Selective PARP1 inhibitors, PARP1-based dual-target inhibitors, PROTAC PARP1 degraders, and prodrugs of PARP1 inhibitors for cancer therapy

Poly ADP-ribose polymerase (PARP) plays a critical role in many cellular processes such as DNA damage repair, gene transcription and cell apoptosis. Therefore, targeting PARP represents a promising strategy for cancer therapy. To date, numerous small molecule PARP1 inhibitors have been identified, but many of them suffer from limited clinical efficacy and serious toxicity. Hence, PARP1 inhibitor-based combination therapies, and other PARP1 modulators (e.g. PROTAC degraders, dual acting agents) have attracted great attention with significant advancements achieved in the past few years. In this review, we overviewed the recent progress on PARP1-based drug discovery with a focus on PARP1 inhibitor-based drug combination therapy and other PARP1-targeting strategies (e.g. selective PARP1 inhibitors, PARP1-based dual-target inhibitors, PROTAC PARP1 degraders, and prodrugs of PARP1 inhibitors). In addition, we also summarized the reported co-crystal structures of PARP1 inhibitors in complex with their target proteins as well as the binding interactions. Finally, the challenges and future directions for PARP-based drug discovery in cancer therapy are also discussed in detail.