In brief
A study by the Garvan Institute examined over 400 breast cancer biopsies and found that higher activity of CDK1, a protein involved in cell division, is associated with more aggressive disease and poorer outcomes in estrogen receptor‑positive cancers. The findings, published in Advanced Science, may guide future personalized therapies and highlight the need for larger trials to confirm CDK1 as a biomarker for CDK4/6 inhibitor response.
In Sydney on October 31, 2026, the Garvan Institute of Medical Research announced that the activity of the cell‑division protein CDK1 could help doctors identify estrogen‑receptor positive breast cancers that are likely to respond to the commonly used class of drugs known as CDK4/6 inhibitors.
The study examined more than 400 biopsy samples from patients whose tumors expressed the hormone estrogen receptor, the most common subtype of breast cancer. Researchers found that as the cancer progressed, CDK1 activity rose, and tumors with higher activity were linked to more aggressive disease and worse clinical outcomes. The authors highlighted that CDK1’s predictive value could be used to tailor therapy, enabling patients likely to benefit from CDK4/6 inhibitors to receive them while sparing others who may not respond from the drug’s side effects.
Researchers at Australia's Garvan Institute of Medical Research found that the activity of a protein called CDK1 in breast cancers is linked to how they respond to a common therapy, an insight that could inform more personalized treatment approaches for patients, according to a statement of the institute released on Friday.
The findings were published in the open‑access journal Advanced Science and underscore the potential of biomarkers in oncology. The paper notes that while the correlation between CDK1 activity and tumor aggressiveness was compelling, the study was retrospective and relied on archival tissue. Therefore, the authors call for prospective trials that enroll patients who are receiving CDK4/6 inhibitors to test whether CDK1 can reliably predict response and resistance before treatment decisions are made.
Implications for Personalized Breast‑Cancer Care
Current treatment for estrogen‑receptor positive breast cancer often combines hormonal therapy with CDK4/6 inhibitors to block tumor cell proliferation. However, resistance eventually develops in most patients, and clinicians lack reliable markers to pre‑screen who will benefit. If CDK1 activity proves to be a valid biomarker, molecular testing could become part of the routine workup, allowing clinicians to select the most effective regimen for each individual. Furthermore, because high CDK1 activity signals a biologically aggressive tumor, it may point to patients who need more intensive monitoring or alternative therapeutic strategies.
The researchers also speculate that drugs designed to target CDK1 directly might emerge as a new line of therapy, particularly for tumors that show high CDK1 activity but are refractory to CDK4/6 inhibitors. Such drugs could disrupt an essential step in the cell cycle, potentially overcoming resistance mechanisms that have limited current targeted treatments. Nevertheless, the study authors caution that the transition from discovery to clinical application will require phase II and III trials that incorporate biomarker assessment into study design.
In sum, the Garvan Institute’s work offers a promising avenue toward precision oncology in breast cancer, suggesting that measuring CDK1 activity could become a valuable tool in predicting response to CDK4/6 inhibitor therapy. The next step, as the authors emphasize, will involve larger, prospective studies that directly link CDK1 levels to treatment outcomes and ultimately guide therapeutic decision‑making for patients with estrogen‑receptor positive breast cancer.
