Benzothiophene derivatives as selective estrogen receptor covalent antagonists: Design, synthesis and anti-ERα activities

Anticancer Potential of the S-Heterocyclic Ring Containing Drugs and its Bioactivation to Reactive Metabolites

Sulfur-containing heterocyclic derivatives have been disclosed for binding with a wide range of cancer-specific protein targets. Various interesting derivatives of sulfur-containing heterocyclics such as benzothiazole, thiazole, thiophene, thiazolidinedione, benzothiophene, and phenothiazine, etc have been shown to inhibit diverse signaling pathways implicated in cancer. Significant progress has also been made in molecular targeted therapy against specific enzymes such as kinase receptors due to potential binding interactions inside the ATP pocket. Sulfur-containing heterocyclic ring metal complexes i. e., benzothiazole, thiazole, thiophene, benzothiophene and phenothiazines are among the most promising active anticancer compounds. However, sulfur heteroaromatic rings, particularly thiophene, are of high structural alert due to their metabolism to reactive metabolites. The mere presence of a structural alert itself does not determine compound toxicity therefore, this review focuses on some specific findings that shed light on factors influencing the toxicity. In the current review, synthetic strategies of introducing the sulfur core ring in the synthesized derivatives are discussed with their structure-activity relationships to enhance our understanding of toxicity mechanisms and develop safer therapeutic options. The sulfur-containing marketed anticancer drugs included in this review direct the synthesis of novel compounds and will help in the development of potent, safer sulfur-based anticancer drugs in near future.

X-ray crystallography study and optimization of novel benzothiophene analogs as potent selective estrogen receptor covalent antagonists (SERCAs) with improved potency and safety profiles

Endocrine therapy (ET) is a well-validated strategy for estrogen receptor α positive (ERα + ) breast cancer therapy. Despite the clinical success of current standard of care (SoC), endocrine-resistance inevitably emerges and remains a significant medical challenge. Herein, we describe the structural optimization and evaluation of a new series of selective estrogen receptor covalent antagonists (SERCAs) based on benzothiophene scaffold. Among them, compounds 15b and 39d were identified as two highly potent covalent antagonists, which exhibits superior antiproliferation activity than positive controls against MCF-7 cells and shows high selectivity over ERα negative (ERα-) cells. More importantly, their mode of covalent engagement at Cys530 residue was accurately illustrated by a cocrystal structure of 15b-bound ERαY537S (PDB ID: 7WNV) and intact mass spectrometry, respectively. Further in vivo studies demonstrated potent antitumor activity in MCF-7 xenograft mouse model and an improved safety profile. Collectively, these compounds could be promising candidates for future development of the next generation SERCAs for endocrine-resistant ERα + breast cancer.

Introducing covalent warheads on spirocyclic sp2-sp3 fragments by innate C-H functionalization

Sp2-sp3 fragments play a vital role in fragment-based drug design (FBDD). Strategies to chemically modify them and efficiently access libraries of these compounds have been goals of the highest priority in the last decades. In this work, a series of sp2-sp3 fragments was synthesized and validated for that purpose, based on their measured physical-chemical properties. Selective C-H cyanation and allylation of these fragments was demonstrated by simple heating in presence of an appropriate hydrogen-atom transfer reagent and a radical acceptor. These conditions enabled a streamlined access to covalent fragments in a single step, by direct introduction of the desired covalent binder. Preliminary results on vinylation, as well as late-stage functionalization of a drug analogue were disclosed.

