PARP inhibitors in gliomas: Mechanisms of action, current trends and future perspectives

Gliomas are the most common primary malignant brain tumours in adults. Despite decades of research into novel therapeutic approaches, the prognosis remains poor. PARP1-2 are critical for DNA repair, cell survival and genomic stability and PARP inhibition (PARPi) may be a promising therapeutic approach for gliomas. Inhibition of PARP activity leads to homologous recombination deficiency (HRD), which, in combination with DNA damage, results in cell death. This review summarises the current knowledge and future perspectives of PARPi in glioma. The available literature was reviewed using PubMed, recent major international oncology congresses were consulted, and ongoing clinical trials were searched using ClinicalTrials.gov. In translational research, PARPi have demonstrated a strong scientific rationale for their use in the treatment of glioma. They have been evaluated both alone and in combination with radiotherapy, temozolomide, anti-angiogenic agents, immunotherapy and other new drugs in newly diagnosed or recurrent glioma. Most studies were open-label, non-randomised, dose-escalation phase I-II trials. Early results show promising anti-tumour activity, and key challenges include identifying predictive biomarkers, elucidating synergistic effects in combination therapies, addressing the development of resistance, and managing hematological toxicity. In conclusion, early phase studies have shown promising anti-tumour activity of PARPi that should be confirmed in larger prospective and randomised trials. In addition, the development of novel PARPi with improved blood brain barrier (BBB) penetration and PARP inhibitor activity with new synergistic treatment combinations seems promising and needs to be further explored.