PARP1-Selective Inhibitors in HRD Tumors — PatSnap Eureka
PARP1-Selective Inhibitors in HRD-Positive Tumors: Isoform Selectivity & Therapeutic Index
Homologous recombination deficiency defines a clinically actionable vulnerability across ovarian, breast, and prostate cancers. This intelligence report maps PARP1-selective chemistry, isoform rationale, combination strategies, and resistance mechanisms from 60+ patent families and academic literature — analyzed by PatSnap Eureka.
Patent Activity by Therapeutic Modality
Distribution of 60+ patent records across PARP inhibitor modalities in this dataset.
Synthetic Lethality in HRD-Positive Tumors: The PARP1 Rationale
Homologous recombination deficiency is the primary therapeutic context for PARP inhibitor development across retrieved results. The canonical synthetic lethality rationale — that tumor cells lacking functional HR repair become entirely dependent on PARP1-mediated base excision repair for survival — is articulated across multiple patent families and academic literature in this dataset.
The genetic landscape of HRD-positive tumors is broad. Multiple TESARO/Janssen filings define HRD-responsive patient populations as those carrying deficiency in at least one gene from a panel including BRCA1, BRCA2, ATM, ATR, BAP1, BARD1, BLM, BRIP1, MRE11A, NBN, PALB2, RAD51 and paralogs RAD51B/C/D, RAD52, RAD54L, XRCC2, TP53, and RB1, with emphasis on non-BRCA HRR gene defects as an expanding biomarker population for niraparib. The PatSnap life sciences platform tracks these evolving biomarker definitions across global patent filings.
At the molecular level, PARP1 (and to a lesser extent PARP2) are the primary therapeutic targets. A Nerviano Medical Sciences patent explicitly frames PARP1-selective inhibition over PARP2 as a medicinal chemistry objective, noting that dual PARP-1/2 knockout is embryonic lethal in mice while PARP-1 single knockout is not — providing a direct mechanistic rationale for isoform selectivity. According to published DNA repair research, PARP trapping at DNA damage sites contributes more cytotoxicity than unrepaired single-strand breaks alone.
A retrieved academic paper from Centre Léon Bérard (2020) summarizes clinical evidence from SOLO-2, NOVA, and ARIEL3 trials demonstrating progression-free survival improvements with olaparib and niraparib as maintenance therapy in platinum-sensitive recurrent ovarian cancer, establishing the clinical framework within which newer PARP1-selective agents are being developed.
Four Distinct Approaches to PARP Inhibition in HRD Tumors
Retrieved patent and literature data reveal four mechanistically distinct therapeutic modalities, from approved pan-PARPi to emerging isoform-selective small molecules and RNAi-based approaches.
Pan-PARP1/2 Small-Molecule Inhibitors
The most densely populated area of retrieved results, covering olaparib, niraparib, rucaparib, talazoparib, veliparib, fluzoparib, and BGB-290 (pamiparib) — referenced across at least 15 distinct patent filings. Mechanism involves catalytic inhibition of PARP NAD+ binding and/or trapping of the PARP1-DNA complex at damage sites. Trapped PARP-DNA complexes are described as more cytotoxic than unrepaired single-strand breaks alone. Assignees include TESARO/GSK, Pfizer, Merck KGaA, and Sierra Oncology.
Phase III clinical evidence: SOLO-2, NOVA, ARIEL3PARP1-Selective Small-Molecule Inhibitors
Nerviano Medical Sciences discloses substituted 3-phenyl-isoquinolin-1(2H)-one derivatives that selectively inhibit PARP1 over PARP2, framing selectivity as a strategy to reduce mechanism-based toxicity. AstraZeneca has separately filed on selective PARP1 inhibitor + ATR inhibitor combinations across ovarian, breast, gastrointestinal, lung, brain, and prostate cancers. KSQ Therapeutics pairs a PARP1-selective inhibitor with a USP1 inhibitor, explicitly noting that PARP1 selectivity may reduce monotherapy toxicity while enabling synergistic tumor killing.
