Medicinal Chemistry of Indole and Quinoline Derivatives: Trends and Future Directions as Therapeutic Drugs, 2nd Edition

A special issue of Pharmaceuticals (ISSN 1424-8247). This special issue belongs to the section "Medicinal Chemistry".

Deadline for manuscript submissions: 25 July 2025 | Viewed by 804

Special Issue Editor


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Guest Editor
School of Chemistry, Analytical and Biological Chemistry Research Facility, University College Cork, College Road, T12 K8AF Cork, Ireland
Interests: indole, carbazole and quinoline chemistry; identification of new molecular templates for drug discovery; ellipticine derivatives and their mechanism of biological effect; kinase inhibitor design and synthesis of bisindolemaleimides and indolocarbazoles; phytosterols and the toxicity of their oxygenated products; quinolinediones and isoquinolinediones for the treatment of multidrug resistant disease; LCMS in the improvement of pharmaceutical process and impurity profiling
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Special Issue Information

Dear Colleagues,

Nitrogen-containing heterocycles have made an enormous contribution to medicinal and pharmaceutical chemistry since the identification of alkaloids such as morphine and strychnine. The prevalence and potency of nitrogen-containing natural products that incorporate indole and quinoline (with melatonin, quinine, serotonin, and tryptophan being other examples) frame this success.  The two bicyclic ring systems have provided a rich source of diversity, upon which medicinal and pharmaceutical chemistry have thrived, and multiple examples of therapeutics with real-life benefits exist. Examples on the WHO Essential Medicines List stretch from chloroquine (discovered in 1934) to ciprofloxacin, fluvastatin, indomethacin, mefloquine, ondansetron, primaquine, quinine, and sumatriptan. More recently, aripiprazole, tadalafil, and ziprasidone are some of the most commonly prescribed medicines and highlight the tangible impact of these heterocycles on people and the treatment of their diseases.  Medicinal chemistry approaches to find small-molecule lead compounds with pharmacological activity continue to use natural products, synthesis, and existing small-molecule drug libraries as sources. The focus of this series of papers is on the use of indole and quinoline as therapeutics. Pharmaceuticals invites both reviews and original articles that concern the use of indoles and quinolines in the discovery and development of pharmaceuticals. The scope of this Special Issue will cover, but is not limited to, new synthetic methods in the synthesis of indoles and quinolines, medicinal chemistry and structure–activity studies on indole and quinoline derivatives, natural product discovery involving indoles and quinolines, indole and quinoline drug repositioning, new combinations of indoles and quinolines, and indoles and quinolines beyond pharmaceutical applications. The collection of manuscripts will be published as a Special Issue of the journal.

Dr. Florence McCarthy
Guest Editor

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Keywords

  • indole
  • quinoline
  • heterocycle
  • pharmaceutical discovery and development

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Published Papers (1 paper)

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Research

23 pages, 3814 KiB  
Article
Discovery of Sphingosine Kinase Inhibition by Modified Quinoline-5,8-Diones
by Ryan D. Kruschel, Kyle Malone, Alison N. Walsh, Christian Waeber and Florence O. McCarthy
Pharmaceuticals 2025, 18(2), 268; https://doi.org/10.3390/ph18020268 - 18 Feb 2025
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Abstract
Background: Sphingosine kinase (SphK) overexpression is observed in many cancers, including breast, renal and leukaemia, which leads to increased cellular proliferation, survival and growth. SphK inhibition has been an attractive target for anticancer drug development for the past decade, with SphK inhibitors such [...] Read more.
Background: Sphingosine kinase (SphK) overexpression is observed in many cancers, including breast, renal and leukaemia, which leads to increased cellular proliferation, survival and growth. SphK inhibition has been an attractive target for anticancer drug development for the past decade, with SphK inhibitors such as PF-543 and opaganib exhibiting clinical antitumour effects. By exploiting both CB5468139 and PF-543 as structural leads, we hereby report on the first quinoline-5,8-dione-based SphK inhibitor using a fragment-based approach. Methods: The quinoline-5,8-dione framework was developed to incorporate two defined regions, namely a polar quinoline core, which links to an aryl lipophilic chain. All synthetic molecules were characterized by NMR and HRMS and assayed against SphK 1 and 2, and molecular docking studies were performed. A subset of compounds was screened for anticancer activity. Results: As the binding site of SphK accommodates the lipophilic tail of sphingosine, we initially set out to explore the substitution of the C(7) aryl moiety to attain eight novel C(7) ether-linked quinoline-5,8-diones, which were screened for SphK1 and SphK2 activity with good potency identified. To improve SphK binding, structural fragments were adapted from PF-543 to participate in hydrogen bonding within the binding site of SphK1. A model study was performed to yield novel compounds through activated C(2) formyl intermediates. Two pyrrolidine-based quinoline-5,8-diones were assayed for SphK activity, with 21 revealing an improvement of SphK1 binding efficacy relative to the parent compound and 20 (and its precursor 4). Molecular modelling on the pyrrolidine quinoline-5,8-dione construct revealed favourable docking, low binding energies and opportunities for further improvement. Conclusions: Although the screening of anticancer activity was inconclusive, low micromolar dual SphK1/2 inhibition with the quinoline-5,8-dione framework has been identified for the first time, and a plausible new binding mode has been identified. Full article
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