Phenyl and Diaryl Ureas with Thiazolo[5,4-d]pyrimidine Scaffold as Angiogenesis Inhibitors: Design, Synthesis and Biological Evaluation

Discovery of VEGFR inhibitors through virtual screening and energy assessment

Vascular endothelial growth factor receptor-2 (VEGFR-2) is crucial in promoting tumor angiogenesis and cancer metastasis. Thus, inhibition of VEGFR-2 has appeared as a good tactic for cancer treatment. To find out novel VEGFR-2 inhibitors, first, the PDB structure of VEGFR-2, 6GQO, was selected based on atomic nonlocal environment assessment (ANOLEA) and PROCHECK assessment. 6GQO was then further used for structure-based virtual screening (SBVS) of different molecular databases, including US-FDA approved drugs, US-FDA withdrawn drugs, may bridge, MDPI, and Specs databases using Glide. Based on SBVS, receptor fit, drug-like filters, and absorption, distribution, metabolism, excretion, and toxicity (ADMET) analysis of 427877 compounds, the best 22 hits were selected. From the 22 hits, hit 5 complex with 6GQO was put through molecular mechanics/generalized born surface area (MM/GBSA) study and hERG binding. The MM/GBSA study revealed that hit 5 possesses lesser binding free energy with more inferior stability in the receptor pocket than the reference compound. The VEGFR-2 inhibition assay of hit 5 disclosed an IC₅₀ of 165.23 nM against VEGFR-2, which can be possibly enhanced through structural modifications.

Thiazolopyrimidine Scaffold as a Promising Nucleus for Developing Anticancer Drugs: a Review in Last Decade

The thiazolopyrimidine nucleus is a bioisostericanalog of purine and an important class of N-containing heterocycles. Thiazolopyrimidine scaffolds are considered a promising class of bioactive compounds that encompass diverse biological activities such as antibacterial, antiviral, antifungal, anticancer, corticotrophin-releasing factor antagonists, anti-inflammatory, antituberculosis, and glutamic receptors antagonists. Despite the importance of thiazolopyrimidines from a pharmacological viewpoint, there is hardly a comprehensive review on this important heterocyclic nucleus. Throughout the years, those scaffolds have been studied extensively for its anticancer properties and several compounds were designed, synthesized, and evaluated for their anticancer effects with activity in the µM to nM range. However, there are hardly any reviews covering the anticancer effects of thiazolopyrimidines. In this review, an effort was made to compile literatures covering the anticancer activity of thiazolopyrimidines reported in the last decade (2010-2020). Nearly thirty articles were reviewed and compounds which IC50 < 50 µM against at least 50% of the used cell lines were listed in this review. The best ten compounds (10a, 14b, 17g, 18,25e, 25k, 34e, 41i, 49a, & 49c) show the best anticancer activity against the corresponding cell lines during the last 10 years are highlighted. By highlighting the most active compounds, this review article sheds light on the structural features associated with the strongest anticancer effects to provide guidance to future research aiming to develop anticancer molecules.

Design and Synthesis of Novel Thiazolo[5,4-d]pyrimidine Derivatives as Potential Angiogenesis Inhibitors

Vascular endothelial growth factor receptor-2 (VEGFR-2) plays an important role in both vasculogenesis and angiogenesis. Inhibition of VEGFR-2 has been demonstrated as a key method against tumor-associated angiogenesis. Thiazolopyrimidine is an important analog of the purine ring, and we choose the thiazolopyrimidine scaffold as the mother nucleus. Two series of thiazolo[5,4-d]pyrimidine derivatives were synthesized and evaluated for their antiproliferative activity. In HUVEC inhibition assay, compounds 3l (=1-(5-{[2-(4-chlorophenyl)-5-methyl[1,3]thiazolo[5,4-d]pyrimidin-7-yl]amino}pyridin-2-yl)-3-(3,4-dimethylphenyl)urea) and 3m (=1-(5-{[2-(4-chlorophenyl)-5-methyl[1,3]thiazolo[5,4-d]pyrimidin-7-yl]amino}pyridin-2-yl)-3-(4-methoxyphenyl)urea) exhibited the most potent inhibitory effect (IC₅₀ =1.65 and 3.52 μm, respectively). Compound 3l also showed the best potency against VEGFR-2 at 50 μm (98.5 %). These results suggest that further investigation of compound 3l might provide potential angiogenesis inhibitors.