PARP1

Overview

Poly(ADP-ribose) polymerase 1 (PARP1) is a nuclear enzyme encoded by the PARP1 gene and classified as a member of the PARP family of proteins. It functions as a central sensor and mediator of DNA damage repair, catalyzing the transfer of ADP-ribose units from nicotinamide adenine dinucleotide (NAD⁺) onto target proteins to form poly(ADP-ribose) (PAR) chains — a post-translational modification that recruits DNA repair machinery to sites of single- and double-strand breaks. Through its zinc-finger DNA-binding domains and catalytic domain, PARP1 is rapidly activated upon detecting DNA lesions, enabling base excision repair and other genomic maintenance pathways. Because PARP1 activity is tightly coupled to adenosine triphosphate consumption and cellular bioenergetics, its inhibition can precipitate profound metabolic and genotoxic stress in cancer cells.

PARP1's clinical relevance is most prominently established in the context of homologous recombination (HR)-deficient cancers. In tumor cells harboring mutations in BRCA1 or BRCA2, the simultaneous loss of HR and PARP1-mediated single-strand break repair creates a state of synthetic lethality, making such tumors exquisitely sensitive to PARP inhibitors (PARPis). This principle underpins the regulatory approval of several PARPis — including olaparib, niraparib, and rucaparib — for cancers including ovarian cancer, breast cancer, and endometrial cancer. Beyond synthetic lethality, PARP1 is implicated in regulating transcription, chromatin remodeling, inflammation, and apoptotic signaling, positioning it as a multifunctional target of broad therapeutic interest.

Focus of Latest Publications

PARP1 inhibition has emerged as a versatile therapeutic strategy across diverse cancer types, including breast, ovarian, endometrial, and cervical cancers, as well as glioblastoma. Recent studies demonstrate evolving approaches to enhance the therapeutic potential of PARP1-targeted agents, ranging from novel chemical modifications and delivery strategies to combination therapies and computational optimization of selectivity.

To overcome intrinsic limitations of PARP inhibitors—including poor bioavailability and inability to cross biological barriers—researchers have developed multiple conjugate and delivery strategies. These include radiolabeling of talazoparib with 211At for targeted alpha-particle radiotherapy, which demonstrated high tumor uptake and therapeutic efficacy in preclinical prostate and glioma models; conjugation of olaparib with a blood-brain barrier-penetrating heptamethine cyanine dye for glioblastoma treatment; attachment of olaparib to platinum-based compounds to enhance specificity and overcome cisplatin resistance in ovarian cancer; and propynylation of the natural product apigeninidin to improve cell membrane permeability and PARP1 targeting in cervical cancer cells.

Complementary therapeutic strategies pairing PARP1 inhibition with DNA-damaging or immunomodulatory agents continue to show promise. The DUO-E trial investigated olaparib combined with durvalumab and chemotherapy in advanced endometrial cancer, demonstrating reduced disease progression and improved survival across mismatch repair proficient and deficient populations. Novel hybrid molecules, such as olaparib-β-carboline compounds, synergistically combine PARP inhibition with DNA damage induction, showing potent anti-proliferative activity against BRCA-deficient triple-negative breast cancer cells and inducing G2/M cell cycle arrest and apoptosis.

Modern drug discovery pipelines employing computational and machine learning approaches are accelerating identification of novel PARP1 inhibitors. Fragment-based design coupled with artificial intelligence-predicted pharmacokinetics and anti-cancer potential identified candidate compounds against triple-negative breast cancer with enhanced stability and synthetic accessibility. Computational methods—including absolute binding free energy calculations and umbrella sampling—have elucidated selectivity determinants between PARP1 and PARP2, revealing how contact connectivity at the binding pocket controls inhibitor selectivity and informing future inhibitor optimization. Additionally, CRISPR-based approaches have identified PARP1 as a synthetic lethal target in BRCA1-deficient tumors, extending the therapeutic rationale for PARP1-targeted precision oncology.