CX-5461 is a DNA G-quadruplex stabilizer with selective lethality in BRCA1/2 deficient tumours.

Hong Xu, Marco Di Antonio, Steven McKinney, Veena Mathew, Brandon Ho, Nigel J O'Neil, Nancy Dos Santos, Jennifer Silvester, Vivien Wei, Jessica Garcia, Farhia Kabeer, Daniel Lai, Priscilla Soriano, Judit BanĂ¡th, Derek S Chiu, Damian Yap, Daniel D Le, Frank B Ye, Anni Zhang, Kelsie Thu, John Soong, Shu-Chuan Lin, Angela Hsin Chin Tsai, Tomo Osako, Teresa Algara, Darren N Saunders, Jason Wong, Jian Xian, Marcel B Bally, James D Brenton, Grant W Brown, Sohrab P Shah, David Cescon, Tak W Mak, Carlos Caldas, Peter C Stirling, Phil Hieter, Shankar Balasubramanian, Samuel Aparicio, Nature communications 8, 14432 (2017) 2017
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Abstract

G-quadruplex DNAs form four-stranded helical structures and are proposed to play key roles in different cellular processes. Targeting G-quadruplex DNAs for cancer treatment is a very promising prospect. Here, we show that CX-5461 is a G-quadruplex stabilizer, with specific toxicity against BRCA deficiencies in cancer cells and polyclonal patient-derived xenograft models, including tumours resistant to PARP inhibition. Exposure to CX-5461, and its related drug CX-3543, blocks replication forks and induces ssDNA gaps or breaks. The BRCA and NHEJ pathways are required for the repair of CX-5461 and CX-3543-induced DNA damage and failure to do so leads to lethality. These data strengthen the concept of G4 targeting as a therapeutic approach, specifically for targeting HR and NHEJ deficient cancers and other tumours deficient for DNA damage repair. CX-5461 is now in advanced phase I clinical trial for patients with BRCA1/2 deficient tumours (Canadian trial, NCT02719977, opened May 2016).