This study aims to evaluate the efficacy of Entinostat combined with Fulvestrant in HR+/HER2- advanced breast cancer patients with recurrence/progression after endocrine therapy (primary endpoint: progression-free survival \[PFS\]), and explore the correlation between peripheral blood mononuclear cell (PBMC) acetylation levels and treatment response to determine the baseline acetylation threshold .
Signed informed consent form.
Female participants aged ≥18 and ≤75 years. 3 .Eastern Cooperative Oncology Group (ECOG) performance status of 0-1
. Hormone receptor positivity is defined by the presence of estrogen receptors (ER), where a threshold of ≥10% positive staining cells is considered indicative of positivity. The status of progesterone receptors (PR) can be either negative or positive, with the same criterion of ≥10% positive staining cells applied to determine receptor positivity.
. HER-2 negativity indicates that the immunohistochemical assessment of the pathological specimen yields a result classified as 0 or 1+. Alternatively, a result classified as 2+ may also be deemed HER-2 negative if corroborated by negative findings from ISH or FISH testing.
Presence of current or prior Central Nervous System (CNS) metastases or leptomeningeal disease (LMD).
Prior treatment with Selective Estrogen Receptor Degraders (SERD, e.g., fulvestrant) or Histone Deacetylase (HDAC) inhibitors (e.g., entinostat, chidamide).
Known to be allergic to SERD, entinostat or other drugs with a benzamide structure (such as tyapride, remopilib, cloprapride, etc.).
Pregnant or lactating women.