Current Topics in Medicinal Chemistry - Volume 23, Issue 12, 2023

Pyrazolo[1,5-a]pyrimidines are fused heterocycles that have spawned many biologically active antitumor drugs and are important privileged structures for drug development. Pyrazolo[1,5- a]pyrimidine derivatives have played an important role in the development of antitumor agents due to their structural diversity and good kinase inhibitory activity. In addition to their applications in traditional drug targets such as B-Raf, KDR, Lck, and Src kinase, some small molecule drugs with excellent activity against other kinases (Aurora, Trk, PI3K-γ, FLT-3, C-Met kinases, STING, TRPC) have emerged in recent years. Therefore, based on these antitumor drug targets, small molecule inhibitors containing pyrazolo[1,5-a]pyrimidine scaffold and their structure-activity relationships are summarized and discussed to provide more reference value for the application of this particular structure in antitumor drugs.

Background: β-ketoacyl-ACP synthase I (KasA I) enzyme is crucial in mycolic acid synthesis via catalytic condensation reactions, hence implicated in M. tuberculosis’s virulence and drug resistance. Presently, there is no known potent KasA inhibitor; thiolactomycin lacks potency. Recently reported indazole compounds JSF-3285/tr1DG167 and 5G/tr2DG167 inhibit the KasA through binding to the substrate cavity. However, the molecular mechanism is still unclear, and the unknown resistance mechanisms raise concerns about JSF-3285's novelty. Methods: This study is the first to report the flap dimer opening and closing of the KasA pocket using combined metrics to define the symmetry impact of the flap-dimer motions and investigate the underlying inhibitory mechanism of tr1DG167 andtr2DG167 using all-atom MD simulation. Results: The distance/d1 between the flap (PRO147) and dimer (LEU205) residues; TriC-α angle (θ1: PRO147-VAL83-LEU205 & θ2: PRO147-GLU199-LEU205); and the dihedral angle (Φ) were applied to investigate the flap “twisting” and dimer shift closing due to concerted motion by adjacent glycine-rich and glutamic acid-rich loops around the active site during the binding pocket’s opening. The full flap-dimer of the unbound opens at 230 ns (d1 = 21.51 Å), corresponding to the largest TriC-α angle θ1 44.5° as θ2 is unreliable to describe the flap-dimer motion. The overall averages θ1 and θ2 for the bounds were ~23.13° and ~23.31°, respectively. Thus, the degree of KasA flap dimer opening is best investigated by distance and θ1. BFE (Kcal/mol) of -44.05 (tr1DG167) showed a higher affinity for the pocket than tr2DG167-KasA (-32.16). Both tr1DG167 and tr2DG167 formed hydrophobic interactions with LEU116, GLY117, ALA119, and tr1DG167 formed strong H-bonds with GLU199. The average RMSD of 2.80 Å (Apo) and RoG of 20.97 Å showed that KasA is less stable and less tightly packed without the inhibitors. Conclusion: These findings provide a background for a new structure-based design of novel KasA inhibitors.

Background: Arylindole derivatives are promising scaffolds in the design of new drugs. These scaffolds exhibit a wide biological activity, including inhibition of COX-2, antitumor activity, receptor GABA agonism, and estrogen receptor modulation. Objectives: Taking this into account, this paper presents a study to understand the inhibitory action of certain 2-arylindole derivatives, specifically a series of 2,3-diarylindoles with IC50 values from 0.006 nM to 100 nM, on the COX-2 enzyme and supports its structural-activity relationship (SAR) through molecular docking simulations. Methods: Applying molecular modelling, especially molecular docking, we assessed the SAR of a series of 2,3-arylindoles derivatives in the COX-2 enzyme. Results: The results indicated that Gly 526 and Phe 381 residues are relevant for improving inhibitory activity on para-substituted 3-phenyl- compounds. Arg 120 was also demonstrated to be an important residue for COX-2 inhibition since it enables a π-cation interaction with the best compound in series A5 (experimental IC50 = 0.006 nM determined in advance). Furthermore, COX-2 presents flexibility in some regions of the active site to adequately accommodate 5-substituted compounds containing an indole ring. Conclusion: Therefore, such structural features can be used as support for further Structural-Based Drug Design (SBDD) and/or Ligand-Based Drug Design (LBDD) studies on new selective COX-2 inhibitors.

It is now an undisputed fact that cancer cells undergo metabolic reprogramming to support their malignant phenotype, and it is one of the crucial hallmarks which enables cancer cells to facilitate their survival under variable conditions ranging from lack of nutrients to conditions, such as hypoxia. Recent developments in technologies, such as lipidomics and machine learning, have underlined the critical effects of altered lipid metabolism in tumorigenesis. The cancer cells show elevated de novo fatty acid synthesis, an increased capacity to scavenge lipids from their environment, and enhanced fatty acid oxidation to fulfill their need for uncontrolled cellular proliferation, immune evasion, tumor formation, angiogenesis, metastasis, and invasion. Besides, important genes/ proteins involved in lipid metabolism have been proposed as prognostic indicators in a variety of cancer types linked to tumor survival and/or recurrence. Consequently, several approaches are being explored to regulate this metabolic dysregulation to subvert its tumorigenic properties in different types of cancers. The present review details the significance of lipid metabolism in cancer progression, the critical enzymes involved therein, and their regulation. Moreover, the current findings of the interplay between the oncogenic pathways and the lipid metabolic enzymes are elucidated briefly. The therapeutic implications of modulating these aberrations for the advancement of anti-cancer therapies are also discussed. Although the understanding of altered lipid metabolism in cancer initiation and progression is still in its infancy and somewhat obscure, its in-depth comprehension will open promising therapeutic opportunities for the development of novel and promising strategies for cancer treatment and management.

