Liu, Ruolin

Abstract Purpose: Inhibitors of the Ataxia telangiectasia and Rad3-related (ATR) protein kinase, a critical component of the DNA damage repair response, have synergistic anti-cancer activity with platinum compounds in preclinical models. We therefore conducted a Phase 2 study of the ATR inhibitor berzosertib+carboplatin vs. docetaxel+carboplatin in metastatic castration-resistant prostate cancer. Patients and Methods: Patients previously treated with at least one androgen receptor pathway inhibitor and taxane underwent mandatory biopsy and were randomized 1:1 to receive Arm A (docetaxel 60 mg/m2+carboplatin AUC4 day 1; or carboplatin AUC5 if not a docetaxel candidate) or Arm B (berzosertib 90 mg/m2 days 2,9+carboplatin AUC5 day 1) every 21 days. The primary endpoint was overall response rate (ORR; ≥50% PSA decline or radiographic response). Results: Of 73 randomized patients, 65 received protocol treatment: 34 on Arm A (26 docetaxel+carboplatin; 8 carboplatin alone) and 31 on Arm B. Thirteen patients (38%) in Arm A and 20 (65%) in Arm B had ≥Grade 3 treatment-related adverse events (TrAEs). ORR was 15% in Arm A (5/34; 5/26[19%] with docetaxel+carboplatin) and 0% in Arm B (0/31). At interim analysis after 65 of planned 130 patients were treated, enrollment was halted due to futility. Homologous recombination repair deficiency status from tissue and blood did not correlate with clinical outcomes, but ATM-deficiency or high levels of phoshpo-KAP1 detected in tissue was associated with clinical benefit across both arms of the trial. Conclusions: Berzosertib+carboplatin demonstrated lower ORR and more frequent ≥grade 3 TrAEs compared to docetaxel+carboplatin in this heavily pre-treated, biomarker-unselected population. NCT03517969

e13003 Background: The emergence of somatic KMT2C mutations has been associated with resistance to various treatments, including chemotherapy and endocrine therapy in patients with estrogen receptor-positive breast cancers. The impact of these mutations in patients treated with poly-ADP ribose polymerase inhibitors (PARPi) and phosphatidylinositol-3-kinase inhibitors (PI3Ki) is unknown. Methods: Circulating tumor DNA (ctDNA) was obtained from plasma and peripheral blood at different time points from 38 patients prior to treatment with the combination of the PARPi olaparib with the alpha-specific PI3Ki alpelisib (NCT01623349). CtDNA was also collected immediately before the first cycle and at the time of disease progression. CtDNA underwent deep targeted sequencing (tumor-normal pairs, 397 genes (2Mb) at 25,000x somatic and 10,000x germline) at the Broad Institute of MIT and Harvard. Variants that were exonic, non-synonymous, and predicted to lead to loss-of-function were considered mutations. Cohorts were stratified according to the presence or absence of the genomic alteration, and progression-free survival was compared with the Kaplan-Meier method and log-rank test. A Cox regression was performed using age, tumor type, germline BRCA1/2 mutation status, performance status, and number of previous lines of treatment as covariates. Results: The KMT2C gene was one of the 3 genes most frequently mutated in our cohort, affecting 5 patients (15%) after the exclusion of those with variants with non-deleterious alterations. The other 2 commonly mutated genes were TP53 (76%) and PIK3CA (15%). In the comparison of patients based on these most common mutations, we identified that patients with somatic KMT2C mutations (n=5) have longer mPFS than those that were wild type (n=28): mPFS 386 vs. 151 days, log-rank p = 0.025. Cox proportional hazards model accounting for age, tumor type, germline BRCA1/2 mutation status, performance status, and number of previous lines revealed a hazard ratio of 0.16; p = 0.007. All somatic KMT2C mutations were proximal to the SET domain critical for methyltransferase activity. Upon progression, the KMT2C-mutated clones were suppressed to below the detection level of mutation calling algorithms. Analysis of the raw files revealed that the clones were suppressed but not eliminated. Conclusions: While the emergence of KMT2C has been reported to be associated with cancer progression and resistance to different therapies, patients with deleterious KMT2C mutations in the ctDNA may benefit from therapy with PARPi and PI3Ki.