Roche clinches FDA OK for two HER2 tests that steer patients to ENHERTU — what investors should watch

Quick take: a practical win for diagnostics that could widen ENHERTU’s reach

Roche (RHHBY) announced FDA approval for two of its HER2 tests as the first diagnostics cleared to identify metastatic breast cancer patients eligible for ENHERTU. The decision formalizes a lab path that treats will actually follow: pathologists can use Roche’s IHC and ISH assays to classify tumors in a way that flags patients for the drug. For Roche this is a commercial win for its diagnostics arm; for the drug makers it lowers a real hurdle to prescribing. Investors should see this as positive for diagnostics revenue and as a modest but tangible booster to ENHERTU’s prescribing footprint — while keeping an eye on uptake and payer decisions that will dictate how big the lift becomes.

What the approvals cover and how the tests will be used in practice

The FDA cleared two specific Roche assays: an immunohistochemistry (IHC) test and a dual in situ hybridization (ISH) test. In plain terms, the IHC test measures how much HER2 protein is on the surface of tumor cells, while the ISH test looks for extra copies of the HER2 gene inside tumor DNA. Together they are intended as companion diagnostics: they give doctors the lab read they need to decide whether ENHERTU is an appropriate choice for a patient with metastatic breast cancer.

The approvals are procedural rather than clinical surprises. They do not change how ENHERTU works or which patients benefit — they simply standardize which laboratory methods count as the official way to identify eligible patients. That matters because different labs have used different platforms and scoring systems; having FDA-cleared, named tests reduces ambiguity for oncologists and payers.

How this could move the needle for Roche’s diagnostics business and for ENHERTU sales

For Roche’s diagnostics division the gain is straightforward. Companion tests drive repeat business: instruments, reagents, and run volumes. When a large drug label explicitly points to a vendor’s test, hospital labs and reference labs are more likely to adopt that platform to avoid equivocal results and billing friction. That often translates into steady reagent demand and incremental instrument placements in major cancer centers.

For ENHERTU’s makers — AstraZeneca (AZN) and Daiichi Sankyo — the approvals remove a practical obstacle to treatment. Clear, FDA‑recognized testing pathways tend to accelerate clinician confidence and can expand the pool of patients who are tested and therefore identified as eligible. The size of that pool depends on tumor biology and testing rates, but thoughtful estimates point to tens of thousands of additional tests annually across major markets, which could translate into a measurable uptick in prescriptions over time.

That said, this is a multiplier rather than a game changer. Diagnostics approvals don’t directly expand the drug’s label or show new clinical benefit; they smooth the path to more consistent use. For investors, expect a slow-burn revenue effect for Roche’s diagnostics and a steady, incremental benefit for ENHERTU sales rather than an overnight surge.

Where this fits in the testing and payer landscape

Roche’s pair of approvals sit against a crowded testing field. Other established players — including Agilent (A) with its Dako portfolio and several large lab networks — already offer HER2 testing solutions. The difference now is regulatory clarity: labs that want to align with the drug label can standardize on Roche’s assays and avoid questions from payers and tumor boards.

Adoption hurdles remain. Many hospitals run in‑house validated assays that clinicians trust. Payers will also decide whether to reimburse testing on Roche platforms at a different rate than established routines. Those decisions will vary by country and by insurer in the U.S. Reimbursement uncertainty and the inertia of lab purchasing cycles mean that uptake will likely be gradual, with big cancer centers and reference labs leading the way.

Investor takeaways: timing, catalysts and risks

Near term, expect three measurable signals. First, Roche may call out incremental test volumes and reagent demand in upcoming diagnostics commentary or quarterly results. Second, ENHERTU prescribers and sales updates from AstraZeneca (AZN) and Daiichi Sankyo could show a lift in regions where Roche platforms are widely used. Third, watch payer announcements and any guideline updates that recommend a specific testing approach — those would accelerate adoption.

Key risks: labs may prefer their existing assays and resist switching platforms, payers may delay or limit reimbursement for branded test kits, and real-world use could diverge from clinical‑trial testing patterns. Analysts should monitor diagnostic reagent sales growth at Roche, ENHERTU prescription trends, and any public statements from large pathology labs about switching or not switching platforms.

Bottom line: this FDA action is a practical, low‑risk win for Roche’s diagnostics business and a helpful enabler for ENHERTU’s manufacturers. It tightens the link between testing and treatment in a way that could steadily boost test volumes and, over time, drug uptake — but the gains will depend on how quickly hospitals, labs and payers adjust their routines.

Sources

• prnewswire.com