Companion diagnostics platforms

Companion diagnostics platforms are tissue-based immunohistochemistry (IHC) and fluorescence in-situ hybridization (FISH) assay systems that determine whether a specific patient’s tumor expresses the biomarker a targeted therapy requires, sold and regulated as a companion diagnostic (CDx) approved alongside a specific drug label. Ventana Medical Systems, operating globally as Roche Tissue Diagnostics, recently received EU IVDR approval for its VENTANA MMR RxDx panel companion diagnostic across multiple cancer types and therapies. Agilent’s Dako PD-L1 IHC 22C3 pharmDx assay — paired with Merck’s Keytruda (pembrolizumab) — has received a string of 2026 FDA approvals expanding its use into esophageal squamous cell carcinoma, triple-negative breast cancer, cervical cancer, gastric/gastroesophageal junction adenocarcinoma and epithelial ovarian/fallopian tube/primary peritoneal carcinoma. Myriad Genetics’ MyChoice CDx received FDA approval as the companion diagnostic for Zejula (niraparib) in ovarian cancer, and the company continues expanding its Precise MRD test to colorectal, renal and breast cancers. In China, 3D Medicines develops companion diagnostics and genomic testing paired with domestic and global oncology drug approvals. In India, MedGenome offers oncology companion-diagnostic and precision-oncology testing including a CNS tumor methylation classifier and its TumourTrack Advance panel.

The key directions of companion diagnostics platforms are:

1. IHC/FISH tissue-based CDx (IHC/FISH Companion Diagnostics): immunohistochemistry and FISH assays run on a tumor tissue biopsy to determine drug eligibility — Ventana/Roche Tissue Diagnostics, Agilent Dako.
2. PD-L1 testing platforms (PD-L1 Testing Platforms): IHC assays specifically quantifying PD-L1 expression to determine checkpoint-inhibitor eligibility across an expanding list of cancer types — Agilent Dako’s 22C3 pharmDx.
3. Hereditary-cancer and biomarker CDx (Hereditary Cancer CDx): germline and homologous-recombination-deficiency testing tied to PARP-inhibitor and other targeted-therapy eligibility — Myriad Genetics.
4. Regional precision-oncology CDx platforms (Tissue-Based Precision Oncology): domestic tissue-based genomic and IHC testing paired with local oncology drug approvals — 3D Medicines, MedGenome.

Sectoral value chain#

[biomarker/assay development] ──> [co-development with drug sponsor] ──> [regulatory approval (paired with drug label)]
                                                    │
                                       (tissue biopsy testing at diagnosis)
                                                    │
                                                    ▼
[label expansion to new indications] <─── [treatment eligibility decision] <─────┘

Value chain levels#

Cross-cutting technologies of the sector:

• Immunohistochemistry (IHC) staining (IHC/FISH Companion Diagnostics): antibody-based staining of tumor tissue sections visualizes protein expression (PD-L1, HER2) directly under a microscope, the workhorse technology of tissue-based CDx.
• PD-L1 quantification scoring (PD-L1 Testing Platforms): standardized scoring systems (Tumor Proportion Score, Combined Positive Score) applied to IHC-stained tissue determine checkpoint-inhibitor eligibility across an expanding list of approved indications.
• Homologous-recombination-deficiency (HRD) testing (Hereditary Cancer CDx): germline and tumor genomic testing identifies patients whose DNA-repair deficiency predicts response to PARP inhibitors and related targeted therapies.

The stack pairs tissue-based IHC/FISH staining and scoring technology with a co-development regulatory pathway that ties the diagnostic directly to a specific drug’s approved label.

1. IHC/FISH assay platforms (IHC/FISH Companion Diagnostics):
   • Ventana’s automated staining platforms and Agilent Dako’s Omnis system run standardized IHC/FISH protocols on tumor tissue sections, the technical foundation every tissue-based CDx builds on.
2. PD-L1 scoring systems (PD-L1 Testing Platforms):
   • Agilent Dako’s 22C3 pharmDx assay applies Tumor Proportion Score and Combined Positive Score scoring to determine checkpoint-inhibitor eligibility, with 2026 approvals expanding the assay across esophageal, breast, cervical, gastric and ovarian cancer indications.
3. Hereditary-cancer and HRD testing (Hereditary Cancer CDx):
   • Myriad Genetics’ MyChoice CDx tests tumor and germline DNA for homologous-recombination deficiency, identifying patients likely to respond to PARP inhibitors such as niraparib.
4. Regional precision-oncology testing (Tissue-Based Precision Oncology):
   • 3D Medicines and MedGenome build domestic tissue-based genomic and IHC testing capacity paired with local oncology drug approvals in China and India respectively.