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Improving PARP inhibitor efficacy in bladder cancer without genetic BRCAness by combination with PLX51107
Jutta Schmitz1,2, Anna L Bartkowiak1,2, Michael Rose2,3,4,5
1Department of Urology, Medical Faculty and University Hospital Duesseldorf, Heinrich-Heine-University Duesseldorf, Germany.
Abstract:
Advanced urothelial carcinoma (UC) requires new therapeutics beyond chemo- and immunotherapies. Clinical trials with PARP inhibitors (PARPi), particularly in Cisplatin-treated UC, yielded limited response. Biomarker-based patient selection (apart from BRCAness) or combination treatment may increase efficacy. To identify the most suitable PARPi for UC, we compared Olaparib with Talazoparib. RNA sequencing of PARPi-treated UC lines revealed few common targets and a different impact on immune response. By analysis of experimental and public clinical data, we identified new UC-specific PARPi response predictors SLFN5, SLFN11, and OAS1. We investigated a new combination treatment using PLX51107, an epigenetic BET protein inhibitor, to increase PARPi efficacy. The Talazoparib + PLX51107 combination had a strong synergistic impact on UC cells and organoids, including Cisplatin-resistant cells, allowing dose reduction to spare benign cells. Mechanisms of synergism targeted homologous recombination repair, DNA replication, and apoptosis regulation. In conclusion, we suggest Talazoparib treatment of UC to be highly efficacious on all models examined when combined with PLX51107. This new combination treatment allows efficient application of PARPi Talazoparib to all UC patients, independent of Cisplatin pretreatment and genetic BRCAness.
Insights
New research suggests combining Talazoparib (a PARP inhibitor) with PLX51107 (a BET inhibitor) shows significant promise for treating advanced urothelial carcinoma (UC). This combination therapy may benefit all UC patients, regardless of prior treatments or genetic mutations.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Advanced urothelial carcinoma (UC) necessitates novel therapeutic strategies beyond conventional chemotherapy and immunotherapy.
- Current poly (ADP-ribose) polymerase inhibitors (PARPi) show limited efficacy in UC, especially in Cisplatin-treated patients, highlighting the need for improved patient selection or combination approaches.
Purpose of the Study:
- To compare the efficacy of Olaparib and Talazoparib in UC models.
- To identify novel biomarkers for PARPi response in UC.
- To investigate the synergistic potential of combining PARPi with the BET inhibitor PLX51107 for enhanced UC treatment.
Main Methods:
- RNA sequencing of UC cell lines treated with PARPi.
- Analysis of experimental and public clinical data to identify response predictors.
- In vitro and organoid studies evaluating the combination of Talazoparib and PLX51107, including in Cisplatin-resistant models.
Main Results:
- Olaparib and Talazoparib exhibited distinct molecular targets and immune response modulation in UC.
- SLFN5, SLFN11, and OAS1 were identified as potential UC-specific PARPi response biomarkers.
- The combination of Talazoparib and PLX51107 demonstrated strong synergy, overcoming Cisplatin resistance and allowing for reduced dosages to minimize toxicity to normal cells.
Conclusions:
- The combination of Talazoparib and PLX51107 is highly efficacious across various UC models.
- This novel therapeutic strategy broadens the applicability of Talazoparib to all UC patients, irrespective of Cisplatin pretreatment or BRCAness status.
- Mechanisms underlying the synergism involve enhanced DNA repair inhibition, DNA replication disruption, and apoptosis induction.
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