Tumor-associated macrophages (TAMs) play a pivotal role in the progression and resistance of tumors to different anticancer drugs. TAMs can modulate the tumor microenvironment (TME) in favor of immune system exhaustion. The interactions of TAMs with TME can affect the function of cytotoxic CD8+ T lymphocytes (CTLs) and natural killer (NK) cells. Furthermore, TAMs can induce cancer cell proliferation by releasing some growth factors, such as transforming growth factor (TGF)-β. TAMs have several positive cross-talks with other immune suppressive cells such as regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs), cancerassociated fibroblasts (CAFs), and cancer cells, leading to the release of growth factors, the proliferation of cancer cells and tumor growth. These interactions also can induce invasion and migration of cancer cells, angiogenesis, and metastasis. The inhibition of TAMs is an intriguing strategy for overcoming tumor resistance and suppression of cancer cells. Some natural-derived agents such as melatonin, curcumin, resveratrol, apigenin, and other flavonoids have shown the ability to modulate TME, including TAMs. These adjuvants may be able to boost antitumor immunity through the modulation of TAMs. This review explains the modulatory effects of some well-known naturally derived agents on the activity of TAMs. The modulation of TAMs by these agents may be useful in suppressing tumor growth and invasion.

Cancer is a disease in which repeated rounds of mutations cause uncontrolled growth of cells, which prospers at the expense of their neighbor cells and then eventually leads to the destruction of the whole cellular community. Chemopreventive drugs either prevent DNA damage, which results in malignancy, or they stop or reverse the division of premalignant cells with DNA damage, which inhibits the growth of cancer. There is an obvious need for an alternate strategy given the ongoing rise in cancer incidence, the ineffectiveness of traditional chemotherapies to control cancer, and the excessive toxicity of chemotherapies. From antiquity to date, the saga of the usage of plants as medicine has been the mainstay among people worldwide. In recent years, extensive studies have been conducted on medicinal plants, spices, and nutraceuticals, as these have gained much popularity in reducing the risk of several cancer types in humans. Extensive studies on cell culture systems and animal models have demonstrated that various medicinal plants and nutraceuticals from various natural resources and their products, such as major polyphenolic constituents, flavones, flavonoids, antioxidants, etc, provide considerable protection against many cancer types. As shown in the literatures, the major aim of studies conducted is to develop preventive/therapeutic agents which can induce apoptosis in cancer cells without affecting normal cells. Projects are going on worldwide to find better ways to eradicate the disease. The study of phytomedicines has shed new light on this topic as research to date has proven that they have antiproliferative and apoptotic capabilities that will aid in the development of novel cancer prevention options. Dietary substances, such as Baicalein, Fisetin, and Biochanin A have shown that they have an inhibitory effect on cancer cells, suggesting that they may work as chemopreventive agents. This review discusses the chemopreventive and anticancer mechanisms of such reported natural compounds.

The radiolabeled tracers have been extensively utilized to access various physiological and pathological conditions non-invasively, such as cancers, inflammation, and organ-specific imaging. These tracers demonstrate and study tumor hypoxia in several malignancies. Hypoxia is commonly seen in solid tumors. Tumor Hypoxia is a non-physiological condition of reduced oxygen concentration in the tumor. Hypoxia is associated with adverse outcomes such as treatment resistance and metastases in solid tumors. Tumor hypoxia may result in resistance to radiation therapy and chemotherapy, leading to a poor prognosis. It is one of the clinically paramount factors in treatment planning. Various chemical scaffolds are labeled with compatible radioisotopes for imaging hypoxia by Single-photon emission computed tomography (SPECT) and Positron emission tomography (PET). Radionuclides, such as [¹⁸F]Flourine, [^99mTc]Technetium, [¹³¹I]Iodine, [¹²⁴I] Iodine, and [⁶⁴Cu]Copper are used for incorporation into different chemical scaffolds.Among them, [¹⁸F]Flourine and [⁶⁴Cu]Copper tagged radiopharmaceuticals are most explored, such as [¹⁸F]FMISO, [¹⁸F]FAZA, [¹⁸F]FETNIM, and N4-methyl thiosemicarbazone [⁶⁴Cu][Cu (ATSM)]. Some of the promising scaffolds for imaging hypoxia are [¹⁸F]EF1, [¹⁸F]EF5, [¹⁸F]EF3, and [¹⁸F]HX4. This review is focused on developing radiochemistry routes to synthesize different radiopharmaceuticals for imaging hypoxia in clinical and preclinical studies, as described in the literature. The chemist and radiochemist exerted enormous efforts to overcome these obstacles. They have successfully formulated multiple radiopharmaceuticals for hypoxia imaging. Radionuclide incorporation in high selectivity and efficiency (radiochemical yield, specific activity, purity, and radio-scalability) is a need for application perspective. Versatile chemistry, including nucleophilic and electrophilic substitutions, allows the direct or indirect introduction of radioisotopes into molecules of interest. This review will discuss the chemical routes for synthesizing and utilizing different precursors for radiolabeling with radionuclides.We will briefly summaries these radio-labeled tracers' application and biological significance.