This study is designed to evaluate the safety and efficacy of SPH4336 combined with letrozole in first-line treatment of locally advanced or metastatic breast cancer
Patients who voluntarily participate in the study, completely understand the study, and voluntarily sign the informed consent form (ICF).
Female, ≥ 18 and ≤ 75 years of age at the time of signing the ICF.
ECOG（Eastern Cooperative Oncology Group） performance status 0 or 1.
Life expectancy ≥ 3 months.
Prior treatment with any CDK4/6 （Cyclin dependent kinase）inhibitor.
Inflammatory breast cancer.
Patients unsuitable for endocrine therapy at the investigator's discretion.
History of other malignancies within 5 years prior to the start of study treatment.
Parallel
SPH4336 Tablets 400mg
DrugSPH4336 Tablets ：Orally, 400mg once a day; 28 days/cycle Letrozole tablets ：Orally, 2.5mg once a day; 28 days/cycle
SPH4336 Tablets Placebo
DrugSPH4336 Tablets Placebo：Orally,28 days/cycle Letrozole tablets ：Orally, 2.5mg once a day; 28 days/cycle
response rate (ORR)
tumor response will be evaluated according to the Response Evaluation Criteria Solid Tumors (RECIST) criteria version 1.1.
Progression-free survival (PFS)
from the start date of study treatment to the date of progression disease or death , whichever occurred first.
Cmax
PK (Pharmacokinetics) parameters
Tmax
PK (Pharmacokinetics) parameters
Disease control rate (DCR)
DCR was defined as the percentage of patients who have achieved complete response, partial response and stable disease.
Duration of remission (DOR)
DOR was defined for participants who had an objective response as the time from the first occurrence of a documented unconfirmed response to the date of disease progression per RECIST v1.1 or death from any cause.
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