Isoquinolinone scaffold · AstraZeneca 2025 filingsPARP7 & PARP14 Isoform-Selective Agents
Ribon Therapeutics has filed two patent families covering PARP7-selective pyridazinones and PARP14-degrading quinazolinones. Azkarra Therapeutics discloses pyridazin-3(2H)-one and pyridin-2(1H)-one core compounds active against PARP7 and optionally other PARP family members, explicitly noting that multi-PARP inhibitors are expected to have broader cell-killing profiles than PARP7-selective agents. PARP7 is highlighted as relevant to immune evasion and cancer cell survival.
Targeted protein degradation · PARP14 quinazolinonesRNAi-Based PARP Inhibition
The University of Sheffield has filed patents across multiple jurisdictions on the use of RNAi agents that inhibit PARP activity for the treatment of HR-deficient cancers, establishing an RNA-based modality for targeting PARP in addition to small molecules. This approach is at early preclinical stage based on available data. The filing establishes synthetic lethality in base excision repair pathway inhibition selectively lethal to HR-deficient cells as the core mechanism, consistent with small-molecule approaches.
University of Sheffield · Multi-jurisdiction filingPARP Inhibitor Patent Landscape: Key Metrics
Quantitative signals from 60+ patent records and academic literature, analyzed via PatSnap Eureka innovation intelligence.
Top Assignees by Patent Family Count
TESARO/GSK leads with 10+ distinct patent families; Francis Crick Institute holds the broadest academic portfolio with 5 jurisdictional filings on DNPH1.
Combination Strategy Mechanistic Axes
Eight distinct mechanistic axes for PARPi combinations identified across retrieved patent filings, with PARP1+ATR and USP1+PARP1 representing the most active emerging strategies.
Key Targets & Novel Pathway Findings in HRD Oncology
Retrieved results highlight PARP1 as the dominant target, alongside novel sensitization pathways (DNPH1, USP1, ALC1) that expand the HRD therapeutic opportunity.
PARP1 — Catalytic Inhibition & DNA Trapping
The predominant therapeutic target across retrieved results. Patents consistently describe dual roles: catalytic inhibition of DNA repair and physical trapping of PARP1 on DNA damage sites. The Nerviano patent discloses PARP1-selective compounds with measured selectivity over PARP2, grounding the isoform selectivity hypothesis in medicinal chemistry data. The University of Texas System patent identifies PARP1 Tyr907 phosphorylation mediated by c-Met kinase as a resistance biomarker, with combined c-Met + PARP1 inhibition restoring sensitivity in TNBC models. Regeneron's filing extends PARP1-selective inhibition to clonal hematopoiesis of indeterminate potential (CHIP) — a non-solid tumor context.
Tyr907 phosphorylation · c-Met resistance axisDNPH1 — PARPi-Independent Synthetic Lethality
The Francis Crick Institute holds patents across five jurisdictions (KR, BR, MX, SG, CA) demonstrating that HR-deficient cells are sensitized to PARP inhibition by DNPH1 catalytic inhibition or genetic ablation, or by its substrate hmdU (5-hydroxymethyl-deoxyuridine). Critically, combined DNPH1 ablation + hmdU administration can cause synthetic lethality in HR-deficient cells even in the absence of PARPi, defining a novel non-PARP pathway to exploit HRD. The absence of large pharma assignees in these filings represents a potential partnering or acquisition opportunity.
5 jurisdictions · PARPi-independent SL · Academic IPEight Mechanistic Axes for PARP Inhibitor Combinations
Retrieved results reveal a rich combination strategy landscape spanning DDR pathway inhibition, immune checkpoint modulation, and novel sensitization approaches. The most active innovation area combines PARP1 selectivity with orthogonal DDR inhibition and immune modulation.
PARP1-Selective + ATR Inhibitor
AstraZeneca's 2025 BR and KR filings explicitly pair a "selective PARP1 inhibitor" with an ATR kinase inhibitor across ovarian, breast, gastrointestinal, lung, brain, and prostate cancers — the most direct evidence in this dataset for clinical-stage PARP1-selective + DDR combination development. Repair Therapeutics similarly discloses ATR inhibitor + PARPi combinations for cancers with ATM, BRCA2, RNase H2A/B, or CDK12 loss of function.
USP1 Inhibitor + PARP1-Selective Inhibitor
KSQ Therapeutics' filings across multiple jurisdictions propose synergistic tumor killing with reduced PARP1-selective inhibitor monotherapy toxicity, citing decreased dose requirements as a therapeutic index benefit. The combination explicitly leverages PARP1 selectivity to reduce mechanism-based toxicity while enabling synergistic tumor killing — a potential regulatory differentiation strategy.
