Polθ/PARP-IN-1 (compound 25d) is a potent dual inhibitor of DNA polymerase theta (Polθ) and PARP, with IC50 values of 45.6 nM and 5.4 nM, respectively. This compound exhibits antiproliferative activity, induces apoptosis and cell cycle arrest at the G2/M phase, leading to DNA damage, and demonstrates antitumor properties.