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Small-Molecule Targeted Drugs

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Medicinal Chemistry".

Deadline for manuscript submissions: 30 June 2026 | Viewed by 3616

Special Issue Editors


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Guest Editor
Laboratory of Chemical Biology and Molecular Drug Design, College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou 310014, China
Interests: medicinal chemical biology; molecular drug design; anti-tumor immunosuppressants; PD-1/PD-L1 small-molecule drugs
Special Issues, Collections and Topics in MDPI journals

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Guest Editor Assistant
Laboratory of Chemical Biology and Molecular Drug Design, College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou 310014, China
Interests: small molecule compunds

Special Issue Information

Dear Colleagues,

The discovery and development of small-molecule drugs involve a combination of biological insights, chemical syntheses, and computational modeling. Each step, from screening to drug design, is crucial in developing effective and safe medications. This Special Issue focuses on the cutting-edge methodologies and strategies used in identifying and optimizing small molecular compounds for therapeutic use, in particulr, in the discovery of small-molecule inhibitors of PD-1/PD-L1. This area of research is critical in the pharmaceutical industry as small molecules make up the majority of drugs available on the market.

This Special Issue covers various screening techniques such as high-throughput screening (HTS), structure-based drug design (SBDD), and ligand-based drug design (LBDD), which are used to rapidly evaluate vast libraries of compounds for potential biological activities. Additionally, it delves into computational approaches, including molecular docking and pharmacophore modeling, which are instrumental in predicting how small molecules interact with their biological targets, thereby accelerating the drug design process. Advances in these technologies have significantly reduced the time and cost associated with drug development while increasing the efficiency and success rate of discovering new therapeutics. This Special Issue also highlights case studies where these techniques have been successfully applied to develop drugs for various diseases, demonstrating their impact on modern medicine.

We look forward to your submission.

Prof. Dr. Wen Zhang
Guest Editor

Dr. Annoor Awadasseid
Guest Editor Assistant

Manuscript Submission Information

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Keywords

  • drug discovery
  • high-throughput screening
  • structure (ligand)-based drug design
  • PD-1/PD-L1 drug design
  • molecular docking
  • pharmacophore modeling
  • therapeutics
  • computational approaches

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Published Papers (3 papers)

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Research

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26 pages, 10645 KB  
Article
Classical Paal-Knorr Cyclization for Synthesis of Pyrrole-Based Aryl Hydrazones and In Vitro/In Vivo Evaluation on Pharmacological Models of Parkinson’s Disease
by Maya Georgieva, Martin Sharkov, Emilio Mateev, Diana Tzankova, Georgi Popov, Vasil Manov, Alexander Zlatkov, Rumyana Simeonova and Magdalena Kondeva-Burdina
Molecules 2025, 30(15), 3154; https://doi.org/10.3390/molecules30153154 - 28 Jul 2025
Cited by 3 | Viewed by 1749
Abstract
Some studies performed in our laboratory on pyrrole and its derivatives pointed towards the enrichment of the evaluations of these promising chemical structures for the potential treatment of neurodegenerative conditions in general and Parkinson’s disease in particular. A classical Paal-Knorr cyclization approach is [...] Read more.
Some studies performed in our laboratory on pyrrole and its derivatives pointed towards the enrichment of the evaluations of these promising chemical structures for the potential treatment of neurodegenerative conditions in general and Parkinson’s disease in particular. A classical Paal-Knorr cyclization approach is applied to synthesize the basic hydrazine used for the formation of the designed series of hydrazones (15a15g). The potential neurotoxic and neuroprotective effects of the newly synthesized derivatives were investigated in vitro using different models of induced oxidative stress at three subcellular levels (rat brain synaptosomes, mitochondria, and microsomes). The results identified as the least neurotoxic molecules, 15a, 15d, and 15f applied at a concentration of 100 µM to the isolated fractions. In addition, the highest statistically significant neuroprotection was observed for 15a and 15d at a concentration of 100 µM using three different injury models on subcellular fractions, including 6-hydroxydopamine in rat brain synaptosomes, tert-butyl hydroperoxide in brain mitochondria, and non-enzyme-induced lipid peroxidation in brain microsomes. The hMAOA/MAOB inhibitory activity of the new compounds was studied at a concentration of 1 µM. The lack of a statistically significant hMAOA inhibitory effect was observed for all tested compounds, except for 15f, which showed 40% inhibitory activity. The most prominent statistically significant hMAOB inhibitory effect was determined for 15a, 15d, and 15f, comparable to that of selegiline. The corresponding selectivity index defined 15f as a non-selective MAO inhibitor and all other new hydrazones as selective hMAOB inhibitors, with 15d indicating the highest selectivity index of >471. The most active and least toxic representative (15d) was evaluated in vivo on Rotenone based model of Parkinson’s disease. The results revealed no microscopically visible alterations in the ganglion and glial cells in the animals treated with rotenone in combination with 15d. Full article
(This article belongs to the Special Issue Small-Molecule Targeted Drugs)
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Review

