A parp or PARP inhibitor is an antineoplastic drug that works by interfering with the DNA repair process in cancerous cells. Drugs in this class can be used alone or with other chemotherapy agents. As of 2011, parp inhibitors were primarily investigational drugs, with researchers studying their potential applications in laboratory and clinical trial environments. This drug class has considerable appeal to cancer researchers and doctors, as it can attack cancers without damaging neighboring cells in the body.
Poly(ADP-ribose) polymerase (PARP) is an enzyme involved in the process of DNA repair. Every time cells multiply and divide, there is a risk of DNA damage, addressed with built-in repair systems. Certain types of tumors rely heavily on the parp enzyme to repair themselves. These tumors can be vulnerable to targeting with agents designed to lock onto the enzyme. A parp inhibitor interferes with this process, killing the cancer cells by making it impossible to repair their DNA. The dead cells cannot replicate and the tumor will stop growing and eventually start shrinking as cells die off.
When used alone, a parp inhibitor can attack a cancer without damaging cells near the cancer, as it does not target healthy cells, only cancer cells relying on parp for DNA repair. It can also be used with another chemotherapeutic agent, mopping up after the other drug to kill cancer cells the first drug is unable to reach. Combination therapy can be highly effective in cancer treatment by attacking a cancer from multiple angles.
A parp inhibitor is not effective on all types of cancers. Cancer cells are highly diverse and some do not rely heavily on this enzyme for DNA repair, making them unsuitable targets for drugs in this class. Research on these drugs has shown them to be effective for treatment of some breast cancers, including breast cancers without susceptibility to other common drug targets, like human epidermal growth factor receptor 2 (HER-2).
Preliminary studies on parp inhibitor drugs showed promise, leading researchers to express excitement about the potential applications of these medications. The lack of cytotoxicity to healthy cells is a particularly important trait for cancer medications. Many chemotherapy regimens are grueling for patients, and can come with considerable complications and side effects. These can potentially endanger patients, as well as making it harder for patients to comply with prescribed treatments. Medications capable of targeting cancer cells only and leaving healthy cells alone represent a new generation of cancer drugs.
