ATR/PARP1-IN-1 is a dual inhibitor of ATR/PARP1, exhibiting an IC50 of 17.3 nM for ATR and 0.38 nM for PARP1. It effectively reduces cell viability, induces apoptosis, and causes DNA damage. In triple-negative breast cancer (TNBC) models, ATR/PARP1-IN-1 significantly inhibits colony formation, migration, and invasion. Additionally, in MDA-MB-468 xenograft mouse models, it suppresses tumor growth without significant changes in body weight.

PARP1:0.38 nM

ATR/PARP1-IN-1 (Compound B8) demonstrates antiproliferative activity in TNBC cells, with IC50 values of 1.89 μM for MDA-MB-231, 0.32 μM for MDA-MB-468, and 0.009 μM for MDA-MB-436. At concentrations of 0.5-1 μM over 48 hours, it induces G2/M phase cell cycle arrest in MDA-MB-231 and MDA-MB-468 cells, significantly outperforming the combination of Ceralasertib (AZD6738) and Olaparib. It also shows greater pro-apoptotic effects than the combination therapy when tested using Annexin V/PI staining after 72 hours at similar concentrations. Additionally, over 10 days, ATR/PARP1-IN-1 significantly inhibits colony formation, migration, and invasion in these cell lines more effectively than either AZD6738 or Olaparib alone, or their combination. Furthermore, at 1-2 μM for 48 hours, it disrupts epithelial-mesenchymal transition (EMT) in MDA-MB-468 cells and induces notable DNA damage in both MDA-MB-231 and MDA-MB-468 cells. It inhibits CHK1 phosphorylation by ATR in MDA-MB-468 cells at 1-2 μM within 48 hours.

ATR/PARP1-IN-1, administered at a dose of 25-50 mg/kg via intraperitoneal injection twice daily for 28 days, demonstrates significant antitumor efficacy and favorable safety in MDA-MB-468 xenograft mouse models.