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A series of eleven 4-substituted 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidines were designed and synthesized and their biological activities were evaluated. Synthesis involved the Gewald reaction to synthesize ethyl 2-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate ring, and SNAr reactions. Compound 4 was 1.6- and ~7-fold more potent than the lead compound 1 in cell proliferation and microtubule depolymerization assays, respectively. Compounds 4, 5 and 7 showed the most potent antiproliferative effects (IC50 values < 40 nM), while compounds 6, 8, 10, 12 and 13 had lower antiproliferative potencies (IC50 values of 53–125 nM). Additionally, compounds 4–8, 10 and 12–13 circumvented Pgp and βIII-tubulin mediated drug resistance, mechanisms that diminish the clinical efficacy of paclitaxel (PTX). In the NCI-60 cell line panel, compound 4 exhibited an average GI50 of ~10 nM in the 40 most sensitive cell lines. Compound 4 demonstrated statistically significant antitumor effects in a murine MDA-MB-435 xenograft model.

: Thieno[3,2-d]pyrimidine ring framework comprises a significant class of heterocyclics that serve as a promising platform showing different pharmacological activities. The interest in thieno[3,2-d]pyrimidine cores for pharmaceutical products makes this scaffold an exceptionally helpful building block for organic chemistry. This review presents current research on thieno[3,2-d]pyrimidines and elucidates their biological importance in anti-cancer, anti-infectious, anti-convulsant, anti-diabetic, CNS, and osteoporosis drug discoveries. Patents on the thieno[3,2-d]pyrimidines are also elaborated as a piece of useful information. Here we additionally focus on the synthesis of this vital ring and the discovery of new thieno[3,2-d]pyrimidines.

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Microtubules are cytoskeleton protein polymers composed of αß-tubulin heterodimers which play pivotal roles in cell division, cellular transport and cell signaling. Interfering with microtubule dynamics is a well-established strategy for the treatment of cancer. However, clinical utility of microtubule targeting agents (MTAs) in cancer chemotherapy is often limited by the emergence of drug resistance. Expression of P-glycoprotein (Pgp) or the βIII isotype of tubulin, are two clinically established drug resistance mechanisms. We previously reported that compound AG346 binds to the colchicine site of tubulin and has microtubule depolymerization activity in A-10 cells (EC50 = 365 nM). Molecular modeling and docking studies of this compound in the X-ray crystal structure of tubulin (PDB: 402B) suggested that the pyrrole NH can be substituted with alkyl chains of optimal length to obtain an altered binding conformation which can facilitate interaction with the hydrophobic pocket formed by amino acid Val181 of side chain A, and Lys352 and Thr314 of side chain B. We designed and synthesized a variety of pyrrole NH-alkyl substituted compounds and determined that the compound AG473 shows a 43-fold improved microtubule depolymerization potency (EC50 = 8.4 nM) in A-10 cells, compared to the lead compound. In addition, this compound inhibited the growth of human melanoma cancer cell line MDA-MB-435 in culture with an IC50 of 7.2 nM, which is a 5-fold improvement in potency over the parent compound. These analogs also circumvented resistance mediated by Pgp and βIII-tubulin. These attributes provide the impetus for further preclinical development of these compounds as microtubule targeted antitumor agents in vivo and these studies are currently underway. Citation Format: Aleem Gangjee, Tasdique M. Quadery, Susan L. Mooberry. Structure-activity relationship study of pyrrolo[2,3- d]pyrimidines as microtubule targeting antitumor agents [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5105. doi:10.1158/1538-7445.AM2017-5105

Microtubules, attractive targets for drug development as anticancer agents, play vital roles in multiple aspects of cellular metabolism. These agents have been successfully used in the clinic for the treatment of various cancers. However, the utility of such agents are often limited by the emergence of tumor resistance due to overexpression of P-glycoprotein and/or âIII-tubulin. Tumor angiogenic mechanisms are important for tumor growth and metastasis are inhibited by antiangiogenic agents (AAs). AAs are usually cytostatic, and their utility in cancer chemotherapy lies in their combination with cytotoxic chemotherapeutic agents. Clinical combinations of antiangiogenic agents with antitubulin agents have been particularly successful. Recently, we reported water-soluble tubulin targeting pyrrolo[2,3-d]- and pyrrolo[3,2-d]pyrimidine analogs as antitumor agents, that circumvent drug resistance. These analogs also possess RTK (EGFR, VEGFR2 and PDGFRâ) inhibitory activity. To further explore the activity of these dual RTK/tubulin inhibitors we designed isosteric thieno[2,3-d] pyrimidine and thieno[3,2-d]pyrimidine analogs which increased microtubule depolymerizing potency by 14 to 24-fold (AG95 IC50 = 7.0 ± 2.7 nM, AG370 IC50 = 7.6 ± 2.1 nM) compared with the lead compounds (AG85 IC50 = 96.6 ± 5.3 nM, AG20 IC50 = 183 ± 3.4 nM). Substitution at the 4-anilino position of both these scaffolds were also explored with various moieties to afford the 6-methoxy-tetrahydroquinoline moiety which possess the optimum balance of microtubule depolymerizing activity (AG372 IC50 = 4.3 ± 1.6 nM, AG337 IC50 = 3.4 ± 0.9 nM,) and RTK (EGFR, VEGFR2 and PDGFRâ) inhibitory activity. These two compounds demonstrated excellent inhibition for EGFR (IC50 = 12.6 ± 1.2 nM, 28.5 ± 3.9 nM), VEGFR-2 (25.2 ± 7.2 nM, 216.1 ± 18.6 nM) and PDGFRâ (IC50 = 25.6 ± 7.2 nM, 266.8 ± 35.4 nM) comparable to the standard clinically used agents. These attributes of the 4-N-substituted thieno pyrimidines provides the impetus for further development of these compounds as dual acting targeted antitumor agents. Citation Format: Aleem Gangjee, Farhana Islam, Tasdique Mohammad Quadery, Susan L. Mooberry, Anja Bastian, Michael A. Ihnat. Design, synthesis, and biological evaluation of thieno[2,3-d] and thieno[3,2-d]pyrimidines as dual acting RTK inhibitors and microtubule targeting antitumor agents. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4837.