CHK1 (SRA737) + PARPi
Sierra Oncology holds active patents in JP and MX demonstrating synergistic growth inhibition across multiple PARPi agents — olaparib, niraparib, talazoparib, and rucaparib — with sequential dosing schedules described. This combination targets the replication stress response in HR-deficient tumors, complementing PARP's role in base excision repair.
PARPi + PD-1/PD-L1 Checkpoint Inhibitors
Multiple large pharma filings from TESARO/GSK, Pfizer, and Merck KGaA cover PARPi + anti-PD-1/PD-L1 combinations, with talazoparib + avelumab and niraparib + pembrolizumab among specific pairs described. Stratification by HRD score and PD-L1 tumor proportion score is referenced in Merck KGaA filings, indicating biomarker-driven combination development. According to NCI research, the immunostimulatory effects of DNA damage may synergize with checkpoint blockade.
ALC1 Inhibition + PARPi
Eisbach Bio's 2025 CN filing on ALC1 allosteric inhibitors describes PARP1/2/3 trapping on chromatin as a mechanism to enhance PARPi efficacy, overcome PARPi resistance, and broaden activity to "BRCAness" tumors beyond germline BRCA1/2 deficiency — potentially the most differentiated resistance-reversal strategy in this dataset.
STING Agonist + PARPi + Anti-PD-1
Dana-Farber Cancer Institute's 2023 CN filing addresses PARPi-resistant ovarian tumors with M2-polarized tumor-associated macrophages, proposing STING agonists (MSA-2, ADU-S100) to repolarize macrophages and restore PARPi sensitivity in combination with olaparib + anti-PD-1. This represents a microenvironment-targeting approach to PARPi resistance.
Commercial & Academic IP Positions in PARP1-Selective Inhibitor Research
Patent activity substantially dominates over academic literature in this dataset, with one academic paper identified versus more than 60 patent records across commercial and institutional assignees.
| Assignee | Focus Area | Jurisdictions | Stage Signal |
|---|---|---|---|
| TESARO, Inc. / GSK | Niraparib in HRR-deficient cancers; non-BRCA gene panels; PD-1 combinations; organoid-based selection | BR, KR, CN, TW, AU, SG, WO, CA | Commercially Active |
| Janssen Pharmaceutica N.V. | Niraparib in mCRPC; niraparib + abiraterone/prednisone; biallelic DNA repair defects | BR, JP | Clinical Stage |
| Francis Crick Institute | DNPH1 inhibition as PARPi sensitizer; PARPi-independent synthetic lethality via hmdU | KR, BR, MX, SG, CA | Partnering Opportunity |
| AstraZeneca AB | Selective PARP1 inhibitor + ATR inhibitor combinations; ATRX-deficient brain tumors | BR, KR | Clinical-Stage |
| KSQ Therapeutics | USP1 + PARP1-selective inhibitor combinations; dose-sparing therapeutic index | MX, TW, KR, CN | Preclinical–Early |
Track PARP Inhibitor Assignee Movements in Real Time
PatSnap Eureka monitors new filings, jurisdictional expansions, and ownership changes across all PARP inhibitor IP portfolios. Explore PatSnap IP analytics for competitive intelligence.
From Phase III Trials to Resistance Biomarkers: Clinical Translation Status
Retrieved results contain several explicit clinical translation signals. Phase III maintenance therapy data from SOLO-2, NOVA, and ARIEL3 trials demonstrate PFS benefit for olaparib and niraparib in platinum-sensitive recurrent epithelial ovarian cancer — representing the most direct clinical evidence in this dataset, as reported by Centre Léon Bérard (2020).
In metastatic castration-resistant prostate cancer, Janssen's 2024 BR filing specifies improvement in median radiographic PFS in biallelic DNA repair-defective mCRPC patients treated with niraparib. A separate Janssen JP filing describes niraparib in line 2+ mCRPC patients with prior taxane-based chemotherapy and androgen receptor-targeted therapy, with reference to health-related quality of life endpoints. According to ASCO guidelines, biomarker-selected patient populations are increasingly central to PARPi development strategies.
