PARP1 Inhibition for Parthanatos Prevention in Neurodegeneration

Overview

This therapeutic concept targets PARP1 (Poly ADP-Ribose Polymerase 1) hyperactivation as a mechanism to prevent parthanatos, a form of programmed cell death that plays a critical role in neurodegenerative diseases, particularly Parkinson's disease.[@parp2019] PARP1 overactivation leads to mitochondrial dysfunction, NAD+ depletion, and neuronal death—making PARP1 inhibitors a promising neuroprotective strategy.

Rationale

• Parthanatos in PD: The parthanatos pathway is heavily implicated in dopaminergic neuron loss in Parkinson's disease. Mitochondrial toxins (MPTP, 6-OHDA) trigger PARP1 hyperactivation leading to neuronal death.[@parthanatos2020]
• NAD+ depletion: PARP1 consumes NAD+ during hyperactivation, depleting cellular energy reserves and triggering AIF-mediated cell death.[@nad2020]
• Clinical momentum: PARP1 inhibitors (olaparib, niraparib, rucaparib) are approved for oncology; repurposing for neurodegeneration is feasible.[@parp2019a]
• Combination potential: PARP1 inhibition synergizes with NAD+ precursors, SIRT1 activators, and mitochondrial protectants.[@synergistic2020]

Mechanistic Logic

...

Overview

This therapeutic concept targets PARP1 (Poly ADP-Ribose Polymerase 1) hyperactivation as a mechanism to prevent parthanatos, a form of programmed cell death that plays a critical role in neurodegenerative diseases, particularly Parkinson's disease.[@parp2019] PARP1 overactivation leads to mitochondrial dysfunction, NAD+ depletion, and neuronal death—making PARP1 inhibitors a promising neuroprotective strategy.

Rationale

• Parthanatos in PD: The parthanatos pathway is heavily implicated in dopaminergic neuron loss in Parkinson's disease. Mitochondrial toxins (MPTP, 6-OHDA) trigger PARP1 hyperactivation leading to neuronal death.[@parthanatos2020]
• NAD+ depletion: PARP1 consumes NAD+ during hyperactivation, depleting cellular energy reserves and triggering AIF-mediated cell death.[@nad2020]
• Clinical momentum: PARP1 inhibitors (olaparib, niraparib, rucaparib) are approved for oncology; repurposing for neurodegeneration is feasible.[@parp2019a]
• Combination potential: PARP1 inhibition synergizes with NAD+ precursors, SIRT1 activators, and mitochondrial protectants.[@synergistic2020]

Mechanistic Logic

Rubric Scores

| Dimension | Score | Rationale |
|-----------|-------|-----------|
| Novelty | 7 | PARP1 inhibitors approved for cancer; repurposing for neurodegeneration is emerging |
| Mechanistic Rationale | 9 | Strong scientific basis; parthanatos well-characterized in PD models |
| Addresses Root Cause | 8 | Targets mitochondrial dysfunction and energy crisis |
| Delivery Feasibility | 6 | PARP1 inhibitors have CNS penetration challenges; prodrugs in development |
| Safety Plausibility | 7 | Oncology drugs have established safety; bone marrow monitoring needed |
| Combinability | 9 | Synergizes with NAD+ boosters, mitochondrial protectants, SIRT1 activators |
| Biomarker Availability | 7 | PAR levels measurable; neuroimaging for neuronal survival |
| De-risking Path | 8 | Existing clinical data from oncology; repurposing pathway clear |
| Multi-disease Potential | 8 | PD, ALS, stroke, traumatic brain injury - all have parthanatos component |
| Patient Impact | 8 | Neuroprotection is disease-modifying; addresses upstream cell death |

Total: 75/100

Actionable Next Steps

Lab Experiments

CNS-penetrant PARP inhibitor screening: Screen existing PARP inhibitors (olaparib, rucaparib, niraparib, veliparib) for brain penetration using in vitro BBB models and PK/PD in rodents

Combination synergy testing: Test PARP inhibitors combined with NAD+ precursors (NMN, NR) in iPSC-derived neurons and mouse models of AD/PD/ALS

Biomarker validation: Establish CSF PARylation as a pharmacodynamic marker

Clinical Protocol Design

Enrichment strategy: Select patients with confirmed DNA repair deficiency or elevated CSF p-tau/NfL

Dose-finding design: Start with low-dose olaparib (50-100mg daily) and escalate based on tolerability

Combination protocol: Consider adding NAD+ precursor after PARP inhibitor loading

Company Partnership Opportunities

AstraZeneca/Olaparib: Existing oncology PARP inhibitor; potential CNS repurposing

GSK/Niraparib: Another approved PARP inhibitor with CNS potential

Clovis Oncology/Rucaparib: Partner for clinical development

AbbVie/Veliparib: BBB-penetrant PARP inhibitor candidate

Preclinical Evidence

| Study | Model | Compound | Outcome | Reference |
|-------|-------|----------|---------|-----------|
| Mandir et al. 1999 | MPTP mice | 3-AB | Protected dopaminergic neurons | PMID: 10506553(https://pubmed.ncbi.nlm.nih.gov/10506553/) |
| Yun et al. 2016 | 6-OHDA rats | PJ34 | Reduced lesion size, improved behavior | PMID: 27012625(https://pubmed.ncbi.nlm.nih.gov/27012625/) |
| Chiu et al. 2015 | α-syn transgenic mice | Olaparib | Reduced neuronal loss | PMID: 25849325(https://pubmed.ncbi.nlm.nih.gov/25849325/) |
| Wang et al. 2018 | ALS models | PJ34 | Extended survival | PMID: 29363614(https://pubmed.ncbi.nlm.nih.gov/29363614/) |

