Abstract 2458: Discovery and development of novel 4-aminopyrimidines (A9 analogs) as potential BRCA1-mimetic drugs for the treatment of breast cancer.

Introduction The breast cancer type-1 susceptibility protein (BRCA1) is encoded by the BRCA-1 gene, and mutations on this gene, or defects on its transcription have been associated with high risks of breast, ovarian, fallopian tube and prostate cancer. The major role of BRCA1 protein is as a tumor suppressor agent, which works mainly by repairing DNA double-strand breaks. We have extensively studied the interactions of BRCA1 protein with the estrogen receptor (ER-1), and observed that it strongly inhibits ER-1 activity in cancer cells and blocks estrogen (E2)-stimulated gene expression and cell proliferation. We have built a high resolution three-dimensional computational model of the protein complex BRCA1:ER-1, and used it to virtually screen libraries of small molecules capable of acting as BRCA1-mimetics. From a focused library, we identified the compound 2,6-dibenzyl-5-phenylpyrimidin-4-amine (A9) as a potent inhibitor of the ER-1 activity (IC50 9 uM). Herein, we will report the synthesis and development of a series of A9-analogs with improved activity. Methods The description of the three-dimensional molecular modeling of the protein complex BRCA1:ER-1 used to identify A9, and the functional assay utilized for determination of the E2-dependent transcriptional activity have been reported (Ma, Y. et al. Oncogene, 2005, 24, 1831-1846). Three distinct series of A9 analogs have been planned, namely the symmetric, asymmetric and restrict analogs. The symmetric compounds were synthesized via base-catalyzed trimerization of aromatic-substituted benzylnitriles using microwave at 165 degrees Celsius, in three cycles of 15 min. After the reaction, the crude reaction mixture was purified via flash chromatography (Biotage) to give the corresponding final 4-aminopyrimidines in yields ranging from 7-23%. The A9 analogs were dissolved in DMSO and tested for in vitro E2-stimulated ERE-luciferase activity. An IC50 was calculated from graph interpolation and expressed in micromolar units. Results Data for six initial A9 analogs are reported herein. Their IC50 values and yields of synthesis are as following: A9, 4-H (IC50= 9 uM); EDO-1-119, 4-NH2 (IC50= 1.3 uM, yield 7.4%); EDO-1-123, 4-Cl (IC50> 20 uM, yield 16.4%); EDO-1-124, 4-CH3 (IC50= 1.3 uM, yield 12.5%); EDO-1-127, 4-Br (IC50= 1.5 uM, yield 20.3%); EDO-1-112, 4-(3-pyridinyl) (IC50= 2.5 uM, yield 23%); EDO-1-116, 4-(β-naphtyl) (IC50= 5 uM, yield 20%). All compounds were fully characterized by 1H-NMR and 13C-NMR, and elemental analysis. Conclusion We have identified several new analogs with increased BRCA1-mimetic activity as compared to A9. Initial structure-activity relationship (SAR) studies suggest that the 4-position at the aromatic ring in A9 can well tolerate a wide range of substituents including larger aromatic rings. Synthetic efforts resulted in a 7-fold increase in mimetic activity. Citation Format: Eliseu O. De Oliveira, Yongxian Ma, York Tomita, Eliot Rosen, Milton L. Brown. Discovery and development of novel 4-aminopyrimidines (A9 analogs) as potential BRCA1-mimetic drugs for the treatment of breast cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2458. doi:10.1158/1538-7445.AM2013-2458 Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.