PARP inhibitors are a type of drug used to treat certain cancers. In 2020, some PARP inhibitors were approved in the USA and the EU (although not in the UK) to treat prostate cancer which has spread outside the prostate and has stopped responding to hormone therapy drugs.
Some cancer cells have problems repairing their DNA. If the cell cannot fix its broken DNA, it will die. Certain cancers are reliant on a protein called PARP to fix the DNA breaks. PARP inhibitors stop PARP from working so the cancer cell cannot repair itself. Normal, healthy cells do not need PARP as much, so PARP inhibitors can target cancer cells specifically.
However, not all cancers need PARP to repair themselves when they are damaged. This means that not all cancers will be susceptible to PARP inhibitors. Some prostate cancers, however, do appear to rely on PARP, which is why PARP inhibitors have potential as a prostate cancer treatment.