Journal: Journal of clinical oncology : official journal of the American Society of Clinical Oncology
This publication reports the SERENA-3 presurgical window-of-opportunity trial evaluating the oral SERD camizestrant in postmenopausal women with newly diagnosed ER-positive, HER2-negative breast cancer.
Design:
- Open-label, parallel-group trial in 132 patients.
- Camizestrant dosing: given once daily at 75, 150, or 300 mg for 5–7 days, or 75 or 150 mg for 12–15 days prior to surgery.
- Primary pharmacodynamic assessments: ER, PgR, and Ki67 by IHC on pre- and on-treatment tumor samples.
- Exploratory work: transcriptomics, mass spectrometry, and IHC image analysis.
Key findings:
- ER expression reduction: reduced by ~65% across all doses, independent of duration, indicating early and substantial target engagement.
- Ki67 reduction: more pronounced after 12–15 days than after 5–7 days, suggesting a time-dependent antiproliferative effect.
- Exploratory analyses: mass spectrometry and digital IHC were concordant with IHC H-score, confirming comparable, maximal pharmacodynamic effects at all tested doses on ER and Ki67.
- Tolerability of 75 mg dose: very well tolerated; 90–100% of patients on this dose reported no treatment-emergent adverse events across preferred terms. Reported events were almost all grade 1, with a single grade 2 upper respiratory tract infection considered unrelated.
Clinical implications:
- Dosing effect: camizestrant 75 mg once daily achieves maximal ER antagonism/degradation within 5–7 days and maximal measurable Ki67 suppression by 12–15 days.
- Preferred dose: the agent is well tolerated at 75 mg, supporting this as the preferred dose for ongoing Phase III development.
- Trial relevance: the trial illustrates how short presurgical window studies can efficiently inform optimal dose selection for endocrine-targeted therapies.