Efficacy and pharmacodynamics of niraparib in BRCA-mutant and wild-type intracranial triple-negative breast cancer murine models

Maria J Sambade; Amanda E D Van Swearingen; Marni B McClure; Allison M Deal; Charlene Santos; Kaiming Sun; Jing Wang; Keith Mikule; Carey K Anders

doi:10.1093/noajnl/vdz005

Efficacy and pharmacodynamics of niraparib in BRCA-mutant and wild-type intracranial triple-negative breast cancer murine models

Neurooncol Adv. 2019 Jun 4;1(1):vdz005. doi: 10.1093/noajnl/vdz005. eCollection 2019 May-Dec.

Authors

Maria J Sambade¹, Amanda E D Van Swearingen¹, Marni B McClure¹, Allison M Deal¹, Charlene Santos¹, Kaiming Sun², Jing Wang², Keith Mikule², Carey K Anders³

Affiliations

¹ Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
² Tesaro, Inc., Durham, North Carolina.
³ Duke Cancer Institute, Duke University Health System, Durham, North Carolina.

Abstract

Background: Despite the poor prognosis of triple-negative breast cancer (TNBC) brain metastases, there are no approved systemic therapies. We explored the DNA-damaging poly(ADP-ribose) polymerase inhibitor (PARPi) niraparib in intracranial mouse models of breast cancer susceptibility protein (BRCA)-mutant TNBC.

Methods: Mice bearing intracranial human-derived TNBC cell lines (SUM149, MDA-MB-231Br, or MDA-MB-436) were treated with niraparib and monitored for survival; intracranial tissues were analyzed for PAR levels and niraparib concentration by mass spectrometry. RNASeq data of primary breast cancers using The Cancer Genome Atlas were analyzed for DNA damage signatures. Combined RAD51 and PARP inhibition in TNBC cell lines was assessed in vitro by colony-forming assays.

Results: Daily niraparib increased median survival and decreased tumor burden in the BRCA-mutant MDA-MB-436 model, but not in the BRCA-mutant SUM149 or BRCA-wild-type MDA-MB-231Br models despite high concentrations in intracranial tumors. RAD51 inhibitor B02 was shown to sensitize all cell lines to PARP inhibition (PARPi). In the analysis of BRCA-mutant primary human TNBCs, gene expression predictors of PARPi sensitivity and DNA repair signatures demonstrate widespread heterogeneity, which may explain the differential response to PARPi. Interestingly, these signatures are significantly correlated to RAD51 expression including PARPi sensitivity (R ² = 0.602, R ²= 0.758).

Conclusions: Niraparib penetrates intracranial tumor tissues in mouse models of TNBC with impressive single-agent efficacy in BRCA-mutant MDA-MB-436. Clinical evaluation of niraparib to treat TNBC brain metastases, an unmet clinical need desperate for improved therapies, is warranted. Further compromising DNA repair through RAD51 inhibition may further augment TNBC's response to PARPi.

Keywords: PARP inhibition; blood–brain barrier; brain metastases; targeted therapy; triple-negative breast cancer.