PARP inhibitors in prostate cancer: practical guidance for busy clinicians

Area of Science:

• Oncology
• Genetics
• Pharmacology

Background:

• Metastatic castration-resistant prostate cancer (mCRPC) management has advanced with biomarker-driven therapies.
• Poly (ADP-ribose) polymerase (PARP) inhibitors rucaparib and olaparib were approved in May 2020 for preselected mCRPC patients.
• These approvals target patients with deleterious BRCA1/BRCA2 mutations or other homologous recombination repair gene mutations.

Purpose of the Study:

• To review the current landscape of PARP inhibitors in prostate cancer treatment.
• To discuss the efficacy and biomarker identification for PARP inhibitor therapy.
• To explore future directions and combinations for PARP inhibitors in mCRPC.

Main Methods:

• Review of clinical trial data and FDA approvals for PARP inhibitors in mCRPC.
• Analysis of genetic mutation prevalence and their association with treatment benefit.
• Evaluation of diagnostic methods for biomarker identification, including tissue and plasma DNA sequencing.

Main Results:

• Olaparib demonstrated an overall survival benefit compared to enzalutamide or abiraterone in patients with mCRPC progressing on these therapies.
• Deleterious BRCA2 alterations show the strongest association with PARP inhibitor benefit, while other gene alterations have less impact or are less frequent.
• Tissue DNA sequencing has limitations, with plasma-based platforms offering higher success rates in identifying predictive mutations in late-stage disease.

Conclusions:

• PARP inhibitors represent a significant advancement in targeted therapy for specific mCRPC patient populations.
• Biomarker testing, preferably via plasma-based sequencing, is crucial for identifying eligible patients, especially after progression on standard therapies.
• Ongoing research is exploring PARP inhibitors in combination with other treatment modalities for broader application in prostate cancer management.