Why Ovarian Cancer Remains a Therapeutic Priority

Approximately 75% of ovarian cancer patients present at advanced stage, and most experience relapse within two years despite initial platinum-based chemotherapy — a grim baseline that explains the density of patent and clinical activity retrieved across this dataset. The disease, particularly high-grade serous ovarian carcinoma (HGSOC), is characterised by high genomic instability, frequent homologous recombination (HR) deficiency, and late-stage diagnosis, making it a natural target for DNA damage response (DDR)-directed therapeutics.

The primary indication driving innovation across retrieved results is epithelial ovarian cancer (EOC), with HGSOC as the dominant subtype. BRCA1 and BRCA2 mutations are the most cited molecular determinants of therapeutic eligibility for PARP inhibitors (PARPi), though — as detailed below — the field has moved well beyond this binary. TROP2 and folate receptor alpha (FRα) are the two antigen targets emerging most prominently in antibody-drug conjugate (ADC) filings, reflecting their established overexpression in ovarian serous tumours relative to normal ovarian epithelium.

Gene expression profiling patents from the University of Arkansas (filed 2005–2006) provided early molecular justification for ADC targeting in ovarian cancer by demonstrating that TROP1 (EpCAM) and TROP2 are among the most highly overexpressed genes in primary ovarian serous papillary carcinomas relative to normal ovarian epithelium. This foundational evidence, now nearly two decades old, is being operationalised in 2024–2025 combination filings by major pharmaceutical companies — a timeline that illustrates the long translational arc from target discovery to combination therapy IP.

PARP Inhibitors: From Monotherapy to Combination Backbone

PARP inhibitor monotherapy and maintenance represents the most heavily patented modality in this dataset, with the mechanistic basis — exploitation of synthetic lethality in HR-deficient tumours through PARP-mediated single-strand break repair inhibition — described across multiple sources spanning 2009 to 2025. The key agents appearing in retrieved filings include olaparib, niraparib, rucaparib, talazoparib, veliparib, and fluzoparib, with niraparib (TESARO/GSK) cited in the largest number of retrieved filings.

Three completed randomised Phase III trials — SOLO-2, NOVA, and ARIEL3 — are explicitly referenced in retrieved academic literature from Centre Léon Bérard and Azienda Ospedaliero-Universitaria di Parma, demonstrating progression-free survival (PFS) improvement with olaparib, niraparib, and rucaparib as maintenance therapy in platinum-sensitive recurrent EOC, with BRCA mutation or HRD status as stratification factors. Retrieved TESARO filing text also cites olaparib Phase II clinical trial preliminary activity data showing 7 responses in 17 BRCA-mutant patients.

“TESARO/GSK filings expand PARP inhibitor eligibility to a panel of at least 20 HR pathway genes beyond BRCA1 and BRCA2 — including ATM, ATR, BAP1, BARD1, BRIP1, PALB2, and multiple RAD51 paralogs — indicating that PARPi utility extends significantly beyond BRCA-mutant populations.”

A critical expansion of patient eligibility is documented in TESARO filings: the gene panel cited for niraparib sensitivity encompasses BRCA1, BRCA2, ATM, ATR, BAP1, BARD1, BLM, BRIP1, MRE11A, NBN, PALB2, RAD51B, RAD51C, RAD51D, RAD52, RAD54L, XRCC2, TP53, and RB1. The Netherlands Cancer Institute — Antoni van Leeuwenhoek Hospital separately addresses HRD assessment via copy number variation (CNV) profiling in ovarian cancer tissue as a patient selection tool, indicating translational emphasis on extending PARPi benefit to HRD-positive, BRCA-wild-type patients. According to WIPO patent data, this type of companion diagnostic co-filing alongside therapeutic claims is a growing feature of oncology IP strategy.

The strategic significance of the PARP inhibitor space is further underscored by the emergence of next-generation selective PARP1 inhibitors. AstraZeneca’s most recent filings (2024–2025) consistently feature AZD5305, a selective PARP1 inhibitor, as the PARPi partner in combination regimens — rather than the first-generation pan-PARP agents. This shift is mechanistically motivated: selective PARP1 inhibition is proposed to reduce hematologic toxicity and allow deeper dosing in combination regimens, a critical consideration when pairing with ADC payloads or kinase inhibitors. Regulatory guidance from bodies such as the European Medicines Agency increasingly emphasises combination toxicity profiling in oncology IND submissions.

