Maloney, Lara

Abstract A key resistance mechanism to platinum-based chemotherapies and PARP inhibitors in BRCA-mutant cancers is the acquisition of BRCA reversion mutations that restore protein function. To estimate the prevalence of BRCA reversion mutations in high-grade ovarian carcinoma (HGOC), we performed targeted next-generation sequencing of circulating cell-free DNA (cfDNA) extracted from pretreatment and postprogression plasma in patients with deleterious germline or somatic BRCA mutations treated with the PARP inhibitor rucaparib. BRCA reversion mutations were identified in pretreatment cfDNA from 18% (2/11) of platinum-refractory and 13% (5/38) of platinum-resistant cancers, compared with 2% (1/48) of platinum-sensitive cancers (P = 0.049). Patients without BRCA reversion mutations detected in pretreatment cfDNA had significantly longer rucaparib progression-free survival than those with reversion mutations (median, 9.0 vs. 1.8 months; HR, 0.12; P < 0.0001). To study acquired resistance, we sequenced 78 postprogression cfDNA, identifying eight additional patients with BRCA reversion mutations not found in pretreatment cfDNA. Significance: BRCA reversion mutations are detected in cfDNA from platinum-resistant or platinum-refractory HGOC and are associated with decreased clinical benefit from rucaparib treatment. Sequencing of cfDNA can detect multiple BRCA reversion mutations, highlighting the ability to capture multiclonal heterogeneity. This article is highlighted in the In This Issue feature, p. 151

Abstract High-grade epithelial ovarian carcinomas containing mutated BRCA1 or BRCA2 (BRCA1/2) homologous recombination (HR) genes are sensitive to platinum-based chemotherapy and PARP inhibitors (PARPi), while restoration of HR function due to secondary mutations in BRCA1/2 has been recognized as an important resistance mechanism. We sequenced core HR pathway genes in 12 pairs of pretreatment and postprogression tumor biopsy samples collected from patients in ARIEL2 Part 1, a phase II study of the PARPi rucaparib as treatment for platinum-sensitive, relapsed ovarian carcinoma. In 6 of 12 pretreatment biopsies, a truncation mutation in BRCA1, RAD51C, or RAD51D was identified. In five of six paired postprogression biopsies, one or more secondary mutations restored the open reading frame. Four distinct secondary mutations and spatial heterogeneity were observed for RAD51C. In vitro complementation assays and a patient-derived xenograft, as well as predictive molecular modeling, confirmed that resistance to rucaparib was associated with secondary mutations. Significance: Analyses of primary and secondary mutations in RAD51C and RAD51D provide evidence for these primary mutations in conferring PARPi sensitivity and secondary mutations as a mechanism of acquired PARPi resistance. PARPi resistance due to secondary mutations underpins the need for early delivery of PARPi therapy and for combination strategies. Cancer Discov; 7(9); 984–98. ©2017 AACR. See related commentary by Domchek, p. 937. See related article by Quigley et al., p. 999. See related article by Goodall et al., p. 1006. This article is highlighted in the In This Issue feature, p. 920

