PARP Inhibitors

PARP Inhibitors are targeted therapies used to exploit weaknesses in cancer cells that result from defects in genes involved in DNA repair. They are particularly effective in metastatic castration-resistant prostate cancer.

PARP inhibitors are opening new doors in prostate cancer treatment, offering targeted options for men whose tumors harbor specific genetic vulnerabilities. These drugs, Olaparib, Linparza, and Rupacarib (Rubraca), are designed to exploit weaknesses in cancer cells that result
from defects in genes involved in DNA repair, such as BRCA1, BRCA2, ATM, and others within the homologous recombination repair pathway. Here’s how they work.
Under normal circumstances, HRR genes act as the cell’s genetic repair crew, fixing DNA damage and maintaining stability. When these genes are mutated, cancer cells lose a vital part of their repair mechanism. PARP inhibitors block another repair pathway, causing DNA damage to accumulate, ultimately leading to cancer cell death. This double-hit strategy is particularly effective in metastatic castration-resistant prostate cancer, where genetic testing reveals HRR mutations, especially in BRCA2, the most common and responsive mutation in prostate cancer.
Olaparib is an option for men with MCRPC who test positive for HRR mutations. Typically, these drugs are prescribed after patients have tried other therapies, including androgen receptor-targeted drugs or chemotherapy. For BRCA2 mutations, responses to PARP inhibitors are especially strong, while BRCA1 mutations also show promise, albeit less frequently in prostate cancer. The efficacy varies for other HRR mutations, highlighting the importance of precise genetic profiling to identify suitable candidates. Genetic testing, both germline and somatic is pivotal in determining who stands to benefit. Without it, these highly targeted therapies may miss the mark.
For men with identified HRR mutations, PARP inhibitors represent a personalized approach to tackling aggressive, treatment-resistant disease. Looking ahead, researchers are exploring ways to amplify the impact of PARP inhibitors by combining them with other therapies such as androgen receptor inhibitors or additional targeted treatments. Trials are also investigating their potential earlier in the disease process before metastasis occurs. However,
as with many targeted therapies, resistance can develop over time, and scientists are actively studying mechanisms to overcome this challenge and improve durability.