Studies Towards Hypoxia-Activated Prodrugs of PARP Inhibitors

Area of Science:

• Medicinal Chemistry
• Oncology
• Drug Discovery

Background:

• Poly(ADP-ribose)polymerase (PARP) inhibitors (PARPi) are effective for homologous recombination repair (HRR) deficient tumors.
• PARPi also sensitize HRR competent tumors to chemotherapy/radiotherapy, but normal cell toxicity is a challenge.
• Hypoxia-activated prodrugs (HAPs) offer tumor selectivity by limiting active drug exposure to hypoxic tumor environments.

Purpose of the Study:

• To investigate novel hypoxia-activated prodrugs (HAPs) of PARP inhibitors (PARPi).
• To develop PARPi prodrugs that are selectively activated in hypoxic tumors, minimizing toxicity to normal tissues.
• To identify a viable prodrug strategy for enhancing PARPi therapeutic applications.

Main Methods:

• Design and synthesis of model PARPi hypoxia-activated prodrugs with bioreducible triggers.
• Biochemical assays to evaluate the enzymatic activity of prodrugs and parent PARPi.
• Radiolysis studies to assess prodrug activation and release of the active PARP inhibitor.

Main Results:

• N-alkylated PARPi prodrugs showed abrogated activity but failed to release the active drug upon reduction.
• A 2-nitroimidazolyl ether prodrug of NU1025 demonstrated modest inhibition but efficient release of the active PARP inhibitor upon reduction.
• The potency of the NU1025 prodrug was decreased approximately seven-fold compared to the parent drug.

Conclusions:

• The study identified a promising prodrug strategy for PARP inhibitors using a 2-nitroimidazolyl ether moiety.
• This approach holds potential for developing more targeted cancer therapies by leveraging tumor hypoxia.
• Further exploration of this prodrug strategy is warranted for clinical applications.