Exploration of tumor genomics associated with prolonged benefit from or resistance to talazoparib monotherapy in patients with metastatic castration-resistant prostate cancer.
Elena Castro, A Douglas Laird, Niven Mehra et al.
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In 30 seconds
This phase II trial analysis explored tumor genomic features associated with duration of benefit from talazoparib monotherapy in pretreated patients with metastatic castration-resistant prostate cancer and HRR gene alterations. In the efficacy population, 15 of 16 patients with radiographic progression-free survival (rPFS) of at least 12 months had tumor BRCA2 alterations, compared with 6 of 27 whose rPFS was under 2 months (p < 0.00001). Retrospective tumor analyses and serial circulating tumor DNA assessments also identified emergent HRR reversion and PARP1 variants in some evaluable patients, potentially associated with resistance.
Key findings
- Tumor BRCA2 alterations were present in 15/16 patients (94%) with rPFS ≥ 12 months versus 6/27 (22%) with rPFS < 2 months (p < 0.00001).
- HRR gene reversion variants predicted to restore gene function were detected in 7/27 patients evaluable at week 25 and/or the safety follow-up visit.
- Emergent PARP1 variants predicted to truncate PARP1 and/or inhibit talazoparib binding were found in 5/27 evaluable patients.
Why it matters
The findings link tumor BRCA2 alterations with prolonged rPFS during talazoparib treatment and identify candidate genomic changes associated with escape from PARP inhibition. These observations add context for interpreting genomic heterogeneity and acquired resistance in HRR-altered metastatic prostate cancer, while remaining exploratory rather than establishing a treatment-selection rule.
What to keep in mind
Genomic analyses were retrospective and conducted in subgroups of the efficacy population; the emergent-variant findings were based on smaller evaluable groups.