisomerase II (Top2) poisons and causes resistance to these drugs. Inhibiting TDP2 is expected to enhance the efficacy of clinically important Top2-targeting anticancer drugs. However, TDP2 as a therapeutic target remains poorly understood. We report herein the discovery of isoquinoline-1,3-dione as a viable chemotype for selectively inhibiting TDP2. The initial hit compound 43 was identified by screening our in-house collection of synthetic compounds. Further structure–activity relationship (SAR) studies identified numerous analogues inhibiting TDP2 in low micromolar range without appreciable inhibition against the homologous TDP1 at the highest testing concentration (111 μM). The best compound 64 inhibited recombinant TDP2 with an IC50 of 1.9 μM. The discovery of this chemotype may provide a platform toward understanding TDP2 as a drug target.

Quest for Novel Chemical Entities through Incorporation of Silicon in Drug Scaffolds

Abstract: In order to optimize a lead molecule for further development, bioisosteric replacements are generally adopted as one of the strategies. Silicon appears to be the right choice as a carbon isostere because of the similarity in chemical properties. Silicon can be strategically introduced in a molecule to modulate its druglike properties, providing medicinal chemists with an unconventional strategy for replacing a carbon atom. Silicon can also be introduced to replace other heteroatoms and can act as a surrogate of functional groups such as olefin and amide as well. The present Perspective focuses on the opportunities that silicon incorporation offers in drug discovery, with an emphasis on case studies where introduction of silicon has created a benefit over its analog. We have tried to highlight all the recent developments in the field and briefly discuss the challenges associated with them.

Ruthenium-Catalyzed Azide Alkyne Cycloaddition Reaction: Scope, Mechanism, and Applications.

Abstract: The ruthenium-catalyzed azide alkyne cycloaddition (RuAAC) affords 1,5-disubstituted 1,2,3-triazoles in one step and complements the more established copper-catalyzed reaction providing the 1,4-isomer. The RuAAC reaction has quickly found its way into the organic chemistry toolbox and found applications in many different areas, such as medicinal chemistry, polymer synthesis, organocatalysis, supramolecular chemistry, and the construction of electronic devices. This Review discusses the mechanism, scope, and applications of the RuAAC reaction, covering the literature from the last 10 years.

Anti-HIV Drug Discovery and Development: Current Innovations and Future Trends

Abstract: The early effectiveness of combinatorial antiretroviral therapy (cART) in the treatment of HIV infection has been compromised to some extent by rapid development of multidrug-resistant HIV strains, poor bioavailability, and cumulative toxicities, and so there is a need for alternative strategies of antiretroviral drug discovery and additional therapeutic agents with novel action modes or targets. From this perspective, we first review current strategies of antiretroviral drug discovery and optimization, with the aid of selected examples from the recent literature. We highlight the development of phosphate ester-based prodrugs as a means to improve the aqueous solubility of HIV inhibitors, and the introduction of the substrate envelope hypothesis as a new approach for overcoming HIV drug resistance. Finally, we discuss future directions for research, including opportunities for exploitation of novel antiretroviral targets, and the strategy of activation of latent HIV reservoirs as a means to eradicate the ...