Cardiff Oncology Data Suggests ADC Combination Could Broaden HER2-Low Breast Cancer Treatment
Event summary
- Cardiff Oncology presented preclinical data at the 2026 AACR Annual Meeting demonstrating antitumor activity of onvansertib combined with trastuzumab deruxtecan (T-DXd).
- The combination showed tumor regression in nearly all mice tested, with complete response rates up to 62% in HER2-low breast cancer models.
- Data suggest the combination overcomes resistance to fulvestrant and CDK4/6 inhibitors.
- Onvansertib is currently in Phase 2 clinical development for RAS-mutated metastatic colorectal cancer.
The big picture
The data highlights a potential shift in ADC treatment strategies, moving beyond targeted therapies to incorporate PLK1 inhibitors to overcome resistance and improve efficacy. This approach could broaden the applicability of ADCs to a wider range of cancers and patient populations, potentially impacting the $30+ billion ADC market. Cardiff Oncology's success here could validate the PLK1 inhibition strategy and open doors for similar combination approaches in other oncology areas.
What we're watching
- Clinical Translation
- The preclinical efficacy observed will need to be replicated in human clinical trials to validate the combination's potential.
- Regulatory Pathway
- Given the existing approvals for both onvansertib and T-DXd, the regulatory pathway for the combination may be accelerated, but will depend on clinical trial results.
- Market Adoption
- The success of this combination will hinge on its ability to address the significant unmet need in HER2-low breast cancer, a growing segment due to the limitations of existing therapies.
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