Kochupurakkal, Bose

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

PURPOSE The multicenter, open-label, randomized phase 2 NCI-9944 study ( NCT02595892 ) demonstrated that addition of ATR inhibitor (ATRi) berzosertib to gemcitabine increased progression-free survival (PFS) compared to gemcitabine alone (hazard ratio [HR]=0.57, one-sided log-rank P = .044, which met the one-sided significance level of 0.1 used for sample size calculation). METHODS We report here the final overall survival (OS) analysis and biomarker correlations (ATM expression by immunohistochemistry, mutational signature 3 and a genomic biomarker of replication stress) along with post-hoc exploratory analyses to adjust for crossover from gemcitabine to gemcitabine/berzosertib. RESULTS At the data cutoff of January 27, 2023 (>30 months of additional follow-up from the primary analysis), median OS was 59.4 weeks with gemcitabine/berzosertib versus 43.0 weeks with gemcitabine alone (HR 0.79, 90% CI 0.52 to 1.2, one-sided log-rank P = .18). An OS benefit with addition of berzosertib to gemcitabine was suggested in patients stratified into the platinum-free interval ≤3 months (N = 26) subgroup (HR, 0.48, 90% CI 0.22 to 1.01, one-sided log-rank P =.04) and in patients with ATM-negative/low (N = 24) tumors (HR, 0.50, 90% CI 0.23 to 1.08, one-sided log-rank P = .06). CONCLUSION The results of this follow-up analysis continue to support the promise of combined gemcitabine/ATRi therapy in platinum resistant ovarian cancer, an active area of investigation with several ongoing clinical trials.

PURPOSE Uterine leiomyosarcoma (uLMS) is an aggressive subtype of soft-tissue sarcoma with frequent metastatic relapse after curative surgery. Chemotherapy provides limited benefit for advanced disease. Multiomics profiling studies have identified homologous recombination deficiency in uLMS. In preclinical studies where olaparib and temozolomide provided modest activity, the combination was highly effective for inhibiting uLMS tumor growth. PATIENTS AND METHODS NCI Protocol 10250 is a single-arm, open-label, multicenter, phase II study evaluating olaparib and temozolomide in advanced uLMS. Patients with progression on ≥1 prior line received temozolomide 75 mg/m2 orally once daily with olaparib 200 mg orally twice a day both on days 1-7 in 21-day cycles. The primary end point was the best objective response rate (ORR) within 6 months. A one-stage binomial design was used. If ≥5 of 22 responded, the treatment would be considered promising (93% power; α = .06). All patients underwent paired biopsies that were evaluated with whole-exome sequencing (WES)/RNAseq and a RAD51 foci formation assay. RESULTS Twenty-two patients were evaluable. The median age was 55 years, and 59% had received three or more prior lines. Best ORR within 6 months was 23% (5 of 22). The overall ORR was 27% (6 of 22). The median progression-free survival (mPFS) was 6.9 months (95% CI, 5.4 months to not estimable). Hematologic toxicity was common (grade 3/4 neutropenia: 75%; thrombocytopenia: 32%) but manageable with dose modification. Five of 16 (31%) of tumors contained a deleterious homologous recombination gene alteration by WES, and 9 of 18 (50%) were homologous recombination-deficient by the RAD51 assay. In an exploratory analysis, mPFS was prolonged for patients with homologous recombination-deficient versus homologous recombination-proficient tumors (11.2 v 5.4 months, P = .05) by RAD51. CONCLUSION Olaparib and temozolomide met the prespecified primary end point and provided meaningful clinical benefit in patients with advanced, pretreated uLMS.