TESARO's 2026 CN pending filing describes using patient-derived organoids to determine IC50 values and tumor cell viability ratios for PARP inhibitors, and references exosomal DNA-chromatin complexes as response predictors — indicating translational biomarker development linked to clinical decision-making.
No retrieved results reference IND submissions, NDA/BLA filings, or drug approval decisions for PARP1-selective agents specifically. Clinical-stage evidence is restricted to approved pan-PARPi (olaparib, niraparib) and clinical combination programs. The PatSnap life sciences intelligence platform tracks regulatory milestones as they emerge.
PARPi resistance is an established clinical phenomenon. The University of Texas System patent describes preclinical validation of PARP1 pTyr907 as a breast cancer biomarker and outlines its potential as a patient stratification tool. The STING agonist approach from Dana-Farber addresses M2-macrophage-mediated resistance in ovarian tumors, while ALC1 inhibition from Eisbach Bio provides a chromatin-remodeling mechanism to overcome resistance.
IP Strategy & Development Priorities for PARP1-Selective Programs
Key strategic signals derived from patent landscape analysis via PatSnap Eureka. All implications are traceable to retrieved patent and literature records.
PARP1-Selective Chemistry: Active IP Frontier
PARP1-selective chemistry is an active medicinal chemistry frontier with commercial IP coverage by AstraZeneca, Nerviano Medical Sciences, and KSQ Therapeutics in this dataset. Developers should monitor IP positions around PARP1-selective scaffolds — isoquinolinone, azaquinolinone, and pyridazinone-adjacent structures — as differentiated from pan-PARPi nicotinamide/benzimidazole scaffolds, particularly given the therapeutic index rationale of sparing PARP2 to reduce hematological toxicity. Use PatSnap IP analytics to monitor scaffold freedom-to-operate.
Non-BRCA HRR Genes: Next Patient Stratification Frontier
Non-BRCA HRR gene defects — ATM, PALB2, RAD51C/D, BRIP1, CDK12 — represent the next patient stratification frontier. Retrieved patent data from TESARO/Janssen demonstrates these populations are already subject to IP protection for niraparib. Foundation Medicine and Myriad Genetics HRD classification model patents signal that computational genomic stratification tools are being positioned as companion diagnostic assets alongside therapeutic IP.
HRD Gene Panel: From BRCA1/2 to 18+ HRR Genes
Patent filings from TESARO/Janssen show progressive expansion of the HRD biomarker gene panel, reflecting efforts to extend the treatable patient population beyond germline BRCA1/2.
HRR Gene Panel Breadth Across TESARO/Janssen Filings
Expansion from BRCA1/2-only to 18+ HRR gene defects as eligibility criteria for niraparib therapy, as documented across at least 8 distinct patent families.
Jurisdiction Distribution: DNPH1 Patent Portfolio (Francis Crick Institute)
Five-jurisdiction coverage of the DNPH1 sensitization approach represents the most internationally distributed non-commercial academic patent portfolio in this dataset.
PARP1-Selective Inhibitors in HRD Tumors — key questions answered
Dual PARP-1/2 knockout is embryonic lethal in mice while PARP-1 single knockout is not, providing a mechanistic rationale for isoform selectivity. The hypothesis is that PARP2 inhibition contributes to hematological toxicity such as anemia and thrombocytopenia, and that selective PARP1 agents may improve tolerability while retaining antitumor activity in BRCA-deficient settings.
Multiple TESARO/Janssen filings define HRD-responsive patient populations as those carrying deficiency in at least one gene from a panel including BRCA1, BRCA2, ATM, ATR, BAP1, BARD1, BLM, BRIP1, MRE11A, NBN, PALB2, RAD51 and paralogs RAD51B/C/D, RAD52, RAD54L, XRCC2, TP53, and RB1, with emphasis on non-BRCA HRR gene defects as an expanding biomarker population for niraparib.
AstraZeneca's 2025 filings explicitly pair a selective PARP1 inhibitor with an ATR kinase inhibitor across ovarian, breast, gastrointestinal, lung, brain, and prostate cancers. KSQ Therapeutics proposes USP1 inhibitor plus PARP1-selective inhibitor combinations for synergistic tumor killing with reduced monotherapy toxicity. Additional combinations include CHK1 inhibitor plus PARPi (Sierra Oncology), PARPi plus PD-1/PD-L1 checkpoint inhibitors, and ALC1 inhibition plus PARPi.
