RE: Sierra7 Nov 2019 22:57
From the Article:-
“If synthetic lethality is a kind of one-two punch, the trick in fighting cancer is landing the right second punch. The only precedent is a type of drug called PARP inhibitors, such as Clovis Pharma’s rucapirib (Rubraca). PARP inhibitors knock out an enzyme, poly (ADP-ribose) polymerase, that cancer cells use to bounce back from treatment. In cells that are also missing the tumor suppressor genes BRCA1 and BRCA2, the PARP knockout takes down the entire cell. But not all the time, warns Tango CEO Weber: “It’s all context dependent,” she says, noting that PARP inhibitors have worked better to date in BRCA1 or BRCA2-mutated ovarian cancer than in breast cancer.
PARP inhibitors can stop working, too. Writing in Science in 2017, Christopher Lord of the Institute of Cancer Research in London and Alan Ashworth of the University of California, San Francisco, noted, “As with other targeted therapies, resistance to PARP [inhibition] arises in advanced disease.” In the 1990s, Ashworth helped make the connection between BRCA mutations and PARP inhibition, sparking the use of synthetic lethality to fight cancer. He is a Tango cofounder.”
So PARP resistance is the problem:-
“Furthermore, in cells with restored fork protection, cells depend on RAD51 recruitment to the fork for proper protection. Importantly, both PALB2–BRCA2 recruitment to DNA breaks, and RAD51 recruitment to stalled forks, are ATR-dependent in these PARPi-resistant cells [99]. Combining PARPi with ATR inhibitors therefore holds great promise to overcome PARPi resistance in tumors with restored HR or restored fork protection. Inhibitors of ATM (ATMi) seem to hold the same promise because cells with combined disruption of BRCA1 and TP53BP1 or REV7 are resensitized to PARPi by ATMi
99 = In tumor cells derived from patients, ATR is also overcome the bypass of BRCA1/2 in fork protection. Thus, ATR inhibition is a unique strategy to overcome the PARPi resistance of BRCA-deficient cancers.
So research ATR pathways and what’s inline downstream = CHK1
https://imgur.com/a/HZzU9Ua
But there’s a limited about of ATR/ATM/CHK1 inhibitors, AstraZeneca has the lead on ATR inhibitors and I think only 1 in the running but it dosnt synergies with chemo very good but SRA737 does!
Add in a bit of PD-L1 immunotherapy:-
From checkpoint to checkpoint: DNA damage ATR/Chk1 checkpoint signalling elicits PD-L1 immune checkpoint activation
https://www.nature.com/articles/s41416-018-0017-x