5512 Background: The multicenter, open-label, randomized phase 2 NCI-9944 study (NCT02595892) demonstrated that addition of ATR inhibitor (ATRi) berzosertib to gemcitabine increased progression-free survival (PFS) compared to gemcitabine alone (HR = 0.57, one-sided log-rank p = 0.044, which met the one-sided significance level of 0.1 used for sample size calculation). Final overall survival (OS) and corresponding biomarker analyses are reported here. Methods: Patients (pts) with platinum-resistant high-grade serous ovarian cancer and unlimited previous lines of cytotoxic therapy in the platinum-sensitive setting but no more than one line of cytotoxic therapy in the platinum-resistant setting, were randomized 1:1 to gemcitabine/berzosertib versus gemcitabine alone. Randomization was stratified based on platinum free interval (PFI), PFI≤3 months versus > 3 months. Crossover from gemcitabine to gemcitabine/berzosertib was allowed upon disease progression by RECIST 1.1. OS was a secondary endpoint while preplanned exploratory correlative studies included assessment of DNA repair pathways and replication stress (RS) alterations by targeted gene sequencing and/or immunohistochemistry (IHC). Results: Seventy pts were randomly assigned to treatment with gemcitabine/berzosertib (34 pts) or gemcitabine alone (36 pts); 15 pts crossed over from gemcitabine to gemcitabine/berzosertib. At the final OS analysis (92.9% maturity), median follow-up was 53.2 weeks in the gemcitabine/berzosertib and 43 weeks in the gemcitabine alone groups. Median OS in the intent-to-treat (ITT) population was 59.4 weeks in the gemcitabine/berzosertib group versus 43.0 weeks in the gemcitabine alone group (HR 0.79, 90% CI 0.52-1.2, one-sided p = 0.18). However, when patients who crossed over to gemcitabine/berzosertib were excluded from analysis, a significant OS benefit was observed with gemcitabine/berzosertib (HR 0.60, 90%CI 0.37−0.97); HR was 0.26 (90% CI 0.1−0.7) in pts with PFI≤3 months and 0.89 (90%CI 0.50−1.59) in pts with PFI > 3 months. Furthermore, significant OS benefit was observed in pts with RS-low tumors (HR 0.39, 90%CI 0.17−0.91, defined as tumors harboring no genomic RS alterations related to loss of RB pathway regulation and/or oncogene-induced RS) but not in pts with RS-high tumors (HR 0.74, 90%CI 0.35−1.56). Additional targeted gene sequencing and IHC analyses as well as analyses adjusting for patient crossover will be reported at the meeting. Conclusions: In the ITT population, gemcitabine/berzosertib did not significantly improve OS versus gemcitabine alone. Pts with PFI≤3 months and pts with RS-low tumors may derive a survival advantage from addition of berzosertib to gemcitabine in the platinum-resistant setting. Clinical trial information: NCT02595892 .

11509 Background: uLMS is an aggressive sarcoma subtype of smooth muscle origin. Chemotherapy provides limited benefit for advanced disease. 18-25% of uLMS harbor deleterious alterations in homologous recombination (HR) DNA repair genes. uLMS exhibits high levels of replicative stress. These findings prompted a phase 2 study of O+T in pretreated uLMS where O+T demonstrated activity: ORR 27%, mPFS 6.9 mos (Ingham M. et. al. ASCO 2021: #11506) Methods: NCI protocol #10250 is a single-arm, multicenter, phase 2 trial evaluating O+T in advanced uLMS pts with progression on ≥1 prior line. Pre-treatment (Pre) and on-treatment (On) biopsies were collected from 22 pts. In prespecified analysis, we evaluated for a relationship between clinical outcomes and HR gene alterations by whole exome sequencing (WES), SLFN11/MGMT expression by RNAseq, and RAD51 foci formation (functional assay). HRD scores were calculated from WES using scarHRD. Gene expression was evaluated using a Spearman rank-order correlation analysis to identify genes associated with PFS (p < 0.01) and overexpressed in sensitive (S: PFS > 240d) or resistant (R: PFS < 240d) pts. Gene set enrichment analysis (GSEA) was performed (q = FDR-adjusted p value). Pts with available results: WES/RNAseq (16), Pre HRD score (13), Pre RAD51 foci (12). Results: 31% (5/16) pts had a mutation (Mut) or homozygous deletion (Hd) in the HR panel: ATRX Mut (2), ATR Mut, PALB2 Hd, RAD51B Hd. Pts with PALB2 and RAD51B Hd had longest PFS on study. Recurrent alterations also occurred in TP53 (56%) and RB1 (19%). Median HRD score in Pre samples was 51 (range 36-66) and 10/13 had HRD scores ≥ 42. Pre and On SLFN11 and MGMT RNA expression were not correlated with ORR/PFS. 6/13 Pre samples were HR-deficient by the RAD51 foci assay. Of pts with PFS ≥ 200d, 4/6 were HR-deficient. In Pre samples, 81 genes were overexpressed in S pts and 73 in R pts. In On samples, 146 genes were overexpressed in S pts and 127 in R pts. In On samples, GSEA identified the epithelial-mesenchymal transition enriched in S pts (q = 3.38e-7) and cell cycle pathways (E2F targets, G2M checkpoint) in R pts (q = 7.43e-4). Only 2 genes, CXCL10 and PCDH15, were differentially expressed between paired Pre and On samples (both increased in On). Gene expression signatures for replicative stress showed borderline association with worse PFS. Conclusions: Most uLMS tumors exhibit HR defects as measured by HRD scores. A subset of pts with greater benefit from O+T were identified by WES for HR genes and the RAD51 assay. There was no correlation between SLFN11 and MGMT expression and outcomes. GSEA identified pathways differentially expressed in S and R pts in On samples. O+T induced CXCL10 which has been associated with T-cell trafficking to tumors. A randomized phase 3 trial of O+T versus investigator’s choice is planned. These results provide insight into which pts may benefit most from this novel drug combination. Clinical trial information: NCT03880019.

