Abstract 52: Analytical validation of the Resolution HRD plasma assay used to identify mCRPC patients with mutations, including homozygous deletions, in DNA repair genes as a companion diagnostic for niraparib
Authors: Pollak Julia , Potts Kristy , Chan PuiYee , Tsai Chen-Hsun , Liao Angela , Garrison Carly , Brown Taylor , Stull Paul , Li Zhen , Baker Christine , Garg Kavita , Pekker Ira , Farabaugh Michael , Gormley Michael , Farrington Lesley , Bell Katherine , Singh Usha 
Published: June 2022

Tumor cells of metastatic castration-resistant prostate cancer (mCRPC) patients with homologous recombination deficiency (HRD) are highly sensitive to the blockade of DNA single-strand break repair via the inhibition of the poly(adenosine diphosphate-ribose) polymerase (PARP) family of nuclear proteins. Niraparib is a highly selective PARP inhibitor, with activity against PARP-1/2 DNA-repair polymerases, and the Resolution HRD assay is being developed as a companion diagnostic for niraparib. Detection of HRD in cell free DNA (cfDNA) isolated from blood is minimally invasive and is of special benefit to mCRPC patients, many without accessible lesions. The Resolution HRD assay identifies patients with substitutions, insertions, deletions, and homozygous deletions of the ATM, BRCA1, BRCA2, BRIP1, CDK12 (except homozygous deletions), CHEK2, FANCA, HDAC2, and PALB2 genes by targeted NGS sequencing of cfDNA isolated from plasma. Analytical performance of the Resolution HRD assay was validated using cfDNA from mCRPC patient plasma, cfDNA from healthy donor plasma, and contrived samples with a wide spectrum of technically challenging genetic aberrations along with CRISPR-engineered human cell lines with ATM and BRCA2 gene deletions. The LOD95 was established for substitutions, insertions, deletions, and homozygous deletions for genes represented in the HRD panel with variant types including complex indels, long indels, and challenging genomic settings including homopolymeric and GC-rich regions. mCRPC specimens were used to confirm an acceptable level of precision near 1X LOD and 2-3X LOD concentrations for all 4 variant types. No false-positives were detected in any samples from healthy donors. Resolution HRD has been validated to give consistent results across the 15-30 ng input range. Studies to confirm accuracy of the Resolution HRD test results using a validated orthogonal method will be presented. The Resolution HRD assay offers highly sensitive, specific, and robust test results, and meets analytical requirements for clinical applications. It is intended as a companion diagnostic to niraparib in combination with abiraterone acetate plus prednisone (AAP) for the treatment of mCRPC patients.

Citation Format: Julia Pollak, Kristy Potts, PuiYee Chan, Chen-Hsun Tsai, Angela Liao, Carly Garrison, Taylor Brown, Paul Stull, Zhen Li, Christine Baker, Kavita Garg, Ira Pekker, Michael Farabaugh, Michael Gormley, Lesley Farrington, Katherine Bell, Usha Singh. Analytical validation of the Resolution HRD plasma assay used to identify mCRPC patients with mutations, including homozygous deletions, in DNA repair genes as a companion diagnostic for niraparib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 52.