Optimization of small molecule degraders and antagonists for targeting estrogen receptor based on breast cancer: current status and future

The estrogen receptor (ER) is a classical receptor protein that plays a crucial role in mediating multiple signaling pathways in various target organs. It has been shown that ER-targeting therapies inhibit breast cancer cell proliferation, enhance neuronal protection, and promote osteoclast formation. Several drugs have been designed to specifically target ER in ER-positive (ER+) breast cancer, including selective estrogen receptor modulators (SERM) such as Tamoxifen. However, the emergence of drug resistance in ER+ breast cancer and the potential side effects on the endometrium which has high ER expression has posed significant challenges in clinical practice. Recently, novel ER-targeted drugs, namely, selective estrogen receptor degrader (SERD) and selective estrogen receptor covalent antagonist (SERCA) have shown promise in addressing these concerns. This paper provides a comprehensive review of the structural functions of ER and highlights recent advancements in SERD and SERCA-related small molecule drugs, especially focusing on their structural optimization strategies and future optimization directions. Additionally, the therapeutic potential and challenges of novel SERDs and SERCAs in breast cancer and other ER-related diseases have been discussed.

Design and development of intramolecular doubly vinylogous Michael addition to access 3-aryl substituted 2-alkenyl-benzofurans and -indoles

Herein, we have disclosed a rare example of an intramolecular doubly vinylogous Michael addition (DVMA). The reaction design exploits the innate reactivity of ortho-heteroatom substituted para-quinone methide (p-QM) derivatives. The sequential reaction of p-QMs and activated allyl halides proceeds through heteroatom-allylation, DVMA and oxidation to furnish a diverse range of 2-alkenyl benzofuran and 2-alkenyl indole derivatives in high yields.

In Silico Drug Design of Anti-Breast Cancer Agents

Cancer is a condition marked by abnormal cell proliferation that has the potential to invade or indicate other health issues. Human beings are affected by more than 100 different types of cancer. Some cancer promotes rapid cell proliferation, whereas others cause cells to divide and develop more slowly. Some cancers, such as leukemia, produce visible tumors, while others, such as breast cancer, do not. In this work, in silico investigations were carried out to investigate the binding mechanisms of four major analogs, which are marine sesquiterpene, sesquiterpene lactone, heteroaromatic chalcones, and benzothiophene against the target estrogen receptor-α for targeting breast cancer using Schrödinger suite 2021-4. The Glide module handled the molecular docking experiments, the QikProp module handled the ADMET screening, and the Prime MM-GB/SA module determined the binding energy of the ligands. The benzothiophene analog BT_ER_15f (G-score -15.922 Kcal/mol) showed the best binding activity against the target protein estrogen receptor-α when compared with the standard drug tamoxifen which has a docking score of -13.560 Kcal/mol. TRP383 (tryptophan) has the highest interaction time with the ligand, and hence it could act for a long time. Based on in silico investigations, the benzothiophene analog BT_ER_15f significantly binds with the active site of the target protein estrogen receptor-α. Similar to the outcomes of molecular docking, the target and ligand complex interaction motif established a high affinity of lead candidates in a dynamic system. This study shows that estrogen receptor-α targets inhibitors with better potential and low toxicity when compared to the existing market drugs, which can be made from a benzothiophene derivative. It may result in considerable activity and be applied to more research on breast cancer.

Discovery of Pyrido[1,2-a]pyrimidine Mesoionic Compounds Containing Benzo[b]thiophene Moiety as Potential Pesticide Candidates

The increasing evolution of insect resistance has made it challenging for traditional insecticides to control the bean aphid (Aphis craccivora Koch). To address this pending issue, a range of pyrido[1,2-a]pyrimidine mesoionic compounds containing benzo[b]thiophene were designed and synthesized. The biological activity test results of the target compounds indicated that they had moderate to outstanding insecticidal activity against the bean aphid (Aphis craccivora) and moderate insecticidal activity against the white-backed planthopper (Sogatella furcifera). Compound L14 exhibited significant insecticidal activity against A. craccivora, with an LC₅₀ value of 1.82 μg/mL, which was superior to triflumezopyrim (LC₅₀ = 4.76 μg/mL). The results of enzyme activity assay showed that compound L14 had a definite inhibitory effect on ATPase. Moreover, the proteomics and docking findings of compound L14 suggested that it may act on the central nervous system of aphids and interact with nicotinic acetylcholine receptors. Therefore, compound L14 is a potentially novel insecticide candidate for further utilization.