Myelodysplastic syndromes (MDS) are a group of bone marrow disorders that can cause low blood cell counts and may progress to acute leukemia. Treatment options for patients with intermediate-to-high-risk MDS are limited, especially for older patients or those who are not suitable for intensive chemotherapy or hypomethylating agents.

Chidamide is an oral histone deacetylase inhibitor that has shown antitumor activity in several hematologic malignancies. This study aims to evaluate the effectiveness and safety of chidamide used alone in patients with intermediate-to-high-risk MDS.

This is a prospective, single-arm, open-label phase II study conducted at a single center. Eligible participants will receive oral chidamide twice weekly and will be followed for treatment response and side effects. The results of this study may help determine whether chidamide could be a potential treatment option for patients with intermediate-to-high-risk MDS who have limited therapeutic choices.

This is a prospective, open-label, single-arm phase II study designed to evaluate the efficacy and safety of chidamide monotherapy in participants with intermediate-to-high-risk myelodysplastic syndromes (MDS) who have limited therapeutic options or are not suitable for intensive chemotherapy or hypomethylating agent therapy.

Eligible participants will receive oral chidamide at an initial dose of 20 mg twice weekly. Each dose consists of four 5-mg tablets taken approximately 30 minutes after meals. Treatment may continue for up to 3 months, with a planned follow-up period of 6 months.

The primary objective is to evaluate the overall response rate (ORR) after chidamide treatment. Treatment response will be assessed according to hematologic response and bone marrow evaluation as specified in the study protocol. Secondary objectives include assessment of safety, tolerability, dose modification, treatment discontinuation, and changes in blood cell counts.

Participants will be followed for treatment response, adverse events, laboratory abnormalities, and overall clinical status for up to 6 months after initiation of study treatment.

Inclusion Criteria:

• Aged 60 years or older at the time of informed consent.
• Diagnosis of myelodysplastic syndromes (MDS) according to the World Health Organization (WHO) classification.
• Intermediate-to-high-risk MDS, defined as at least one of the following:
• International Prognostic Scoring System (IPSS) risk category of Intermediate-2 or High, with bone marrow blasts <15%.
• Revised International Prognostic Scoring System (IPSS-R) risk category of Intermediate, High, or Very High, with bone marrow blasts <15%.
• Intermediate-1 risk MDS with grade 1 to 3 anemia and not suitable for hypomethylating agent therapy.
• Evidence of persistent cytopenia affecting one or more hematopoietic lineages for at least 4 months, unless MDS-associated cytogenetic abnormalities or increased blasts are present.
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2.
• Adequate organ function as assessed by laboratory tests within 7 days before enrollment, including liver, renal, and cardiac function, in the opinion of the investigator.
• Ability to understand and willingness to sign a written informed consent form.

Exclusion Criteria:

• Bone marrow blasts >=15% at screening.
• Prior treatment with chidamide.
• Concurrent diagnosis of acute myeloid leukemia (AML) or other active hematologic malignancy.
• Receipt of intensive chemotherapy, hypomethylating agents, or other investigational agents within 4 weeks before enrollment.
• Uncontrolled active infection or severe concurrent medical condition that, in the investigator's judgment, would interfere with study participation.
• Clinically significant cardiac disease, including uncontrolled arrhythmia or clinically relevant QT interval prolongation.
• Known hypersensitivity to chidamide or any of its excipients.
• Participation in another interventional clinical trial at the time of enrollment.
• Any condition that, in the investigator's judgment, would make the participant unsuitable for participation in this study.