OTX-015

OTX-015 is a potent inhibitor of BRD2, BRD3, and BRD4 with IC50 values range from 92 to 112 nM [1].
BRD2, BRD3, and BRD4 belong to BET bromodomain family and play an important role in regulating transcription. BRDs regulate several oncogenes transcription in a variety of cancers and thus have emerged as a promising target [2].
OTX-015 is a selective BRD2, BRD3, and BRD4 inhibitor and inhibits the binding of BRD2, BRD3, and BRD4 to AcH4. Using TR-FRET method and CHO cell lysate harboring BRD2, BRD3, and BRD4 to research the effect of OTX-015, result showed that OTX-015 inhibited BET family binding to AcH4 in a dose-dependent manner and the EC50 values range from 10 to 19 nM. When tested with human tumor cell lines, incubation with OTX-015 for 72 hours inhibited cell proliferation with GI 50 values ranged from 60 to 200 nM [1]. In ALKpos ALCL cell lines, treatment of OTX-015 for 24 h arrested cell proliferation in G1 phase which was more pronounced at 48 h and 72 h, and tested with SUPM2/TS and JB-6 cell lines OTX-015 showed ability to increase cell death rate [3].
In BLAB/c-nu/nu mice model with established Ty82 BRD-NUT midline carcinoma xenografts, oral administration of OTX-015 markedly inhibited tumor growth and reduced tumor volume [1].
References:
[1]. J. Kay Noel, Kazunori Iwata, Shinsuke Ooike, et al. Development of the BET bromodomain inhibitor OTX015 [J]. Mol Cancer Ther November 2013 12; C244.
[2]. Fu LL, Tian M, Li X, et al. Inhibition of BET bromodomains as a therapeutic strategy for cancer drug discovery [J]. Oncotarget. 2015 Mar 20;6(8):5501-5516.
[3]. Michela Boi, Maria Todaro, Valentina Vurchio, et al. OTX015, a bromodomain and extraterminal inhibitor, represents a novel agent for ALK positive anaplastic large cell lymphoma [J]. Mol Cancer Ther November 2013 12; A219.

Inhibition of BET bromodomain-dependent XIAP and FLIP expression sensitizes KRAS-mutated NSCLC to pro-apoptotic agents.[Pubmed:27607580]

Cell Death Dis. 2016 Sep 8;7(9):e2365.

Non-small cell lung cancer (NSCLC) has the highest incidence of cancer-related death worldwide and a high medical need for more effective therapies. Small-molecule inhibitors of the bromodomain and extra terminal domain (BET) family such as JQ1, I-BET762 and OTX-015 are active in a wide range of different cancer types, including lung cancer. Although their activity on oncogene expression such as c-Myc has been addressed in many studies, the effects of BET inhibition on the apoptotic pathway remain largely unknown. Here we evaluated the activity of BET bromodomain inhibitors on cell cycle distribution and on components of the apoptosis response. Using a panel of 12 KRAS-mutated NSCLC models, we found that cell lines responsive to BET inhibitors underwent apoptosis and reduced their S-phase population, concomitant with downregulation of c-Myc expression. Conversely, ectopic c-Myc overexpression rescued the anti-proliferative effect of JQ1. In the H1373 xenograft model, treatment with JQ1 significantly reduced tumor growth and downregulated the expression of c-Myc. The effects of BET inhibition on the expression of 370 genes involved in apoptosis were compared in sensitive and resistant cells and we found the expression of the two key apoptosis regulators FLIP and XIAP to be highly BET dependent. Consistent with this, combination treatment of JQ1 with the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or the pro-apoptotic chemotherapeutic agent cisplatin enhanced induction of apoptosis in both BET inhibitor sensitive and resistant cells. Further we showed that combination of JQ1 with cisplatin led to significantly improved anti-tumor efficacy in A549 tumor-bearing mice. Altogether, these results show that the identification of BET-dependent genes provides guidance for the choice of drug combinations in cancer treatment. They also demonstrate that BET inhibition primes NSCLC cells for induction of apoptosis and that a combination with pro-apoptotic compounds represents a valuable strategy to overcome treatment resistance.