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21 pages, 1084 KB  
Review
Review of Structural Modification and Development of Novel Tramadol Derivatives
by Ni Wang, Xiaoli Zhou, Jingwen Wang, Lixin Sun, Bo Liu and Lihui Yin
Molecules 2026, 31(7), 1177; https://doi.org/10.3390/molecules31071177 - 2 Apr 2026
Viewed by 538
Abstract
Tramadol acts via μ-opioid receptor agonism and monoamine reuptake inhibition but is clinically limited by metabolic dependence, interindividual variability, and addiction risks. Structural modification aims to resolve these limitations. This review systematically summarizes tramadol’s structure–activity relationships and mechanisms, focusing on key strategies for [...] Read more.
Tramadol acts via μ-opioid receptor agonism and monoamine reuptake inhibition but is clinically limited by metabolic dependence, interindividual variability, and addiction risks. Structural modification aims to resolve these limitations. This review systematically summarizes tramadol’s structure–activity relationships and mechanisms, focusing on key strategies for structural optimization. Major advances include: (i) synergistic strategies, such as tramadol–celecoxib cocrystals (tramadol and celecoxib coexist in the supramolecular crystal network at a 1:1 molar ratio), achieving multimodal analgesia at lower doses; (ii) mechanism-balancing strategies such as tapentadol (derivatives of tramadol with a dual mechanism of action), which enhance μ-opioid agonism and norepinephrine reuptake inhibition while attenuating serotonergic effects to improve efficacy; (iii) metabolic optimization utilizing M1 analogues to circumvent CYP2D6 polymorphisms (tramadol is metabolized by this enzyme into the active metabolite M1 to exert analgesic effects); and (iv) pharmacophore optimization leveraging tramadol–morphine homology and “message–address” concepts to design selective ligands. Novel derivatives demonstrate improved potency and metabolic stability but continue to face challenges regarding opioid risks and clinical translation. Future research should integrate rational drug design, delivery systems, and personalized medicine to facilitate the development of safer next-generation analgesics. Full article
(This article belongs to the Special Issue Small-Molecule Targeted Drugs)
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23 pages, 1333 KB  
Review
Targeting the UPR with Small Molecules: Emerging Strategies for Immune Regulation
by Junyi Duan, Daoyuan Huang and Yick W. Fong
Molecules 2026, 31(3), 559; https://doi.org/10.3390/molecules31030559 - 5 Feb 2026
Viewed by 781
Abstract
The unfolded protein response (UPR) is a highly conserved adaptive mechanism that restores endoplasmic reticulum (ER) homeostasis under stress. Beyond its canonical roles in proteostasis, the UPR has emerged as a central regulator of immune responses across diverse contexts, including infection, inflammation, cancer, [...] Read more.
The unfolded protein response (UPR) is a highly conserved adaptive mechanism that restores endoplasmic reticulum (ER) homeostasis under stress. Beyond its canonical roles in proteostasis, the UPR has emerged as a central regulator of immune responses across diverse contexts, including infection, inflammation, cancer, and autoimmunity. IRE1α, PERK, and ATF6 are three principal UPR sensors that coordinate complex signaling networks to regulate antigen presentation, cytokine production, and immune cell differentiation. This review highlights the molecular mechanisms by which small molecules target the UPR to modulate immune responses. In addition, we highlight stress granules (SGs) and the prevalence of protein–protein interactions mediated by intrinsically low-complexity domains (LCDs) in the UPR as potential new avenues for immune modulation. Finally, we discuss future directions for leveraging UPR modulation in immunotherapy, infectious disease, and chronic inflammatory disorders. Full article
(This article belongs to the Special Issue Small-Molecule Targeted Drugs)
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