A novel strategy involves combining antibody-drug conjugates (ADCs) with PARP inhibitors. This approach could potentially overcome the need for a germline BRCA mutation, significantly broadening the patient population that could benefit from PARP inhibitor therapy in triple-negative breast cancer.

The next innovation for PARP inhibitors will likely involve combinations with other DNA-damaging agents beyond just ARPIs. Promising partners include radioligands like radium (an alpha emitter) and lutetium, or even therapies like superphysiologic testosterone (BAT) that are theorized to work by inducing DNA breaks.

The modest benefit of PARP inhibitors in metastatic breast cancer, compared to ovarian cancer, is likely due to resistance induced by prior exposure to DNA-damaging agents like anthracyclines. This explains the clinical rationale for moving PARP inhibitors to earlier treatment settings, such as neoadjuvant or adjuvant therapy, before resistance develops.

In the absence of direct evidence for adjuvant therapy in high-risk, non-clear cell kidney cancers, clinicians may justify off-label treatment by extrapolating from the drug's known efficacy in the metastatic setting for that specific histology. This highlights the difficult risk-benefit calculations made daily in data-poor clinical scenarios.

The development of PARP-1 selective inhibitors like seriparib signals a shift in drug innovation. Instead of only chasing higher efficacy, these new agents aim for a more favorable toxicity profile (less GI toxicity, fewer dose discontinuations) to improve patient quality of life and treatment adherence.

For high-risk, HR+ patients with germline BRCA mutations, data suggest they derive less benefit from CDK4/6 inhibitors. A practical approach is to give one year of the PARP inhibitor olaparib first, followed by a CDK4/6 inhibitor, capitalizing on the delayed initiation allowance in major trials.

A nuanced approach to PARP inhibitors involves reserving combinations for BRCA2 patients with clear, aggressive clinical features like high-volume disease or liver metastases. This strategy balances potent efficacy against toxicity for a molecularly defined but clinically heterogeneous group, avoiding overtreatment of those with more indolent disease.

In high-risk, BRCA-positive patients eligible for both, clinicians favor giving a PARP inhibitor first. The rationale is based on established survival data, shorter one-year duration, and emerging biological evidence suggesting BRCA2-mutated tumors may be resistant to CDK4/6 inhibitors due to concurrent RB gene loss.

The initial broad enthusiasm for PARP inhibitors in ovarian cancer has been refined. New data confirms a lack of overall survival improvement for patients with HRD-negative (or HR proficient) tumors, pushing clinicians toward a precision medicine approach where these drugs are reserved for patients with BRCA mutations or HRD-positive disease who are most likely to benefit.