Biomarkers Associating with PARP Inhibitor Benefit in Prostate Cancer in the TOPARP-B Trial

Abstract

Pròstata; PARP; Biomarcadors

Próstata; PARP; Biomarcadores

Prostate; PARP; biomarkers

PARP inhibitors are approved for treating advanced prostate cancers (APCs) with various defective DNA repair genes; however, further studies to clinically qualify predictive biomarkers are warranted. Herein we analyzed TOPARP-B Phase II clinical trial samples, evaluating whole exome and low-pass whole genome sequencing and immunohistochemical assays evaluating ATM and RAD51 foci (testing homologous recombination repair function). BRCA1/2 germline and somatic pathogenic mutations associated with similar benefit from olaparib; greater benefit was observed with homozygous BRCA deletion. Biallelic, but not mono-allelic, PALB2 deleterious alterations were associated with clinical benefit. In the ATM cohort, loss of ATM protein by immunohistochemistry associated with better outcome. RAD51 foci loss identified tumors with biallelic BRCA and PALB2 alteration while most ATM- and CDK12-altered APCs had higher RAD51 foci levels. Overall, APCs with homozygous BRCA2 deletion are exceptional responders; PALB2 biallelic loss and loss of ATM immunohistochemical expression associated with clinical benefit.

TOPARP is an investigator-initiated trial; we are grateful for the support and funding from AstraZeneca, and for the study grants from Cancer Research UK (CRUK/11/029; C12540/A12829; C12540/A13230; C12540/A20447). ICR-CTSU also receives program grant funding from Cancer Research UK (Grant number: C1491/A15955, C1491/A25351). We acknowledge research funding for this work from Cancer Research UK, Prostate Cancer UK, the Movember Foundation through the London Movember Centre of Excellence (CEO13_2-002), the Prostate Cancer Foundation, and the UK Department of Health through an Experimental Cancer Medicine Centre (ECMC) grant. Professor Johann de Bono is a National Institute for Health Research (NIHR) Senior Investigator. The views expressed in this article are those of the author(s) and not necessarily those of the NHS, the NIHR, or the Department of Health; research at the Royal Marsden Hospital is supported by a Biomedical Research Centre grant. Pasquale Rescigno was supported by a PCF Young Investigator Award 19YOUN19. The authors affiliated to VHIO acknowledge funding from “La Caixa” Foundation and European Institute of Innovation and Technology/Horizon 2020 (LCF/TR/CC19/52470003), Fundacion FERO and Fundacion Cellex. J. Mateo, A. Llop-Guevara and V. Serra received grants from Fundacion Cientifica AECC (LABAE16020PORTT) and an ERAPERMED2019-215. J. Mateo gratefully acknowledges funding from the European Union’s Horizon 2020 research and innovation program (Marie Skłodowska-Curie grant 837900), Instituto de Salud Carlos III (Grant PI18/01384), Fundación AECC, CRIS Cancer Foundation and the US Department of Defense CDMRP (Impact Award PC170510P1). S. Arce-Gallego Research. Downloaded from cancerdiscovery.aacrjournals.org on July 1, 2021. © 2021 American Association for Cancer Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited. Author Manuscript Published OnlineFirst on May 27, 2021; DOI: 10.1158/2159-8290.CD-21-0007 3 and V. Serra were supported by Instituto de Salud Carlos III (FI19/00280, CPII19/00033).