Simon A. Smith

Supplementary Fig 1-9 with legends

Study Representativeness Table

Purpose: ARID1A is frequently mutated in cancer. Motivated by the preclinical synthetic lethality between ARID1A loss and ataxia telangiectasia and Rad3-related (ATR) inhibition, we performed an investigator-initiated phase II study of the ATR inhibitor (ATRi) ceralasertib in ARID1A-deficient solid tumors (NCT03682289). Patients and Methods: This was a phase II, Simon two-stage study with a planned sample size of 29 evaluable patients. Eligible patients had locally advanced or metastatic solid tumors with measurable disease by Response Evaluation Criteria in Solid Tumors 1.1 and radiographic progression at study entry. Patients were required to have ARID1A loss as determined by immunohistochemistry analysis of tumor tissue. Patients received ceralasertib 160 mg twice daily on days 1 to 14 every 28 days. RNA sequencing (RNA-seq) and cyclic immunofluorescence were performed on tumor tissue to identify potential biomarkers of treatment response. Results: The confirmed objective response rate (ORR) was 14% among the 29 efficacy-evaluable patients. All four responses, including three complete responses, occurred in endometrioid endometrial carcinoma or ovarian clear-cell carcinoma, with an ORR of 33% and a median duration of response of 33.7 months in this subset. Including one patient with uterine carcinosarcoma who had stable disease, the ORR was 31% among the 13 patients with gynecologic malignancies. Exploratory RNA-seq analysis of pretreatment archival tumor tissue identified upregulated G2–M checkpoint and DNA double-strand break-sensing pathways in patients who responded. Immune profiling revealed tumor immune microenvironment changes associated with the response to ceralasertib. Conclusions: Ceralasertib monotherapy demonstrated promising antitumor activity in ARID1A-deficient gynecologic malignancies. Tumor molecular and immune correlates may inform the further development of ATRis in this patient population.

Representativeness of Study Participants

Purpose:Addition of ataxia telangiectasia and Rad3-related kinase inhibitors (ATRi) to PARP inhibitors (PARPi) overcomes PARPi resistance in high-grade serous ovarian cancer (HGSOC) cell and mouse models. We present the results of an investigator-initiated study of combination PARPi (olaparib) and ATRi (ceralasertib) in patients with acquired PARPi-resistant HGSOC.Patients and Methods:Eligible patients had recurrent, platinum-sensitive BRCA1/2 mutated or homologous recombination (HR)–deficient (HRD) HGSOC and clinically benefited from PARPi (response by imaging/CA-125 or duration of maintenance therapy; > 12 months first-line or > 6 months ≥ second-line) before progression. No intervening chemotherapy was permitted. Patients received olaparib 300 mg twice daily and ceralasertib 160 mg daily on days 1 to 7 of a 28-day cycle. Primary objectives were safety and objective response rate (ORR).Results:Thirteen patients enrolled were evaluable for safety and 12 for efficacy; 62% (n = 8) had germline BRCA1/2 mutations, 23% (n = 3) somatic BRCA1/2 mutations, and 15% (n = 2) tumors with positive HRD assay. Prior PARPi indication was treatment for recurrence (54%, n = 7), second-line maintenance (38%, n = 5) and first-line treatment with carboplatin/paclitaxel (8%, n = 1). There were 6 partial responses yielding an ORR of 50% (95% confidence interval, 0.15–0.72). Median treatment duration was 8 cycles (range 4–23+). Grade (G) 3/4 toxicities were 38% (n = 5); 15% (n = 2) G3 anemia, 23% (n = 3) G3 thrombocytopenia, 8% (n = 1) G4 neutropenia. Four patients required dose reductions. No patient discontinued treatment due to toxicity.Conclusions:Combination olaparib and ceralasertib is tolerable and shows activity in HR-deficient platinum-sensitive recurrent HGSOC that benefited and then progressed with PARPi as the penultimate regimen. These data suggest that ceralasertib resensitizes PARPi-resistant HGSOCs to olaparib, warranting further investigation.