11506 Background: Uterine leiomyosarcoma (uLMS) is an aggressive sarcoma subtype with frequent metastatic relapse. After failure of front-line chemotherapy, remaining options provide limited benefit (trabectedin: ORR 11%, mPFS 4.0 mos; pazopanib: ORR 11%, median PFS 2.9 mos; dacarbazine: ORR 9%, mPFS 1.5 mos). Recent molecular studies suggest uLMS harbors characteristic defects in the homologous recombination (HR) DNA repair pathway, including somatic biallelic BRCA2 deletion in 10%, implicating potential sensitivity to PARP-inhibitor based treatment approaches. In preclinical uLMS models in which temozolomide (T, an oral equivalent to dacarbazine) or the PARP inhibitor olaparib (O) showed limited single agent activity, the combination of T + O was highly effective in inhibiting uLMS tumor growth and promoting apoptosis. Methods: NCI protocol #10250 is a single-arm, open-label, multi-center phase II study evaluating T + O in advanced uLMS. Pts had progression on ≥ 1 prior line and ECOG PS ≤ 2. Pts received T 75 mg/m2 PO daily + O 200 mg PO BID days 1-7 in 21-day cycles. Primary endpoint was ORR. A one-stage binomial design was used. If ≥ 5/22 responded, the treatment was considered promising (95% power; α = 0.06). All pts underwent paired tumor biopsies. Correlative assays to evaluate for HR deficiency (whole exome sequencing/RNAseq, RAD51 foci formation) and for intrinsic PARP inhibitor resistance (SLFN11 expression) will be correlated with response. Results: 22 patients were evaluable (median age 55, median prior treatment lines 3). Median follow-up was 10.8 mos. Primary endpoint, ORR within 6 mos of initiating treatment, was 23% (5/22). Overall ORR was 27% (6/22). Median PFS was 6.9 mos (95% CI: 5.4 mos – not estimable (NE)). Median duration of response (DOR) was 12.0 mos (95% CI: 9.5 mos – NE). Hematologic toxicity was common (grade 3/4 neutropenia, 77%; thrombocytopenia 32%) but manageable with dose modification. Correlative assays are ongoing with plans to present at the meeting. An immunohistochemical assay for RAD51 foci has been adapted for uLMS samples and clearly distinguishes BRCA2- deleted and wild-type tumors. Conclusions: NCI 10250 met the prespecified primary efficacy endpoint of ORR in a population of patients with heavily pre-treated uLMS. Responses are durable (median DOR 12 mos). Correlative assays are being completed to evaluate whether uLMS tumors with HR deficiency or with preserved SLFN11 expression are most sensitive to T + O and may underlie durable responses. A randomized study of the combination is planned. Clinical trial information: NCT03880019.