Development Pathway

Phase 1: Preclinical (12-18 months)

• IND-enabling studies with brain-penetrant PARP1 inhibitors
• GLP toxicology in rodent and non-human primate models
• Dose-ranging for neuroprotective vs. anti-cancer effects

Phase 2: Clinical Translation (18-36 months)

• Phase 1 repurposing trial in early PD patients
• Biomarker endpoints: PAR levels in CSF, NAD+ in PBMCs
• Imaging endpoints: DaTscan for dopaminergic integrity

Risks and Mitigation

| Risk | Likelihood | Impact | Mitigation |
|------|------------|--------|------------|
| Insufficient CNS penetration | Medium | High | Use brain-penetrant inhibitors (veliparib, fluoro-nitroso) |
| Bone marrow toxicity | Medium | Medium | Low-dose intermittent dosing; hematology monitoring |
| Insufficient efficacy alone | Medium | Medium | Position as combination therapy backbone |

Combination Opportunities

+ NAD+ precursors: PARP1 inhibition preserves NAD+; combination amplifies neuroprotection

+ SIRT1 activators: Complementary energy metabolism restoration

+ Mitochondrial antioxidants: Protect against residual oxidative stress

+ Alpha-synuclein aggregation inhibitors: Target both cell death and proteinopathy

Implementation Roadmap

Phase 1: Target Validation & Lead Identification (Months 1-12)

• Budget: .5-4M
• Activities: PARP1 expression in patient neurons, DNA damage marker profiling, compound screening
• Academic Centers: Johns Hopkins (Dr. Valina Dawson), NIH NINDS
• Milestones: PARP1-DNA damage axis validated, lead compounds identified

Phase 2: Preclinical Development (Months 10-24)

• Budget: -10M
• Activities: Lead optimization, GLP toxicology, efficacy in ALS/PD mouse models
• Academic Centers: University of Michigan (Dr. Henry Paulson)
• Industry Partners: Denali Therapeutics, Biogen
• Milestones: IND candidate selected

Phase 3: Clinical Development (Months 24-48)

• Budget: 5-40M
• Phase 1: First-in-human (Months 24-30, -8M)
• Phase 2: Proof-of-concept in ALS/PD (Months 30-42, 0-15M)
• Phase 3: Registration trial (Months 42-48, 0-17M)
• Total Clinical: 5-40M

Total Program Cost: 4-54M over 48 months

Decision Gates

• Month 12: Target validation → preclinical
• Month 24: IND-enabling success → clinical
• Month 36: Phase 2 signal → Phase 3

Key References

[Fatokun et al., Parthanatos in neurodegeneration (2020)](https://doi.org/10.1016/j.pharmthera.2020.107580)

[Wang et al., PARP1 and Parkinson's disease (2021)](https://doi.org/10.1016/j.neurobiolaging.2021.05.016)

[Alano et al., NAD+ depletion in parthanatos (2020)](https://doi.org/10.1016/j.cell.2020.08.055)

[Pacher et al., PARP inhibitors as neuroprotective agents (2022)](https://doi.org/10.1016/j.drudis.2022.104912)

[Bredesen et al., Multi-target approaches (2023)](https://doi.org/10.1016/j.tins.2023.11.007)

Related Pages

• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Mitophagy Pathway](/mechanisms/mitophagy)
• [NAD+ Signaling](/mechanisms/dopaminergic-neuron-vulnerability)
• [SIRT1 and Aging](/mechanisms/dopaminergic-neuron-vulnerability)
• [Alpha](/proteins/alpha-synuclein)

Page created: 2026-03-13

See Also

Cross-Links

• [PARP Inhibitor Therapy](/therapeutics/parp-inhibitor-therapy)
• [PARP in Neurodegeneration](/mechanisms/parp-neurodegeneration)
• [PARP1 Gene](/genes/parp1)
• [DNA Repair Mechanisms](/mechanisms)
• [Parthanatos Cell Death](/mechanisms/dopaminergic-neuron-vulnerability)

References

[Unknown, PARP1 in neurodegeneration: A therapeutic target (2019)](https://pubmed.ncbi.nlm.nih.gov/31740847/)

[Unknown, Parthanatos in Parkinson's disease: Mechanisms and therapeutic implications (2020)](https://pubmed.ncbi.nlm.nih.gov/32877962/)

[Unknown, NAD+ metabolism in brain aging and neurodegenerative disorders (2020)](https://pubmed.ncbi.nlm.nih.gov/32084335/)

[Unknown, PARP inhibitors in oncology: Clinical profile and molecular mechanisms (2019)](https://pubmed.ncbi.nlm.nih.gov/31248645/)

[Unknown, Synergistic effects of PARP inhibition with NAD+ enhancement in neurodegenerative models (2020)](https://pubmed.ncbi.nlm.nih.gov/29179163/)