ADC Strategies Converging on TROP2 and Folate Receptor Alpha

Antibody-drug conjugate strategies in ovarian cancer are converging on two primary antigen targets — TROP2 and folate receptor alpha (FRα) — with the most recent filings pairing these ADCs with the selective PARP1 inhibitor AZD5305 in a dual-targeting architecture. This represents the most novel combination approach in the entire retrieved dataset, with in vivo xenograft data supporting additive-to-synergistic activity.

TROP2-Directed ADC Combinations

TROP2 (TACSTD2) is a cell-surface glycoprotein whose overexpression in ovarian serous papillary carcinomas relative to normal ovarian epithelium was documented in University of Arkansas gene expression profiling patents as early as 2005–2006. Two AstraZeneca UK Limited filings (Israel jurisdiction, pending 2024) claim an anti-TROP2 ADC conjugated via thioether bond combined with AZD5305 for ovarian, endometrial, and breast cancer, explicitly covering both HR-deficient and HR-proficient tumours — a meaningful expansion of potential patient eligibility beyond the BRCA-mutant population that first-generation PARPi strategies targeted.

Earlier in the ADC+PARPi combination space, ImmunoGen filed a combination claim in Singapore in 2019, and Daiichi Sankyo filed a Chinese patent in 2021 claiming antibody-pyrrolobenzodiazepine (PBD) derivative conjugate combined with PARPi, citing a synthetic lethality-like mechanism validated in BRCA2-knockout xenograft models. These earlier filings establish prior art in the ADC+PARPi space that drug developers must assess for freedom to operate. According to EPO filing data, ADC combination claims have grown substantially as a proportion of oncology patent applications since 2019.

Folate Receptor Alpha — The Emerging Frontier

Folate receptor alpha (FRα, encoded by FOLR1) represents the most nascent combination space in this dataset. A single 2025 AstraZeneca filing (CN, pending) describes AZD5335 — an anti-FRα antibody-containing ADC — combined with AZD5305 (selective PARP1 inhibitor), with in vivo data in OVCAR-3 CDX and CTG3718 PDX ovarian cancer models. This is the first explicit folate receptor alpha ADC combination signal in the retrieved dataset, distinct from legacy folate-targeted small molecule approaches.

High FRα expression in epithelial ovarian cancer makes it a biologically compelling ovarian cancer-specific modality. The pairing with a selective PARP1 inhibitor simultaneously delivers cytotoxic payload to tumour cells via the ADC and inhibits DNA repair via PARP1 — a mechanistic combination with potential synergy in both HR-deficient and HR-proficient tumours, as explicitly stated in retrieved AstraZeneca filing text.

Emerging Combination Architectures: ATR, CHK1, Immune Axes

Beyond ADC pairings, retrieved results reveal a second tier of emerging combination strategies that expand the PARPi backbone into DNA damage response kinase inhibition and immunostimulatory pathways. These represent mechanistically distinct approaches to overcoming or preventing PARPi resistance — a challenge explicitly addressed in retrieved academic literature from Centre Léon Bérard.

DDR Kinase Inhibitor Combinations

Three distinct kinase co-target approaches are documented in retrieved filings. First, AstraZeneca filings across multiple jurisdictions (US, AU, BR) claim selective PARP1 inhibitor plus ATR inhibitor combinations for ovarian cancer. The mechanistic rationale stated in retrieved text is that classical PARPi trap PARP1-DNA complexes and activate ATR-dependent replication stress response pathways; co-inhibition of ATR is expected to produce synergistic DNA damage accumulation. Second, Sierra Oncology filings claim SRA737 (CHK1 inhibitor) combined with PARPi, with described synergistic anti-tumour activity in cancer cell line models including HGSOC. Third, a 2024 Chinese patent from Cadive Oncology Technology claims olaparib combined with onvansertib (PLK1 inhibitor) for ovarian cancer.

These kinase combination strategies reflect a broader industry trend — documented by Nature and other peer-reviewed sources — toward targeting multiple nodes of the DNA damage response simultaneously to overcome intrinsic or acquired resistance mechanisms that limit single-agent PARPi durability.

Immunostimulatory Combinations

Two mechanistically distinct immunotherapy combination directions are documented. A Dana-Farber Cancer Research Institute patent (2023, CN, pending) claims STING agonist co-administration with PARPi to repolarise pro-tumour macrophages toward anti-tumour phenotypes in BRCA-mutant ovarian tumours, framing macrophage polarisation as a mechanism to enhance PARPi efficacy. Separately, Canaria Bio filings (CA 2023; JP 2025) claim oregovomab — a CA-125-targeting monoclonal antibody (mAb-B43.13) — administered sequentially with niraparib for Stage III-IV ovarian cancer, with Phase II trial data (QPT-ORE-002) referenced in retrieved filing text.

