Design, synthesis and biological evaluation of 3,5-dimethylisoxazole and pyridone derivatives as BRD4 inhibitors

Bromodomain inhibitors and therapeutic applications

The bromodomain acts to recognize acetylated lysine in histones and transcription proteins and plays a fundamental role in chromatin-based cellular processes including gene transcription and chromatin remodeling. Many bromodomain proteins, particularly the bromodomain and extra terminal domain (BET) protein BRD4 have been implicated in cancers and inflammatory disorders and recognized as attractive drug targets. Although clinical studies of many BET bromodomain inhibitors have made substantial progress toward harnessing the therapeutic potential of targeting the bromodomain proteins, the development of this new class of epigenetic drugs is met with challenges, especially on-target dose-limiting toxicity. In this review, we highlight the current development of new-generation small molecule inhibitors for the BET and non-BET bromodomain proteins and discuss the research strategies used to target different bromodomain proteins for a wide array of human diseases including cancers and inflammatory disorders.

Tyrosol Derivatives, Bearing 3,5-Disubstituted Isoxazole and 1,4-Disubstituted Triazole, as Potential Antileukemia Agents by Promoting Apoptosis

In the present study, we assess tyrosol derivatives bearing 3,5-disubstituted isoxazoles and 1,4-disubstituted triazoles for their ability to inhibit the proliferation of K562 cells derived from leukemia as well as primary chronic myeloid leukemia (CML) cells obtained from the peripheral blood of 15 CML patients including 10 patients with untreated chronic phase and 5 patients with resistance against imatinib or multiple TKI. Our results showed that most derivatives displayed significant anti-proliferative activity against K562 cells in a dose-dependent manner. Among them, compounds 3d and 4a exhibited greater potent anticancer activity with respective IC₅₀ values of 16 and 18 µg/mL (45 µM and 61 µM). Interestingly, compound 3d inhibited CML cell proliferation not only in newly diagnosed but also in imatinib-resistant patients. We demonstrated that the anti-proliferative effect of this compound is mediated by a pro-apoptotic activity by promoting oxidative stress and modulating the activity of the Akt, p38 MAPK and Erk 1/2 pathways. In conclusion, our data highlight the potential of this class of derivative as a novel promising therapeutic agent for CML therapy.

Design, synthesis, and evaluation of novel pyridone derivatives as potent BRD4 inhibitors for the potential treatment of prostate cancer

Since androgen receptor (AR) can bind to BRD4 protein and this binding can be blocked by BRD4 inhibitors, targeting BRD4 has emerged as a promising approach for the treatment of prostate cancer (PC). Herein, we designed and synthesized a series of 5-(1-benzyl-1H-indazol-6-yl)-4-ethoxy-1-methylpyridin-2(1H)-one derivatives as novel BRD4 inhibitors for prostate cancer. Among them, compound 13 displayed the most robust BRD4 inhibitory activity with an IC₅₀ value of 18 nM. Furthermore, 13 showed potent anti-proliferative activity against enzalutamide-resistant 22RV1 cells. The mechanism of action studies demonstrated that 13 induced cell apoptosis by regulating Bcl-2/Bax proteins and activating caspase-3 signaling pathway. In addition, the c-Myc level was significantly reduced in 22RV1 cells on the western blot assay. These findings collectively suggested that compound 13 might find potential use for the treatment of prostate cancer.