ER+ Breast Cancer: A Promising Strategy
KAT6A/B Inhibition & Menin Codependency in ER+ Breast Cancer: Key Facts
What: Research reveals a synergistic approach to treating endocrine-resistant, estrogen receptor-positive (ER+) breast cancer by simultaneously inhibiting KAT6A/B (histone acetyltransferases) and Menin (a chromatin adaptor protein). This combination overcomes resistance to existing endocrine therapies like SERMs, AIs, and SERDs.
Were: This research spans in vitro studies (cell lines), in vivo studies (patient-derived xenografts – PDX models, and 3D patient-derived organoids – PDxO models) and builds upon understanding of epigenetic mechanisms within breast cancer cells. The clinical progress is centered around pharmaceutical companies like Pfizer (PF-9363) and syndax Pharmaceuticals (SNDX-5613/revumenib).
When: the breakthrough inhibitor PF-9363 has been developed recently, with preclinical data demonstrating efficacy.The identification of Menin as a codependency factor and the synergistic effects of dual inhibition are recent findings (referenced with superscript ‘2’ indicating recent publications). Revumenib (SNDX-5613) is already approved for certain leukemias, paving the way for potential repurposing.
Why it Matters: Endocrine therapy resistance is a major clinical challenge in ER+ breast cancer,the most common subtype. This research offers a novel strategy to address this resistance by targeting epigenetic regulators of ER-driven gene expression. The combination therapy shows promise even in cases where ER signaling persists, suggesting it could benefit a significant patient population. The identification of biomarkers (KAT6A/B amplification/overexpression, Menin expression) could help identify patients most likely to respond.
What’s Next: Clinical trials are needed to evaluate the safety and efficacy of the PF-9363/revumenib combination in patients with endocrine-resistant ER+ breast cancer.Further research will likely focus on:
Identifying predictive biomarkers for response.
Investigating the optimal dosing and sequencing of the two inhibitors.
Exploring the potential for combining this approach with other therapies.
Understanding the mechanisms of resistance that may emerge with this combination.
Key Data & Prevalence:
| Factor | Prevalence in ER+ Breast Cancer | Impact |
|---|---|---|
| KAT6A/B Amplification/Overexpression | 10-15% | Correlates with aggressive tumor behavior & poor prognosis |
| Menin (MEN1) High Expression | >50% | Strongly associated with ER+ subtypes |
Key Compounds:
PF-9363 (CTx-648): A potent, selective, and orally bioavailable KAT6A/B inhibitor (Pfizer).
SNDX-5613 (revumenib, Revuforj): A menin inhibitor (Syndax Pharmaceuticals) – already approved for certain leukemias.
Mechanism of Action (Combined Inhibition):
- Reduced ESR1 Expression: The combination lowers the levels of ERα (ESR1) gene and protein.
- Chromatin Disruption: Displaces KAT6A and Menin-KMT2A from promoters of ER target genes.
- Reduced RNA Polymerase II Binding: Leads to decreased transcription of ER-driven genes and reduced chromatin accessibility.
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