The Discovery of a Potent PARP1 Inhibitor Senaparib

PARP1 is a critical enzyme involved in DNA damage repair. It belongs to a superfamily of proteins and catalyzes poly(ADP-ribosyl)ation (PARylation). PARP1 inhibitors are effective to treat tumors that have homologous recombination deficiency such as those with BRCA1/2 mutations. The PARP1 inhibitors that have been approved by FDA inhibit both PARP1 and PARP2. PARP2 has also been suggested to play a similar function in DNA repair as PARP1. In addition to inhibiting PARP1 enzymatic activities, PARP1 inhibitors cause the PARP1 enzyme to be "trapped" on DNA, stalling the DNA replication fork and eventually causing double-strand DNA breaks and cell death. Here, we report a PARP1 inhibitor, Senaparib, which has a novel chemical structure and high potency inhibiting PARP1/2 enzymes. Senaparib was highly potent in cell viability tests against tumor cells with BRCA1/2 mutations. It was efficacious in cell line-derived and patient-derived xenograft models in tumors harboring BRCA1/2 mutations. In combination studies, Senaparib used with temozolomide had shown strong synergistic cytotoxicity in both in vitro and in vivo experiments. Senaparib represents a novel class of PARP1 inhibitors that can be used for the treatment of cancer. A phase III clinical study of Senaparib for maintenance treatment following first-line chemotherapy in patients with advanced ovarian cancer has met its primary endpoint, and a new drug application of Senaparib has been accepted by the National Medical Products Administration of China for review.