Abstract Background: PARP inhibitors are thought to be effective therapy for cancers with homologous recombination (HR) deficiency, best shown to date in patients (pts) with a germline BRCA (gBRCA) mutation. The Cancer Genome Atlas (TCGA) estimated ∼ 50% of high-grade serous ovarian carcinoma (OC) pts have an HR defect (HRD) due to a BRCA mutation (germline or somatic), other HR gene mutation, or another mechanism, e.g., BRCA1 promoter methylation. A randomized maintenance trial of olaparib in recurrent OC demonstrated a clinical benefit in both gBRCA-mutated and gBRCA-wild-type pts. Currently, the best molecular predictors of PARPi response (other than a BRCA mutation) are not known. Platinum sensitivity, often used as a surrogate predictive indicator for PARPi response, is inadequate. A better technique, such as molecular analysis of tumor tissue, could be a superior method for selection of pts for PARPi therapy. Methods: The rucaparib development plan in OC employs a unique strategy of conducting the key trials in parallel, allowing the Phase 2 (ARIEL2) to complete first so that a molecular HRD signature, associated with sub-groups most likely to benefit, can be prospectively applied to the final analysis of the Phase 3 pivotal trial (ARIEL3). ARIEL2 is an ongoing, single-arm, open-label biomarker study designed to refine the molecular signature associated with a response to rucaparib. Eligible pts (n=180) have relapsed, platinum-sensitive, high-grade OC and measurable disease. All pts undergo a pre-dose biopsy and provide archival tumor tissue. Tumor tissue HR status is assessed using Foundation Medicine's next generation sequencing (NGS) platform and University of Washington's BROCA-HR panel, with the current HRD algorithm developed using in vitro/in vivo and TCGA (and similar) bioinformatic data. The key efficacy analyses to be correlated with tumor HR status are response by RECIST v1.1, GCIG-defined CA-125 response, and PFS. The number of gBRCA pts is limited to maximize non-gBRCA response predictors. Exploratory biomarkers include assessment of tissue NHEJ competency (candidate predictive biomarker) and circulating tumor DNA (candidate efficacy surrogate). The optimized algorithm will then be tested prospectively in ARIEL3 (n=540), an international, randomized (2:1), double-blind, placebo-controlled maintenance trial in platinum-sensitive OC in remission after platinum-based therapy. The primary endpoint of ARIEL3 is PFS in molecularly-defined HRD subgroups as determined by NGS analysis of archival tumor tissue using the optimized algorithm, refined (as required) through ARIEL2.Conclusion: This pair of clinical trials seeks to determine prospectively the appropriate population, among all women with platinum-sensitive OC, who derive a meaningful benefit from PARPi treatment in the maintenance setting. Citation Format: Elizabeth Swisher, Iain McNeish, Robert L. Coleman, James D. Brenton, Scott H. Kaufmann, Andrew Allen, Mitch Raponi, Heidi Giordano, Lara Maloney, Jeffrey Isaacson, Jonathan A. Ledermann. Prospective molecular identification of ovarian cancer patients benefiting from PARP inhibitor (PARPi, rucaparib) maintenance therapy - reaching beyond germline BRCA mutations. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr CT339. doi:10.1158/1538-7445.AM2014-CT339

Purpose To assess the tolerability, pharmacokinetics (PKs), and pharmacodynamics (PDs) of the mitogen-activated protein kinase kinase (MEK) 1/2 inhibitor AZD6244 (ARRY-142886) in patients with advanced cancer. Patients and Methods In part A, patients received escalating doses to determine the maximum-tolerated dose (MTD). In both parts, blood samples were collected to assess PK and PD parameters. In part B, patients were stratified by cancer type (melanoma v other) and randomly assigned to receive the MTD or 50% MTD. Biopsies were collected to determine inhibition of ERK phosphorylation, Ki-67 expression, and BRAF, KRAS, and NRAS mutations. Results Fifty-seven patients were enrolled. MTD in part A was 200 mg bid, but this dose was discontinued in part B because of toxicity. The 50% MTD (100 mg bid) was well tolerated. Rash was the most frequent and dose-limiting toxicity. Most other adverse events were grade 1 or 2. The PKs were less than dose proportional, with a median half-life of approximately 8 hours and inhibition of ERK phosphorylation in peripheral-blood mononuclear cells at all dose levels. Paired tumor biopsies demonstrated reduced ERK phosphorylation (geometric mean, 79%). Five of 20 patients demonstrated ≥ 50% inhibition of Ki-67 expression, and RAF or RAS mutations were detected in 10 of 26 assessable tumor samples. Nine patients had stable disease (SD) for ≥ 5 months, including two patients with SD for 19 (thyroid cancer) and 22 (uveal melanoma plus renal cancer) 28-day cycles. Conclusion AZD6244 was well tolerated with target inhibition demonstrated at the recommended phase II dose. PK analyses supported twice-daily dosing. Prolonged SD was seen in a variety of advanced cancers. Phase II studies are ongoing.