The University of Texas System patent identifies PARP1 phosphorylation at Tyr907 by c-Met as a resistance mechanism, framing this post-translational modification as a biomarker for stratifying patients who may not respond to PARP1 inhibitors. Additional resistance mechanisms include M2-polarized tumor-associated macrophages in ovarian cancer (addressed by STING agonists), and loss of PARP trapping efficiency addressed by ALC1 allosteric inhibitors.
Phase III trial data from SOLO-2, NOVA, and ARIEL3 demonstrate progression-free survival improvements with olaparib and niraparib as maintenance therapy in platinum-sensitive recurrent ovarian cancer. Janssen's 2024 filing specifies improvement in median radiographic PFS in biallelic DNA repair-defective mCRPC patients treated with niraparib. No retrieved results reference IND submissions, NDA/BLA filings, or drug approval decisions for PARP1-selective agents specifically.
The Francis Crick Institute holds patents demonstrating that HR-deficient cells are sensitized to PARP inhibition by DNPH1 catalytic inhibition or genetic ablation, or by its substrate hmdU (5-hydroxymethyl-deoxyuridine). Combined DNPH1 ablation plus hmdU administration can cause synthetic lethality in HR-deficient cells even in the absence of PARPi, defining a novel non-PARP pathway to exploit HRD.
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References
- Methods for Treating Cancer — TESARO, INC., 2020, BR [Patent]
- Methods of treating cancer — TESARO, INC., 2019, WO [Patent]
- Methods of treating cancer — TESARO, INC., 2019, CA [Patent]
- Prostate cancer treatments with combinations of abiraterone acetate and niraparib — JANSSEN PHARMACEUTICA N.V., 2022, BR [Patent]
- 3-Phenyl-isoquinolin-1(2H)-one derivatives as PARP-1 inhibitors — Nerviano Medical Sciences, 2014, CN [Patent]
- Method of treating diseases with PARP inhibitors — BIPAR SCIENCES, INC., 2012, IL [Patent]
- Use of RNAi inhibiting PARP activity for the manufacture of a medicament for the treatment of cancer — The University of Sheffield, 2015, PL [Patent]
- Overcoming resistance to PARP inhibitor in epithelial ovarian cancer, are we ready? — Centre Léon Bérard, 2020 [Paper]
- Prediction of response to PARP inhibitors and combination therapy targeting c-MET and PARP1 — Board of Regents, The University of Texas System, 2017, CN [Patent]
- Methods of treating clonal hematopoiesis of indeterminate potential (CHIP) with PARP1 inhibitors — Regeneron Pharmaceuticals, 2024, CN [Patent]
- Combination therapy for cancer treatment — ASTRAZENECA AB, 2025, BR [Patent]
- Combination therapy for cancer treatment — AstraZeneca AB, 2025, KR [Patent]
- Therapeutic combinations comprising USP1 inhibitors and PARP1-selective inhibitors — KSQ Therapeutics, 2025, CN [Patent]
- Therapeutic combinations comprising USP1 inhibitors and PARP inhibitors — KSQ THERAPEUTICS, INC., 2022, MX [Patent]
- Pyridazinones as PARP7 inhibitors — RIBON THERAPEUTICS, INC., 2022, AR [Patent]
- Targeted degradation of PARP14 proteins for use in therapy — RIBON THERAPEUTICS, INC., 2024, AR [Patent]
- Pyridazin-3(2H)-one and pyridin-2(1H)-one PARP inhibitor compounds — Azkarra Therapeutics, 2025, CN [Patent]
- PARP trapping and DNA damage repair mechanisms — NCBI/PubMed [Literature]
- National Cancer Institute — Cancer Research Resources [NCI]
- American Society of Clinical Oncology — Clinical Guidelines [ASCO]
- The Francis Crick Institute — Research Programs [Crick]
All data and statistics on this page are sourced from the references above and from PatSnap's proprietary innovation intelligence platform. This report is derived from a limited set of patent and literature records retrieved across targeted searches and represents a snapshot of innovation signals within this dataset only — it should not be interpreted as a comprehensive view of the full field, clinical pipeline, or regulatory landscape.
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