ANVISA approved an oral treatment for advanced breast cancer aimed at patients with the ESR1 mutation. The case shows why well-validated biomarkers are increasingly central to the research and development of new treatments.
In 2026, ANVISA approved a new oral drug to treat advanced breast cancer in patients whose tumor carries a specific genetic mutation called ESR1. The news drew attention for the treatment itself, but what it reveals is even more interesting for anyone working in research: how much finding the right biomarker, at the right time, can change the course of a treatment.
Why a tumor stops responding to treatment
Many hormone therapies work well at first but stop working over time. Under the pressure of the treatment itself, some tumor cells can survive carrying a new mutation, a kind of escape route the tumor finds. In breast cancer treated with hormone therapy, that route often runs through the ESR1 gene. Detecting this mutation in time is what makes it possible to change strategy before the disease progresses, and that is exactly what the study behind the new drug's approval, with nearly 900 patients, helped demonstrate.
The role of the biomarker in this story
Simply put, a biomarker is a measurable biological signal that helps answer a clinical or scientific question, in this case, whether a specific tumor will keep responding to a specific treatment. Here, the signal is usually tracked by liquid biopsy, a blood test that detects fragments of the tumor's own DNA circulating in the body, without repeating a tissue biopsy, a less invasive way to follow disease progression in real time.
This kind of signal has been reshaping much of the research and development of new treatments in recent years, and not only in oncology. A well-validated biomarker allows earlier decisions in a project, changing strategy before investing time and resources in something that no longer works, and selecting more precisely who truly benefits from a treatment. That gain, faster decisions, more precise targeting, less trial and error, explains why so much research today is devoted to finding and validating new biomarkers.
Why validating this kind of test is so challenging
The problem is that this signal usually appears in very small amounts, sometimes below 1% of all the genetic material in the blood sample. Detecting something so rare with confidence does not depend only on good equipment, it depends on a fully calibrated process, from sample collection to the criterion that defines what counts as a positive result. A recent study comparing different detection methods showed exactly this: the largest source of error was not the technology used, but the steps before the test itself.
Where preclinical research comes in
This challenge is not exclusive to breast cancer or any specific disease. Whenever a new biomarker is under development, whether for a resistance mutation, a rare variant or an early sign of relapse, the same question arises: how to prove the test is reliable before putting it into use. That is exactly where product validation and preclinical research support come in, designing the right experiment, defining appropriate controls and ensuring the result reflects the sample's biology rather than a method failure. The earlier this step enters the project, the less rework appears down the line, and the lower the risk of an important decision being made on an unreliable result.
This is the kind of reasoning that guides Base Científica's work alongside research and development teams. Talk to us to jointly design and validate your next biomarker.