“These studies further demonstrate the value of DiviTum TKa as a practical and actionable tool that supports clinicians in making precise and timely treatment decisions. By offering real-time insights into treatment effect and helping identify issues such as drug–drug interactions or resistance, DiviTum TKa are contributing to improved care for patients with metastatic breast cancer,” said Anders Rylander, CEO of Biovica.

“The DiviTum TKA assay is a promising tool for monitoring adherence to CDK4/6 inhibitors and drug-drug interactions in the clinic,” said Mariya Rozenblit, MD Assistant Professor of Medicine (Medical Oncology) Yale School of Medicine.
 
“Our study indicates that the TKa assay provides a dynamic, non-invasive way to monitor response to CDK 4/6 inhibitor-based therapy and, when paired with baseline ctDNA, can help identify patients at risk of early progression,” said Dr. Elena Michaels at MGB Cancer.

In both studies, DiviTum TKa, a blood-based assay measuring thymidine kinase activity (TKa), was used for patients with hormone receptor-positive, HER2-negative metastatic breast cancer (HR+/HER2- mBC) receiving CDK4/6 inhibitor therapy. The results will be presented at the San Antonio Breast Cancer Symposium, SABCS 2025 (December 9-12).

More on the studies:
Monitoring adherence and drug interactions with DiviTum TKa
Researchers from Yale Cancer Center evaluated whether early TKa measurements could identify suboptimal CDK4/6 inhibitor activity caused by medication non-adherence or drug interactions. In this single-institution pilot study of 30 patients:

• 83% achieved TKa suppression (<100 DuA) by Cycle 2 Day 28, correlating with prolonged progression-free survival.
• Persistently elevated TKa levels early in treatment predicted poor outcomes (median PFS 2.5 months).
• In several cases, elevated TKa revealed practical issues such as incorrect dosing or interacting medications, which were corrected to restore suppression.

Linking tumor genomics and TKa response patterns
A multi-center case series from Massachusetts General Hospital Cancer Center and Washington University explored associations between baseline circulating tumor DNA (ctDNA) profiles and early TKa response patterns in 22 patients initiating CDK4/6 inhibitor therapy:

• Three distinct TKa patterns were observed: suppressed, rebound, and unsuppressed. The latter two were associated with inferior outcomes.
• Baseline ctDNA revealed resistance-associated alterations, including AKT/PTEN, TP53, ERBB2, and ESR1 mutations.
• Notable cases demonstrated how integrating ctDNA and TKa may provide complementary insights—ctDNA reveals resistance biology, while TKa reflects real-time treatment effect.