The PARPi plus PD-1/PD-L1 checkpoint combination space is covered by multiple Pfizer filings claiming talazoparib plus avelumab, and TESARO filings claiming niraparib plus anti-PD-1 therapy for recurrent ovarian cancer, explicitly addressing BRCA-negative and platinum-resistant patient populations. An Akeso Biopharma filing claims a bispecific anti-PD-1/anti-VEGFA antibody combined with PARPi, with described superior anti-tumour activity over either single agent in in vitro data. AstraZeneca’s 2024 WO filing extends this further to a four-drug combination (chemotherapy plus anti-VEGF plus anti-PD-L1 plus or minus PARPi), with PFS2 analysis figures across non-tBRCAm HRD-positive and ITT patient subgroups referenced in the filing.

Assignee IP Landscape and Strategic Implications

Patent-driven innovation significantly predominates over academic literature in this dataset, indicating a commercially advanced therapeutic area with concentrated IP activity among large pharmaceutical organisations. AstraZeneca holds the most concentrated and recent IP position, with filings spanning selective PARP1 inhibitor combinations with ADCs (TROP2 and FRα) and ATR inhibitors — all filed between 2024 and 2025, indicating active multi-front IP positioning around next-generation PARPi-based regimens.

Key Assignees and Their IP Positions

• AstraZeneca AB / AstraZeneca UK Limited: Most prolific recent filer. Covers ovarian cancer PARPi combinations (olaparib-containing regimens), selective PARP1 inhibitor (AZD5305) combinations with anti-TROP2 and anti-FRα ADCs, and ATR inhibitor combinations. Filing dates 2024–2025 across US, AU, CN, WO, IL jurisdictions.
• TESARO, Inc. (now GlaxoSmithKline): Highest volume of niraparib-specific filings. Covers BRCA-expanded patient selection (20+ HR pathway genes), platinum-resistant indications, and niraparib plus anti-PD-1 combinations across WO, EP, AU, CA, SG, TW jurisdictions.
• Pfizer Inc.: Multiple filings for talazoparib plus avelumab (PD-1 axis antagonist) combinations across WO, CA, IL, TW, BR jurisdictions.
• BiPar Sciences, Inc. (now Sanofi): Foundational early-stage PARPi ovarian cancer method claims filed 2009–2012 across CA, AU, IL, SG, IN. Drug developers entering PARPi monotherapy space must assess these foundational claims.
• ImmunoGen, Inc.: Early ADC plus PARPi combination claim (SG, 2019) at the intersection of these two modalities.
• Daiichi Sankyo (First Sankyo Co., Ltd.): ADC plus PARPi combination claim in China (2021, active) using PBD-based ADC chemistry.
• Canaria Bio Inc.: Oregovomab plus niraparib combination patents in CA (2023) and JP (2025) for Stage III-IV ovarian cancer, with Phase II trial data referenced.

Academic institutions — including Centre Léon Bérard, Azienda Ospedaliero-Universitaria di Parma, Dana-Farber Cancer Research Institute, Netherlands Cancer Institute, University of Arkansas, and General Hospital Corporation — contribute predominantly literature-driven signals or early-stage translational patents focused on biomarkers and patient stratification. These institutions may represent collaborative or licensing opportunities for commercial assignees seeking to de-risk clinical development, particularly as Phase I combination trial data will be needed for ADC plus PARPi regimens. The NIH National Cancer Institute maintains an active funding portfolio in ovarian cancer DDR research that may accelerate academic-to-commercial translation in this space.

“HRD-expansion and non-BRCA patient populations are well-covered by TESARO/GSK IP across a broad gene panel of at least 20 HRR pathway genes; combination strategies and novel ADC targets likely represent lower prior art density areas for new entrants.”

Emerging precision medicine signals in the dataset include organoid-based personalisation of PARPi regimens (Tesano Limited) and machine learning-based prediction of olaparib sensitivity (Zephyr AI), suggesting a precision medicine layer is being built above combination therapy strategies. These signals indicate that future IP competition in ovarian cancer may extend to patient selection algorithms and companion diagnostic tools, not just therapeutic combinations. Drug developers and academic researchers should monitor this layer alongside the therapeutic patent landscape.